WO2017211504A1

WO2017211504A1 - Sensor apparatus, method for calibrating a sensor apparatus and method for capturing a measured variable

Info

Publication number: WO2017211504A1
Application number: PCT/EP2017/060490
Authority: WO
Inventors: Theresa Lutz; Fabian Purkl; Dayo Oshinubi; Robert Roelver
Original assignee: Robert Bosch Gmbh
Priority date: 2016-06-10
Filing date: 2017-05-03
Publication date: 2017-12-14
Also published as: DE102016210259B4; CN109219756A; DE102016210259A1; EP3469388A1

Abstract

The invention relates to a sensor apparatus (800). The sensor apparatus (800) has a crystal body (810) with at least one defect. Moreover, the sensor apparatus (800) has a light source (820) for irradiating the crystal body (810) with excitation light (210). Further, the sensor apparatus (800) has at least one microwave antenna (830) for applying microwaves onto the crystal body (810). Moreover, the sensor apparatus (800) has a detection device (840, 850, 855) for detecting at least one signal property of a fluorescence signal (220) from the crystal body (810). The sensor apparatus (800) also has an application device (860, 870, 880) which is embodied to apply a microwave signal for producing the microwaves and a magnetic field signal for generating an internal magnetic field, which can be applied to the crystal body (810), to the at least one microwave antenna (830).

Description

Description title

Sensor device, method for calibrating a sensor device and method for detecting a measured variable

State of the art

The invention is based on a device or a method according to the preamble of the independent claims. The subject of the present invention is also a computer program.

For example, nitrogen vacancies in a diamond lattice, also referred to as NV centers (NV = Nitrogen Vacancy), can be applied in the field of sensor technology. By stimulating the NV centers with light and

Microwave radiation, a fluorescence of the same can be observed.

DE 37 42 878 AI describes an optical magnetic field sensor in which a crystal is used as a magnet-sensitive optical component.

Disclosure of the invention

Against this background, with the approach presented here, a sensor device, methods, furthermore a control device which uses at least one of the methods, and finally a corresponding one

Computer program presented according to the main claims. The measures listed in the dependent claims are advantageous

Further developments and improvements of the device specified in the independent claim possible.

According to embodiments, in particular a sensor device and a calibration and evaluation method based on a sensor device be provided on defects or lattice defects in a crystal. In this case, for example, a function of at least one electric coil for generating a magnetic constant or alternating field can be integrated into a sensor device by additionally applying an induction current to a microwave antenna. In other words, a

Microwave antenna can be used in particular in two ways, on the one hand for microwaves and the other for an internal magnetic field. Thus, the sensor device can be calibrated in an efficient manner, in particular during use or operation, and can be easily and accurately concluded from a fluorescence signal to a measured value.

Advantageously, a microwave dependence of one here

detectable fluorescence sensitive to external agents such as

Magnetic fields, temperature changes or mechanical stresses as measured variables react. Thus, by measuring this fluorescence, it is possible to provide sensitive and robust sensors for magnetic field, current, temperature, mechanical stresses, pressure and other measurands. Due to a high sensitivity of imperfections in

Crystal lattices, for example, already weak magnetic fields sufficient and therefore only small electrical currents may be necessary, which can lead to an energy-efficient method or sensor. In the case of a sensor based on defects in a crystal body, an improvement of the calibration and evaluation method can thus be achieved in particular. A sensor device is presented which has the following features: a crystal body with at least one defect; a light source for irradiating the crystal body with excitation light; at least one microwave antenna for exposing the crystal body to microwaves; a detection device for detecting at least one signal characteristic of a fluorescence signal from the crystal body; and a applying device, which is designed to apply a microwave signal for generating the microwaves and a magnetic field signal for generating an internal magnetic field, with which the crystal body can be acted upon, to the at least one microwave antenna.

The sensor device can be designed to detect a measured variable. The measured variable may be, for example, an external magnetic field, an electrical current, a temperature, a mechanical stress, a pressure and additionally or alternatively another measured variable. The sensor device can be used, for example, as a battery current sensor and additionally or alternatively as

Combustion chamber pressure sensor, as a combined pressure sensor and geomagnetic field sensor, used as a power line detector or the like. The

Mooring device can be connected or connected signal transmitting capable with the at least one microwave antenna. The crystal body may be, for example, diamond, silicon carbide (SiC) or hexagonal boron nitride (h-BN). For example, a defect may be a nitrogen defect in a diamond, a silicon defect in silicon carbide, or a vacancy color center in hexagonal boron nitride. In other words, a defect can be a lattice defect in a lattice structure of the

Be crystal body. The detection device can be designed to optically and / or electrically detect the at least one signal property of the fluorescence signal from the crystal body. The at least one signal property of the fluorescence signal from the crystal body may be a light intensity. Thus, the detection device can be designed to provide the at least one

Signal property by means of an optical evaluation of an intensity of the fluorescence signal or by means of an electrical evaluation via a so-called Photocurrent Detection Of Magnetic Resonance (PDMR) to detect.

According to one embodiment, the sensor device may include a

Have embodiment of a control unit mentioned below.

In this case, the control unit can be connected to or connected to the light source, with the at least one microwave antenna, with the detection device and with the application device. Such an embodiment offers the advantage that by means of the control unit a precise, quick and easy calibration and measurement size detection of the sensor device can be performed. Also, the sensor device can at least one electric coil for

Causing at least one further internal magnetic field. In this case, the at least one further internal magnetic field can have a further field direction, which differs from a field direction of the internal magnetic field

different. Such an embodiment offers the advantage that, due to an alignment of defects along the crystal directions in the crystal body, for example, a direction of an external magnetic field can also be determined by a shift of fluorescence minima belonging to these directions.

In particular, the application device can be a microwave source, a

Power source and additionally or alternatively an electric filter for

Minimizing mutual interference of the microwave source and the power source. The power source may be configured to be as

Magnetic field signal to inject a direct current or an alternating current into the at least one microwave antenna. Such an embodiment offers the advantage that the diamond can be acted upon by the at least one microwave antenna in a simple, reliable, efficient and accurate manner both with microwaves and with the internal magnetic field.

A method for calibrating a sensor device is also presented, wherein the sensor device comprises a crystal body with at least one defect, a light source for irradiating the crystal body with excitation light, at least one microwave antenna for exposing the crystal body to microwaves, and a detection device for detecting at least one signal property of a fluorescence signal the crystal body, wherein the method comprises at least the following steps:

Applying a microwave signal to generate the microwaves

at least one microwave antenna; Applying a magnetic field signal for generating an internal magnetic field, with which the crystal body can be acted upon, to the at least one

Microwave antenna; and

Determining at least one microwave frequency at which a predetermined signal characteristic occurs in a frequency spectrum of the microwaves using the fluorescence signal in response to the internal magnetic field to generate calibration data for use in detecting a measurand.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit. The method can be carried out using or in

Compound with an embodiment of the above

Sensor device are advantageously carried out to calibrate the sensor device. Thus, by carrying out the method by means of the induced magnetic field, it is possible to carry out, for example, regular, calibration with regard to sensitivity as well as directional dependence of the sensor device during operation. In the step of determining, a microwave frequency may be chosen in which a variation of the

Fluorescence signal is observable depending on the internal magnetic field. The predetermined signal property may represent a minimum of the light intensity. According to an embodiment, the method may comprise a step of determining at least one reference frequency at which a reference signal property occurs in the frequency spectrum using the fluorescence signal. Here, the step of determining may be performed before the step of applying the magnetic field signal. It can be in the step of

Determining at least one shift value between the at least one

Reference frequency and the at least one microwave frequency can be calculated under the influence of the internal magnetic field. Such an embodiment offers the advantage that interference by, for example, an external

Magnetic field can be considered to allow accurate calibration. Further, in the step of applying the magnetic field signal, a magnetic field signal suitable for generating a periodically varying internal magnetic field may be applied. Such an embodiment offers the advantage that during the calibration in a simple manner a change in the

Fluorescence signal is filtered out, which varies with the known frequency of the periodically varying magnetic field. Thus, interference from external magnetic fields on the calibration can be minimized.

A method for detecting a measured variable is also presented, wherein the method can be carried out in conjunction with a sensor device comprising a crystal body with at least one defect, a light source for

Irradiating the crystal body with excitation light, at least one

A microwave antenna for exposing the crystal body to microwaves and detection means for detecting at least one signal characteristic of a fluorescence signal from the crystal body, the method having at least the following steps:

Applying a microwave signal to generate the microwaves to the at least one microwave antenna to traverse a frequency spectrum of the microwaves;

Evaluate the fluorescence signal in response to the applied

A microwave signal to at least one microwave frequency at which a predetermined signal property occurs in the frequency spectrum

determine;

Adjusting the microwave signal to generate microwaves having a microwave frequency determined in the step of determining;

Adjusting the microwave signal in response to a shift in the predetermined signal characteristic caused by a change in the measured quantity to vary a frequency of the microwaves around the determined microwave frequency until a new microwave frequency is found, in which the

shifted predetermined signal characteristic occurs; and Calculate the measurand using the microwave frequency and the new microwave frequency. This method can be used, for example, in software or hardware or in a

Mixed form of software and hardware, for example, be implemented in a control unit. The method can be carried out using or in

Compound with an embodiment of the above

Sensor device are advantageously carried out to detect at least one measured variable. A pursuit of a shift of the at least one

Minimums, for example of ODMR (Optically Detected Magnetic Resonance) optics, can be simplified and accelerated by performing the method, since not every one of them

Change a complete shutdown of the microwave spectrum of the measured variable is necessary.

According to one embodiment, in the step of calculating, the measured quantity may be calculated using the calibration data generated according to an embodiment of the aforementioned method for calibration. Such an embodiment offers the advantage that a precise and reliable determination of the measured variable even under changing

Environmental conditions can be realized.

The method may also include a step of applying a magnetic field signal for generating an internal magnetic field, which can be acted upon by the crystal body, to the at least one microwave antenna in order to generate an internal magnetic field which periodically varies with an excitation frequency. In this case, in the step of adjusting the microwave signal can be adjusted until correlated with the excitation frequency and a predetermined signal property associated frequency component of the

Fluorescence signal is maximum to find the new microwave frequency. Such an embodiment offers the advantage that a derivation of the measured value from the fluorescence spectrum can be simplified.

In particular, using an induced magnetic

Alternating field thereby the fluorescence signal are advantageously modulated. about the alternating magnetic field in one direction can be easily and reliably identified and adjusted via an alternating shift of the microwave frequency at which the at least one predetermined signal property can be detected, also spatial directions to which the at least one predetermined signal property reacts.

In this case and additionally or alternatively in the method for calibrating, in the step of applying the magnetic field signal, the magnetic field signal to the at least one microwave antenna and at least one further

Magnetic field signal to be applied to at least one further microwave antenna or to at least one electrical coil. It can do that

Magnetic field signal and the at least one further magnetic field signal differ from each other with respect to a frequency or a phase. Such an embodiment offers the advantage that over an alternating

Magnetic field with different frequencies or different phases in different spatial directions via an alternating shift of the microwave frequency at which the at least one predetermined signal property of the fluorescence can be detected, also spatial directions to which the at least one predetermined signal property reacts, can be easily and reliably identified and compared ,

Further, the method may include a step of varying the microwave signal to periodically vary a frequency of the microwaves at an excitation frequency about the particular microwave frequency. In this case, in the step of adjusting the microwave signal can be adjusted until correlated with the excitation frequency and a predetermined

Signal property associated maximum frequency component of the fluorescence signal is to find the new microwave frequency. Such an embodiment offers the advantage that no internal magnetic field is required, wherein it is also possible to measure in several spatial directions without the need for further coils.

The approach presented here also provides a control unit which is designed to implement the steps of a variant of a method presented here

to implement, control or implement appropriate facilities. Also by this embodiment of the invention in the form of a control device, the object underlying the invention can be achieved quickly and efficiently.

For this purpose, the control unit can have at least one arithmetic unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading sensor signals from the sensor or for outputting control signals to the actuator and / or or at least one

Communication interface for reading or outputting data embedded in a communication protocol. The arithmetic unit may be, for example, a signal processor, a microcontroller or the like, wherein the memory unit is a flash memory, an EPROM or a

magnetic storage unit can be. The communication interface can be designed to read or output data wirelessly and / or by line, wherein a communication interface that can read or output line-bound data, for example, electrically or optically read this data from a corresponding data transmission line or output in a corresponding data transmission line.

In the present case, a control device can be understood as meaning an electrical device which processes sensor signals and outputs control and / or data signals in dependence thereon. The control unit may have an interface, which may be formed in hardware and / or software. In a hardware training, the interfaces may for example be part of a so-called system ASICs, the various functions of the

Control unit includes. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

In an advantageous embodiment, the control device is used to control a sensor device, more precisely the light source

Detection device and the applying device of an embodiment of the aforementioned sensor device. For this purpose, the control unit can, for example, access the fluorescence signal from the detection device. The control unit can be designed to control the light source and the application device.

Also of advantage is a computer program product or computer program with program code which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and / or controlling the steps of the method according to one of the above

described embodiments, in particular when the program product or program is executed on a computer or a device. Devices and methods according to embodiments may be configured to implement an ODM R method (ODM R = Optically Detected Magnetic

Resonance; optically recorded magnetic resonance) to use or apply. In particular, a behavior of such defects in a

Crystal bodies are exploited to show fluorescence at a wavelength in the normal state under optical excitation. Is in addition to the optical

When the excitation is still irradiated with microwave radiation, the fluorescence at a certain frequency is broken, since in this case the electrons are raised to a higher energy level and recombine non-radiatively from there. In the presence of a magnetic field, the splitting of the energy level, the so-called Zeeman Splitting, occurs, and the frequency of the fluorescence is shown by the frequency

Microwave excitation based on a single defect, in particular two minima in the fluorescence spectrum, the frequency spacing is proportional to the magnetic field strength.

Embodiments of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows:

Fig. 1 is a schematic representation of a nitrogen defect in a diamond lattice; Figures 2 to 7 are energy schemes and diagrams of fluorescence characteristics according to embodiments;

8 is a schematic representation of a sensor device according to an embodiment;

Figures 9 and 10 are schematic representations of an induction of magnetic fields around a diamond according to embodiments;

Figures 11 to 13 are schematic representations and diagrams for

Directional dependence of a fluorescence measurement according to a

Embodiment;

Figures 14 to 19 diagrams for fluorescence measurement with additional microwave excitation and magnetic field excitation according to a

Embodiment;

FIG. 20 is a flowchart of a method of calibration according to an embodiment; FIG.

21 is a flow chart of a method of detecting according to an embodiment;

FIG. 22 is a flowchart of a measuring process according to FIG

Embodiment; and

Figures 23 to 28 are diagrams for fluorescence measurement with additional microwave excitation according to an embodiment.

In the following description of favorable embodiments of the present invention are for the in the various figures

represented and similar elements acting the same or similar

Reference numeral used, wherein a repeated description of these elements is omitted. Further, embodiments will be described below merely described by way of example with reference to nitrogen defects in a diamond lattice or diamond.

FIG. 1 shows a schematic representation of a nitrogen defect 105 in a diamond lattice 100 or diamond 100. The nitrogen defect 105 may also be referred to as a nitrogen vacancy center 105 or NV center 105. A carbon atom here is replaced by a nitrogen atom 110, wherein a directly adjacent carbon atom in the diamond lattice 100 is missing and thus the nitrogen defect 105 results.

FIGS. 2 to 7 show energy schemes and diagrams

Fluorescence properties according to embodiments. In this case, Fig. 2 shows a power scheme 200 without microwave excitation and without magnetic field excitation, wherein excitation light hv 210, a fluorescence signal 220 and three states ³ A, ³ E and ¹ A and respective energy levels ms = 0 and ms = ± l for the states ³ A and ³ E are shown in terms of electrons.

FIG. 3 shows a diagram 300 of the energy scheme of FIG

Diagram 300, a microwave frequency in megahertz or MHz is plotted on the abscissa axis 302, and a fluorescence in arbitrary units is plotted on the ordinate axis 304, wherein an arrow 306 parallel to the ordinate axis 304 symbolizes a rising magnetic field B. Further, in FIG. 3, four characteristic curves or graphs 310, 312, 314 and 316 are shown by way of example, which represent a fluorescence profile for magnetic fields of different strength. A first graph 310 represents a magnetic field of magnitude 0, B = 0; for example, a second graph 312 represents a 2.8 mT magnetic field; For example, a third graph 314 represents a

Magnetic field with the strength of 5.8 mT; For example, a fourth graph 360 represents a magnetic field of 8.3 mT. Minima one

Fluorescence are merely exemplified for the second graph 312 denoted by ωι and 002. A marking 320 on the first graph 310 represents the state of the energy scheme of FIG. 2, ie without magnetic field (B = 0) and without microwave excitation or a microwave frequency f 2.9 GHz. 4 shows a power scheme 400 with microwave excitation and without

Magnetic field excitation, wherein excitation light hv 210, microwave radiation 430 and three states ³ A, ³ E and ¹ A and respective energy levels ms = 0 and ms = ± l for the states ³ A and ³ E are shown in terms of electrons.

FIG. 5 shows a diagram 500 for the energy scheme from FIG. 4. The diagram 500 in FIG. 5 corresponds to the diagram of FIG. 3, with the exception that a marking 520 on the first graph 310 shows the state of the energy diagram from FIG 4 represents, i. H. without magnetic field (B = 0) and with microwave excitation or a microwave frequency f = 2.9 GHz. The

Mark 520 is here in a range of a minimum or

Fluorescence minimum of the first graph 310 is arranged.

6 shows a power scheme 600 with microwave excitation and with

Magnetic field excitation, wherein excitation light hv 210, microwave radiation 430 and three states ³ A, ³ E and ¹ A and respective energy levels ms = 0 and ms = ± l for the states ³ A and ³ E are shown in terms of electrons. Although not explicitly illustrated in FIG. 6, the states ³ E ms = ± 1 also split when the magnetic field is applied, as are the states ³ A ms = ± 1 due to Zeeman splitting. Thus, the states ³ E here have a further energy level or two separate energy levels ms = + 1 and ms = -1.

FIG. 7 shows a diagram 700 for the energy scheme from FIG. 6. The diagram 700 in FIG. 7 corresponds to the diagram from FIG. 3 or FIG. 5 with FIG

Except that two marks 720 and 725 on the second graph 312 are the facts from the power scheme of FIG. 6

represent, d. H. with a magnetic field (B * 0) and with variable

Microwave excitation or a microwave frequency. The marks 720 and 725 are each in a range of a minimum or

Fluorescence minimum of the second graph 312 arranged. For example, a first marking 720 is arranged in the region of a first minimum ωι and a second marking 725 is arranged in the region of a second minimum 002. In other words and in summary terms, energy schemes and diagrams are shown with respect to an operation of a magnetic field measurement via a fluorescence measurement with additional microwave excitation or an example of a measurement of magnetic fields, with reference to FIGS. 2 to 7. Nitrogen defects in diamond exhibit that in the in

Fig. 2 illustrated diagram or energy scheme 200 shown

Energy spectrum at room temperature. In the normal state, d. H. without

Microwaves and no magnetic field, shows a nitrogen defect at optical excitation fluorescence at a wavelength of 630 nm. If one radiates in addition to the optical excitation by the excitation light 210 yet

Microwave radiation 430, it comes at 2.88 GHz to a break in fluorescence, since the electrons are lifted in this case from the level ms = ± l of the state ³ A to the level ms = ± l of the state ³ E and from there non-radiative recombine. An external magnetic field splits the level ms = ± l (Zeeman Splitting) and shows up

Plotting the fluorescence on the frequency of the microwave excitation two minima, for example ωι and 002, in the fluorescence spectrum, the

Frequency difference is proportional to the magnetic field strength B. A

Magnetic field sensitivity is characterized by a minimum resolvable

Frequency shift defined and can reach a few ρΤ / νΉζ. This

The method is also referred to as ODM R (Optically Detected Magnetic Resonance). If the agreement

Microwave frequency with the energy gap between the state ³ A ms = 0 and the level ms = ± 1 there is a collapse of fluorescence. With an external magnetic field, the level ms = ± l splits and there are two defined microwave frequencies at which the fluorescence decreases or minima are present. The frequency spacing is proportional to the magnetic field B.

FIG. 8 shows a schematic illustration of a sensor device 800 according to one exemplary embodiment. The sensor device 800 has according to the in Fig.

8 illustrates a diamond 810 with at least one nitrogen defect, a light source 820 for irradiating the diamond 810 with excitation light 210 or for an optical excitation of the diamond 810, for example only a microwave antenna 830 for exposing the diamond 810 with microwaves or microwave radiation, a Detection device 840 for detecting a light intensity of a

Fluorescence signal 220 from the diamond 810 with a detector 850 and an optical filter 855, a contactor 860 with a

Microwave source 870 and a power source 880 for an internal magnetic field and a controller 890 and a readout circuit 890 on.

The diamond 810 is disposed between the light source 820 and the detection device 840. In this case, the optical filter 855 is disposed between the diamond 810 and the detector 850. The microwave antenna 830 is the

Diamonds 810 arranged at least partially surrounding. The

Microwave antenna 830 is signal transmitting capable connected to the applying device 860 or the microwave source 870 and the power source 880.

The applying device 860 is designed to transmit a microwave signal to the

Generating the microwaves and a magnetic field signal for generating an internal magnetic field B _mo d, with which the diamond 810 can be acted upon to apply to the microwave antenna 830.

The controller 890 is signal transmitting with the light source 820, with the detection device 840, more precisely with the detector 850, and with the

Mooring device 860 or connected to the microwave source 870 and the power source 880. The controller 890 is configured to execute the calibration method or the like shown in FIG. 20, the detection method or the like shown in FIG. 21, and / or the measurement process shown in FIG. 22 or a similar measurement process.

In other words, FIG. 8 shows a schematic representation of a

exemplary arrangement for a sensor or the sensor device 800 based on nitrogen vacancies or NV centers in the diamond 810th The

Diamond 810 is irradiated in operation of the sensor device 800 for excitation by the light source 820 and irradiated from the microwave source 870 via the light source 820

Microwave antenna 830 charged with microwaves. The fluorescence signal 220 is separated from the excitation light 210 by the optical filter 855 and impinges on the detector 850 which applies a measurement of a light intensity to the light source Evaluation circuit 890 or passes on to the control unit 890. The controller 890 is configured to inter alia also the light source 820 and the

To control microwave source 870. In addition, the power source 880 is for

Induction of the magnetic field B _mo d connected to the microwave antenna 830. Thus, FIG. 8 shows an exemplary configuration of the sensor device 800 based on NV centers in the diamond 810. The microwave source 880 is electrically connected to the microwave antenna 830, which is implemented in, for example, a wire having one or more turns around the diamond 810, and is designed to excite the nitrogen defects in the diamond 810 with microwaves. Alternatively, other methods of preparation of

Coils or microwave antennas are used, such. B. a use of traces on a circuit board.

FIG. 9 shows a schematic representation of an induction of a magnetic field or internal magnetic field B _mo d about a diamond 810 in accordance with FIG

Embodiment. Shown here in FIG. 9 are the diamond 810 and the microwave antenna 830 of the sensor device of FIG. 8 or a similar sensor device, the internal magnetic field B _mo d or magnetic field B _mo d and a magnetic field signal Lod or additional current Lod or induction current Lod which is applied to the microwave antenna 830. Thus, FIG. 9 shows induction of the magnetic field B _mo d about the diamond 810 by applying the additional current Lod to the microwave antenna 830.

10 shows a schematic representation of an induction of magnetic fields B _y and B _x around a diamond 810 according to one exemplary embodiment. In other words, FIG. 10 shows a generation of the magnetic fields B _y and B _x in two spatial directions by an arrangement of a plurality of coils 830 and 1030 or microwave antennas 830 and 1030. Referring to FIGS. 9 and 10, it should be noted that the

Microwave antenna 830 is used to induce a magnetic field B _mo d acting on the diamond 810. For this purpose is in the

Microwave antenna 830 a DC or AC in the form of

Induction current Lod imprinted, which generates a corresponding magnetic field B _mo d, as shown in Fig. 9. To magnetic fields B _y and B _x in more than 10 is intended to use more than one microwave antenna 830, as shown in FIG. 10 with reference to another microwave antenna 1030 or electrical coil 1030. Here, the microwave antenna 830 and the other microwave antenna 1030 or electric coil 1030 z. B. arranged orthogonal to each other. Will the

Microwave antenna 830 used to generate an alternating magnetic field B _mo d, influencing the AC power source used for this purpose (frequencies eg in the kHz range) and the microwave source (frequencies in the GHz range) by an electric filter, for. As a network of passive components can be prevented.

11 shows a schematic representation of the directional dependence of a fluorescence measurement according to an exemplary embodiment. Shown here are the diamond 810 and the microwave antenna 830 of the sensor device of FIG. 8 or a similar sensor device and an internal magnetic field B _mo d, a measuring direction 1101 and symbolically an alignment 1102 of individual nitrogen defects at the four crystal directions in the diamond 810 11 shows an arrangement for determining a sensitivity of four ODMR minima or fluorescence minima, which are related to the four crystal directions in the diamond 810, on magnetic fields B _mo d in the measuring direction 1101 by applying the internal magnetic field B _mo d or a reference field B _mo d, which is induced via the microwave antenna 830 or an electrical coil. FIG. 12 shows a diagram 1200 for the directional dependence of a

Fluorescence measurement according to an embodiment. The graph 1200 in FIG. 12 shows a light intensity 1204 of a fluorescence signal at the

Ordinatenachse in dependence on a microwave frequency 1202 on the abscissa axis for the facts of Fig. 11. In this case, a shift of individual ODMR minima by the internal magnetic field B _mo d for an optically detected magnetic resonance (ODM R) is illustrated in FIG. Here, in the diagram 1200, four pairs of ODMR minima 1210, 1212, 1214 and 1216 are drawn. A first pair of ODMR minima 1210 relates to a first crystal direction of the diamond and shows a first one

Displacement distance. A second pair of ODMR minima 1212 relates on a second crystal direction of the diamond and shows a second

Displacement distance. The second shift distance is less than the first shift distance. A third pair of ODMR minima 1214 refers to a third crystal direction of the diamond and shows a third one

Displacement distance. The third displacement distance is less than the second displacement distance. A fourth pair of ODMR minima 1216 refers to a fourth crystal direction of the diamond and shows a fourth shift distance. The fourth shift distance is less than the third shift distance. Strictly speaking, the fourth is

Displacement distance zero, with the fourth pair of ODMR minima 1216 not shifted relative to one another.

FIG. 13 shows a direction dependence diagram 1300

Fluorescence measurement according to an embodiment. The diagram 1300 in FIG. 13 shows a relative sensitivity 1304 with respect to four crystal directions in the measuring direction on the ordinate axis as a function of a crystal direction 1302 on the abscissa axis for the situation from FIG. 11 or FIG. 12.

Here, a first crystal direction is associated with a first bar 1310 having a first sensitivity value. A second crystal direction is associated with a second bar 1312 having a second sensitivity value. The second

Sensitivity value is less than the first sensitivity value. A third

Crystal direction is associated with a third bar 1314 having a third sensitivity value. The third sensitivity value is less than the second one

Sensitivity value. A fourth crystal direction is associated with a fourth bar 1316 having the height and a fourth sensitivity value of zero, respectively.

Figures 14 to 19 are diagrams for measuring fluorescence with additional microwave excitation and magnetic field excitation according to a

Embodiment. In this case, the fluorescence measurement can be carried out using the sensor device illustrated in FIG. 8 or a similar sensor device or in conjunction with at least one of the methods from FIGS. 20 and 21.

FIG. 14 shows a plot 1400 of an ODMR spectrum for various internally generated magnetic fields B _mod as a function of a microwave frequency according to an embodiment. The abscissa axis 1402 plots a relative change in the microwave frequency in megahertz (MHz) and the ordinate axis 1404 plots an ODMR signal in arbitrary units. Further, in graph 1400, three graphs 1410, 1412, and 1414 are drawn. The three graphs 1410, 1412, and 1414 each exemplarily show only a minimum of the two minima generated by Zeeman splitting from FIGS. 2 to 7. Here, the ODMR spectrum is locked to the minimum. A first graph 1410 represents a first ODMR signal at an applied magnetic field B _mo d = 0 or without applied magnetic field. A second graph 1412 represents a second ODMR signal at a

applied magnetic field B _m od = + B. A third graph 1414 represents a third ODMR signal at an applied magnetic field B _mo d = -B.

Fig. 15 shows a signal-time diagram 1500 related to the ODMR spectrum of Fig. 14. More specifically, a temporal variation of one through a

Microwave antenna or coil generated magnetic field B _mod 1510 and a resulting ODMR output signal 1520 for constant

Microwave excitation. On the abscissa axis 1502 here is the time in

Seconds (s) multiplied by 10 ^"3 and plotted on the ordinate axis 1504 are signals in arbitrary units.

16 shows a diagram 1600 of a frequency spectrum or

Frequency content of the signals of Fig. 15. More specifically, the diagram 1600 shows a frequency spectrum of the signals of Fig. 15 in the case where the microwave frequency is determined by an external magnetic field

Position of the ODMR minimum matches. The abscissa axis 1602 plots a frequency in Hertz (Hz) and the ordinate axis 1604 plots a Fourier transform in arbitrary units. A first graph 1610 represents the Fourier transform of the magnetic field B _mo d and a second graph 1620 represents the Fourier transform of the ODM R

Signal.

17 shows a diagram 1700 of an ODMR spectrum for various internally generated magnetic fields B _mod as a function of a microwave frequency according to an exemplary embodiment. The diagram 1700 in FIG. 17 corresponds Here, the diagram of Fig. 14 except that the ODM R spectrum is shown by the additional action of an external constant magnetic field. Here, the three graphs 1410, 1412 and 1414 are shifted due to the external magnetic field.

FIG. 18 shows a signal-time diagram 1800 related to the ODMR spectrum of FIG. 17. The signal-time diagram 1800 in FIG. 18 corresponds to the signal-time diagram of FIG. 15, except that FIG a waveform of the ODMR output signal 1520 is different from a waveform shown in FIG.

19 shows a diagram 1900 of a frequency spectrum or

Frequency content of the signals from FIG. 18. The diagram 1900 in FIG. 19 corresponds to the diagram of FIG. 16, except that the second graph 1620, which represents the Fourier transformation of the ODMR signal, has a different course than the one In other words, Fig. 19 shows a frequency spectrum of the signals of Fig. 18 in the case where the microwave frequency is separated by an external one

Magnetic field determined position of the ODMR minimum does not match.

FIG. 20 shows a flow chart of a method 2000 for calibration according to one exemplary embodiment. The method 2000 is executable to a

Calibrate sensor device. In particular, method 2000 may be practiced to include the sensor device of FIG. 8 or the like

Calibrate sensor device. Generally speaking, the calibration method 2000 is operable to calibrate a sensor device including a diamond having at least one nitrogen vacancy, a light source for irradiating the diamond with excitation light, at least one of the two

A microwave antenna for exposing the diamond to microwaves and detection means for detecting a light intensity of a microwave

Has fluorescence signal from the diamond.

In the method 2000 for calibration, in a step 2010 of the

Applying a microwave signal for generating the microwaves applied to the at least one microwave antenna of the sensor device. Below is in a further step 2020 of applying a magnetic field signal for generating an internal magnetic field, which is acted upon by the diamond, applied to the at least one microwave antenna. Then, in a step 2030 of determining, at least one microwave frequency at which a minimum of the light intensity occurs is submerged in a frequency spectrum of the microwaves

Use of the fluorescence signal in response to the internal magnetic field determined to generate calibration data for use in detecting a measured variable.

According to the exemplary embodiment illustrated in FIG. 20, the method 2000 for calibrating further comprises a step 2040 of determining in which at least one reference frequency at which a reference minimum of the

Light intensity occurs in the frequency spectrum using the

Fluorescence signal is detected. The determining step 2040 is executable before the step of applying the magnetic field signal. Specifically, the determining step 2040 is between the step 2010 of application of the microwave signal and the step 2020 of applying the microwave signal

Magnetic field signal executed. In this case, in step 2030 of the determination, at least one shift value between the at least one

Reference frequency and the at least one microwave frequency calculated.

In other words, by carrying out the method 2000 for calibration using an internal magnetic field, e.g. B. over a

Microwave antenna or coil or is produced in another known manner, a sensitivity of the sensor device to magnetic fields during a

Operating calibrated. For this purpose, a magnetic field of known strength is generated and the associated displacement of one or more minima in the ODMR spectrum is measured. These calibration data are stored, for example, and used hereafter to calculate the vectorial size of an external magnetic field from measured shifts in the ODMR minima.

Because during the calibration by means of a magnetic field generated in the sensor device simultaneously applied outer magnetic fields lead to disturbances can, according to one embodiment, a relative measurement of the ODMR signal is performed. For this purpose, in step 2040 of the determination and in step 2030 of determining z. B. two measurements immediately before and after switching on or applying the internal magnetic field performed and compared. Optionally, a periodically varying magnetic field can be generated or applied. The displacements of the ODMR spectra for such a varying field B _mo d are shown by way of example in FIG. 14 (only one peak of the two minima generated by Zeeman splitting is shown in each case).

During one embodiment of the method 2000 for calibration, only the shift of the ODMR spectrum which varies with the known frequency of the generated magnetic field can be filtered out. Thus, the influence of external magnetic fields on the calibration can be minimized.

According to one embodiment, also a directional

Sensitivity of the individual minima are assigned to the spatial directions of the sensor device. NV centers or nitrogen defects in the diamond align in each case at one of the four crystal directions in the diamond and are also sensitive in this direction to magnetic fields. Depending on a direction of the magnetic field, the four minima pairs associated with these four orientations are shifted differently in the ODMR spectrum, as shown in FIG.

12 is shown. Using the at least one microwave antenna or coil arranged in the desired or several desired measurement directions and measuring the displacement of the different ODM R minima due to the generated magnetic fields, the sensitivities of these minima to the measurement direction can be determined. This principle is shown by way of example in FIGS. 11 to 13. The measured values are stored and used to calculate a vector of an external magnetic field from a measured shift of the minima. The calibration of several spatial directions by a plurality of microwave antennas and / or coils may, for. B. be performed sequentially. Alternatively it is possible to different

Microwave antennas and / or coils with currents or magnetic field signals to occupy, which differ in frequencies or phases. Thus, the assignment of the relative shift of the ODMR spectra to the

Measuring directions on the identification using frequency or phase information also possible simultaneously. FIG. 21 shows a flowchart of a method 2100 for detecting a measured variable according to an exemplary embodiment. In particular, the method 2100 is for detecting in conjunction with or using the

Sensor device of FIG. 8 or a similar sensor device executable.

Generally speaking, the detection method 2100 is practicable in conjunction with a sensor device comprising a diamond having at least one nitrogen vacancy, a light source for irradiating the diamond with excitation light, at least one microwave antenna for

Microwaving the diamond and detection means for detecting a light intensity of a fluorescence signal from the

Has diamonds.

In the detection method 2100, in a step 2110 of application, a microwave signal for generating the microwaves is applied to the at least one microwave antenna to traverse a frequency spectrum of the microwaves. Thereafter, in a step 2120 of the evaluation, the

Fluorescence signal in response to the applied microwave signal

evaluated to determine at least one microwave frequency at which a minimum of the light intensity occurs in the frequency spectrum. Then, in a step 2130 of setting, the microwave signal is set to

Microwaves with a determined in the step of determining

To generate microwave frequency. Subsequently, in a step 2140 of the adjustment, the microwave signal is adjusted in response to a shift of the minimum caused by a change of the measured variable to a

To vary the frequency of the microwaves around the particular microwave frequency until a new microwave frequency is found at which the shifted minimum of light intensity occurs. Finally, in a step 2150 of calculating, the measured quantity is calculated using the

Calculated microwave frequency and the new microwave frequency.

In one embodiment, in step 2150 of calculating, the measure is calculated using the calibration data generated according to the method of calibration of FIG. 20 or a similar method. In other words, in step 2150 of the calculation, the Calibration data generated according to the method of calibration of Fig. 20 or a similar method.

Optionally, the detecting method 2100 includes a step 2160 of applying a magnetic field signal or a step 2170 of changing the magnetic field signal

Microwave signal on. The step 2160 of applying a magnetic field signal or the step 2170 of changing the microwave signal are in this case executable between the step 2130 of setting the microwave signal and the step 2140 of adjusting the microwave signal.

In step 2160 of the application, a magnetic field signal for generating an internal magnetic field to which the diamond can be acted upon is applied to the at least one microwave antenna in order to generate an internal magnetic field which periodically varies with an excitation frequency. In this case, the microwave signal is then adjusted in step 2140 of adjusting until one with the

Excitation frequency correlated and a minimum of the light intensity associated frequency component of the fluorescence signal is maximum to find the new microwave frequency. In one embodiment, in step 2160 of applying the magnetic field signal, the magnetic field signal may be applied to the at least one microwave antenna and at least one other

Magnetic field signal to be applied to at least one further microwave antenna or to at least one electrical coil. In this case, the magnetic field signal and the at least one further magnetic field signal differ from one another with respect to a frequency or a phase.

In step 2170 of varying, the microwave signal is varied to periodically vary a frequency of the microwaves having an excitation frequency about the particular microwave frequency. In this case, the microwave signal is then adjusted in step 2140 of the adjustment until one with the

Excitation frequency correlated and a minimum of the light intensity associated frequency component of the fluorescence signal is maximum to find the new microwave frequency.

FIG. 22 shows a flow chart of a measurement process 2200 according to an exemplary embodiment. In other words, Fig. 22 shows an example of one Sequence of a measurement or a measuring process 2200, wherein an internally generated magnetic field is used to modulate an ODMR spectrum. The measuring process 2200 can be carried out in conjunction with the method for detecting from FIG. 21 or a similar method.

At a block 2201, the measurement is started. Thereafter, at block 2202, an ODMR spectrum is transmitted over all microwave frequencies

added. The block 2202 is hereby comparable to the step of applying the microwave signal in the method for detecting from FIG. 21. Then, the measuring process 2200 proceeds to a block 2203 in which a position (microwave frequency) of the minima in the ODMR spectrum is identified. Block 2203 is similar to the step of evaluating the

Fluorescence signal in the method of detection of Fig. 21. Subsequently, in a block 2204, the microwave frequency is set to the position of the relevant minimum. The block 2204 is similar to the step of setting the microwave signal in the detection method of FIG. 21.

Thereafter, the measurement process 2200 proceeds to a block 2205 in which an internal alternating magnetic field with a frequency or excitation frequency fmag is generated. The block 2205 is similar to the step of applying the magnetic field signal according to an embodiment of the detecting method of FIG. 21.

The measurement process 2200 then passes to a decision block 2206, in which it is checked whether a frequency component f _ma g of the ODMR signal is maximum. If so, the process proceeds to block 2207 where the microwave frequency determines the size of the external magnetic field. Block 2207 is similar to the step of calculating in the method of FIG. 21. From block 2207, the measurement process 2200 loops back to decision block 2206.

If it is determined at decision block 2206 that the

Frequency f _ma g of the ODMR signal is not maximum, the measuring process 2200 goes to a block 2208, in which it is determined whether the minimum in the Near the original frequency is suspected. If not, the measurement process 2200 goes back to the block 2202. If so, the measurement process 2200 proceeds to a block 2209 where a systematic variation of the microwave frequency from the previous position in both directions is performed. From block 2207, measurement process 2200 returns to decision block 2206.

Referring to Figs. 21 and 22, the method 2100 for detecting and measuring process 2200 will be summarized below and in other words.

A method 2100 for sensing or measuring process 2200 is presented in which internally generated magnetic fields are used for modulation so as to easily determine and track a position and shift of the individual minima in the ODMR spectrum of the sensor device. When changing the measured value, the z. B. may be an external magnetic field, a temperature or a mechanical strain, move the microwave frequencies at which the individual minima of fluorescence occur. In the process 2100 for detecting or in the measuring process 2200, the external measured variable is determined via this displacement.

Conventionally, in order to determine shifts in the minima, an intensity of fluorescence is often measured while the microwave frequency is changed. In the spectrum thus acquired, the minima are then usually identified by a mathematical operation and compared with a previously recorded spectrum in order to determine a relative shift of the minima.

According to embodiments, however, in the method 2100 for detecting or in the measuring process 2200, a calculation effort can be reduced and a bandwidth of the sensor device can be increased, since a range of microwave frequencies to be traversed regularly for recording the spectrum can be reduced. For this purpose, in the method 2100 for detecting or in the measuring process 2200, first of all a complete ODMR spectrum is recorded in order to identify positions of the minima, such as it is shown in the step 2110 of application of the microwave signal and the step 2120 of the evaluation of the fluorescence signal or in the blocks 2202 and 2203. Thereafter, the microwave source is set to the frequency of the minimum to be measured, as shown in step 2130 of setting the microwave signal and in block 2204, respectively.

Now in block 2205 or in step 2160 of the application of the

Magnetic field signal internally in the sensor device a periodically changing, z. B. sinusoidal as shown in Fig. 15 and Fig. 18, magnetic field B _mo d induced in the direction to which this minimum is sensitive. The frequency f _mo d of the alternating field is set so that it is higher than a desired bandwidth of the sensor device, but less than a reaction time of nitrogen vacancies. Due to the internally generated magnetic field, the position of the minimum varies as shown in FIG. 14 around the previously determined average microwave frequency. Thus, the intensity of the fluorescence signal measured at a constant microwave frequency also periodically changes at twice the frequency of the impressed magnetic field (2f _mo d), as shown in FIGS. 15 and 16. An external signal or a measured variable, such. B. an external magnetic field, results in a shift of the average microwave frequency by which the ODMR minimum oscillates periodically, as shown in Fig. 17. At constant microwave frequency, therefore, the observed fluorescence signal changes. In particular, the proportion of the fluorescence signal which has twice the excitation frequency is reduced, as shown in FIGS. 18 and 19. The proportion of the fluorescence signal with the double excitation frequency becomes maximum when the

Microwave frequency coincides with the frequency of the ODMR minimum, which is assumed without the internal magnetic field. By means of an evaluation of this signal component, a change of an external measured value can consequently be detected easily and an evaluation concept similar to a so-called lock-in method can be realized.

If such a change in the external measurement is detected, at block 2209, the microwave frequency is varied in both directions of the original frequency, ie, higher and lower frequencies until the proportion in the ODRM signal becomes twice the excitation frequency (2f _mo d) and the maximum new Microwave frequency of the shifted ODRM minimum is found. From this position of the shifted minimum can, for. B. optional under

Using the calibration values from the calibration procedure of FIG. 20, the new measured value of the external measurement is determined. Only when the minimum can not be found again by a repeated variation of the microwave frequency, an ODMR spectrum is again recorded to determine the position of the minima, as previously described.

For example, a plurality of microwave antennas and / or a plurality of coils are used for a modulation in more than one measuring axis. It is again conceivable to vary the induced magnetic fields relative to one another in frequency or phase such that it is possible to associate the effect of the fields with the measurement axes via this variation. Figures 23 to 28 are diagrams for fluorescence measurement with additional

Microwave excitation according to one embodiment. The diagrams shown in FIGS. 23 to 28 are similar to the diagrams shown in FIGS. 14 to 19. The fluorescence measurement is in this case using the sensor device shown in FIG. 8 or a similar sensor device or in conjunction with at least one of the methods

Fig. 20 and Fig. 21 feasible.

FIG. 23 shows a diagram 2300 of an ODMR spectrum for a periodically varied frequency of the microwave excitation according to an embodiment. On the abscissa axis 2302 is a change in the microwave frequency A † MW in

Megahertz (MHz) is plotted and on the ordinate axis 2304 an ODMR signal is plotted in arbitrary units. Furthermore, a graph 2310 is plotted in the diagram 2300, which represents by way of example only a minimum of the two minima generated by Zeeman splitting from FIGS. 2 to 7. Here, the ODMR signal is locked to the minimum. In the readout concept shown here, the microwave frequency or frequency of the microwave excitation is periodically varied, here z. In the boundaries marked by lines 2320 and 2330, resulting in an output signal having similar properties to those of Figures 14 to 19, without modulation by an internally generated magnetic field. A shift in the ODM R Minima due to external measurements can be detected as described above.

FIG. 24 shows a signal-time diagram 2400 related to the ODMR spectrum from FIG. 23. The signal-time diagram 2400 corresponds to the signal-time diagram.

Diagram of Fig. 15 except that instead of the generated magnetic field, the periodically varied microwave frequency A † MW 2410 is plotted as a graph. In other words, Fig. 24 shows a variation of A † MW and the ODMR signal.

FIG. 25 shows a diagram 2500 of a frequency spectrum or

Frequency content of the ODMR signal of FIG. 24. In this case, the diagram 2500 corresponds to the diagram from FIG. 16, with the exception that only the Fourier transformation of the ODMR signal represented by the graph 1620 is plotted.

FIG. 26 shows a graph 2600 of an ODMR spectrum for a periodically varied microwave excitation frequency according to one embodiment. Diagram 2600 in FIG. 26 corresponds to the diagram of FIG. 23, except that the ODMR spectrum is shown with the additional action of an external constant magnetic field. Here, the graph 2310 is shifted due to the external magnetic field.

FIG. 27 shows a signal-time diagram 2700 related to the ODMR spectrum of FIG. 26. The signal-time diagram 2700 in FIG. 27 corresponds to FIG

Signal-time diagram of Fig. 24 except that a waveform of the ODMR output signal 1520 is different from a waveform shown in Fig. 24. FIG. 28 shows a diagram 2800 of a frequency spectrum or

Frequency content of the ODMR signal of Fig. 27. The diagram 2800 in Fig. 28 corresponds to the diagram of Fig. 25 except that the graph 1620 representing the Fourier transform of the ODMR signal

represents a different course than the graph of FIG. 25. FIGS. 23 to 28 thus show an evaluation concept in which, in contrast to a modulation of the fluorescence signal by an internally generated magnetic field, the microwave frequency (by the previously determined frequency of a minimum in the ODMR spectrum) is periodically varied. This results in a similar output signal as through an alternating magnetic field without being applied. Changes of an external measurand can be detected as described above. Thus, it is possible to measure in several directions in space, without the additional expense of further coils being necessary.

If an exemplary embodiment comprises a "and / or" link between a first feature and a second feature, then this is to be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment either only first feature or only the second feature.

Claims

claims

A sensor device (800) comprising: a crystal body (810) having at least one defect (105); a light source (820) for irradiating the crystal body (810) with excitation light (210); at least one microwave antenna (830; 1030) for exposing the crystal body (810) to microwaves (430); a detection device (840, 850, 855) for detecting at least one signal characteristic of a fluorescent signal (220) from the crystal body (810); and applying means (860, 870, 880) adapted to generate a microwave signal for generating the microwaves (430) and

Magnetic field signal (Lod) for generating an internal magnetic field (Bmod), with which the crystal body (810) can be acted upon, to be applied to the at least one microwave antenna (830; 1030).

2. Sensor device (800) according to claim 1, with a control device (890) according to one of the following claims, wherein the

Control unit (890) signal transmitting capable with the light source (820), with the detection means (840, 850, 855) and with the applying means (860, 870, 880) connectable or connected.

3. Sensor device (800) according to one of the preceding

Claims, having at least one electrical coil (1030) for effecting at least one further internal magnetic field, wherein the at least one further internal magnetic field has a further field direction, the from a field direction of the internal magnetic field (B _mo d)

different.

Sensor device (800) according to one of the preceding

Claims wherein the applying means (860) comprises a microwave source (870), a power source (880) and / or an electrical filter for minimizing interference of the microwave source (870) and the power source (880), the power source (880) is formed to impress as a magnetic field signal (Lod) a direct current or an alternating current in the at least one microwave antenna (830; 1030).

Method (2000) for calibrating a sensor device (800), wherein the sensor device (800) comprises a crystal body (810) with at least one defect (105), a light source (820) for irradiating the crystal body (810) with excitation light (210), at least a

A microwave antenna (830, 1030) for exposing the crystal body (810) to microwaves (430) and detection means (840, 850, 855) for detecting at least one signal property of a

Fluorescence signal (220) from the crystal body (810), the method (2000) comprising at least the following steps:

Applying (2010) a microwave signal to generate the microwaves (430) to the at least one microwave antenna (830; 1030);

Applying (2020) a magnetic field signal (Lod) to generate an internal magnetic field (B _mo d), with which the crystal body (810)

can be acted upon, the at least one microwave antenna (830, 1030); and

Determining (2030) at least one microwave frequency at which a predefined signal property occurs in a frequency spectrum of the microwaves (430) using the fluorescence signal (220) in response to the internal magnetic field (B _mo d) to obtain calibration data for use in detecting a measurand to create. Method (2000) according to claim 5, comprising a step (2040) of determining at least one reference frequency at which a

The reference signal property occurs in the frequency spectrum using the fluorescence signal (220), wherein the determining step (2040) is performed prior to the step (2020) of applying the magnetic field signal (Lod), wherein in the step (2030) of determining at least one shift value between the at least one reference frequency and the at least one microwave frequency is calculated under the influence of the internal magnetic field (B _mo d).

The method (2000) according to any one of claims 5 to 6, wherein in the step (2020) of applying the magnetic field signal (Lod)

Magnetic field signal (Lod) is applied, which is suitable to generate a periodically varying internal magnetic field (B _mo d).

A method (2100) for detecting a measured variable, the method (2100) being executable in conjunction with a sensor device (800) comprising a crystal body (810) with at least one defect (105), a light source (820) for irradiating the crystal body ( 810) with

Excitation light (210), at least one microwave antenna (830; 1030) for exposing the crystal body (810) to microwaves (430) and detection means (840, 850, 855) for detecting at least one signal property of a fluorescence signal (220) from the diamond (810 ), the method (2100) having at least the following steps:

Applying (2110) a microwave signal to generate the microwaves (430) to the at least one microwave antenna (830; 1030) to traverse a frequency spectrum of the microwaves (430);

Evaluating (2120) the fluorescence signal (220) in response to the applied microwave signal to determine at least one microwave frequency at which a predefined signal property occurs

To determine frequency spectrum; Adjusting (2130) the microwave signal to provide microwaves (430) having one of the steps determined in step (2120)

To generate microwave frequency;

Adjusting (2140) the microwave signal in response to a shift in the predefined signal characteristic caused by a change in the measured quantity to vary a frequency of the microwaves (430) by the determined microwave frequency until a new microwave frequency is found at which the shifted predefined signal property occurs ; and

Calculating (2150) the measurand using the

Microwave frequency and the new microwave frequency.

The method (2100) according to claim 8, wherein in the step (2150) of calculating, the measured quantity is calculated using the calibration data generated by the method (2000) for calibration according to any one of claims 5 to 7.

Method (2100) according to one of claims 8 to 9, comprising a step (2160) of applying a magnetic field signal (Lod) for generating an internal magnetic field (B _mo d) to which the crystal body (810) can be acted upon A microwave antenna (830; 1030) for generating an internal magnetic field (B _mo d) periodically varying with an excitation frequency, wherein in step (2140) of adjusting the microwave signal is adjusted until coincident with the

Excitation frequency correlated and a predefined

Signal property associated maximum frequency of the fluorescence signal (220) is to find the new microwave frequency.

The method (2100) according to one of claims 5 to 7 and 10, wherein in step (2160) of applying the magnetic field signal (Lod) the

Magnetic field signal (Lod) to the at least one microwave antenna (830) and at least one further magnetic field signal to at least one another microwave antenna (1030) or at least one electrical coil (1030) is applied, wherein the magnetic field signal (Lod) and the at least one further magnetic field signal with respect to a frequency or a phase differ from each other.

The method (2100) according to one of claims 8 to 9, comprising a step (2170) of varying the microwave signal to periodically vary a frequency of the microwaves (430) having an excitation frequency around the determined microwave frequency, wherein in step (2140 ) of adjusting the microwave signal is adjusted until correlated with the excitation frequency and a predefined

A controller (890) arranged to execute steps of a method (2000; 2100) according to any one of the preceding claims in respective units.

A computer program adapted to perform a method (2000;

2100) according to any one of the preceding claims.

15. Machine-readable storage medium on which the computer program

is stored according to claim 14.