Diamond Sensor Unit

Abstract

This diamond sensor unit includes: a diamond having a color center having electron spin; an exciting light emitting unit for emitting exciting light onto the diamond; a first patch antenna for receiving electromagnetic waves; an electromagnetic wave emitting unit for emitting electromagnetic waves received by the first patch antenna onto the diamond; a detecting unit for detecting radiated light radiated from the color center of the diamond, after the exciting light and the electromagnetic waves have been emitted onto the diamond; and an optical waveguide for transmitting the exciting light and the radiated light.

Description

Technical Field

[0001] The present disclosure relates to a diamond sensor unit. This application claims priority based on Japanese Patent Application No. 2021-010937 filed on January 27, 2021, and incorporates all the descriptions described in the above Japanese application.

Background Art

[0002] Sensors using diamond NV centers are known. When a diamond NV center is used in combination with a microscope, it is configured as shown in FIG. 1, for example. That is, the LED 900 disposed on the substrate 912 emits green light for exciting the NV center of the diamond 904. The emitted light passes through the SPF (Short Pass Filter) 902 and then enters the diamond 904 disposed on the substrate 914. As a result, the electrons of the NV - center are excited. When the excited electrons return to the original ground state, red fluorescence is emitted from the diamond 904, and the fluorescence is collected by the lens 906, passes through the LPF (Long Pass Filter) 908, and is then detected by the photodiode 910 disposed on the substrate 916. Further, the diamond 904 is irradiated with microwaves generated by an external device (not shown). As a result, when it resonates and is excited with different spin states, the intensity of the red fluorescence from the diamond 904 changes. This change is detected by the photodiode 910. The lens 906 can be either a lens configuration of a high-performance optical microscope or a simple lens configuration.

[0003] The following Patent Document 1 discloses a scanning probe microscope (i.e., a frequency modulation type atomic force microscope (FM-AFM)) using a diamond NV center. Further, the following Patent Document 2 discloses a magnetic field detection device using a diamond NV center. The following Non-Patent Document 1 discloses a compact magnetic field detection device using a lens.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Non - Patent Documents

[0005]

Non - Patent Document 1

Summary of the Invention

[0006] A diamond sensor unit according to an aspect of the present disclosure includes a diamond having a color center with an electron spin, an excitation light irradiation unit that irradiates the diamond with excitation light, a first patch antenna that receives an electromagnetic wave, an electromagnetic wave irradiation unit that irradiates the diamond with the electromagnetic wave received by the first patch antenna, a detection unit that detects the emitted light radiated from the color center of the diamond after the excitation light and the electromagnetic wave are irradiated on the diamond, and an optical waveguide that transmits the excitation light and the emitted light.

Brief Description of the Drawings

[0007]

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DETAILED DESCRIPTION OF THE INVENTION

[0008] [Problems to be Solved by the Invention] When using a sensor for a high-voltage device such as a power device, the high voltage and large current that are instantaneously generated by the discharge, and the generation of a strong electromagnetic wave accompanying it may damage the light-emitting element and the light-receiving element. The configuration disclosed in Patent Document 1 cannot be adopted for a sensor used in a high-voltage environment.

[0009] Patent Document 2 discloses that a light-emitting element and a light-receiving element are arranged at a distance from a diamond and a microwave irradiation coil. However, since the excitation light and the emitted fluorescence are transmitted through the air as parallel light, they are diffused, and there is a limit to the separation distance. In particular, since the signal intensity of the fluorescence is weak, this becomes a problem.

[0010] Therefore, an object of the present disclosure is to provide a diamond sensor unit that can accurately detect a magnetic field or the like from a remote location without being damaged even in a high-voltage environment.

[0011] [Advantages of the Invention] According to the present disclosure, it is possible to provide a diamond sensor unit that can accurately measure a magnetic field, an electric field, etc. from a remote location without being damaged even in a high-voltage environment.

[0012] [Description of Embodiments of the Present Disclosure] The contents of the embodiments of the present disclosure will be listed and described. At least a part of the embodiments described below may be arbitrarily combined.

[0013] (1) The diamond sensor unit according to the first aspect of the present disclosure includes a diamond having a color center with an electron spin, an excitation light irradiation unit that irradiates the diamond with excitation light, a first patch antenna that receives an electromagnetic wave, an electromagnetic wave irradiation unit that irradiates the diamond with the electromagnetic wave received by the first patch antenna, a detection unit that detects the emitted light radiated from the color center of the diamond after the excitation light and the electromagnetic wave are irradiated on the diamond, and an optical waveguide that transmits the excitation light and the emitted light. Thereby, it is possible to accurately measure a magnetic field, an electric field, etc. from a remote location without being damaged even in a high-voltage environment. Further, by using a patch antenna as the receiving antenna for the electromagnetic wave, the degree of freedom in design is increased.

[0014] (2) The diamond sensor unit can further include a horn antenna or a second patch antenna that transmits the electromagnetic wave received by the first patch antenna. The horn antenna can transmit microwaves as the electromagnetic wave, and the second patch antenna can transmit microwaves, millimeter waves, or sub-millimeter waves as the electromagnetic wave. Thereby, the electromagnetic wave can be transmitted to the first patch antenna with good directivity, and the detection accuracy can be improved. Also, an electromagnetic wave with a frequency corresponding to the type of color center used can be transmitted, and sensors using not only NV centers but also Si-V centers, Ge-V centers, or Sn-V centers, etc. can be realized.

[0015] (3) The first patch antenna includes a plate-shaped conductive member that receives the electromagnetic wave, and may be disposed on the electrical device or electrical wiring that is the detection target. The first patch antenna may be disposed such that the conductive member is parallel to the equipotential surface formed by the detection target. Thereby, when the electromagnetic wave is received by the first patch antenna, the influence from the electric field formed by the normal operation of the electrical device or electrical wiring to be measured can be suppressed. Therefore, the first patch antenna can stably receive the electromagnetic wave.

[0016] (4) The equipotential surface may be in a curved shape, and the first patch antenna may be disposed such that the conductive member follows the curved shape. Thereby, when the electromagnetic wave is received by the first patch antenna, the influence from the electric field formed by the normal operation of the electrical device or electrical wiring to be measured can be further suppressed. Therefore, the first patch antenna can more stably receive the electromagnetic wave.

[0017] [Details of Embodiments of the Present Disclosure] In the following embodiments, the same components are given the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0018] (First Embodiment) Referring to FIG. 2, the diamond sensor unit 100 according to the first embodiment of the present disclosure includes an excitation light generation unit 106, a fluorescence reflection filter 110, an optical waveguide 112, a sensor unit 120, an LPF 122, a light receiving unit 128, and a receiving unit 130. Outside the diamond sensor unit 100, an electromagnetic wave generation unit 140, a control unit 142, and a transmission unit 144 are arranged.

[0019] The control unit 142 includes a CPU (Central Processing Unit) and a storage unit (both not shown). The processes performed by the control unit 142 described below are realized by the CPU reading and executing a program stored in advance in the storage unit.

[0020] The excitation light generation unit 106 includes a light emitting element 102 and a condensing element 104. The light emitting element 102 generates excitation light for exciting the NV - center (hereinafter abbreviated as NV center) of diamond, which will be described later, under the control of the control unit 142. The control unit 142 supplies, for example, a voltage for causing the light emitting element 102 to emit light to the light emitting element 102 at a predetermined timing. The excitation light is green light (wavelength of about 490 to 560 nm). The excitation light is preferably laser light, and the light emitting element 102 is preferably a semiconductor laser (for example, the wavelength of the emitted light is 532 nm). The condensing element 104 condenses the excitation light output from the light emitting element 102. The condensing element 104 is for inputting as much of the excitation light diffused and output from the light emitting element 102 as possible to the light incident end of the optical waveguide 112 described later. The condensing element 104 preferably outputs parallel light condensed within a range smaller than the size of the light incident end of the optical waveguide 112 (for example, when an optical fiber is used, its core diameter (i.e., the diameter of the core)).

[0021] The fluorescence reflection filter 110 is an element for separating the excitation light incident from the condensing element 104 and the light (i.e., fluorescence) emitted from the diamond described later. For example, the fluorescence reflection filter 110 is a short-pass filter that passes light with a wavelength of a predetermined wavelength or less and cuts (i.e., reflects) light with a wavelength greater than the predetermined wavelength, or a band-pass filter that passes light with a wavelength within a predetermined wavelength range and cuts (i.e., reflects) light with a wavelength outside the predetermined wavelength range. Generally, since the excitation light has a shorter wavelength than the fluorescence, such a configuration is preferable. The fluorescence reflection filter 110 is preferably a dichroic mirror having such a function.

[0022] The optical waveguide 112 includes a medium for transmitting light and transmits light bidirectionally. That is, the excitation light incident on the first end disposed on the side of the excitation light generation unit 106 is transmitted to the second end disposed on the side of the sensor unit 120. Further, the emitted light (i.e., fluorescence) of the diamond element 116 incident on the second end is transmitted to the first end. The optical waveguide 112 is, for example, an optical fiber. In order to increase the energy density of the excitation light to be transmitted, it is preferable that the core diameter of the optical fiber is as small as possible. On the other hand, if the core diameter is too small, the efficiency of inputting the light diffused and emitted from the light source (i.e., the light emitting element) into the optical fiber decreases. Therefore, there is an appropriate core diameter. For example, the core diameter of the optical fiber is 1 μm or more and about 80 μm or less.

[0023] The sensor unit 120 includes a condenser element 114, a diamond element 116, and an electromagnetic wave irradiation unit 118. The diamond element 116 includes an NV center. The condenser element 114 is disposed in contact with the diamond element 116. The condenser element 114 converges the excitation light output from the optical waveguide 112 and irradiates the diamond element 116. The electromagnetic wave irradiation unit 118 irradiates the diamond element 116 with electromagnetic waves (for example, microwaves). The electromagnetic wave irradiation unit 118 is, for example, a coil formed including an electrical conductor. The source of the electromagnetic waves irradiated from the electromagnetic wave irradiation unit 118 to the diamond element 116 is the electromagnetic wave generation unit 140. That is, the electromagnetic waves output from the electromagnetic wave generation unit 140 are radiated into the air as electromagnetic waves EW by the transmission unit 144, received by the reception unit 130 (for example, an antenna), and transmitted to the electromagnetic wave irradiation unit 118.

[0024] The reception unit 130 is, for example, the patch antenna (that is, a microstrip antenna) shown in FIG. 3. This patch antenna includes substrates 280 and 284 and a connector 288 for outputting the received signal. The connector 288 is an SMA type coaxial connector and is connected to the electromagnetic wave irradiation unit 118 via a coaxial cable or the like. The substrates 280 and 284 are arranged with a predetermined interval H by spacers 286 provided at four corners. Both the substrates 280 and 284 are substrates of an electrically insulating member having a predetermined thickness d, and their planes are squares with a side length L. Among the two planes of the substrate 280, four conductive members 282 are arranged separately from each other on the surface not facing the substrate 284. Each conductive member 282 is square, its four sides are parallel to the four sides of the substrate 280, and the four conductive members 282 are rotationally symmetric four times with the center point of the substrate 280 as the center of rotation. On the entire surface of the surface of the substrate 284 facing the substrate 280, a conductive member 290 is arranged.

[0025] The four conductive members 282 are connected in parallel to the signal lines of the connector 288, and the conductive member 290 of the substrate 284 is connected to the shield (i.e., ground) of the connector 288. The conductive member 290 is the ground plane of the patch antenna. Thereby, the patch antenna has directivity in the direction perpendicular to the plane of the substrate 280. The microwave received by the receiving unit 130 is transmitted to the electromagnetic wave irradiating unit 118 via a transmission line (i.e., a coaxial cable) and irradiated onto the diamond element 116. When receiving a microwave with a frequency of about 2.87 GHz, the substrates 280 and 284 are made of, for example, a glass epoxy resin substrate (e.g., FR4) with L = 120 (mm) and t = 1 (mm), and are arranged at an interval of H = 5.2 (mm). Since the patch antenna can be formed in a planar shape, using the patch antenna for the receiving unit 130 increases the degree of freedom in design.

[0026] The transmitting unit 144 is, for example, a waveguide horn antenna shown in FIG. 4. The horn antenna includes an adapter portion 300, a horn portion 302, and a connector 304. The connector 304 is an SMA type coaxial connector and supplies the electromagnetic wave (i.e., microwave) supplied from the outside (i.e., the electromagnetic wave generating unit 140) to the adapter portion 300. The adapter portion 300 is a waveguide formed of a conductive member (e.g., an aluminum alloy), and the shape of the cross section (hereinafter referred to as the cut) perpendicular to the propagation direction of the electromagnetic wave is constant. The electromagnetic wave supplied to the adapter portion 300 is propagated to the horn portion 302. The horn portion 302 is formed of a conductive member (e.g., an aluminum alloy) and is formed in a bell shape in which the cut gradually widens in order to match with free space and suppress reflection. The horn antenna has directivity in the direction of its central axis 306. In the horn antenna shown in FIG. 4, the opening of the horn portion 302 is a rectangle with a predetermined width L1 and a predetermined height L2, and the total length of the adapter portion 300 and the horn portion 302 is a predetermined length L3. When radiating a microwave with a frequency of about 2.87 GHz, for example, those with L1 = 110 (mm), L2 = 87.9 (mm), and L3 = 254 (mm) can be used. By using the horn antenna for the transmitting unit 144, electromagnetic waves can be transmitted to the receiving unit 130 (i.e., the patch antenna) with good directivity.

[0027] Note that the shape of the horn part 302 only needs to be a conical shape with a gradually widening cut surface, and is not limited to the shape shown in FIG. 4 and is arbitrary. For example, the shape of the horn part 302 may be a conical shape, a pyramidal shape with the height L2 of the opening equal to the height of the adapter part 300, or a pyramidal shape with the height width L1 of the opening equal to the width of the adapter part 300. Further, the adapter part 300 and the horn part 302 may be integrally formed or may be detachably configured. For example, each of the adapter part 300 and the horn part 302 may have a flange at a portion where they are connected to each other, and the flanges may be detachably connected by screws or the like. Further, the electromagnetic wave outlet (i.e., the opening) of the horn part 302 needs to be arranged toward the receiving part 130 (i.e., such that the receiving part 130 is located on the extension line of the central axis 306 of the horn antenna). It is preferable that the closest part between the horn part 302 and the patch antenna is separated by 50 cm or more, more preferably 1 m or more, still more preferably 5 m or more, and even more preferably 10 m or more. If it is less than 50 cm, when the receiving part 130 is on the high voltage side of 33 kV or more (for example, high voltage equipment), it is not preferable because discharge is likely to occur between the high voltage side and the horn part 302. Further, if it is separated by 30 m or more, the power of the microwave radiated from the transmitting part 144 cannot reach the receiving part 130, which is not preferable.

[0028] The irradiation of the excitation light and electromagnetic waves to the diamond element 116 is controlled by the control unit 142, and is performed, for example, at the timing as shown in FIG. 5. That is, the control unit 142 controls the light emitting element 102 to output the excitation light for a predetermined time (for example, period t1) at a predetermined timing. The control unit 142 controls the electromagnetic wave generation unit 140 to output electromagnetic waves at a predetermined timing for a predetermined time (for example, period t2). The pulse sequence in the period t2 may be an appropriate one according to the diamond to be used (for example, the alignment state of a plurality of NV centers) and the observation signal (that is, the signal affected by the spin state of the NV center). Thereby, the electromagnetic wave is combined with the excitation light temporally and spatially and irradiated to the diamond element 116. The control unit 142 takes in the output signal of the light detection unit 126 to be input at a predetermined timing (for example, within the period t3) and stores it in the storage unit, as will be described later.

[0029] The NV center has a structure in which a carbon (C) atom in a diamond crystal is replaced by a nitrogen (N) atom and there is no carbon atom that should be adjacent thereto (that is, a vacancy (V)). The NV center transitions from the ground state to the excited state by green light having a wavelength of about 490 to 560 nm (for example, 532 nm laser light), emits red light having a wavelength of about 630 to 800 nm (for example, 637 nm fluorescence), and returns to the ground state. In the state where the NV center captures one electron (that is, NV - ), the magnetic quantum number m s forms a spin triplet state of -1, 0, +1. When a magnetic field exists, the energy levels of the states with m s =±1 are separated according to the magnetic field strength (that is, Zeeman separation). By irradiating the NV center with microwaves of about 2.87 GHz, the state with m s =0 is changed to m sAfter transitioning to the state of ±1 (i.e., electron spin resonance), green light is irradiated for excitation. As a result, when returning to the ground state, the transition includes a transition that does not emit light (i.e., fluorescence), so the intensity of the observed emitted light decreases. Therefore, a valley (i.e., a signal dip) is observed in the ESR (Electron Spin Resonance) spectrum. As described above, by the control unit 142 controlling the light-emitting element 102 and the electromagnetic wave generation unit 140, for example, a spectrum as shown in FIG. 6 is measured. The observed Δf depends on the magnetic field strength at the position of the diamond element 116.

[0030] Specific spectrum measurement is performed as follows. That is, the light (i.e., fluorescence) diffused and emitted from the diamond element 116 is collected by the condenser element 114 and made into parallel light, and is input to the second end of the optical waveguide 112. The light (i.e., fluorescence) input to the optical waveguide 112 is transmitted by the optical waveguide 112 and output from the first end of the optical waveguide 112. The light (i.e., fluorescence) output from the first end of the optical waveguide 112 is reflected by the fluorescence reflection filter 110, passes through the LPF 122, is collected by the condenser element 124, and is incident on the light detection unit 126. Thereby, light of a frequency corresponding to the magnetic field at the position where the diamond element 116 is arranged is detected by the light detection unit 126. The light detection unit 126 generates and outputs an electrical signal corresponding to the incident light. The light detection unit 126 is, for example, a photodiode. The output signal of the light detection unit 126 is acquired by the control unit 142.

[0031] The LPF 122 is a long-pass filter that passes light with a wavelength of a predetermined wavelength or longer and cuts (e.g., reflects) light with a wavelength smaller than the predetermined wavelength. The emitted light of the diamond element 116 is red light and passes through the LPF 122, but the excitation light has a shorter wavelength than that, so it does not pass through the LPF 122. Thereby, it is possible to suppress the excitation light emitted from the light-emitting element 102 from being detected by the light detection unit 126 and becoming noise, and to suppress a decrease in the detection sensitivity of the emitted light (i.e., fluorescence) of the diamond element 116.

[0032] As described above, the control unit 142 irradiates the diamond element 116 with the excitation light, sweeps the frequency of the electromagnetic wave within a predetermined range and irradiates the diamond element 116, and can acquire the light (i.e., fluorescence) emitted from the diamond element 116 as an electrical signal output from the light detection unit 126. From the observed Δf (i.e., a value depending on the magnetic field strength at the position of the diamond element 116), the magnetic field strength at the position of the diamond element 116 can be calculated. That is, the diamond sensor unit 100 functions as a magnetic sensor. Note that the diamond sensor unit 100 can be used not only as a sensor for detecting a magnetic field (i.e., a magnetic field), but also as a sensor for detecting physical quantities related to the magnetic field, such as magnetization, electric field, voltage, current, temperature, and pressure.

[0033] The electromagnetic wave irradiated to the diamond element 116 is propagated through the air (i.e., wirelessly) by the transmission unit 144 and the reception unit 130 and transmitted to the electromagnetic wave irradiation unit 118. Therefore, even if a high voltage and a large current are generated by discharge in high-voltage equipment or the like where the sensor unit 120 is disposed, the devices for transmitting the electromagnetic wave (i.e., the electromagnetic wave generation unit 140 and the control unit 142) are not damaged.

[0034] Also, if an optical fiber is used for the optical waveguide 112, since the diamond element 116, which is the main body of the sensor, and the condensing element 114 are formed of an electrical insulator, even if the second end of the sensor unit 120 and the optical waveguide 112 are installed in high-voltage equipment or the like, the occurrence of damage due to discharge or the like can be suppressed. Therefore, the diamond sensor unit 100 can safely measure a magnetic field or the like in a high-voltage environment. Further, the excitation light generation unit 106 and the light receiving unit 128 can be arranged far from the high-voltage environment via the optical waveguide 112, and the electromagnetic wave generation unit 140 and the transmission unit 144 can also be arranged far from the high-voltage environment. Therefore, the diamond sensor unit 100 enables remote measurement of a magnetic field or the like. The distance (i.e., the separation distance) between the transmission unit 144, the excitation light generation unit 106, the light receiving unit 128, and the sensor unit 120 is preferably 10 cm or more, more preferably 50 cm or more. The separation distance is further preferably 1 m or more, still more preferably 5 m or more, and even more preferably 10 m or more.

[0035] Also, since the sensor unit 120 includes the condensing element 114 arranged between the diamond element 116 and the optical waveguide 112, the loss of excitation light and emitted light can be reduced, and the detection accuracy can be improved. Further, a fluorescence reflection filter 110 for separating the excitation light and the emitted light is provided, and the transmission of the excitation light and the emitted light can be performed by one medium (for example, the optical waveguide 112). As a result, as will be described later, the number of components can be reduced and a simple configuration can be achieved compared to the case where two media for transmitting the excitation light and the emitted light are provided.

[0036] (Second Embodiment) In the first embodiment, one optical waveguide 112 was used to transmit light (i.e., excitation light and emission light) bidirectionally. However, in the second embodiment, optical waveguides for transmitting the excitation light and the emission light of the diamond element 116 are used. Referring to FIG. 7, a diamond sensor unit 200 according to the second embodiment of the present disclosure includes an excitation light generation unit 206, a first optical waveguide 212, a condensing element 208, a fluorescence reflection filter 210, a sensor unit 220, an LPF 222, a condensing element 224, a second optical waveguide 230, a light receiving unit 228, and a receiving unit 252. Outside the diamond sensor unit 200, an electromagnetic wave generation unit 140, a control unit 142, and a transmission unit 144 are arranged in the same manner as in the first embodiment.

[0037] The excitation light generation unit 206 includes a light emitting element 202 and a condensing element 204. The sensor unit 220 includes a condensing element 214, a diamond element 216, and an electromagnetic wave irradiation unit 218. The light receiving unit 228 includes a light detection unit 226. The light emitting element 202, the condensing element 204, the fluorescence reflection filter 210, the condensing element 214, the diamond element 216, the electromagnetic wave irradiation unit 218, the LPF 222, the light detection unit 226, and the receiving unit 252 respectively correspond to the light emitting element 102, the condensing element 104, the fluorescence reflection filter 110, the condensing element 114, the diamond element 116, the electromagnetic wave irradiation unit 118, the LPF 122, the light detection unit 126, and the receiving unit 130 shown in FIG. 2 and function in the same manner. Therefore, these will be briefly described.

[0038] The light emitting element 202, as in the first embodiment, generates excitation light for exciting the NV center of diamond under the control of the control unit 142. The control unit 142 supplies, for example, a voltage for causing the light emitting element 202 to emit light to the light emitting element 202 at a predetermined timing. The excitation light is green light. The excitation light is preferably laser light, and the light emitting element 202 is preferably a semiconductor laser. The condensing element 204 condenses the excitation light diffused and output from the light emitting element 202 and inputs it to the light incident end of the first optical waveguide 212.

[0039] The first optical waveguide 212 includes a medium for transmitting light. Different from the optical waveguide 112 shown in FIG. 2, the first optical waveguide 212 transmits the excitation light but does not transmit the emitted light of the diamond element 216. That is, the excitation light incident on the first end (i.e., the incident end) of the first optical waveguide 212 disposed on the excitation light generation unit 206 side is transmitted to and output from the second end (i.e., the output end) disposed on the sensor unit 220 side. The first optical waveguide 212 is, for example, an optical fiber. The excitation light diffused and output from the first optical waveguide 212 is condensed by the condenser element 208 and incident on the fluorescence reflection filter 210 as parallel light.

[0040] The fluorescence reflection filter 210 is an element for separating the excitation light incident from the condenser element 208 and the light (i.e., fluorescence) emitted from the diamond element 216. The fluorescence reflection filter 210 may be a dichroic mirror.

[0041] The condenser element 214 converges the excitation light input through the fluorescence reflection filter 210 and irradiates the diamond element 216. The condenser element 214 is disposed in contact with the diamond element 216. The diamond element 216 includes an NV center. The electromagnetic wave irradiation unit 218 irradiates the diamond element 216 with electromagnetic waves (e.g., microwaves). The electromagnetic wave irradiation unit 218 is, for example, a coil. The electromagnetic wave is generated by the electromagnetic wave generation unit 140, radiated into the air as the electromagnetic wave EW by the transmission unit 144, received by the reception unit 252 (e.g., the patch antenna shown in FIG. 3), and supplied to the electromagnetic wave irradiation unit 218. The irradiation of the excitation light and the electromagnetic wave to the diamond element 216 is controlled by the control unit 142, for example, at the timing as shown in FIG. 5. Thereby, as described above, red light (i.e., fluorescence) is emitted from the diamond element 216.

[0042] The light (i.e., red fluorescence) diffused and emitted from the diamond element 216 is collected by the light collecting element 214 to become parallel light and is input to the fluorescence reflection filter 210. The light (i.e., red fluorescence) input to the fluorescence reflection filter 210 is reflected by the fluorescence reflection filter 210 and enters the LPF 222. The emitted light of the diamond element 216 (i.e., red fluorescence) that has entered the LPF 222 passes through the LPF 222, is collected by the light collecting element 224, and enters the first end (i.e., the incident end) of the second optical waveguide 230. The LPF 222 suppresses the excitation light emitted from the light emitting element 202 from being detected by the light detection unit 226 and becoming noise, and thus suppresses a decrease in the detection sensitivity of the emitted light (i.e., fluorescence) of the diamond element 216.

[0043] The second optical waveguide 230 includes a medium for transmitting light. The second optical waveguide 230 transmits the light (i.e., the emitted light of the diamond element 216) incident from the light collecting element 224 to the first end (i.e., the incident end) to the second end (i.e., the output end) disposed on the light receiving unit 228 side and outputs it. The light output from the second optical waveguide 230 is detected by the light detection unit 226. The light detection unit 226 is, for example, a photodiode. The output signal of the light detection unit 226 is acquired by the control unit 142.

[0044] As described above, the control unit 142 irradiates the diamond element 216 with excitation light and irradiates the diamond element 216 by sweeping the frequency of the electromagnetic wave within a predetermined range, and can acquire the light (i.e., fluorescence) emitted from the diamond element 216 as an electrical signal output from the light detection unit 226, in the same manner as in the first embodiment. Therefore, the diamond sensor unit 200 functions as a magnetic sensor. The diamond sensor unit 200 can also be used as a sensor for detecting physical quantities related to a magnetic field, such as magnetization, electric field, voltage, current, temperature, and pressure, not limited to a magnetic field.

[0045] The electromagnetic wave irradiated to the diamond element 216 is propagated through the air (i.e., wirelessly) by the transmission unit 144 and the reception unit 252 and transmitted to the electromagnetic wave irradiation unit 218. Therefore, even if a high voltage and a large current are generated by discharge in high-voltage equipment or the like where the sensor unit 220 is arranged, the devices for transmitting electromagnetic waves (i.e., the electromagnetic wave generation unit 140 and the control unit 142) will not be damaged.

[0046] Also, if optical fibers are used for the two optical waveguides, since the diamond element 216 which is the main body of the sensor and the condensing element 214 are formed of electrical insulators, the occurrence of damage due to discharge or the like can be suppressed. Therefore, the diamond sensor unit 200 can safely measure a magnetic field or the like in a high-voltage environment. Further, the excitation light generation unit 206 and the light reception unit 228 can be arranged far from the high-voltage environment via the first optical waveguide 212 and the second waveguide 230, and the electromagnetic wave generation unit 140 and the transmission unit 144 can also be arranged far from the high-voltage environment. Therefore, the diamond sensor unit 200 enables measurement of a magnetic field or the like from a remote location. The distance (i.e., the separation distance) between the transmission unit 144, the excitation light generation unit 206 and the light reception unit 228 and the sensor unit 220 is preferably 10 cm or more, more preferably 50 cm or more. The separation distance is more preferably 1 m or more, still more preferably 5 m or more, and even more preferably 10 m or more.

[0047] Also, since the sensor unit 220 includes the condensing element 214 arranged between the diamond element 216 and the first optical waveguide 212 and the second waveguide 230, the loss of the excitation light and the emitted light can be reduced and the detection accuracy can be improved.

[0048] By using two optical waveguides (i.e., the first optical waveguide 212 and the second optical waveguide 230), the excitation light with different wavelengths and the emitted light of the diamond element 216 can be appropriately transmitted respectively. That is, by using an optical fiber with a core diameter corresponding to the wavelength, a condensing optical system suitable for each (i.e., the condensing element 204, the condensing element 208, the condensing element 214, and the condensing element 224) can be designed, the light transmission efficiency can be improved, and the measurement accuracy can be improved. When an optical fiber is used for the optical waveguide, it is preferable that the core diameter of the optical fiber (i.e., the second optical waveguide 230) for transmitting the emitted light of the diamond is larger than the core diameter of the optical fiber (i.e., the first optical waveguide 212) for transmitting the excitation light.

[0049] As described above, for the optical fiber used to transmit the excitation light, in order to increase the energy density of the excitation light, it is better that the core diameter is smaller. However, if the core diameter is too small, loss will occur when the light is input from the light source into the fiber. Therefore, there is an appropriate core diameter. The core diameter of the first optical waveguide 212 is preferably 1 μm or more and 100 μm or less. On the other hand, the larger the core diameter of the optical fiber for transmitting the emitted light of the diamond element 216, the better. However, if the core diameter is too large, the cost will be high. The core diameter of the second optical waveguide 230 is preferably 1 μm or more and 1 mm or less.

[0050] The sensor unit 120 and the receiving unit 130 in FIG. 2 are arranged in the vicinity of the detection target. If the detection target is a high-voltage electrical device, a transmission line, or the like, they form an electric field around them when energized, so the receiving performance of the receiving unit 130 is affected by this. The same applies to the sensor unit 220 and the receiving unit 252 in FIG. 5. To reduce the influence, it is preferable to pay attention to the arrangement of the receiving unit 130 with respect to the electric field, that is, the arrangement of the conductive members that function as the antennas of the receiving unit 130. Specifically, in the case of the patch antenna shown in FIG. 3, it is preferable to arrange the receiving unit 130 so that the conductive members 282 and 290 are parallel to the equipotential surface formed by electrical equipment, transmission lines, etc. Thereby, when the receiving unit 130 receives electromagnetic waves, the influence of the electric field formed by the normal operation of the detection target (that is, a high-voltage electrical device, a transmission line, or the like) can be suppressed. Therefore, the receiving unit 130 can stably receive the electromagnetic waves radiated from the transmitting unit 144.

[0051] If the equipotential surface at the location where the receiving unit 130 is arranged is planar, as described above, even if the substrates 280 and 284 of the receiving unit 130 are flat plates (for example, substrates of glass epoxy resin), the conductive members 282 and 290 can be arranged parallel to the equipotential surface. However, when the equipotential surface is curved, if the substrates 280 and 284 are rigid flat plates, the conductive members 282 and 290 cannot be arranged along the curved equipotential surface. Therefore, it is preferable to form the shapes of the conductive members 282 and 290, that is, the shapes of the substrates 280 and 284 that are their bases, into shapes curved along the equipotential surface. Incidentally, the equipotential surfaces of electrical equipment, transmission lines, etc. can be known in advance by simulation or the like according to the shapes of the conductive members that constitute them. If the conductive members deviate from the equipotential surface, electric field concentration occurs at the corners of the patch antenna or the like, which may lead to insulation breakdown or cause arc discharge when a rapid potential change such as lightning occurs, leading to possible equipment failure.

[0052] For example, referring to FIG. 8, when the sensor unit 120 is disposed on a high-voltage transmission line including the central conductor 310 and the outer conductor 312, the receiving unit 130 is disposed, for example, in the vicinity of the central conductor 310. The central conductor 310 is formed of a conductive member, and its periphery is covered with an insulating member. The outer conductor 312 is formed of a conductive member and is grounded (i.e., at ground potential). A gas such as SF6 or CO2 may be filled between the central conductor 310 and the outer conductor 312.

[0053] The equipotential surface formed by energizing the central conductor 310 is a cylindrical surface having the same central axis as the central conductor 310. Therefore, it is preferable that the conductive member 282 disposed on the substrate 280 has a shape along the cylindrical surface that is the equipotential surface. Referring to FIG. 9 showing a cross-section of the transmission line (the substrates 280 and 284 are not shown for convenience), the cross-section of the equipotential surface (i.e., the equipotential line) is concentric with the point O which is the center of the central conductor 310. Therefore, it is preferable that the cross-sectional shape of the conductive member 282 is an arc having a radius r1 and centered on the point O. Similarly, with respect to the conductive member 290 formed on the substrate 284, it is preferable that it has a shape along the cylindrical surface that is the equipotential surface. That is, it is preferable that the cross-section of the conductive member 290 is an arc having a radius r2 and centered on the point O.

[0054] The substrates 280 and 284 on which the conductive members 282 and 290 are respectively disposed are preferably formed in a plate shape curved along the side surface of the central conductor 310 using, for example, a glass epoxy resin or the like. When the receiving unit 130 is formed and disposed on the central conductor 310 in this way, as shown in FIGS. 8 and 9, a transmitting unit 144 (for example, a horn antenna) is disposed in an opening 314 provided on the side surface of the outer conductor 312 so that the radial direction is toward the center of the central conductor 310 (i.e., the point O), and an electromagnetic wave EW (for example, a microwave) may be radiated toward the receiving unit 130.

[0055] As a result, when the receiving unit 130 receives an electromagnetic wave, it is possible to suppress the influence of the electric field formed by the normal operation (i.e., power supply) of the transmission line to be detected. Therefore, the receiving unit 130 can stably receive the electromagnetic wave radiated from the transmitting unit 144.

[0056] Further, the conductive members 282 and 290 may be formed as thin plates (or thin films), and the substrates 280 and 284 on which the conductive members 282 and 290 are respectively arranged may be formed using a plastic member. For example, when the substrates 280 and 284 are formed of a shape memory resin (e.g., shape memory polymer), if the equipotential surfaces formed by electrical equipment or electrical wiring are separated, the substrates 280 and 284 can be heated and deformed into a shape along the equipotential surfaces. As a result, the conductive members 282 and 290 can be deformed into a shape along the equipotential surfaces and arranged along the equipotential surfaces.

[0057] In the second embodiment, the fluorescence reflection filter 210 is used to separate the excitation light and the emitted light of the diamond element 216, but the present invention is not limited to this. The excitation light and the emitted light of the diamond element 216 may be separated using an LPF. Specifically, the optical path for transmitting the excitation light shown in FIG. 7 and the optical path for transmitting the emitted light may be interchanged, and a configuration may be adopted in which an LPF is used instead of the fluorescence reflection filter 210.

[0058] In the above description, the case where excitation light is incident on one surface of a diamond element including an NV center and the emitted light from the same surface is measured has been described, but it is not limited thereto. When the diamond element including the NV center has a plurality of flat surfaces, the surface on which the excitation light is irradiated and the surface on which the emitted light is measured may be different. A flat surface means a single flat plane having an area equal to or larger than a predetermined value. Here, the flat surface of the diamond element including the NV center means a single flat plane having an area larger than a circle with a diameter of about 200 μm. For example, when the diamond element is formed in a rectangular parallelepiped shape, among the two surfaces forming a 90-degree angle, excitation light is incident on the first flat surface, and the emitted light from the second flat surface is collected and detected. Also, a third flat surface parallel to the first flat surface may be used as the surface for collecting the emitted light to be detected. The diamond element only needs to have at least two flat surfaces, and is not limited to a hexahedron, and the shape of the diamond element is arbitrary.

[0059] In the above description, the case where a diamond element having an NV center is used in the diamond sensor unit has been described, but it is not limited thereto. Any diamond element having a color center with an electron spin may be used. A color center with an electron spin is a center that forms a spin triplet state and emits light when excited, and the NV center is a representative example. In addition, it is known that there are also color centers with electron spins in silicon-vacancy centers (i.e., Si-V centers), germanium-vacancy centers (i.e., Ge-V centers), and tin-vacancy centers (i.e., Sn-V centers). Therefore, a diamond element including these may be used instead of the diamond element including the NV center to constitute the diamond sensor unit.

[0060] Note that, depending on the level of the color center, the wavelengths of the excitation light and the emitted light (i.e., fluorescence), as well as the frequency of the electromagnetic wave for resonance excitation, are different. Among them, the NV center is easy to handle in terms of the wavelength of light and the frequency of microwaves, and is preferable. In the case of Si-V centers, Ge-V centers, and Sn-V centers, millimeter waves (e.g., 30 GHz to 300 GHz) or sub-millimeter waves (e.g., 300 GHz to 3 THz) with a frequency higher than that of microwaves (e.g., 1 GHz to 30 GHz) are used for the irradiated electromagnetic waves. For example, for Si-V centers, millimeter waves of about 48 GHz can be used, and for Sn-V centers, sub-millimeter waves of about 850 GHz can be used.

[0061] In the above, the case of using horn antennas (see FIG. 4) in the transmission units 144 and 252 has been described, but it is not limited thereto. Instead of horn antennas, patch antennas (e.g., microstrip antennas) may be used. By using patch antennas, millimeter waves and sub-millimeter waves can be transmitted, and sensors using Si-V centers, Ge-V centers, Sn-V centers, etc. can be realized.

[0062] The optical waveguide preferably has a coaxial structure of two or more layers having a core portion through which light passes and a portion of a material having a refractive index different from that of the core portion formed around the core. The core portion does not have to be in a form densely filled with a medium for transmitting light. Since the space itself can transmit light, the core portion may be a cavity. The optical waveguide is preferably an optical fiber having a core diameter of 1 μm or more and 80 μm or less. This is because if an optical fiber is used, laser light can be relatively easily guided to a desired position, and divergence at the output end of the optical fiber can also be suppressed.

[0063] The light condensing element may be formed of a substance having the function of condensing light. For example, it may be a lens formed of a silicon oxide-based material (for example, glass, which may contain additives other than silicon oxide), or a substance having a diffraction function. The light condensing element is preferably a lens that transmits light and utilizes the refraction phenomenon. A spherical lens, a hemispherical lens, a Fresnel lens, etc. are preferable. In particular, in terms of the relationship between the refractive index and the spherical shape, a lens in which the focal point of parallel light is located on the spherical surface is more preferable. The use of such a lens makes it very convenient to adjust the optical focal point and optical axis, and the light amount can be utilized to the maximum extent.

[0064] When the sensor unit is arranged in a high-voltage environment, the optical waveguide (for example, an optical fiber) for transmitting the excitation light and the emitted light of the diamond is preferably arranged through an insulator. Thereby, the excitation light generation part and the light receiving part can be insulated from the high voltage, and the devices used in the excitation light generation part and the light receiving part can be protected.

[0065] The electromagnetic wave irradiation part is not limited to a coil shape, and may be a linear electrical wiring as described later. In that case, the diamond element may be arranged on the surface or at the end of a transmission path (for example, a conductive member) that transmits electromagnetic waves (for example, microwaves or millimeter waves, etc.). Thereby, the NV center of the diamond can be accurately irradiated with electromagnetic waves.

[0066] When using the above-described diamond sensor unit to detect the time change of a fluctuating magnetic field or the like for alternating current power, after the NV center of the diamond element is excited, it is preferably quickly returned to the original state (that is, the state before excitation) from the state of emitting light. For this purpose, it is preferable that the spin coherence time T2 of the diamond element is short. For example, the spin coherence time T2 of the diamond element is preferably less than 50 μsec. Note that the detection sensitivity is (T2) -1 / 2Since it is proportional to T2, the smaller T2 is, the lower the detection sensitivity becomes. Therefore, when detecting a rapid change in magnetic field fluctuations, for example, when detecting pulsed magnetic field fluctuations, it is conceivable to sacrifice the detection sensitivity and make the spin coherence time T2 of the diamond element as short as possible.

[0067] In order to shorten the spin coherence time, it is preferable that the diamond element contains impurities. Considering that the detection sensitivity decreases as T2 becomes smaller, for example, it is preferable that the total hydrogen concentration in the diamond is greater than 0 ppm and less than or equal to 1 ppm. Also, the NVH - concentration, CH concentration, and CH2 concentration in the diamond are all preferably greater than 0 ppm and less than or equal to 1 ppm. Here, the concentration (in ppm units) represents the ratio of the number of atoms.

[0068] Note that in the first embodiment, the diamond sensor unit 100 may include the transmission unit 144. Similarly, in the second embodiment, the diamond sensor unit 200 may include the transmission unit 144.

Examples

[0069] Hereinafter, the effectiveness of the present disclosure will be shown by examples. FIG. 10 shows an example of the configuration shown in FIG. 7. In FIG. 10, those corresponding to the components shown in FIG. 7 are given the same reference numerals as in FIG. 7.

[0070] For the first optical waveguide 212 and the second optical waveguide 230, step-index multimode optical fibers were used. The first optical waveguide 212 has a core diameter of 50 μm and a numerical aperture (NA), i.e., the aperture number, of 0.2. The second optical waveguide 230 has a core diameter of 400 μm and an NA of 0.5. For the diamond element 216, a rectangular parallelepiped diamond of 3 mm × 3 mm × 0.3 mm was used. For the condensing element 214, a spherical lens with a diameter of 2 mm was used, and the condensing element 214 was fixed in contact with the surface of the diamond element 216 (i.e., the 3 mm × 3 mm flat surface). In the optical system for transmitting the excitation light, in addition to the condensing element 208 and the fluorescence reflection filter 210, a triangular prism 250 was arranged to form a collimating optical system. Thereby, the excitation light was adjusted to be incident on the center of the condensing element 214.

[0071] For the electromagnetic wave irradiation unit 218, the coplanar line shown in FIG. 11 was used. The copper foil 272 formed on the surface of a glass epoxy substrate 270 with a side length of about 2 cm was notched in a U shape, and the electromagnetic wave irradiation unit 218, which is the main wiring with a width of 1 mm, was formed in the center. The diamond element 216 was fixed with silver paste to the first end portion of the electromagnetic wave irradiation unit 218 facing the copper foil 272 (i.e., the region indicated by the dashed ellipse in FIG. 11). Thereby, the NV center of the diamond element 216 can be accurately irradiated with microwaves. The second end portion of the electromagnetic wave irradiation unit 218 where the diamond element 216 is not arranged was connected to the connector 254 in FIG. 10.

[0072] The microwave was generated by a remotely installed microwave generator, transmitted through the air, and received by the receiving unit 252 (see Fig. 10). The transmitting unit 144 that radiates microwaves toward the receiving unit 252 used the horn antenna shown in Fig. 4. The dimensions were L1 = 110 (mm), L2 = 87.9 (mm), and L3 = 254 (mm), and the gain was 10 dB. The receiving unit 252 used the patch antenna shown in Fig. 3 (frequency 2.873 GHz, maximum gain of approximately 10 dBi). The substrates 280 and 284 were glass epoxy substrates (L = 120 (mm), t = 1 (mm)), and were arranged at an interval of H = 5.2 (mm). The microwave received by the receiving unit 252 was transmitted to the connector 254 via a transmission line (i.e., a coaxial cable), and the diamond element 216 was irradiated from the electromagnetic wave irradiation unit 218.

[0073] For the optical detection unit 226, a PIN-AMP (i.e., a photodiode IC having a linear current amplification circuit) was used. The PIN-AMP used had a sensitivity wavelength range of 300 to 1000 nm for the photodiode, a maximum sensitivity wavelength of 650 nm, and amplified the photocurrent generated by the photodiode 1300 times for output.

[0074] The condensing element 214, diamond element 216, and electromagnetic wave irradiation unit 218 that constitute the sensor unit were arranged near the electrical wiring 260, and an alternating current (50 Hz or 60 Hz, 30 A) was passed through the electrical wiring 260, and the resulting fluctuating magnetic field was used as the detection target. The maximum value of the magnetic field formed in the sensor unit by the alternating current was approximately 0.3 μT. The power of the microwave radiated from the horn antenna was made constant (30 dBm (= 1 W)), and the distance D between the sensor unit and the horn antenna that radiates the microwave was changed and measured. The results are shown in Figs. 12A to 12C and Fig. 13. In any case, both the sensor unit and the receiving unit were arranged at the same distance D from the horn part.

[0075] Figures 12A to 12C show the signals detected by the PIN-AMP with an alternating current (30 A) of 50 Hz flowing through the electrical wiring 260. Figures 12A to 12C are the measurement results at D = 2.8 (m), D = 4 (m), and D = 5 (m), respectively. In all cases, the vertical axis is 10.0 mV per division and the horizontal axis is 5 ms per division. Figure 13 shows the signal detected by the PIN-AMP with an alternating current (30 A) of 60 Hz flowing through the electrical wiring 260, with D = 10 (m). The vertical axis is 10.0 mV per division and the horizontal axis is 4 ms per division.

[0076] As can be seen from FIGS. 12A to 12C and FIG. 13, as the distance D at which microwaves are radiated increases, the detected signal decreases. However, even when relatively weak microwaves of about 1 W are radiated from a position about 10 m away from the sensor unit, the magnetic field changes formed by the alternating current could be sufficiently detected. The detection signals shown in FIGS. 12A to 12C change at an alternating frequency of 50 Hz. The detection signal shown in FIG. 13 changes at an alternating frequency of 60 Hz. Although microwaves attenuate according to the distance, considering the detection limit (i.e., the lower limit value of power) and the radiation distance of the optical detection unit employed, the microwave power to be radiated, the gain of the radiation antenna, the gain of the reception antenna, etc. may be adjusted. When the receiving unit was placed in a high voltage environment of 10 kV at a distance D of 5 cm, discharge occurred at the horn antenna and the corners of the receiving unit, making measurement impossible. When the distance D was set to 30 m, the microwave power did not reach, and the change in the signal corresponding to the change in magnetism (i.e., the change in the magnetic field formed by the alternating current flowing through the electrical wiring 260) could not be measured. When the distances D were 50 cm and 1 m, the respective signal intensities became 5 times and 4 times the signal intensity in FIG. 12A. Here, the signal intensity means the difference between the maximum value and the minimum value obtained by averaging the noise. The signal intensity in FIG. 12A is the difference between the maximum value and the minimum value obtained by averaging the noise with respect to the data in FIG. 12A. As described above, when the distance D was 30 m, the microwave power did not reach and the signal could not be detected, so it is preferable that the distance D is smaller. However, since the signal intensity does not depend only on the microwave power, if the distance D is small to a certain extent, the signal intensity becomes a sufficient value and has a saturation tendency. Therefore, as the diamond sensor unit, it was confirmed that the measurement is possible and good if the distance between the horn antenna (specifically, the horn part) and the sensor unit (specifically, the receiving part) is 50 cm or more and 10 m or less.

[0077] In the above, a coplanar line was formed on a substrate with a side length of about 2 cm, but a rectangular substrate with a side length of about 5 cm or less may also be used.

[0078] The present disclosure has been described by explaining the embodiments. However, the above-described embodiments are examples, and the present disclosure is not limited to only the above-described embodiments. The scope of the present disclosure is indicated by each claim in the claims, and includes all modifications within the meaning and scope equivalent to the language described therein.

Explanation of Reference Numerals

[0079] 100, 200 Diamond Sensor Unit 102, 202 Light Emitting Element 104, 114, 124, 204, 208, 214, 224 Condensing Element 106, 206 Excitation Light Generation Unit 110, 210 Fluorescence Reflection Filter 112 Optical Waveguide 116, 216 Diamond Element 118, 218 Electromagnetic Wave Irradiation Unit 120, 220 Sensor Unit 122, 222, 908 LPF 126, 226 Light Detection Unit 128, 228 Light Receiving Unit 130, 252 Receiving Unit 140 Electromagnetic Wave Generation Unit 142 Control Unit 144 Transmission Unit 212 First Optical Waveguide 230 Second Optical Waveguide 250 Triangular Prism 254, 288, 304 Connector 260 Electrical Wiring 270 Glass Epoxy Substrate 272 Copper Foil 280, 284, 912, 914, 916 Substrate 282, 290 Conductive Member 286 Spacer 300 Adapter Unit 302 Horn Unit 306 Central Axis 310 Central Conductor 312 External Conductor 314 Opening 900 LED 902 SPF 904 Diamond 906 Lens 910 Photodiode d Thickness EW Electromagnetic Wave H Interval L, L3 Length L1 Width L2 Height

Claims

1. A diamond having a color center with an electron spin, an excitation light irradiation unit that irradiates the diamond with excitation light, a first patch antenna that receives electromagnetic waves, an electromagnetic wave irradiation unit that irradiates the diamond with the electromagnetic waves received by the first patch antenna, a detection unit that detects the radiation light emitted from the color center of the diamond after the excitation light and the electromagnetic waves are irradiated on the diamond, and an optical waveguide that transmits the excitation light and the radiation light, a diamond sensor unit.

2. further including a horn antenna or a second patch antenna that transmits the electromagnetic waves received by the first patch antenna, wherein the horn antenna transmits microwaves as the electromagnetic waves, and the second patch antenna transmits microwaves, millimeter waves, or sub-millimeter waves as the electromagnetic waves, the diamond sensor unit according to claim 1.

3. The first patch antenna includes a plate-shaped conductive member that receives the electromagnetic waves and is disposed on an electrical device or electrical wiring to be detected, and the first patch antenna is disposed such that the conductive member is parallel to the equipotential surface formed by the detection target, the diamond sensor unit according to claim 1 or claim 2.

4. The equipotential surface has a curved shape, and the first patch antenna is disposed such that the conductive member follows the curved shape, the diamond sensor unit according to claim 3.

Images