WO2016118791A1 - Dnv magnetic field detector - Google Patents
Dnv magnetic field detector Download PDFInfo
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- WO2016118791A1 WO2016118791A1 PCT/US2016/014403 US2016014403W WO2016118791A1 WO 2016118791 A1 WO2016118791 A1 WO 2016118791A1 US 2016014403 W US2016014403 W US 2016014403W WO 2016118791 A1 WO2016118791 A1 WO 2016118791A1
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- magnetic field
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- diamond
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
Definitions
- the present disclosure generally relates to magnetometers.
- NV nitrogen-vacancy
- DNV Nitrogen vacancy diamond
- FIG. 1 illustrates one orientation of an NV center in a diamond lattice.
- FIG. 1 illustrates one orientation of an NV center in a diamond lattice.
- FIG. 2 is an energy level diagram showing energy levels of spin states for the NV center.
- FIG. 3 is a schematic illustrating an NV center magnetic sensor system.
- FIG. 4 is a graph illustrating a fluorescence as a function of an applied RF frequency of an NV center along a given direction for a zero magnetic field.
- FIG. 5 is a graph illustrating the fluorescence as a function of an applied RF frequency for four different NV center orientations for a non-zero magnetic field.
- FIG. 6 is a schematic diagram illustrating a magnetic field detection system according to an embodiment of the present invention.
- FIG. 7 is a graph illustrating a fluorescence as a function of an applied RF frequency for an NV center orientation in a non-zero magnetic field and a gradient of the fluorescence as a function of the applied RF frequency.
- FIG. 8 is an energy level diagram showing a hyperfine structure of spin states for the NV center.
- FIG. 9 is a graph illustrating a fluorescence as a function of an applied RF frequency for an NV center orientation in a non-zero magnetic field with hyperfine detection and a gradient of the fluorescence as a function of the applied RF frequency.
- FIG. 10 is an overview of a reflector with a diamond having nitrogen vacancies.
- FIG. 11 is a side view of an ellipsoidal reflector with a diamond having nitrogen vacancies and a photo detector.
- FIG. 12 is a side view of an ellipsoidal diamond having nitrogen vacancies and a photo detector.
- FIG. 13 is a side view of a parabolic reflector with a diamond having nitrogen vacancies and a photo detector.
- FIG. 14 is a side view of a parabolic diamond having nitrogen vacancies and a photo detector.
- FIG. 15 is a side view of a parabolic reflector with a flat diamond having nitrogen vacancies inserted parallel to a major axis of the parabolic reflector and a photo detector.
- FIG. 16 is a side view of a parabolic reflector with a flat diamond having nitrogen vacancies inserted parallel to a minor axis of the parabolic reflector and a photo detector.
- FIG. 17 is a side view of a sensor assembly with a parabolic diamond having nitrogen vacancies and a photo detector.
- FIG. 18 is a side view of a sensor assembly with a waveguide provided within a parabolic reflector.
- FIG. 19 is a process diagram for a method for constructing a DNV sensor.
- FIG. 20 is another process diagram for a method for constructing a DNV sensor.
- FIG. 21 is a block diagram depicting a general architecture for a computer system that may be employed to implement various elements of the systems and methods described and illustrated herein.
- FIG. 22 is a schematic illustrating a position sensor system according to one embodiment.
- FIG. 23 is a schematic illustrating a position sensor system including a rotary position encoder.
- FIG. 24 is a schematic illustrating a top down view of a rotary position encoder.
- FIG. 25 is a schematic illustrating a position sensor system including a linear position encoder.
- FIG. 26 is a schematic illustrating a magnetic element arrangement of a position encoder according to one embodiment.
- FIG. 27 is a schematic illustrating a magnetic element arrangement of a position encoder according to another embodiment.
- FIG. 28 is a schematic illustrating a magnetic element arrangement of a position encoder according to another embodiment.
- FIG. 29 is a schematic illustrating the relationship of a position sensor head and the magnetic elements of a position encoder.
- FIG. 30 is a graph of measured magnetic field intensity attributable to magnetic elements of a position encoder for a first magnetic field sensor and a second magnetic field sensor of a position sensor head.
- FIG. 31 is a flow chart illustrating the process of determining a position utilizing a position sensor system according to one embodiment.
- FIGs. 32A and 32B are graphs illustrating the frequency response of a DNV sensor in accordance with an illustrative embodiment.
- FIGs. 33A is a diagram of NV center spin states in accordance with an illustrative embodiment.
- FIG. 33B is a graph illustrating the frequency response of a DNV sensor in response to a changed magnetic field in accordance with an illustrative embodiment.
- FIG. 34 is a block diagram of a magnetic communication system in accordance with an illustrative embodiment.
- FIGs. 35 A and 35B show the strength of a magnetic field versus frequency in accordance with an illustrative embodiment.
- FIG. 36 is a block diagram of a computing device in accordance with an illustrative embodiment.
- FIG. 37 is graphs illustrating the fluorescence as a function of applied RF frequency of four different NV center orientations for a magnetic field applied in opposite directions to the NV center diamond material.
- FIG. 38 is a graph illustrating the fluorescence intensity as a function of time for a NV center diamond material with a pulsed RF excitation.
- FIG. 39 is a graph illustrating the fluorescence as a function of applied RF frequency of four different NV center orientations for a magnetic field applied in opposite directions to the NV center diamond material, with a Lorentzian pair being identified in the graph.
- FIG. 40 is a graph illustrating the fluorescence intensity as a function of time for a NV center diamond material for a pulse of RF excitation.
- FIG. 41 is a graph illustrating the normalized fluorescence intensity as a function of time for a pair of Lorentzian peaks of a NV center diamond material.
- FIG. 42 is a graph illustrating the time to 60% of the equilibrium fluorescence as a function of RF frequency for a negative and positive magnetic bias field applied to a NV center diamond material.
- FIGs. 43 A and 43B are diagrams illustrating hydrophone systems in accordance with illustrative embodiments.
- FIG. 44 illustrates a low altitude flying object in accordance with some illustrative implementations.
- FIG. 45A illustrates a ratio of signal strength of two magnetic sensors, A and B, attached to wings of the UAS as a function of distance, x, from a center line of a power in accordance with some illustrative implementations.
- FIG. 45B illustrates a composite magnetic field (B-filed) in accordance with some illustrative implementations.
- FIG. 46 illustrates a high-level block diagram of an example UAS navigation system in accordance with some illustrative implementations.
- FIG. 47 illustrates an example of a power line infrastructure.
- FIGs. 48A and 48B illustrate examples of magnetic field distribution for overhead power lines and underground power cables.
- FIG. 49 illustrates examples of magnetic field strength of power lines as a function of distance from the centerline.
- FIG. 50 illustrates an example of a UAS equipped with DNV sensors in accordance with some illustrative implementations.
- FIG. 51 illustrates a plot of a measured differential magnetic field sensed by the DNV sensors when in close proximity of the power lines in accordance with some illustrative implementations.
- FIG. 52 illustrates an example of a measured magnetic field distribution for normal power lines and power lines with anomalies according to some implementations.
- FIG. 53 is a depiction of the energy levels of an NV center which contribute to the Hamiltonian thereof.
- FIG. 54 is a graph illustrating fluorescence as a function of applied RF frequency of an NV center for a zero external magnetic bias field.
- FIG. 55 is a graph illustrating fluorescence as a function of applied RF frequency of a high quality NV center sample for an applied external magnetic bias field.
- FIG. 56 is a graph illustrating fluorescence as a function of applied RF frequency of a low quality NV center sample for an applied external magnetic bias field.
- FIG. 57 is a signal flow block diagram of an open loop processing of the total incident magnetic field on the NV center magnetic sensor system.
- FIG. 58 is a signal flow block diagram of a closed loop processing of the total incident magnetic field on the NV center magnetic sensor system.
- FIG. 59 is a flowchart showing a method of the closed loop processing of FIG. 58.
- FIG. 60 is a schematic diagram illustrating a magnetic field detection system according to an embodiment of the present invention.
- FIG. 61 is a schematic illustrating a Ramsey sequence of optical excitation pulses and RF excitation pulses according to an operation of the system of FIG. 60.
- FIG. 62A is a free induction decay curve where a free precession time ⁇ is varied using the Ramsey sequence of FIG. 61.
- FIG. 62B is a magnetometry curve where a RF detuning frequency ⁇ is varied using the Ramsey sequence of FIG. 61.
- FIG. 63 A is a free induction decay surface plot where both the free precession time ⁇ and the RF detuning frequency ⁇ are varied using the Ramsey sequence of FIG.61.
- FIG. 63B is a plot showing a gradient of the free induction decay surface plot of FIG. 63B.
- FIG. 64 is a schematic illustrating a Rabi sequence of optical excitation pulses and RF pulses according to an operation of the system of FIG. 60.
- FIG. 65 is a comparison of graphs showing resonant Rabi frequencies according to a power of RF excitation applied to the system of FIG. 60.
- FIG. 66 is a graph showing raw pulse data collected during an operation of the system of FIG. 60.
- FIG. 67 is a schematic illustrating a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- FIG. 68 is a schematic illustrating a cross section of a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- FIGS. 69A and 69B are schematics illustrating a coil assembly in accordance with some illustrative implementations.
- FIG. 70 is a cross section illustrating a coil assembly in accordance with some illustrative implementations.
- FIG. 71 is a schematic illustrating a side element of a coil assembly in accordance with some illustrative implementations.
- FIG. 72 is a schematic illustrating a top or bottom element of a coil assembly in accordance with some illustrative implementations.
- FIG. 73 is a schematic illustrating a center mounting block of a coil assembly in accordance with some illustrative implementations.
- FIG. 74 is a cross section illustrating of a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- FIG. 75 is a schematic illustrating a coil assembly in accordance with some illustrative implementations.
- FIG. 76 is a schematic illustrating a cross section of a coil assembly in accordance with some illustrative implementations.
- FIG. 77 is a schematic illustrating a side element of a coil assembly in accordance with some illustrative implementations.
- FIG. 78 is a schematic illustrating a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- FIG. 79 is a schematic illustrating a cross section of a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- FIG. 80 is a schematic illustrating a cross section of a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- FIG. 81 is a schematic illustrating a coil assembly in accordance with some illustrative implementations.
- FIG. 82 is a schematic illustrating a cross section of a coil assembly in accordance with some illustrative implementations.
- FIG. 83 is a schematic illustrating a side element of a coil assembly in accordance with some illustrative implementations.
- FIGs. 84A and 84B are schematics illustrating top and bottom elements of a coil assembly in accordance with some illustrative implementations.
- FIG. 85 illustrates a geomagnetic noise model compared with empirical noise data.
- FIG. 86 is a graph illustrating a signal of interest due to a distortion in the magnetic field in the Z-direction as measured by a single magnetic sensor.
- FIGs. 87A-87C are graphs illustrating the signal of interest due to a distortion in the magnetic field in the Z-direction as measured by a two-dimensional magnetic sensor array for times of 1100, 1115 and 1120 seconds, respectively.
- FIG. 88 is a schematic illustrating a magnetic sensor array system according to an embodiment of the invention.
- FIGs. 89A and 89B respectively illustrate a common coordinate system and a coordinate system corresponding to one of the magnetic sensors of the array.
- FIG. 90 is a schematic illustrates an orientation sensor attached to a magnetic field sensor according to an embodiment of the invention.
- FIGs. 91A-91C are graphs illustrating a magnetic field measurement component along the X-direction, Y-direction and Z-direction, respectively, at a time of 500 seconds for a two-dimensional array of magnetic field sensors in the case of a single unmanned underwater vehicle (UUV).
- UUV unmanned underwater vehicle
- FIGs. 91D-91F are graphs illustrating a magnetic field measurement component along the X-direction, Y-direction and Z-direction, respectively, at a time of 1000 seconds for a two-dimensional array of magnetic field sensors in the case of a single UUV.
- FIGs. 91G-91I are graphs illustrating a magnetic field measurement component along the X-direction, Y-direction and Z-direction, respectively, at a time of 1500 seconds for a two- dimensional array of magnetic field sensors in the case of a single UUV.
- FIGs. 92A-92C are graphs illustrating a magnetic field measurement component along the X-direction, Y-direction and Z-direction, respectively, at a time of 500 seconds for a two-dimensional array of magnetic field sensors in the case of two UUVs.
- FIGs. 92D-92F are graphs illustrating a magnetic field measurement component along the X-direction, Y-direction and Z-direction, respectively, at a time of 1000 seconds for a two-dimensional array of magnetic field sensors in the case of two UUVs.
- FIGs. 92G-92I are graphs illustrating a magnetic field measurement component along the X-direction, Y-direction and Z-direction, respectively, at a time of 1500 seconds for a two- dimensional array of magnetic field sensors in the case of two UUVs.
- FIG. 93 A is a graph illustrating the X-direction component of the noise free and measured magnetic fields as a function of time for a single magnetic field sensor measurement.
- FIG. 93B is a graph illustrating the noise free and reconstructed X-direction component of the magnetic field as a function of time for a single magnetic field sensor measurement as a function of time, where the noise has been removed by a median subtraction algorithm.
- FIG. 93 C is a graph illustrating the difference in the noise free and reconstructed X- direction component of the magnetic fields of FIG. 93B.
- FIGs. 94A-94C are graphs illustrating the magnetic field for an array of sensors including the signal of interest in the X-direction for the array at times of 500, 1000 and 1500 seconds, respectively.
- FIGs. 95 A-95C are graphs illustrating, in the X-direction, a region of interest and a expanded region of interest as a results of set closing and convex hulling, at respective times of 500, 1000 and 1500 seconds for a single UUV.
- FIGs. 96A-96C are graphs illustrating a fit to a plane of the X-direction component of magnetic field measurement data with the region of interest data removed for a two-dimensional array of magnetic field sensors at times of 500, 1000 and 1500 seconds, respectively.
- FIG. 9 ⁇ is a graph illustrating the X-direction component of noise free and measured magnetic fields as a function of time for a single magnetic field sensor measurement.
- FIG. 97B is a graph illustrating the noise free and reconstructed X-direction component of the magnetic field as a function of time for a single magnetic field sensor measurement as a function of time, where the noise has been removed using noise fit to a plane.
- FIG. 97C is a graph illustrating the difference in the noise free and reconstructed X- direction component of the magnetic field of FIG. 97B.
- FIGs. 98A-98C are graphs illustrating a fit to a quadratic spline of the X-direction component of magnetic field measurement data with the region of interest data removed for a two-dimensional array of magnetic field sensors at times of 500, 1000 and 1500 seconds, respectively.
- FIG. 99 A is a graph illustrating the X-direction component of noise free and measured magnetic fields as a function of time for a single magnetic field sensor measurement.
- FIG. 99B is a graph illustrating the noise free and reconstructed X-direction component of the magnetic field as a function of time for a single magnetic field sensor measurement as a function of time, where the noise has been removed using noise fit to a quadratic spline.
- FIG. 99C is a graph illustrating the difference in the noise free and reconstructed X- direction component of the magnetic field of FIG. 99B.
- FIGs. lOOA-lOOC are graphs illustrating, in the X-direction, a region of interest and a expanded region of interest as a results of set closing and convex hulling, at respective times of 500, 1000, and 1500 seconds for two UUVs.
- FIGs. 101 A-101C are graphs illustrating a fit to a quadratic spline of the X-direction component of magnetic field measurement data with the region of interest data removed for a two-dimensional array of magnetic field sensors at times of 500, 1000 and 1500 seconds, respectively, for two UUVs.
- FIG. 102A is a graph illustrating X-direction component of noise free and measured magnetic fields as a function of time for a single magnetic field sensor measurement for two UUVs.
- FIG. 102B is a graph illustrating the noise free and reconstructed X-direction component of the magnetic field as a function of time for a single magnetic field sensor measurement as a function of time, where the noise has been removed using noise fit to a quadratic spline.
- FIG. 102C is a graph illustrating the difference in the noise free and reconstructed X- direction component of the magnetic field of FIG. 102B.
- FIG. 103 A is a top perspective view of a sensor assembly according to an
- FIG. 103B is a bottom perspective view of the sensor assembly of FIG. 103 A.
- FIG. 104A is a top perspective view of a diamond assembly of the sensor assembly of FIG. 103 A.
- FIG. 104B is a bottom perspective view of the diamond assembly of FIG. 104A.
- FIG. 104C is a side view of an assembly substrate of the sensor assembly of FIG. 104 A.
- FIG. 105 is a top view of the diamond assembly of FIG. 104A.
- FIG. 106A and 106B are side views of diamond material with metal layers illustrating steps of forming a RF excitation source according to an embodiment.
- FIG. 107A is a top view of the diamond assembly according to another embodiment.
- FIG. 107B is a side view of the diamond assembly if FIG. 107A.
- FIG. 108 is a graphical diagram depicting NV0 and NV- photon intensity relative to wavelength without fluorescence manipulation.
- FIG. 109 is a graphical diagram for the indirect band gap for a diamond having nitrogen vacancies depicting a valence band and a conduction band on an energy versus momentum (E vs. k) plot and showing a zero phonon line, an optical drive for exciting an electron over the band gap, and the recombination of the electron from various points of the conduction band to generate photons.
- E vs. k energy versus momentum
- FIG. 110 is a graphical diagram depicting NV0 and NV- photon intensity relative to wavelength with fluorescence manipulation.
- FIG. 111 is a process diagram for fluorescence manipulation of the diamond having nitrogen vacancies through phonon spectrum manipulation using an acoustic driver.
- FIG. 112 is a process diagram for determining an acoustic driving frequency for phonon spectrum manipulation.
- FIG. 113 A is a block diagram of a magnetometer with a light pipe in accordance with an illustrative embodiment.
- FIGs. 113B and 113C are isometric views of a light pipe and a shield in accordance with illustrative embodiments.
- FIG. 114 is a block diagram of a magnetometer with two light pipes in accordance with an illustrative embodiment.
- FIG. 115 is a block diagram of a magnetometer with two light pipes in accordance with an illustrative embodiment.
- FIG. 116 is a flow diagram of a method for measuring a magnetic field in accordance with an illustrative embodiment.
- FIG. 117 is a block diagram of a magnetometer in accordance with an illustrative embodiment.
- FIG. 118 is an exploded view of a magnetometer in accordance with an illustrative embodiment.
- FIG. 119 is a flow diagram of a method for detecting a magnetic field in accordance with an illustrative embodiment.
- FIG 120 is a schematic illustrating a portion of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- FIG. 121 is a view of an enclosed DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- FIGs. 122A and 122B are schematics of an assembly portion of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- FIG. 123 is a cross-section of a portion of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- FIG. 124 is a schematic illustrating a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- FIG. 125 is a cross-section of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- FIG. 126 is a schematic illustrating a DNV sensor with a dual RF arrangement and laser mounting in accordance with some illustrative implementations.
- FIG. 127 is a cross-section of a DNV sensor with a dual RF arrangement and laser mounting in accordance with some illustrative implementations.
- FIGs. 128A and 128B are schematics of an assembly portion of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- FIGs. 129A and 129B are schematics of an assembly portion of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- FIG. 130 is a block diagram of an overview of a single-cycle synthesis, control, and acquisition system for a diamond nitrogen vacancy sensor.
- FIG. 131 is a block circuit diagram of the single-cycle control, synthesis, and acquisition processor for a diamond nitrogen vacancy sensor of FIG. 130.
- FIG. 132A is a block circuit diagram of the host interface of FIG. 131.
- FIG. 132B is a block circuit diagram of the program counter of FIG. 131.
- FIG. 132C is a block circuit diagram of the program memory of FIG. 131.
- FIG. 132D is a block circuit diagram of a first portion of the jump control with delay of FIG. 131.
- FIG. 132E is a block circuit diagram of a second portion of the jump control FIG. 131.
- FIG. 132F is a block circuit diagram of the RF waveform generator of FIG. 131.
- FIG. 132G is a block circuit diagram of the digital control of FIG. 131.
- FIG. 132H is a block circuit diagram of the acquisition processor of FIG. 131.
- FIG. 133A is a unit cell diagram of the crystal structure of a diamond lattice having a standard orientation.
- FIG. 133B is a unit cell diagram of the crystal structure of a diamond lattice having an unknown orientation.
- FIG. 134 is a schematic diagram illustrating a step in a method for determining the unknown orientation of the diamond lattice of FIG. 133B.
- FIG. 135 is a flowchart illustrating a sign recovery method for the method for determining the unknown orientation of the diamond lattice of FIG. 133B.
- FIG. 136 is a schematic diagram illustrating a step in the method for determining the unknown orientation of the diamond lattice of FIG. 133B.
- FIG. 137 is a flowchart illustrating a method for recovering a three-dimensional magnetic field on the NV center magnetic sensor system.
- FIG. 138 is an overview diagram of a diamond of a DNV sensor with a low pass filter and a high pass filter.
- FIG. 139 is graphical diagram of an example signal detected with a DNV sensor that includes a test signal without filtering.
- FIG. 140 is an overview diagram of a diamond of a DNV sensor with a low pass filter and showing a magnetic field of the environment, a change in the magnetic field of the environment, and an induced magnetic field by the low pass filter to filter high frequency signals.
- FIG. 141 is another overview diagram of a diamond of a DNV sensor with two low pass filters arranged for spatial attenuation.
- FIG. 142 is an overview diagram of a diamond of a DNV sensor relative to a diamagnetic material and showing alignment of the poles of the diamagnetic material relative to the induced magnetic field.
- FIG. 143 is a graphical diagram of magnetism in a diamagnetic material relative to the applied magnetic field.
- FIG. 144 is a process diagram for modifying a filtering frequency of a low pass filter for a DNV sensor based on a detected magnetic field.
- FIG. 145 is a process diagram for modifying an orientation of a DNV sensor with a low pass filter based on a detected magnetic field.
- FIG. 146 illustrates a low altitude flying object in accordance with some illustrative implementations.
- FIG. 147 illustrates a magnetic field detector in accordance with some illustrative implementations.
- FIGs. 148A and 148B illustrate a portion of a detector array in accordance with some illustrative implementations.
- FIG. 149 is a schematic illustrating a hydrophone in accordance with some illustrative implementations.
- FIG. 150 is a schematic illustrating a portion of a vehicle with a hydrophone in accordance with some illustrative implementations.
- FIG. 151 is a schematic illustrating a portion of a vehicle with a hydrophone with a containing membrane in accordance with some illustrative implementations.
- FIG. 152 is a schematic illustrating a portion of a vehicle with a hydrophone in accordance with some illustrative implementations.
- FIG. 153 is a schematic illustrating a portion of a vehicle with a hydrophone with a containing membrane in accordance with some illustrative implementations.
- FIG. 154 is a schematic illustrating a system for AC magnetic vector anomaly detection according to an embodiment of the invention.
- FIG. 155 is a schematic illustrating a sequence of optical excitation pulses and RF pulses according to the operation of the system of FIG. 156.
- FIG. 156 is a graph illustrating the fluorescence signal of NV diamond material as a function of RF excitation frequency over an range of RF frequencies according to an
- FIG. 157A illustrates a matched-filtered first correlated code for the magnetic field component along three different diamond lattice directions corresponding to the magnetic field provided by a first magnetic field generator according to an embodiment of the invention.
- FIG. 157B illustrates a matched-filtered first correlated code for the magnetic field component along three different diamond lattice directions corresponding to the magnetic field provided by a second magnetic field generator according to an embodiment of the invention.
- FIG. 158 illustrates reconstructed magnetic field vectors for two different correlated codes in the case where a ferrous object and no object are disposed in relation to a magnetic field generator and NV diamond material, according to an embodiment of the invention.
- FIGs. 159A and 159B are block diagrams of a system for detecting deformities in a material in accordance with an illustrative embodiment.
- FIGs. 160 illustrates current paths through a conductor with a deformity in accordance with an illustrative embodiment.
- FIGs. 161 is a flow diagram of a method for detecting deformities in accordance with an illustrative embodiment.
- FIG. 162 is a block diagram of a vehicular system in accordance with an illustrative embodiment.
- FIG. 163 is a flow chart of a method for charging a power source in accordance with an illustrative embodiment.
- FIG. 164 is a graph of the strength of a magnetic field versus distance from the conductor in accordance with an illustrative embodiment.
- FIGs. 165 A and 165B are block diagrams of a system for detecting deformities in transmission lines in accordance with an illustrative embodiment.
- FIG. 166 illustrates current paths through a transmission line with a deformity in accordance with an illustrative embodiment.
- FIG. 167 illustrates power transmission line sag between transmission towers in accordance with an illustrative embodiment.
- FIG. 168 illustrates vector measurements indicating power transmission line sag in accordance with an illustrative embodiment.
- FIG. 169 illustrates vector measurements along a path between adjacent towers in accordance with an illustrative embodiment.
- aspects of the disclosure relates to apparatuses and methods for elucidating hyperfine transition responses to determine an external magnetic field acting on a magnetic detection system.
- the hyperfine transition responses exhibit a steeper gradient than the gradient of aggregate Lorentzian responses measured in conventional systems, which can be up to three orders of magnitude larger.
- the steeper gradient exhibited by the hyperfine transition responses thus allow for a comparable increase in measurement sensitivity in a magnetic detection system.
- external magnetic fields may be detected more accurately, especially low magnitude and/or rapidly changing fields.
- the NV center in a diamond comprises a substitutional nitrogen atom in a lattice site adjacent a carbon vacancy as shown in FIG. 1.
- the NV center may have four orientations, each corresponding to a different crystallographic orientation of the diamond lattice.
- the NV center may exist in a neutral charge state or a negative charge state.
- the neutral charge state uses the nomenclature NV°, while the negative charge state uses the nomenclature NV, which is adopted in this description.
- the NV center has a number of electrons, including three unpaired electrons, each one from the vacancy to a respective of the three carbon atoms adjacent to the vacancy, and a pair of electrons between the nitrogen and the vacancy.
- the NV center which is in the negatively charged state, also includes an extra electron.
- the optical transitions between the ground state 3 A 2 and the excited triplet 3 E are predominantly spin conserving, meaning that the optical transitions are between initial and final states that have the same spin.
- a photon of red light is emitted with a photon energy corresponding to the energy difference between the energy levels of the transitions.
- the system 300 includes an optical excitation source 310, which directs optical excitation to an
- the system further includes an RF excitation source 330, which provides RF radiation to the NV diamond material 320.
- Light from the NV diamond may be directed through an optical filter 350 to an optical detector 340.
- the RF excitation source 330 may be a microwave coil, for example.
- the optical excitation source 310 may be a laser or a light emitting diode, for example, which emits light in the green, for example.
- the optical excitation source 310 induces fluorescence in the red, which corresponds to an electronic transition from the excited state to the ground state.
- Light from the NV diamond material 320 is directed through the optical filter 350 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the detector 340.
- the component Bz may be determined.
- Optical excitation schemes other than continuous wave excitation are contemplated, such as excitation schemes involving pulsed optical excitation, and pulsed RF excitation. Examples of pulsed excitation schemes include Ramsey pulse sequence, and spin echo pulse sequence.
- the diamond material 320 will have NV centers aligned along directions of four different orientation classes.
- FIG. 5 illustrates fluorescence as a function of RF frequency for the case where the diamond material 320 has NV centers aligned along directions of four different orientation classes.
- the component Bz along each of the different orientations may be determined.
- crystallographic planes of a diamond lattice allow not only the magnitude of the external magnetic field to be determined, but also the direction of the magnetic field.
- FIG. 3 illustrates an NV center magnetic sensor system 300 with NV diamond material 320 with a plurality of NV centers
- the magnetic sensor system may instead employ a different magneto-optical defect center material, with a plurality of magneto-optical defect centers.
- the electronic spin state energies of the magneto-optical defect centers shift with magnetic field, and the optical response, such as fluorescence, for the different spin states is not the same for all of the different spin states.
- the magnetic field may be determined based on optical excitation, and possibly RF excitation, in a corresponding way to that described above with NV diamond material.
- FIG. 6 is a schematic diagram of a system 600 for a magnetic field detection system according to an embodiment of the present invention.
- the system 600 includes an optical excitation source 610, which directs optical excitation to an NV diamond material 620 with NV centers, or another magneto-optical defect center material with magneto-optical defect centers.
- An RF excitation source 630 provides RF radiation to the NV diamond material 620.
- a first magnetic field generator 670 generates a magnetic field, which is detected at the NV diamond material 620.
- the first magnetic field generator 670 may be a permanent magnet positioned relative to the NV diamond material 620, which generates a known, uniform magnetic field (e.g., a bias or control magnetic field) to produce a desired fluorescence intensity response from the NV diamond material 620.
- a second magnetic field generator 675 may be provided and positioned relative to the NV diamond material 620 to provide an additional bias or control magnetic field.
- the second magnetic field generator 675 may be configured to generate magnetic fields with orthogonal polarizations, for example.
- the second magnetic field generator 675 may include one or more coils, such as a Helmholtz coils.
- the coils may be configured to provide relatively uniform magnetic fields at the NV diamond material 620 and each may generate a magnetic field having a direction that is orthogonal to the direction of the magnetic field generated by the other coils.
- the second magnetic field generator 675 may include three Helmholtz coils that are arranged to each generate a magnetic field having a direction orthogonal to the other direction of the magnetic field generated by the other two coils resulting in a three- axis magnetic field.
- only the first magnetic field generator 670 may be provided to generate a bias or control magnetic field.
- the first and/or second magnetic field generators may be affixed to a pivot assembly (e.g., a gimbal assembly) that may be controlled to hold and position the first and/or second magnetic field generators to a predetermined and well-controlled set of orientations, thereby establishing the desired bias or control magnetic fields.
- the controller 680 may be configured to control the pivot assembly having the first and/or second magnetic field generators to position and hold the first and/or second magnetic field generators at the predetermined orientation.
- the system 600 further includes a controller 680 arranged to receive a light detection or optical signal from the optical detector 640 and to control the optical excitation source 610, the RF excitation source 630, and the second magnetic field generator 675.
- the controller may be a single controller, or multiple controllers. For a controller including multiple controllers, each of the controllers may perform different functions, such as controlling different components of the system 600.
- the second magnetic field generator 675 may be controlled by the controller 680 via an amplifier 660, for example.
- the RF excitation source 630 may be a microwave coil, for example.
- the optical excitation source 610 may be a laser or a light emitting diode, for example, which emits light in the green, for example.
- the optical excitation source 610 induces fluorescence in the red from the NV diamond material 620, where the fluorescence corresponds to an electronic transition from the excited state to the ground state.
- Light from the NV diamond material 620 is directed through the optical filter 650 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 640.
- the controller 680 is arranged to receive a light detection signal from the optical detector 640 and to control the optical excitation source 610, the RF excitation source 630, and the second magnetic field generator 675.
- the controller may include a processor 682 and a memory 684, in order to control the operation of the optical excitation source 610, the RF excitation source 630, and the second magnetic field generator 675.
- the memory 684 which may include a nontransitory computer readable medium, may store instructions to allow the operation of the optical excitation source 610, the RF excitation source 630, and the second magnetic field generator 675 to be controlled. That is, the controller 680 may be programmed to provide control.
- the pair of frequency responses also known as Lorentzian responses, profiles, or dips
- the pair of frequency responses manifest as dips in intensity of the emitted red light from the NV centers as a function of RF carrier frequency.
- a bias magnetic field is applied to the NV diamond material (such as by the first and/or second magnetic field generators 670, 675 of FIG.
- Point 25 represents the point of the greatest gradient of the Lorentzian dip 20. This point gives the greatest measurement sensitivity in detecting changes in the total incident magnetic field as it responds to the external magnetic field.
- Each of the three hyperfine transitions manifest within the width of one aggregate Lorentzian dip. With proper detection, the hyperfine transitions may be elucidated within a given Lorentzian response.
- the NV diamond material 620 exhibits a high purity (e.g., low existence of lattice dislocations, broken bonds, or other elements beyond 14 N) and does not have an excess concentration of NV centers.
- the RF excitation source 630 is operated on a low power setting in order to further resolve the hyperfine responses. In other embodiments, additional optical contrast for the hyperfine responses may be
- NV negative-charge type centers accomplished by increasing the concentration of NV negative-charge type centers, increasing the optical power density (e.g., in a range from about 20 to about 1000 mW/mm 2 ), and decreasing the RF power to the lowest magnitude that permits a sufficient hyperfine readout (e.g., about 1 to about lO W/rara 2 ).
- FIG. 9 shows an example of fluorescence intensity as a function of an applied RF frequency for an NV center with hyperfine detection.
- the gradient ⁇ ⁇ - plotted against the applied RF frequency f(t) is shown.
- the three hyperfine transitions 200a-200c constitute a complete Lorentzian response 20 (e.g., corresponding to the Lorenztian response 20 in FIG. 7).
- the point of maximum slope may then be determined through the gradient of the fluorescence intensity as a function of the applied RF frequency, which occurs at the point 250 in FIG. 9. This point of maximum slope may then be tracked during the applied RF sweep to detect movement of the point of maximum slope along the frequency sweep. Like the point of maximum slope 25 for the aggregate Lorentzian response, the corresponding movement of the point 250 corresponds to changes in the total incident magnetic field B t (t), which because of the known and constant bias field B bias (t), allows for the detection of changes in the external magnetic field B ext (t).
- point 250 exhibits a larger gradient than the aggregate Lorentzian gradient described above with regard to FIG. 7.
- the gradient of point 250 may be up to 1000 times larger than the aggregate Lorentzian gradient of point 25. Due to this, the point 250 and its corresponding movement may be more easily detected by the measurement system resulting in improved sensitivity, especially in very low magnitude and/or very rapidly changing magnetic fields.
- the subject technology can allow efficient collection of the emitted light of the diamond of the DNV sensor with a compact and low cost reflector.
- the reflector can focus the emitted light of the diamond of the DNV sensor to an optical or photo detector that can increase the amount of light detected from the diamond.
- such a configuration may detect virtually all light emitted by the diamond of the DNV sensor.
- the reflector may be shaped as a parabola, an ellipse, or other shapes that can convey the light emitted from a source to a focal point or focal area.
- the diamond of the DNV sensor may be machined or otherwise shaped to be a reflector itself. That is, the diamond with nitrogen vacancies may be shaped to form a parabolic reflector, ellipsoidal reflector or other shapes that can convey the light emitted from the nitrogen vacancies to a focal point or focal area.
- the reflector can be mostly parabolic or ellipsoidal such that the light hits the photo detector at a 90 degree angle with some margin of error, e.g., 2 to 10 degrees.
- the nitrogen vacancies of the diamond will fluoresce in response to excitation with green light and will emit red light in random directions.
- the red light measurements are shot noise limited, collecting as much emitted light as possible is desirable. In some current collection approaches using large optics, the collection efficiencies were in the range of 20%.
- Some implementations use a large aperture lens mounted close to the diamond or DNV sensor, which limits light collection to a fraction of the light emitted by the diamond or DNV sensor.
- Other implementations use a flat diamond and a number of photo detectors (e.g., four) positioned at the edges of the flat diamond. This arrangement of photo detectors may be able to capture more of the emitted light conducted to edges of the flat diamond due to internal reflection, but increases the number of photo detectors required and may not capture light emitted from the faces of the flat diamond.
- the DNV sensors discussed herein provide an alternative to increase the collection efficiency.
- FIG. 10 depicts an overview of an assembly 1000 with an example diamond 1002 having nitrogen vacancies and a reflector 1004 positioned about the diamond 1002 for a DNV light-collection apparatus.
- the reflector 1004 is positioned about the diamond 1002 to reflect a portion of the light emitted 1006 from the diamond 1002.
- the reflector 1004 is an elliptical or ellipsoidal reflector with the diamond 1002 positioned within a portion of the reflector 1004.
- the reflector 1004 may be parabolic or any other geometric configuration to reflect light emitted from the diamond 1002.
- the reflector 1004 may be a monolithic reflector, a hollow reflector, or any other type of reflector to reflect light emitted from the diamond 1002.
- the diamond 1002 is positioned at a focus 1008 of the reflector 1004.
- a photo detector may be positioned at the second focus to collect the reflected light.
- FIG. 11 depicts an assembly 1100 with an example diamond 1102 having nitrogen vacancies and an ellipsoidal reflector 1104 positioned about the diamond 1102 for a DNV light- collection apparatus.
- the ellipsoidal reflector 1104 can be a single monolithic component that can be considered to be divided into two portions, such as a reflector portion 1106 and a concentrator portion 1108.
- the ellipsoidal reflector 1104 may be divided into two components, such as the reflector portion 1106 and the
- the reflector portion 1106 and the concentrator portion 1108 may be separate parabolic components that can be combined to form the ellipsoidal reflector 1104.
- the ellipsoidal reflector 1104 may be composed of more than two components and can be coupled or otherwise positioned to form the ellipsoidal reflector 1104.
- the diamond 1102 is positioned at a first focus of the ellipsoidal reflector 1104 for the reflector portion 1106. In some implementations, the diamond 1102 is positioned at the first focus using a mount for the diamond 1102. In other implementations, the diamond 1102 is positioned at the first focus using a borehole through the ellipsoidal reflector 1104. The borehole may be backfilled to seal the diamond 1102 in the ellipsoidal reflector 1104.
- the ellipsoidal reflector 1104 may also include an opening to allow an excitation laser beam to excite the diamond 1102, such as a green excitation laser beam.
- the opening may be positioned at any location for the ellipsoidal reflector 1104.
- the reflector portion 1106 reflects the red light emitted 1110 from the diamond 1102 towards the concentrator portion 1108.
- the concentrator portion 1108 directs the emitted light 1110 toward a second focus of the ellipsoidal reflector 1104.
- a photo detector 1120 is positioned to receive and measure the light from the concentrator portion 1108.
- the photo detector 1120 is positioned at the second focus to receive the redirected emitted light.
- the photo detector 1120 is coupled and/or sealed to a portion of the ellipsoidal reflector 1104, such as to the concentrator portion 1108.
- the opening may be adjacent or proximate to the photo detector 1120, such as through the
- the opening may be opposite the photo detector 1120, such as through the reflector portion 1106. In still further configurations, the opening may be at any other angle and/or orientation relative to the photo detector 1120.
- an optical filter such as a red filter, may be applied to and/or positioned on the photo detector 1120 to filter out light except the relevant red light of interest.
- the ellipsoidal reflector 1104 is concatenated with a non-focusing concentrator that can capture the emitted light from a light source (e.g., from the nitrogen vacancies of the diamond of a DNV sensor) to a single photo detector.
- the loss of emitted light can be limited to the light loss due to the mount for the diamond and/or the small entrance for the green stimulation laser beam.
- the foregoing solution provides high light collection efficiency to collect the light emitted from the diamond 1102, while utilizing a reflector 1104 that may not require high precision refinements.
- a reflector 1104 may be a low cost solution to increase the light collection efficiency, such as using a reflective mirror component.
- the shape of the ellipsoidal reflector 1104 may separate the electronics of the photo detector 1120 from the diamond 1102, which may decrease the magnetic interaction between the electronics of the photo detector 1120 and the diamond 1102.
- the elliptical reflector 1104 may, in some implementations, include a substrate with a dielectric mirror film or coating applied to reflect the emitted light 1110.
- the dielectric mirror film may be selected for the specific frequency of interest.
- the thickness of the dielectric mirror material may affect the specific frequency of interest.
- the substrate may possess a high clarity at a frequency of interest for the DNV sensor.
- the substrate may be made of a plastic, glass, diamond, quartz, and/or any other suitable material.
- the dielectric mirror film may be applied to the substrate such that the light emitted 1110 from the diamond 1102 is reflected within the ellipsoidal reflector 1104.
- the dielectric mirror film may only reflect red light such that other colors or wavelengths of light pass through the ellipsoidal reflector 1104.
- a dielectric mirror film may permit transmission of green wavelength light, such as from an excitation laser beam, through the ellipsoidal reflector 1104 to the diamond 1102 to excite the diamond 1102.
- the separation between the diamond 1102 and the electronics of the photo detector 1120 can be extended, for example to several feet.
- the thin dielectric mirror film is used in the ellipsoidal reflector 1104 to allow an RF antenna to be located inside the ellipsoidal reflector 1104. In some applications, the antenna may instead be outside of the ellipsoidal reflector 1104.
- FIG. 12 depicts an assembly 1200 with an example diamond 1202 having nitrogen vacancies that is formed or machined into a reflector configuration for a DNV light-collection apparatus.
- the diamond 1202 in the present configuration is formed or machined into an ellipsoidal reflector and is a monolithic component that can be considered to be divided into two portions, such as a reflector portion 1204 and a concentrator portion 1206.
- the diamond 1202 may have a dielectric mirror film coated on or applied to the diamond 1202.
- the dielectric mirror film may be selected for the specific frequency of interest. In some implementations, the thickness of the dielectric mirror material may affect the specific frequency of interest.
- the dielectric mirror film may be applied such that the light emitted 1210 from the nitrogen vacancies within the diamond 1202 is reflected within the reflector portion 1204 and concentrator portion 1206 of the diamond 1202. In some implementations, the dielectric mirror film may only reflect red light such that other colors or wavelengths of light pass through the diamond 1202. For instance, such a dielectric mirror film may permit transmission of green wavelength light, such as from an excitation laser beam, through the dielectric mirror film to the nitrogen vacancies of the diamond 1202 to excite the nitrogen vacancies of the diamond 1202.
- the reflector portion 1204 of the diamond 1202 may internally reflect the emitted light 1210 via the dielectric mirror film applied to the diamond 1202.
- the diamond 1202 internally reflects the red light emitted 1210 from the diamond 1202 towards the concentrator portion 1206.
- the concentrator portion 1206 also redirects the light emitted 1210 by the nitrogen vacancies of the diamond 1202 toward a focus of the concentrator portion 1206 of the diamond 1202.
- a photo detector 1220 is positioned to receive and measure the light from the concentrator portion 1206.
- the photo detector 1220 is positioned at the focus to receive the redirected emitted light 1210.
- the photo detector 1220 is coupled and/or sealed to a portion of the diamond 1202, such as to the concentrator portion 1206.
- an optical filter such as a red filter, may be applied to and/or positioned on the photo detector 1220 to filter out light except the relevant red light of interest.
- a portion of the diamond 1202 may be formed without nitrogen vacancies. That is, for instance, one or more layers for the diamond may be formed by chemical deposition without nitrogen vacancies. The one or more layers may be machined or formed for the concentrator portion such that the emitted light reflected by the reflector portion 1204 is not reabsorbed by nitrogen vacancies when travelling through the concentrator portion 1206 of the diamond 1202.
- FIG. 13 depicts an assembly 1300 with an example diamond 1302 having nitrogen vacancies and a parabolic reflector 1304 positioned about the diamond 1302 for a DNV light- collection apparatus.
- the parabolic reflector 1304 can be a single monolithic component.
- the parabolic reflector 1304 may be composed of more than two components and can be coupled or otherwise positioned to form the parabolic reflector 1304.
- the diamond 1302 is positioned at a focus of the parabolic reflector 1304. In some implementations, the diamond 1302 is positioned at the focus using a mount for the diamond 1302. In other implementations, the diamond 1302 is positioned at the focus using a borehole through the parabolic reflector 1304. The borehole may be backfilled to seal the diamond 1302 in the parabolic reflector 1304.
- the parabolic reflector 1304 may also include an opening to allow an excitation laser beam to excite the diamond 1302, such as a green excitation laser beam.
- the opening may be positioned at any location for the parabolic reflector 1304.
- the parabolic reflector 1304 reflects the red light emitted 1310 from the diamond 1302 towards a photo detector 1320.
- a photo detector 1320 is positioned to receive and measure the light from the parabolic reflector 1304.
- the photo detector 1320 is coupled and/or sealed to a portion of the parabolic reflector 1304.
- the opening may be adjacent or proximate to the photo detector 1320. In other implementations, the opening may be opposite the photo detector 1320. In still further configurations, the opening may be at any other angle and/or orientation relative to the photo detector 1320.
- an optical filter such as a red filter
- a red filter may be applied to and/or positioned on the photo detector 1320 to filter out light except the relevant red light of interest.
- the parabolic reflector 1304 is concatenated with a non-focusing concentrator that can capture the emitted light from a light source (e.g., from the nitrogen vacancies of the diamond of a DNV sensor) to a single photo detector.
- the loss of emitted light can be limited to the light loss due to the mount for the diamond and/or the small entrance for the green stimulation laser beam.
- the foregoing solution provides high light collection efficiency to collect the light emitted from the diamond 1302, while utilizing a parabolic reflector 1304 that may not require high precision refinements.
- a parabolic reflector 1304 may be a low cost solution to increase the light collection efficiency, such as using a reflective mirror component.
- the shape of the parabolic reflector 1304 may separate the electronics of the photo detector 1320 from the diamond 1302, which may decrease the magnetic interaction between the electronics of the photo detector 1320 and the diamond 1302.
- the parabolic reflector 1304 may, in some implementations, include a substrate with a dielectric mirror film or coating applied to reflect the emitted light 1310.
- the dielectric mirror film may be selected for the specific frequency of interest.
- the thickness of the dielectric mirror material may affect the specific frequency of interest.
- the substrate may possess a high clarity at a frequency of interest for the DNV sensor.
- the substrate may be made of a plastic, glass, diamond, quartz, and/or any other suitable material.
- the dielectric mirror film may be applied to the substrate such that the light emitted 1310 from the diamond 1302 is reflected within the parabolic reflector 1304.
- the dielectric mirror film may only reflect red light such that other colors or wavelengths of light pass through the parabolic reflector 1304.
- a dielectric mirror film may permit transmission of green wavelength light, such as from an excitation laser beam, through the parabolic reflector 1304 to the diamond 1302 to excite the diamond 1302.
- the separation between the diamond 1302 and the electronics of the photo detector 1320 can be extended, for example to several feet.
- the thin dielectric mirror film is used in the parabolic reflector 1304 to allow an RF antenna to be located inside the parabolic reflector 1304. In some applications, the antenna may instead be outside of the parabolic reflector 1304.
- FIG. 14 depicts an assembly 1400 with an example diamond 1402 having nitrogen vacancies that is formed or machined into a reflector configuration for a DNV light-collection apparatus.
- the diamond 1402 in the present configuration is formed or machined into a parabolic reflector and is a monolithic component.
- the diamond 1402 may have a dielectric mirror film coated on or applied to the diamond 1402.
- the dielectric mirror film may be selected for the specific frequency of interest. In some implementations, the thickness of the dielectric mirror material may affect the specific frequency of interest.
- the dielectric mirror film may be applied such that the light emitted 1410 from the nitrogen vacancies within the diamond 1402 is reflected within the diamond 1402. In some implementations, the dielectric mirror film may only reflect red light such that other colors or wavelengths of light pass through the diamond 1402. For instance, such a dielectric mirror film may permit transmission of green wavelength light, such as from an excitation laser beam, through the dielectric mirror film to the nitrogen vacancies of the diamond 1402 to excite the nitrogen vacancies of the diamond 1402.
- the parabolic reflector configuration for the diamond 1402 may internally reflect the emitted light 1410 via the dielectric mirror film applied to the diamond 1402.
- the diamond 1402 may internally reflect the emitted light 1410 via the dielectric mirror film applied to the diamond 1402.
- an optical filter such as a red filter, may be applied to and/or positioned on the photo detector 1420 to filter out light except the relevant red light of interest.
- a portion of the diamond 1402 may be formed without nitrogen vacancies. That is, for instance, one or more layers for the diamond may be formed by chemical deposition without nitrogen vacancies. The one or more layers may be machined or formed near the junction for the photo detector 1420 such that the emitted light reflected by the parabolic reflector configuration of the diamond 1402 is not reabsorbed by nitrogen vacancies when travelling through the one or more layers of the diamond 1402.
- FIG. 15 depicts another implementation of a parabolic reflector configuration for an assembly 1500 for a DNV sensor.
- An example thin diamond 1502 having nitrogen vacancies may be inserted into a portion of a parabolic reflector 1504 positioned about the diamond 1502 for a DNV light-collection apparatus.
- the parabolic reflector 1504 can be a single monolithic component that is split into two portions to insert the thin diamond 1502.
- the parabolic reflector 1504 may be composed of more than two components and can be coupled or otherwise positioned to form the parabolic reflector 1504.
- the thin diamond 1502 is inserted parallel to (and in some instances along) an axis of symmetry the parabolic reflector 1504.
- the thin diamond 1502 may be inserted parallel to and/or along a major axis of the ellipsoidal reflector.
- the parabolic reflector 1504 may also include an opening to allow an excitation laser beam to excite the diamond 1502, such as a green excitation laser beam.
- the opening may be positioned at any location for the parabolic reflector 1504.
- the parabolic reflector 1504 reflects the red light emitted 1510 from the diamond 1502 towards a photo detector 1520.
- a photo detector 1520 is positioned to receive and measure the light from the parabolic reflector 1504.
- the photo detector 1520 is coupled and/or sealed to a portion of the parabolic reflector 1504.
- the opening may be adjacent or proximate to the photo detector 1520. In other implementations, the opening may be opposite the photo detector 1520. In still further configurations, the opening may be at any other angle and/or orientation relative to the photo detector 1520.
- an optical filter such as a red filter
- a red filter may be applied to and/or positioned on the photo detector 1520 to filter out light except the relevant red light of interest.
- the parabolic reflector 1504 is concatenated with a non-focusing concentrator that can capture the emitted light from a light source (e.g., from the nitrogen vacancies of the diamond of a DNV sensor) to a single photo detector.
- the loss of emitted light can be limited to the light loss due to the mount for the diamond and/or the small entrance for the green stimulation laser beam.
- the foregoing solution provides high light collection efficiency to collect the light emitted from the diamond 1502, while utilizing a parabolic reflector 1504 that may not require high precision refinements.
- a parabolic reflector 1504 may be a low cost solution to increase the light collection efficiency, such as using a reflective mirror component.
- the shape of the parabolic reflector 1504 may separate the electronics of the photo detector 1520 from the diamond 1502, which may decrease the magnetic interaction between the electronics of the photo detector 1520 and the diamond 1502.
- the parabolic reflector 1504 may, in some implementations, include a substrate with a dielectric mirror film or coating applied to reflect the emitted light 1510.
- the dielectric mirror film may be selected for the specific frequency of interest.
- the thickness of the dielectric mirror material may affect the specific frequency of interest.
- the substrate may possess a high clarity at a frequency of interest for the DNV sensor.
- the substrate may be made of a plastic, glass, diamond, quartz, and/or any other suitable material.
- the dielectric mirror film may be applied to the substrate such that the light emitted 1510 from the diamond 1502 is reflected within the parabolic reflector 1504.
- the dielectric mirror film may only reflect red light such that other colors or wavelengths of light pass through the parabolic reflector 1504.
- a dielectric mirror film may permit transmission of green wavelength light, such as from an excitation laser beam, through the parabolic reflector 1504 to the diamond 1502 to excite the diamond 1502.
- the separation between the diamond 1502 and the electronics of the photo detector 1520 can be extended, for example to several feet.
- the thin dielectric mirror film is used in the parabolic reflector 1504 to allow an RF antenna to be located inside the parabolic reflector 1504. In some applications, the antenna may instead be outside of the parabolic reflector 1504.
- FIG. 16 depicts another implementation of a parabolic reflector configuration for an assembly 1600 for a DNV sensor.
- An example thin diamond 1602 having nitrogen vacancies may be inserted into a portion of a parabolic reflector 1604 positioned about the diamond 1602 for a DNV light-collection apparatus.
- the parabolic reflector 1604 can be a single monolithic component that is split into two portions to insert the thin diamond 1602.
- the parabolic reflector 1604 may be composed of more than two components and can be coupled or otherwise positioned to form the parabolic reflector 1604.
- the thin diamond 1602 is inserted perpendicular to an axis of symmetry the parabolic reflector 1604.
- the thin diamond 1602 may be inserted parallel to and/or along a minor axis of the ellipsoidal reflector. In some implementations, the thin diamond 1602 is positioned at a focus of the parabolic reflector 1604.
- the parabolic reflector 1604 may also include an opening to allow an excitation laser beam to excite the diamond 1602, such as a green excitation laser beam.
- the opening may be positioned at any location for the parabolic reflector 1604.
- a photo detector 1620 is positioned to receive and measure the light from the parabolic reflector 1604.
- the photo detector 1620 is coupled and/or sealed to a portion of the parabolic reflector 1604.
- the opening may be adjacent or proximate to the photo detector 1620. In other implementations, the opening may be opposite the photo detector 1620. In still further configurations, the opening may be at any other angle and/or orientation relative to the photo detector 1620.
- an optical filter such as a red filter
- a red filter may be applied to and/or positioned on the photo detector 1620 to filter out light except the relevant red light of interest.
- the parabolic reflector 1604 is concatenated with a non-focusing concentrator that can capture the emitted light from a light source (e.g., from the nitrogen vacancies of the diamond of a DNV sensor) to a single photo detector.
- the loss of emitted light can be limited to the light loss due to the mount for the diamond and/or the small entrance for the green stimulation laser beam.
- the foregoing solution provides high light collection efficiency to collect the light emitted from the diamond 1602, while utilizing a parabolic reflector 1604 that may not require high precision refinements.
- a parabolic reflector 1604 may be a low cost solution to increase the light collection efficiency, such as using a reflective mirror component.
- the shape of the parabolic reflector 1604 may separate the electronics of the photo detector 1620 from the diamond 1602, which may decrease the magnetic interaction between the electronics of the photo detector 1620 and the diamond 1602.
- the parabolic reflector 1604 may, in some implementations, include a substrate with a dielectric mirror film or coating applied to reflect the emitted light 1610.
- the dielectric mirror film may be selected for the specific frequency of interest.
- the thickness of the dielectric mirror material may affect the specific frequency of interest.
- the substrate may possess a high clarity at a frequency of interest for the DNV sensor.
- the substrate may be made of a plastic, glass, diamond, quartz, and/or any other suitable material.
- the dielectric mirror film may be applied to the substrate such that the light emitted 1610 from the diamond 1602 is reflected within the parabolic reflector 1604.
- the dielectric mirror film may only reflect red light such that other colors or wavelengths of light pass through the parabolic reflector 1604.
- a dielectric mirror film may permit transmission of green wavelength light, such as from an excitation laser beam, through the parabolic reflector 1604 to the diamond 1602 to excite the diamond 1602.
- the separation between the diamond 1602 and the electronics of the photo detector 1620 can be extended, for example to several feet.
- the thin dielectric mirror film is used in the parabolic reflector 1604 to allow an RF antenna to be located inside the parabolic reflector 1604. In some applications, the antenna may instead be outside of the parabolic reflector 1604.
- FIG. 17 depicts an assembly 1700 for a DNV sensor that incorporates the assembly 1400 of FIG. 15 where the diamond 1402 is formed or machined into a parabolic configuration.
- the assembly 1700 includes the photo detector 1420 coupled to and/or positioned to receive the emitted light 1410 from the diamond 1402.
- the diamond 1402 includes the dielectric mirror film applied to the diamond 1402 to reflect the emitted red light 1410 within the diamond 1402. In some implementations, the dielectric mirror film may only reflect red light such that other colors or wavelengths of light pass through the diamond 1402.
- such a dielectric mirror film may permit transmission of green wavelength light 1710, such as from an excitation laser beam, through the dielectric mirror film to the nitrogen vacancies of the diamond 1402 to excite the nitrogen vacancies of the diamond 1402.
- the assembly 1700 includes microwave coils about the diamond 1402 such that, if the diamond 1402 is irradiated with microwaves at a certain frequency, then the diamond will cease and/or reduce the emission of red light.
- a microwave off is performed for the DNV sensor prior to illumination of the diamond 1402 to emit the red light 1410.
- the microwave frequency is moved to a different frequency, then the red light emitted is dimmed and the frequency is related to the strength of the magnetic field the DNV sensor is within.
- the green light 1710 from the green laser may be applied through a fiber, rather than the free air, to the diamond 1402.
- the entire apparatus of FIG. 17 may be as compact as ⁇ 2 mm.
- the assembly of the subject technology may be used in a number of applications, for example, in all areas of magnetometry, where DNV magnetometers are employed.
- FIG. 18 depicts another implementation of a reflector configuration for an assembly 1800 for a DNV sensor that includes a waveguide 1830 positioned within the reflector to direct light to a diamond 1802 having nitrogen vacancies.
- An example diamond 1802 having nitrogen vacancies may be inserted into a portion of a reflector 1804 positioned about the diamond 1802 for a DNV light-collection apparatus.
- the reflector 1804 may be a parabolic reflector or an ellipsoidal reflector.
- the reflector 1804 can be a single monolithic component or can be a shell component with a fill, such as plastic or fiber optic material, or without a fill (e.g., empty).
- a waveguide 1830 is formed or inserted along an axis of symmetry of the parabolic reflector 1804. In other implementations, the waveguide 1830 is formed or inserted along a major axis of an ellipsoidal reflector 1804.
- the waveguide 1830 may be a fiber optic component and/or may simply be a material having a differing refractive index than the reflector 1804 and/or the fill within the reflector 1804.
- the diamond 1802 is positioned at an end of the waveguide 1830 such that an excitation beam, such as green laser light, can be transmitted via the waveguide 1830 to the diamond 1802.
- an excitation beam such as green laser light
- the reflector 1804 reflects the red light emitted 1810 from the diamond 1802 towards a photo detector 1820.
- a photo detector 1820 is positioned to receive and measure the light from the reflector 1804.
- the photo detector 1820 is coupled and/or sealed to a portion of the reflector 1804.
- an opening for transmitting the excitation beam is through the photo detector 1820 such that the excitation beam can be transmitted via the waveguide 1830 to the diamond 1802.
- an emitter to emit light to excite the nitrogen vacancy of the diamond 1802, such as the excitation beam may be provided at a first end of the waveguide 1830 with the diamond 1802 at a second end of the waveguide 1830.
- the emitter may be formed and/or positioned within or at a center of the photo detector 1820 to generate and transmit the excitation beam along the waveguide 1830 to the diamond 1802.
- the photo detector 1820 and emitter may be positioned on a single substrate.
- a single chip can include both the photo detector 1820 and the emitter for the excitation beam such that both the illumination and collection can be provided on the single chip.
- an optical filter such as a red filter
- a red filter may be applied to and/or positioned on the photo detector 1820 to filter out light except the relevant red light of interest.
- the reflector 1804 is concatenated with a non-focusing concentrator that can capture the emitted light from a light source (e.g., from the nitrogen vacancies of the diamond of a DNV sensor) to a single photo detector.
- the loss of emitted light can be limited to the light loss due to the mount for the diamond and/or any emitted light that travels back down the waveguide 1830.
- the foregoing solution provides high light collection efficiency to collect the light emitted from the diamond 1802, while utilizing a reflector 1804 that may not require high precision refinements.
- a reflector 1804 may be a low cost solution to increase the light collection efficiency, such as using a reflective mirror component.
- the shape of the parabolic reflector 1804 may separate the electronics of the photo detector 1820 and/or emitter from the diamond 1802, which may decrease the magnetic interaction between the electronics of the photo detector 1820 and/or emitter and the diamond 1802.
- the reflector 1804 may, in some implementations, include a substrate with a dielectric mirror film or coating applied to reflect the emitted light 1810.
- the dielectric mirror film may be selected for the specific frequency of interest. In some implementations, the thickness of the dielectric mirror material may affect the specific frequency of interest.
- the substrate may possess a high clarity at a frequency of interest for the DNV sensor.
- the substrate may be made of a plastic, glass, diamond, quartz, and/or any other suitable material.
- the dielectric mirror film may be applied to the substrate such that the light emitted 1810 from the diamond 1802 is reflected within the reflector 1804. In some implementations, the dielectric mirror film may only reflect red light such that other colors or wavelengths of light pass through the reflector 1804.
- the separation between the diamond 1802 and the electronics of the photo detector 1820 can be extended, for example to several feet.
- the thin dielectric mirror film is used in the reflector 1804 to allow an RF antenna to be located inside the reflector 1804. In some applications, the antenna may instead be outside of the reflector 1804.
- FIG. 19 depicts an implementation of a process 1900 to form a DNV sensor.
- the process 1900 includes providing a diamond having a nitrogen vacancy (block 1902), machining a portion of the diamond to form a reflector (block 1904), positioning a photo detector relative to the diamond to receive light emitted from the diamond (block 1906), and/or applying a dielectric mirror film coat to a portion of the diamond (block 1908).
- the process 1900 may include simple providing a diamond having a nitrogen vacancy (block 1902) and applying a dielectric mirror film coat to a portion of the diamond (block 1908).
- the machining of the diamond to form a reflector may machine a portion of the diamond to form a parabolic shape, an ellipsoidal shape, and/or any other suitable shape.
- a layer of the diamond may not have nitrogen vacancies.
- FIG. 20 depicts another process 2000 to form a DNV sensor.
- the process 2000 includes providing a diamond having a nitrogen vacancy and a reflector (block 2002), positioning the diamond within the reflector such that the reflector reflects a portion of the light from the diamond (block 2004), and/or positioning a photo detector relative to the diamond to receive light emitted from the diamond (block 2006).
- the reflector is monolithic and the diamond is positioned within a borehole of the monolithic reflector.
- the borehole may be backfilled.
- the reflector may be formed from two or more pieces and positioning the diamond within the reflector includes inserting the diamond between the two or more pieces.
- the diamond may be substantially flat, such as in the
- the two or more pieces of the reflector may be parabolic in shape.
- the diamond may be positioned parallel to an axis of symmetry of the parabolic reflector or may be positioned perpendicular to the axis of symmetry.
- the two or more pieces of the reflector may be ellipsoidal in shape.
- the diamond may be positioned parallel to a major axis of the ellipsoidal reflector or may be positioned parallel to a minor axis of the ellipsoidal reflector.
- positioning the diamond within the reflector may include casting the reflector about the diamond.
- FIG. 21 is a diagram illustrating an example of a system 2100 for implementing some aspects of the subject technology.
- the system 2100 may be a processing system for processing the data output from a photo detector of the implementations describe in reference to FIGS. 11-19.
- the system 2100 includes a processing system 2102, which may include one or more processors or one or more processing systems.
- a processor can be one or more processors.
- the processing system 2102 may include a general-purpose processor or a specific-purpose processor for executing instructions and may further include a machine- readable medium 2119, such as a volatile or non-volatile memory, for storing data and/or instructions for software programs.
- the instructions which may be stored in a machine-readable medium 2110 and/or 2119, may be executed by the processing system 2102 to control and manage access to the various networks, as well as provide other communication and processing functions.
- the instructions may also include instructions executed by the processing system 2102 for various user interface devices, such as a display 2112 and a keypad 2114.
- the processing system 2102 may include an input port 2122 and an output port 2124. Each of the input port 2122 and the output port 2124 may include one or more ports.
- the input port 2122 and the output port 2124 may be the same port (e.g., a bi-directional port) or may be different ports.
- the processing system 2102 may be implemented using software, hardware, or a combination of both.
- the processing system 2102 may be implemented with one or more processors.
- a processor may be a general-purpose microprocessor, a
- DSP Digital Signal Processor
- ASIC Application Specific Integrated Circuit
- FPGA Field Programmable Gate Array
- PLD Programmable Logic Device
- controller a state machine, gated logic, discrete hardware components, or any other suitable device that can perform calculations or other manipulations of information.
- a machine-readable medium can be one or more machine-readable media.
- Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (e.g., in source code format, binary code format, executable code format, or any other suitable format of code).
- Machine-readable media e.g., 2119
- Machine-readable media may also include storage external to a processing system, such as a Random Access Memory (RAM), a flash memory, a Read Only Memory (ROM), a Programmable Read-Only Memory (PROM), an Erasable PROM (EPROM), registers, a hard disk, a removable disk, a CD-ROM, a DVD, or any other suitable storage device.
- RAM Random Access Memory
- ROM Read Only Memory
- PROM Programmable Read-Only Memory
- EPROM Erasable PROM
- registers a hard disk, a removable disk, a CD-ROM, a DVD, or any other suitable storage device.
- a machine-readable medium is a computer-readable medium encoded or stored with instructions and is a computing element, which defines structural and functional
- Instructions may be executable, for example, by the processing system 2102 or one or more processors. Instructions can be, for example, a computer program including code for performing methods of the subject technology.
- a network interface 2116 may be any type of interface to a network (e.g., an Internet network interface), and may reside between any of the components shown in FIG. 21 and coupled to the processor via the bus 2104.
- a network e.g., an Internet network interface
- a device interface 2118 may be any type of interface to a device and may reside between any of the components shown in FIG. 21.
- a device interface 2118 may, for example, be an interface to an external device (e.g., USB device) that plugs into a port (e.g., USB port) of the system 2100.
- the device interface 2118 may be an interface to the apparatus of FIGS. 10-18, where some or all of the analysis of the detected red light by the photo detector electronics is handled by the processing system 2102.
- the computer readable media does not include carrier waves and electronic signals passing wirelessly or over wired connections, or any other ephemeral signals.
- the computer readable media may be entirely restricted to tangible, physical objects that store information in a form that is readable by a computer.
- the computer readable media is non-transitory computer readable media, computer readable storage media, or non-transitory computer readable storage media.
- a computer program product also known as a program, software, software application, script, or code
- a computer program product can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, object, or other unit suitable for use in a computing
- a computer program may, but need not, correspond to a file in a file system.
- a program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code).
- a computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.
- the subject technology is directed to method and systems for an efficient collection of fluorescence (e.g., red light) emitted by the NV centers of a DNV sensor.
- fluorescence e.g., red light
- the subject technology may be used in various markets, including for example and without limitation, advanced sensors and materials and structures.
- a position sensor system may include a position sensor that includes a magnetic field sensor.
- the magnetic field sensor may be a DNV magnetic field sensor capable of resolving a magnetic field vector of the type described above.
- the high sensitivity of the DNV magnetic field sensor combined with an appropriate position encoder component is capable of resolving both a discrete position and a proportionally determined position between discrete positions.
- the position sensor system has a small size, light weight, and low power requirement.
- the position sensor 2220 may be part of a system that also includes an actuator 2210 and a sensor component 2230.
- the actuator 2210 may be connected to the position sensor 2220 by any appropriate attachment means 2214, such as a rod or shaft.
- the actuator may be any actuator that produces the desired motion, such as an electro-mechanical actuator.
- the position sensor 2220 may be connected to the sensor component 2230 by any appropriate attachment means 2224, such as a rod or shaft.
- a controller 2240 may be included in the system and connected to the position sensor 2220 and optionally the actuator 2210 by electronic interconnects 2222 and 2212, respectively.
- the controller may be configured to receive a measured position from the position sensor 2220 and activate or deactivate the actuator to position the sensor 2230 in a desired position.
- the controller may be on the same substrate as the magnetic field sensor of the position sensor.
- the controller may include a processor and a memory.
- the position sensor may be a rotary position sensor.
- FIG. 23 depicts a rotary position sensor system that includes a rotary actuator 2380 that is configured to produce a rotation of a sensor 2390.
- a rotary position encoder 2310 is connected to the rotary actuator 2380 by a connection means 2382, such as a rod or shaft.
- a connection means 2392 is also provided between the rotary position encoder 2310 and the sensor 2390.
- a position sensor head 2320 is located to measure the magnetic field of magnetic elements located on the rotary position encoder 2310. The position sensor head 2320 is aligned with magnetic elements located on the rotary position encoder 2310 at a distance, r, from the center of the rotary position encoder.
- FIG. 24 A surface of the rotary position encoder 2310 that includes magnetic elements is shown in FIG. 24.
- the center 2440 of the rotary position encoder 2310 may be configured to attach to a connection means 2392, 2394 that connects the rotary position encoder 2310 to the actuator 2320 or the sensor 2390.
- Magnetic elements such as uniform coarse magnetic elements 2434 and tapered fine magnetic elements 2432, may be disposed on the surface of the rotary position encoder 2310 along an arc 2436 at a distance, r, from the center of the rotary position encoder.
- the magnetic elements on the rotary position encoder 2310 may be located on only a portion of the arc, as shown in FIG. 24, or around an entirety of the arc forming a circle of magnetic elements.
- the spacing between the magnetic elements on the rotary position encoder 2310 correlates to a discrete angular rotation, ⁇ .
- the distance between magnetic elements associated with the discrete angular rotation, ⁇ increases as r increases.
- the sensitivity of the magnetic field sensors employed in the position sensor allows r to be reduced while maintaining a high degree of precision for the angular position of the rotary position encoder.
- the rotary position encoder may have an r on the order of mm, such as an r of 1 mm to about 30 mm, or about 5 mm to about 20 mm.
- the rotary position encoder allows for the measurement of a rotary position with a precision of 0.5 micro-radians.
- the position sensor may be a linear position sensor.
- the linear position sensor system includes a linear actuator 2580 that is configured to produce linear motion of the linear position encoder 2510 and sensor 2590.
- the linear position encoder 2510 may be connected to the linear actuator by a connecting means 2582, such as a rod or shaft.
- the linear position encoder 2510 may be connected to the sensor 2590 by a connecting means 2592, such as a rod or shaft.
- a position sensor head 2520 is located to measure the magnetic field produced by magnetic elements disposed on the linear position encoder.
- a mechanical linkage such as a lever arm, may be utilized to multiply the change in position of the linear position encoder for an associated movement of the sensor.
- the linear position sensor may have a sensitivity that allows a change in position on the order of hundreds of nanometers to be resolved, such as a position change of 500 nm.
- the magnetic elements may be arranged on the linear or rotary position encoder in any appropriate configuration. As shown in FIG. 26, the magnetic elements may include both uniform coarse magnetic elements 2634 and tapered fine magnetic elements 2632.
- the uniform coarse magnetic elements 2634 may have an influence on the local magnetic field that is at least two orders of magnitude greater than the maximum influence of the tapered fine magnetic elements 2634.
- the coarse magnetic elements 2634 may be formed on the position encoder by any suitable process. According to one embodiment, a polymer loaded with magnetic material may be utilized to form the uniform coarse magnetic elements. The amount of magnetic material that may be included in the coarse magnetic elements is limited by potential interference with other elements in the system.
- the tapered fine magnetic elements may be formed by any suitable process on the position encoder.
- a polymer loaded with magnetic material may be utilized to form the tapered fine magnetic elements.
- the loading of the magnetic material in the polymer may be increased to produce a magnetic field gradient from a first end of the tapered fine magnetic element to a second end of the tapered fine magnetic element.
- the geometric size of the tapered fine magnetic element may be increased to create the desired magnetic field gradient.
- a magnetic field gradient of the tapered fine magnetic element may be about 10 nT/mm.
- the tapered fine magnetic elements 2632 as shown in FIG. 26 allow positions between the coarse magnetic elements 2634 to be accurately resolved.
- the position encoder on which the magnetic elements are disposed may be formed from any appropriate material, such as a ceramic, glass, polymer, or non-magnetic metal material.
- the size of the magnetic elements is limited by manufacturing capabilities.
- the magnetic elements on the position encoder may have geometric features on the order of nanometers, such as about 5 nm.
- FIG. 27 depicts an alternate magnetic element arrangement that may be employed when the additional precision provided by the tapered fine magnetic elements is not required.
- the magnetic element arrangement of FIG. 27 includes only coarse magnetic elements 2634.
- FIG. 13 depicts a magnetic element arrangement that does not include coarse magnetic elements.
- a similar effect to the coarse magnetic elements 2634 may be achieved by utilizing the transitions between the maximum of the tapered fine magnetic elements 2632 and the minimum of the adjacent tapered fine magnetic elements as indicators in much the same way that the coarse magnetic elements shown in FIGS. 26 and 27 indicate a discrete change in position.
- FIGS. 26-18 depict the magnetic element arrangements in linear form, similar magnetic element arrangements may be applied to a rotary position encoder.
- a single tapered magnetic element may be employed. Such an arrangement may be especially suitable for an application where only a small position range is required, as for a larger position range the increase in magnetic field with the increasing gradient of the magnetic element may interfere with other components of the position sensor system.
- the use of a single tapered magnetic element may allow a position to be determined without first initializing the position sensor by setting the position encoder to a known position.
- the ability of the magnetic field sensor to resolve a magnetic field vector may allow a single magnetic field sensor to be employed in the position sensor head when a single tapered fine magnetic element is utilized on the position encoder.
- the position sensor head 2620 may include a plurality of magnetic field sensors, as shown in FIG. 29.
- at least two magnetic field sensors 2624 and 2622 may be utilized in the position head sensor.
- the magnetic field sensors may be separated by a distance, a.
- the distance, a, between the magnetic sensors 2622 and 2624 may be less than the distance, d, between the coarse magnetic elements 2634.
- the relationship between the spacing of the magnetic field sensors and the spacing of the coarse magnetic elements may be 0. Id ⁇ a ⁇ d.
- the position sensor head 2620 may include a third and fourth magnetic field sensor.
- the magnetic field sensors in the position sensor head may be DNV magnetic field sensors of the type described above.
- the magnetic field sensor arrangement in the position sensor head 2620 depicted in FIG. 29 allows the direction of movement of the position encoder to be determined.
- the spacing between the magnetic field sensors 2624 and 2622 produces a delayed response to the magnetic field elements as the position encoder moves.
- the difference in measured magnetic field for each magnetic field sensor allows a direction of the movement of the position encoder to be determined, as for any given position of the position encoder a different output magnetic field will be measured by each magnetic field sensor.
- the increasing portion of the plots in FIG. 30 is produced by the tapered fine magnetic element and the square peak is produced by the coarse magnetic element.
- the controller of the position sensor system may be programmed to determine the position of position encoder, and thereby the sensor connected thereto, utilizing the output from the magnetic field sensors.
- the controller may include a line transection logic 402 function that determines when the coarse magnetic elements have passed the magnetic sensor.
- the output from two magnetic field sensors B 1 and B2 may be utilized to determine the direction of the position change based on the order in which a coarse magnetic element is encountered by the magnetic field sensors, and to count the number of coarse magnetic elements measured by the magnetic field sensors. Each coarse magnetic element adds a known amount of position change due to the known spacing between the coarse magnetic elements on the position encoder.
- An element gradient logic processing function 400 is programmed in the controller to determine the position between coarse magnetic elements based on the magnetic field signal produced by the tapered fine magnetic elements located between the coarse magnetic elements. As shown in FIG. 31, the element gradient logic processing 400 is utilized only when the line transection logic determines that the position is between coarse magnetic elements, or lines. In the case that the position is determined to be between coarse magnetic elements, a position correction, ⁇ , is calculated based on the magnetic field associated with the tapered fine magnetic elements. The position correction is then added to the sum of the position change calculated from the number of coarse magnetic elements that were counted. A final position may be calculated by adding the calculated position change to a starting position of the position encoder.
- the logic processing in the controller may be conducted by analog or digital circuits.
- the position sensor may be employed in a method for controlling the position of the position encoder.
- the method includes determining a movement direction required to reach a desired position, and activating the actuator to produce the desired movement.
- the position sensor is employed to monitor the change in position of the position encoder, and determine when to deactivate the actuator and stop the change in position.
- the change in position may be stopped once the desired position is reached.
- the method may additionally include initializing the position sensor system by moving the position encoder to a known starting point.
- the end position of the position encoder may be determined after the deactivation of the actuator, and the end position may be stored in a memory of the position sensor controller as a starting position for future movement.
- the ability of the position sensor system to resolve positions between the coarse magnetic elements of the position encoder provides many practical benefits.
- the position of the position encoder, and associated sensor may be known with more precision while reducing the size, weight and power requirements of the position sensor system.
- position control systems that offer resolution of discrete position movements can result in dithering when a desired position is between two discrete position values. Dithering can result in unwanted vibration and overheating of the actuator as the control system repeatedly tries to reach the desired position.
- the characteristics of the position sensor system described above make it especially suitable for applications where precision, size, weight, and power requirements are important considerations.
- the position sensor system is well suited for astronautic applications, such as on space vehicles.
- the position sensor system is also applicable to robot arms, 3-d mills, machine tools, and X-Y tables.
- the position sensor system may be employed to control the position of a variety of sensors and other devices.
- sensors that could be controlled with the position sensor system are optical sensors.
- Radio waves can be used as a carrier for information.
- a transmitter can modulate radio waves at one location, and a receiver at another location can detect the modulated radio waves and demodulate the signals to receive the information.
- Many different methods can be used to transmit information via radio waves. However, all such methods use radio waves as a carrier for the information being transmitted.
- radio waves are not well suited for all communication methods.
- radio waves can be greatly attenuated by some materials.
- radio waves do not generally travel well through water.
- communication through water can be difficult using radio waves.
- radio waves can be greatly attenuated by the earth.
- wireless communication through the earth for example for coal or other mines, can be difficult.
- the strength of a radio wave signal can also be reduced as the radio wave passes through materials such as walls, trees, or other obstacles.
- communication via radio waves is widely used and understood.
- secret communication using radio waves requires complex methods and devices to maintain the secrecy of the information.
- wireless communication is achieved without using radio waves as a carrier for information.
- modulated magnetic fields can be used to transmit information.
- a transmitter can include a coil or inductor. When current passes through the coil, a magnetic field is generated around the coil. The current that passes through the coil can be modulated, thereby modulating the magnetic field. Accordingly, information converted into a modulated electrical signal (e.g., the modulated current through the coil) can be used to transfer the information into a magnetic field.
- a magnetometer can be used to monitor the magnetic field. The modulated magnetic field can, therefore, be converted into traditional electrical systems (e.g., using current to transfer information).
- a communications signal can be converted into a magnetic field and a remote receiver (e.g., a magnetometer) can be used to retrieve the communication from the modulated magnetic field.
- a remote receiver e.g., a magnetometer
- a diamond with a nitrogen vacancy (DNV) can be used to measure a magnetic field.
- DNV sensors generally have a quick response to magnetic fields, consume little power, and are accurate.
- Diamonds can be manufactured with nitrogen vacancy (NV) centers in the lattice structure of the diamond. When the NV centers are excited by light, for example green light, and microwave radiation, the NV centers emit light of a different frequency than the excitation light. For example, green light can be used to excite the NV centers, and red light can be emitted from the NV centers.
- the frequency of the light emitted from the NV centers changes. Additionally, when the magnetic field is applied to the NV centers, the frequency of the microwaves at which the NV centers are excited changes.
- a green light or any other suitable color
- NV centers in a diamond are oriented in one of four spin states. Each spin state can be in a positive direction or a negative direction. The NV centers of one spin state do not respond the same to a magnetic field as the NV centers of another spin state. A magnetic field vector has a magnitude and a direction. Depending upon the direction of the magnetic field at the diamond (and the NV centers), some of the NV centers will be excited by the magnetic field more than others based on the spin state of the NV centers.
- Figs. 32 A and 32B are graphs illustrating the frequency response of a DNV sensor in accordance with an illustrative embodiment.
- Figs. 32A and 32B are meant to be illustrative only and not meant to be limiting.
- Figs. 32A and 32B plot the frequency of the microwaves applied to a DNV sensor on the x-axis versus the amount of light of a particular frequency (e.g., red) emitted from the diamond.
- Fig. 32A is the frequency response of the DNV sensor with no magnetic field applied to the diamond
- Fig. 32B is the frequency response of the DNV sensor with a seventy gauss (G) magnetic field applied to the diamond.
- G seventy gauss
- Fig. 32A when no magnetic field is applied to the DNV sensor, there are two notches in the frequency response. With no magnetic field applied to the DNV sensor, the spin states are not resolvable. That is, with no magnetic field, the NV centers with various spin states are equally excited and emit light of the same frequency.
- the two notches shown in Fig. 32A are the result of the positive and negative spin directions.
- the frequency of the two notches is the axial zero field splitting parameter.
- the spin states become resolvable in the frequency response.
- the notches corresponding to the positive and negative directions separate on the frequency response graph.
- Fig. 32B when a magnetic field is applied to the DNV sensor, eight notches appear on the graph.
- the eight notches are four pairs of corresponding notches. For each pair of notches, one notch corresponds to a positive spin state and one notch corresponds to a negative spin state.
- Each pair of notches corresponds to one of the four spin states of the NV centers.
- the amount by which the pairs of notches deviate from the axial zero field splitting parameter is dependent upon how strongly the magnetic field excites the NV centers of the corresponding spin states.
- the magnetic field at a point can be characterized with a magnitude and a direction.
- all of the NV centers will be similarly affected.
- the ratio of the distance from 2.87 GHz of one pair to another will remain the same when the magnitude of the magnetic field is altered.
- each of the notch pairs will move away from 2.87 GHz at a constant rate, although each pair will move at a different rate than the other pairs.
- Fig. 33A is a diagram of NV center spin states in accordance with an illustrative embodiment.
- Fig. 33A conceptually illustrates the four spin states of the NV centers.
- the spin states are labeled NV A, NV B, NV C, and NV D.
- 3301 is a representation of a first magnetic field vector with respect to the spin states.
- Fig. 3302 is a representation of a second magnetic field vector with respect to the spin states.
- Vector 3301 and vector 3302 have the same magnitude, but differ in direction. Accordingly, based on the change in direction, the various spin states will be affected differently depending upon the direction of the spin states.
- Fig. 33B is a graph illustrating the frequency response of a DNV sensor in response to a changed magnetic field in accordance with an illustrative embodiment. The frequency response graph illustrates the frequency response of the DNV sensor from the magnetic field corresponding to vector 3301 and to vector 3302. As shown in Fig.
- the notches corresponding to the NV A and NV D spin states moved closer to the axial zero field splitting parameter from vector 3301 to vector 3302, the negative (e.g., lower frequency notch) notch of the NV C spin state moved away from the axial zero field splitting parameter, the positive (e.g., high frequency notch) of the NV C spin state stayed essentially the same, and the notches corresponding to the NV B spin state increased in frequency (e.g., moved to the right in the graph).
- the DNV sensor can determine the direction of the magnetic field.
- a magnetic field in the direction of NV A can be modulated with a first pattern
- a magnetic field in the direction of NV B can be modulated with a second pattern
- a magnetic field in the direction of NV C can be modulated with a third pattern
- a magnetic field in the direction of NV D can be modulated with a fourth pattern.
- the movement of the notches in the frequency response corresponding to the various spin states can be monitored to determine each of the four patterns.
- the direction of the magnetic field corresponding to the various spin states of a DNV sensor of a receiver may not be known by the transmitter.
- by monitoring at least three of the spin states messages transmitted on two magnetic fields that are orthogonal to one another can be deciphered.
- by monitoring the frequency response of the four spin states messages transmitted on three magnetic fields that are orthogonal to one another can be deciphered.
- two or three independent signals can be transmitted simultaneously to a receiver that receives and deciphers the two or three signals.
- Such embodiments can be a multiple-input multiple-output (MIMO) system.
- MIMO multiple-input multiple-output
- a full rank channel matrix allows MTMO techniques to leverage all degrees of freedom (e.g., three degrees of polarization).
- Using a magnetic field to transmit information circumvents the keyhole effect that propagating a radio frequency field can have.
- Fig. 34 is a block diagram of a magnetic communication system in accordance with an illustrative embodiment.
- An illustrative magnio system 3400 includes input data 3405, a 3410, a transmitter 3445, a modulated magnetic field 3450, a magnetometer 3455, a magnio receiver 3460, and output data 3495.
- additional, fewer, and/or different elements may be used.
- input data 3405 is input into the magnio system 3400, transmitted wirelessly, and the output data 3495 is generated at a location remote from the generation of the input data 3405.
- the input data 3405 and the output data 3495 contain the same information.
- input data 3405 is sent to the magnio transmitter 3410.
- the magnio transmitter 3410 can prepare the information received in the input data 3405 for transmission.
- the magnio transmitter 3410 can encode or encrypt the information in the input data 3405.
- the magnio transmitter 3410 can send the information to the transmitter 3445.
- the transmitter 3445 is configured to transmit the information received from the magnio transmitter 3410 via one or more magnetic fields.
- the transmitter 3445 can be configured to transmit the information on one, two, three, or four magnetic fields. That is, the transmitter 3445 can transmit information via a magnetic field oriented in a first direction, transmit information via a magnetic field oriented in a second direction, transmit information via a magnetic field oriented in a third direction, and/or transmit information via a magnetic field oriented in a fourth direction.
- the magnetic fields can be orthogonal to one another. In alternative embodiments, the magnetic fields are not orthogonal to one another.
- the transmitter 3445 can be any suitable device configured to create a modulated magnetic field.
- the transmitter 3445 can include one or more coils.
- Each coil can be a conductor wound around a central axis.
- the transmitter 3445 can include three coils.
- the central axis of each coil can be orthogonal to the central axis of the other coils.
- the transmitter 3445 generates the modulated magnetic field 3450.
- magnetometer 3455 can detect the modulated magnetic field 3450.
- the magnetometer 3455 can be located remotely from the transmitter 3445. For example, with a current of about ten
- a message can be sent, received, and recovered in full with several meters between the transmitter and receiver and with the magnetometer 3455 inside of a Faraday cage.
- the magnetometer 3455 can be configured to measure the modulated magnetic field 3450 along three or four directions. As discussed above, a magnetometer 3455 using a DNV sensor can measure the magnetic field along four directions associated with four spin states.
- the magnetometer 3455 can transmit information, such as frequency response information, to the magnio receiver 3460.
- the magnio receiver 3460 can analyze the information received from the magnetometer 3455 and decipher the information in the signals. The magnio receiver 3460 can reconstitute the information contained in the input data 3405 to produce the output data 3495.
- the magnio transmitter 3410 includes a data packet generator 3415, an outer encoder 3420, an interleaver 3425, an inner encoder 34340, an interleaver 34345, and an output packet generator 3440.
- a data packet generator 3415 an outer encoder 3420, an interleaver 3425, an inner encoder 34340, an interleaver 34345, and an output packet generator 3440.
- additional, fewer, and/or different elements may be used.
- the various components of the magnio transmitter 310 are illustrated in Fig. 34 as individual components and are meant to be illustrative only. However, in alternative embodiments, the various components may be combined.
- the input data 3405 can be sent to the data packet generator 3415.
- the input data 3405 is a series or stream of bits.
- the data packet generator 3415 can break up the stream of bits into packets of information.
- the packets can be any suitable size.
- the data packet generator 3415 includes appending a header to the packets that includes transmission management information.
- the header can include information used for error detection, such as a checksum. Any suitable header may be used.
- the input data 3405 is not broken into packets.
- the stream of data generated by the data packet generator 3415 can be sent to the outer encoder 3420.
- the outer encoder 3420 can encrypt or encode the stream using any suitable cypher or code. Any suitable type of encryption can be used such as symmetric key encryption.
- the encryption key is stored on memory associated with the magnio transmitter 3410.
- the magnio transmitter 3410 may not include the outer encoder 3420.
- the messages may not be encrypted.
- the outer encoder 3420 separates the stream into multiple channels.
- the outer encoder outer encoder 3420 performs forward error correction (FEC). In some embodiments, the forward error correction dramatically increases the reliability of transmissions for a given power level.
- FEC forward error correction
- the encoded stream from the outer encoder 3420 is sent to the interleaver 3425.
- the interleaver 3425 interleaves bits within each packet of the stream of data. In such an embodiment, each packet has the same bits, but the bits are shuffled according to a predetermined pattern. Any suitable interleaving method can be used.
- the packets are interleaved. In such an embodiment, the packets are shuffled according to a predetermined pattern.
- the magnio transmitter 3410 may not include the interleaver 3425.
- interleaving data can be used to prevent loss of a sequence of data. For example, if a stream of bits are in sequential order and there is a communication loss during a portion of the stream, there is a relatively large gap in the information
- the lost bits are not grouped together but are spread across the sequential bits. In some instances, if the lost bits are spread across the message, error correction can be more successful in determining what the lost bits were supposed to be.
- the interleaved stream from the interleaver 3425 is sent to the inner encoder 3430.
- the inner encoder 3430 can encrypt or encode the stream using any suitable cypher or code. Any suitable type of encryption can be used such as symmetric key encryption.
- the encryption key is stored on memory associated with the magnio transmitter 3410.
- the magnio transmitter 3410 may not include the inner encoder 3430.
- the inner encoder 3430 and the outer encoder 3420 perform different functions.
- the inner encoder 3430 can use a deep convolutional code and can perform most of the forward error correction, and the outer encoder can be used to correct residual errors and can use a different coding technique from the inner encoder 3430 (e.g., a block-parity based encoding technique).
- a different coding technique from the inner encoder 3430 e.g., a block-parity based encoding technique
- the encoded stream from the inner encoder 3430 is sent to the interleaver 3435.
- the interleaver 3435 interleaves bits within each packet of the stream of data.
- each packet has the same bits, but the bits are shuffled according to a predetermined pattern. Any suitable interleaving method can be used.
- the packets are interleaved. In such an
- the packets are shuffled according to a predetermined pattern.
- interleaving the data spreads out burst-like errors across the signal, thereby facilitating the decoding of the message.
- the magnio transmitter 3410 may not include the interleaver 3435.
- the interleaved stream from the interleaver 3435 is sent to the output packet generator 3440.
- the output packet generator 3440 can generate the packets that will be transmitted.
- the output packet generator 3440 may append a header to the packets that includes transmission management information.
- the header can include information used for error detection, such as a checksum. Any suitable header may be used.
- the output packet generator 3440 appends a synchronization sequence to each of the packets.
- a synchronization sequence can be added to the beginning of each packet.
- the packets can be transmitted on multiple channels. In such an embodiment, each channel is associated with a unique synchronization sequence.
- the synchronization sequence can be used to decipher the channels from one another, as is discussed in greater detail below with regard to the magnio receiver 3460.
- the output packet generator 3440 modulates the waveform to be transmitted. Any suitable modulation can be used. In an illustrative
- the waveform is modulated digitally.
- minimum shift keying can be used to modulate the waveform.
- non-differential minimum shift key can be used.
- the waveform has a continuous phase. That is, the waveform does not have phase discontinuities.
- the waveform is sinusoidal in nature.
- the modulated waveform is sent to the transmitter 3445.
- multiple modulated waveforms are sent to the transmitter 3445.
- two, three, or four signals can be transmitted simultaneously via magnetic fields with different directions.
- three modulated waveforms are sent to the transmitter 3445.
- Each of the waveforms can be used to modulate a magnetic field, and each of the magnetic fields can be orthogonal to one another.
- the transmitter 3445 can use the received waveforms to produce the modulated magnetic field 3450.
- the modulated magnetic field 3450 can be a combination of multiple magnetic fields of different directions.
- the frequency used to modulate the modulated magnetic field 3450 can be any suitable frequency.
- the carrier frequency of the modulated magnetic field 3450 can be 10 kHz.
- the carrier frequency of the modulated magnetic field 3450 can be less than or greater than 10 kHz.
- the carrier frequency can be modulated to plus or minus the carrier frequency. That is, using the example in which the carrier frequency is 10 kHz, the carrier frequency can be modulated down to 0 Hz and up to 20 kHz. In alternative embodiments, any suitable frequency band can be used.
- Figs. 35 A and 35B show the strength of a magnetic field versus frequency in accordance with an illustrative embodiment.
- Figs. 35 A and 35B are meant to be illustrative only and not meant to be limiting.
- the magnetic spectrum is relatively noisy.
- the noise over a large band e.g., 0-200 kHz
- Fig. 35B illustrates the noise over a smaller band (e.g., 1-3 kHz).
- the noise over a smaller band is relatively low.
- modulating the magnetic field across a smaller band of frequencies can be less noisy and more effective.
- the magnio transmitter 3410 can monitor the magnetic field and determine a suitable frequency to modulate the magnetic fields to reduce noise. That is, the magnio transmitter 3410 can find a frequency that has a high signal to noise ratio. In an illustrative embodiment, the magnio transmitter 3410 determines a frequency band that has noise that is below a predetermined threshold.
- the magnio receiver 3460 includes the demodulator 3465, the de-interleaver 3470, the soft inner decoder 3475, the de-interleaver 3480, the outer decoder 3485, and the output data generator 3490.
- the magnio receiver 3460 can include the magnetometer 3455 in some embodiments.
- the various components of the magnio receiver 3460 are illustrated in Fig. 34 as individual components and are meant to be illustrative only. However, in alternative embodiments, the various components may be combined.
- magnio receiver 3460 can be implemented using hardware and/or software.
- the magnetometer 3455 is configured to measure the modulated magnetic field 3450.
- the magnetometer 3455 includes a DNV sensor.
- the magnetometer 3455 can monitor the modulated magnetic field 3450 in up to four directions.
- the magnetometer 3455 can be configured to measure the magnetometer 3455 in one or more of four directions that are tetrahedronally arranged.
- the magnetometer 3455 can monitor n + 1 directions where n is the number of channels that the transmitter 3445 transmits on.
- the transmitter 3445 can transmit on three channels, and the magnetometer 3455 can monitor four directions.
- the transmitter 3445 can transmit via the same number of channels (e.g., four) as directions that the magnetometer 3455 monitors.
- the magnetometer 3455 can send information regarding the modulated magnetic field 3450 to the demodulator 3465.
- the demodulator 3465 can analyze the received
- the demodulator 3465 can determine the directions of the channels that the transmitter 3445 transmitted on.
- the transmitter 3445 can transmit multiple streams of data, and each stream of data is transmitted on one channel.
- Each of the streams of data can be preceded by a unique synchronization sequence.
- the synchronization sequence includes 1023 bits. In alternative embodiments, the synchronization sequence includes more than or fewer than 1023 bits.
- Each of the streams can be transmitted simultaneously such that each of the channels are time-aligned with one another.
- the demodulator 3465 can monitor the magnetic field in multiple directions simultaneously.
- the demodulator 3465 can determine the directions corresponding to the channels of the transmitter 3445. When the streams of synchronization sequences are time-aligned, the demodulator 3465 can monitor the modulated magnetic field 3450 to determine how the multiple channels mixed. Once the demodulator 3465 determines how the various channels are mixed, the channels can be demodulated.
- the transmitter 3445 transmits on three channels, with each channel corresponding to an orthogonal direction. Each channel is used to transmit a stream of information.
- the channels are named “channel A,” “channel B,” and “channel C.”
- the magnetometer 3455 monitors the modulated magnetic field 3450 in four directions.
- the demodulator 3465 can monitor for three signals in orthogonal directions.
- the signals can be named “signal 1,” “signal 2,” and “signal 3.”
- Each of the signals can contain a unique, predetermined synchronization sequence.
- the demodulator 3465 can monitor the modulated magnetic field 3450 for the signals to be transmitted on the channels. There is a finite number of possible combinations that the signals can be received at the magnetometer 3455.
- signal 1 can be transmitted in a direction corresponding to channel A
- signal 2 can be transmitted in a direction corresponding to channel B
- signal 3 can be transmitted in a direction corresponding to channel C
- signal 2 can be transmitted in a direction corresponding to channel A
- signal 3 can be transmitted in a direction corresponding to channel B
- signal 1 can be transmitted in a direction
- magnetometer 3455 can be known by the demodulator 3465.
- the demodulator 3465 can monitor the output of the magnetometer 3455 for each of the possible combinations.
- the demodulator 3465 can monitor for additional data in directions associated with the recognized combination.
- the transmitter 3445 transmits on two channels, and the magnetometer 3455 monitors the modulated magnetic field 3450 in three directions.
- the demodulated signals (e.g., the received streams of data from each of the channels) is sent to the de-interleaver 3470.
- the de-interleaver 3470 can undo the interleaving of the interleaver 3435.
- the de-interleaved streams of data can be sent to the soft inner decoder 3475, which can undo the encoding of the inner encoder 3430.
- Any suitable decoding method can be used.
- the inner encoder 3430 uses a three- way, soft-decision turbo decoding function.
- a two-way, soft- decision turbo decoding function may be used.
- the expected cluster positions for signal levels are learned by the magnio receiver 3460 during the synchronization portion of the transmission.
- distances from all possible signal clusters to the observed signal value are computed for every bit position.
- the bits in each bit position are determined by combining the distances with state transition probabilities to find the best path through a "trellis.” The path through the trellis can be used to determine the most likely bits that were communicated.
- the decoded stream can be transmitted to the de-interleaver 3480.
- the de- interleaver 3480 can undo the interleaving of the interleaver 3425.
- the de-interleaved stream can be sent to the outer decoder 3485.
- the outer decoder 3485 undoes the encoding of the outer encoder 3420.
- the unencoded stream of information can be sent to the output data generator 3490.
- the output data generator 3490 undoes the packet generation of data packet generator 3415 to produce the output data 3495.
- Fig. 36 is a block diagram of a computing device in accordance with an illustrative embodiment.
- An illustrative computing device 3600 includes a memory 3610, a processor 3605, a transceiver 3615, a user interface 3620, and a power source 3625. In alternative embodiments, additional, fewer, and/or different elements may be used.
- the computing device 3600 can be any suitable device described herein.
- the computing device 3600 can be a desktop computer, a laptop computer, a smartphone, a specialized computing device, etc.
- the computing device 3600 can be used to implement one or more of the methods described herein.
- the memory 3610 is an electronic holding place or storage for information so that the information can be accessed by the processor 3605.
- the memory 3610 can include, but is not limited to, any type of random access memory (RAM), any type of read only memory (ROM), any type of flash memory, etc. such as magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks (e.g., compact disk (CD), digital versatile disk (DVD), etc.), smart cards, flash memory devices, etc.
- the computing device 3600 may have one or more computer-readable media that use the same or a different memory media technology.
- the computing device 3600 may have one or more drives that support the loading of a memory medium such as a CD, a DVD, a flash memory card, etc.
- the processor 3605 executes instructions.
- the instructions may be carried out by a special purpose computer, logic circuits, or hardware circuits.
- the processor 3605 may be implemented in hardware, firmware, software, or any combination thereof.
- execution is, for example, the process of running an application or the carrying out of the operation called for by an instruction.
- the instructions may be written using one or more programming language, scripting language, assembly language, etc.
- the processor 3605 executes an instruction, meaning that it performs the operations called for by that instruction.
- the processor 3605 operably couples with the user interface 3620, the transceiver 3615, the memory 3610, etc. to receive, to send, and to process information and to control the operations of the computing device 3600.
- the processor 3605 may retrieve a set of instructions from a permanent memory device such as a ROM device and copy the instructions in an executable form to a temporary memory device that is generally some form of RAM.
- a permanent memory device such as a ROM device
- An illustrative computing device 3600 may include a plurality of processors that use the same or a different processing technology.
- the instructions may be stored in memory 3610.
- the transceiver 3615 is configured to receive and/or transmit information.
- the transceiver 3615 communicates information via a wired connection, such as an Ethernet connection, one or more twisted pair wires, coaxial cables, fiber optic cables, etc.
- the transceiver 3615 communicates information via a wireless connection using microwaves, infrared waves, radio waves, spread spectrum technologies, satellites, etc.
- the transceiver 3615 can be configured to communicate with another device using cellular networks, local area networks, wide area networks, the Internet, etc.
- one or more of the elements of the computing device 3600 communicate via wired or wireless communications.
- the transceiver 3615 provides an interface for presenting information from the computing device 3600 to external systems, users, or memory.
- the transceiver 3615 may include an interface to a display, a printer, a speaker, etc.
- the transceiver 3615 may also include alarm/indicator lights, a network interface, a disk drive, a computer memory device, etc.
- the transceiver 3615 can receive information from external systems, users, memory, etc.
- the user interface 3620 is configured to receive and/or provide information from/to a user.
- the user interface 3620 can be any suitable user interface.
- the user interface 3620 can be an interface for receiving user input and/or machine instructions for entry into the computing device 3600.
- the user interface 3620 may use various input technologies including, but not limited to, a keyboard, a stylus and/or touch screen, a mouse, a track ball, a keypad, a microphone, voice recognition, motion recognition, disk drives, remote controllers, input ports, one or more buttons, dials, joysticks, etc. to allow an external source, such as a user, to enter information into the computing device 3600.
- the user interface 3620 can be used to navigate menus, adjust options, adjust settings, adjust display, etc.
- the user interface 3620 can be configured to provide an interface for presenting information from the computing device 3600 to external systems, users, memory, etc.
- the user interface 3620 can include an interface for a display, a printer, a speaker, alarm/indicator lights, a network interface, a disk drive, a computer memory device, etc.
- the user interface 3620 can include a color display, a cathode-ray tube (CRT), a liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, etc.
- the power source 36236 is configured to provide electrical power to one or more elements of the computing device 3600.
- the power source 3625 includes an alternating power source, such as available line voltage (e.g., 120 Volts alternating current at 60 Hertz in the United States).
- the power source 3625 can include one or more transformers, rectifiers, etc. to convert electrical power into power useable by the one or more elements of the computing device 3600, such as 1.5 Volts, 8 Volts, 12 Volts, 24 Volts, etc.
- the power source 3625 can include one or more batteries.
- the NV center magnetic sensor that operates as described above is capable of resolving a magnetic field to an unsigned vector.
- the symmetry of the fluorescence spectra makes the assignment of a sign to the calculated magnetic field vector unreliable.
- the natural ambiguity introduced to the magnetic field sensor is undesirable in some applications, such as magnetic field based direction sensing.
- the sign of the magnetic field vector may be determine by whether the total magnetic field, cumulative of the bias field and the signal of interest, increases or decreases. If the magnetic sensor is employed to detect submarines from a surface ship, assigning the calculated magnetic field vector a sign that would place a detected submarine above the surface ship would be nonsensical. Alternatively, where the sign of the vector is not important a sign can be arbitrarily assigned to the unsigned vector.
- the method of determining the signed magnetic field vector may be performed with a DNV magnetic field sensor of the type shown in FIG. 6 and described above.
- the recovery of the vector may be achieved as described in co-pending U.S.
- fluorescence intensity with the application of RF excitation may be employed to calculate an "equilibration time.”
- An “equilibration time” as utilized herein refers to the time between the start of an RF excitation pulse and when a predetermined percentage of the equilibrium fluorescence intensity is achieved. The predetermined amount of the equilibrium fluorescence at which the
- equilibration time is calculated may be about 20% to about 80% of the equilibrium fluorescence, such as about 30%, 40%, 50%, 60%, or 70% of the equilibrium fluorescence.
- the equilibration time as shown in FIGS. 38, 40 and 41 is actually a decay time, as the fluorescence intensity is actually decreasing in the presence of the RF excitation, but has been inverted for the sake of clarity.
- the fluorescence intensity of the DNV material varies with the application of a pulsed RF excitation source.
- the RF pulse When the RF pulse is in the "on" state, the electrons decay through a non-fluorescent path and a relatively dark equilibrium fluorescence is achieved.
- the absence of the RF excitation when the pulse is in the "off state, results in a relatively bright equilibrium fluorescence.
- the transition between the two fluorescence equilibrium states is not instantaneous, and the measurement of the equilibration time at a predetermined value of fluorescence intensity provides a repeatable indication of the relaxation time for the electrons at the RF excitation frequency.
- the peak which corresponds to the higher energy state may be identified.
- the higher energy peak provides a reliable indication of the sign of the magnetic field vector.
- the Lorentzian pair of the fluorescence spectra which are located furthest from the zero splitting energy may be selected to calculate the equilibration time. These peaks include the least signal interference and noise, allowing a more reliable measurement. The preferred
- FIG. 40 A plot of the fluorescence intensity for a single RF pulse as a function of time is shown in FIG. 40.
- the frequency of the pulsed RF excitation is selected to be the maximum value for each peak in the Lorentzian pair.
- the other conditions for the measurement of an equilibration time for each peak in the Lorentzian pair are held constant.
- the peaks of the Lorentzian pair have an equilibration time when calculated to 60% of the equilibrium intensity value that is distinguishable.
- the RF pulse duration may be set such that the desired percentage of the equilibrium fluorescence intensity is achieved for each "on" portion of the pulse, and the full “bright” equilibrium intensity is achieved during the "off portion of the pulse.
- the equilibrium fluorescence intensity under the application of the RF excitation may be set by any appropriate method.
- the RF excitation may be maintained until the intensity becomes constant, and the constant intensity may be considered the equilibrium intensity value utilized to calculate the equilibration time.
- the equilibrium intensity may be set to the intensity at the end of an RF excitation pulse.
- a decay constant may be calculated based on the measured fluorescence intensity and a theoretical data fit employed to determine the equilibrium intensity value.
- the signs of the peaks in the other Lorentzian pairs in the fluorescence spectra of the DNV material as a function of RF frequency may then be assigned, and the signed magnetic field vector calculated.
- the method of determining a sign of a magnetic field vector with a DNV magnetic sensor described herein may be performed with the DNV magnetic field sensor shown in FIG. 6. No additional hardware is required.
- the controller of the magnetic field sensor may be programmed to determine the location of peaks in a fluorescence spectra of a DNV material as a function of RF frequency.
- the equilibration time for the peaks of a Lorentzian pair located the furthest from the zero field energy may then be calculated.
- the controller may be programmed to provide a pulsed RF excitation energy by controlling a RF excitation source and also control an optical excitation source to excite the DNV material with continuous wave optical excitation.
- the resulting optical signal received at the optical detector may be analyzed by the controller to determine the equilibration time associated with each peak in the manner described above.
- the controller may be programmed to assign a sign to each peak based on the measured equilibration time.
- the method of assigning a sign to a magnetic field vector described above may also be applied to magnetic field sensors based on magneto-optical defect center materials other than DNV.
- the DNV magnetic field sensor described herein that produces a signed magnetic field vector may be especially useful in applications in which the direction of a measured magnetic field is important.
- the DNV magnetic field sensor may be employed in magnetic field based navigation or positioning systems.
- FIGS. 43 A and 43B are diagrams illustrating hydrophone systems in accordance with illustrative embodiments.
- An illustrative system 4300 includes a hull 4305 and a magnetometer 4310.
- an acoustic transmitter can be used to generate one or more acoustic signals.
- the system 4300 can be used as a passive sonar system.
- the system 4300 can be used to detect sounds created by something other than a transmitter (e.g., a ship, a boat, an engine, a mammal, ice movement, etc.).
- the hull 4305 is the hull of a vessel such as a ship or a boat.
- the hull 4305 can be any suitable material, such as steel or painted steel.
- the magnetometer 4310 is installed in alternative structures such as a bulk head or a buoy.
- the magnetometer 4310 can be located within the 4305. In the embodiment, the magnetometer 4310 is located at the outer surface of the hull 4305. In alternative embodiments, the magnetometer 4310 can be located at any suitable location. For example, magnetometer 4310 can be located near the middle of the hull 4305, at an inner surface of the hull 4305, or on an inner or outer surface of the hull 4305.
- the magnetometer 4310 is a magnetometer with a diamond with NV centers. In an illustrative embodiment, the magnetometer 4310 has a sensitivity of about 0.1 micro Tesla. In alternative embodiments, the magnetometer 4310 has a sensitivity of greater than or less than 0.1 micro Tesla.
- sound waves 4315 propagate through a fluid with dissolved ions, such as sea water.
- the ions create a magnetic field.
- the ions move within the magnetic field of the
- the ions create a magnetic field that is detectable by the magnetometer 4310.
- a magnetic field source such as a permanent magnet or an electromagnet can be used. The movement of the ions with respect to the source of the magnetic field (e.g., the Earth) creates the magnetic field detectable by the magnetometer 4310.
- the sound waves 4315 travel through sea water.
- the density of dissolved ions in the fluid near the magnetometer 4310 depends on the location in the sea that the magnetometer 4310 is. For example, some locations have a lower density of dissolved ions than others. The higher the density of the dissolved ions, the greater the combined magnetic field created by the movement of the ions. In an illustrative embodiment, the strength of the combined magnetic field can be used to determine the density of the dissolved ions (e.g., the salinity of the sea water).
- the hull 4305 is the hull of a ship that travels through the sea water.
- the movement of the ions relative to the source magnetic field can be measured by the magnetometer 4310.
- the magnetometer 4310 can be used to detect and measure the sound waves 4315 as the magnetometer 4310 moves through the sea water and as the magnetometer 4310 is stationary in the sea water.
- the magnetometer 4310 can measure the magnetic field caused by the moving ions in any suitable direction.
- the magnetometer 4310 can measure the magnetic field caused by the movement of the ions when the sound waves 4315 is perpendicular to the hull 4305 or any other suitable angle.
- the magnetometer 4310 can measure the magnetic field caused by the movement of the ions when the sound waves 4315 is perpendicular to the hull 4305 or any other suitable angle.
- magnetometer 4310 measures the magnetic field caused by the movement of ions caused by sound waves 4315 that are parallel to the surface of the hull 4305.
- An illustrative system 4350 includes the hull 4305 and an array of magnetometers 4355.
- additional, fewer, and/or different elements can be used.
- FIG. 43B illustrates four magnetometers 4355 are used.
- the system 4350 can include fewer than four magnetometers 4355 or more than magnetometers 4355.
- the array of the magnetometers 4355 can be used to increase the sensitivity of the hydrophone. For example, by using multiple magnetometers 4355, the hydrophone has multiple measurement points.
- the array of magnetometers 4355 can be arranged in any suitable manner.
- the magnetometers 4355 can be arranged in a line. In another example, the
- magnetometers 4355 can be arranged in a circle, in concentric circles, in a grid, etc.
- the array of magnetometers 4355 can be uniformly arranged (e.g., the same distance from one another) or non-uniformly arranged.
- the array of magnetometers 4355 can be used to determine the direction from which the sound waves 4315 travel.
- the sound waves 4315 can cause ions near one the bottom magnetometer of the magnetometers 4355 of the embodiment illustrated in the system 4350 to create a magnetic field before the sound waves 4315 cause ions near the top magnetometer of the magnetometers 4355.
- it can be determined that the sound waves 4315 travels from the bottom to the top of FIG. 43B.
- the magnetometer 4310 or the magnetometers 4355 can determine the angle that the sound waves 4315 travel relative to the magnetometer 4310 based on the direction of the magnetic field caused by the movement of the ions.
- individual magnetometers of the magnetometers 4355 can each be configured to measure the magnetic field of the ions in a different direction. Principles of beamforming can be used to determine the direction of the magnetic field.
- any suitable magnetometer 4310 or magnetometers 4355 can be used to determine the direction of the magnetic field and/or the direction of the acoustic signal.
- DNV diamond nitrogen-vacancy
- the characteristic magnetic signature of human infrastructure provides context for navigation.
- power lines which have characteristic magnetic signatures, can serve as roads and highways for mobile platforms (e.g., UASs). Travel in relatively close proximity to power lines may allow stealthy transit, may provide the potential for powering the mobile platform itself, and may permit point-to-point navigation both over long distances and local routes.
- Some implementations can include one or more magnetic sensors, a magnetic navigation database, and a feedback loop that controls the UAS position and orientation.
- DNV magnetic sensors and related systems and methods may provide high sensitivity magnetic field measurements.
- the DNV magnetic systems and methods can also be low cost, space, weight, and power (C-SWAP) and benefit from a fast settling time.
- C-SWAP low cost, space, weight, and power
- DNV-based magnetic systems and methods can be approximately 100 times smaller than conventional systems and can have a reaction time that that is approximately 100,000 times faster than other systems.
- FIG. 44 is a diagram illustrating an example of UAS 4402 navigation along power lines 4404, 4406, and 4408, according to some implementations of the subject technology.
- the UAS 4402 can exploit the distinct magnetic signatures of power lines for navigation such that the power lines can serve as roads and highways for the UAS 4402 without the need for detailed a priori knowledge of the route magnetic characteristics.
- a ratio of signal strength of two magnetic sensors, A and B (4410 and 4412 in Figure 44), attached to wings of the UAS 4402 varies as a function of distance, x, from a center line of an example three-line power transmission line structure 4404, 4406, and 4408.
- This field is an illustration of the strength of the magnetic field measured by one or more magnetic sensors in the UAS.
- the peak of the field 4508 corresponds to the UAS 4402 being above the location of the middle line 4406.
- the sensors would read strengths corresponding to points 4502 and 4504.
- a computing system on the UAS or remote from the UAS can calculate combined readings. Not all of the depicted components may be required, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made, and additional components, different components, or fewer components may be provided.
- a vehicle such as a UAS
- a vehicle can include one or more navigation sensors, such as DNV sensors.
- the vehicle's mission could be to travel to an initial destination and possibly return to a final destination.
- Known navigation systems can be used to navigate the vehicle to an intermediate location.
- a UAS can fly using GPS and/or human controlled navigation to the intermediate location.
- the UAS can then begin looking for the magnetic signature of a power source, such as power lines. To find a power line, the UAS can continually take measurements using the DNV sensors.
- the UAS can fly in a circle, straight line, curved pattern, etc. and monitor the recorded magnetic field.
- the magnetic field can be compared to known characteristics of power lines to identify if a power line is in the vicinity of the UAS.
- the measured magnetic field can be compared with known magnetic field characteristics of power lines to identify the power line that is generating the measured magnetic field.
- information regarding the electrical infrastructure can be used in combination with the measured magnetic field to identify the current source.
- a database regarding magnetic measurements from the area that were previously taken and recorded can be used to compare the current readings to help determine the UAS's location.
- the UAS positions itself at a known elevation and position relative to the power line. For example, as the UAS flies over a power line, the magnetic field will reach a maximum value and then begin to decrease as the UAS moves away from the power line. After one sweep of a known distance, the UAS can return to where the magnetic field was the strongest. Based upon known characteristics of power lines and the magnetic readings, the UAS can determine the type of power line.
- the UAS can change its elevation until the magnetic field is a known value that corresponds with an elevation above the identified power line. For example, as shown in Figure 6, a magnetic field strength can be used to determine an elevation above the current source.
- the UAS can also use the measured magnetic field to position itself offset from directly above the power line. For example, once the UAS is positioned above the current source, the UAS can move laterally to an offset position from the current source. For example, the UAS can move to be 10 kilometers to the left or right of the current source.
- the UAS can be programmed, via a computer 306, with a flight path. In some implementations, once the UAS establishes its position, the UAS can use a flight path to reach its destination. In some implementations, the magnetic field generated by the transmission line is perpendicular to the transmission line. In some implementations, the vehicle will fly
- the UAS can follow the detected power line to its destination. In this example, the UAS will attempt to keep the detected magnetic field to be close to the original magnetic field value. To do this, the UAS can change elevation or move laterally to stay in its position relative to the power line. For example, a power line that is rising in elevation would cause the detected magnetic field to increase in strength as the distance between the UAS and power line decreased.
- the navigation system of the UAS can detect this increased magnetic strength and increase the elevation of the UAS.
- on board instruments can provide an indication of the elevation of the UAS. The navigation system can also move the UAS laterally to the keep the UAS in the proper position relative to the power lines.
- the magnetic field can become weaker or stronger, as the UAS drifts from its position of the transmission line. As the change in the magnetic field is detected, the navigation system can make the appropriate correction. For a UAS that only has a single DNV sensor, when the magnetic field had decreased by more than a predetermined amount the navigation system can make corrections. For example, the UAS can have an error budget such that the UAS will attempt to correct its course if the measured error is greater than the error budget. If the magnetic field has decreased, the navigation system can instruct the UAS to move to the left. The navigation system can continually monitor the magnetic field to see if moving to the left corrected the error.
- the navigation system can instruct the UAS to fly to the right to its original position relative to the current source and then move further to the right. If the magnetic field decreased in strength, the navigation system can deduce that the UAS needs to decrease its altitude to increase the magnetic field. In this example, the UAS would originally be flying directly over the current source, but the distance between the current source and the UAS has increased due to the current source being at a lower elevation. Using this feedback loop of the magnetic field, the navigation system can keep the UAS centered or at an offset of the current source. The same analysis can be done when the magnetic field increases in strength. The navigation can maneuver until the measured magnetic field is within the proper range such that the UAS in within the flight path.
- the UAS can also use the vector measurements from one or more DNV sensors to determine course corrections.
- the readings from the DNV sensor are vectors that indicate the direction of the sensed magnetic field.
- the vector can provide an indication of the direction the UAS should move to correct its course. For example, the strength of the magnetic field can be reduced by a threshold amount from its ideal location.
- the magnetic vector of this field can be used to indicate the direction the UAS should correct to increase the strength of the magnetic field. In other words, the magnetic field indicates the direction of the field and the UAS can use this direction to determine the correct direction needed to increase the strength of the magnetic field, which could correct the UAS flight path to be back over the transmission wire.
- the navigation system can determine if the UAS needs to correct its course by moving left, right, up, or down. For example, if both DNV sensors are reading a stronger field, the navigation system can direct the UAS to increase its altitude. As another example if the left sensor is stronger than expected but the right sensor is weaker than expected, the navigation system can move the UAS to the left.
- a recent history of readings can also be used by the navigation system to identify how to correct the UAS course. For example, if the right sensor had a brief increase in strength and then a decrease, while the left sensor had a decrease, the navigation system can determine that the UAS has moved to far to the left of the flight path and could correct the position of the UAS accordingly.
- FIG. 46 illustrates a high-level block diagram of an example UAS navigation system 4600, according to some implementations of the subject technology.
- the UAS navigation system of the subject technology includes a number of DNV sensors 4602a, 4602b, and 4602c, a navigation database 4604, and a feedback loop that controls the UAS position and orientation.
- a vehicle can contain a navigation control that is used to navigate the vehicle. For example, the navigation control can change the vehicle's direction, elevation, speed, etc.
- the DNV magnetic sensors 4602a-4602c have high sensitivity to magnetic fields, low C-SWAP and a fast settling time.
- the DNV magnetic field measurements allow the UAS to align itself with the power lines, via its characteristic magnetic field signature, and to rapidly move along power-line routes. Not all of the depicted components may be required, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made, and additional components, different components, or fewer components may be provided.
- FIG. 47 illustrates an example of a power line infrastructure. It is known that widespread power line infrastructures, such as shown in FIG. 47, connect cities, critical power system elements, homes and businesses.
- the infrastructure may include overhead and buried power distribution lines, transmission lines, railway catenary and 3rd rail power lines and underwater cables.
- Each element has a unique electro-magnetic and spatial signature. It is understood that, unlike electric fields, the magnetic signature is minimally impacted by man- made structures and electrical shielding. It is understood that specific elements of the
- Figures 48A and 48B illustrate examples of magnetic field distribution for overhead power lines and underground power cables. Both above-ground and buried power cables emit magnetic fields, which unlike electrical fields are not easily blocked or shielded. Natural Earth and other man-made magnetic field sources can provide rough values of absolute location.
- the sensitive magnetic sensors described here can locate strong man-made magnetic sources, such as power lines, at substantial distances. As the UAS moves, the measurements can be used to reveal the spatial structure of the magnetic source (point source, line source, etc.) and thus identify the power line as such. In addition, once detected the UAS can guide itself to the power line via its magnetic strength. Once the power line is located its structure is determined, and the power line route is followed and its characteristics are compared to magnetic way points to determine absolute location. Fixed power lines can provide precision location reference as the location and relative position of poles and towers are known. A compact on-board database can provide reference signatures and location data for waypoints. Not all of the depicted components may be required, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made, and additional components, different components, or fewer components may be provided.
- Figure 49 illustrates examples of magnetic field strength of power lines as a function of distance from the centerline showing that even low current distribution lines can be detected to distances in excess of 10 km.
- DNV sensors provide 0.01 uT sensitivity (le-10 T), and modeling results indicates that high current transmission line (e.g. with 1000 A - 4000 A) can be detected over many tens of km.
- high current transmission line e.g. with 1000 A - 4000 A
- These strong magnetic sources allow the UAS to guide itself to the power lines where it can then align itself using localized relative field strength and the characteristic patterns of the power-line configuration as described below.
- Figure 50 illustrates an example of a UAS 5002 equipped with DNV sensors 5004 and 5006.
- Figure 51 is a plot of a measured differential magnetic field sensed by the DNV sensors when in close proximity of the power lines. While power line detection can be performed with only a single DNV sensor precision alignment for complex wire configurations can be achieved using multiple arrayed sensors. For example, the differential signal can eliminate the influence of diurnal and seasonal variations in field strength. Not all of the depicted components may be required, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made, and additional components, different components, or fewer components may be provided.
- a vehicle can also be used to inspect power transmission lines, power lines, and power utility equipment.
- a vehicle can include one or more magnetic sensors, a magnetic waypoint database, and an interface to UAS flight control.
- the subject technology may leverage high sensitivity to magnetic fields of DNV magnetic sensors for magnetic field measurements.
- the DNV magnetic sensor can also be low cost, space, weight, and power (C-SWAP) and benefit from a fast settling time.
- C-SWAP low cost, space, weight, and power
- the DNV magnetic field measurements allow UASs to align themselves with the power lines, and to rapidly move along power-line routes and navigate in poor visibility conditions and/or in GPS- denied environments. It is understood that DNV-based magnetic sensors are approximately 100 times smaller than conventional magnetic sensors and have a reaction time that that is approximately 100,000 times faster than sensors with similar sensitivity such as the EMDEX LLC Snap handheld magnetic field survey meter.
- power lines can be efficiently surveyed via small unmanned aerial vehicles (UAVs) on a routine basis over long distance, which can identify emerging problems and issues through automated field anomaly identification.
- UAVs small unmanned aerial vehicles
- a land based vehicle or submersible can be used to inspect power lines. Human inspectors are not required to perform the initial inspections. The inspections of the subject technology are quantitative, and thus are not subject to human interpretation as remote video solutions may be.
- Figure 52 illustrates an example of a measured magnetic field distribution for power lines 904 and power lines with anomalies 902 according to some implementations.
- the inspection method of the subject technology is a high-speed anomaly mapping technique that can be employed for single and multi-wire transmission systems.
- the subject solution can take advantage of existing software modeling tools for analyzing the inspection data.
- the data form a normal set of power lines may be used as a comparison reference for data resulting from inspection of other power lines (e.g., with anomalies or defects).
- Damage to wires and support structure alters the nominal magnetic field characteristics and is detected by comparison with nominal magnetic field characteristics of the normal set of power lines. It is understood that the magnetic field measurement is minimally impacted by other structures such as buildings, trees, and the like. Accordingly, the measured magnetic field can be compared to the data from the normal set of power lines and the measured magnetic field's magnitude and if different by a predetermined threshold the existence of the anomaly can be indicated. In addition, the vector reading between the difference data can also be compared and used to determine the existence of anomaly.
- a vehicle may need to avoid objects that are in their navigation path. For example, a ground vehicle may need to maneuver around people or objects, or a flying vehicle may need to avoid a building or power line equipment. In these
- the vehicle can be equipment with sensors that are used to locate the obstacles that are to be avoided.
- Systems such as a camera system, focal point array, radar, acoustic sensors, etc., can be used to identify obstacles in the vehicles path.
- the navigation system can then identify a course correction to avoid the identified obstacles.
- Measuring the quantum energy levels of a diamond nitrogen vacancy (DNV) material may provide information regarding the quality of the material, such as the suitability of the DNV material for use in a magnetic field sensor.
- the impurity content, lattice strain, and nitrogen vacancy (NV) concentration of the DNV material impact the quantum energy levels of the DNV material.
- measuring the quantum energy levels of the DNV material provides information regarding the impurity content, lattice strain, and NV content of the DNV material.
- the characterization of DNV materials may be achieved by measuring a number of parameters associated with the fluorescence behavior described above.
- DNV metrology may be carried out through the measurement of a number of parameters associated with the Zero-Field-Splitting (ZFS) of the DNV dipolar coupling and the Hyperfine coupling of the DNV material.
- ZFS Zero-Field-Splitting
- the measurement of these parameters allows assessment of the impurities in the diamond. Examples of the impurities are lattice dislocations, broken bonds, and other elements beyond 14-Nitrogen. Measurement of these parameters further affords insight as to the concentration of DNV centers. Impurities and excess DNV concentration directly impact the hyperfine resolution.
- Lattice dislocations and crystal strain can affect the ZFS level by introducing an asymmetry that breaks the degeneracy of the state.
- the assessment pursued by the measurements maybe conducted in a reasonably short period of time, and provides sufficient depth of information such that the quality of the DNV material may be confirmed.
- Such a quality assurance (QA) assessment is desirable when evaluating and comparing various DNV suppliers or when confirming the properties of DNV materials.
- the characterization of a DNV sample includes measurements of the quantum nature of the sample.
- the ZFS parameters are derived from the Hamiltonian (Energy Equation) to a specific precision for the DNV system.
- the Hamiltonian can be expressed as:
- the Zeeman term describes the interaction of the spin centers with an external magnetic field. Measurements of the terms D, A, and Q provide significant insight into the repeatability and quality of the DNV manufacturing process.
- FIG. 53 A schematic depiction of the energy levels of the DNV Hamiltonian is shown in FIG. 53.
- the terms D, A, and Q provide insight into the repeatability and quality of the DNV manufacturing process because the terms D, A, and Q from the Hamiltonian equation are measurable quantities that determine the energy levels of the DNV system.
- the D tensor may be expressed as:
- FIG. 54 is a diagram illustrating an example of a DNV fluorescence signal as described above without an applied bias field (0 gauss bias).
- the parameters E and D are derived from the measured frequencies v 1 and v 2 of the DNV optical signal of FIG. 54 according to following equations:
- the measured frequencies v 1 and v 2 of the DNV signal may be considered to be the location of lorentzian peaks in the DNV optical signal, as shown in FIG. 54.
- a continuous wave (CW) laser pumping and a continuous-wave (CW) radio-frequency (RF) can be employed for excitation of the DNV sample, in the absence of an applied bias magnetic field.
- the RF signal can be swept from ⁇ 2.8 to 2.95 GHz to observe the fluorescence signal shown in FIG. 54.
- FIGS. 55 and 56 are diagrams illustrating DNV florescence signals for a high quality DNV sample and a low quality DNV sample, respectively, under a 1 Gauss magnetic bias field.
- the locations of the hyperfine levels may indicate the presence of isotopes of 15 N, 14 N, and 13 C in the DNV sample.
- the natural isotope 14 N has known levels of approximately +2.5 MHz, 0 MHz, and -2.5 MHz relative to the dipolar energy levels, as shown in FIG. 55.
- the ability to resolve hyperfine levels at room temperature, as seen in FIG. 55 indicates a high purity of the DNV sample.
- a high purity DNV sample may allow hyperfine levels to be resolved without cooling the DNV sample to cryogenic
- a small bias magnetic field is applied to the DNV sample along with continuous wave (CW) laser pumping and a CW RF excitation.
- the RF power may be beneficially adjusted to the lowest setting possible while still obtaining measurable resonances.
- the RF signal can be swept from -2.8 to 2.95 GHz to observe the fluorescence signal shown in FIG. 55, which utilized a 1 gauss bias magnetic field.
- the bias magnetic field applied to identify and measure the hyperfine splitting may be any appropriate bias field, such as at least about 1 gauss, or about 30 gauss.
- FIG. 6 is a schematic of an NV center sensor 600, according to some embodiments.
- the sensor 600 includes an optical excitation source 610, which directs optical excitation to an NV diamond material 620 with NV centers.
- An RF excitation source 630 provides RF radiation to the NV diamond material 620.
- the NV center sensor 600 may include a bias magnetic field source 670, such as a permanent magnet or electromagnet, applying a bias magnetic field to the NV diamond material 620.
- Light from the NV diamond material 620 may be directed through an optical filter 650 and an electromagnetic interference (EMI) filter 660, which suppresses conducted interference, to an optical detector 640.
- EMI electromagnetic interference
- the sensor 600 further includes a controller 680 arranged to receive a light detection signal from the optical detector 640 and to control the optical excitation source 610 and the RF excitation source 630.
- the RF excitation source 630 may be a microwave coil, for example.
- the optical excitation source 610 may be a laser or a light emitting diode, for example, which emits light in the green band, for example.
- the optical excitation source 610 induces fluorescence of the NV diamond material in the red band, which corresponds to an electronic transition from the excited state to the ground state.
- Light from the NV diamond material 620 is directed through the optical filter 650 to filter out light in the excitation band (in the green for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 640.
- the EMI filter 660 is arranged between the optical filter 650 and the optical detector 640 and suppresses conducted interference.
- the controller 680 is arranged to receive a light detection signal from the optical detector 640 and to control the optical excitation source 610 and the RF excitation source 630.
- the controller may include a processor 682 and a memory 684, in order to control the operation of the optical excitation source 610 and the RF excitation source 630.
- the memory 684 which may include a nontransitory computer readable medium, may store instructions to allow the operation of the optical excitation source 610 and the RF excitation source 630 to be controlled.
- the controller 680 controls the operation such that the optical excitation source 610 continuously pumps the NV centers of the NV diamond material 620.
- the overall fluorescence intensity is reduced at resonance, as discussed above with respect to FIG. 3.
- the NV center sensor 600 may also function as a magnetic field sensor.
- the assessment of the DNV material may take place in a dedicated test system prior to incorporation of the DNV material in a sensor system or after the DNV material has been incorporated in a sensor system, such as a magnetic field sensor.
- a dedicated test system allows the DNV material to be evaluated after production or upon receipt from a supplier. In this manner it can be assured that the DNV material exhibits the desired properties before incorporation in to a device.
- Assessing the DNV material after incorporation in a sensor system allows the condition of the DNV material to be monitored throughout the lifetime of the sensor system. This arrangement allows the DNV material to be monitored and a user alerted if the DNV material is damaged or degrades to an extent that the accuracy or operation of the sensor system would be negatively impacted.
- a dedicated test system for assessment of the DNV material may include the features of the NV sensor system depicted in FIG. 6 and described above.
- the zero field splitting (ZFS) amount of the DNV material is measured in the absence of an external magnetic field.
- the bias magnetic field source 670 may be omitted from the sensor system.
- a switchable bias magnetic field source 670 such as an electromagnet, may be employed in the off state when measuring the ZFS amount.
- Magnetic shielding may be included in the sensor system to reduce or eliminate the magnetic field acting on the DNV material during the measurement of the ZFS amount.
- the test system may include a controller of the type depicted in FIG. 6.
- the controller may be programmed to control the optical excitation source and the RF excitation source to produce a luminescence signal at the optical detector.
- the controller is also programmed to determine the ZFS amount, D and E from the luminescence signal received by the optical detector in the manner described above. During the measurement of the ZFS amount, D and E, a magnetic bias field is not applied to the DNV material.
- the test system may include an automated system for disposing the DNV material in the test system.
- the automated system may include any component capable of disposing the DNV material in the test system.
- the test system may be configured such that a user can place the DNV sample in the test system.
- the ZFS amount, D and E provide insight into the degree of strain in the crystal lattice of the DNV material.
- the controller may be programmed to determine the degree of strain in the crystal lattice of the DNV material based on the measured ZFS amount, D and E. Determining the degree of strain in the crystal lattice may include comparing the measured ZFS amount, D and E to pre-determined threshold values stored in the memory of the controller. In the case that the measured ZFS amount, D and E fall within the range defined by the threshold values, the degree of strain in the crystal lattice of the DNV material is determined to be acceptable.
- the ZFS amount, D and E also provide insight into the concentration of crystal lattice defects present in the DNV material.
- the controller may be programmed to determine the concentration of crystal lattice defects in the crystal lattice of the DNV material based on the measured ZFS amount, D and E. Determining the concentration of crystal lattice defects in the crystal lattice may include comparing the measured ZFS amount, D and E to pre-determined threshold values stored in the memory of the controller. In the case that the measured ZFS amount, D and E fall within the range defined by the threshold values, the concentration of crystal lattice defects in the crystal lattice of the DNV material is determined to be acceptable.
- the threshold values for ZFS amount, D and E may be any appropriate value that is associated with a DNV material that exhibits the desired properties. For example, a threshold value for D may be between 2.5 and 5.5 MHz.
- the controller may be programmed to determine whether hyperfines are resolvable in a luminescence signal received at the optical detector when a magnetic bias is applied to the DNV material.
- the controller may be programmed to control the optical excitation source and the RF excitation source to produce the luminescence signal at the optical detector.
- the controller may be programmed to control a magnetic bias generator, such that a magnetic bias field is applied to the DNV material.
- the magnetic bias field applied to the DNV material may be a small magnetic bias field, such as -30 gauss.
- the test system utilized to determine whether hyperfines are resolvable may be the same test system employed to measure the ZFS amount, D and E. Alternatively, the test system utilized to determine whether hyperfines are resolvable may be a different test system than the test system employed to measure the ZFS amount, D and E.
- the ability to resolve hyperfines in the luminescence signal received at the optical detector provides insight as the concentration of NV centers and impurities in the DNV material.
- a hyperfine may be considered to be resolvable when the full width half maximum value for the hyperfine is measurable from the luminescence signal received at the optical detector.
- the ability to resolve hyperfines indicates that the concentration of NV centers and impurities in the DNV material is in an acceptable range.
- Impurities may be considered the inclusion of components in the DNV material that deviate from the intent of manufacture.
- the presence of hyperfines in addition to those associated with the natural isotope 14 N shown in FIG. 55 may indicate that additional impurity species are present in the DNV material.
- hyperfines at other locations in the luminescence signal may indicate that isotopes of N, and/or C are present in the DNV sample.
- the ability to resolve hyperfines in the luminescence signal indicates that the DNV material is of sufficient purity. According to some embodiments, where a high purity DNV material including 14 N and 12 C is desired 15 N and 13 C isotopes are considered impurities. According to some other embodiments, where a high purity DNV material including 15 N and 12 C is desired 14 N and 13 C isotopes are considered impurities.
- the assessment of the DNV material may be carried out in a sensor system.
- the controller of a DNV magnetic field sensor may be programmed to measure the ZFS amount, D and E and determine whether hyperfines can be resolved as described above.
- the result of the measurement of ZFS amount, D and E may be compared to a threshold value stored in a memory of the controller.
- an error message may be communicated to a user of the sensor system.
- hyperfines are not capable of being resolved, an error message may be communicated to a user of the sensor system.
- the error message may be communicated to a user by any appropriate means, such as a display, error light, or wireless communication.
- the ability to resolve hyperfines may be considered to indicate that a concentration of NV centers in the DNV material and/or a concentration of impurities in the DNV material are within a desired range.
- the ability to resolve hyperfines may indicate a concentration on the order of at least parts per million.
- the assessment of the DNV material in the sensor system may be carried out periodically. For example, the assessment may be carried out hourly or daily while the sensor is in use. Alternatively, the assessment of the DNV material may be carried out when the sensor is moved or has been subjected to an event that may have damaged the DNV material. In this manner, the assessment of the DNV material may be carried out throughout the lifetime of the sensor system. This ensures that the DNV material produces acceptable performance over the lifetime of the sensor system. The performance of the sensor system may be negatively impacted if the DNV material exhibits an increased strain, concentration of crystal lattice defects, concentration of impurities, or change in NV center concentration. The assessment of the DNV material throughout the lifetime of the sensor system warns a user of such an occurrence.
- the result of the assessment of the DNV material may be stored in a memory of the controller.
- the stored assessment results may then be utilized to monitor a trend in the properties of the DNV material over time. This information may provide insight into potential future problems with the DNV material in the sensor system, or provide a warning regarding the degradation of the DNV material. For example, an increase in the degree of strain in the crystal lattice over time may indicate that a stress induced fracture of the DNV material is imminent.
- the DNV assessment systems and methods described herein are capable of quickly and non-destructively performing quality control checks on DNV materials.
- the systems are capable of sufficient throughput to operate in line with a DNV sensor manufacturing line, and provide sufficient information regarding the properties of the DNV material to establish that the DNV material is acceptable for use.
- the hyperfine transition responses may exhibit a steeper gradient than the gradient of aggregate Lorentzian responses measured in conventional systems, which can be up to three orders of magnitude larger.
- the hyperfine responses can allow for greater sensitivity in detecting changes in the external magnetic field.
- the detection of the hyperfine responses is then used in a closed loop processing to estimate the external magnetic field in realtime. This may be done by applying a compensatory field via a magnetic field generator controlled by a controller that offsets any shifts in the hyperfine responses that occur due to changes in the external magnetic field.
- the controller continually monitors the hyperfine responses and, based on a computed estimated total magnetic field acting on the system, provides a feedback to the magnetic field generator to generate a compensatory field that is equal and opposite in sign to the vector components of the external magnetic field in order to fix the hyperfine responses despite changes in the external magnetic field.
- This provides a real-time calculation of the external magnetic field in the form of the calculated inverted compensatory field.
- a smaller bias magnetic field which separates out the hyperfine responses to provide sufficient spacing for tracking purposes, may be utilized.
- the application of a smaller bias magnetic field reduces the frequency range needed for the radiofrequency excitation sweep and measurement circuits, thus providing a system that is more responsive and efficient in determining the external magnetic field acting on the system.
- a hyperfine structure of the NV center exists due to the hyperfine coupling between the electronic spin states of the NV center and the nitrogen nucleus, which results in further energy splitting of the spin states.
- FIG 8 shows the hyperfine structure of the ground state triplet 3 A 2 of the NV center.
- mi spin states three hyperfine transitions
- Each of the three hyperfine transitions manifest within the width of one aggregate Lorentzian dip. With proper detection, the hyperfine transitions may be elucidated within a given Lorentzian response.
- the NV diamond material 620 exhibits a high purity (e.g., low existence of lattice dislocations, broken bonds, or other elements beyond 14 N) and does not have an excess concentration of NV centers.
- the RF excitation source 630 is operated on a low power setting in order to further resolve the hyperfine responses.
- additional optical contrast for the hyperfine responses may be accomplished by increasing the concentration of NV negative-charge type centers, increasing the optical power density (e.g., in a range from about 20 to about 1000 mW/mm 2 ), and decreasing the RF power to the lowest magnitude that permits a sufficient hyperfine readout (e.g., about 1 to about 10 W/mm 2 ).
- FIG. 9 shows an example of fluorescence intensity as a function of an applied RF frequency for an NV center with hyperfine detection.
- the gradient plotted against the applied RF frequency f(t) is shown.
- the three hyperfine transitions 200a-200c constitute a complete Lorentzian response 20 (e.g., corresponding to the Lorenztian response 20 in FIG. 7).
- the point of maximum slope may then be determined through the gradient of the fluorescence intensity as a function of the applied RF frequency, which occurs at the point 250 in FIG. 9. This point of maximum slope may then be tracked during the applied RF sweep to detect movement of the point of maximum slope along the frequency sweep. Like the point of maximum slope 25 for the aggregate Lorentzian response, the corresponding movement of the point 250 corresponds to changes in the total incident magnetic field B t (t), which because of the known and constant bias field B bias (t), allows for the detection of changes in the external magnetic field B ext (t).
- point 250 exhibits a larger gradient than the aggregate Lorentzian gradient described above with regard to FIG. 7.
- the gradient of point 250 may be up to 1000 times larger than the aggregate Lorentzian gradient of point 25. Due to this, the point 250 and its corresponding movement may be more easily detected by the measurement system resulting in improved sensitivity, especially in very low magnitude and/or very rapidly changing magnetic fields.
- a bias or control magnetic field B bias may be applied.
- the first magnetic field generator e.g., a permanent magnet
- the second magnetic field generator e.g., a three-axis Cartesian B b i as (t) Helmholtz coil system
- the second magnetic field generator 675 is electrically connected to the controller 680, by which the magnetic field produced by the second magnetic field generator 675 may be controlled by the controller 680.
- the total incident magnetic field may be linearly expressed as:
- ⁇ represents the nitrogen vacancy gyromagnetic ratio of about 28 GHz/T.
- the maximum gradient or slope may be determined by the Jacobian operator evaluated at a critical frequency f c where the Lorentzian aggregate or hyperfine slope is the greatest: (2)
- the critical frequency f c is determined analytically based on the NV diamond material 620 incorporated into the sensor system and is pre-stored in the controller 680 for processing purposes.
- the total incident magnetic field may be estimated according to the critical frequency:
- the open-loop or ad-hoc method shown in FIG. 64 relies on continuous tracking to determine the external magnetic field vector B ext (t) based on subtraction of the known bias control magnetic field B bias (t) from the total estimated incident field B t (t).
- the determination of the external magnetic field vector B ext (t) may be affected due to sensitivity to external in-band and corrupting disturbance fields or related Hamiltonian effects (e.g., temperature, strain).
- the above open loop method requires constant re-calibration and
- FIGS. 58 and 59 show a closed loop processing performed by the controller 680 according to an exemplary embodiment of the present invention.
- the closed loop processing described herein allows the estimated total incident magnetic field B t (t) to be computed in realtime and actuated through the second magnetic field generator 675 to create a compensatory field B comp (t).
- This compensatory field may then be used to offset the shifts in RF response by the external magnetic field B ext (t) to produce a fluorescence response that remains constant and fixed, thus reducing the need for constant tracking of the response shifts.
- FIG. 58 is a schematic diagram showing the closed loop processing using the compensatory field
- FIG. 59 is a flowchart depicting a method in performing the closed loop processing shown in FIG. 58.
- a bias field B bias (t) is applied to separate out the Lorentzian responses at desired frequencies (e.g., equally-spaced frequencies).
- the bias field may be applied using the first magnetic field generator 670 (e.g., a permanent magnet), which is known and constant.
- the bias field may alternatively be applied by the second magnetic field generator 675.
- an initial calibration offset R shown in FIG. 58, in the form of a constant, is added to the driver G, which drives the second magnetic field generator 675 to generate the bias field necessary to separate the Lorentzian hyperfine responses.
- the closed loop processing may proceed to a step S5910, where the unknown external magnetic field B ext (t) is read.
- this step may be performed in a similar manner as the processing described with regard to FIG. 57, where an estimated total incident magnetic field B t t) is computed by evaluating the gradient of the intensity response /(t) as a function of applied frequency f(t) at the critical frequency.
- a step S5920 shifts in the hyperfine responses are observed. Largest changes per a predetermined sampling period may be identified in order to identify the vector direction of the unknown magnetic field. The observed shifts may then be used to close the loop processing as shown in FIG. 58. Specifically, the closed loop processing includes a feedback controller block
- the feedback H and driver G serve as transfer functions to output a signal to the second magnetic field generator 675 to generate the compensatory field B comp (t) that represents the magnetic field needed to ensure that the largest gradient of the response remains fixed in terms of intensity response, thereby offsetting any shifts due to the external magnetic field B ext (t) .
- B comp the compensatory field
- Loop closure may be achieved with the feedback H and driver G set as either constant gains (e.g., a Luenberger Observer ) or state and measurement noise covariance driven variable gains (e.g., a Kalman filter) or a non-linear gain scheduled observer or the like, where each control system embodiment may be tailored to the specific application.
- a compensatory field B comp (t) is stored with an inverted sign to the shift observed in step S5920. Because this compensatory field B comp (t) represents an equal, but opposite, magnetic field as the unknown external field B ext (t), the inverse of the compensatory field B comp (t) may be subsequently exported in a step S5941 and stored in the controller 680 as the external field
- step S5950 the controller net spectral gain is further increased to drive the compensatory field B comp (t) to lock to the external field B ext (t) such that the observed intensity response remains fixed.
- step S5910 Such a processing allows for the compensatory field B comp (t) stored by the controller 680 to offset any shifts in the intensity response caused by the external field B ext (t), resulting in real-time computation of the external field by virtue of this processing.
- the loop algebra for the closed loop processing may be represented as follows.
- the total incident magnetic field is represented by the sum total of the unknown external field and the sum of the bias field and the compensatory field that is applied when the loop is closed. Because the bias field is constant over time, for the purposes of evaluating the required compensatory field needed for the closed loop processing, the bias field will be excluded in the loop algebra below.
- the total incident field may be represented by:
- equation (3) may be expressed as: [00468] Loop closure based on the estimated total magnetic field B t (t) in order to produce the compensatory field B comp (t) using the feedback and driver gains and the calibration reference may be expressed as follows:
- equation (7) may be reduced as follows:
- control loop processing of the system 600 provides a means to fix the hyperfine responses despite changes in the external magnetic field.
- a smaller bias magnetic field may be utilized, while still retaining a robust means to detect and calculate changes due to the external magnetic field.
- the application of a smaller bias magnetic field reduces the frequency range needed for the RF excitation sweep and measurement circuits of the intensity response, which provides a system that is more responsive and efficient in determining the external magnetic field acting on the system.
- the range of signal amplitudes to which the system can detect and respond to quickly and accurately may be significantly improved, which can be especially important for large amplitude magnetic field applications.
- the system utilizes a Ramsey pulse sequence to detect and measure the magnetic field acting on the system.
- Parameters relating to the Ramsey pulse sequence are optimized before measurement of the magnetic field. These parameters include the resonant Rabi frequency, the free precession time (tau), and the detuning frequency, all of which help improve the sensitivity of the measurement. These parameters may be optimally determined using calibration tests utilizing other optical detection techniques, such as a Rabi pulse sequence or additional Ramsey sequences.
- parameters, in particular the resonant Rabi frequency may be further optimized by an increase in power of the RF excitation source, which may be achieved through the use of a small loop antenna.
- processing of the data obtained during measurement is further optimized by the use of at least two reference windows, the average of which is used to obtain the signal.
- the NV center in a diamond comprises a substitutional nitrogen atom in a lattice site adjacent a carbon vacancy as shown in FIG. 1.
- the NV center may have four orientations, each corresponding to a different crystallographic orientation of the diamond lattice.
- the NV center may exist in a neutral charge state or a negative charge state.
- the neutral charge state uses the nomenclature NV°, while the negative charge state uses the nomenclature NV, which is adopted in this description.
- the NV center has a number of electrons, including three unpaired electrons, each one from the vacancy to a respective of the three carbon atoms adjacent to the vacancy, and a pair of electrons between the nitrogen and the vacancy.
- the NV center which is in the negatively charged state, also includes an extra electron.
- the optical transitions between the ground state 3 A 2 and the excited triplet 3 E are predominantly spin conserving, meaning that the optical transitions are between initial and final states that have the same spin.
- a photon of red light is emitted with a photon energy corresponding to the energy difference between the energy levels of the transitions.
- NV Center or Magneto-Optical Defect Center, Magnetic Sensor System
- the system 300 includes an optical excitation source 310, which directs optical excitation to an
- the system further includes an RF excitation source
- NV diamond material 320 which provides RF radiation to the NV diamond material 320.
- Light from the NV diamond may be directed through an optical filter 350 to an optical detector 340.
- the RF excitation source 330 may be a microwave coil, for example.
- the optical excitation source 310 may be a laser or a light emitting diode, for example, which emits light in the green, for example.
- the optical excitation source 310 induces fluorescence in the red, which corresponds to an electronic transition from the excited state to the ground state.
- Light from the NV diamond material 320 is directed through the optical filter 350 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the detector 340.
- the component Bz may be determined.
- Optical excitation schemes other than continuous wave excitation are contemplated, such as excitation schemes involving pulsed optical excitation, and pulsed RF excitation. Examples of pulsed excitation schemes include Ramsey pulse sequence (described in more detail below), and spin echo pulse sequence.
- the diamond material 320 will have NV centers aligned along directions of four different orientation classes.
- FIG. 5 illustrates fluorescence as a function of RF frequency for the case where the diamond material 320 has NV centers aligned along directions of four different orientation classes.
- the component Bz along each of the different orientations may be determined.
- crystallographic planes of a diamond lattice allow not only the magnitude of the external magnetic field to be determined, but also the direction of the magnetic field.
- FIG. 3 illustrates an NV center magnetic sensor system 300 with NV diamond material 320 with a plurality of NV centers
- the magnetic sensor system may instead employ a different magneto-optical defect center material, with a plurality of magneto-optical defect centers.
- the electronic spin state energies of the magneto-optical defect centers shift with magnetic field, and the optical response, such as fluorescence, for the different spin states is not the same for all of the different spin states.
- the magnetic field may be determined based on optical excitation, and possibly RF excitation, in a corresponding way to that described above with NV diamond material.
- FIG. 60 is a schematic diagram of a system 6000 for a magnetic field detection system according to an embodiment.
- the system 6000 includes an optical excitation source 6010, which directs optical excitation to an NV diamond material 6020 with NV centers, or another magneto-optical defect center material with magneto-optical defect centers.
- An RF excitation source 6030 provides RF radiation to the NV diamond material 6020.
- a magnetic field generator 6070 generates a magnetic field, which is detected at the NV diamond material 6020.
- the magnetic field generator 6070 may generate magnetic fields with orthogonal polarizations, for example.
- the magnetic field generator 6070 may include two or more magnetic field generators, such as two or more Helmholtz coils.
- the two or more magnetic field generators may be configured to provide a magnetic field having a predetermined direction, each of which provide a relatively uniform magnetic field at the NV diamond material 6020.
- the predetermined directions may be orthogonal to one another.
- the two or more magnetic field generators of the magnetic field generator 6070 may be disposed at the same position, or may be separated from each other. In the case that the two or more magnetic field generators are separated from each other, the two or more magnetic field generators may be arranged in an array, such as a one-dimensional or two-dimensional array, for example.
- the system 6000 may be arranged to include one or more optical detection systems 6005, where each of the optical detection systems 6005 includes the optical detector 6040, optical excitation source 6010, and NV diamond material 6020. Furthermore, the magnetic field generator 6070 may have a relatively high power as compared to the optical detection systems 6005. In this way, the optical systems 6005 may be deployed in an environment that requires a relatively lower power for the optical systems 6005, while the magnetic field generator 6070 may be deployed in an environment that has a relatively high power available for the magnetic field generator 6070 so as to apply a relatively strong magnetic field.
- the system 6000 further includes a controller 6080 arranged to receive a light detection signal from the optical detector 6040 and to control the optical excitation source 6010, the RF excitation source 6030, and the second magnetic field generator 6075.
- the controller may be a single controller, or multiple controllers. For a controller including multiple controllers, each of the controllers may perform different functions, such as controlling different components of the system 6000.
- the second magnetic field generator 6075 may be controlled by the controller 6080 via an amplifier 6060, for example.
- the RF excitation source 6030 may be a microwave coil, for example.
- the optical excitation source 6010 may be a laser or a light emitting diode, for example, which emits light in the green, for example.
- the optical excitation source 6010 induces fluorescence in the red from the NV diamond material 6020, where the fluorescence corresponds to an electronic transition from the excited state to the ground state.
- Light from the NV diamond material 6020 is directed through the optical filter 6050 to filter out light in the excitation band (in the green, for example), and to pass light in the red fluorescence band, which in turn is detected by the optical detector 6040.
- the controller 6080 is arranged to receive a light detection signal from the optical detector 6040 and to control the optical excitation source 6010, the RF excitation source 6030, and the second magnetic field generator 6075.
- the controller may include a processor 6082 and a memory 6084, in order to control the operation of the optical excitation source 6010, the RF excitation source 6030, and the second magnetic field generator 6075.
- the memory 6084 which may include a nontransitory computer readable medium, may store instructions to allow the operation of the optical excitation source 6010, the RF excitation source 6030, and the second magnetic field generator 6075 to be controlled. That is, the controller 6080 may be programmed to provide control.
- the controller 6080 controls the operation of the optical excitation source 6010, the RF excitation source 6030, and the magnetic field generator 6070 to perform Optically Detected Magnetic Resonance (ODMR).
- ODMR Optically Detected Magnetic Resonance
- the component of the magnetic field Bz along the NV axis of NV centers aligned along directions of the four different orientation classes of the NV centers may be determined by ODMR, for example, by using an ODMR pulse sequence according to a Ramsey pulse sequence.
- the Ramsey pulse sequence is a pulsed RF-pulsed laser scheme that measures the free precession of the magnetic moment in the NV diamond material 6020 and is a technique that quantum mechanically prepares and samples the electron spin state.
- FIG. 61 is a schematic diagram illustrating the Ramsey pulse sequence.
- a Ramsey pulse sequence includes optical excitation pulses and RF excitation pulses over a five-step period.
- a first RF excitation pulse 720 in the form of, for example, a microwave (MW) ⁇ /2 pulse
- the system is allowed to freely precess (and dephase) over a time period referred to as tau ( ⁇ ).
- tau a time period referred to as tau ( ⁇ ).
- tau tau
- the system measures the local magnetic field and serves as a coherent integration.
- a second optical pulse 6130 is applied to optically sample the system and a measurement basis is obtained by detecting the fluorescence intensity of the system.
- the RF excitation pulses applied to the system 6000 are provided at a given RF frequency, which correspond to a given NV center orientation.
- the Ramsey pulse sequence shown in FIG. 66 may be performed multiple times, wherein each of the MW pulses applied to the system during a given Ramsey pulse sequence includes a different frequency that respectively corresponds to a different NV center orientation.
- ⁇ represents the free precession time
- ⁇ 2 * represents spin dephasing due to inhomogeneities present in the system 6000
- a> res represents the resonant Rabi frequency
- ⁇ ⁇ ⁇ represents the effective Rabi frequency
- a n represents the hyperfine splitting of the NV diamond material 620 ( ⁇ 2.14 MHz)
- ⁇ represents the MW detuning
- ⁇ represents the phase offset.
- the parameters that may be controlled are the duration of the MW ⁇ /2 pulses, the frequency of the MW pulse (which is referenced as the frequency amount detuned from the resonance location, ⁇ ), and the free precession time ⁇ .
- FIGS. 62 A and 62B show the effects on the variance of certain parameters of the Ramsey pulse sequence. For example, as shown in FIG. 62A, if all parameters are kept constant except for the free precession time ⁇ , an interference pattern, known as the free induction decay (FID), is obtained. The FID curve is due to the constructive/destructive interference of the three sinusoids that correspond to the hyperfine splitting.
- the decay of the signal is due to inhomogeneous dephasing and the rate of this decay is characterized by ⁇ 2 * (characteristic decay time).
- ⁇ 2 * characteristic decay time
- a two-dimensional FID surface plot may be constructed, an example of which is shown in FIG. 63 A.
- the FID surface plot includes several characteristics that can elucidate optimization of the controllable parameters of the Ramsey sequence.
- the FID surface plot is generated using a ⁇ 2 * of about 6150 ns and a resonant Rabi frequency of about 6.25 MHz.
- the horizontal slices of FIG. 63 A represent individual FID curves (e.g., FIG. 62 A), while the vertical slices represent magnetometry curves (e.g., FIG. 62B).
- FID curves of higher fundamental frequency occur at greater detuning.
- FIG. 63B shows the gradient of the two-dimensional FID surface plot of FIG. 63 A.
- ⁇ 2 * used (i.e., about 750 ns)
- operating at around 900 ns will yield the greatest sensitivity.
- the decay in the horizontal axis of FIG. 63B is characterized by ⁇ 2
- the decay in the vertical axis is characterized by the ratio of the resonant Rabi frequency a> res (described in more detail below) to the effective Rabi frequency ⁇ ⁇ ⁇ .
- the effective Rabi frequency may be defined by equation (a2) below:
- the ratio of the resonant Rabi frequency and the effective Rabi frequency may be expressed in terms of the resonant Rabi frequency, as follows:
- a general three-step approach may be used to obtain highly sensitive magnetometry measurements.
- a first step is performed to verify the resonant Rabi frequency i res .
- the inhomogeneous dephasing ⁇ 2 * of the system is measured.
- the parameter space of equation (al) is optimized and a highly sensitivity magnetometry measurement is performed.
- a bias magnetic field using the magnetic field generator 6070 is applied to the system 6000 such that the outermost resonance of the fluorescence intensity response is separated, while the three remaining resonances for the other axes remain overlapping.
- either a CW-CW sweep or a single ⁇ pulse sweep is applied to identify the resonance RF frequency that corresponds to the axis of interest (i.e., the outermost resonance).
- a series of Rabi pulses is applied.
- FIG. 64 shows an example of a Rabi pulse sequence. As shown in FIG. 64, three periods of optical and RF excitation pulses are applied.
- a first optical excitation pulse 6410 is applied, which is followed by a RF excitation pulse 6420 (e.g., a MW pulse).
- the Rabi pulse sequence is then completed by a second optical excitation pulse 6430.
- the time interval in which the RF pulse is applied (shown as tau ⁇ in FIG. 64, but this tau ⁇ should be distinguished from the free precession interval ⁇ in a Ramsey pulse sequence) is varied.
- a constant optical duty cycle is maintained to minimize thermal effects in the system. This may be achieved with the use of a variable "guard" window, shown as the period 6450 in FIG. 64, between the first optical pulse 6410 and the MW pulse 6420.
- the guard window 6450 helps to ensure that the first optical pulse 6410 is completely off by the time the MW pulse 6420 is applied, thus preventing any overlap between the two pulses and preventing the optical pulse from partially re-initializing the NV diamond material while the MW pulse 6420 is being applied.
- the resonant Rabi frequency ⁇ ⁇ 3 is defined by the frequency of the resulting curve.
- FIG. 65 shows measured curves A-D after the application of the Rabi pulses using varying RF excitation power (e.g., MW power). As shown by the differences in the frequency of curves A-D, by increasing the MW power applied to the system 6000, the resonant Rabi frequency ⁇ ⁇ 3 obtained also increases. Thus, to obtain practical Rabi frequencies (e.g., greater than 5 MHz), substantial amounts of MW power should be used. In some embodiments, sufficient MW power may be applied to ensure that application of the pulses is kept short, while, at the same time, the MW power may be limited to avoid saturation.
- RF excitation power e.g., MW power
- a power of about 10 watts may be applied.
- the necessary power requirements to achieve practical Rabi frequencies may be difficult to achieve.
- a small loop antenna e.g., an antenna having a loop size of about 2 mm in diameter
- a high MW power may be achieved while significantly reducing the required antenna power due to the ability to position the antenna in closer proximity to the NV diamond material 6020.
- the increase in MW power achieved by the small loop antenna allows for an increase in the resonant Rabi frequency i res .
- the data obtained during this step of the measurement process is used to determine the ⁇ /2 pulse necessary to perform the Ramsey pulse sequence (described below).
- ⁇ may be defined as the first minimum of the Rabi curve obtained (e.g., curve D in FIG. 65).
- a second step of the measurement process using the ⁇ /2 pulse determined by the resonant Rabi frequency and the resonance location obtained during the first step above, measurements of the inhomogeneous dephasing ⁇ 2 * of the system are obtained. Measurements are performed similar to the Rabi measurements described above, except a Ramsey pulse sequence is used. As described above with reference to the Ramsey pulse sequence, tau ⁇ denotes the free precession time interval in this step. [00510]
- the detune frequency ⁇ is set to be relatively high, in certain embodiments. As noted above, larger detune frequencies cause higher fundamental frequencies (see, e.g., FIG. 63 A), thus allowing for greater contrast, making the data easier to fit.
- the detune frequency ⁇ may be set to about 10 MHz. However, for relatively large ⁇ 2 , smaller detune frequencies may be used.
- FIG. 62A shows one example of an FID curve that may be used to obtain ⁇ 2 , where the detune frequency was set to about 10 MHz.
- the optimal free precession time ⁇ may be determined based on the strong interference regions discussed above with reference to FIG. 63B.
- a small range of x's are also collected on either side of the optimally determined free precession time due to the theta term in equation (al).
- the optical pulse used for optical polarization of the system and the optical pulse used for measurement readout may be merged into one pulse during application of a series of Ramsey sequences.
- the optical power of the optical excitation source 6010 may be set to about 1.25 W
- the MW ⁇ /2 pulse may be applied for about 50 ns
- the free precession time ⁇ may be about 420 ns
- the optical excitation pulse duration may be about 50 ⁇ .
- guard windows may be employed before and after the MW ⁇ /2 pulses, which may be set to be about 2.28 and 20 ns in duration, respectively.
- the curve in the intensity response is typically only measured once to obtain the slope and fine-tuned frequency, and additional measurements are only taken at the optimal detuning frequency, while the fluorescence signal is monitored.
- the system may experience drift caused by, for example, optical excitation heating (e.g., laser-induced heating) and/or strain, which can contribute to imprecision and error during the measurement process. Tracking a single spin resonance does not properly account for the translation in response curves due to thermal effects.
- data obtained from the measuring process is saved in real-time and sensitivity is determined offline to minimize time between measurements.
- two magnetometry curves (e.g., FIG. 62B) may be obtained for both the positive and negative spin states.
- FIG. 66 shows an example of a raw pulse data segment that may be obtained during a given measurement cycle.
- the signal is defined as the first 300 ns of an optical excitation pulse. However, this definition applies at optical power densities that are near saturation. As optical power density decreases from saturation, the useful part of the signal may extend further in time.
- the end of the pulse when the system has been polarized, is referenced in order to account for power fluctuations in the optical excitation source (e.g., the laser).
- the samples within the windows or periods may be averaged to obtain a mean value of the signal contained within the respective window or period.
- the value of the windows or periods may be determined using a weighted mean.
- the first and second reference windows are equally spaced from the signal window, as shown in FIG. 66. This extension of referencing allows for better estimation of the optical excitation power during the acquisition of the signal and an overall increase in sensitivity of the system.
- FIG. 67 is a schematic illustrating a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- the magnetic sensor shown in Figure 6 used a single RF excitation source 630 and a bias magnet 670.
- the DNV sensor illustrated in Figure 7 uses six separate RF elements that also provide the bias field that is provided the bias magnet 670 in Figure 6. Accordingly, in various implementations, the DNV sensor shown in Figure 67 does not require a separate bias magnetic.
- Figures 67 - 73 illustrate various components of the DNV sensor.
- the portion of the illustrated DNV sensor includes a heatsink 6702 that can connect to the rest of the DNV sensor via a mounting clamp.
- a light element such as a laser or LED that is located within or near the heatsink 6702.
- Light from the light element travels through a lens tube 6706 through a focusing lens tube 6718 and through a coil assembly 6716 that includes the NV diamond.
- Light passes into the coil assembly 6716 through the NV diamond and exits the coil assembly.
- Light that exits the coil assembly passes through a red filter to a photo sensor assembly 6714.
- the coil assembly 6716, red filter, and photo sensor can all be housed in a lens tube 6710 that can be coupled to lens tube 6718 via a lens tube coupler 6708.
- a lens tube rotation mount 6712 allows a rotation adjustment element to be attached that allows the coil assembly to be rotated in relation to the light element.
- FIG. 68 is a schematic illustrating a cross section of a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- the portion of the DNV sensor that is illustrated contains the coil assembly 6816 and the photo sensor 6820.
- the coil assembly 6816 includes six RF elements.
- Each RF element has an RF mount that can be used to connect an RF cable 6830.
- each RF element can have its own RF feed.
- the each RF element is fed a unique RF signal.
- subcombinations of the RF elements receive the same RF feed signal. For example, groups of two or three RF elements can receive the same RF feed signal.
- FIG. 70 is a cross section illustrating a coil assembly in accordance with some illustrative implementations. In this illustration, the light path 7030 is shown. The light path allows for light from the lighting element to pass through the coil assembly and through the NV diamond 7040. Light exits the NV diamond and proceeds out of the coil assembly through the light path 7030.
- the coil assembly includes four RF elements 7002 and two top and bottom elements 7020.
- the NV diamond 7040 is held in place via a diamond plug 7004 that holds the diamond in the mounting block 7006.
- the RF elements can be held together using various means such as element mounting screws 7032.
- the six total RF elements can be seen in Figures 69A and 69B that illustrate a coil assembly in accordance with some illustrative
- RF elements 6902 are shown along with two top and bottom RF elements 6920. Each RF element is attached to a center mounting block 6904. Attachment mechanisms such as screws 6932 can be used to attach the RF elements to the mounting block.
- a light injection hole 6930 is the bottom RF element and the light exit hole 6970 is in the top RF element. Accordingly, in this implementation light passes through the coil assembly and the diamond in a straight path. In one implementation, the light enters a face of the NV diamond and exits through another face of the NV diamond. As described below, in other implementation the light path through the coil assembly is not straight and may take on multiple paths of egress.
- FIG 71 is a schematic illustrating a side element 7100 of a coil assembly in accordance with some illustrative implementations.
- the side element 7100 can include a middle mounting hole and one other mounting hole. In this implementation, there would be side elements that had different mounting hole configurations. As shown in Figure 71, the side element 7100 has three mounting holes, but not all mounting holes are required to be used. In one implementation, the middle mounting hole and one of the remaining two mounting holes are used, but all three mounting holes are not used.
- Each side element 7100 includes an RF connector 7102 that is used to provide the RF feed signal to the side element.
- Figure 72 is a schematic illustrating a top or bottom element 7200 of a coil assembly in accordance with some illustrative implementations. Similar to the side element 7100, the top or bottom element 7200 includes an RF connector 7202 for receiving an RF feed signal. The top or bottom element 7200, however, has only two mounting holes 7204. The three hole is a light path portion 7230 that allows for light to enter or exit the coil assembly.
- Figure 73 is a schematic illustrating a center mounting block 7300 of a coil assembly in accordance with some illustrative implementations.
- the NV diamond is located within the mounting block 7300.
- a diamond plug can be used to hold the NV diamond.
- the mounting block 7300 can include a diamond mounting location that provides alignment of the NV diamond.
- the mounting block 7300 can include a recess that fits the NV diamond. Once positioned, the diamond plug can be inserted into the mounting block 7300 to hold the diamond in place.
- Figures 74-77 illustrate another implementation.
- Figure 74 is a cross section illustrating of a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- a coil assembly 7416 holds an NV diamond within an NV diamond sensor.
- the coil assembly 7416 can include six RF elements, four side elements and two top and bottom elements (shown in Figures 75-77).
- RF cables 7430 can connect to the RF elements via RF connections 7432.
- the RF cables 7430 are used to provide an RF signal to one or more of the RF elements.
- the RF signal can be different for each RF element or subsets of the RF elements can receive different RF signals.
- RF feed signals are used by the RF elements to provide a uniform microwave RF signal to the NV diamond.
- the arrangement of the RF elements allows the RF elements to also provide the magnetic bias field to the NV diamond.
- light enters and exits through the top and bottom elements.
- Light that exits the NV diamond can pass through a red filter 7426 and through a light pipe 7450 that is located within an attenuator 7440.
- at least a portion of the light pipe 7450 is located within the attenuator 7440.
- Figure 75 is a schematic illustrating a coil assembly in accordance with some illustrative implementations.
- Figure 76 is a schematic illustrating a cross section of a coil assembly in accordance with some illustrative implementations.
- the coil assembly includes two bottom or top RF elements 7506 and 7606.
- the top or bottom RF elements are circular and are larger compared to the side elements 7502 and 7602.
- Figure 77 is a schematic illustrating a side element of a coil assembly in accordance with some illustrative implementations.
- the side element has an RF connector 7702 used to provide a feed RF signal to the RF element.
- the side RF elements do not include any mounting holes as the side RF elements can be held into position by the top and bottom RF elements.
- each of the RF elements can include multiple stacked spiral antenna coils. These stacked coils can occupy a small footprint and can provide the needed microwave RF field in such that the RF field is uniform over the NV diamond. Additional details regarding RF elements and RF circuit boards that contain RF elements are described in U.S. Patent Application
- each RF side element and top and bottom RF elements can include an RF element or an RF circuit board.
- the NV diamond 7622 is located within the six RF elements.
- the RF elements can be held together by mounting screws 7510 and 7610.
- a light injection portion 7504 of the top RF element allows light to enter the coil assembly and enter the NV diamond.
- the bottom portion includes a corresponding light egress portion 7620.
- the NV diamond can fit within a mounting block 7608 and be held in position via a diamond plug 7624.
- Figures 78-84 illustrate another implementation.
- light enters the NV diamond through an edge of the NV diamond and exits through multiple faces of the NV diamond. How light enters and exits the NV diamond is based upon the orientation of the NV diamond relative to the light source.
- the NV diamond can be repositioned to allow light to enter and exit from edges, faces, and/or both edges and faces.
- Figure 78 is a schematic illustrating a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations. Similar to other implementations, the DNV sensor includes a light source heatsink 7802 and 7902, a mounting clamp 7804 for the heatsink 7802, a lens tube 7806, a focusing lens tube 7818, a coil assembly 7816 located, and red filters and photo sensor assemblies 7814, and a lens tube rotation mount 7812 and 7912.
- Figure 79 is a schematic illustrating a cross section of a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations. In this implementation, the light source is an LED 7906.
- a thermal electric cooler 7904 can be used to provide cooling for the LED 7906.
- Light from the LED 7906 can be focused using lens 7918. The focused light enters the NV diamond that is located within the coil assembly 7916.
- Figure 80 is a schematic illustrating a cross section of a portion of a DNV sensor with a coil assembly in accordance with some illustrative implementations.
- the NV diamond 8040 within the coil assembly can be seen.
- the light the exits the NV diamond 8040 travels one of two light pipes 7914.
- at least a portion of the light pipe is located within an attenuator.
- the NV diamond 8040 can be held in place within the coil assembly via center mounting blocks 8050.
- the mounting blocks and the coil assembly can be held in place using retaining rings 8052.
- RF cables 8030 connect to the RF elements via RF connectors 8032 to provide an RF feed signal to the RF elements as described in greater detail below.
- Figure 81 is a schematic illustrating a coil assembly in accordance with some illustrative implementations.
- Figure 82 is a schematic illustrating a cross section of a coil assembly in accordance with some illustrative implementations.
- Figure 81 shows four side elements 8014 and 8242 located between the top and bottom RF elements 8112 and 8212.
- the center mounting blocks 8108 and 8208 and retaining plate 8106 and 8206 are also shown.
- light enters the NV diamond 8240 at an edge. The light reaches the NV diamond via a light injection opening 8101 and 8202.
- a second light exit hole is opposite of the illustrated light exit hole 8110.
- the second light exit hold is behind the NV diamond 8240.
- Figure 83 is a schematic illustrating a side element of a coil assembly in accordance with some illustrative implementations.
- the individual side element includes an RF connector 8304 and a light egress portion 8302.
- the side element does not include any attachment holes. Rather, the side elements can be held in place within the coil assembly using the top and bottom elements as illustrated in Figures 84 A and 84B.
- Figures 84A and 84B are schematics illustrating top and bottom elements of a coil assembly in accordance with some illustrative implementations.
- the top element includes slots 8406 for aligning and holding into position the four RF side elements.
- the light injection hole 8404 is also shown.
- RF connectors 8404 located on both the top RF element and the bottom RF element allow for separate RF feeds to be separately applied to the top and bottom RF elements.
- Various aspects of the subject technology provide methods and systems for general purpose removal of geomagnetic noise.
- the subject solution combines the use of an array (e.g., 1-D or 2-D) of highly sensitive vector magnetic sensors with proper transformation means and signal processing to separate the broadly-spatially-correlated Pc and Pi noise from the local anomalies that affect fewer sensors of a spatially distributed array of DNV sensors.
- the vector magnetic sensors of the subject technology are large enough and spaced densely enough such that the magnetic signal of interest (SOI) is detected by at least one sensor but is below the target noise floor for many of the other sensors.
- the proper transformation means can achieve transforming the sensor measurements to a common coordinate system by transforming each element of an array of measured magnetic field values to provide an array of transformed magnetic field values.
- the signal processing includes signal processing of the spatially distributed array of sensors.
- Geomagnetic noise that is of considerable significance is that due to the solar wind impinging on the exoatmosphere. This noise can be decomposed into diurnal variations (slow daily variations due to the orientation of the earth relative to the sun) and what are termed "Pc and Pi" noise.
- the Pc and Pi noise are the most problematic in many potential applications, as they vary in time scales that are similar to the magnetic signals that one may wish to measure (signals resulting from some object in motion relative to a magnetic sensor, either because the object is moving and the sensor is stationary, or because the object is stationary and the sensor is being moved, or some combination). It is thought that the Pc and Pi noise, together, span the frequency range of 0.01 Hz and 5 Hz, with a spectrum shape proportional to 1/f (f is frequency) in this band.
- the nature of the Pc and Pi noise may be investigated by comparing generated model Pc and Pi noise to that of empirical data.
- This model Pc and Pi noise may be generated, for example, by passing white Gaussian noise through a linear filter with this shape and steep rolloff above and below this passband. For amplitude, empirical data was used from: J.
- SACLANTCEN which measures peak-to-peak values over time windows of different lengths, averaged over months.
- the noise amplitude of the model data is adjusted to have comparable peak-to-peak statistics.
- the comparison is shown in FIG. 85, where the geomagnetic noise model compares well with empirical data.
- the SACLANTCEN paper also suggests that the geomagnetic noise is spatially highly correlated over tens of kilometers.
- Other sources discuss the Pc and Pi noise as originating at an altitude of about 100 km, affirming that it is reasonable to expect high correlation over distances greater than 10 km when measured on the earth surface or undersea.
- FIG. 86 illustrates a signal of interest due to a distortion in the magnetic field in the Z-direction by an unmanned underwater vehicle (UUV) for magnetic field over time as measured by a single magnetic sensor.
- FIG. 86 illustrates the signal of interest without noise and a measurement of the signal of interest including noise. As can be seen, the signal of interest is overwhelmed by the noise.
- UUV unmanned underwater vehicle
- FIGs. 87A-87C illustrate the signal of interest due to a distortion in the magnetic field in the Z-direction by an unmanned underwater vehicle (UUV) for magnetic field at three different times as measured by a two-dimensional array of sensors, to provide an array of measured magnetic field values, on the sea floor.
- UUV unmanned underwater vehicle
- the array used for the dataset is a 3 l-by-31 sensor array spaced at 100m, such that the center is the 16
- the large and dense array of sensors is sufficiently large such that many sensors are unaffected by a signal of interest and spaced closely enough such that the signal of interest is detected by at least one sensor when the signal is present.
- the sensor array may include 1-D (one-dimensional) or 2-D (two- dimensional) array of many precision vector magnetometers.
- High pass time-domain filtering can remove very slow variations on the order of many hours or longer.
- S the signal defined as the local magnetic field variation of interest, which is to be measured
- F the interest floor chosen to be a value lower than the amplitude of S to be used in the definition of signals that are too small to be of interest.
- Rmax be the maximum influence region of S, defined as maximum size and shape of the region (1-D or 2-D) in which the amplitude of S may be greater than F.
- N be the vector environmental noise for which the time variations of the noise may be large compared to S, but at each time sample are spatially correlated such that the variation is much less than F over a distance more than twice the diameter of Rmax.
- the vector magnetic sensor of the subject technology are of high precision relative to F such that the sensor noise is negligible as compared to F.
- the array (1-D or 2-D) of these sensors is dense enough such that when the variation of interest is present, S is greater than F for at least one sensor and large enough relative to Rmax such that for most of the sensors, S is less than F.
- the means of establishing a common coordinate system can measure the orientation of the sensors relative to the local earth coordinate system so as to achieve a common coordinate system among the sensors.
- a spatial-domain common-mode rejection algorithm (CMRA) processes each time sample of the array measurements and produces an array of values preserving local variations greater than F, while reducing residual errors from N to amplitude below F.
- the magnetic sensor is a DNV sensor.
- the means of measurement of the orientation of the sensor can be the measurement of the earth's local magnetic field as one reference direction, and an inclinometer (gravity) vector
- the CMRA includes subtraction of the median value of the sensor array at each point in time.
- the CMRA can further include the combination of the identification of a region of interest where S may be present, a noise estimation using the measurements outside of the region of interest, and subtraction of the estimated noise.
- the identification of a region of interest may be performed either by using the difference of the measured value from the median value exceeding a chosen threshold, or the spatial gradient of the measured value exceeding a chosen threshold.
- the noise estimation can be performed by fitting the measurements with a curve such as a constant (e.g., the average of the measurements), a line (e.g., in the case of a 1-D array), a plane (e.g., in the case of a 2-D array), or a spline.
- the noise estimation can include a Kriging approach to estimate the noise in the region of interest from the measured values outside of the region of interest.
- FIG. 88 illustrates a magnetic sensor array system 8800 according to an embodiment of the invention.
- the system includes a controller 8810 and a magnetic sensor array 8830, which includes a number of magnetic sensors 8832.
- the spacing being adjacent sensors 8832 may be s, for example. While FIG. 88 illustrates the magnetic sensors 8832 to be arranged in a two-dimensional array, the magnetic sensors 8832 may be arranged in a one- dimensional array or in some other dimension. Further, while FIG. 88 illustrates a 4 by 3 array of sensors 8832 for simplicity, in general the array may be much larger, or may be smaller.
- the controller 8810 receives magnetic field signals from each of the magnetic sensors 8832, where the magnetic field signals are indicative of the magnetic field measured at each of the magnetic sensors 8832. Thus, the controller 8810 receives an array of magnetic field values.
- the controller 8810 may include a processor 8812 and a memory 8814.
- the magnetic field signals received by the controller 8810 may be stored in the memory 8814 as data.
- the memory 8814 may further store instructions which are executed by the processor to allow the controller 8810 to perform various data processing operations, such as establishing a common coordinate system, high pass time domain filtering, and noise removal exploiting spatially coordinated noise, as discussed further below.
- the memory 8814 may include a non- transitory computer readable medium to store the instructions and data.
- FIG. 88 illustrates a single processor 8812 and a single memory 8814
- the controller 8810 may include more than one processor 8812 to perform various functions, and may include more than one memory. Further the controller 8810 may include subcontrollers arranged in a distributed manner.
- the sensors 8832 may be DNV sensors, for example, or other magnetic sensors such as Hall effect sensors.
- the magnetic fields measured by each of the magnetic sensors may be transformed to a common coordinate system which is common to all of the magnetic sensors.
- FIGs. 89A and 89B illustrate a common coordinate system, and coordinate system corresponding to one of the magnetic sensors, respectively.
- the sensors may be arranged such that they are fixed relative to each other such that they are initially in a common coordinate system. This could be accomplished by fixing the sensors in a rigid material, for example.
- the Z axis is considered to be "down,” that is, the direction of the gravity vector.
- the X axis is considered to be perpendicular to the Z axis such that the local magnetic north vector is in the X-Z plane.
- Y is considered to be perpendicular to X and Z thus providing a right-hand coordinate system, where Y is pointed nearly east.
- FIG. 90 illustrates an orientation sensor 9000 attached to a magnetic field sensor 8832.
- Each of the magnetic field sensor 8832 may have a corresponding orientation sensor 9000, which measures the orientation of magnetic field sensor 8832 relative to one or more directions, such as the Z-direction, for the common coordinate system.
- the orientation sensor 9000 aids in achieving a common coordinate system for the data from all of the sensors 8832.
- the orientation sensor 9000 may be a gravity sensor, which is affixed to a
- the orientation sensor 9000 is aligned with its corresponding sensor 8832 so as to be in a same coordinate system.
- R is a unitary rotation matrix for the particular sensor 8832.
- R could be designated as R 1,7' to denote the rotation matrix associated with the sensor in the i, j position since it will be different for each i, j .
- the i, j notation may be omitted for simplicity.
- Converting the magnetic measurements of each magnetic sensor 8832 to a common coordinate system is as follows. For each sensor, measure R as a coordinate system calibration step. This may be achieved partly by using a gravity sensor as the orientation sensor 9000, for example. Alternatively, the orientation may be taken based on detection of the orientation of the stars. Then take the product of magnetic measurements with the transpose of the rotation matrix, R T , to place the magnetic measurements in the X, Y, Z common coordinate system.
- the rotation matrix R may be estimated as follows. As stated, the third column of R is the vector direction in a sensor coordinate system that would result from an input in the Z direction. The estimate of the Z direction in sensor coordinates may be denoted as Z, thus the estimated R, denoted R, has as its third column, Z. Likewise, the first and second columns of R may be denoted as X and ⁇ respectively. Thus, determining the estimated R is performed by estimating the columns of R, being X, ⁇ and Z.
- the Z value may be simply taken as the measurement of Z from the orientation sensor 9000, which may be a gravity sensor.
- the measurement of Z from a gravity sensor will be the true value of Z plus a rotation error in the sensor.
- a reasonable bound on a rotation error for existing cost-effective gravity sensors is 0.01 degrees.
- the lvalue may be calculated by taking the magnetic measurement of a sensor
- the accuracy of the transformation of the magnetic field measurement to a common coordinate system may be estimated as follows.
- all of the sensors are independently randomly orientated, with the following process: For each sensor: (1) generate an axis of rotation by selecting a random vector with a uniform distribution over the unit sphere, (2) generate an angle of rotation by selecting a random angle uniformly from f— radians, radians], and (3) create a random rotation matrix for the sensor based on the selected axis of rotation and angle of rotation by using well-known linear algebra techniques, such as the Rodrigues' rotation formula, for example.
- This random rotation provides the true value for R l, i for each i,j sensor.
- the rotation is then applied to the magnetic field dataset of the sensor, producing the dataset in the non- aligned individual sensor coordinates.
- R l, i for each i, j was calculated separately, with the following imperfection including: (1) a gravity sensor rotational error of about 0.01 degrees, unique for each sensor, where the error was simulated by: (a) randomly picking a rotation error from a uniform distribution over [-0.01 degrees, 0.01 degrees], (b) rotating a unit vector lined up with the Z-Axis towards the Y-Axis by the selected rotation error to form Z', (c) randomly picking a second rotation angle uniformly from [0, 2 ⁇ ], and (d) rotating Z' about the original Z-axis by the selected second rotation angle, and (2) a single time sample of the modeled geomagnetic noise and magnetic sensor noise.
- the single time sample was provided such that the value of the earth's magnetic field (magnetic north) was based on a location in the ocean in the vicinity of New York City. At this latitude, magnetic north had a significant inclination.
- the earth magnetic field vector used was micro Tesla.
- the transpose of R l, i was applied to place the measurements in the common X, Y, Z coordinate system. That is the data used below for all of the common mode rejection algorithms. Further, for the common mode rejection algorithms that follow, a (time/freq domain) high-pass filter is applied to the array of measured magnetic field values remove variations that are very slow (e.g. nearly constant over hours) and therefore the large magnetic north component is absent.
- the unfiltered magnetic measurement is used because magnetic north is of interest in establishing the coordinates.
- Figures 91A-91I illustrate the array of measured magnetic field values including the magnetic signal of interest without noise in a scenario where one UUV is travelling past the array of sensors, and Figures 93 A-93I illustrate the signal of interest with two UUVs passing at different depths and in different directions.
- FIGs. 91 A-91C illustrate the magnetic field measurement component along the X-direction, Y-direction and Z-direction, respectively, at a time of 500 seconds.
- FIGs. 91D-91F illustrate the magnetic field
- FIGs. 91G-91I illustrate the magnetic field measurement component along the X-direction, Y-direction and Z-direction, respectively, at a time of 1500 seconds.
- FIGs. 93A-93I correspond to FIGs. 91 A-91I, respectively, but for the case of two UUVs.
- the median value of the magnetic field for all of the sensors of the array is determined for each of the X, Y, and Z coordinates separately, and the median value is then subtracted from the magnetic field dataset.
- the median value of the magnetic field value is taken as an estimate of the spatially correlated background noise and subtracted from the transformed magnetic field values to provide noise removed magnetic field values. Because the noise is spatially highly correlated and because the signal of interest is significant in less than half of the array, the median value is a reasonable measurement of the geomagnetic noise.
- Figures 93A-93C show the results for the Median Subtraction approach, where FIG.
- FIG. 93 A shows the magnetic measurement at one of the sensors, and the noise-free signal of interest, over time
- FIG. 93B shows the result at the same sensor after noise removal, and the noise-free signal of interest
- FIG. 93C shows the difference in the two lines (noise free and reconstructed) of FIG. 93B, on a different scale.
- Figures 94A-94C shows the magnetic field including the signal of interest in the X-direction for the array at times of 500, 1000 and 1500 seconds, respectively, which demonstrates an excellent fit when compared to the noise free signal shown in FIGs. 91 A, 91D and 91G, respectively.
- the spatially correlated noise in the region of interest may be estimated, and subtracted from the magnetic field measurement in the region of interest.
- the spacing of the sensors and the size of the array of sensors is such that some of the sensors 8832 are not in the region of interest.
- the fraction of the sensors which are outside the region of interest may be > 50%, for example.
- a "region of interest" is established, where the region of interest are those magnetic sensors where there appears to be a signal of interest because the magnetic measurements show local deviation from the spatially correlated noise by more than a predetermined threshold.
- the array elements where the signal of interest exists are adjacent to each other.
- the region of interest is excluded from the region where the rest of the measurement are performed (the remaining magnetic sensors which are not part of the region of interest) to provide a remaining array of transformed magnetic field values, and the rest of the
- the measurements are used to estimate the geomagnetic noise.
- the estimated geomagnetic noise is subtracted from the entire region (the region of interest plus the remaining region) covered by the magnetic sensor array (all of the magnetic sensors) including the signal of interest.
- One method for identifying the signal of interest is as follows. The median measured magnetic field is subtracted across the array from each magnetic sensor, and then a predetermined amplitude threshold (such as .01 nT in these examples) is applied. Any magnetic sensor values above the threshold are assumed to be signals of interest in the region of interest.
- a predetermined amplitude threshold such as .01 nT in these examples
- the region of interest may be expanded slightly using expansion techniques. Because magnetic field variations do not change abruptly, the region of interest may be expanded.
- the region of interest may be expanded using a set closing algorithm, based on dilation followed by erosion, using standard morphological image processing techniques and then taking the convex hull of the resulting region.
- Figures 95A-95C shows the resulting regions of interest in an example for the magnetic field component in the X-direction at 500, 1000, and 1500 seconds, respectively.
- the lighter color region is the "core" region of interest, i.e. the values for which the measurements deviate from the array median enough to exceed the threshold.
- the darker color regions are the additional sensors that are included in the region of interest as a result of set closing and convex hulling of the region.
- the region of interest could be expanded by taking the union of the regions according to the magnetic field components in the X-direction, Y-direction and Z-direction, or, alternatively use the 2-norm of the vector value in the thresholding step.
- the region of interest is identified, it is removed, and then the rest of the data is fit, such as, for example, by fitting to a plane, or fitting to a quadratic spline.
- a Kriging technique could be applied to the data with region of interest removed, to produce an estimate of the noise in the region of interest.
- FIGs. 96A, 96B and 96C illustrate a fit of a plane to the data for the magnetic field component in the X-direction, where FIGs. 96A, 96B and 96C correspond to times of 500, 1000 and 1500 seconds.
- the fit plane is the meshed sheet, and the specific sensor measurements are the dots. The dots obscure the plane to some extent, but in all cases the plane is a reasonably good fit.
- FIGs. 97A, 97B and 97C illustrate the results for the X-direction magnetic field component obtained by subtracting the planar estimate of the noise, where FIG. 97A shows the magnetic measurement at one of the sensors, and the noise-free signal of interest, over time, FIG. 97B shows the result at the same sensor after noise removal, and the noise-free signal of interest, and FIG. 97C shows the difference in the two lines (noise free and reconstructed) of the FIG. 97B, on a different scale. As can be seen, the noise removal works well.
- FIGs. 98 A, 98B and 98C illustrate a fit of a quadratic spline to the data for the magnetic field component in the X-direction, where 98A, 98B and 98C correspond to times of 500, 1000 and 1500 seconds.
- the fit quadratic spline is the meshed sheet, and the specific sensor measurements are the dots.
- FIGs. 99A, 99B and 99C illustrate the results for the X-direction magnetic field component obtained by subtracting the quadratic spline estimate of the noise, where FIG. 99A shows the magnetic measurement at one of the sensors, and the noise-free signal of interest, over time, FIG. 99B shows the result at the same sensor after noise removal, and the noise-free signal of interest, and FIG. 99C shows the difference in the two lines (noise free and reconstructed) of the FIG. 99B, on a different scale.
- FIGs. 100A, 100B and lOOC two regions of interest corresponding respectively to the two UUVs are first identified in a manner similar to that described above with respect to a single UUV.
- the regions of interest are then expanded using a set closing algorithm, based on dilation followed by erosion, using standard morphological image processing techniques and then taking the convex hull of the resulting region.
- Figures lOOA-lOOC shows the resulting regions of interest in an example for the magnetic field component in the X-direction at 500, 1000, and 1500 seconds, respectively.
- the lighter color region is the "core" region of interest, i.e. the values for which the measurements deviate from the array median enough to exceed the threshold.
- the darker color regions are the additional sensors that are included in the region of interest as a result of set closing and convex hulling of the region.
- two regions of interest a identified, each one corresponding to a different one of the two UUVs.
- the regions of interest are first separated as shown in FIG. 100 A, and then overlap in FIG. 100B, and then are separated again in FIG. lOOC, suggesting that the two UUVs are moving so that one passes over the other.
- the regions of interest are removed, and then the rest of the data is fit, such as, for example, by fitting to a plane, or fitting to a quadratic spline.
- a Kriging technique could be applied to the data with region of interest removed, to produce an estimate of the noise in the region of interest.
- FIGs. 101 A, 101B and 101C illustrate, for the two UUV case, a fit of a quadratic spline to the data for the magnetic field component in the X-direction, where 101 A, 101B and 101C correspond to times of 500, 1000 and 1500 seconds.
- the fit quadratic spline is the meshed sheet, and the specific sensor measurements are the dots.
- FIGs. 102 A, 102B and 102C illustrate, for the two UUV case, the results for the
- FIG. 102A shows the magnetic measurement at one of the sensors, and the noise-free signal of interest, over time
- FIG. 102B shows the result at the same sensor after noise removal, and the noise-free signal of interest
- FIG. 102C shows the difference in the two lines (noise free and reconstructed) of the FIG. 102B, on a different scale.
- DNV magnetic sensors with a sensor assembly that provide a number of advantages over magnetic sensor systems where the optical excitation sources, RF excitation source, and optical detectors are all formed on different substrates or as separate components mechanically supported.
- the sensor assembly described provides for a diamond NV sensor system in a single compact homogeneous device. Providing the optical excitation sources and the optical detectors on the same assembly substrate, such as on a same silicon wafer, reduces the overall system cost, size and weight. Providing the RF excitation source directly on the NV diamond material reduces the overall system size and weight. Providing the optical detectors directly on the NV diamond material reduces the amount of the red fluorescence emitted by the NV centers lost to the surroundings, which improves the system efficiency.
- Providing the optical excitation sources directly on the NV diamond material increases the amount of the optical excitation light by drastically reducing the amount of optical excitation light lost to the environment.
- Combining the optical excitation sources, RF excitation source, and optical detectors directly on the NV diamond material results in a significant size reduction that results in NV diamond sensors that are usable in small consumer and industrial products.
- a sensor assembly 10300 which includes a base substrate 10310 and a diamond assembly 10320, or a material assembly generally, of a NV center magnetic sensor according to an embodiment, is illustrated in FIGs. 103 A, 103B, 104A, 104B, 104C and 105.
- FIGs. 103 A and 103B respectively illustrates a top perspective view, and a bottom perspective view of the sensor assembly 10300.
- FIGs. 104A and 104B respectively illustrate a top perspective view, and a bottom perspective view of the diamond assembly 10320.
- FIG. 104C illustrates a side view of an assembly substrate 10350 of the diamond assembly 10320.
- FIG. 105 illustrates a top view of the diamond assembly 10320.
- the sensor assembly 10300 includes a base substrate 10310, and a diamond assembly 10320 arranged on the base substrate 10310.
- the sensor assembly 10300 further includes power/logic circuits 10330, which may be in the form of chips, mounted on the base substrate 10310, both on a top surface 10312 adjacent the diamond assembly 10320, and on bottom surface 10314 opposite to the top surface 10312.
- Attachment elements 10340 such as screws for example, extending in the base substrate 10310, allow for the attachment of the sensor assembly 10300 to further components.
- the base substrate 10310 may be, for example, a printed circuit board (PCB).
- the diamond assembly 10320 has the assembly substrate 10350, and NV diamond material 10352, or another magneto-optical defect center material with magneto- optical defect centers, formed over the assembly substrate 10350.
- the diamond assembly 10320 includes a plurality of optical excitation sources 10354 and a plurality of optical detectors 10356 on, or embedded in, the assembly substrate 10350.
- An RF excitation source 10358 is formed on the NV diamond material 10352, and connected to an RF connector 10360.
- the optical excitation sources 10354 and the RF excitation source 10358 are in general terms electromagnetic excitation sources.
- the optical excitation sources 10354 and the optical detectors 10356 may be arranged in an alternating fashion, such as the checkerboard arrangement shown. While FIGs. 103 A, 104A and 105 illustrate an arrangement with four optical excitation sources 10354 and five optical detectors 10356, other numbers of optical excitation sources 10354 and optical detectors 10356 are contemplated.
- the alternating arrangement of the optical excitation sources 10354 and the optical detectors 10356 reduces the amount of the red fluorescence emitted by the NV diamond material 10352 lost to the surroundings, which improves the system efficiency
- the optical excitation sources 10354 and the optical detectors 10356 need not be arranged in an alternating fashion.
- a bottom surface 10362 of the assembly substrate 10350 opposite to a top surface 10366 adjacent the NV diamond material 10352, has a plurality of connection pads 10364.
- Conductive through connections 10368 electrically connect the connection pads 10364 to the top surface 10366, and electrically connect to the optical excitation sources 10354 and the plurality of optical detectors 10356 to allow control of the optical excitation sources 10354 and to receive optical signals from the plurality of optical detectors 10356.
- the power/logic circuits 10330 are electrically connected to the connection pads 10364 via wirings 10334 on the base substrate 10310, to allow control of the optical excitation sources 10354 and to receive optical signals from the plurality of optical detectors 10356.
- the wirings 10334 may extend through the base substrate 10310 to those power/logic circuits 10330.
- a power/logic connector 10332 is electrically connected to the power/logic circuits 10330.
- the power/logic connector 10332 includes a plurality of connectors 10333, which allow for connection of power/logic circuits 10330 to a power source and controller (not shown in FIGs. 103A-105) external to the sensor assembly 10300, such as the controller 680 illustrated in FIG. 6.
- the control functions may be split between the power logic circuits 10330 and the external controller.
- the RF connector 10360 allows for connection of the RF excitation source 10358 to a power source and controller (not shown in FIGs. 103 A- 105) outside the sensor assembly 10300, such as the controller 680 illustrated in FIG. 6.
- the assembly substrate 10350 may be a semiconductor material, such as silicon, upon which the plurality of optical excitation sources 10354 and a plurality of optical detectors 10356 are formed.
- the assembly substrate 10350 may be a silicon wafer, for example.
- the optical excitation sources 10354 may be laser diodes or light emitting diodes (LEDs), for example.
- the optical excitation sources 10354 emit light which excites fluorescence in the NV diamond material 10352, and may emit in the green, such at a wavelength of about 532 nm or 518nm, for example.
- the excitation light is not in the red so as to not interfere with the red fluorescent light collected and detected.
- the optical detectors 10356 detect light, and in particular detect light in the red fluorescence band of the NV diamond material 10352.
- the optical excitation sources 10354 and the optical detectors 10356 may be formed on a single silicon wafer as the assembly substrate 10350 using fabrication techniques known for silicon fabrication, such as doping, ion implantation, and patterning techniques.
- the power/logic circuits 10330 and the power/logic connecter 10332 are mounted on the base substrate 10310, which may be a PCB.
- the mounting may be performed by soldering, for example.
- the RF excitation source 10358 may be formed on the NV diamond material
- the RF excitation source 10358 acts as a microwave RF antenna.
- the RF excitation source 10358 may be formed by forming a metal material on the NV diamond material 10352 followed by patterning the metal material.
- the metal material may be patterned by photolithography techniques, for example.
- the metal material may be formed on the
- NV diamond material 10352 first by forming a thin film seed layer 10370 on the NV diamond material 10352, followed by depositing a film metallization 10372 on the seed layer 10370.
- the seed layer 10370 may be, for example, TiW
- the film metallization 10372 may be Cu, for example.
- the seed layer 10370 and the film metallization 10372 are formed, they are patterned, such as by photolithography techniques, for example, to form the RF excitation source 10358 into a coil shape.
- the RF connector 10360 is then formed at one end of the coil shaped RF excitation source 10358.
- the sensor assembly described herein provides a number of advantages over magnetic sensor systems where the optical excitation sources, RF excitation source, and optical detectors are all formed on different substrates or as separate components mechanically supported.
- the sensor assembly described provides for a diamond NV sensor system in a single compact homogeneous device. Providing the optical excitation sources and the optical detectors on the same assembly substrate, such as on a same silicon wafer, reduces the overall system cost, size and weight. Providing the RF excitation source directly on the NV diamond material reduces the overall system size and weight. Providing the optical detectors directly on the NV diamond material reduces the amount of the red fluorescence emitted by the NV centers lost to the surroundings, which improves the system efficiency.
- Providing the optical excitation sources directly on the NV diamond material increases the amount of the optical excitation light by drastically reducing the amount of optical excitation light lost to the environment.
- Combining the optical excitation sources, RF excitation source, and optical detectors directly on the NV diamond material results in a significant size reduction that results in NV diamond sensors that are usable in small consumer and industrial products.
- FIGs. 107 A and 107B illustrate a diamond assembly according to another embodiment.
- the RF excitation source 10358 which may comprise a first RF excitation source 10358a and second RF excitation source 10358b, is larger in the plane of the NV diamond material 10352 than the NV diamond material 10352.
- the first RF excitation source 10358a and the second RF excitation source 10358b are on opposite sides of the NV diamond material 10352.
- the plane of the NV diamond material 10352 is horizontal and into the page in FIG. 107 A, and is parallel to the page in FIG. 107B. While FIGs.
- 107 A and 107B illustrate two RF excitation source 10358a and 10358b, only a single RF excitation source may be provided.
- the diamond assembly of FIGs. 107A and 107B further may include optical detectors 10356 and optical excitation sources 10354 in a similar fashion to earlier disclosed embodiments.
- 10358a may be spiral as shown in FIG. 107A (as well as in FIGs. 103 A, 104A and 105).
- the spiral shape provides a maximum field with low driving power, thus providing good efficiency.
- the spiral shape allows for the coil of the RF excitation source to be made larger, which allows for a more uniform field over a larger device.
- the size of the first RF excitation source 10358a and second RF excitation source 10358a in the plane of the top surface 10380 of the NV diamond material 10352 is greater than a size of the top surface 10380 in the plane.
- the greater size allows for a more uniform field provided by the RF excitation sources 10358a and 10358b applied to the NV diamond material 10352.
- the RF excitation sources 10358a and 10358b are on the NV diamond material 10352, but further extend to a support material 10700 laterally adjacent the NV diamond material 10352.
- the support material may be a material other than diamond, or may be diamond substantially without NV centers, for example.
- the size of the first RF excitation source 10358a and second RF excitation source 10358a in the plane of the top surface 10380 of the NV diamond material 10352 is also greater than a size of a detector region 10702 which includes the optical detectors 10356.
- NV- negatively charged NV centers
- NV° magnetically neutral uncharged NV centers
- the subject technology can manipulate the phonon spectrum to alter the phonon sideband of fluorescence spectrum of both the NV° and NV " centers. During room temperature operation, the NV° fluorescence spectrum overlaps with the NV " spectrum.
- generating separation between these overlapping spectrums by altering the phonon mediated spectrum allows a filter to be used with the magnetometer device and/or with the data output from the magnetometer device to filter out the unwanted spectrum of NV° photon emissions while reducing the amount of NV " photon emissions filtered out.
- optical contrast is defined by ratio of NV " photon emissions to total fluorescence.
- the total fluorescence is a combination of NV° photon emissions, NV " photon emissions, and a ratio of photon emissions transmitted to scattered optical drive, such as transmitted into the diamond of the DNV and/or absorbed by other nitrogen vacancies.
- the optical drive is traditionally higher energy and narrowband making it easy to filter out.
- the majority of fluorescence from NV° centers and NVcenters that originates from a phonon sideband is a function of the energy versus momentum (E vs. k). That is, the
- fluorescence from the NV° centers and NVcenters that originates from the phonon sideband is a function of the applied optical drive and the momentum imparted by a phonon assisting the transition of the electron from the conduction band to the valence band.
- the width and shape of the spectral content of the photon emissions is thus a function of the combination of the phonon spectrum and the E vs. k variation.
- Controlling the phonon spectrum can alter the response fluorescence spectrum, which can allow the spectrum profile of wavelengths of the NV° photon emissions and the NV " photon emissions to be narrowed.
- the peaks of the NV° photon emissions at a particular wavelength and the NV " photon emissions at another particular wavelength display a more defined difference in fluorescence intensity peaks based on the greater separation of the NV° and NV " spectra.
- the more defined fluorescence intensity peaks can permit a filter, such as a long pass filter, to be used to filter out the unwanted NV° photon emissions, thereby increasing the optical contrast for the remaining NV " photon emissions.
- the NV° and NV " spectra can be manipulated through acoustic driving and diamond shape optimization that affects the phonon spectrum experienced by the NV° centers and NV " centers.
- acoustic driving can increase and/or control the phonon spectrum by generating phonons within the lattice structure of the diamond at a specific frequency or at a set of specific frequencies.
- the generation of phonons at a specific frequency can narrow the phonons experienced by the NV centers within the diamond such that the effects of other phonons, e.g., lattice vibrations, such as those introduced based upon the temperature of the material, may be reduced.
- the narrowing of phonons experienced by the NV centers can result in sharper wavelength intensity peaks for the NV° photon emissions and the NV " photon emissions.
- the bandwidth of the NV° and NV " spectra can be narrowed to permit optical filtering.
- the shape of the diamond can be modified to enhance the phonon spectrum by modifying the resonance of the diamond.
- the resonance of the diamond can also narrow the phonons experienced by the NV° and NV " centers.
- the optical drive applied to the diamond of the DNV sensor may be matched with a NV° zero phonon line to decrease the phonon sideband.
- FIG. 108 is a graphical diagram 10800 depicting an example of a DNV optical fluorescence spectrum from NV° centers and NV " centers.
- the meaningful signal is a change in fluorescence of the NV " states, indicating a resonant energy level.
- the inactive NV fluorescence spectrum 10820 overlaps the desired signal of the NV " fluorescence spectrum 10810.
- the NV° fluorescence spectrum 10820 causes a large background signal that is subject to noise and that ultimately raises the noise floor and reduces magnetic field detection sensitivity.
- the majority of the spectral content of the NV fluorescence spectrum is the result of the phonon mediated transitions.
- exciton recombination requires absorption of a phonon and release of a photon.
- the released photon is the fluorescence of the NV " fluorescence spectrum 10810 and/or NV° fluorescence spectrum 10820 shown in FIG. 108.
- room temperature diamonds there is a Boltzmann distribution of phonon energies dictated by the temperature and variations in vibrations experienced in the lattice structure of the diamond, resulting in a broad phonon spectrum that can be experienced by the NV° and NV " centers of the diamond.
- the broad phonon spectrum results in the broad bandwidth of the NV " fluorescence spectrum 10810 and NV° fluorescence spectrum 10820 as shown in FIG. 108.
- the NV " fluorescence spectrum 10810 and NV° fluorescence spectrum 10820 overlap, thus resulting in an increase in the background of the signal and low optical contrast.
- FIG. 109 depicts an energy vs. momentum diagram 10900 for the indirect band gap of a diamond of a DNV sensor showing a valence band 10910 and a conduction band 10920.
- an optical drive 10930 is applied to and absorbed by an electron in the valence band 10910, the excited electron is elevated to the conduction band 10920.
- the electron returns to the ground state from the conduction band 10920 through recombination, a photon is emitted.
- a fluorescence spectrum of photons 10950 are emitted as shown in FIG. 108.
- matching the optical drive frequency 10930 with a zero phonon line (ZPL) 10940 can decrease the phonon sideband, thereby increasing the optical contrast.
- ZPL zero phonon line
- the energy of the resulting photons is hco, where h is the Plank constant and ⁇ is the angular frequency, which is equal to 2 f, where /is the frequency.
- ZPL zero phonon line
- vibrational energy is introduced into the diamond at such low temperatures, such as through an acoustic driver, then the added vibrational energy results in phonon energy, h P h 0 non, that can be imparted to the electrons in the momentum direction of the diagram 10900 for phonon assisted transitioning.
- the resulting fluorescence photons 10950 emitted from the phonon driven electrons results in a second peak for the driven vibrational frequency.
- the driven vibrational frequency can be adjusted to narrow the phonon spectrum at room temperature, thereby narrowing the
- the shape of the diamond can be modified to manipulate the phonon spectrum by modifying the resonance of the diamond, either separately or in addition to the driven vibrational frequency.
- FIG. 1 10 illustrates is a graphical diagram 11000 depicting NV° and NV " photon intensity spectra relative to wavelength with fluorescence manipulation.
- the desired signal of the NV " fluorescence spectrum 11010 and the inactive NV° fluorescence spectrum 11020 include narrower bandwidths for the peaks at particular frequencies due to controlling the phonon spectrum that alters the response fluorescence spectrum.
- the phonon spectrum manipulation can be controlled through acoustic driving and/or diamond size and/or shape optimization.
- the narrow bandwidth peaks allows for greater separation between the NV° and NV " spectra, which enables the use of filtering to increase optical contrast.
- a filter such as a long pass filter
- a filter can be used to filter out the unwanted NV° photon emissions while filtering a minimal amount of NV " photon emissions, thereby increasing the optical contrast.
- the subject technology provides a device that can control the phonon content within the diamond resulting in a controlled spectral content. This allows for better background suppression and overall greater optical contrast.
- the optical contrast can be directly related to the overall system sensitivity. For instance, with narrower bandwidth peaks for the NV " fluorescence spectrum 11010, smaller changes in magnitude of an external magnetic field can be detected. In some instances, controlling the phonon spectrum within the diamond may allow achieving an optical contrast that approaches the theoretical limit or approximately 25%. [00614] FIG.
- I l l depicts a method 11100 for fluorescence manipulation of a diamond having nitrogen vacancies through phonon spectrum manipulation using an acoustic driver.
- the method 11100 includes providing a diamond having nitrogen vacancies and an acoustic driver (block 11102).
- the diamond having nitrogen vacancies can be part of a DNV sensor that includes a photo detector configured to detect photon emissions from the diamond responsive to laser excitation of the diamond.
- the acoustic driver may be a piezoelectric acoustic driver or any other acoustic driver for inducing vibrations to the diamond.
- the acoustic driver may be coupled to the diamond to directly impart vibrational energy to the diamond or may be spaced apart from the diamond to indirectly impart vibrational energy to the diamond.
- the acoustic driver may be positioned relative to the diamond such that the acoustic driver drives the diamond parallel to the nitrogen vacancies of a lattice of the diamond.
- the method 11100 may include modifying a shape and/or size of the diamond to manipulate a phonon spectrum based on resonance of the diamond (block 11104).
- the shape of the diamond may be modified to alter the internal resonance of the diamond such that the phonons resulting from the vibrational energy imparted based on the temperature can be narrowed for the phonon spectrum.
- the size of the diamond may also be modified to alter the resonance to manipulate the phonon spectrum.
- the method 11100 further includes acoustically driving the diamond with the acoustic driver to manipulate the phonon spectrum (block 11106).
- Acoustically driving the diamond may include activating the acoustic driver at a particular frequency to narrow the phonon spectrum.
- the acoustic driver may be a piezoelectric acoustic driver.
- the acoustic driver may be positioned relative to the diamond such that the acoustic driver drives the diamond parallel to the nitrogen vacancies of a lattice of the diamond.
- the method may include applying a long pass filter to filter NV° photon emissions from NV " photon emissions (block 11108).
- the filter such as a long pass filter, can be used to filter out the unwanted NV° photon emissions while filtering a minimal amount of NV " photon emissions, thereby increasing the optical contrast.
- the long pass filter may be incorporated into the photo detector of the DNV sensor and/or may be applied to data output from the photo detector.
- FIG. 112 depicts a method 11200 for determining an acoustic driving frequency for phonon spectrum manipulation for a DNV sensor.
- the method 11200 can include subjecting a diamond of a DNV sensor to near 0 Kelvin (block 11202).
- the diamond of the DNV sensor includes nitrogen vacancies and the DNV sensor may include a photo detector configured to detect photon emissions from the diamond responsive to laser excitation of the diamond.
- Subjecting the diamond to near 0 Kelvin may include cryogenically cooling the diamond to a near 0 Kelvin temperature.
- the method 11200 includes acoustically driving the diamond having nitrogen vacancies of the DNV sensor at a first frequency using an acoustic driver (block 11204).
- Acoustically driving the diamond may include activating the acoustic driver at a particular frequency to narrow the phonon spectrum.
- the acoustic driver may be a piezoelectric acoustic driver.
- the acoustic driver may be positioned relative to the diamond such that the acoustic driver drives the diamond parallel to the nitrogen vacancies of a lattice of the diamond.
- the first frequency can be a randomly selected frequency, a frequency within a range of frequencies, and/or a frequency based on a frequency response output.
- the method 11200 includes detecting a first set of NV° photon emissions and a first set of NV " photon emissions from the DNV sensor (block 11206).
- the detection of the first set of NV° photon emissions and the first set of NV " photon emissions from the DNV sensor may include receiving and processing data from a photo detector of the DNV sensor.
- the first set of NV° photon emissions and the first set of NV " photon emissions from the DNV sensor may form spectra such as those shown in FIGS. 108 or 110.
- the method 11200 includes acoustically driving the diamond having nitrogen vacancies of the DNV sensor at a second frequency using an acoustic driver (block 11208).
- the second frequency can be a randomly selected frequency, a frequency within a range of frequencies, and/or a frequency based on a frequency response output.
- the method 11200 includes detecting a second set of NV° photon emissions and a second set of NV " photon emissions from the DNV sensor (block 11210).
- the detection of the second set of NV° photon emissions and the second set of NV " photon emissions from the DNV sensor may include receiving and processing data from a photo detector of the DNV sensor.
- the second set of NV° photon emissions and the second set of NV " photon emissions from the DNV sensor may form spectra such as those shown in FIGS. 108 or 110.
- the method 11200 includes selecting the second frequency for acoustically driving the diamond with the acoustic driver to manipulate a phonon spectrum based on a wavelength difference between a peak of the second set of NV° photon emissions and the second set of NV " photon emissions from the DNV sensor (block 11212).
- the selection of the second frequency may be based on the second frequency producing a fluorescence spectrum similar to FIG. 110 rather than FIG. 108.
- the method 11200 may include applying a long pass filter to filter NV° photon emissions from NV " photon emissions detected by the photo detector.
- the method 11200 can include modifying a shape of the diamond to manipulate the phonon spectrum based on resonance of the diamond.
- a light source is used to provide light to the diamond.
- the more light that is transmitted through the diamond the more light can be detected and analyzed to determine the amount of red light emitted from the diamond.
- the amount of red light can be used to determine the strength of the magnetic field applied to the diamond.
- photo detectors used to detect the amount of red light are sensitive to electromagnetic interference (EMI).
- EMI electromagnetic interference
- electromagnetic signals can be emitted from electrical components near the diamond. In such cases, EMI from the diamond assembly can affect the photo detectors.
- EMI glass can be used to block and/or absorb EMI signals from the diamond assembly (or associated electronics or signals).
- EMI glass is placed between the diamond and the photo detector, the amount of EMI affecting the photo detector can be reduced.
- the amount of light emitted from the diamond that is sensed by the photo detector can be increased.
- sensitivity of the magnetometer is reduced by inefficient transmission of light between the diamond and the photo detector.
- EMI glass is an inefficient transmitter of light.
- metal embedded in the EMI glass can absorb, block, or reflect light traveling through the EMI glass.
- an EMI shield can be used to block EMI from the diamond assembly.
- the EMI shield may include a hole that allows light to pass to or from the diamond. Depending upon the size of the hole in the EMI shield, some EMI may pass through the hole. Thus, the smaller the hole, the more EMI is prevented from passing through.
- a light pipe may be used to transmit light through the hole in the EMI shield.
- light from a light source can pass through a diamond and through a hole in an EMI shield.
- the light can be collected by a light pipe and travel through the light pipe to a photo detector.
- light pipes are efficient at transmitting light.
- a relatively high percentage of light that is emitted from the diamond can be transferred to the photo detector.
- Any suitable light pipe e.g., a homogenizing rod
- Fig. 113 A is a block diagram of a magnetometer with a light pipe in accordance with an illustrative embodiment.
- An illustrative magnetometer 11300 includes a light source 11305, a diamond 11315, a light pipe 11325, a photo detector 11335, and a shield 11345.
- additional, fewer, and/or different elements may be used.
- a magnet 11340 can be determined by measuring the amount of red light in the light emitted from the diamond 11315.
- the light source 11305 emits source light 11310 to the diamond 11315.
- one or more components can be used to focus the source light 11310 to the diamond 11315.
- the light passes through the diamond 11315, and the modulated light 11320 passes through the hole in the shield 11345. To pass through the hole in the shield 11345, the modulated light 11320 enters and passes through the light pipe 11325.
- the transmitted light 11330 which passed through the hole in the shield 11345, exits the light pipe 11325 and is detected by the photo detector 11335.
- any suitable photo detector 11335 can be used.
- the photo detector 11335 includes one or more photo diodes.
- the photo detector 11335 can be an image sensor.
- the image sensor can be configured to detect light and/or electromagnetic waves.
- the image sensor can be a semiconductor charge-coupled device (CCD) or an active pixel sensor in complementary metal-oxide-semiconductor (CMOS) or N- type metal-oxide-semiconductor (NMOS) technologies. Any other suitable image sensor can be used.
- CCD semiconductor charge-coupled device
- CMOS complementary metal-oxide-semiconductor
- NMOS N- type metal-oxide-semiconductor
- the diamond 11315 is surrounded by one or more components that emit EMI.
- a Helmholtz coil can surround the diamond.
- a two- dimensional or a three-dimensional Helmholtz coil can be used.
- the Helmholtz coil can be used to cancel out the earth's magnetic field by applying a magnetic field with an equal magnitude but opposite direction of the earth's magnetic field.
- the Helmholtz coil can be used to cancel any suitable magnetic field and/or apply any suitable magnetic field to the diamond.
- a microwave generator and/or modulator can be located near the diamond to use microwaves to excite the NV centers of the diamond. The microwave generator and/or modulator can emit EMI that can interfere with the photo detectors.
- the shield 11345 can shield the photo detector 11335 from the EMI.
- the shield 11345 can be a material that attenuates electromagnetic signals.
- the shield 11345 can be solid metal such as a metal foil. In alternative
- materials such as glass, plastic, or paper can be coated or infused with a metal.
- protecting the photo detector 11335 from EMI allows the magnetometer to be more sensitive because the reduction in EMI reduces the amount of noise in the signal received from the photo detector 11335.
- protecting the photo detector 11335 from EMI protects the fidelity of the magnetometer because the signal received from the photo detector 11335 is more accurate. That is, protecting the photo detector 11335 from EMI helps to ensure that a reliable and accurate signal is received from the photo detector 11335 because there is less noise in the signal.
- the noise may include a direct current (DC) offset.
- the light pipe 11325 can be made of any suitable material.
- the light pipe 11325 can be made of quartz, silica, glass, etc.
- the light pipe 11325 is made of optical glass such as BK7 or BK9 optical glass. In alternative embodiments, any suitable material can be used.
- one or more of the faces of the light pipe 11325 can include a filter.
- the face of the light pipe 11325 can filter out non-green light and allow green light to pass through the light pipe 11325, for example, to the diamond 11315.
- light from diamond can pass through a face of the light pipe 11325 that filters out non- red light and permits red light to pass through the light pipe 11325 to the photo detector 11335.
- any suitable filtering mechanism can be used.
- Figs. 113B and 113C are isometric views of a light pipe and a shield in accordance with illustrative embodiments. In alternative embodiments, additional, fewer, and/or different elements may be used. As shown in Fig. 113B, the light pipe 11325 is surrounded axially by the shield 11345. In an illustrative embodiment, the light pipe 11325 and the shield 11345 are coaxial.
- the cross-sectional shape of the light pipe 11325 can be any suitable shape. In the embodiment illustrated in Fig. 113B, the cross-sectional shape of the light pipe 11325 is circular. In the embodiment illustrated in Fig.
- the cross-sectional shape of the light pipe 11325 is octagonal.
- the cross-sectional shape of the light pipe 11325 can be triangular, square, rectangular, or any other suitable shape.
- the cross-sectional shape of the shield 11345 can be any suitable shape.
- the outer shape of the shield 11345 is suited to fit against the wall of a housing that houses the diamond 11315, the photo detector 11335, the light pipe 11325, etc.
- the light pipe 11325 is the same as the length of the shield 11345. In alternative embodiments, the light pipe 11325 can be longer than the shield 11345. For example, the light pipe 11325 may extend beyond the end surface of the shield 11345 at one or both ends. In an illustrative embodiment, the shield 11345 is one inch long. In alternative embodiments, the shield 11345 can be shorter or longer than one inch long. For example, in embodiments in which greater attenuation is beneficial, such as with a more sensitive photo detector 11335, the shield 11345 can be longer. In an illustrative embodiment, the light pipe 11325 can be two inches long. In alternative embodiments, the light pipe 11325 can be shorter or longer than two inches long. For example, the light pipe 11325 can be a length suitable to fit within a housing or arrangement of elements.
- the light pipe 11325 can be tapered along the length of the light pipe 11325.
- the diameter of the light pipe 11325 at one end can be large than the diameter of the light pipe 11325 at the opposite end. Any suitable ratio of diameters can be used.
- a light pipe 11325 can be used to transmit light from the light source 11305, which can be a light emitting diode, to the diamond 11315.
- Using a tapered light pipe 11325 can help to focus the light exiting the light pipe 11325 to enter the diamond 11315 at a more perpendicular angle than if a non-tapered light pipe 11325 were to be used.
- the narrow end can be adjacent to the light source 11305 and the wide end can be adjacent to the diamond 11315.
- the size of the aperture in the middle of the shield 11345 can be sized to block one or more particular frequencies of EMI.
- the diameter of the light pipe 11325 can be between five and six millimeters. In alternative embodiments, the diameter of the light pipe 11325 can be less than five millimeters or greater than six millimeters.
- the light pipe 11325 is sized to have a cross-sectional area that is the same size or slightly larger than a cross-sectional diameter of the diamond 11315. In such embodiments, the light pipe 11325 is sized to capture as much of the light emitted from the diamond 11315 as possible while minimizing the inner diameter of the shield 11345 (and, therefore, maximizing the shielding effect of the shield 11345).
- light from an LED that enters the light pipe 11325 in an uneven pattern can exit the light pipe 11325 in a more uniform pattern. That is, the light pipe 11325 can evenly distribute the light over the surface area of the diamond 11315 or the photo detector 11335. The light pipe 11325 can prevent the light from diverging. Thus, in some embodiments, the light pipe 11325 can be used in place of a lens.
- the outer diameter of the shield 11345 can be any suitable size.
- the outer diameter of the shield 11345 can be sized to block or attenuate electromagnetic signals from the diamond apparatus thereby protecting the photo detector.
- the light pipe 1 1325 passes through the shield 11345. That is, the shield 11345 surrounds the light pipe 11345 along at least a length of the light pipe 11325. In some embodiments, the shield 11345 surrounds the length of the light pipe 11325.
- Fig. 114 is a block diagram of a magnetometer with two light pipes in accordance with an illustrative embodiment.
- An illustrative magnetometer 11400 includes two light pipes 11325, two shields 11345, a diamond 11315, a photo detector 11335, and a photo detector 11350.
- additional, fewer, and/or different elements may be used.
- the magnetometer 11400 includes a light source 1 1305 that sends source light 11310 into a light pipe 11325. Some of the light transmitted from the light source 11305 can be sensed by the photo detector 11350. In some embodiments, the light sensed by the photo detector 11350 is transmitted through the light pipe 11325. In alternative embodiments, the light sensed by the photo detector 11350 does not travel through the light pipe 11325. As discussed above with regard to the magnetometer 11300, the diamond 1 1315 may be associated with electrical components that emit EMI that may interfere with the performance of the photo detector 11350. In such instances, one of the shield 11345 may be placed between the diamond 11315 and the photo detector 11350. Light from the light source 11305 may travel through the light pipe 11325, through the hole in the shield 11345, and into the diamond 11315.
- a shield 11345 may be used to protect the photo detector 11335 from EMI emitted from circuitry associated with the diamond 11315.
- the magnetometer 11400 includes a shield 11345 on either side of the diamond 11315 and the electrical components associated with the diamond 11315.
- Fig. 115 is a block diagram of a magnetometer with two light pipes in accordance with an illustrative embodiment.
- the magnetometer 1 1500 includes a light source 11305, a diamond 11315, two light pipes 11325 with associated shields 11345, and two photo detectors 11335.
- additional, fewer, and/or different elements may be used.
- the source light 11310 from the light source 11305 passes through the diamond 11315.
- the light that enters the diamond 11315 can be split and can exit the diamond 11315 in two streams of modulated light 11320.
- the two streams of modulated light 11320 are in opposite directions.
- the two streams of modulated light 11320 are in any suitable orientation to one another.
- the two streams of modulated light 11320 exit the diamond 11315 in directions orthogonal to the direction in which the source light 11310 enters the diamond 11315.
- Fig. 115 illustrates a magnetometer with two light streams exiting the diamond 11315.
- the magnetometer can be used with three or more light streams that exit the diamond 11315.
- the diamond 11315 is a cube, light can enter the diamond 11315 on one of the six sides.
- up to five light streams can exit the diamond 11315 via the five other sides.
- Each of the five light streams can be transmitted to one of five photo detectors 11335.
- Using two or more light streams that exit the diamond 11315, which are sensed by associated photo detectors 11335, can provide increased sensitivity.
- Each of the light streams contains the same information. That is, the light streams contain the same amount of red light.
- Fig. 116 is a flow diagram of a method for measuring a magnetic field in accordance with an illustrative embodiment. In alternative embodiments, additional, fewer, and/or different operations may be performed. Also, the use of a flow chart and arrows is not meant to be limiting with respect to the order or flow of operations. For example, in some embodiments, one or more of the operations can be performed simultaneously.
- light is generated by a light source.
- Any suitable light source can be used.
- lasers or light emitting diodes can be used.
- sunlight or environmental light can be used as the light source.
- the light generated by the light source is green light or blue light.
- a filter can be used to filter out undesirable light frequencies (e.g., red light).
- light from the light source is sensed.
- the light can be sensed using a photo detector.
- the photo detector is sensitive to electromagnetic interference.
- the operation 11610 is not performed.
- light from the diamond is sensed and the sensed light signal is compared to a pre-determined reference value.
- an operation 11615 light from the light source is transmitted through a first light pipe.
- the first light pipe can be surrounded by a material that attenuates EMI.
- EMI from electrical components near the diamond can be attenuated via the material such that the photo detector is not affected by or is less affected by the EMI.
- the operation 11615 may not be performed.
- light from the light source is transmitted through the diamond.
- the diamond can include NV centers that are affected by magnetic fields. The amount of red light emitted from the diamond (e.g., via the NV centers) can change based on the applied magnetic field.
- light emitted from the diamond is transmitted through a second light pipe.
- light from the second light pipe is sensed. In an illustrative embodiment, the light is sensed via a light detector that is sensitive to EMI.
- the light pipe can be surrounded by material that attenuates EMI from electrical components near the diamond, such as a Helmholtz coil or a microwave generator/modulator.
- a magnetic field point is determined.
- the magnetic field point is a vector with a magnitude and a direction.
- the operation 11635 includes determining a magnitude or a direction.
- the operation 11635 can include comparing the amount of green light (or any other suitable wavelength) emitted from the light source with the amount of detected red light (or any other suitable wavelength) that was transmitted through the second light pipe.
- the amount of detected red light that was transmitted through the second light pipe is compared to a baseline amount.
- any suitable method of determining the magnetic field point can be used.
- a light source is used to provide light to the diamond.
- the more light that is transmitted through the diamond the more light can be detected and analyzed to determine the amount of red light emitted from the diamond.
- the amount of red light can be used to determine the strength of the magnetic field applied to the diamond.
- photo detectors used to detect the amount of red light are sensitive to electromagnetic interference (EMI).
- EMI electromagnetic interference
- electromagnetic signals can be emitted from electrical components near the diamond. In such cases, EMI from the diamond assembly can affect the photo detectors.
- EMI glass can be used to block and/or absorb EMI signals from the diamond assembly (or associated electronics or signals). Thus, if EMI glass is placed between the diamond and the photo detector, the amount of EMI affecting the photo detector can be reduced. To increase the sensitivity of the magnetometer, the amount of light emitted from the diamond that is sensed by the photo detector can be increased. Thus, in some instances, sensitivity of the magnetometer is reduced by inefficient transmission of light between the diamond and the photo detector. In many instances, EMI glass is an inefficient transmitter of light. For example, metal embedded in the EMI glass can absorb, block, or reflect light traveling through the EMI glass.
- an EMI shield can be used to block EMI from the diamond assembly.
- the EMI shield may include a hole that allows light to pass to or from the diamond. Depending upon the size of the hole in the EMI shield, some EMI may pass through the hole. Thus, the smaller the hole, the more EMI is prevented from passing through.
- a light pipe may be used to transmit light through the hole in the EMI shield.
- light from a light source can pass through a diamond and through a hole in an EMI shield.
- the light can be collected by a light pipe and travel through the light pipe to a photo detector.
- light pipes are efficient at transmitting light.
- a relatively high percentage of light that is emitted from the diamond can be transferred to the photo detector.
- Any suitable light pipe e.g., a homogenizing rod
- Fig. 113 A is a block diagram of a magnetometer with a light pipe in accordance with an illustrative embodiment.
- An illustrative magnetometer 11300 includes a light source 11305, a diamond 11315, a light pipe 11325, a photo detector 11335, and a shield 11345.
- additional, fewer, and/or different elements may be used.
- a magnet 11340 can be determined by measuring the amount of red light in the light emitted from the diamond 11315.
- the light source 11305 emits source light 11310 to the diamond 11315.
- one or more components can be used to focus the source light 11310 to the diamond 11315.
- the light passes through the diamond 11315, and the modulated light 11320 passes through the hole in the shield 11345. To pass through the hole in the shield 11345, the modulated light 11320 enters and passes through the light pipe 11325.
- the transmitted light 11330 which passed through the hole in the shield 11345, exits the light pipe
- the photo detector 11335 includes one or more photo diodes.
- the photo detector 11335 can be an image sensor.
- the image sensor can be configured to detect light and/or electromagnetic waves.
- the image sensor can be a semiconductor charge-coupled device (CCD) or an active pixel sensor in complementary metal-oxide-semiconductor (CMOS) or N- type metal-oxide-semiconductor (NMOS) technologies. Any other suitable image sensor can be used.
- CCD semiconductor charge-coupled device
- CMOS complementary metal-oxide-semiconductor
- NMOS N- type metal-oxide-semiconductor
- the diamond 11315 is surrounded by one or more components that emit EMI.
- a Helmholtz coil can surround the diamond.
- a two- dimensional or a three-dimensional Helmholtz coil can be used.
- the Helmholtz coil can be used to cancel out the earth's magnetic field by applying a magnetic field with an equal magnitude but opposite direction of the earth's magnetic field.
- the Helmholtz coil can be used to cancel any suitable magnetic field and/or apply any suitable magnetic field to the diamond.
- a microwave generator and/or modulator can be located near the diamond to use microwaves to excite the NV centers of the diamond. The microwave generator and/or modulator can emit EMI that can interfere with the photo detectors.
- the shield 11345 can shield the photo detector 11335 from the EMI.
- the shield 11345 can be a material that attenuates electromagnetic signals.
- the shield 11345 can be solid metal such as a metal foil. In alternative
- materials such as glass, plastic, or paper can be coated or infused with a metal.
- Protecting the photo detector 11335 from EMI allows the magnetometer to be more sensitive because the reduction in EMI reduces the amount of noise in the signal received from the photo detector 11335.
- protecting the photo detector 11335 from EMI protects the fidelity of the magnetometer because the signal received from the photo detector 11335 is more accurate. That is, protecting the photo detector 11335 from EMI helps to ensure that a reliable and accurate signal is received from the photo detector 11335 because there is less noise in the signal.
- the noise may include a direct current (DC) offset.
- the light pipe 11325 can be made of any suitable material.
- the light pipe 11325 can be made of quartz, silica, glass, etc.
- the light pipe 11325 is made of optical glass such as BK7 or BK9 optical glass. In alternative embodiments, any suitable material can be used.
- one or more of the faces of the light pipe 11325 can include a filter.
- the face of the light pipe 11325 can filter out non-green light and allow green light to pass through the light pipe 11325, for example, to the diamond 11315.
- light from diamond can pass through a face of the light pipe 11325 that filters out non- red light and permits red light to pass through the light pipe 11325 to the photo detector 11335.
- any suitable filtering mechanism can be used.
- Figs. 113B and 113C are isometric views of a light pipe and a shield in accordance with illustrative embodiments. In alternative embodiments, additional, fewer, and/or different elements may be used. As shown in Fig. 113B, the light pipe 11325 is surrounded axially by the shield 11345. In an illustrative embodiment, the light pipe 11325 and the shield 11345 are coaxial.
- the cross-sectional shape of the light pipe 11325 can be any suitable shape. In the embodiment illustrated in Fig. 113B, the cross-sectional shape of the light pipe 11325 is circular. In the embodiment illustrated in Fig.
- the cross-sectional shape of the light pipe 11325 is octagonal.
- the cross-sectional shape of the light pipe 11325 can be triangular, square, rectangular, or any other suitable shape.
- the cross-sectional shape of the shield 11345 can be any suitable shape.
- the outer shape of the shield 11345 is suited to fit against the wall of a housing that houses the diamond 11315, the photo detector 11335, the light pipe 11325, etc.
- the length of the light pipe 11325 is the same as the length of the shield 11345.
- the light pipe 11325 can be longer than the shield 11345.
- the light pipe 11325 may extend beyond the end surface of the shield 11345 at one or both ends.
- the shield 11345 is one inch long.
- the shield 11345 can be shorter or longer than one inch long.
- the shield 11345 can be longer.
- the light pipe 11325 can be two inches long.
- the light pipe 11325 can be shorter or longer than two inches long.
- the light pipe 11325 can be a length suitable to fit within a housing or arrangement of elements.
- the light pipe 11325 can be tapered along the length of the light pipe 11325.
- the diameter of the light pipe 11325 at one end can be large than the diameter of the light pipe 11325 at the opposite end. Any suitable ratio of diameters can be used.
- a light pipe 11325 can be used to transmit light from the light source 11305, which can be a light emitting diode, to the diamond 11315.
- Using a tapered light pipe 11325 can help to focus the light exiting the light pipe 11325 to enter the diamond 11315 at a more perpendicular angle than if a non-tapered light pipe 11325 were to be used.
- the narrow end can be adjacent to the light source 11305 and the wide end can be adjacent to the diamond 11315.
- the size of the aperture in the middle of the shield 11345 can be sized to block one or more particular frequencies of EMI.
- the diameter of the light pipe 11325 can be between five and six millimeters. In alternative embodiments, the diameter of the light pipe 11325 can be less than five millimeters or greater than six millimeters.
- the light pipe 11325 is sized to have a cross-sectional area that is the same size or slightly larger than a cross-sectional diameter of the diamond 11315. In such embodiments, the light pipe 11325 is sized to capture as much of the light emitted from the diamond 11315 as possible while minimizing the inner diameter of the shield 11345 (and, therefore, maximizing the shielding effect of the shield 11345).
- the light pipe 11325 can evenly distribute the light over the surface area of the diamond 11315 or the photo detector 11335.
- the light pipe 11325 can prevent the light from diverging.
- the light pipe 11325 can be used in place of a lens.
- the outer diameter of the shield 11345 can be any suitable size.
- the outer diameter of the shield 11345 can be sized to block or attenuate electromagnetic signals from the diamond apparatus thereby protecting the photo detector.
- the light pipe 1 1325 passes through the shield 11345. That is, the shield 11345 surrounds the light pipe 11345 along at least a length of the light pipe 11325. In some embodiments, the shield 11345 surrounds the length of the light pipe 11325.
- Fig. 114 is a block diagram of a magnetometer with two light pipes in accordance with an illustrative embodiment.
- An illustrative magnetometer 11400 includes two light pipes 11325, two shields 11345, a diamond 11315, a photo detector 11335, and a photo detector 11350.
- additional, fewer, and/or different elements may be used.
- the magnetometer 11400 includes a light source 1 1305 that sends source light 11310 into a light pipe 11325. Some of the light transmitted from the light source 11305 can be sensed by the photo detector 11350. In some embodiments, the light sensed by the photo detector 11350 is transmitted through the light pipe 11325. In alternative embodiments, the light sensed by the photo detector 11350 does not travel through the light pipe 11325. As discussed above with regard to the magnetometer 11300, the diamond 1 1315 may be associated with electrical components that emit EMI that may interfere with the performance of the photo detector 11350. In such instances, one of the shield 11345 may be placed between the diamond 11315 and the photo detector 11350. Light from the light source 11305 may travel through the light pipe 11325, through the hole in the shield 11345, and into the diamond 11315.
- a shield 11345 may be used to protect the photo detector 11335 from EMI emitted from circuitry associated with the diamond 11315.
- the magnetometer 11400 includes a shield 11345 on either side of the diamond 11315 and the electrical components associated with the diamond 11315.
- Fig. 115 is a block diagram of a magnetometer with two light pipes in accordance with an illustrative embodiment.
- the magnetometer 1 1500 includes a light source 11305, a diamond 11315, two light pipes 11325 with associated shields 11345, and two photo detectors 11335.
- additional, fewer, and/or different elements may be used.
- the source light 11310 from the light source 11305 passes through the diamond 11315.
- the light that enters the diamond 11315 can be split and can exit the diamond 11315 in two streams of modulated light 11320.
- the two streams of modulated light 11320 are in opposite directions.
- the two streams of modulated light 11320 are in any suitable orientation to one another.
- the two streams of modulated light 11320 exit the diamond 11315 in directions orthogonal to the direction in which the source light 11310 enters the diamond 11315.
- Fig. 115 illustrates a magnetometer with two light streams exiting the diamond 11315.
- the magnetometer can be used with three or more light streams that exit the diamond 11315.
- the diamond 11315 is a cube, light can enter the diamond 11315 on one of the six sides.
- up to five light streams can exit the diamond 11315 via the five other sides.
- Each of the five light streams can be transmitted to one of five photo detectors 11335.
- Using two or more light streams that exit the diamond 11315, which are sensed by associated photo detectors 11335, can provide increased sensitivity.
- Each of the light streams contains the same information. That is, the light streams contain the same amount of red light.
- Each light stream provides one of the multiple photo detectors a sample of the light.
- multiple samples of the same light are gathered. Having multiple samples provides redundancies and allows the system to verify measurements.
- the multiple measurements can be averaged or otherwise combined. The combined value can be used to determine the magnetic field applied to the diamond.
- Fig. 116 is a flow diagram of a method for measuring a magnetic field in accordance with an illustrative embodiment.
- additional, fewer, and/or different operations may be performed.
- the use of a flow chart and arrows is not meant to be limiting with respect to the order or flow of operations.
- one or more of the operations can be performed simultaneously.
- light is generated by a light source. Any suitable light source can be used. For example, lasers or light emitting diodes can be used. In some embodiments, sunlight or environmental light can be used as the light source. In an illustrative embodiment, the light generated by the light source is green light or blue light.
- a filter can be used to filter out undesirable light frequencies (e.g., red light).
- light from the light source is sensed.
- the light can be sensed using a photo detector.
- the photo detector is sensitive to electromagnetic interference.
- the operation 11610 is not performed.
- light from the diamond is sensed and the sensed light signal is compared to a pre-determined reference value.
- an operation 11615 light from the light source is transmitted through a first light pipe.
- the first light pipe can be surrounded by a material that attenuates EMI.
- EMI from electrical components near the diamond can be attenuated via the material such that the photo detector is not affected by or is less affected by the EMI.
- the operation 11615 may not be performed.
- the diamond can include NV centers that are affected by magnetic fields. The amount of red light emitted from the diamond (e.g., via the NV centers) can change based on the applied magnetic field.
- a magnetic field point is determined.
- the magnetic field point is a vector with a magnitude and a direction.
- the operation 11635 includes determining a magnitude or a direction.
- the operation 11635 can include comparing the amount of green light (or any other suitable wavelength) emitted from the light source with the amount of detected red light (or any other suitable wavelength) that was transmitted through the second light pipe. In alternative embodiments, the amount of detected red light that was transmitted through the second light pipe is compared to a baseline amount. In alternative embodiments, any suitable method of determining the magnetic field point can be used.
- a light source is used to provide light to the diamond.
- the more light that is transmitted through the diamond the more light can be detected and analyzed to determine the amount of red light emitted from the diamond.
- the amount of red light can be used to determine the strength of the magnetic field applied to the diamond.
- lasers are used to provide light to the diamond. Lasers can provide concentrated light to the diamond and can focus the beam of light relatively easily.
- lasers may not be the most effective light source for all applications.
- some lasers produce polarized light. Because the axes of the NV centers may not all be oriented in the same direction, the polarized light from a laser may excite NV centers with axes oriented in one direction more effectively than NV centers with axes oriented in other directions.
- nonpolarized light may be used. The non-polarized light may affect the NV centers of different orientations (more) uniformly.
- a light source such as a light-emitting diode (LED) may be used as the light source.
- lasers that produce non-polarized light may be used. For example, helium-neon (HeNe) lasers can be used.
- lasers are relatively bulky and large compared to LEDs.
- using LEDs as the light source for a magnetometer using a diamond with NV centers may provide a more compact and versatile sensor.
- lasers user more power to produce light than do LEDs.
- LEDs may allow a power source, such as a battery, to last longer, be smaller, and/or provide less power.
- Fig. 117 is a block diagram of a magnetometer in accordance with an illustrative embodiment.
- An illustrative magnetometer 11700 includes an LED 11705, source light 11710, a diamond 11715, red light 11720, a filter 11725, filtered light 11730, a photo detector 11735, and a radio frequency transmitter 11745.
- additional, fewer, and/or different elements may be used.
- the LED 11705 can be used to produce the source light 11710.
- any suitable light source can be used to produce the source light 11710.
- a light source that produces non-polarized light can be used.
- any suitable LED may be used.
- the LED 11705 can emit primarily green light, primarily blue light, or any other suitable light with a wavelength shorter than red light.
- the LED 11705 emits any suitable light, such as white light.
- the light can pass through one or more filters before entering the diamond 11715.
- the filters can filter out light that is not the desired wavelength.
- the source light 11710 is emitted by the LED 11705.
- the source light 11710 can be any suitable light.
- the source light 11710 has a wavelength of between 500 nanometers (nm) and 600 nm.
- the source light 11710 can have a wavelength of 532 nm (e.g., green light), 550 nm, or 518 nm.
- the source light 11710 can be blue (e.g., with a wavelength as low as 450 nm).
- the source light 11710 can have a wavelength lower than 450 nm.
- the source light 11710 can be any color of visible light other than red.
- An illustrative diamond 11715 includes one or more nitrogen vacancy centers (NV centers). As explained above, each of the NV centers' axes can be oriented in one of multiple directions. In an illustrative embodiment, each of the NV centers are oriented in one of four directions. In some embodiments, the distribution of NV centers with any particular axis direction is even throughout the diamond 11715.
- the diamond 11715 can be any suitable size. In some embodiments, the diamond 1 1715 is sized such that the source light 11710 provides a relatively high light density. That is, the diamond 11715 can be sized such that all or almost all of the NV centers are excited by the source light 11710. In some instances, the LED 11705 emits less light than a laser. In such instances, a thinner diamond can be used with the LED 11705 to ensure that all or nearly all of the NV centers are excited.
- the diamond can be
- the source light 11710 travels a shorter distance through the diamond 11715.
- a magnet 11740 can be used to provide a magnetic field.
- the NV centers can cause the amount of red light emitted from the diamond 11715 to be changed.
- the source light 11710 is pure green light and there is no magnetic field applied to the diamond 11715
- the red light 11720 which is emitted from the diamond 11715
- the amount of red light 11720 varies in intensity.
- a magnetic field applied to the diamond 11715 can be measured.
- the red light 11720 emitted from the diamond 11715 can be any suitable wavelength.
- the radio frequency transmitter 11745 can be used to transmit radio waves to the diamond 11715.
- the amount of red light emitted from the diamond 11715 changes based on the frequency of the radio waves absorbed by the diamond 11715.
- the amount of red light sensed by the photo detector 11735 may change.
- the strength of the magnetic field applied to the diamond 11715 by the magnet 11740 can be determined.
- a photo detector 11735 is used to receive the light emitted from the diamond 11715.
- the photo detector 11735 can be any suitable sensor configured to analyze light emitted from the diamond 11715.
- the photo detector 11735 can be used to determine the amount of red light in the red light 11720.
- some embodiments include a filter 11725.
- the filter 11725 can be configured to filter the red light 11720.
- the filter 11725 can be a red filter that permits red light to pass through the filter 11725 but blocks some or all of non-red light from passing through the filter 11725.
- any suitable filter 11725 can be used.
- the filter 11725 is not used.
- the red light 11720 emitted from the diamond 11715 passes through the filter 11725, and the filtered light 11730 (which is emitted from the filter 11725) travels to the photo detector 11735.
- greater sensitivity may be achieved because the photo detector 11735 detects only the light of interest (e.g., red light) and other light (e.g., green light, blue light, etc.) does not affect the sensitivity of the photo detector 11735.
- the light of interest e.g., red light
- other light e.g., green light, blue light, etc.
- Fig. 118 is an exploded view of a magnetometer in accordance with an illustrative embodiment.
- An illustrative magnetometer 11800 includes an LED 11805, a housing 11810, a source light photo sensor 11815, a mirror tube assembly 11820, electromagnetic glass 11825, a concentrator 11830, retaining rings 11835, a diamond assembly 11840, a concentrator 11845, a modulated light photo sensor 11850, a sensor plate 11855, and a lens tube coupler 11860.
- additional, fewer, and/or different elements may be used.
- the embodiment illustrated in Fig. 118 is meant to be illustrative only and not meant to be limiting with respect to the orientation, size, or location of elements.
- An illustrative LED 11805 includes a heat sink that is configured to dissipate into the environment heat created by the LED 11805.
- a portion of the LED 11805 e.g., a cylindrical portion
- the mirror tube assembly 1 1820 Adjacent to the LED 11805 within the housing 11810 is the mirror tube assembly 1 1820.
- the mirror tube assembly 11820 is configured to focus the light from the LED 11805 into a concentrated beam.
- the source light photo sensor 11815 is configured to receive a portion of the light emitted from the LED 11805.
- the source light photo sensor 11815 can include a green filter.
- the source light photo sensor 11815 receives mostly or all green light. In embodiments in which the source light photo sensor 11815 is used, the amount of green light sensed by the source light photo sensor 11815 can be compared to the amount of red light sensed by the modulated photo sensor 11850 to determine the magnitude of the magnetic field applied to the diamond assembly 11840. As discussed above, in some embodiments, the source light photo sensor 11815 may not be used. In such embodiments, the amount of red light sensed by the modulated photo sensor 11850 can be compared to a baseline amount of red light to determine the magnitude of the magnetic field applied to the diamond assembly 11840.
- electromagnetic glass 11825 can be located between the source light photo sensor 11815 and the diamond assembly 11840.
- the diamond assembly 11840 can emit electromagnetic interference (EMI) signals.
- EMI electromagnetic interference
- the source light photo sensor 11815 can be sensitive to EMI signals. That is, in such instances, the source light photo sensor 11815 performs better when there is less EMI affecting the source light photo sensor 11815.
- the electromagnetic glass 11825 can allow light to pass through the electromagnetic glass 11825, but inhibit transmission of electromagnetic signals. Any suitable electromagnetic glass 11825 can be used. In alternative embodiments, any suitable EMI attenuator can be used.
- the concentrator 11830 can be configured to concentrate light from the mirror tube assembly 11820 (and/or the electromagnetic glass 11825) into a more narrow beam of light.
- the concentrator 11830 can be any suitable shape, such as parabolic.
- the diamond assembly 11840 can include a diamond with one or more NV centers.
- the concentrator 11830 can concentrate light from the LED 11805 into a beam of light with a cross-sectional area that is similar to the cross-sectional area of the diamond. That is, the light from the LED 11805 can be concentrated to most effectively flood the diamond with the light such that as much of the light as possible from the LED 11805 passes through the diamond and/or such that as many NV centers as possible are excited by the light.
- the concentrator 11830 may include a ring mount that is configured to hold the concentrator 11830 at a secure location within the housing 11810.
- the diamond assembly 11840 can include any suitable components.
- the diamond assembly 11840 can include a diamond.
- the diamond can be located at the center of the diamond assembly 11840.
- the diamond assembly 11840 may also include one or more circuit boards that are configured to modulate electromagnetic signals applied to the diamond.
- the diamond assembly 11840 includes a Helmholtz coil.
- a three-dimensional Helmholtz coil can be used counteract or cancel unwanted magnetic fields from affecting the diamond.
- the circuit boards or other electronics can emit EMI signals.
- the diamond assembly 11840 includes a red filter that allows red light emitted from the diamond to pass through to the modulated photo sensor 11850.
- the red filter can be located at any suitable location between the diamond and the modulated photo sensor 11850. In yet other embodiments, the red filter may not be used.
- the retaining rings 11835 can be used to hold one or more of the elements of the magnetometer 11800 within the housing 11810. Although Fig. 118 illustrates two retaining rings 11835, any suitable number of retaining rings 11835 may be used. In some embodiments, the retaining rings 11835 may not be used.
- the concentrator 11845 is configured to
- the concentrator 11830 can be configured to concentrate light into a beam that has the same or a similar cross-sectional area as the modulated photo sensor 11850.
- the concentrator 11845 can be configured to focus as much light as possible from the diamond assembly 11840 to the modulated photo sensor 1 1850.
- electromagnetic glass 11825 can be located between the diamond assembly 11840 and the modulated photo sensor 11850 to shield the modulated photo sensor 11850 from EMI signals emitted from the diamond assembly 11840.
- the sensor plate 11855 can be used to hold the modulated photo sensor 11850 in place such that the modulated photo sensor 11850 receives the concentrated light beam from the concentrator 11845 (and/or the diamond assembly 11840).
- a lens tube coupler 11860 may be used as an end cap to the housing 11810, thereby holding the various elements in place inside the housing 11810.
- Fig. 119 is a flow diagram of a method for detecting a magnetic field in accordance with an illustrative embodiment.
- additional, fewer, and/or different operations may be performed.
- the use of a flow diagram and arrows is not meant to be limiting with respect to the order or flow of operations.
- one or more of the operations may be performed simultaneously.
- a light emitting diode Any suitable amount of power can be provided.
- a 5 milli-Watt (mW) LED can be used.
- the LED can be powered by two or more AA batteries.
- the LED can use more or less power.
- the amount of power provided to the LED is modulated based on a particular application.
- the operation 11905 includes providing pulsed power to the LED to cause the LED to alternately lighten and darken. In such embodiments, any suitable frequency and/or pattern can be used.
- the operation 11905 can include causing any suitable device to emit non-polarized light.
- an operation 11910 light emitted from the LED is sensed. Sensing the light from the LED can include using a photo detector. The operation 11910 can include determining an amount of green light emitted from the LED. In some embodiments, the operation 11910 is not performed.
- light from the LED is focused into a diamond.
- the diamond can include one or more NV centers.
- the light can be focused as to excite as many of the NV centers as possible with the light from the LED.
- Any suitable focusing method can be used.
- lenses or light pipes can be used to focus light from the LED to the diamond.
- light from the diamond is focused to a photo detector.
- Light from the LED passes through the diamond, is modulated by the diamond, and is emitted from the diamond.
- the light emitted from the diamond is focused to a detector such that as much light emitted from the diamond as possible is detected by the photo detector.
- the light from the diamond is sensed by the photo detector.
- the operation 11925 includes determining the amount of red light emitted from the diamond.
- a magnetic field applied to the diamond is determined.
- the amount of red light emitted by the diamond is compared to the amount of green light emitted from the LED to determine the magnetic field.
- the amount of red light emitted from the diamond is compared to a baseline quantity of red light.
- any suitable method of determining the magnetic field applied to the diamond can be used.
- noise in the light emitted from the LED can be compensated for.
- noise in the light emitted from the LED can be detected by a photo detector, such as the photo detector used for the operation 11910.
- Noise in the light emitted from the LED passes through the diamond and is sensed by the photo detector that senses light emitted from the diamond, such as the photo detector used for the operation 11925.
- amount of light detected in the operation 11910 is subtracted from the light detected in the operation 11930. The result of the subtraction is the changes in the light caused by the diamond.
- Figure 120 is a schematic illustrating a portion of a DNV sensor 12000 with a dual
- the magnetic sensor shown in Figure 6 used a single RF excitation source 630.
- Figure 120 uses two separate RF elements.
- the diamond 12020 is used to provide the microwave RF to the diamond 12020.
- the diamond 12020 is sandwiched between the two RF elements 12004 and 12008.
- a space 12006 can be used between the RF elements 12004 and 12008 to all light ingress or egress.
- light can enter or leave the sensor via spaces 12002 and/or 12010. Accordingly, light can be shown onto the diamond 12020 from various positions and photo-sensors, such as photodiodes, can be used in various locations to collect the red light that exits the diamond 12020.
- FIG. 121 is a view of an enclosed DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- the RF elements are located on two circuit boards 12112.
- the diamond not shown in Figure 121 but shown as 12320 in Figure 123, is located between the circuit boards 12112.
- the RF element can include one or more spiral elements with n number of loops.
- each RF element can include a single spiral with 2, 3, 4, etc., loops.
- the RF element can include multiple spirals, such as 2, 3, 4, 5, etc., that are stack on top of one another. In these
- each RF element contains five spirals each having four loops. These elements can be made using fusion bonded multilayer dielectrics.
- a spacer 12114 separates the individual circuit boards.
- the sensor assembly also includes retaining rings 12108 and a plastic mounting plate 12116.
- the illustrated sensor assembly is contained with a lens tube 12104 such as a 1 inch ID lens tube.
- the sensor assembly also contains a direct-current connector 12106 that can be used to provide power to the sensor assembly.
- the assembly also includes a photo sensor 12140.
- the RF elements are fed from a RF feed cable 12102, that can be a coaxial cable.
- the RF feed cable 12102 attaches to the assembly via an RF connector 12110.
- a second RF feed cable can be used.
- each RF element is fed using a separate RF signal.
- Figures 122A and 122B are schematics of an assembly portion of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- the illustrated assembly portion can be used in the implementation illustrated in Figure 121.
- Figure 122A illustrates one side of the assembly. This side includes an ingress portion 12202 that allows light to reach the diamond that is between the RF elements. In this implementation, the ingress portion is in the center of the assembly. In other implementations, the ingress portion can be located between the RF elements along the diameter of the assembly.
- Figure 122B illustrates the opposite side of the assembly shown in Figure 122 A.
- the circuit board elements that contain the RF elements 12214 are shown along with the space 12212 that separates the RF elements.
- a RF connector 12210 is shown that provides the RF source signal to the RF elements.
- a photo sensor 12240 is also shown in the middle of the assembly. Underneath the photo sensor is an egress portion. As light is shined through the ingress portion 12220, the light will pass through the diamond, not shown, that is contained within the assembly between the two RF elements. The light will pass through the diamond and exit the opposite side of the assembly and reach the photo sensor 12240. The photo sensor can then measure property of the light, such as the light's wavelength.
- Figure 123 is a cross-section of a portion of a DNV sensor with a dual RF
- the portion of the DNV sensor is the same as the portion of the assembly illustrated in Figures 122A and 122B and can be used in the DNV sensor illustrated in Figure 121.
- the cross section of the sensor assembly is done as illustrated on the portion of the assembly 12330.
- the diamond 12320 is now visible as located between a top RF element 12304 and a bottom RF element 12308.
- a spacer 12310 separates the RF elements 12304 and 12308.
- the ingress portion of the assembly is shown directly above the diamond 12320. Light can enter the assembly through this ingress portion and pass through the diamond 12320. The light that exits the diamond can pass through the egress portion of the assembly and reach the photo sensor 12340. Additional egress portions through the space can also be used. Thus, light can be collected from the face of the diamond and/or through the edges of the diamond.
- FIG 124 is a schematic illustrating a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- the DNV sensor includes a light source and focusing lens assembly 12402.
- the light source can various light sources such as a laser or LED.
- the light source is an LED.
- a heatsink 12408 is used to bleed away the heat from the light source.
- the DNV assembly is housed in an element structure 12406 and described in greater detail below. In the illustrated implementation, the element structure 12460 is fixed within the sensor.
- two RF cables 12404 are provided to the DNV assembly.
- the RF signal provided to the RF elements can therefore be the same or the feed signals can be different.
- the RF signals are different based upon the configuration of the elements of the NV diamond assembly. For example, if one RF element is slightly further from the NV diamond compared to the other RF element, different RF signals can be used to take into account the differences in distances.
- Figure 125 is a cross-section of a DNV sensor of Figure 124 with a dual RF arrangement in accordance with some illustrative implementations.
- the DNV sensor includes a light source heatsink 12508.
- the light source and focusing lens assembly includes an LED 12502 and one or more focusing lenses 12504. Light from the LED 12502 is focused, using the one or more focusing lenses 12504, onto an NV diamond 12520. In this implementation, light enters an edge of the NV diamond 12520 and is ejected from one or more faces on the NV diamond 12520.
- photo-sensor assemblies 12540 and 12542 located above and below the NV diamond. These photo-sensor assemblies 12540 and 12542 can include photodiodes that detect the light that is ejected from the NV diamond 12520.
- the NV diamond is located between two RF elements 12530 and 12532. These RF elements provide a microwave RF signal uniformly across the NV diamond.
- Light is ejected through the top and bottom face of the NV diamond 12520 and travels to one of the photo-sensor assemblies 12540 and 12542. Between the photo-sensor assemblies 12540 and 12542 there are attenuators 12534. The attenuators reduce or eliminate the RF generated by the RF elements to avoid interference with other elements of the sensor. Ejected travels through a light pipe 12536 that is between each photo-sensor assembly and the NV diamond. In various implementations, at least a portion of the light pipe is located within the attenuators.
- Figure 126 is a schematic illustrating a DNV sensor with a dual RF arrangement and laser mounting in accordance with some illustrative implementations.
- the light source has been changed to a laser which is included in a laser and focusing lens assembly 12602.
- the NV diamond is housed in an adjustable structure.
- a rotatable adjustment assembly 12604 allows the NV diamond to be rotated.
- An x-y-z adjustment assembly 12606 allows the NV diamond and various elements to be positioned in 3D space. As the NV diamond's position can be changed, there is an x-y adjustment assembly 12604 that is used to adjust the ingress of light into the NV diamond assembly.
- Figure 127 is a cross-section of a DNV sensor illustrated in Figure 126 with a dual RF arrangement and laser mounting in accordance with some illustrative implementations.
- An NV diamond 12720 is located between two RF elements 12732.
- Light pipes 12730 provide a path for light that exits the faces of the NV diamond 12720 to travel from the NV diamond to one of two photo-sensing assemblies 12740.
- at least a portion of each light pipe 12730 is housed with an attenuator 12734.
- the DNV sensor does not contain the attenuators 12734.
- the rotatable adjustment assembly allows the NV diamond and related elements such as the RF elements to be rotated within the NV diamond assembly. This can allow the light ingress portion of the diamond to be altered as well as altering where light exiting the NV diamond 12720 is collected. For example, the NV diamond can be rotated to allow light to enter the diamond at an edge or at a face.
- the x-y-z adjustment assembly allows the position of the NV diamond and related elements within the NV diamond assembly to be changed. This assembly allows for the control of where the light will enter the NV diamond as well as where the ejected light will be collected.
- the x-y adjustment assembly allows the light source to also be moved such that the light can enter the NV diamond assembly regardless of the rotation and position of the NV diamond within the NV diamond assembly.
- Figures 128 A and 128B are schematics of an assembly portion of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- Figure 128A illustrates one side of the assembly portion of the DNV sensor and
- Figure 128B illustrates the opposite side of the assembly.
- the assembly includes two RF elements, a top RF element 12804 and a bottom RF portion 12806. These RF elements can be fed using the same RF signal or can be fed separate RF signals via the RF connector 12802 and RF connector 12812.
- the NV diamond is not shown, but is located between the RF elements 12804 and 12806. Light from the light source enters the diamond via a space between the RF elements 12804 and 12806. Light is ejected from the NV diamond via either light egress portion 12808 and 12810.
- Figures 129 A and 129B are schematics of an assembly portion of a DNV sensor with a dual RF arrangement in accordance with some illustrative implementations.
- Figures 129A and 129B further illustrate the assembly portion of the DNV sensor illustrated in Figures 128 A and 128B.
- the NV diamond 12920 is now shown located within a spacer or a diamond alignment plate, such as a plastic diamond alignment plate.
- light enters between the RF elements.
- light can enter the diamond via the light ingress portion 12910 of the assembly.
- the RF elements 12902 and 12904 are shown in Figure 129A along with the RF feed cable connectors 12906 and 12908.
- the disclosed system includes a reduced instruction set (RISC) processor that is coupled to a configurable signal synthesizer.
- RISC reduced instruction set
- the configurable signal synthesizer may be configured to perform single-cycle commands for frequency shifts, digital outputs, and initial synchronous preprocessing of received data such that the digital control, acquisition, and waveform generation may be performed on the same clock cycle for synchronization.
- the specially designed single-cycle operations of the subject technology may provide more precise and deterministic timing for digital control, acquisition, and waveform generation.
- the RF waveform generation and digital control outputs are coordinated in configurable patterns that can range from simple sequences to complex adaptive control patterns.
- FIG. 130 is a block diagram depicting an overview of an implementation of a single- cycle synthesis, control, and acquisition system 13000.
- the system 13000 is configured to control multiple RF signals and digital output signals for magnetometry, such as for a diamond nitrogen vacancy (DNV) sensor.
- DNV diamond nitrogen vacancy
- the system 13000 may be
- the system 13000 is implemented as a single single-cycle integrated circuit for RF waveform synthesis, digital control, and acquisition. A more detailed implementation of the single-cycle synthesis, control, and acquisition system is shown as the system 13100 in FIG. 131.
- the system 13000 includes a host interface 13010 that receives DNV sensing information from an external system, such as a data processing or acquisition system (not shown), and is communicatively coupled to a program counter 13020, a program memory 13030, and an acquisition processor 13080.
- the host interface 13010 may be coupled to a data processing system, such as system 13200 of FIG. 132, that can communicate with the system 13000 via the host interface 13010.
- the data processing system can output instructions, such as control instructions from the reduced instruction set, to the system 13000 via the host interface 13010 for the program memory 13030.
- the data acquisition system can also receive output from the acquisition processor 13080 via the host interface 13010, such as pulse processed data from a DNV sensor.
- the host interface 13010 provides communication between the components of the system 13000 and an external system.
- a more detailed depiction of the host interface 13010 is shown as host interface 13110 in FIGS. 131 and 132 A.
- the host interface 13010 is communicatively coupled to the program counter 13020, which is in communication with the program memory 13030 and thejump control 13070.
- a more detailed implementation of the program counter 13020 is shown as program counter 13120 in FIGS. 131 and 132B.
- a more detailed implementation of the program memory 13030 is shown as program memory 13130a, 13130b in FIGS. 131 and 132C.
- a more detailed implementation of the jump control 13070 is shown as jump control with delay 13140a and thejump control 13140b in FIGS. 131 and 132D-E.
- the program memory 13030 provides outputs through a decoder 13040 to a RF waveform generator of the CORDIC (Coordinate Rotation Digital Computer) synthesis 13050 for generating the RF waveform to be applied, the digital control 13060 for controlling a laser on/off timing, and a jump control 13070.
- Thejump control 13070 provides feedback to the program counter 13020.
- the CORDIC synthesis 13050 provides digital up or down conversion and can have a run-time configurable base frequency and increment for the RF waveform generation.
- the RF waveform generator of the CORDIC synthesis 13050 utilizes a frequency base value and a frequency increment that outputs a single value for a slope of a ramp that is used by an accumulator to generate a sine wave for the RF waveform.
- the sine wave is processed through an upconverter to generate the RF waveform signal to be applied to the magnetometry
- the CORDIC synthesis 13050 may phase shift the RF waveform.
- an analog or digital switch may be used for arbitrary waveform generation.
- a more detailed implementation of the RF waveform generator and CORDIC synthesis 13050 is shown as RF waveform generator 13150 in FIGS. 131 and 132F.
- the digital control 13050 provides timing control for a number of aspects of a magnetometry component, such as a DNV sensor.
- the digital control 13050 includes RF gating or switches and may include additional general inputs or outputs for additional control.
- the digital control 13050 may output signals to control the activation of a magnetometry component, such as a laser for exciting a nitrogen vacancies of a DNV sensor.
- the digital control can also convert the CORDIC output to 0 via a multiplexer (MUX) such that no RF signal is applied to the DNV sensor.
- the digital control 13050 can be used for an acousto- optic modulator (AOM) to control optic pulsing of the laser and/or can be used for phase shift control.
- the digital control 13050 may further provide an output to an I/Q component, such as a digital I/Q.
- a more detailed implementation of the digital control 13060 is shown as digital control 13160 in FIGS. 131 and 132G.
- the acquisition processor 13080 provides initial synchronous preprocessing of data received from a magnetometry component, such as data received from a photo detector of a DNV sensor.
- the acquisition processor 13080 can include two coherent channels for
- the channels may be chainable up to four.
- data received by the acquisition processor 13080 may be at a rate of 50 MHz, 100 MHz, 200 MHz, or greater.
- the acquisition processor can preprocess the data to reduce the size of the data outputted.
- the acquisition processor 13080 synchronously gathers samples from a magnetometry component, such as the photo detector of a DNV sensor, and preprocesses the data, such as decimation of the data.
- the acquisition process 13080 may include a digital output to trigger an accumulator for a predetermined number of clock cycles and then will subtract from two integration windows for processing of the data. By providing a consistent trigger based on a single-cycle of the system 13000, the preprocessing of the acquired data can be more consistent, thereby increasing sensitivity and reducing noise in the acquired data from inconsistent triggers.
- the acquisition processor 13080 may include a digitally controllable offset for effects similar to a DC block or AC coupling. A more detailed implementation of the acquisition processor 13080 is shown as acquisition processor 13170 in FIGS. 131 and 132H.
- the system 13000 is configured for single-cycle instructions for the components of the system 13000 such that the RF waveform generator of the CORDIC synthesis 13050 for generating the RF waveform, the digital control 13060 for controlling the laser on/off timing, and the acquisition processor 13080 operate on the same clock cycle.
- a main counter (not shown) drives the RF waveform generation while the program counter 13020 allows for delays to be implemented for the digital control 13050 and the acquisition processor 13080.
- the single-cycle can provide laser and/or microwave deterministic timing control for coordination of the CORDIC synthesis 13050, the digital control 13060, and the acquisition processor 13080.
- the single-cycle tightly ties in the digital control 13060 for controlling the laser and acquisition processor with the RF waveform generation of the CORDIC synthesis 13050.
- the single-cycle permits synchronous stepped-frequency complex waveform synthesis by the CORDIC synthesis 13050 and permits coordinated large-range frequency retuning (e.g., >1 GHz) without losing base time.
- the single-cycle system 13000 can also provide synchronous reduced instruction set program control of the frequency for the RF waveform synthesis.
- the system 13000 of FIG. 130 with a single-cycle also reduces redundant components compared to systems that utilize separate components for the RF waveform generator, digital control, and/or acquisition processor.
- the single- cycle synthesis, control, and acquisition system 13000 may also be configured for two-cycle implementations as well.
- the system 13000 can utilize a reduced instruction set (RISC) engine that issues one instruction per clock cycle, including for conditional branching.
- the reduced instruction set can include commands for an unconditional jump (jmp), a conditional jump (cjmp), setting of a loop counter (setc ⁇ counter value>), setting of a frequency (set/ value>), setting of a digital control output field (seto ⁇ output field value>), a frequency increment (incf ⁇ increment value>), and a delay for a specified cycle count (del ⁇ cycle count value>).
- the single-cycle synthesis, control, and acquisition system 13000 can provide lock-step precision for laser on/off timing via the digital control 13060, sequenced microwave waveform synthesis and delivery via the RF waveform generator and CORDIC synthesis 13050, data acquisition via the acquisition processor 13070, and laser and /or microwave deterministic timing control.
- the single-cycle synthesis, control, and acquisition system 13000 can facilitate effective experimentation by enabling rapid coordination of excitation signals and tuning across broad frequency ranges without losing timing.
- Not all of the depicted components may be required, however, and one or more implementations may include additional components not shown in the figure. Variations in the arrangement and type of the components may be made, and additional components, different components, or fewer components may be provided.
- FIG. 131 is a circuit diagram illustrating an example implementation of the single-cycle synthesis, control, and acquisition system 13100.
- the single-cycle synthesis, control, and acquisition system 13100 is a dedicated hardware configured for DNV
- the reduced instruction set (RISC) engine is configured to issue one instruction per clock cycle, even for conditional branches.
- the RF waveform generator uses a run-time configurable base frequency and increment to provide the CORDIC synthesis with an RF waveform for digital up/down conversion.
- the digital control block is responsible for providing laser timing, RF gating, and additional general control input/output (I/O).
- the acquisition processor block is configured to provide two coherent channels (potentially chainable up to 4) for simultaneous red, infra-red (IR), laser, and other types of light collection.
- the acquisition processing block is further configured to synchronously collect samples and to provide digitally controllable analog offset that allows effects like DC blocking or AC coupling.
- Examples of advantageous features of the single-cycle synthesis, control, and acquisition system 13100 include, but are not limited to, single-cycle deterministic timing coordination of RF waveform generation, laser control, and data acquisition, synchronous stepped-frequency for complex waveform synthesis, synchronous RISC program control of frequency, coordinated large-range (e.g., >lGHz) frequency retuning without losing time base, and a minimal instruction set.
- the system 13000, 13100 can be incorporated into a variety of settings and configurations where DNV magnetometers are employed.
- Examples of applications of the single-cycle synthesis, control, and acquisition system 13000, 13100 include, but are not limited to incorporating the single chip into a DNV sensor, incorporating the single chip into DNV-based geolocation systems, incorporating the single chip into DNV anomaly detection systems, incorporating the single chip into covert communications systems, incorporating the single chip into distributed measure point systems, incorporating the single chip into small form factor unmanned systems for air (e.g., unmanned air vehicle (UAV), micro unmanned air vehicle ( ⁇ ), missiles), sea, underground, and surveillance (e.g., satellites, cluster satellites, etc.), incorporating the single chip into low SWAP (size, weight, and power) applications, and utilizing the single chip, single-cycle synthesis, control, and acquisition system 13000, 13100 for automatic experimental optimization.
- UAV unmanned air vehicle
- ⁇ micro unmanned air vehicle
- missiles sea, underground
- surveillance e.g., satellites, cluster satellites, etc.
- FIG. 132 is a diagram illustrating an example of a system 13200 for implementing some aspects of the subject technology.
- the system 13200 includes a processing system 13202, which may include one or more processors or one or more processing systems.
- a processor can be one or more processors.
- the processing system 13202 may include a general-purpose processor or a specific-purpose processor for executing instructions and may further include a machine-readable medium 13219, such as a volatile or non-volatile memory, for storing data and/or instructions for software programs.
- the instructions which may be stored in a machine- readable medium 13210 and/or 13219, may be executed by the processing system 13202 to control and manage access to the various networks, as well as provide other communication and processing functions.
- the instructions may also include instructions executed by the processing system 13202 for various user interface devices, such as a display 13212 and a keypad 13214.
- the processing system 13202 may include an input port 13222 and an output port 13224. Each of the input port 13222 and the output port 13224 may include one or more ports.
- the input port 13222 and the output port 13224 may be the same port (e.g., a bi-directional port) or may be different ports.
- the processing system 13202 may be implemented using software, hardware, or a combination of both.
- the processing system 13202 may be implemented with one or more processors.
- a processor may be a general-purpose microprocessor, a microcontroller, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Programmable Logic Device (PLD), a controller, a state machine, gated logic, discrete hardware components, or any other suitable device that can perform calculations or other manipulations of information.
- DSP Digital Signal Processor
- ASIC Application Specific Integrated Circuit
- FPGA Field Programmable Gate Array
- PLD Programmable Logic Device
- controller a state machine, gated logic, discrete hardware components, or any other suitable device that can perform calculations or other manipulations of information.
- a machine-readable medium can be one or more machine-readable media.
- Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (e.g., in source code format, binary code format, executable code format, or any other suitable format of code).
- Machine-readable media may include storage integrated into a processing system such as might be the case with an ASIC.
- Machine-readable media may also include storage external to a processing system, such as a Random Access Memory (RAM), a flash memory, a Read Only Memory (ROM), a Programmable Read-Only Memory (PROM), an Erasable PROM (EPROM), registers, a hard disk, a removable disk, a CD- ROM, a DVD, or any other suitable storage device.
- RAM Random Access Memory
- ROM Read Only Memory
- PROM Erasable PROM
- registers a hard disk, a removable disk, a CD- ROM, a DVD, or any other suitable storage device.
- a machine-readable medium is a computer-readable medium encoded or stored with instructions and is a computing element, which defines structural and functional interrelationships between the instructions and the rest of the system, which permit the instructions' functionality to be realized.
- Instructions may be executable, for example, by the processing system 13202 or one or more processors. Instructions can be, for example, a computer program including code for performing methods of the subject technology.
- a network interface 13216 may be any type of interface to a network (e.g., an Internet network interface), and may reside between any of the components shown in FIG. 132 and coupled to the processor via the bus 13204.
- a network e.g., an Internet network interface
- a device interface 13218 may be any type of interface to a device and may reside between any of the components shown in FIG. 132.
- a device interface 13218 may, for example, be an interface to an external device (e.g., USB device) that plugs into a port (e.g., USB port) of the system 13200.
- the device interface 13218 may be the host interface of FIG. 130, where at least some of the functionalities of the apparatus of FIG. 130 are performed by the processing system 13202.
- the controller 680 may be configured to compute an accurate estimation of the true orientation of the NV diamond lattice, which can be performed on-site as a calibration method prior to use. This information can be subsequently used to accurately recover the full vector information of an unknown external magnetic field acting on the system 600.
- a desired geospatial coordinate reference frame relative to the system 600 by which measurement of the total magnetic field vector will take place is established.
- a Cartesian reference frame having ⁇ x, y, z ⁇ orthogonal axes may be used, but any arbitrary reference frame and orientation may be used.
- FIG. 133A shows a unit cell 13300 of a diamond lattice having a "standard" orientation. The axes of the diamond lattice will fall along four possible directions. Thus, the four axes in a standard orientation relative to the desired coordinate reference frame may be defined as unit vectors corresponding to:
- the four vectors of equation (b l) may be represented by a single matrix A s , which represents the standard orientation of the unit cell 13300:
- the angle between axis i and axis j may also be given by the (i,j) tfl row of the following:
- FIG. 133B is a unit cell 13300' that represents an arbitrarily placed NV diamond material having unknown axes orientation with respect to the coordinate reference frame.
- the arbitrary orientation shown in FIG. 133B may be obtained through a rotation and/or reflection of the standard orientation matrix.
- This can be achieved by applying a transformation matrix R, which is defined as a general 3x3 matrix representing the three-dimensional, orthogonal Cartesian space and is, at this stage, unknown.
- b E E 3 l represents the magnetic field vector acting inside the sensor system, expressed in Cartesian coordinates relative to the coordinate reference frame;
- a T b represents the projection of the magnetic field vector onto each of the four, arbitrarily-placed NV center diamond lattice axes;
- n E E 4 l represents the sensor noise vector;
- m E E 4 l represents the measurement vector, where the i th element represents the estimated projection of the magnetic field onto the sensor axis i.
- the measurement vector has been converted from the DNV sensor's native units (in terms of microwave resonance frequency) into the units of magnetic field strength.
- represents the element-wise absolute value of A T b + n, rather than its determinant.
- equation (b6) [00761] Based on equation (b9), the generalized least squares solution of equation (b6) may now be written as:
- b For a perfect NV diamond material 620 having no defects (e.g., lattice misalignments, impurities, etc.) and no sensor noise, b should be equal to b. However, in an imperfect system, it is possible to utilize a performance metric to determine the error associated with the
- the magnitude of the true magnetic field may be used to normalize the metric to give a consistent metric even in the presence of a changing true magnetic field:
- the measurement vector magnitude may be used to normalize the metric:
- a permanent magnet e.g., the first magnetic field generator 670
- coils e.g., the second magnetic field generator 675
- b bias the required bias or control magnetic field
- any b bias vector that sufficiently separates the four dips may suffice for the determination of the unknown orientation of the diamond lattice, thus increasing the viable b bias vectors appropriate for this step.
- Sufficient spectral dip separation may depend on the width of the dips and the planned magnitude of the calibration magnetic fields (described below). The width of the dips varies, depending on diamond composition and sensor laser and/or RF excitation mechanisms. Based on the resulting widths due to inherent sensor characteristics, the magnitude and orientation should be sufficient to ensure that the anticipated maximum spectral shifts that will occur due to the calibration tests will maintain sufficient separation between neighboring Lorentzian dips.
- FIG. 134 shows a step for determining a viable b bias vector field.
- the first magnetic field generator 670 may be arbitrarily placed in one or more positions and/or orientations such that multiple magnetic fields are applied to the diamond having an unknown orientation 13300'. Measurements of the fluorescence intensity response are taken for each position and/or orientation of the first magnetic field generator 670. Once a fluorescence intensity response 13400 is produced that adequately separates out the four Lorentzian pairs, the position of the first magnetic field generator 670 is maintained and the process may proceed to calibration tests. In other embodiments, the separation process may be performed by the second magnetic field generator 675.
- the controller 680 may be configured to control the second magnetic field generator 675 to generate multiple magnetic fields until the desired separation is produced.
- the first and/or second magnetic field generators may be affixed to a pivot assembly (e.g., a gimbal assembly) that may be controlled to hold and position the first and/or second magnetic field generators to a predetermined and well- controlled set of orientations, thereby establishing the desired Lorentzian separation and/or calibration magnetic fields (described below).
- the controller 680 may be configured to control the pivot assembly having the first and/or second magnetic field generators to position and hold the first and/or second magnetic field generators at the predetermined orientation.
- a measurement vector m bias of the corresponding bias magnet's magnetic field projections is collected.
- the measurement vector may be expressed in a similar manner as the linear model described in equation (b5): bias ⁇ A T b bias + n bias ⁇ (bl5)
- equation (bl5) As noted above with regard to equation (b5), the variables represented in equation (bl5) are the same, but represented in relation to the applied bias field.
- the axes may be generally assigned such as, for example, the Lorentzian dip that is closest to the zero-field splitting frequency is assigned as , the second-closest is assigned as a 2 , and so on.
- the obtained m bias vector Due to the symmetry of the sensor measurements, the obtained m bias vector has no inherent sign information for each of its four components. However, sign information may be recovered using the following process.
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Abstract
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Priority Applications (6)
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US15/372,201 US20170212187A1 (en) | 2016-01-21 | 2016-12-07 | Magneto-optical defect sensor with common rf and magnetic fields generator |
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US15/003,062 US20170023487A1 (en) | 2015-07-23 | 2016-01-21 | Light collection from dnv sensors |
US15/003,298 | 2016-01-21 | ||
US15/003,336 US20170212181A1 (en) | 2016-01-21 | 2016-01-21 | Reduced instruction set controller for diamond nitrogen vacancy sensor |
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