Measuring device and measuring method

Abstract

To suppress a noise component due to irradiation light to enhance measurement accuracy.SOLUTION: A light receiving device 13 receives fluorescence emitted from a magnetic resonance member 1 in response to excitation light, and generates a fluorescence sensor signal corresponding to the intensity of the fluorescence. A CMR calculation unit 25 performs common mode rejection on the fluorescence sensor signal based on a reference light sensor signal of reference light obtained by branching the excitation light, to generate a CMR signal. An analog-to-digital converter 26 digitizes the CMR signal, and an analog-to-digital converter 27 digitizes the reference light sensor signal. An arithmetic processing device 31 divides the digitized CMR signal by the digitized reference light sensor signal to generate a detection signal, derives a measurement value of a field under measurement on the basis of the detection signal, and performs digital filter processing for noise removal on the digitized CMR signal or detection signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a measurement device and a measurement method. [Background technology]

[0002] A certain magnetic field measuring device performs magnetic measurements using optically detected magnetic resonance (ODMR) that utilizes the electron spin resonance of a sensing material such as a diamond structure having nitrogen and lattice defects (NV center). In ODMR, a static magnetic field is applied to a magnetic resonance material such as a diamond having an NV center in addition to the magnetic field to be measured, and laser light (excitation light for initialization and measurement) and microwaves are applied in a predetermined sequence, and the amount of fluorescent light emitted from the magnetic resonance material is detected, and the magnetic flux density of the magnetic field to be measured is derived based on the amount of light.

[0003] For example, in the Ramsey pulse sequence, (a) excitation light is applied to the NV center, (b) a first π / 2 pulse of microwaves is applied to the NV center, (c) a second π / 2 pulse of microwaves is applied to the NV center at a predetermined time interval tt from the first π / 2 pulse, (d) excitation light is applied to the NV center to measure the amount of light emitted by the NV center, and (e) the magnetic flux density is derived based on the measured amount of light emitted. Also, in the spin echo pulse sequence, (a) excitation light is applied to the NV center, (b) a first π / 2 pulse of microwaves is applied to the NV center at a phase of 0 degrees of the measured magnetic field, (c) a π pulse of microwaves is applied to the NV center at a phase of 180 degrees of the measured magnetic field, (d) a second π / 2 pulse of microwaves is applied to the NV center at a phase of 360 degrees of the measured magnetic field, (e) excitation light is applied to the NV center to measure the amount of light emitted by the NV center, and (f) the magnetic flux density is derived based on the measured amount of light emitted.

[0004] One sensor device measures a magnetic field by nuclear magnetic resonance using a diamond sensor containing the above-mentioned NV center (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-138772 A Summary of the Invention [Problem to be solved by the invention]

[0006] In optical detection magnetic resonance that utilizes the electron spin resonance of the sensing component, the detection signal obtained from fluorescence is weak and is therefore easily affected by noise. In particular, the measurement accuracy is reduced due to noise in the irradiated light (laser light).

[0007] An object of the present invention is to provide a measuring device and a measuring method that suppresses noise components caused by irradiated light and improves measurement accuracy. [Means for solving the problem]

[0008] The measuring device according to the present invention comprises a magnetic resonance member whose electron spin quantum state changes in response to a measured field and which is capable of electron spin quantum manipulation using microwaves; a high-frequency magnetic field generator which performs electron spin quantum manipulation of the magnetic resonance member using microwaves; a light emitting device which emits excitation light to be irradiated to the magnetic resonance member; a fluorescence receiving device which receives fluorescence emitted by the magnetic resonance member in response to the excitation light and generates a fluorescence sensor signal corresponding to the intensity of the fluorescence; a CMR calculation unit which performs common mode rejection on the fluorescence sensor signal based on a reference light sensor signal which is generated by receiving reference light obtained by branching the excitation light and generates a CMR signal based on the common mode rejection; a first analog-to-digital converter which digitizes the CMR signal; a second analog-to-digital converter which digitizes the reference light sensor signal which is generated by receiving reference light obtained by branching the excitation light; and a calculation processing device which divides the digitized CMR signal by the digitized reference light sensor signal to generate a detection signal and derives a measurement value of the measured field based on the detection signal. The processor then performs digital filtering for noise removal on the digitized CMR signal or the detection signal.

[0009] The measurement method of the present invention (a) performs electron spin quantum manipulation of a magnetic resonance component whose electron spin quantum state changes in response to a measured field and whose electron spin quantum manipulation is possible with microwaves in accordance with a predetermined measurement sequence, and emits excitation light to be irradiated onto the magnetic resonance component, (b) receives fluorescence emitted by the magnetic resonance component in response to the excitation light, and generates a fluorescent sensor signal corresponding to the intensity of the fluorescent light, (c) performs common mode rejection of the fluorescent sensor signal based on a reference optical sensor signal generated by receiving reference light obtained by branching the excitation light, and generates a CMR signal based on the common mode rejection, (d) digitizes the CMR signal, (e) digitizes the reference optical sensor signal generated by receiving reference light obtained by branching the excitation light, and (f) divides the digitized CMR signal by the digitized reference optical sensor signal to generate a detection signal, and derives a measurement value of the measured field based on the detection signal. Then, digital filtering is performed on the digitized CMR signal or the detection signal to remove noise. Effect of the Invention

[0010] According to the present invention, a measurement device and a measurement method are obtained that suppress noise components caused by irradiated light and increase measurement accuracy. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing a configuration of a measurement device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of a measurement sequence. [Diagram 3] FIG. 3 is a diagram illustrating the reference optical sensor signals ref1(t) and ref2(t), the fluorescent sensor signal PL(t), the CMR signal CMR_SIG(t), and the detection signal SD(t). [Figure 4] FIG. 4 is a diagram illustrating an example of frequency characteristics of a window function. [Diagram 5]FIG. 5 is a flowchart illustrating the operation of the measurement device according to the embodiment shown in FIG. 1 (that is, the measurement method). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] 1 is a block diagram showing the configuration of a measurement device according to an embodiment of the present invention. The measurement device shown in FIG. 1 includes a sensor unit 10, a high-frequency power supply 11, a light emitting device 12, and a light receiving device 13.

[0014] The sensor unit 10 detects a measured field (e.g., a magnetic field such as the strength and direction of the magnetic field) at a predetermined position (e.g., on or above the surface of an object to be inspected). The measured field may be an AC field of a single frequency, an AC field of a predetermined period having multiple frequency components, or a DC field.

[0015] In this embodiment, the sensor section 10 includes a magnetic resonance member 1, a high-frequency magnetic field generator 2, and a magnet 3, and detects the measured field by ODMR.

[0016] The magnetic resonance member 1 has a crystal structure, and is a member in which the electron spin quantum state changes in response to the measured field (magnetic field in this case), and in which the electron spin quantum operation (based on Rabi oscillation) is possible with microwaves having a frequency according to the arrangement direction of defects and impurities in the crystal lattice. In other words, the magnetic resonance member 1 is placed at the position where the magnetic field is measured.

[0017] In this embodiment, the magnetic resonance component 1 is a light-detecting magnetic resonance component having a plurality (i.e., an ensemble) of specific color centers. The specific color centers have energy levels that can be Zeeman split, and can take a plurality of orientations in which the energy level shift widths during Zeeman splitting are different from one another.

[0018] Here, the magnetic resonance member 1 is a member such as diamond that includes multiple NV (Nitrogen Vacancy) centers as a single type of specific color center. In the case of the NV center, the ground state is a triplet state of ms=0, +1, -1, and the ms=+1 level and the ms=-1 level are Zeeman split. When the NV center transitions from the excited state of the ms=+1 and ms=-1 levels to the ground state, a certain proportion of them emit fluorescence, and the remaining proportion of the NV centers transition from the excited state (ms=+1 or ms=-1) to the ground state (ms=0) without radiation.

[0019] The color center included in the magnetic resonance member 1 may be a color center other than the NV center.

[0020] The high-frequency magnetic field generator 2 applies microwaves to the magnetic resonance member 1 to perform electron spin quantum manipulation of the magnetic resonance member 1. For example, the high-frequency magnetic field generator 2 is a plate-shaped coil, and includes a substantially circular coil portion that emits microwaves, and terminal portions that extend from both ends of the coil portion and are fixed to a substrate. The high-frequency power source 11 generates the microwave current and conducts it to the high-frequency magnetic field generator 2. The coil portion conducts two parallel currents at a predetermined interval at both end surface portions of the coil portion so as to sandwich the magnetic resonance member 1, and emits the above-mentioned microwaves. Here, the coil portion is a plate-shaped coil, but due to the skin effect, the microwave current flows through the end surface portions of the coil portion, so that two currents are formed.

[0021] In the case of NV centers, color centers are formed in diamond crystals by defects (vacancies) (V) and nitrogen (N) as impurities, and there are four possible positions of adjacent nitrogen (N) relative to the defects (vacancies) (V) in the diamond crystal (i.e., the arrangement direction of pairs of vacancies and nitrogen), and the sublevels (i.e., the energy levels from the ground level) after Zeeman splitting corresponding to each of these arrangement directions are different from each other. Therefore, in the characteristics of the fluorescence intensity after Zeeman splitting by the static magnetic field against the microwave frequency, four different dip frequency pairs (fi+, fi-) appear corresponding to each direction i (i=1,2,3,4). Here, the frequency (wavelength) of the microwave described above is set corresponding to one of the dip frequencies among these four dip frequency pairs.

[0022] Moreover, the magnet 3 applies a static magnetic field (DC magnetic field) to the magnetic resonance member 1, and Zeeman-splits the energy levels of a plurality of specific color centers (here, a plurality of NV centers) in the magnetic resonance member 1. Here, the magnet 3 is a ring-shaped permanent magnet, such as a ferrite magnet, an alnico magnet, or a samarium-cobalt magnet.

[0023] In this embodiment, the direction of application of the static magnetic field is the same as the direction of application of the magnetic field to be measured, and application of the static magnetic field enhances the change in fluorescence intensity at the dip frequency, thereby increasing sensitivity.

[0024] Furthermore, in this embodiment, the magnetic resonance member 1 includes a plurality of color centers (here, NV centers) capable of quantum manipulation of electron spins by the above-mentioned microwaves, and the magnet 3 applies a substantially uniform static magnetic field to a predetermined region (excitation light irradiation region) of the magnetic resonance member 1. For example, the static magnetic field is applied so that the difference or ratio between the maximum and minimum values ​​of the intensity of the static magnetic field in the predetermined region is equal to or less than a predetermined value.

[0025] Furthermore, in the magnetic resonance member 1, the crystals of the magnetic resonance member 1 are formed and the orientation of the magnetic resonance member 1 is set so that the arrangement direction of the above-mentioned defects and impurities approximately coincides with the direction of the above-mentioned static magnetic field (and the direction of the applied magnetic field).

[0026] Furthermore, in this embodiment, an optical system is provided from the light emitting device 12 to the magnetic resonance component 1 in order to irradiate excitation light to the magnetic resonance component 1, and an optical system is provided from the magnetic resonance component 1 to the light receiving device 13 in order to detect fluorescence from the magnetic resonance component 1.

[0027] The light emitting device 12 includes a laser diode or the like as a light source, which emits laser light of a predetermined wavelength as excitation light to be irradiated onto the magnetic resonance member 1. The light receiving device 13 includes a photodiode, a phototransistor, or the like as a light receiving element, receives fluorescence emitted by the magnetic resonance member 1 in response to the excitation light, and generates a fluorescence sensor signal PL corresponding to the intensity of the fluorescence. This fluorescence is focused toward the light receiving device 13 by an optical system such as a compound parabolic concentrator (CPC).

[0028] Here, the measurement principle will be explained.

[0029] The intensity I of the above mentioned excitation light is expressed as the following equation: laser and the intensity of the noise component I noise The noise component is generated due to fluctuations in the power supply voltage of the light emitting device 12 or fluctuations in the amount of light emitted by the light source, and has a frequency in the range of, for example, about kHz to about 100 kHz.

[0030] I=I laser +I noise

[0031] Furthermore, the level of the fluorescent sensor signal PL is basically proportional to the intensity I of the excitation light. However, due to the change in the electron spin quantum state caused by the measured field, the fluorescent intensity is small at the start of the excitation light irradiation during measurement, and then the fluorescent intensity gradually increases until the effect of the change in the electron spin quantum state caused by the measured field disappears. Therefore, the level fluctuation α of the fluorescent sensor signal PL caused by the change in the electron spin quantum state caused by the measured field cont A detection signal SD proportional to (t) is derived as a signal indicative of the measured field. The fluorescent sensor signal PL is expressed by the following equation:

[0032] PL(t) = α(t) × I = (α init +α cont (t)) × I = (α init +α cont (t))×(I laser +I noise )

[0033] Here, α init is a coefficient indicating the part proportional to the intensity I of the excitation light (the part that is not affected by the change in the electron spin quantum state due to the measured field).

[0034] On the other hand, the level ref of the reference light sensor signal of the reference light branched off from the excitation light is proportional to the intensity I of the excitation light and is therefore expressed by the following equation.

[0035] ref = ref1 = ref2 = β × I = β × (I laser +I noise )

[0036] Here, β is a constant. Note that ref1 and ref2 will be described later.

[0037] Here, common mode rejection is performed on PL(t) to generate a CMR signal. The CMR signal CMR_SIG(t) is expressed by the following equation. This means that α init About I noise The effect of is eliminated.

[0038] CMR_SIG(t)=PL(t)-α init / β×ref(t)=α cont (t) × (I laser +I noise )

[0039] The detection signal SD(t) is derived as follows: cont I about (t) noise The effect of is eliminated.

[0040] SD(t) = α cont (t) / β=CMR_SIG(t) / ref(t)

[0041] Since the peak value (the value at t = 0) and time integral value of the detection signal SD(t) are correlated with the strength of the measured field, the correspondence between the peak value and time integral value of the detection signal SD(t) and the strength of the measured field is determined in advance by experiments, etc., and the strength of the measured field is derived from the peak value and time integral value of the detection signal SD(t) using a formula or table that shows the correspondence.

[0042] Based on this measurement principle, the following configuration is provided.

[0043] 1 further includes optical splitters 21 and 22 as optical elements on the optical path of the excitation light from the light emitting device 12 to the magnetic resonance member 1. The optical splitters 21 and 22 each split a part of the excitation light from the excitation light and emit the split light in a different direction as a reference light. For example, the optical splitters 21 and 22 are polarization-independent beam splitters.

[0044] The measurement device shown in FIG. 1 also includes light receiving devices 23 and 24 that receive reference light and generate reference light sensor signals ref1 and ref2 (the above-mentioned ref) that correspond to the intensities of the reference light.

[0045] In this embodiment, two reference lights are generated separately from the excitation light, and two reference optical sensor signals ref1 and ref2 are generated. The reference optical sensor signal ref1 is used for common mode rejection, which will be described later, and the reference optical sensor signal ref2 is digitized and used to generate a detection signal SD.

[0046] 1 further includes a CMR calculation unit 25 as an analog calculation circuit. The CMR calculation unit 25 performs common mode rejection on the fluorescence sensor signal PL based on the reference optical sensor signal ref1, and generates a CMR signal CMR_SIG based on the common mode rejection. Specifically, the CMR calculation unit 25 includes a coefficient unit 25a and a differential amplifier 25b. The coefficient unit 25a calculates a CMR signal CMR_SIG based on a predetermined coefficient α init The differential amplifier 25b multiplies the reference optical sensor signal ref1 by the fluorescence sensor signal PL and the output signal ref1×α init The difference with / β is calculated, and the result of the calculation is output as the CMR signal CMR_SIG.

[0047] The coefficient unit 25a may be provided as a circuit, or the coefficient unit 25a may not be provided, and the gain of the light receiving device 23 may be adjusted to obtain a predetermined coefficient α init Alternatively, a reference optical sensor signal multiplied by / β may be output.

[0048] Furthermore, the measuring device shown in FIG. 1 comprises analog-to-digital converters 26, 27 for digitizing the CMR signal CMR_SIG and the reference sensor signal ref2, respectively, and a processing unit 31 for controlling the measuring device and for signal processing.

[0049] The analog-to-digital converters 26 and 27 digitize the CMR signal CMR_SIG and the reference sensor signal ref2, respectively, with a predetermined bit number and at a predetermined sampling period (speed), and output the digitized CMR signal CMR_SIG and the reference sensor signal ref2 to the calculation processing device 31.

[0050] The arithmetic processing device 31 includes, for example, a computer, and executes a signal processing program on the computer to operate as various processing units. In this embodiment, the arithmetic processing device 31 causes the computer to operate as a measurement control unit 41 and a calculation unit 42, and also includes a non-volatile storage device 43.

[0051] A signal processing program is stored in the storage device 43, and the computer is equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and operates as a measurement control unit 41 and a calculation unit 42 by loading the signal processing program into the RAM and executing it on the CPU.

[0052] The measurement control unit 41 (a) controls the high-frequency power supply 11 and the light emitting device 12 in accordance with a predetermined measurement sequence, and (b) acquires the CMR signal CMR_SIG and the reference optical sensor signal ref2 digitized as described above, stores them in RAM or a storage device 43, and causes the calculation unit 42 to derive measurement values ​​of the measured field.

[0053] This measurement sequence is set according to the frequency of the measured field. For example, when the measured field is a relatively high frequency AC field, a spin echo pulse sequence (Hahn echo sequence, etc.) is applied to this measurement sequence. However, the measurement sequence is not limited to this. Also, for example, when the measured field is a relatively low frequency AC field, the physical field may be measured multiple times in one period of the measured field using a Ramsey pulse sequence (i.e., a measurement sequence of a DC field), and the measured field (intensity, waveform, etc.) may be specified based on the measurement results.

[0054] Fig. 2 is a diagram showing an example of a measurement sequence. Fig. 2 shows the timing of a microwave pulse with respect to the measured magnetic field and the timing of irradiation with excitation light (twice, for initialization and measurement) in the case of a spin echo pulse sequence. As shown in Fig. 2, fluorescence is detected during the irradiation period of the excitation light.

[0055] FIG. 3 is a diagram illustrating the reference optical sensor signals ref1(t) and ref2(t), the fluorescent sensor signal PL(t), the CMR signal CMR_SIG(t), and the detection signal SD(t).

[0056] 3, the reference optical sensor signals ref1(t) and ref2(t) are substantially rectangular pulse signals during the irradiation period, and the fluorescent sensor signal PL(t) is a pulse signal that gradually rises during the irradiation period and converges to a constant level. Then, the CMR signal CMR_SIG(t) is obtained by common mode rejection.

[0057] Then, the calculation unit 42 divides the digitized CMR signal CMR_SIG(t) by the digitized reference optical sensor signal ref2(t) to obtain α cont A detection signal SD(t) proportional to (t) is generated, and a measurement value of the measured field (here, magnetic flux density, magnetic field waveform, etc.) is derived based on the detection signal SD(t).

[0058] Furthermore, the calculation unit 42 performs digital filtering for noise removal on the digitized CMR signal CMR_SIG(t) or the detection signal SD(t).

[0059] In this embodiment, in this digital filtering process, the calculation unit 42 applies a window function to the digitized CMR signal CMR_SIG(t) or the detection signal SD(t) to attenuate high-frequency components (high-frequency noise components) of the signal. The window function is a Finite Impulse Response (FIR) filter.

[0060] 4 is a diagram showing an example of the frequency characteristic of a window function. The above-mentioned window function has a frequency characteristic as shown in FIG. 4, and attenuates high-frequency noise components (in this case, components of about 10 kHz or higher).

[0061] Furthermore, in this embodiment, the calculation unit 42 executes a noise removal process in addition to the above-mentioned digital filtering process. In the noise removal process, the calculation unit 42 (a) integrates the values ​​of digitized CMR signals obtained multiple times (a predetermined number of samples) in the first and second half of the irradiation period of the excitation light, and (b) calculates the difference between the integrated value (sum or average) of the CMR signal for the first half and the integrated value (sum or average) of the CMR signal for the second half to remove noise components in the CMR signal.

[0062] For example, as shown in FIG. 3, during period P1 in the first half (a period of a predetermined length from the start time of irradiation (t=0)), a predetermined number of sampling values ​​of the CMR signal are acquired, and during period P2 in the second half (a period of a predetermined length until the end time of irradiation (t=te)), a predetermined number of sampling values ​​of the CMR signal are acquired. The integrated value of the second half is subtracted from the integrated value of the first half, and the resulting subtraction value is set as the value of the CMR signal, thereby suppressing the noise components of the CMR signal.

[0063] Furthermore, in this embodiment, the analog-digital converter 26 operates at a higher speed than the analog-digital converter 27 , and the analog-digital converter 27 performs digitization with a higher degree of accuracy than the analog-digital converter 26 .

[0064] For example, analog-to-digital converter 26 converts the input analog signal into a 20-bit digital signal, for example at 200M samples / sec, and analog-to-digital converter 27 converts the input analog signal into a 24-bit digital signal, for example at 100k samples / sec.

[0065] Since the CMR signal converted by the analog-to-digital converter 26 changes relatively quickly, it is sampled by the high-speed analog-to-digital converter 26, and noise removal is performed based on multiple sampling as described above. On the other hand, as described above, the reference light center signal ref2 converted by the analog-to-digital converter 27 is a signal that is generated by converting the excitation light noise component I noiseThis is used for division to theoretically eliminate the effect of the level fluctuation α cont (t) and noise component intensity I noise Since it is necessary to divide the product term with a precision according to the voltage level relative to the voltage level of the fluorescent sensor signal PL, the signal is sampled by the analog-to-digital converter 27 with relatively high precision.

[0066] Next, the operation of the measurement device according to the embodiment will be described below. Fig. 5 is a flow chart illustrating the operation (that is, the measurement method) of the measurement device according to the embodiment shown in Fig. 1.

[0067] The sensor unit 10 is disposed at a measurement position in the measured field. Note that the sensor unit 10 may be scanned to perform measurements at each of a plurality of measurement positions.

[0068] Next, the measurement control unit 41 causes the light emitting device 12 to emit excitation light and the high frequency magnetic field generator 2 to emit microwaves in accordance with a predetermined measurement sequence (step S1).

[0069] As a result, during the irradiation period of the excitation light during measurement, the fluorescent sensor signal PL (analog signal) is output from the light receiving device 13, and the reference optical sensor signals ref1 and ref2 (analog signals) are output from the light receiving devices 23 and 24, respectively (step S2). Then, the CMR calculation unit 25 outputs a CMR signal CMR_SIG(t) from the fluorescent sensor signal PL(t) and the reference optical sensor signal ref1, and the CMR signal CMR_SIG(t) is digitized by the analog-to-digital converter 26 (steps S3 and S4). On the other hand, the reference optical sensor signal ref2 is digitized by the analog-to-digital converter 27 (step S4).

[0070] When the measurement control unit 41 acquires this CMR signal CMR_SIG(t) (digital signal) and the reference optical sensor signal ref2 (digital signal), the calculation unit 42 applies a window function to the CMR signal to remove high-frequency noise components (e.g., components of 10 kHz or higher) from the CMR signal CMR_SIG(t) (step S5), and further performs accumulation and difference on multiple values ​​of the CMR signal CMR_SIG(t) sampled multiple times (e.g., 1,000 times) to remove relatively low-frequency noise components (e.g., components of several kHz to 10 kHz) (step S6).

[0071] Then, the calculation unit 42 divides the value of the CMR signal obtained by removing noise in this manner by the value of the reference optical sensor signal ref2 to derive the value of the detection signal (step S7), and derives the measurement value of the measured field at that measurement position and at that measurement timing (the execution timing of the measurement sequence) from the detection signal value (step S7).

[0072] As described above, according to the above embodiment, the high-frequency magnetic field generator 2 performs, by microwaves, the electron spin quantum manipulation of the magnetic resonance member 1, whose electron spin quantum state changes in response to the measured field and whose electron spin quantum manipulation is possible by microwaves. The light emitting device 12 emits excitation light to be irradiated to the magnetic resonance member 1. The light receiving device 13 receives the fluorescence emitted by the magnetic resonance member 1 in response to the excitation light, and generates a fluorescence sensor signal corresponding to the intensity of the fluorescence. The CMR calculation unit 25 performs common mode rejection on the fluorescence sensor signal based on a reference light sensor signal generated by receiving a reference light obtained by splitting the excitation light, and generates a CMR signal based on the common mode rejection. The analog-to-digital converter 26 digitizes the CMR signal, and the analog-to-digital converter 27 digitizes a reference light sensor signal generated by receiving a reference light obtained by splitting the above-mentioned excitation light. The processor 31 divides the digitized CMR signal by the digitized reference optical sensor signal to generate a detection signal, and derives a measurement value of the measured field based on the detection signal. The processor 31 also performs digital filtering to remove noise on the digitized CMR signal or the detection signal.

[0073] As a result, the noise components caused by the excitation light irradiated to the magnetic resonance component 1 are suppressed by the above-mentioned common mode rejection, division, and digital filtering, thereby improving the measurement accuracy.

[0074] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, such changes and modifications are intended to be included within the scope of the claims.

[0075] For example, in the above embodiment, magnetic field measurement is performed based on optically detected magnetic resonance, but temperature measurement etc. can also be performed in a similar manner. Also, current measurement can be performed based on a magnetic field obtained by magnetic field measurement.

[0076] In the above embodiment, the reference light for the above division is branched from the excitation light in addition to the reference light for common mode rejection, but the reference light branched for common mode rejection may also be used as the reference light for the above division. Also, the above reference optical sensor signals ref1 and ref2 are generated separately, but one reference optical sensor signal ref may be generated and used as the above reference optical sensor signals ref1 and ref2.

[0077] Furthermore, in the above embodiment, the window function is applied to the CMR signal, but instead, the window function may be applied to the detection signal.

[0078] In the above embodiment, the differential amplifier 25b may be provided separately from the analog-to-digital converter , or may be built into the analog-to-digital converter . [Industrial Applicability]

[0079] The present invention is applicable, for example, to a measurement device that utilizes optically detected magnetic resonance. [Explanation of symbols]

[0080] 1 Magnetic resonance components 2. High frequency magnetic field generator 3. Magnets 12 Light emitting device 13. Light receiving device (an example of a fluorescent light receiving device) 23 Photodetector 24 Light receiving device 25 CMR calculation section 26 Analog-to-digital converter (an example of a first analog-to-digital converter) 27 Analog-to-digital converter (an example of a second analog-to-digital converter) 31 Processing unit

Claims

1. a magnetic resonance member in which the electron spin quantum state changes in response to a measured field and in which the electron spin quantum state can be manipulated by microwaves; a high frequency magnetic field generator for performing quantum manipulation of electron spins of the magnetic resonance member using the microwave; a light emitting device that emits excitation light to be irradiated onto the magnetic resonance member; a fluorescence receiving device that receives fluorescence emitted by the magnetic resonance member in response to the excitation light and generates a fluorescence sensor signal corresponding to the intensity of the fluorescence; a CMR calculation unit that performs common mode rejection on the fluorescent sensor signal based on a reference light sensor signal generated by receiving a reference light obtained by splitting the excitation light, and generates a CMR signal based on the common mode rejection; a first analog-to-digital converter for digitizing the CMR signal; a second analog-to-digital converter that receives a reference light obtained by splitting the excitation light and digitizes a reference light sensor signal generated by the reference light sensor; a processor for dividing the digitized CMR signal by the digitized reference optical sensor signal to generate a detection signal and deriving a measurement of the measured field based on the detection signal; the arithmetic processing device performs digital filtering for removing noise on the digitized CMR signal or the detection signal; A measuring device comprising:

2. a magnetic resonance member in which an electron spin quantum state changes in response to a measured field and in which electron spin quantum manipulation can be performed by microwaves is subjected to electron spin quantum manipulation of the magnetic resonance member by the microwaves in accordance with a predetermined measurement sequence, and an excitation light to be irradiated to the magnetic resonance member is emitted; receiving fluorescence emitted by the magnetic resonance member in response to the excitation light and generating a fluorescence sensor signal corresponding to an intensity of the fluorescence; performing common mode rejection on the fluorescence sensor signal based on a reference light sensor signal generated by receiving a reference light obtained by splitting the excitation light, and generating a CMR signal based on the common mode rejection; digitizing the CMR signal; digitizing a reference light sensor signal generated by receiving a reference light obtained by splitting the excitation light; dividing the digitized CMR signal by the digitized reference optical sensor signal to generate a detection signal and deriving a measurement of the measured field based on the detection signal; performing digital filtering on the digitized CMR signal or the detection signal to remove noise; A measuring method comprising:

3. digitizing the CMR signal with a first analog-to-digital converter; digitizing the reference photosensor signal with a second analog-to-digital converter; the first analog-to-digital converter operates at a higher speed than the second analog-to-digital converter; the second analog-to-digital converter performs digitization with higher accuracy than the first analog-to-digital converter; 3. The method according to claim 2, further comprising:

4. 3. The measurement method according to claim 2, further comprising the step of generating the reference optical sensor signal, which is digitized and used to generate the detection signal, separately from the reference optical sensor signal used for the common mode rejection.

5. 3. The measurement method according to claim 2, wherein the digital filtering process applies a window function to the digitized CMR signal or the detection signal.

6. 3. The measurement method according to claim 2, further comprising: (a) accumulating the digitized values ​​of the CMR signal obtained multiple times in each of the first and second parts of the irradiation period of the excitation light; and (b) calculating the difference between the accumulated value of the CMR signal for the first half part and the accumulated value of the CMR signal for the second half part to remove noise components in the CMR signal.

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