Measuring device and measuring method

Abstract

To suppress a noise component resulting from irradiation light, so that measurement accuracy is improved.SOLUTION: A light-receiving device 13 receives fluorescence emitted from a magnetic resonance member 1 by corresponding to excitation light and generates a fluorescence sensor signal corresponding to a fluorescence intensity. A CMR arithmetic unit 25 takes into account non-linearity of a fluorescence sensor signal level relative to an amount of excitation light, and applies common mode rejection based on a reference light sensor signal of reference light having branched excitation light, to the fluorescence sensor signal, in order to generate a CMR signal. An A / D converter 26 digitizes the CMR signal, whereas an analog digital converter 27 digitizes the reference light sensor signal. An arithmetic processing device 31 derives a measurement value of a measured place on the basis of the digitized CMR signal and the digitized reference light sensor signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a measuring device and a measuring method.

Background Art

[0002] A certain magnetic field measuring device performs magnetic measurement by optically detected magnetic resonance (ODMR) that utilizes the electron spin resonance of a sensing member such as a diamond structure having nitrogen and lattice defects (NV center: Nitrogen Vacancy Center). In ODMR, a static magnetic field is applied to a magnetic resonance member such as a diamond having such an NV center, separately from 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 fluorescence emitted from the magnetic resonance member is detected, and the magnetic flux density of the magnetic field to be measured is derived based on the detected light amount.

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

[0004] A certain sensor device measures a magnetic field by nuclear magnetic resonance using a diamond sensor including an NV center as described above (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the optically detected magnetic resonance using the electron spin resonance of a sensing member, since the detection signal obtained from fluorescence is weak, it is easily affected by noise. In particular, due to the noise of the irradiation light (laser light), the measurement accuracy becomes low.

[0007] An object of the present invention is to obtain a measuring device and a measuring method that suppress noise components caused by irradiation light and improve measurement accuracy.

Means for Solving the Problems

[0008] The measuring device according to the present invention includes a magnetic resonance member whose electron spin quantum state changes corresponding to the measured field and which enables electron spin quantum operation with microwaves, a high-frequency magnetic field generator that performs electron spin quantum operation of the magnetic resonance member with microwaves, a light-emitting device that emits excitation light to be irradiated to the magnetic resonance member, a fluorescence light-receiving device that receives fluorescence emitted corresponding to the excitation light by the magnetic resonance member and generates a fluorescence sensor signal corresponding to the intensity of the fluorescence, a CMR operation unit that performs common-mode rejection based on a reference light sensor signal generated by receiving reference light obtained by branching the excitation light with respect to the fluorescence sensor signal and generates a CMR signal based on the common-mode rejection, a first analog-to-digital converter that digitizes the CMR signal, a second analog-to-digital converter that digitizes the reference light sensor signal generated by receiving the reference light obtained by branching the excitation light, and an arithmetic processing device that generates a detection signal based on the digitized CMR signal and the digitized reference light sensor signal and derives a measured value of the measured field based on the detection signal. And the CMR operation unit Under the condition that the level of the fluorescence sensor signal is expressed by a function showing non-linearity with respect to the intensity of the excitation light, performs the above-described common-mode rejection. Further, the arithmetic processing device executes digital filter processing for noise removal on the digitized CMR signal or the detection signal.

[0009] The measuring method according to the present invention includes: (a) performing electron spin quantum operation of a magnetic resonance member with microwaves according to a predetermined measurement sequence on a magnetic resonance member whose electron spin quantum state changes corresponding to the measured field and which enables electron spin quantum operation with microwaves, and emitting excitation light to be irradiated to the magnetic resonance member; (b) receiving fluorescence emitted corresponding to the excitation light by the magnetic resonance member and generating a fluorescence sensor signal corresponding to the intensity of the fluorescence; (c) Under the condition that the level of the fluorescence sensor signal is expressed by a function showing non-linearity with respect to the intensity of the excitation lightPerform common mode rejection based on a reference light sensor signal generated by receiving reference light obtained by branching excitation light with respect to the fluorescence sensor signal, generate a CMR signal based on the common mode rejection, (d) digitize the CMR signal, (e) digitize a reference light sensor signal generated by receiving reference light obtained by branching the excitation light, (f) generate a detection signal based on the digitized CMR signal and the digitized reference light sensor signal, and derive a measured value of the field to be measured based on the detection signal. Then, perform digital filter processing for noise removal on the digitized CMR signal or the detection signal.

Advantages of the Invention

[0010] According to the present invention, a measuring device and a measuring method for suppressing noise components caused by irradiation light and increasing measurement accuracy can be obtained.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

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

[0013] FIG. 1 is a block diagram showing the configuration of a measuring device according to an embodiment of the present invention. The measuring 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 (for example, a magnetic field such as the intensity and direction of a magnetic field) at a predetermined position (for example, on or above the surface of an object to be inspected). Note that the measured field may be an alternating field of a single frequency, an alternating field of a predetermined period having a plurality of frequency components, or a direct current field.

[0015] In this embodiment, the sensor unit 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 the electron spin quantum state changes corresponding to the measured field (here, a magnetic field), and is a member capable of performing electron spin quantum operations with microwaves (based on Rabi oscillations) of a frequency corresponding to the arrangement direction of defects and impurities in the crystal lattice. That is, the magnetic resonance member 1 is arranged at the measurement position of the magnetic field.

[0017] In this embodiment, the magnetic resonance member 1 is an optically detected magnetic resonance member having a plurality (that is, an ensemble) of specific color centers. This specific color center has an energy level that can be Zeeman split, and can take a plurality of directions in which the shift widths of the energy levels at the time of Zeeman splitting are different from each other.

[0018] Here, the magnetic resonance member 1 is a member such as a diamond containing a plurality of NV (Nitrogen Vacancy) centers as a single type of specific color center. In the case of an NV center, the ground state is a triplet state with ms = 0, +1, -1, and the levels of ms = +1 and ms = -1 are Zeeman split. When the NV center transitions from the excited states of the levels of ms = +1 and ms = -1 to the ground state, fluorescence occurs at a predetermined rate, and the remaining proportion of NV centers transition non-radiatively from the excited state (ms = +1 or ms = -1) to the ground state (ms = 0).

[0019] Note that 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 operations on 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 supply 11 generates the current of the microwaves and conducts it to the high-frequency magnetic field generator 2. The coil portion conducts two currents parallel to each other at a predetermined interval so as to sandwich the magnetic resonance member 1 at both end face portions thereof, and emits the above-described microwaves. Here, although the coil portion is a plate-shaped coil, due to the skin effect, the current of the microwaves flows through the end face portion of the coil portion, so that two currents are formed. As a result, microwaves with a spatially uniform intensity are applied to the magnetic resonance member 1.

[0021] In the case of an NV center, in a diamond crystal, color centers are formed by defects (vacancies) (V) and nitrogen (N) as impurities. For the defect (vacancy) (V) in the diamond crystal, there are four possible positions for adjacent nitrogen (N) (i.e., the arrangement direction of the pair of vacancy and nitrogen), and the sub-levels (i.e., energy levels from the ground state) 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 a static magnetic field with respect to the frequency of microwaves, four different dip frequency pairs (fi+, fi-) appear corresponding to each direction i (i = 1, 2, 3, 4). Here, the frequency (wavelength) of the above-mentioned microwaves is set corresponding to any one of the dip frequencies of these four dip frequency pairs.

[0022] Further, the magnet 3 applies a static magnetic field (DC magnetic field) to the magnetic resonance member 1, causing Zeeman splitting of 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, for example, a ferrite magnet, an alnico magnet, a samacoba magnet, or the like.

[0023] In this embodiment, the application direction of the above-mentioned static magnetic field is the same as the application direction of the above-mentioned magnetic field to be measured. By applying the above-mentioned static magnetic field, the change in fluorescence intensity at the above-mentioned dip frequency is enhanced, and the sensitivity is increased.

[0024] Furthermore, in this embodiment, the magnetic resonance member 1 includes a plurality of color centers (here, NV centers) capable of electron spin quantum operation with 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 such that the difference or ratio between the maximum value and the minimum value of the intensity of the static magnetic field in the predetermined region is below a predetermined value.

[0025] In addition, in the magnetic resonance member 1, the crystal of the magnetic resonance member 1 is formed and the orientation of the magnetic resonance member 1 is set so that the arrangement directions of the above-described defects and impurities substantially coincide with the direction of the above-described static magnetic field (and the direction of the applied magnetic field).

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

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

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

[0029] The intensity I of the above-described excitation light is the sum of the original intensity I laser and the intensity I of the noise component noise This noise component is generated due to fluctuations in the power supply voltage of the light-emitting device 12, fluctuations in the light emission amount of the light source, etc., and has a frequency in the range from about the kHz order to about the 100 kHz order, for example.

[0030] I = I laser + I noise

[0031] In addition, the level of the fluorescence sensor signal PL basically increases as the intensity I of the excitation light increases. However, due to the change in the electron spin quantum state caused by the measurement target field, the fluorescence intensity at the start of excitation light irradiation during measurement is low, and then the fluorescence intensity gradually increases until the influence of the change in the electron spin quantum state caused by the measurement target field disappears. Therefore, the level fluctuation α cont (t) of the fluorescence sensor signal PL caused by the change in the electron spin quantum state due to the measurement target field is proportional to the detection signal SD, which is derived as a signal indicating the measurement target field. The fluorescence sensor signal PL is expressed by the following equation. Here, since the fluorescence intensity is relatively low, the level of the fluorescence sensor signal PL has non-linearity. FIG. 2 is a diagram for explaining the non-linearity of the level of the fluorescence sensor signal with respect to the light quantity of the excitation light. For example, as shown in FIG. 2, the slope of the level of the fluorescence sensor signal PL becomes larger as the fluorescence intensity becomes smaller.

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

[0033] Here, α init is a coefficient indicating a part proportional to the intensity I of the excitation light (a part not affected by the change in the electron spin quantum state caused by the measurement target field), and f is a function indicating non-linearity with respect to the intensity I of the excitation light. For example, f is an N-th order equation (N ≧ 2), and in this embodiment, f is a second-order equation (f(x) = x + γ · x 2 , γ is a constant). The fluorescence sensor signal PL in this case is expressed by the following equation.

[0034] Note that this function f and the constant γ are derived in advance by experiments on the sensor of the light receiving device 13 or the like. Also, this function f may have other functional forms such as an exponential function.

[0035] PL(t) = α(t) × f(I) = (α init + αcont (t))×I=(α init +α cont (t))×{(I laser +I noise )+γ(I laser +I noise ) 2}=α init {(γI laser 2 +I laser )+(2γI laser +1)I noise +γI noise 2}+α cont (t){(I laser +I noise )+γ(I laser +I noise ) 2}

[0036] On the other hand, since the level ref of the reference light sensor signal of the reference light branched from the excitation light is proportional to the intensity I of the excitation light, it is expressed by the following equation. Here, since the intensity of the reference light is relatively high, the level of the reference light sensor signal PL is linear (proportional) with respect to the reference light intensity.

[0037] ref=ref1=ref2=β×I=β×(I laser +I noise )

[0038] Here, β is a constant. Note that ref1 and ref2 will be described later.

[0039] Specifically, PL is obtained by Taylor expansion and ignoring the terms of the third order and higher because I noise <<I laser . Also, as follows, by Taylor expanding (Maclaurin expanding) the above-mentioned PL and ref with respect to I noise and ignoring the terms of the third order and higher for approximation, the CMR signal CMR_SIG(t) is derived from the PL and ref. Note that in the following equations, PL(I laser +I noise ) indicates that PL is a function of (I laser +I noise ), and PL(Ilaser ) is the PL when I noise is set to 0. Similarly, ref(I laser +I noise ) indicates that ref is a function of (I laser +I noise ), and ref(I laser ) is the ref when I noise is set to 0. Note that PL’ is the first derivative coefficient of PL with respect to I noise at I noise = 0, and ref’ is the first derivative coefficient of ref with respect to I noise at I noise = 0.

[0040] PL(I laser +I noise ) = PL(I laser ) + PL’(I laser )I noise + ···

[0041] ref(I laser +I noise ) = ref(I laser ) + ref’(I laser )I noise + ···

[0042] Here, since I noise << I laser , the terms of I noise after the third order can be ignored. Therefore, the above PL and ref are approximated by the following equations.

[0043] PL(I laser +I noise ) = PL(I laser ) + PL’(I laser )I noise

[0044] ref(I laser +I noise ) = ref(I laser ) + ref’(I laser )I noise

[0045] Here, common mode rejection is performed on PL(t), and a CMR signal is generated. Specifically, the CMR signal CMR_SIG(t) is derived by the following equation so that the influence of α init on I noise is removed.

[0046] CMR_SIG(t)=PL-(PL’(I laser ) / ref’(I laser ))ref

[0047] Here, since PL’(I laser ) / ref’(I laser ) = α init (2γI laser +1) / β, the CMR signal CMR_SIG(t) becomes as follows. In the following equation, in order to remove the constant term (described later) regardless of time t, the constant α init γI laser 2 is added.

[0048] CMR_SIG(t)=PL(t)-α init (2γI laser +1) / β×ref(t)+α init γI laser 2 =α cont (t){(I laser +I noise )+γ(I laser +I noise ) 2}

[0049] Here, regarding α init {(I laser +I noise )+γ(I laser +I noise ) 2} in PL(t), the term γI noise 2 which is sufficiently small is ignored, and α init {(I laser +I noise )+γ(I laser +I noise ) 2}=α init (γIlaser +1)I laser +α init (2γI laser +1)I noise =α init (2γI laser +1)×(I laser +I noise )-α init γI laser is used as

[0050] And the detection signal SD(t) described above is derived as follows. Thus, the influence of I on α cont (t) is removed. noise is removed.

[0051] SD(t)=α cont (t)=CMR_SIG(t) / (ref(t)+γ·ref(t) 2 )

[0052] Since the peak value (the value at t = 0) and the time integral value of the detection signal SD(t) are correlated with the intensity of the field to be measured, the correspondence between the peak value or the time integral value of the detection signal SD(t) and the intensity of the field to be measured is specified in advance through experiments or the like, and the intensity of the field to be measured is derived from the peak value or the time integral value of the detection signal SD(t) using a calculation formula or a table showing the correspondence.

[0053] Based on such a measurement principle, the configuration described below is provided.

[0054] The measuring device shown in FIG. 1 further includes optical separation units 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 separation units 21 and 22 each branch a part of the excitation light and emit it in another direction as reference light. For example, the optical separation units 21 and 22 are non - polarization - dependent beam splitters.

[0055] Also, the measuring device shown in FIG. 1 includes light receiving devices 23 and 24 that receive the reference light and generate reference light sensor signals ref1 and ref2 (ref described above) corresponding to the intensity of the reference light.

[0056] In this embodiment, two reference lights are separately generated from the excitation light, and two reference light sensor signals ref1 and ref2 are generated. The reference light sensor signal ref1 is used for common mode rejection described later, and the reference light sensor signal ref2 is digitized and used for generating the detection signal SD.

[0057] Furthermore, the measuring device shown in FIG. 1 includes a CMR operation unit 25 as an analog operation circuit. The CMR operation unit 25 performs common mode rejection on the fluorescence sensor signal PL based on the reference light sensor signal ref1, and generates a CMR signal CMR_SIG based on the common mode rejection. Specifically, the CMR operation unit 25 includes a coefficient unit 25a, an offset removal unit 25b, and a differential amplifier 25c. The coefficient unit 25a multiplies the reference light sensor signal ref1 by a predetermined coefficient α init (2γI laser +1) / β. The offset removal unit 25b subtracts the constant α init γI laser 2 indicating the above-mentioned offset from the output signal ref1×α init (2γI laser +1) / β of the coefficient unit 25a. The differential amplifier 25c calculates the difference between the fluorescence sensor signal PL and the output signal ref1×α init (2γI laser +1) / β - α init γI laser 2 of the offset removal unit 25b, and outputs the calculation result as the CMR signal CMR_SIG. In FIG. 1, the offset removal unit 25b subtracts the constant α init γI laser 2 indicating the above-mentioned offset from the output signal ref1×α init (2γI laser +1) / β of the coefficient unit 25a. Instead, the constant α init γI laser 2 indicating the above-mentioned offset may be added to the fluorescence sensor signal PL, or the constant α init γI laser2 It may be added to the output signal of the differential amplifier 25c.

[0058] In addition, a coefficient unit 25a as an analog arithmetic circuit may be provided, or without providing the coefficient unit 25a, the gain of the light receiving device 23 may be adjusted to multiply a reference optical sensor signal by a predetermined coefficient α init (2γI laser +1) / β.

[0059] Furthermore, the measuring device shown in FIG. 1 includes analog-to-digital converters 26 and 27 that digitize the CMR signal CMR_SIG and the reference sensor signal ref2, respectively, and an arithmetic processing unit 31 that controls and processes signals of the measuring device.

[0060] The analog-to-digital converters 26 and 27 digitize the CMR signal CMR_SIG and the reference sensor signal ref2, respectively, at a predetermined number of bits and a predetermined sampling period (speed), and output the digitized CMR signal CMR_SIG and reference sensor signal ref2 to the arithmetic processing unit 31.

[0061] The arithmetic processing unit 31 includes, for example, a computer, and operates as various processing units by executing a signal processing program on the computer. In this embodiment, the arithmetic processing unit 31 operates the computer as a measurement control unit 41 and an arithmetic unit 42, and also includes a non-volatile storage device 43.

[0062] A signal processing program is stored in the storage device 43. The computer includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., loads the signal processing program into the RAM, and executes it with the CPU to operate as the measurement control unit 41 and the arithmetic unit 42.

[0063] The measurement control unit 41 controls the high-frequency power supply 11 and the light-emitting device 12 according to a predetermined measurement sequence, acquires the CMR signal CMR_SIG and the reference optical sensor signal ref2 digitized as described above, stores them in the RAM or the storage device 43, and causes the arithmetic unit 42 to derive a measurement value of the field to be measured.

[0064] This measurement sequence is set according to the frequency of the field to be measured and the like. For example, when the field to be measured is an alternating field with a relatively high frequency, a spin echo pulse sequence (such as a Hahn echo sequence) is applied to this measurement sequence. However, the measurement sequence is not limited to this. Also, for example, when the field to be measured is an alternating field with a relatively low frequency, in one cycle of the field to be measured, the Ramsey pulse sequence (that is, the measurement sequence for a DC field) is used multiple times to measure the physical field, and based on the measurement results, the field to be measured (intensity, waveform, etc.) may be specified.

[0065] FIG. 3 is a diagram showing an example of a measurement sequence. FIG. 3 shows the timing of microwave pulses and the irradiation timing of excitation light (twice for initialization and measurement) with respect to the magnetic field to be measured in the case of a spin echo pulse sequence. As shown in FIG. 3, fluorescence is detected during the irradiation period of the excitation light.

[0066] FIG. 4 is a diagram for explaining the reference optical sensor signals ref1(t), ref2(t), the fluorescence sensor signal PL(t), the CMR signal CMR_SIG(t), and the detection signal SD(t).

[0067] As shown in FIG. 4, the reference optical sensor signals ref1(t), ref2(t) are pulse signals in a substantially rectangular shape during the irradiation period, and the fluorescence sensor signal PL(t) is a pulse signal that gradually rises and converges to a certain level during the irradiation period. Then, the CMR signal CMR_SIG(t) is obtained by common mode rejection.

[0068] Then, as described above, the arithmetic unit 42 calculates and generates a detection signal SD(t) proportional to α cont (t) from the digitized CMR signal CMR_SIG(t) and the digitized reference optical sensor signal ref2(t), and derives a measured value of the field to be measured (here, magnetic flux density, magnetic field waveform, etc.) based on the detection signal SD(t).

[0069] Also, the arithmetic unit 42 performs digital filter processing for noise removal on the digitized CMR signal CMR_SIG(t) or the detection signal SD(t).

[0070] In this embodiment, the arithmetic unit 42 applies a window function to the digitized CMR signal CMR_SIG(t) or the detection signal SD(t) in this digital filter processing to attenuate the high-frequency components (high-frequency noise components) of the signal. The window function is a FIR (Finite Impulse Response) filter.

[0071] FIG. 5 is a diagram showing an example of the frequency characteristics of the window function. The above-described window function has frequency characteristics as shown in FIG. 5, for example, and attenuates high-frequency noise components (in this case, components of about 10 kHz or more).

[0072] Furthermore, in this embodiment, the arithmetic unit 42 performs noise removal processing separately from the above-described digital filter processing. In the noise removal processing, the arithmetic unit 42 (a) integrates the values of the digitized CMR signals obtained a plurality of times (predetermined number of samplings) in the first half and the second half of the excitation light irradiation period, respectively, and (b) calculates the difference between the integrated value (sum or average) of the CMR signals for the first half and the integrated value (sum or average) of the CMR signals for the second half to remove the noise components in the CMR signal.

[0073] For example, as shown in FIG. 4, in the first half period P1 (a period of a predetermined time length from the irradiation start time (t = 0)), the values of the CMR signals for a predetermined number of samplings are acquired. In the second half period P2 (a period of a predetermined time length until the irradiation end time (t = te)), the values of the CMR signals for a predetermined number of samplings are acquired. By subtracting the integrated value of the second half from the integrated value of the first half and using the value of the subtraction result as the value of the CMR signal, the noise component of the CMR signal is suppressed.

[0074] Also, in this embodiment, the analog-to-digital converter 26 operates faster than the analog-to-digital converter 27, and the analog-to-digital converter 27 performs digitization with higher precision than the analog-to-digital converter 26.

[0075] For example, the analog-to-digital converter 26 converts an input analog signal into a 20-bit digital signal at, for example, 200 M samples / second, and the analog-to-digital converter 27 converts an input analog signal into a 24-bit digital signal at, for example, 100 k samples / second.

[0076] Note that since the CMR signal analog-to-digital 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 based on multiple samplings is performed as described above. On the other hand, as described above, the reference optical sensor signal ref2 analog-to-digital converted by the analog-to-digital converter 27 is used for an operation to theoretically cancel the influence of the noise component I noise of the excitation light in the CMR signal. Since it is necessary to perform the operation with an accuracy corresponding to the relative voltage level with respect to the voltage level of the fluorescence sensor signal PL for the term of the product of the level fluctuation α cont (t) in the detected fluorescence sensor signal PL and the noise component intensity I noise , it is sampled by the relatively high-precision analog-to-digital converter 27.

[0077] Next, the operation of the measuring device according to this embodiment will be described. FIG. 6 is a flowchart for explaining the operation (that is, the measuring method) of the measuring device according to the embodiment shown in FIG. 1.

[0078] The sensor unit 10 is arranged at the measurement position of the field to be measured. Note that measurements may be performed at a plurality of measurement positions while scanning the sensor unit 10.

[0079] 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 send out microwaves according to a predetermined measurement sequence (step S1).

[0080] As a result, during the irradiation period of the excitation light during measurement, a fluorescence sensor signal PL (analog signal) is output from the light receiving device 13, and reference light sensor signals ref1 and ref2 (analog signals) are respectively output from the light receiving devices 23 and 24 (step S2). Then, a CMR signal CMR_SIG(t) is output from the fluorescence sensor signal PL(t) and the reference light sensor signal ref1 by the CMR operation unit 25 and digitized by the analog-to-digital converter 26 (steps S3 and S4). On the other hand, the reference light sensor signal ref2 is digitized by the analog-to-digital converter 27 (step S4).

[0081] When the measurement control unit 41 acquires this CMR signal CMR_SIG(t) (digital signal) and the reference light sensor signal ref2 (digital signal), the operation unit 42 applies a window function to the CMR signal to remove high-frequency noise components (for example, components of 10 kHz or higher) from the CMR signal CMR_SIG(t) (step S5), and further performs integration and difference on a plurality of values of the CMR signal CMR_SIG(t) sampled a plurality of times (for example, 1000 times) to remove relatively low-frequency noise components (for example, components of several kHz to 10 kHz) (step S6).

[0082] Then, the arithmetic unit 42 derives the value of the detection signal SD(t) based on the value of the CMR signal obtained by noise removal in this way and the value of the reference light sensor signal ref2 (step S7), and derives the measured value of the field to be measured at the measurement position and the measurement timing (the execution timing of the measurement sequence) from the value of the detection signal SD(t) (step S7).

[0083] As described above, according to the above embodiment, the high-frequency magnetic field generator 2 performs microwave electron spin quantum operation on the electron spin quantum operation of the magnetic resonance member 1 whose electron spin quantum state changes corresponding to the field to be measured and which can perform electron spin quantum operation with microwaves. The light-emitting device 12 emits excitation light to be irradiated on the magnetic resonance member 1. The light-receiving device 13 receives the fluorescence emitted corresponding to the excitation light by the magnetic resonance member 1 and generates a fluorescence sensor signal corresponding to the intensity of the fluorescence. The CMR arithmetic unit 25 performs common mode rejection on the fluorescence sensor signal based on the reference light sensor signal generated by receiving the reference light obtained by branching 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 the reference light sensor signal generated by receiving the reference light obtained by branching the above-described excitation light. The arithmetic processing unit 31 generates a detection signal based on the digitized CMR signal and the digitized reference light sensor signal, and derives the measured value of the field to be measured based on the detection signal. Then, the CMR arithmetic unit 25 performs the above-described common mode rejection in consideration of the non-linearity of the level of the fluorescence sensor signal with respect to the light amount of the above-described excitation light. Further, the arithmetic processing unit 31 executes digital filter processing for noise removal on the digitized CMR signal or the detection signal.

[0084] As a result, due to the above-mentioned common mode rejection, the calculation of the detection signal using the reference light sensor signal, and the digital filter processing, the noise components caused by the excitation light irradiated on the magnetic resonance member 1 are suppressed, so the measurement accuracy is improved. Furthermore, since the non-linearity of the level of the fluorescence sensor signal with respect to the amount of the above-mentioned excitation light is taken into account, the measurement accuracy is improved.

[0085] It should be noted that various changes and modifications to the above-described embodiments are obvious 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 weakening the intended advantages. That is, it is intended that such changes and modifications be included in the claims.

[0086] For example, in the above embodiment, the magnetic field measurement is performed based on the photo-detection magnetic resonance, but temperature measurement and the like can also be similarly performed. Also, it is possible to perform current measurement based on the magnetic field obtained by the magnetic field measurement.

[0087] Also, in the above embodiment, the reference light for the calculation of the detection signal using the above-mentioned reference light sensor signal is branched from the excitation light separately from the reference light for the common mode rejection. However, the reference light branched for the common mode rejection may also be used as the reference light for the calculation of the detection signal using the above-mentioned reference light sensor signal. Also, although the above-mentioned reference light sensor signals ref1 and ref2 are generated separately, it is also possible to generate one reference light sensor signal ref and use the reference light sensor signal ref as the above-mentioned reference light sensor signals ref1 and ref2.

[0088] Also, in the above embodiment, a window function is applied to the CMR signal, but instead, a window function may be applied to the detection signal.

[0089] Also, in the above embodiment, the differential amplifier 25b may be provided separately from the analog-to-digital converter 26, or may be incorporated in the analog-to-digital converter 26.

Industrial Applicability

[0090] The present invention is applicable to, for example, a measuring device using photo-detection magnetic resonance.

Explanation of Signs

[0091] 1 Magnetic resonance member 2 High-frequency magnetic field generator 3 Magnet 12 Light-emitting device 13 Light-receiving device (an example of a fluorescence light-receiving device) 23 Light-receiving device 24 Light-receiving device 25 CMR arithmetic unit 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 Arithmetic processing unit

Claims

1. A nuclear magnetic resonance member whose electron spin quantum state changes corresponding to a measurement target field and which enables electron spin quantum operation with microwaves, A high-frequency magnetic field generator that performs electron spin quantum operation of the nuclear magnetic resonance member with the microwaves, A light-emitting device that emits excitation light to be irradiated onto the nuclear magnetic resonance member, A fluorescence light-receiving device that receives fluorescence emitted corresponding to the excitation light by the nuclear magnetic resonance member and generates a fluorescence sensor signal corresponding to the intensity of the fluorescence, A CMR arithmetic unit that performs common mode rejection based on a reference light sensor signal generated by receiving reference light obtained by branching the excitation light with respect to the fluorescence sensor signal, and generates a CMR signal based on the common mode rejection, A first analog-to-digital converter that digitizes the CMR signal, A second analog-to-digital converter that digitizes a reference light sensor signal generated by receiving reference light obtained by branching the excitation light, An arithmetic processing device that generates a detection signal based on the digitized CMR signal and the digitized reference light sensor signal, and derives a measured value of the measurement target field based on the detection signal, The CMR arithmetic unit performs the common mode rejection under the condition that the level of the fluorescence sensor signal is expressed by a function showing non-linearity with respect to the intensity of the excitation light, The arithmetic processing device executes digital filter processing for noise removal on the digitized CMR signal or the detection signal, A measuring device characterized by the above.

2. With respect to a nuclear magnetic resonance member whose electron spin quantum state changes corresponding to a measurement target field and which enables electron spin quantum operation with microwaves, according to a predetermined measurement sequence, the electron spin quantum operation of the nuclear magnetic resonance member is performed with the microwaves, and excitation light to be irradiated onto the nuclear magnetic resonance member is emitted, Fluorescence emitted corresponding to the excitation light by the nuclear magnetic resonance member is received to generate a fluorescence sensor signal corresponding to the intensity of the fluorescence, Under the condition that the level of the fluorescence sensor signal is expressed by a function showing non-linearity with respect to the intensity of the excitation light, common mode rejection based on a reference light sensor signal generated by receiving reference light obtained by branching the excitation light is performed on the fluorescence sensor signal, and a CMR signal based on the common mode rejection is generated, The CMR signal is digitized, Digitize the reference light sensor signal generated by receiving the reference light obtained by branching the excitation light, generate a detection signal based on the digitized CMR signal and the digitized reference light sensor signal, and derive a measured value of the field to be measured based on the detection signal, perform digital filter processing for noise removal on the digitized CMR signal or the detection signal, A measurement method characterized by the above.

3. Perform common mode rejection based on the reference light sensor signal under the condition that the level of the fluorescence sensor signal is expressed by an N-th order equation of the intensity of the excitation light, and generate a CMR signal based on the common mode rejection, wherein N is any number of 2 or more, The measurement method according to claim 2, characterized by the above.

4. Digitize the CMR signal with a first analog-to-digital converter, Digitize the reference light sensor signal with a second analog-to-digital converter, The first analog-to-digital converter operates faster 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, The measurement method according to claim 2, characterized by the above.

5. The measurement method according to claim 2, characterized in that, separately from the reference light sensor signal used for the common mode rejection, a reference light sensor signal that is digitized and used for generating the detection signal is generated.

6. The measurement method according to claim 2, characterized in that in the digital filter processing, a window function is applied to the digitized CMR signal or the detection signal.

7. (a) Integrate the values of the digitized CMR signals obtained a plurality of times respectively in the first half and the second half of the irradiation period of the excitation light, and (b) calculate the difference between the integrated value of the CMR signal for the first half and the integrated value of the CMR signal for the second half to remove the noise component in the CMR signal. The measurement method according to claim 2, characterized by the above.

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