DE102016210259B4 - Sensor device, method for calibrating a sensor device and method for detecting a measured variable - Google Patents

Abstract

Sensor device (800) having the following features: 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 Applying microwaves (430) to the crystal body (810); a detection device (840, 850, 855) for detecting at least one signal property of a fluorescence signal (220) from the crystal body (810); andan application device (860, 870, 880) which is designed to generate a microwave signal for generating the microwaves (430) in order to cause the fluorescence signal (220) to break in, and a magnetic field signal (Imod) for generating an internal magnetic field (Bmod) , with which the crystal body (810) can be acted upon in order to bring about a Zeeman effect, to apply to the at least one microwave antenna (830; 1030), the application device (860) having a microwave source (870), a power source (880) and / or an electrical filter for minimizing mutual influencing of the microwave source (870) and the current source (880), the current source (880) being designed to supply a direct current or an alternating current as a magnetic field signal (Imod) into the at least one microwave antenna (830; 1030).

Description

State of the art

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

For example, nitrogen vacancies in a diamond lattice, also referred to as NV centers (NV = Nitrogen Vacancy), can be used in the field of sensor technology. By exciting the NV centers with light and microwave radiation, fluorescence of the same can be observed.

the DE 37 42 878 A1 describes an optical magnetic field sensor in which a crystal is used as a magnetically sensitive optical component.

Disclosure of the invention

Against this background, with the approach presented here, a sensor device, method, furthermore a control device which uses at least one of the methods, and finally a corresponding computer program according to the main claims are presented. The measures listed in the dependent claims make advantageous 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 for a sensor device based on defects or lattice defects in a crystal can be provided. Here, for example, a function of at least one electrical 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 two ways, on the one hand for microwaves and on the other hand for an internal magnetic field. The sensor device can thus be calibrated in an efficient manner, in particular during use or operation, and a measurement value can be inferred simply and precisely from a fluorescence signal.

A microwave dependency of a fluorescence that can be detected here can advantageously react sensitively to external influences such as magnetic fields, temperature changes or mechanical stresses as measured variables. Thus, by measuring this fluorescence, it is possible to provide sensitive and robust sensors for magnetic field, current, temperature, mechanical stresses, pressure and other measured variables. Due to the high sensitivity of imperfections in crystal lattices, for example, already weak magnetic fields can be sufficient and thus only small electrical currents are necessary, which can lead to an energy-efficient method or sensor. In the case of a sensor that is based on imperfections in a crystal body, an improvement in the calibration and evaluation method can be achieved in particular.

• einen Kristallkörper mit zumindest einer Fehlstelle;
• eine Lichtquelle zum Bestrahlen des Kristallkörpers mit Anregungslicht;
• zumindest eine Mikrowellenantenne zum Beaufschlagen des Kristallkörpers mit Mikrowellen;
• eine Detektionseinrichtung zum Detektieren zumindest einer Signaleigenschaft eines Fluoreszenzsignals von dem Kristallkörper; und
• eine Anlegeeinrichtung, die ausgebildet ist, um ein Mikrowellensignal zum Erzeugen der Mikrowellen und ein Magnetfeldsignal zum Generieren eines internen Magnetfelds, mit dem der Kristallkörper beaufschlagbar ist, an die zumindest eine Mikrowellenantenne anzulegen.

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 applying microwaves to the crystal body;
• detection means for detecting at least one signal property of a fluorescence signal from the crystal body; and
• an application 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 applied to the at least one microwave antenna.

The sensor device can be designed to detect a measured variable. The measured variable can be, for example, an external magnetic field, an electric current, a temperature, a mechanical tension, 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 a combustion chamber pressure sensor, as a combined pressure sensor and geomagnetic field sensor, as a power line detector or the like. The application device can be connected or connected to the at least one microwave antenna in a manner capable of signal transmission. The crystal body can be, for example, diamond, silicon carbide (SiC) or hexagonal boron nitride (h-BN). A flaw can be, for example, a nitrogen flaw in a diamond, a silicon flaw in silicon carbide or a flaw color center in hexagonal boron nitride. In other words, a flaw can be a lattice flaw or flaw in a lattice structure of the crystal body. The detection device can be designed to detect the at least one signal property of the fluorescence signal from the crystal body optically and / or electrically. The at least one signal property of the fluorescence signal from the crystal body can be a light intensity. The detection device can thus be designed to detect the at least one signal property by means of an optical evaluation using an intensity of the fluorescence signal or by means of an electrical evaluation using a so-called photocurrent detection of magnetic resonance (PDMR).

According to one embodiment, the sensor device can have an embodiment of a control device mentioned below. Here, the control device can be able to transmit signals to the light source, to the at least one microwave antenna, to the detection device and to the application device. Such an embodiment offers the advantage that a precise, quick and simple calibration and measurement variable acquisition of the sensor device can be carried out by means of the control device.

The sensor device can also have at least one electrical coil for producing at least one further internal magnetic field. Here, the at least one further internal magnetic field can have a further field direction that differs from a field direction of the internal magnetic field. Such an embodiment offers the advantage that, due to an alignment of defects along the crystal directions in the crystal body, a direction of an external magnetic field can also be determined, for example, by shifting fluorescence minima belonging to these directions.

In particular, the application device can have a microwave source, a power source and, additionally or alternatively, an electrical filter for minimizing mutual influencing of the microwave source and the power source. The current source can be designed to impress a direct current or an alternating current into the at least one microwave antenna as a magnetic field signal. Such an embodiment offers the advantage that both microwaves and the internal magnetic field can be applied to the diamond via the at least one microwave antenna in a simple, reliable, efficient and precise manner.

• Anlegen eines Mikrowellensignals zum Erzeugen der Mikrowellen an die zumindest eine Mikrowellenantenne;
• Anlegen eines Magnetfeldsignals zum Generieren eines internen Magnetfelds, mit dem der Kristallkörper beaufschlagbar ist, an die zumindest eine Mikrowellenantenne; und
• Bestimmen zumindest einer Mikrowellenfrequenz, bei der eine vorbestimmte Signaleigenschaft auftritt, in einem Frequenzspektrum der Mikrowellen unter Verwendung des Fluoreszenzsignals ansprechend auf das interne Magnetfeld, um Kalibrierungsdaten zur Verwendung bei einem Erfassen einer Messgröße zu erzeugen.

A method for calibrating a sensor device is also presented, the sensor device having 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 applying microwaves to the crystal body and a detection device for detecting at least one signal property of a fluorescence signal from comprising the crystal body, the method comprising at least the following steps:

• Applying a microwave signal for generating the microwaves to the 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 property 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 measurement quantity.

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 device. The method can advantageously be carried out using or in connection with an embodiment of the aforementioned sensor device in order to calibrate the sensor device. Thus, by executing the method by means of the induced magnetic field, a, for example regular, calibration with regard to a sensitivity and also a directional dependency of the sensor device can be carried out during operation. In the determination step, a microwave frequency can be selected at which a variation in the fluorescence signal can be observed as a function of the internal magnetic field. The predetermined signal property can represent a minimum of the light intensity.

According to one embodiment, the method can have 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 can be carried out before the step of applying the magnetic field signal. In the determination step, 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 from, for example, an external magnetic field can be taken into account in order to enable precise calibration.

Furthermore, in the step of applying the magnetic field signal, a magnetic field signal can be applied which is suitable for generating a periodically varying internal magnetic field. Such an embodiment offers the advantage that, during the calibration, a change in the fluorescence signal is filtered out in a simple manner varies with the known frequency of the periodically varying magnetic field. In this way, interference from external magnetic fields on the calibration can be minimized.

• Anlegen eines Mikrowellensignals zum Erzeugen der Mikrowellen an die zumindest eine Mikrowellenantenne, um ein Frequenzspektrum der Mikrowellen zu durchlaufen;
• Auswerten des Fluoreszenzsignals ansprechend auf das angelegte Mikrowellensignal, um zumindest eine Mikrowellenfrequenz, bei der eine vorbestimmte Signaleigenschaft auftritt, in dem Frequenzspektrum zu bestimmen;
• Einstellen des Mikrowellensignals, um Mikrowellen mit einer im Schritt des Bestimmens bestimmten Mikrowellenfrequenz zu erzeugen;
• Verstellen des Mikrowellensignals ansprechend auf eine durch eine Änderung der Messgröße bedingte Verschiebung der vorbestimmten Signaleigenschaft, um eine Frequenz der Mikrowellen um die bestimmte Mikrowellenfrequenz herum zu variieren, bis eine neue Mikrowellenfrequenz gefunden ist, bei der die verschobene vorbestimmte Signaleigenschaft auftritt; und
• Berechnen der Messgröße unter Verwendung der Mikrowellenfrequenz und der neuen Mikrowellenfrequenz.

A method for detecting a measured variable is also presented, the method being executable in connection with a sensor device which has 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 applying microwaves to the crystal body and a Has detection device for detecting at least one signal property of a fluorescence signal from the crystal body, the method having at least the following steps:

• Applying a microwave signal for generating the microwaves to the at least one microwave antenna in order to sweep through a frequency spectrum of the microwaves;
• Evaluating the fluorescence signal in response to the applied microwave signal in order to determine at least one microwave frequency at which a predetermined signal property occurs in the frequency spectrum;
• 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 property caused by a change in the measured variable in order to vary a frequency of the microwaves around the specific microwave frequency until a new microwave frequency is found at which the shifted predetermined signal property occurs; and
• Calculate the measured variable using the microwave frequency and the new microwave frequency.

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 device. The method can advantageously be carried out using or in connection with an embodiment of the aforementioned sensor device in order to acquire at least one measured variable. Tracking a shift of the at least one minimum, for example ODMR minima (ODMR = Optically Detected Magnetic Resonance; optically detected magnetic resonance), can be simplified and accelerated by executing the method, since a complete scanning of the microwave spectrum of the measured variable is not necessary for every change is.

According to one embodiment, in the step of calculating, the measured variable can be calculated using the calibration data that are generated according to one embodiment of the above-mentioned method for calibration. Such an embodiment offers the advantage that a precise and reliable determination of the measured variable can be realized even under changing environmental conditions.

The method can also have a step of applying a magnetic field signal to generate an internal magnetic field, which can be applied to the crystal body, to the at least one microwave antenna in order to generate an internal magnetic field that varies periodically with an excitation frequency. In this case, the microwave signal can be adjusted in the adjustment step until a frequency component of the fluorescence signal that is correlated with the excitation frequency and assigned to a predetermined signal property is maximum in order 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, the fluorescence signal can be advantageously modulated using an induced alternating magnetic field. Via the alternating magnetic field in one direction, spatial directions to which the at least one predetermined signal property reacts can also be easily and reliably identified and compared via an alternating shift in the microwave frequency at which the at least one predetermined signal property can be detected.

In this case, and additionally or alternatively in the calibration method, the magnetic field signal can be applied to the at least one microwave antenna and at least one further magnetic field signal to at least one further microwave antenna or to at least one electrical coil in the step of applying the magnetic field signal. The magnetic field signal and the at least one further magnetic field signal can differ from one another with regard to a frequency or a phase. Such an embodiment offers the advantage that via an alternating magnetic field with different frequencies or different phases in different spatial directions via an alternating shift in the microwave frequency at which the at least one predetermined signal property of the fluorescence can be detected, also spatial directions in which the at least one predetermined Signal property reacts, can be identified and compared easily and reliably.

Furthermore, the method can have a step of changing the microwave signal to a frequency of the microwaves with a To vary the excitation frequency periodically around the specific microwave frequency. In this case, the microwave signal can be adjusted in the adjustment step until a frequency component of the fluorescence signal that is correlated with the excitation frequency and assigned to a predetermined signal property is maximum in order to find the new microwave frequency. Such an embodiment offers the advantage that no internal magnetic field is required, and measurements can also be made in several spatial directions without the need for additional coils.

The approach presented here also creates a control device which is designed to carry out, control or implement the steps of a variant of a method presented here in corresponding devices.

The object on which the invention is based can also be achieved quickly and efficiently by means of this embodiment variant of the invention in the form of a control device.

For this purpose, the control device can have at least one processing unit for processing signals or data, at least one storage unit for storing signals or data, at least one interface to a sensor or an actuator for reading in sensor signals from the sensor or for outputting control signals to the actuator and / or have at least one communication interface for reading in or outputting data that is embedded in a communication protocol. The computing unit can be, for example, a signal processor, a microcontroller or the like, wherein the storage unit can be a flash memory, an EPROM or a magnetic storage unit. The communication interface can be designed to read in or output data wirelessly and / or wired, a communication interface that can read in or output wired data, for example, can read this data electrically or optically from a corresponding data transmission line or output it into a corresponding data transmission line.

In the present case, a control device can be understood to mean an electrical device that processes sensor signals and outputs control and / or data signals as a function thereof. The control device can have an interface which can be designed in terms of hardware and / or software. In the case of a hardware design, the interfaces can, for example, be part of a so-called system ASIC, which contains a wide variety of functions of the control device. However, it is also possible that the interfaces are separate, integrated circuits or at least partially consist of discrete components. In the case of a software-based design, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

In an advantageous embodiment, the control device controls a sensor device, more precisely the light source, the detection device and the application device of an embodiment of the aforementioned sensor device. For this purpose, the control device can, for example, access the fluorescence signal from the detection device. The control device can be designed to control the light source and the application device.

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 or an optical memory, and for performing, implementing and / or controlling the steps of the method according to one of the embodiments described above is also advantageous is used, especially when the program product or program is executed on a computer or device.

Devices and methods according to embodiments can be designed to use or apply an ODMR method (ODMR = Optically Detected Magnetic Resonance; optically detected magnetic resonance). In particular, a behavior of such defects in a crystal body can be used to show fluorescence at one wavelength in the normal state with optical excitation. If, in addition to the optical excitation, microwave radiation is radiated in, the fluorescence collapses at a certain frequency, since the electrons are raised to a higher energy level in this case and recombine from there in a nonradiative manner. When a magnetic field is applied, the energy level is split, known as Zeeman splitting, and when the fluorescence is plotted against the frequency of the microwave excitation, based on a single defect, there are in particular two minima in the fluorescence spectrum, the frequency of which is proportional to the magnetic field strength.

• 1 eine schematische Darstellung einer Stickstoff-Fehlstelle in einem Diamantgitter;
• 2 bis 7 Energieschemata und Diagramme zu Fluoreszenzeigenschaften gemäß Ausführungsbeispielen;
• 8 eine schematische Darstellung einer Sensorvorrichtung gemäß einem Ausführungsbeispiel;
• 9 und 10 schematische Darstellungen einer Induktion von Magnetfeldern um einen Diamanten gemäß Ausführungsbeispielen;
• 11 bis 13 schematische Darstellungen und Diagramme zur Richtungsabhängigkeit einer Fluoreszenzmessung gemäß einem Ausführungsbeispiel;
• 14 bis 19 Diagramme zur Fluoreszenzmessung bei zusätzlicher Mikrowellenanregung und Magnetfeldanregung gemäß einem Ausführungsbeispiel;
• 20 ein Ablaufdiagramm eines Verfahrens zum Kalibrieren gemäß einem Ausführungsbeispiel;
• 21 ein Ablaufdiagramm eines Verfahrens zum Erfassen gemäß einem Ausführungsbeispiel;
• 22 ein Ablaufdiagramm eines Messprozesses gemäß einem Ausführungsbeispiel; und
• 23 bis 28 Diagramme zur Fluoreszenzmessung bei zusätzlicher Mikrowellenanregung gemäß einem Ausführungsbeispiel.

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

• 1 a schematic representation of a nitrogen vacancy in a diamond lattice;
• 2 until 7th Energy schemes and diagrams for fluorescence properties according to exemplary embodiments;
• 8th a schematic representation of a sensor device according to an embodiment;
• 9 and 10 schematic representations of an induction of magnetic fields around a diamond according to exemplary embodiments;
• 11th until 13th schematic representations and diagrams for the directional dependency of a fluorescence measurement according to an exemplary embodiment;
• 14th until 19th Diagrams for fluorescence measurement with additional microwave excitation and magnetic field excitation according to an embodiment;
• 20th a flowchart of a method for calibration according to an embodiment;
• 21 a flowchart of a method for detection according to an embodiment;
• 22nd a flowchart of a measurement process according to an embodiment; and
• 23 until 28 Diagrams for fluorescence measurement with additional microwave excitation according to an embodiment.

In the following description of advantageous exemplary embodiments of the present invention, identical or similar reference symbols are used for the elements shown in the various figures and having a similar effect, a repeated description of these elements being dispensed with. Furthermore, exemplary embodiments are described below merely by way of example on the basis of nitrogen defects in a diamond lattice or diamond.

1 shows a schematic representation of a nitrogen vacancy 105 in a diamond lattice 100 or diamond 100 . The nitrogen void 105 can also be used as a nitrogen vacancy center 105 or NV center 105 are designated. A carbon atom is replaced by a nitrogen atom 110 replaced, with a directly adjacent carbon atom in the diamond lattice 100 missing and thus the nitrogen deficiency 105 results.

2 until 7th show energy schemes and diagrams for fluorescence properties according to exemplary embodiments. Here shows 2 a power scheme 200 without microwave excitation and without magnetic field excitation, with excitation light hv 210, a fluorescence signal 220 and three states ³ A, ³ E and ¹ A as well as respective energy levels m _S = 0 and m _S = ± 1 for the states ³ A and ³ E with respect to electrons are shown.

3 shows a diagram 300 to the power scheme 2 . In the diagram 300 is on the abscissa axis 302 a microwave frequency is plotted in megahertz or MHz and is on the ordinate axis 304 a fluorescence is plotted in arbitrary units, with a on the ordinate axis 304 parallel arrow 306 a rising magnetic field B symbolizes. Furthermore, in 3 exemplary four characteristic curves or graphs 310 , 312 , 314 and 316 which represent a fluorescence curve for magnetic fields of different strength. A first graph 310 represents a magnetic field with the strength 0 , B = 0; a second graph 312 represents, for example, a magnetic field with a strength of 2.8 mT; a third graph 314 represents, for example, a magnetic field with the strength of 5.8 mT; a fourth graph 360 represents, for example, a magnetic field with a strength of 8.3 mT. Fluorescence minima are only exemplary for the second graph 312 denoted by ω ₁ and ω _2. A mark 320 on the first graph 310 represents the facts from the energy scheme of 2, d . H. without magnetic field (B = 0) and without microwave excitation or a microwave frequency f ≠ 2.9 GHz.

4th shows a power scheme 400 with microwave excitation and without magnetic field excitation, with excitation light hv 210, microwave radiation 430 and three states ³ A, ³ E and ¹ A as well as respective energy levels ms = 0 and m _S = ± 1 for the states ³ A and ³ E with regard to electrons are shown.

5 shows a diagram 500 to the power scheme 4th . The diagram 500 in 5 corresponds to the diagram 3 except that a mark 520 on the first graph 310 the facts from the energy scheme of 4th represented, ie without a magnetic field (B = 0) and with microwave excitation or a microwave frequency f = 2.9 GHz. The mark 520 is here in a region of a minimum or fluorescence minimum of the first graph 310 arranged.

6th shows a power scheme 600 with microwave excitation and with magnetic field excitation, with excitation light hv 210, microwave radiation 430 and three states ³ A, ³ E and ¹ A as well as respective energy levels ms = 0 and m _S = ± 1 for the states ³ A and ³ E with regard to electrons are shown. Even if it's in 6th is not explicitly or differently shown, the states ³ E m _S = ± 1 also split up when a magnetic field is applied like the states ³ A m _S = ± 1 due to Zeeman splitting. The states ³ E thus have a further energy level or two separate energy levels ms = + 1 and ms = -1.

7th shows a diagram 700 to the power scheme 6th . The diagram 700 in 7th corresponds to the diagram 3 respectively. 5 except that two marks 720 and 725 on the second graph 312 the facts from the energy scheme of 6th represent, ie with a magnetic field (B ≠ 0) and with variable microwave excitation or a microwave frequency. The markings 720 and 725 are each in a range of a minimum or fluorescence minimum of the second graph 312 arranged. For example, is a first mark 720 arranged in the area of a first minimum ω ₁ and is a second marking 725 arranged in the region of a second minimum ω ₂ .

With reference to the 2 until 7th In other words and in summary terms, energy schemes and diagrams with regard to a mode of operation of a magnetic field measurement via a fluorescence measurement with additional microwave excitation or an example for a measurement of magnetic fields are shown. Nitrogen vacancies in diamond indicate that in 2 shown diagram or energy scheme 200 shown energy spectrum at room temperature. In the normal state, ie without microwaves and without a magnetic field, a nitrogen defect shows fluorescence at a wavelength of 630 nm upon optical excitation. If the excitation light is used in addition to the optical excitation 210 nor microwave radiation 430 a, there is a collapse in fluorescence at 2.88 GHz, since in this case the electrons _{are lifted from the level m S} = ± 1 of the state ³ A to the level m _S = ± 1 of the state ³ E and from there Recombine non-radiating. In the case of an external magnetic field, the level m _S = ± 1 is split (Zeeman splitting) and when the fluorescence is plotted over the frequency of the microwave _{excitation, two minima, for example ω 1} and ω ₂ , appear in the fluorescence spectrum, the frequency of which is proportional to magnetic field strength B is. A magnetic field sensitivity is defined by a minimally resolvable frequency shift and can reach a few pT / √Hz. This process is also known as ODMR (Optically Detected Magnetic Resonance; optically detected magnetic resonance). If the microwave frequency agrees with the energy gap between the state ³ A m _S = 0 and the level m _S = ± 1, there is a collapse in fluorescence. In the case of an external magnetic field, the level m _S = ± 1 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.

8th shows a schematic representation of a sensor device 800 according to an embodiment. The sensor device 800 according to the in 8th illustrated embodiment a diamond 810 with at least one nitrogen void, a light source 820 for irradiating the diamond 810 with excitation light 210 or for an optical stimulation of the diamond 810 , for example only a microwave antenna 830 for impacting the diamond 810 with microwaves or microwave radiation, a detection device 840 for detecting a light intensity of a fluorescence signal 220 of the diamond 810 with a detector 850 and an optical filter 855 , a mooring device 860 with a microwave source 870 and a power source 880 for an internal magnetic field and a control unit 890 or a readout circuit 890 on.

The diamond 810 is between the light source 820 and the detection device 840 arranged. Here is the optical filter 855 between the diamond 810 and the detector 850 arranged. The microwave antenna 830 is the diamond 810 at least partially arranged surrounding it. The microwave antenna 830 can transmit signals with the mooring device 860 or the microwave source 870 and the power source 880 tied together.

The mooring device 860 is designed to generate a microwave signal for generating the microwaves and a magnetic field signal for generating an internal magnetic field Bmod with which the diamond 810 can be acted upon, to the microwave antenna 830 to put on.

The control unit 890 can transmit signals with the light source 820 , with the detection device 840 , more precisely with the detector 850 , and with the mooring device 860 or with the microwave source 870 and the power source 880 tied together. The control unit 890 is trained to handle the in 20th calibration procedure shown or a similar procedure described in 21 The method shown for detection or a similar method and / or the in 22nd to perform a measurement process or a similar measurement process.

In other words, shows 8th a schematic representation of an exemplary arrangement for a sensor or the sensor device 800 based on nitrogen vacancies or NV centers in the diamond 810 . The diamond 810 is in operation of the sensor device 800 for excitation by the light source 820 irradiated and from the microwave source 870 via the microwave antenna 830 exposed to microwaves. The fluorescence signal 220 is from the optical filter 855 from the excitation light 210 separated and hits the detector 850 , which sends a measured value of a light intensity to the evaluation circuit 890 or to the control unit 890 passes on. The control unit 890 is designed to include the light source, among other things 820 and the Microwave source 870 to control. In addition is the power source 880 for the induction of the magnetic field Bmod to the microwave antenna 830 connected. Thus shows 8th an exemplary structure of the sensor device 800 based on NV centers in diamond 810 . The microwave source 880 is here electrical with the microwave antenna 830 connected, for example, from a wire with one or more turns around the diamond 810 is realized and designed to eliminate the nitrogen vacancies in the diamond 810 stimulate with microwaves. Alternatively, other methods of making coils or microwave antennas can be used, such as e.g. B. a use of conductor tracks on a circuit board.

9 shows a schematic representation of an induction of a magnetic field or internal magnetic field Bmod around a diamond 810 according to an embodiment. Shown here are in 9 the diamond 810 as well as the microwave antenna 830 the sensor device 8th or a similar sensor device, the internal magnetic field Bmod or magnetic field Bmod and a magnetic field signal I _mod or additional current I _mod or induction _{current I mod} that is sent to the microwave antenna 830 is applied. Thus shows 9 an induction of the magnetic field Bmod around the diamond 810 by applying the additional current I _mod 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 an embodiment. In other words, shows 10 a generation of the magnetic fields B _y and B _x in two spatial directions by an arrangement of several coils 830 and 1030 or microwave antennas 830 and 1030 .

With reference to 9 and 10 it should be noted that the microwave antenna 830 is used to induce a magnetic field Bmod that acts on the diamond 810 works. This is done in the microwave antenna 830 a direct or alternating current is impressed in the form of the induction current I _mod , which generates a corresponding magnetic field Bmod, as shown in FIG 9 is shown. In order to be able to generate magnetic fields B _y and B _x in more than one spatial direction, in 10 provided more than one microwave antenna 830 to use as it is in 10 using another microwave antenna 1030 or electric coil 1030 is shown. Here are the microwave antenna 830 and the other microwave antenna 1030 or electric coil 1030 z. B. arranged orthogonally to one another. Will the microwave antenna 830 used to generate an alternating magnetic field Bmod, the AC power source used for this purpose (frequencies, e.g. in the kHz range) and the microwave source (frequencies in the GHz range) can be influenced by an electrical filter, e.g. B. a network of passive components can be prevented.

11th shows a schematic representation of the directional dependency of a fluorescence measurement according to an embodiment. The diamond is shown here 810 and the microwave antenna 830 the sensor device 8th or a similar sensor device and an internal magnetic field Bmod, a measuring direction 1101 and symbolically an alignment 1102 of individual nitrogen vacancies in the four crystal directions in the diamond 810 . In other words, shows 11th an arrangement for determining a sensitivity of four ODMR minima or fluorescence minima, which correspond to the four crystal directions in diamond 810 related to magnetic fields Bmod in the measuring direction 1101 by applying the internal magnetic field Bmod or a reference field Bmod, which is transmitted via the microwave antenna 830 or an electrical coil is induced.

12th shows a diagram 1200 for directional dependence of a fluorescence measurement according to an embodiment. The diagram 1200 in 12th shows a light intensity 1204 of a fluorescence signal on the ordinate axis as a function of a microwave frequency 1202 on the abscissa axis for the facts 11th . In 12th a shift of individual ODMR minima by the internal magnetic field Bmod for an optically detected magnetic resonance (ODMR) is illustrated. Here are in the diagram 1200 four pairs of ODMR minima 1210 , 1212 , 1214 and 1216 drawn. A first pair of ODMR minima 1210 refers to a first crystal direction of the diamond and shows a first displacement distance. A second pair of ODMR minima 1212 refers to a second crystal direction of the diamond and shows a second displacement distance. The second displacement distance is less than the first displacement distance. A third pair of ODMR minima 1214 refers to a third crystal direction of the diamond and shows a third displacement distance. The third shift distance is less than the second shift distance. A fourth pair of ODMR minima 1216 refers to a fourth crystal direction of the diamond and shows a fourth displacement distance. The fourth shift distance is less than the third shift distance. Specifically, the fourth shift distance is zero, with the fourth pair of ODMR minima 1216 is not shifted relative to each other.

13th shows a diagram 1300 for directional dependence of a fluorescence measurement according to an embodiment. The diagram 1300 in 13th shows a relative sensitivity 1304 based on four crystal directions in the measuring direction on the ordinate axis depending on one crystal direction 1302 on the abscissa axis for the facts 11th respectively. 12th . Here, a first crystal direction is a first bar 1310 assigned with a first sensitivity value. A second crystal direction is a second bar 1312 assigned with a second sensitivity value. The second sensitivity value is lower than the first sensitivity value. A third crystal direction is a third bar 1314 assigned with a third sensitivity value. The third sensitivity value is lower than the second sensitivity value. A fourth crystal direction is a fourth bar 1316 assigned with the amount or a fourth sensitivity value of zero.

14th until 19th show diagrams for fluorescence measurement with additional microwave excitation and magnetic field excitation according to an embodiment. The fluorescence measurement is carried out using the in 8th illustrated sensor device or a similar sensor device or in connection with at least one of the methods 20th and 21 feasible.

14th shows a diagram 1400 an ODMR spectrum for different internally generated magnetic fields Bmod as a function of a microwave frequency according to an embodiment. On the abscissa axis 1402 a relative change in microwave frequency is plotted in megahertz (MHz) and on the ordinate axis 1404 an ODMR signal is plotted in arbitrary units. Also in the diagram are 1400 three graphs 1410 , 1412 and 1414 drawn. The three graphs 1410 , 1412 and 1414 each show, by way of example, only one minimum of the two minima generated from the Zeeman splitting 2 until 7th . Here the ODMR spectrum is locked to the minimum. A first graph 1410 represents a first ODMR signal with an applied magnetic field B _mod = 0 or without an applied magnetic field. A second graph 1412 represents a second ODMR signal with an applied magnetic field B _mod = + B. A third graph 1414 represents a third ODMR signal with an applied magnetic field B _mod = -B.

15th shows a signal-time diagram 1500 based on the ODMR spectrum 14th . More precisely, a variation over time of a magnetic field generated by a microwave antenna or coil is Bmod 1510 and a resulting ODMR output signal 1520 for constant microwave excitation. On the abscissa axis 1502 the time in seconds (s) multiplied by 10 ^{-3 is} plotted on the ordinate axis 1504 signals are plotted in arbitrary units.

16 shows a diagram 1600 a frequency spectrum or frequency content of the signals 15th . More precisely, the diagram shows 1600 a frequency spectrum of the signals 15th in the event that the microwave frequency coincides with a position of the ODMR minimum determined by an external magnetic field. On the abscissa axis 1602 a frequency is plotted in Hertz (Hz) and on the ordinate axis 1604 a Fourier transformation is plotted in arbitrary units. A first graph 1610 represents the Fourier transform of the magnetic field Bmod and a second graph 1620 represents the Fourier transform of the ODMR signal.

17th shows a diagram 1700 an ODMR spectrum for different internally generated magnetic fields Bmod as a function of a microwave frequency according to an embodiment. The diagram 1700 in 17th corresponds to the diagram 14th with the exception that the ODMR spectrum is shown with additional exposure to an external constant magnetic field. Here are the three graphs 1410 , 1412 and 1414 shifted due to the external magnetic field.

18th shows a signal-time diagram 1800 based on the ODMR spectrum 17th . The signal-time diagram 1800 in 18th corresponds to the signal-time diagram 15th except that a waveform of the ODMR output signal 1520 from an in 15th signal curve shown differs.

19th shows a diagram 1900 a frequency spectrum or frequency content of the signals 18th . The diagram 1900 in 19th corresponds to the diagram 16 except that the second graph 1620 , which represents the Fourier transform of the ODMR signal, shows a different course than the second graph from 16 . In other words, shows 19th a frequency spectrum of the signals 18th in the event that the microwave frequency does not coincide with a position of the ODMR minimum determined by an external magnetic field.

20th shows a flow chart of a method 2000 for calibration according to an embodiment. The procedure 2000 is executable to calibrate a sensor device. In particular, the procedure 2000 executable to the sensor device 8th or calibrate a similar sensor device. Generally speaking, the procedure is 2000 can be carried out for calibration in order to calibrate a sensor device which has a diamond with at least one nitrogen defect, a light source for irradiating the diamond with excitation light, at least one microwave antenna for applying microwaves to the diamond and a detection device for detecting a Having light intensity of a fluorescent signal from the diamond.

In the process 2000 calibration is done in one step 2010 of applying a microwave signal for generating the microwaves is applied to the at least one microwave antenna of the sensor device. Below is a further step 2020 the application of a magnetic field signal for generating an internal magnetic field, with which the diamond can be applied, applied to the at least one microwave antenna. Then in one step 2030 of determining at least one microwave frequency at which a minimum of the light intensity 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 measurement quantity.

According to the in 20th illustrated embodiment has the method 2000 a further step for calibration 2040 of determining, at which at least one reference frequency, at which a reference minimum of the light intensity occurs, is determined in the frequency spectrum using the fluorescence signal. The step 2040 the determination is before the step 2020 the application of the magnetic field signal can be carried out. In particular, the step 2040 of determining between the step 2010 the application of the microwave signal and the step 2020 of the application of the magnetic field signal. This is then done in 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.

In other words, by performing the method 2000 for calibration using an internal magnetic field, e.g. B. is generated via a microwave antenna or coil or in some other known manner, a sensitivity of the sensor device to magnetic fields can be calibrated during operation. For this purpose, a magnetic field with a known strength is generated and the associated shift of one or more minima in the ODMR spectrum is measured. These calibration data are stored, for example, and used in the following to calculate the vectorial size of an external magnetic field from measured shifts in the ODMR minima.

Since simultaneously applied external magnetic fields can lead to interference during calibration by means of a magnetic field generated in the sensor device, a relative measurement of the ODMR signal is carried out according to one embodiment. You can do this in step 2040 of determining and in step 2030 of determining z. B. two measurements can be carried out and compared immediately before and after switching on or applying the internal magnetic field. Optionally, a periodically varying magnetic field can be generated or applied. The shifts in the ODMR spectra for such a varying field Bmod are exemplified in FIG 14th (only one peak of the two minima generated by Zeeman splitting is shown). During an execution of the procedure 2000 For calibration, only the shift in the ODMR spectrum can be filtered out, which varies with the known frequency of the generated magnetic field. In this way, the influence of external magnetic fields on the calibration can be minimized.

According to one exemplary embodiment, a direction-dependent sensitivity of the individual minima can also be assigned to the spatial directions of the sensor device. NV centers or nitrogen defects in diamond are each aligned with one of the four crystal directions in diamond and are also sensitive to magnetic fields in this direction. Depending on a direction of the magnetic field, the four pairs of minima associated with these four alignments are shifted to different degrees in the ODMR spectrum, as shown in FIG 12th is shown. Using the at least one microwave antenna or coil, which is arranged in the desired or several desired measuring directions, and measuring the displacement of the various ODMR minima due to the generated magnetic fields, the sensitivities of these minima to the measuring direction can be determined. This principle is exemplified in the 11th until 13th shown. The measured values are stored and used to calculate a vector of an external magnetic field from a measured shift in the minima. The calibration of several spatial directions by several microwave antennas and / or coils can, for. B. be carried out one after the other. Alternatively, it is possible to assign currents or magnetic field signals to different microwave antennas and / or coils that differ in frequencies or phases. It is thus also possible to assign the relative shift of the ODMR spectra to the measurement directions via the identification using frequency or phase information simultaneously.

21 shows a flow chart of a method 2100 for acquiring a measured variable according to an exemplary embodiment. In particular, the procedure 2100 for detection in connection with or using the sensor device 8th or a similar sensor device. Generally speaking, the procedure is 2100 can be carried out for detection in connection with or using a sensor device which has a diamond with at least one nitrogen defect and a light source for irradiating the diamond Having excitation light, at least one microwave antenna for exposing the diamond to microwaves and a detection device for detecting a light intensity of a fluorescence signal from the diamond.

In the process 2100 to capture is in one step 2110 of applying a microwave signal for generating the microwaves is applied to the at least one microwave antenna in order to traverse a frequency spectrum of the microwaves. Then in one step 2120 of the evaluation, the fluorescence signal is evaluated in response to the applied microwave signal in order to determine at least one microwave frequency at which a minimum of the light intensity occurs in the frequency spectrum. Then in one step 2130 of setting, the microwave signal is set to generate microwaves with a microwave frequency determined in the step of determining. Below is in one step 2140 of adjusting adjusts the microwave signal in response to a shift in the minimum caused by a change in the measured variable in order to vary a frequency of the microwaves around the specific microwave frequency until a new microwave frequency is found at which the shifted minimum in the light intensity occurs. Finally, in one step 2150 after calculating, the measured variable is calculated using the microwave frequency and the new microwave frequency.

According to one embodiment, step 2150 of calculating the measured variable using the calibration data calculated according to the method for calibrating 20th or a similar process. In other words, in step 2150 of calculating the calibration data used after the method for calibrating out 20th or a similar process.

Optionally, the procedure 2100 to capture one step 2160 the application of a magnetic field signal or a step 2170 of changing the microwave signal. The step 2160 the application of a magnetic field signal or the step 2170 of changing the microwave signal are between step 2130 the setting of the microwave signal and the step 2140 the adjustment of the microwave signal can be carried out.

In step 2160 After application, a magnetic field signal for generating an internal magnetic field, with 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 varies periodically with an excitation frequency. This is then done in step 2140 of the adjustment adjusts the microwave signal until a frequency component of the fluorescence signal that is correlated with the excitation frequency and assigned to a minimum of the light intensity is maximum in order to find the new microwave frequency. According to one embodiment, in step 2160 applying the magnetic field signal, the magnetic field signal is applied to the at least one microwave antenna and at least one further magnetic field signal is applied to at least one further microwave antenna or to at least one electrical coil. Here, the magnetic field signal and the at least one further magnetic field signal differ from one another with regard to a frequency or a phase.

In step 2170 of changing, the microwave signal is changed in order to periodically vary a frequency of the microwaves with an excitation frequency around the specific microwave frequency. This is then done in step 2140 of the adjustment adjusts the microwave signal until a frequency component of the fluorescence signal that is correlated with the excitation frequency and assigned to a minimum of the light intensity is maximum in order to find the new microwave frequency.

22nd shows a flow chart of a measurement process 2200 according to an embodiment. In other words, shows 22nd an example of a measurement sequence or a measurement process 2200 , where an internally generated magnetic field is used to modulate an ODMR spectrum. The measurement process 2200 is related to the method of acquisition 21 or a similar procedure.

With a block 2201 the measurement starts. After that, at a block 2202 an ODMR spectrum recorded over all microwave frequencies. The block 2202 is here comparable to the step of applying the microwave signal in the method for detecting off 21 . Then the measuring process goes 2200 to a block 2203 above, at which a position (microwave frequency) of the minima in the ODMR spectrum is identified. The block 2203 is comparable to the step of evaluating the fluorescence signal in the method for detecting off 21 . The following is in a block 2204 the microwave frequency is set to the position of the relevant minimum. The block 2204 is comparable to the step of setting the microwave signal in the method for detecting off 21 .

Then the measuring process goes 2200 to a block 2205 over, in which an internal alternating magnetic field with a frequency or excitation frequency fmag is generated. The block 2205 is comparable to the step of applying the magnetic field signal according to an exemplary embodiment of the method for detecting off 21 .

The measuring process then arrives 2200 to a decision block 2206 , which checks whether a frequency component fmag of the ODMR signal is maximum. If so, the process goes to a block 2207 over, at which the magnitude of the external magnetic field is determined from the microwave frequency. The block 2207 is comparable to the step of calculating in the method for acquiring from 21 . From the block 2207 the measuring process jumps 2200 loops back to the decision block 2206 .

If at the decision block 2206 it is determined that the frequency component fmag of the ODMR signal is not at its maximum, the measurement process continues 2200 to a block 2208 over, which determines whether the minimum is presumed to be near the original frequency. If this is not the case, the measuring process works 2200 back to the block 2202 . If so, the measurement process continues 2200 to a block 2209 , in which a systematic variation of the microwave frequency is carried out from the previous position in both directions. From the block 2207 the measuring process arrives 2200 back to the decision block 2206 .

With reference to 21 and 22nd is the procedure below 2100 for recording or the measuring process 2200 summarized and presented in other words.

It becomes a process 2100 for acquisition or a measurement process 2200 presented, in which internally generated magnetic fields are used for modulation in order to easily determine and track a position and shift of the individual minima in the ODMR spectrum of the sensor device. If the measured variable changes, e.g. B. an external magnetic field, a temperature or a mechanical tension, shift the microwave frequencies at which the individual minima of the fluorescence occur. This shift is discussed in the procedure 2100 for recording or during the measurement process 2200 determines the external measurand.

Conventionally, in order to determine shifts in the minima, an intensity of the fluorescence is often measured while the microwave frequency is being changed. In the spectrum recorded in this way, 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 exemplary embodiments, however, in the method 2100 for recording or during the measurement 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 passed through regularly for recording the spectrum can be reduced. This is done in the procedure 2100 for recording or during the measurement process 2200 First a complete ODMR spectrum was recorded in order to identify positions of the minima, as shown in the step 2110 the application of the microwave signal and the step 2120 the evaluation of the fluorescence signal or in the blocks 2202 and 2203 is shown. The microwave source is then set to the frequency of the minimum to be measured, as in step 2130 of setting the microwave signal or in the block 2204 is shown.

Now is in the block 2205 or in step 2160 the application of the magnetic field signal internally in the sensor device a periodically changing, z. B. sinusoidal as in 15th respectively. 18th shown, magnetic field B mod induced in the direction to which this minimum is sensitive. The frequency fmod of the alternating field is set in such a way that it is higher than a desired bandwidth of the sensor device, but less than a reaction time of the nitrogen defects. Due to the internally generated magnetic field, the position of the minimum varies, as in 14th shown around the previously determined, mean microwave frequency. Thus, the intensity of the fluorescence signal measured with the microwave frequency kept constant also changes periodically at twice the frequency of the applied magnetic field (2fmod), as in FIG 15th and 16 shown. An external signal or a measured variable, such as B. an external magnetic field, leads to a shift in the mean microwave frequency around which the ODMR minimum oscillates periodically, as shown in 17th is shown. For this reason, the observed fluorescence signal changes if the microwave frequency remains the same. In particular, the proportion of the fluorescence signal that has twice the excitation frequency is reduced, as in FIG 18th and 19th is shown. The portion of the fluorescence signal with twice the excitation frequency is maximal when the microwave frequency coincides with the frequency of the ODMR minimum, which is assumed without the internal magnetic field. By evaluating this signal component, a change in an external measured value can consequently be easily detected and an evaluation concept similar to a so-called lock-in method can be implemented.

If such a change in the external measured value is detected, in the block 2209 the microwave frequency varies in both directions of the original frequency, ie to higher and lower frequencies, until the portion in the ODRM signal with twice the excitation frequency (2fmod) is maximum and the new microwave frequency of the shifted ODRM minimum is found. the end this position of the shifted minimum can e.g. B. optionally using the calibration values from the method for calibration 20th , the new measured value of the external measured variable can be determined. Only when the minimum cannot be found again due to a repeated variation of the microwave frequency is an ODMR spectrum recorded again in order to determine the position of the minima, as described above.

For a modulation in more than one measuring axis, several microwave antennas and / or several coils are used, for example. It is again conceivable to vary the frequency or phase of the induced magnetic fields with respect to one another in such a way that an assignment of the effect of the fields to the measuring axes is possible via this variation.

23 until 28 show diagrams for fluorescence measurement with additional microwave excitation according to an embodiment. The ones in the 23 until 28 The diagrams shown are similar to the diagrams shown in the 14th until 19th are shown. The fluorescence measurement is carried out using the in 8th illustrated sensor device or a similar sensor device or in connection with at least one of the methods 20th and 21 feasible.

23 shows a diagram 2300 an ODMR spectrum for a periodically varied frequency of the microwave excitation according to an embodiment. On the abscissa axis 2302 a change in the microwave frequency Δf _{MW is} plotted in megahertz (MHz) and on the ordinate axis 2304 an ODMR signal is plotted in arbitrary units. Also in the diagram is 2300 a graph 2310 shown, the example of only a minimum of the two minima generated by Zeeman splitting from the 2 until 7th represents. The ODMR signal is locked to the minimum here. In the readout concept shown here, the microwave frequency or frequency of the microwave excitation is varied periodically, here z. B. in the by lines 2320 and 2330 marked limits, resulting in an output signal with properties similar to those in the 14th until 19th without any modulation by an internally generated magnetic field. A shift in the ODMR minima due to external measured variables can be detected as described above.

24 shows a signal-time diagram 2400 based on the ODMR spectrum 23 . The signal-time diagram 2400 corresponds to the signal-time diagram 15th with the exception that instead of the generated magnetic field, the periodically varied microwave frequency Δf _MW 2410 is shown as a graph. In other words, shows 24 a variation of Δf _MW and the ODMR signal.

25th shows a diagram 2500 a frequency spectrum or frequency content of the ODMR signal 24 . the diagram 2500 corresponds to the diagram 16 except that only those represented by the graph 1620 represented Fourier transform of the ODMR signal is shown.

26th shows a diagram 2600 an ODMR spectrum for a periodically varied frequency of the microwave excitation according to an embodiment. The diagram 2600 in 26th corresponds to the diagram 23 with the exception that the ODMR spectrum is shown with additional exposure to an external constant magnetic field. Here is the graph 2310 shifted due to the external magnetic field.

27 shows a signal-time diagram 2700 based on the ODMR spectrum 26th . The signal-time diagram 2700 in 27 corresponds to the signal-time diagram 24 except that a waveform of the ODMR output signal 1520 from an in 24 signal curve shown differs.

28 shows a diagram 2800 a frequency spectrum or frequency content of the ODMR signal 27 . The diagram 2800 in 28 corresponds to the diagram 25th except that the graph 1620 , which represents the Fourier transform of the ODMR signal, shows a different course than the graph from 25th .

23 until 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 is varied periodically (by the previously determined frequency of a minimum in the ODMR spectrum). This leads to an output signal similar to that of an alternating magnetic field without one being applied. Changes in an external measured variable can be detected as described above. This means that measurements can be carried out in several spatial directions without the need for additional work through additional coils.

If an exemplary embodiment comprises an “and / or” link between a first feature and a second feature, this is to be read in such a way that the exemplary embodiment according to one embodiment has both the first feature and the second feature and, according to a further embodiment, either only the has the first feature or only the second feature.

Claims (14)

Sensor device (800) having the following features: 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 applying microwaves (430) to the crystal body (810); detection means (840, 850, 855) for detecting at least one signal property of a fluorescence signal (220) from the crystal body (810); and an application device (860, 870, 880) which is designed to generate a microwave signal for generating the microwaves (430) to cause the fluorescence signal (220) to break in, and a magnetic field signal (I _mod ) for generating an internal magnetic field ( B _mod ), with which the crystal body (810) can be acted upon in order to bring about a Zeeman effect, to be applied to the at least one microwave antenna (830; 1030), the application device (860) being a microwave source (870), a power source (880 ) and / or an electrical filter to minimize mutual interference between the microwave source (870) and the current source (880), the current source (880) being designed to supply a direct current or an alternating current _{as a magnetic field signal (I mod) to the at least one} Emboss the microwave antenna (830; 1030). Sensor device (800) according to Claim 1 with a control device (890) which can transmit signals to the light source (820), to the detection device (840, 850, 855) and to the application device (860, 870, 880). Sensor device (800) according to one of the preceding claims, with at least one electrical coil (1030) for producing at least one further internal magnetic field, the at least one further internal magnetic field having a further field direction which differs from a field direction of the internal magnetic field (B _mod ) differs. Method (2000) for calibrating a sensor device (800), wherein the sensor device (800) has 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 microwave antenna (830; 1030) for subjecting the crystal body (810) to microwaves (430) and a detection device (840, 850, 855) for detecting at least one signal property of a fluorescence signal (220) from the crystal body (810), the method (2000) comprises at least the following steps: applying (2010) a microwave signal for generating the microwaves (430) to the at least one microwave antenna (830; 1030) in order to cause the fluorescence signal (220) to break in; Applying (2020) a magnetic field signal (I _mod ) for generating an internal magnetic field (B _mod ), with which the crystal body (810) can be acted upon, to the at least one microwave antenna (830; 1030) in order to bring about a Zeeman effect, wherein A direct current or an alternating current is impressed into the at least one microwave antenna (830; 1030) as a magnetic field _{signal (I mod);} 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 _mod ) in order to obtain calibration data for use in detecting a measured variable to create. Procedure (2000) according to Claim 4 , with a step (2040) of determining at least one reference frequency at which a reference signal property occurs in the frequency spectrum using the fluorescence signal (220), wherein the step (2040) of determining before the step (2020) of applying the magnetic field signal (I _mod ), wherein in 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 mod} ). Method (2000) according to one of the Claims 4 until 5 , in which, in the step (2020) of applying the magnetic field signal (I _mod ), a magnetic field signal (I _mod ) is applied which is suitable for generating a periodically varying internal magnetic field (B _mod). Method (2100) for detecting a measured variable, the method (2100) being executable in connection with a sensor device (800) which has 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 applying microwaves (430) to the crystal body (810) and a detection device (840, 850, 855) for detecting at least one signal property of a fluorescence signal (220) from the Diamonds (810), the method (2100) having at least the following steps: applying (2110) a microwave signal for generating the microwaves (430) to the at least one microwave antenna (830; 1030) in order to assign a frequency spectrum of the microwaves (430) go through to causing the fluorescence signal (220) to collapse; Evaluating (2120) the fluorescence signal (220) in response to the applied microwave signal in order to determine at least one microwave frequency at which a predefined signal property occurs in the frequency spectrum; Adjusting (2130) the microwave signal to generate microwaves (430) having a microwave frequency determined in the step (2120) of determining; Adjusting (2140) the microwave signal in response to a shift in the predefined signal property caused by a change in the measured variable in order to vary a frequency of the microwaves (430) around the determined microwave frequency until a new microwave frequency is found at which the shifted predefined signal property occurs ; and calculating (2150) the measured variable using the microwave frequency and the new microwave frequency. Method (2100) according to Claim 7 , in which, in the step (2150) of calculating, the measured variable is calculated using the calibration data obtained according to the method (2000) for calibrating in accordance with one of the Claims 4 until 6th are generated. Method (2100) according to one of the Claims 7 until 8th , with a step (2160) of applying a magnetic field signal (I _mod ) for generating an internal magnetic field (B _mod ), with which the crystal body (810) can be acted upon, to the at least one microwave antenna (830; 1030) in order to have a To generate excitation frequency periodically varying internal magnetic field (B _mod ) in order to bring about a Zeeman effect, a direct current or an alternating current being impressed into the at least one microwave antenna (830; 1030) _{as the magnetic field signal (I mod), wherein in step (2140} ) of the adjustment, the microwave signal is adjusted until a frequency component of the fluorescence signal (220) that is correlated with the excitation frequency and assigned to a predefined signal property is maximum in order to find the new microwave frequency. Method (2100) according to one of the Claims 4 until 6th and 9 in which in the step (2160) of applying the magnetic field _{signal (I mod} ) the magnetic field _{signal (I mod} ) to the at least one microwave antenna (830) and at least one further magnetic field signal to at least one further microwave antenna (1030) or to at least one electrical coil ( 1030) is applied, the magnetic field _{signal (I mod} ) and the at least one further magnetic field signal differing from one another with regard to a frequency or a phase. Method (2100) according to one of the Claims 7 until 8th , with a step (2170) of changing the microwave signal in order to vary a frequency of the microwaves (430) with an excitation frequency periodically around the determined microwave frequency, wherein in the step (2140) of adjusting the microwave signal is adjusted until one with the excitation frequency correlated frequency component of the fluorescence signal (220) assigned to a predefined signal property is maximum in order to find the new microwave frequency. Control unit (890) which is set up to carry out steps of a method (2000; 2100) according to one of the preceding claims in corresponding units. Computer program which is set up to carry out a method (2000; 2100) according to one of the preceding claims. Machine-readable storage medium on which the computer program is based Claim 13 is stored.

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