Electromagnetic wave measuring device, method, program, and recording medium

Abstract

To facilitate acquiring a component of a frequency spectrum not dependent on a measurement object (a so-called a base line).SOLUTION: An electromagnetic wave measuring device 1 measures a measurement object on the basis of post-irradiation electromagnetic wave obtained by irradiating a target body including the measurement object with a pre-irradiation electromagnetic wave. The post-irradiation electromagnetic wave includes a response component B from the measurement object and a background component A corresponding to the pre-irradiation electromagnetic wave. The electromagnetic wave measuring device 1 comprises: a first frequency spectrum acquisition unit 18a for acquiring the frequency spectrum of a first signal including the background component A and response component B in the post-irradiation electromagnetic wave; a second frequency spectrum acquisition unit 18b for acquiring the frequency spectrum of a second signal including the background component A in the post-irradiation electromagnetic wave; and a subtraction unit 19 for subtracting the frequency spectrum of the second signal from the frequency spectrum of the first signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to measuring frequency spectra. [Background technology]

[0002] It has been known in the past to acquire a signal containing free induction decay (FID) that occurs after pulse excitation of a gas, and measure the concentration of a predetermined gas component based on the frequency spectrum (see, for example, Patent Document 2). In this frequency spectrum, absorption is observed at a predetermined frequency corresponding to the predetermined gas component.

[0003] In order to determine the depth of this absorption, it is necessary to determine a component of the frequency spectrum that is not dependent on the predetermined gas being measured (hereinafter, sometimes referred to as the "baseline").

[0004] To obtain a baseline, it is known that a path through which a pulse passes (however, it does not pass through a gas cell containing a gas) is used as a reference path (the reference path may be formed by removing the gas cell from the signal path described below), and the frequency spectrum of a pulse that has passed through this reference path is measured and used as the baseline (see, for example, Patent Document 1, Patent Document 3, and Non-Patent Document 1). However, since the reference path is different from the signal path through which a pulse passes (however, it is assumed that the pulse passes through the gas cell), conditions such as pulse reflection differ between the two paths, and therefore the baseline cannot always be obtained accurately.

[0005] It is also known that, in order to obtain a baseline, a path through which a pulse passes (however, the path passes through a gas cell from which gas has been removed (or an empty cell containing no gas)) is used as a reference path, and the frequency spectrum of a pulse that has passed through this reference path is measured and used as the baseline (see, for example, Non-Patent Document 2). However, it takes time to remove gas from a gas cell, and the baseline may fluctuate over this time.

[0006] Furthermore, in order to obtain the baseline, it is known to approximate the baseline by a polynomial for each narrow frequency range, in view of the fact that the baseline fluctuates slowly in narrow frequency ranges (see, for example, Non-Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2021 / 261240 [Patent Document 2] Special Publication No. 2016-521859 [Patent Document 3] U.S. Patent No. 9,557,219 [Non-Patent Document 1] Albert Schliesser,et.al. “Frequency-comb infrared spectrometer for rapid, remote chemical sensing”, Optics Express, 2005, Vol. 13, Issue 22 p.9029-9038 [Non-patent document 2] S.Okubo,et.al., “Ultra-broadband dual-comb spectroscopy across1.0-1.9μm”, Applied Physics Express, 2015, 8, 082402 [Non-patent document 3] GB Rieker, FR Giorgetta, WC Swann,et.al., “Frequency-comb-based remote sensing of greenhouse gases over kilometer air paths”, Optica, 2014,Vol. 1, Issue 5, p. 290-298 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in order to approximate the baseline with a polynomial, the baseline must be approximated for each narrow frequency range, and therefore the approximation must be repeated many times, which is cumbersome.

[0009] Therefore, an object of the present invention is to easily acquire a component of the frequency spectrum that is independent of the measurement target (so-called baseline). [Means for solving the problem]

[0010] An electromagnetic wave measuring device according to the present invention is an electromagnetic wave measuring device that measures an object to be measured based on post-irradiation electromagnetic waves obtained by irradiating a pre-irradiation electromagnetic wave onto an irradiated body having the object to be measured, wherein the post-irradiation electromagnetic wave has a response component from the object to be measured and a background component corresponding to the pre-irradiation electromagnetic wave, and the electromagnetic wave measuring device is configured to include: a first frequency spectrum acquiring unit that acquires the frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave; a second frequency spectrum acquiring unit that acquires the frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave; and a subtraction unit that subtracts the frequency spectrum of the second signal from the frequency spectrum of the first signal.

[0011] According to the electromagnetic wave measuring device configured as described above, an object to be measured is measured based on a post-irradiation electromagnetic wave obtained by irradiating a pre-irradiation electromagnetic wave onto an irradiated object having the object to be measured. The post-irradiation electromagnetic wave has a response component from the object to be measured and a background component corresponding to the pre-irradiation electromagnetic wave. A first frequency spectrum acquisition unit acquires a frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave. A second frequency spectrum acquisition unit acquires a frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave. A subtraction unit subtracts the frequency spectrum of the second signal from the frequency spectrum of the first signal.

[0012] In addition, in the electromagnetic wave measuring device of the present invention, the post-irradiation electromagnetic wave may further have a no-signal component that is neither the background component nor the response component, and the second signal may further include at least a portion of the no-signal component.

[0013] In the electromagnetic wave measuring device according to the present invention, the time length of the first signal may be equal to the time length of the second signal.

[0014] In addition, in the electromagnetic wave measuring device of the present invention, the post-irradiation electromagnetic wave may further have a non-signal component that is neither the background component nor the response component, and the first signal may further include at least a portion of the non-signal component.

[0015] In the electromagnetic wave measuring device according to the present invention, the waveform of the post-irradiation electromagnetic wave may be acquired by dual comb spectroscopy.

[0016] In the electromagnetic wave measuring device according to the present invention, the waveform of the post-irradiation electromagnetic wave may be acquired by terahertz time domain spectroscopy.

[0017] In the electromagnetic wave measuring device according to the present invention, the waveform of the post-irradiation electromagnetic wave may be acquired by a pump-probe method.

[0018] In the electromagnetic wave measuring device according to the present invention, the response component may be a free induction decay signal.

[0019] In the electromagnetic wave measuring device according to the present invention, the irradiated object may be a gas.

[0020] In the electromagnetic wave measuring device according to the present invention, the object to be irradiated may be accommodated in a gas cell.

[0021] The electromagnetic wave measuring device according to the present invention may measure the concentration of the measurement target.

[0022] In the electromagnetic wave measuring device according to the present invention, the object to be irradiated may be a liquid or a solid.

[0023] The electromagnetic wave measuring device according to the present invention may measure the presence or absence of the measurement object.

[0024] The present invention is an electromagnetic wave measurement method for measuring a measurement object based on a post-irradiation electromagnetic wave obtained by irradiating a pre-irradiation electromagnetic wave onto an irradiated object having the measurement object, wherein the post-irradiation electromagnetic wave has a response component from the measurement object and a background component corresponding to the pre-irradiation electromagnetic wave, and the electromagnetic wave measurement method includes a first frequency spectrum acquisition step of acquiring a frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave, a second frequency spectrum acquisition step of acquiring a frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave, and a subtraction step of subtracting the frequency spectrum of the second signal from the frequency spectrum of the first signal.

[0025] The present invention is a program for causing a computer to execute an electromagnetic wave measurement process for measuring an object to be measured based on post-irradiation electromagnetic waves obtained by irradiating a pre-irradiation electromagnetic wave onto an irradiated object having the object to be measured, wherein the post-irradiation electromagnetic wave has a response component from the object to be measured and a background component corresponding to the pre-irradiation electromagnetic wave, and the electromagnetic wave measurement process includes a first frequency spectrum acquisition step for acquiring a frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave, a second frequency spectrum acquisition step for acquiring a frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave, and a subtraction step for subtracting the frequency spectrum of the second signal from the frequency spectrum of the first signal.

[0026] The present invention is a computer-readable recording medium having recorded thereon a program for causing a computer to execute an electromagnetic wave measurement process for measuring a measurement object based on post-irradiation electromagnetic waves obtained by irradiating a pre-irradiation electromagnetic wave onto an irradiated object having the measurement object, wherein the post-irradiation electromagnetic wave has a response component from the measurement object and a background component corresponding to the pre-irradiation electromagnetic wave, and the electromagnetic wave measurement process includes a first frequency spectrum acquisition step for acquiring a frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave, a second frequency spectrum acquisition step for acquiring a frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave, and a subtraction step for subtracting the frequency spectrum of the second signal from the frequency spectrum of the first signal. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a diagram showing a configuration of an electromagnetic wave measuring device 1 according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing the waveform of an interference signal. [Figure 3] 3(a) shows the frequency spectrum of a first signal acquired by a first frequency spectrum acquisition unit 18a, and FIG. 3(b) shows the frequency spectrum of a second signal acquired by a second frequency spectrum acquisition unit 18b. [Figure 4]FIG. 10 is a diagram showing the output of a subtraction unit 19. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0029] 1 is a diagram showing the configuration of an electromagnetic wave measuring device 1 according to an embodiment of the present invention. The electromagnetic wave measuring device 1 according to an embodiment of the present invention measures an irradiated body having a measurement target.

[0030] For example, the object to be irradiated is a gas, which is contained in a gas cell (DUT2 in the embodiment of the present invention). More specifically, the gas flows into the gas cell and is discharged from the gas cell. The gas has a measurement target (for example, molecules in the gas). The electromagnetic wave measuring device 1 may also measure the concentration of the measurement target. The method for measuring the concentration of the measurement target is well known, so a description thereof will be omitted.

[0031] The electromagnetic wave measuring device 1 according to the embodiment of the present invention includes a signal comb generator 12a, a local comb generator 12b, a bandpass filter 14, an interference signal acquirer 16, a first frequency spectrum acquirer 18a, a second frequency spectrum acquirer 18b, and a subtractor 19.

[0032] The signal comb generation unit 12a generates a pre-irradiation signal comb (pre-irradiation electromagnetic waves before being irradiated to the irradiated object). The local comb generation unit 12b generates a local comb. The pre-irradiation signal comb and local comb are optical combs. When the pre-irradiation electromagnetic waves are irradiated to the irradiated object housed in the DUT 2, post-irradiation electromagnetic waves are obtained. The electromagnetic wave measurement device 1 measures the measurement object based on these post-irradiation electromagnetic waves. The waveform of the post-irradiation electromagnetic waves is obtained by dual comb spectroscopy.

[0033] For example, the repetition frequency of the pre-irradiation signal comb is fs. Also, for example, the repetition frequency of the local comb is fL. However, the local comb differs from the repetition frequency fs of the pre-irradiation signal comb by a predetermined difference frequency Δf (= fs - fL). The frequencies of the pre-irradiation signal comb and the local comb are roughly the same as the frequency of light.

[0034] When the pre-irradiation signal comb is irradiated onto the object (gas) to be irradiated within the DUT (gas cell) 2, the pre-irradiation signal comb passes through the DUT 2, resulting in a post-irradiation signal comb (post-irradiation electromagnetic wave). The post-irradiation signal comb is also an optical comb, just like the pre-irradiation signal comb. The post-irradiation signal comb is then passed to the bandpass filter 14, and the passed components are then passed to the interference signal acquisition unit 16.

[0035] It is assumed that the power of the light irradiated onto the object to be irradiated within the DUT 2 changes to become lower (meaning light absorption) at a predetermined frequency corresponding to the object to be measured.

[0036] The bandpass filter 14 passes signals in a band near a predetermined frequency corresponding to the measurement target, but the passband of the bandpass filter 14 is set to a predetermined value or less to suppress the occurrence of aliasing.

[0037] That is, the frequency difference between the post-irradiation signal comb and the local comb increases by Δf, such as 0, Δf, 2Δf, ..., and when it reaches a maximum value of fL / 2, it decreases by Δf. Therefore, the passband of the bandpass filter 14 is determined so that the frequency difference between the post-irradiation signal comb and the local comb is between 0 and fL / 2 or between fL / 2 and fL.

[0038] For example, suppose that the frequency of the signal comb after irradiation is mfs (where m is a positive integer) and is equal to the frequency of the local comb. In this case, the passband of the bandpass filter 14 is from frequency mfs to frequency mfs + (1 / 2)Mfs (where MΔf = fL, and M is a positive integer). However, mfs < (a predetermined frequency corresponding to the measurement target). <mfs+(1 / 2)Mfsとする。

[0039] The interference signal acquisition unit 16 acquires an interference signal between the post-irradiation signal comb and the local comb. Because the predetermined difference frequency Δf is relatively small, beats occur between the post-irradiation signal comb and the local comb. The interference signal acquisition unit 16 is, for example, an optical coupler, and the post-irradiation signal comb and the local comb are provided to the interference signal acquisition unit 16 via a polarization-maintaining fiber and an optical attenuator.

[0040] The interference signal can be said to be the waveform of the electromagnetic wave obtained by the pump-probe method after irradiation.

[0041] 2 is a diagram showing the waveform of an interference signal, where the vertical axis of FIG. 2 represents the signal (e.g., expressed as voltage [V]) and the horizontal axis represents time (e.g., milliseconds).

[0042] The post-irradiation signal comb (post-irradiation electromagnetic waves) has a response component from the measurement object, a background component corresponding to the pre-irradiation signal comb (pre-irradiation electromagnetic waves), and a non-signal component that is neither a background component nor a response component.

[0043] In the waveform of an interference signal, the portion A where the signal is relatively large corresponds to the background component. The portion B where the signal is relatively small immediately after the background component A corresponds to the response component. The response component B is a free induction decay (FID) signal emitted by the measurement object excited by an optical field. The background component A and the response component B appear repeatedly, but a no-signal component X that is neither background component A nor response component B appears between the response component B and the next background component A that appears. Note that a portion of the no-signal component is called C. However, the portion of the no-signal component C appears immediately before the background component A.

[0044] The first frequency spectrum acquisition unit 18a acquires the frequency spectrum of a first signal including a background component A and a response component B in the post-irradiation electromagnetic wave. The second frequency spectrum acquisition unit 18b acquires the frequency spectrum of a second signal including the background component A in the post-irradiation electromagnetic wave. The second signal further includes a portion C of the no-signal component. The time length of the second signal is equal to or longer than the time length of the first signal. However, since it is preferable that the time length of the first signal and the time length of the second signal are equal, the following description will be given assuming that they are equal. The first frequency spectrum acquisition unit 18a and the second frequency spectrum acquisition unit 18b acquire frequency spectra by integrating the interference signals and performing a Fourier transform.

[0045] 3A and 3B are diagrams showing the frequency spectrum of the first signal acquired by the first frequency spectrum acquisition unit 18a (FIG. 3A) and the frequency spectrum of the second signal acquired by the second frequency spectrum acquisition unit 18b (FIG. 3B). Note that the vertical axis of FIG. 3 represents signal strength [dB], and the horizontal axis represents frequency [Hz].

[0046] 3(a), the frequency spectrum of the first signal is the frequency spectrum of the post-irradiation electromagnetic wave, and includes a component (so-called baseline) BL that is not dependent on the measurement object and a component (absorption line) AL that is dependent on the measurement object. Because the baseline BL is a curve, the depth of the absorption line AL cannot be accurately determined.

[0047] Referring to Figure 3(b), the frequency spectrum of the second signal is the frequency spectrum of the post-irradiation electromagnetic wave that includes a component (so-called baseline) BL that is not dependent on the object to be measured, but does not include a component (absorption line) AL that is dependent on the object to be measured.

[0048] The subtraction unit 19 subtracts the frequency spectrum of the second signal (see FIG. 3(b)) from the frequency spectrum of the first signal (see FIG. 3(a)).

[0049] 4 is a diagram showing the output of the subtraction unit 19. The baseline BL is roughly a straight line with a signal intensity of 0, and the depth of the absorption line AL can be accurately determined.

[0050] Next, the operation of the embodiment of the present invention will be described.

[0051] When the pre-irradiation signal comb is irradiated from the signal comb generator 12a to the object (gas) to be irradiated in the DUT (gas cell) 2, the pre-irradiation signal comb passes through the DUT 2, and a post-irradiation signal comb is obtained.

[0052] The post-irradiation signal comb is applied to a band-pass filter 14 , and the passed components are applied to an interference signal acquisition unit 16 .

[0053] Furthermore, the local comb is provided to the interference signal acquisition unit 16 from the local comb generation unit 12b.

[0054] An interference signal between the post-irradiation signal comb (components that have passed through the bandpass filter 14) and the local comb is acquired by the interference signal acquisition unit 16. From the acquisition result of the interference signal acquisition unit 16, the frequency spectrum of the first signal (see FIG. 3(a), with absorption line AL) is measured by the first frequency spectrum acquisition unit 18a, and the frequency spectrum of the second signal (see FIG. 3(b), without absorption line AL) is measured by the second frequency spectrum acquisition unit 18b.

[0055] The frequency spectrum of the second signal (see FIG. 3(b)) is subtracted from the frequency spectrum of the first signal (see FIG. 3(a)) by a subtraction unit 19 (see FIG. 4). According to the subtraction result of the subtraction unit 19 (see FIG. 4), the baseline BL is roughly a straight line with a signal intensity of 0, so the depth of the absorption line AL can be accurately determined. From the depth of this absorption line AL, the concentration of the object to be measured can be derived using the Beer-Lambert law.

[0056] According to the embodiment of the present invention, there is no need to prepare a reference path, and there is also no need to approximate the baseline for each narrow frequency range, so that the baseline can be easily obtained.

[0057] Furthermore, since the time length (A+B) of the first signal is equal to the time length (C+A) of the second signal, the number of Fourier transform points can be increased when acquiring the second signal, thereby improving the accuracy of acquiring the baseline BL.

[0058] The following various modifications of the embodiment of the present invention are possible.

[0059] <Variation 1> For example, it is possible to prevent the second signal from including the portion of the no-signal component C. In this case, the accuracy of obtaining the baseline BL decreases, but it does not mean that the baseline BL cannot be obtained.

[0060] <Variation 2> The first signal may further include a portion C of the no-signal component.

[0061] <Variation 3> The object to be irradiated may be a liquid or a solid. For example, the presence or absence of the measurement object is measured. For example, when the object to be irradiated is a solid, FTIR is used to measure the absorption of OH groups (1.4 um band) of the optical fiber. When the object to be irradiated is a liquid, FTIR is used to determine whether water is contained or not based on the presence or absence of OH group absorption.

[0062] <Variation 4> Instead of dual-comb spectroscopy, terahertz time-domain spectroscopy may be used to acquire the waveform of the post-irradiation electromagnetic wave. In this case, the signal comb generator 12a and the local comb generator 12b are each replaced with a terahertz generator (however, each has a different repetition frequency), and the interference signal acquirer 16 is replaced with a terahertz detector.

[0063] Alternatively, the signal comb generator 12a and the local comb generator 12b may be replaced with terahertz generators with the same repetition rate, and the interference signal acquirer 16 may be replaced with a terahertz detector. In this case, a device capable of sweeping the delay time must be placed between the local comb generator 12b replaced with a terahertz generator and the interference signal acquirer 16 replaced with a terahertz detector.

[0064] <Variation 5> Instead of light or terahertz waves, RF or magnetism may be irradiated onto the DUT 2.

[0065] The above embodiment can be realized as follows: A computer equipped with a CPU, a hard disk, and a media (USB memory, CD-ROM, etc.) reader reads a medium on which a program for implementing each of the above components, such as first frequency spectrum acquisition unit 18a, second frequency spectrum acquisition unit 18b, and subtraction unit 19, is recorded, and the program is installed on the hard disk. The above functions can also be realized in this manner. [Explanation of symbols]

[0066] 1 Electromagnetic wave measuring device 2 DUT (gas cell) 12a Signal comb generation unit 12b Local comb generator 14 Bandpass Filter 16 Interference signal acquisition unit 18a First frequency spectrum acquisition unit 18b Second frequency spectrum acquisition unit 19 Subtraction section A Background component B response component X No signal component C Part of the non-signal component X

Claims

1. An electromagnetic wave measuring device for measuring a measurement object based on a post-irradiation electromagnetic wave obtained by irradiating a pre-irradiation electromagnetic wave to an irradiation object having a measurement object, the post-irradiation electromagnetic wave has a response component from the measurement object and a background component corresponding to the pre-irradiation electromagnetic wave, The electromagnetic wave measuring device, a first frequency spectrum acquisition unit that acquires a frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave; a second frequency spectrum acquisition unit that acquires a frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave; a subtraction unit that subtracts a frequency spectrum of the second signal from a frequency spectrum of the first signal; An electromagnetic wave measuring device comprising:

2. 2. The electromagnetic wave measuring device according to claim 1, the post-irradiation electromagnetic wave further has a non-signal component which is neither the background component nor the response component, the second signal further comprises at least a portion of the non-signal component; Electromagnetic wave measuring device.

3. 3. The electromagnetic wave measuring device according to claim 2, The time length of the first signal is equal to the time length of the second signal. Electromagnetic wave measuring device.

4. 2. The electromagnetic wave measuring device according to claim 1, the post-irradiation electromagnetic wave further has a non-signal component which is neither the background component nor the response component, the first signal further comprises at least a portion of the non-signal component; Electromagnetic wave measuring device.

5. 5. The electromagnetic wave measuring device according to claim 1, The waveform of the electromagnetic wave after irradiation is obtained by dual comb spectroscopy; Electromagnetic wave measuring device.

6. 5. The electromagnetic wave measuring device according to claim 1, The waveform of the electromagnetic wave after irradiation is obtained by terahertz time domain spectroscopy; Electromagnetic wave measuring device.

7. 5. The electromagnetic wave measuring device according to claim 1, The waveform of the electromagnetic wave after irradiation is obtained by a pump-probe method; Electromagnetic wave measuring device.

8. 5. The electromagnetic wave measuring device according to claim 1, the response component is a free induction decay signal; Electromagnetic wave measuring device.

9. 5. The electromagnetic wave measuring device according to claim 1, The electromagnetic wave measuring device, wherein the irradiated object is a gas.

10. 10. The electromagnetic wave measuring device according to claim 9, The electromagnetic wave measuring device, wherein the object to be irradiated is accommodated in a gas cell.

11. The electromagnetic wave measuring device according to claim 10, An electromagnetic wave measuring device for measuring the concentration of the object to be measured.

12. 5. The electromagnetic wave measuring device according to claim 1, The electromagnetic wave measuring device, wherein the irradiated object is a liquid or a solid.

13. The electromagnetic wave measuring device according to claim 12, An electromagnetic wave measuring device that measures the presence or absence of the measurement object.

14. An electromagnetic wave measurement method for measuring a measurement object based on a post-irradiation electromagnetic wave obtained by irradiating a pre-irradiation electromagnetic wave to an irradiation object having a measurement object, comprising: the post-irradiation electromagnetic wave has a response component from the measurement object and a background component corresponding to the pre-irradiation electromagnetic wave, The electromagnetic wave measuring method comprises: a first frequency spectrum acquisition step of acquiring a frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave; a second frequency spectrum acquisition step of acquiring a frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave; a subtraction step of subtracting the frequency spectrum of the second signal from the frequency spectrum of the first signal; An electromagnetic wave measuring method comprising:

15. A program for causing a computer to execute an electromagnetic wave measurement process for measuring a measurement target based on a post-irradiation electromagnetic wave obtained by irradiating a pre-irradiation electromagnetic wave to an irradiation target having a measurement target, the post-irradiation electromagnetic wave has a response component from the measurement object and a background component corresponding to the pre-irradiation electromagnetic wave, The electromagnetic wave measurement process includes: a first frequency spectrum acquisition step of acquiring a frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave; a second frequency spectrum acquisition step of acquiring a frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave; a subtraction step of subtracting the frequency spectrum of the second signal from the frequency spectrum of the first signal; A program with.

16. A computer-readable recording medium having a program recorded thereon for causing a computer to execute an electromagnetic wave measurement process for measuring a measurement target based on a post-irradiation electromagnetic wave obtained by irradiating a pre-irradiation electromagnetic wave to an irradiation target having a measurement target, the post-irradiation electromagnetic wave has a response component from the measurement object and a background component corresponding to the pre-irradiation electromagnetic wave, The electromagnetic wave measurement process includes: a first frequency spectrum acquisition step of acquiring a frequency spectrum of a first signal including the background component and the response component in the post-irradiation electromagnetic wave; a second frequency spectrum acquisition step of acquiring a frequency spectrum of a second signal including the background component in the post-irradiation electromagnetic wave; a subtraction step of subtracting the frequency spectrum of the second signal from the frequency spectrum of the first signal; A recording medium comprising:

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