Spectroscopic apparatus, spectroscopic apparatus calibration method, and spectroscopic method

Abstract

To provide a spectroscopic apparatus capable of compensating for a decrease in length measurement precision and generating a high-precision spectral pattern even when two light reflection surfaces of a moving mirror have poor parallelism, a spectroscopic method, and a spectroscopic apparatus calibration method for calibrating the spectroscopic apparatus.SOLUTION: A spectroscopic apparatus comprises an analysis optical system, a length measuring optical system, and a calculation device, and performs spectroscopic analysis of a sample. The analysis optical system includes: a moving mirror that has a first reflection surface and a second reflection surface, the moving mirror configured to be translated; a gas cell that encapsulates gas and adds a light absorption signal to analysis light; and a first light receiving element that receives the analysis light containing a sample derived signal, a first modulation signal, and the light absorption signal. The length measuring optical system includes a length measuring section that acquires a displacement signal corresponding to a position of the moving mirror from laser light reflected off the second reflection surface. The calculation device includes a moving mirror position calculation section, a light intensity calculation section, a Fourier transform section, and a moving mirror position correction section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spectroscopic device, a method for calibrating a spectroscopic device, and a spectroscopic method. [Background technology]

[0002] Patent Document 1 discloses an optical module used in spectroscopic analysis, which acquires spectral information about light emitted or absorbed by a sample and analyzes the components of the sample based on that information. This optical module includes a mirror unit, a beam splitter unit, a light input unit, a first photodetector, a second light source, and a second photodetector. The mirror unit includes a movable mirror that moves in a predetermined direction and a fixed mirror that is fixed in position. In this optical module, the beam splitter unit, the movable mirror, and the fixed mirror form an interference optical system into which measurement light and laser light are respectively incident.

[0003] The measurement light incident from the first light source through the measurement object passes through the light incident section and is split in the beam splitter unit. A portion of the split measurement light is reflected by the movable mirror and returns to the beam splitter unit. The remaining portion of the split measurement light is reflected by the fixed mirror and returns to the beam splitter unit. The portion of the measurement light that returned to the beam splitter unit and the remaining portion are detected by the first photodetector as interference light.

[0004] Meanwhile, the laser light emitted from the second light source is split by the beam splitter unit. A portion of the split laser light is reflected by the movable mirror and returns to the beam splitter unit. The remaining portion of the split laser light is reflected by the fixed mirror and returns to the beam splitter unit. The portion of the laser light that returned to the beam splitter unit and the remaining portion are detected by the second photodetector as interference light.

[0005] In such an optical module, the position of the movable mirror is measured based on the detection result of the interference light of the laser light. Then, spectroscopic analysis of the measurement object is possible based on the measurement result of the position of the movable mirror and the detection result of the interference light of the measurement light. Specifically, a waveform called an interferogram is obtained by determining the intensity of the measurement light at each position of the movable mirror. The spectral pattern of the measurement object can be determined by Fourier transforming this interferogram. Therefore, the optical module described in Patent Document 1 is used in an FTIR (Fourier transform infrared spectroscopic analyzer). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 009404 Summary of the Invention [Problem to be solved by the invention]

[0007] In Fourier transform spectroscopic analyzers, the measurement accuracy of the movable mirror position is directly linked to the accuracy of the wavenumber axis (wavelength axis) of the spectral pattern. Therefore, studies are being conducted to measure the movable mirror position with high precision using a length measurement technology using laser light. As part of this technology, the use of a movable mirror with two light-reflecting surfaces that are reversed to each other is being considered. In order to accurately measure the change in the optical path length of the measurement light using laser light, it is necessary to sufficiently increase the parallelism between the light-reflecting surface that reflects the measurement light and the light-reflecting surface that reflects the laser light.

[0008] However, it is not easy to achieve high parallelism between the two reflecting surfaces, and poor parallelism can lead to measurement errors, which can reduce the accuracy of the wavenumber axis (wavelength axis) of the spectrum pattern obtained for the measurement target.

[0009] Therefore, the challenge is to realize a spectroscopic device that can compensate for the decrease in measurement accuracy and generate highly accurate spectral patterns even when the parallelism of the two light-reflecting surfaces of the movable mirror is reduced. [Means for solving the problem]

[0010] A spectroscopic device according to an application example of the present invention includes: A spectroscopic device that performs spectroscopic analysis of a sample, the spectroscopic device comprising an analytical optical system, a length measurement optical system, and a calculation device, The analytical optical system includes: a movable mirror that is driven to move in translation, the movable mirror having a first reflecting surface that reflects the analytical light emitted from a first light source and adds a first modulation signal to the analytical light, and a second reflecting surface that is located on the opposite side to the first reflecting surface; a gas cell in which a gas that absorbs light of a predetermined wavelength is sealed, and which adds a light absorption signal to the analytical light when the analytical light is incident thereon; a first light-receiving element that receives the analytical light, which includes a sample-derived signal generated by the interaction between the analytical light and the sample, the first modulated signal, and the light absorption signal, and outputs a first received light signal; Equipped with The length measurement optical system includes: a second light source that emits laser light; a length measuring unit that irradiates the laser light onto the second reflecting surface and acquires a displacement signal corresponding to a position of the movable mirror from the laser light reflected by the second reflecting surface; Equipped with The computing device a moving mirror position calculation unit that generates a moving mirror position signal based on the displacement signal; a light intensity calculation unit that generates a waveform representing the intensity of the first light receiving signal at each position of the movable mirror based on the first light receiving signal and the movable mirror position signal; a Fourier transform unit that performs a Fourier transform on the waveform to generate a spectral pattern including a peak due to the optical absorption signal; a moving mirror position correcting unit that calculates a correction value for correcting the moving mirror position signal based on the position of the peak; Equipped with.

[0011] A method for calibrating a spectroscopic device according to an application example of the present invention includes: A method for calibrating a spectroscopic device that performs spectroscopic analysis of a sample, comprising: In a spectroscopic device according to an application example of the present invention, after placing the gas cell on an optical path of the analytical light, the spectroscopic device acquires the displacement signal and measures the position of the movable mirror; a step of irradiating the analytical light to the gas cell while changing the position of the movable mirror, causing the first light receiving element to receive the analytical light emitted from the gas cell, and outputting the first light receiving signal derived from the gas cell; generating a waveform indicating the intensity of the first light receiving signal derived from the gas cell at each position of the movable mirror based on measurements of the first light receiving signal derived from the gas cell and the position of the movable mirror; performing a Fourier transform on the waveform from the gas cell to generate a spectral pattern including peaks due to the optical absorption signal; calculating a correction value for correcting the measurement value of the position of the movable mirror based on a difference between the wavelength of the peak and the fundamental wavelength of the gas cell; It has.

[0012] A spectroscopic method according to an application example of the present invention includes: Executing a method for calibrating a spectroscopic device according to an application example of the present invention; in the spectroscopic device, after placing the sample on an optical path of the analytical light, acquiring a spectral pattern including information derived from the sample, and correcting the spectral pattern including information derived from the sample based on the correction value; It has. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram showing a spectroscopic device according to a first embodiment. [Figure 2] 2 is a cross-sectional view showing an example of the configuration of the moving mirror in FIG. 1. [Figure 3] 2 is a cross-sectional view showing an example of the configuration of the moving mirror in FIG. 1. [Figure 4] 2 is a schematic diagram showing the main parts of the analytical optical system, the length measurement optical system, the signal generating unit, and the arithmetic unit of FIG. 1. FIG. [Figure 5] 2 is a diagram showing an example of a first received light signal and a second received light signal acquired by the spectroscopic device shown in FIG. 1. FIG. [Figure 6] FIG. 10 is a diagram showing an example of an interferogram. [Figure 7] FIG. 6 is a partial enlarged view of the second received light signal shown in FIG. 5. [Figure 8] This is an energy level diagram showing the hyperfine structure of the Cs(D1) line of the cesium atom. [Figure 9] The absorption spectrum of the Cs (D1) line shown in FIG. 8. [Figure 10] 5 is an example of a spectral pattern obtained by the spectrometer shown in FIG. 4. [Figure 11] 4 is a flowchart for explaining a spectroscopic method including a calibration method for the spectroscopic device according to the first embodiment. [Figure 12] FIG. 10 is a schematic diagram showing the configuration of a spectroscopic device according to a second embodiment. [Figure 13] FIG. 10 is a schematic diagram showing the configuration of a spectroscopic device according to a third embodiment. [Figure 14] 14 is a schematic diagram showing the main parts of the analytical optical system, the length measurement optical system, the signal generating unit, and the arithmetic unit in FIG. 13. FIG. [Figure 15] 14 is a diagram showing an example of a first light receiving signal and a movable mirror position signal acquired by the spectroscopic device shown in FIG. 13. FIG. [Figure 16] 10 is a graph showing the relationship between the measurement interval of the position of the movable mirror and the maximum measured wave number and the minimum measured wavelength in the spectrum pattern. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spectroscopic device and a method for calibrating a spectroscopic device according to the present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0015] 1. First embodiment First, a spectroscopic device and a method for calibrating the spectroscopic device according to the first embodiment will be described. FIG. 1 is a schematic diagram showing the configuration of a spectroscopic device 100 according to the first embodiment.

[0016] 1.1.Spectroscopic device In the spectroscopic device 100 shown in Fig. 1, analytical light L1 emitted from a first light source 51 is irradiated onto a sample 9, which is an object to be inspected. The analytical light L1 emitted from the sample 9 is passed through a Michelson interference optical system, and changes in the intensity of the obtained interference light are detected. An interferogram is obtained by performing a Fourier transform on the obtained interferogram to generate a spectral pattern (spectral information) containing information derived from the sample 9. By selecting the wavelength of the analytical light L1, the spectroscopic device 100 shown in Fig. 1 can be applied to, for example, Fourier-transform infrared spectroscopy (FT-IR), Fourier-near-infrared spectroscopy (FT-NIR), Fourier-visible spectroscopy (FT-VIS), Fourier-ultraviolet spectroscopy (FT-UV), and Fourier-terahertz spectroscopy (FT-THz), etc., on the sample 9.

[0017] The spectroscopic instrument 100 includes an optical device 1, a signal generating unit 8, and a computing unit . Of these, the optical device 1 includes an analytical optical system 3 and a length measurement optical system 4, as shown in FIG.

[0018] The analytical optical system 3 irradiates the sample 9 with analytical light L1, and splits and mixes the analytical light L1 to generate interference while changing the optical path length of the analytical light L1 so that a sample-derived signal originating from the sample 9 can be extracted from the analytical light L1. The length measurement optical system 4 uses laser light, length measurement light L2, to measure changes in the optical path length of the analytical light L1.

[0019] The signal generating unit 8 has a function of outputting a reference signal Ss to the arithmetic unit 7, and may be a function generator, which will be described later. The arithmetic unit 7 has a function of calculating a waveform representing the intensity of the interference light relative to the optical path length, i.e., the above-mentioned interferogram, based on a signal representing the intensity of the interference light output from the analytical optical system 3 and a signal representing the change in the optical path length output from the length measurement optical system 4. The arithmetic unit 7 also has a function of performing a Fourier transform on the interferogram to obtain a spectral pattern.

[0020] 1.2.Optical Devices Next, the optical device 1 will be described. As described above, the optical device 1 includes the analytical optical system 3 and the length measurement optical system 4.

[0021] 1.2.1.Analysis optical system The analytical optical system 3 includes a Michelson interference optical system, which includes a first light source 51, a gas cell 6, a beam splitter 32, a movable mirror 33, a fixed mirror 34, a condenser lens 35, and a first light-receiving element 36. Note that the analytical optical system 3 may omit some of these optical elements, may include optical elements other than these, or may replace these optical elements with other optical elements having equivalent functions.

[0022] The first light source 51 is a light source that emits, for example, white light, i.e., light comprising a wide range of wavelengths, as the analytical light L1. The wavelength range of the analytical light L1, i.e., the type of the first light source 51, is appropriately selected depending on the purpose of the spectroscopic analysis to be performed on the sample 9. When infrared spectroscopic analysis is performed, examples of the first light source 51 include a halogen lamp, an infrared lamp, a tungsten lamp, and a blackbody radiation lamp. When visible light spectroscopic analysis is performed, examples of the first light source 51 include a halogen lamp. When ultraviolet spectroscopic analysis is performed, examples of the first light source 51 include a deuterium lamp and a UV-LED (ultraviolet light emitting diode).

[0023] By selecting a wavelength of the analytical light L1 that is equal to or greater than 100 nm and less than 760 nm, the spectroscopic device 100 can perform ultraviolet spectroscopic analysis or visible spectroscopic analysis. By selecting a wavelength of the analytical light L1 that is equal to or greater than 760 nm and less than 20 μm, the spectroscopic device 100 can perform infrared spectroscopic analysis or near-infrared spectroscopic analysis. Furthermore, by selecting a wavelength of the analytical light L1 that is equal to or greater than 30 μm and less than 3 mm, the spectroscopic device 100 can perform terahertz wave spectroscopic analysis.

[0024] The first light source 51 may be provided externally to the spectrometer 100. In this case, it is sufficient that the analytical light L1 emitted from the externally provided first light source 51 is introduced into the spectrometer 100. On the other hand, by providing the spectrometer 100 with the first light source 51 as in this embodiment, the alignment accuracy between the first light source 51 and the beam splitter 32 can be particularly improved, and loss of analytical light L1 due to misalignment can be minimized.

[0025] The analytical light L1 is collimated using a lens, concave mirror, or the like (not shown) and then enters the gas cell 6. The gas cell 6 is filled with a gas that absorbs light of a specific wavelength. When the analytical light L1 enters the gas cell 6, a light absorption signal is added to the analytical light L1. The light absorption signal is the absorption of light of a specific wavelength by the gas. The gas cell 6 will be described in detail later.

[0026] The analytical light L1 transmitted through the gas cell 6 is incident on the beam splitter 32. The beam splitter 32 is a non-polarizing beam splitter that splits the analytical light L1 into two analytical lights L1a and L1b. Specifically, the beam splitter 32 has the function of splitting the analytical light L1 into two by reflecting a portion of the analytical light L1 toward a movable mirror 33 as analytical light L1a and transmitting the other portion of the analytical light L1 toward a fixed mirror 34 as analytical light L1b.

[0027] The beam splitter 32 may be of various types, such as a prism-type element (cube-type element) as shown in Fig. 1, a plate-type element, a stacked-type element, etc. When a plate-type beam splitter 32 is used, wavelength dispersion occurs between the analytical light L1a and the analytical light L1b, so a wavelength dispersion compensation plate may be disposed between the beam splitter 32 and the fixed mirror 34, if necessary.

[0028] The beam splitter 32 also transmits the analytical light L1a reflected by the movable mirror 33 toward the first light receiving element 36, and reflects the analytical light L1b reflected by the fixed mirror 34 toward the first light receiving element 36. Therefore, the beam splitter 32 has the function of mixing the split analytical light L1a and L1b.

[0029] 2 and 3 are cross-sectional views showing examples of the configuration of the movable mirror 33 in FIG. As shown in FIGS. 2 and 3, the movable mirror 33 has a first reflecting surface 331 and a second reflecting surface 332 which are opposite each other, and is driven to move in translation.

[0030] The movable mirror 33 moves in the incident direction of the analytical light L1a relative to the beam splitter 32 and reflects the analytical light L1a at the first reflecting surface 331. The analytical light L1a reflected by the movable mirror 33 changes in phase depending on the position of the movable mirror 33. As a result, the movable mirror 33 adds a first modulation signal to the analytical light L1a. The first modulation signal is a change in phase added to the analytical light L1a depending on the position of the movable mirror 33.

[0031] The position of the movable mirror 33 is measured by the distance measurement optical system 4, which will be described later. The measurement laser light emitted from the distance measurement optical system 4 is reflected by the second reflecting surface 332. The distance measurement optical system 4 measures the position of the movable mirror 33 based on the reflected laser light.

[0032] The moving mechanism (not shown) that moves the moving mirror 33 is not particularly limited, but examples thereof include a one-axis linear stage, a piezoelectric driving device, and a microactuator using MEMS (Micro Electro Mechanical Systems) technology.

[0033] As shown in Figures 2 and 3, the movable mirror 33 has a first reflecting surface 331 and a second reflecting surface 332 which are opposite surfaces to each other. Specifically, the movable mirror 33 shown in Figures 2 and 3 has a first mirror member 335 and a second mirror member 336. The first reflecting surface 331 is a surface 335a of the first mirror member 335, and the second reflecting surface 332 is a surface 336a of the second mirror member 336 which is attached to a back surface 335b of the first mirror member 335. The back surface 335b of the first mirror member 335 and the back surface 336b of the second mirror member 336 are bonded via an adhesive layer 337.

[0034] According to this configuration, the movable mirror 33 is configured by combining two mirror members, which makes it easy to increase the reflectance of both the first reflecting surface 331 and the second reflecting surface 332. This increases the S / N ratio (signal-to-noise ratio) of the interference light including the analytical light L1 reflected by the first reflecting surface 331. Similarly, the S / N ratio of the interference light including the length measurement laser light reflected by the second reflecting surface 332 is also increased.

[0035] On the other hand, first reflecting surface 331 and second reflecting surface 332 of movable mirror 33 are required to be parallel to each other. However, in reality, a decrease in parallelism occurs due to manufacturing errors of movable mirror 33, the accuracy of components, etc. Such a decrease in parallelism reduces the measurement accuracy of the position of movable mirror 33.

[0036] Specifically, when the first reflecting surface 331 and the second reflecting surface 332 are non-parallel to each other, the optical axis of the analytical light L1 incident on the first reflecting surface 331 and the optical axis of the measurement laser light incident on the second reflecting surface 332 become non-parallel. This causes an error between the actual movement distance of the movable mirror 33 and the measured value of the movement distance of the movable mirror 33 measured by the length measurement optical system 4. Such a measurement error causes a decrease in the accuracy of the spectral pattern acquired by the spectroscopic device 100.

[0037] FIG. 2 shows a schematic diagram of the decrease in parallelism due to manufacturing errors in the movable mirror 33. 2 has a variation in thickness. When the thickness of the adhesive layer 337 varies, the parallelism between the first reflecting surface 331 and the second reflecting surface 332 decreases. As a result, for example, the optical axis of the measurement light L2 is shifted by an angle θ with respect to the optical axis of the analysis light L1a.

[0038] 3, the dimensional accuracy of the first mirror member 335 and the second mirror member 336 themselves, specifically, the parallelism between the front surface 335a and the back surface 335b of the first mirror member 335 and the parallelism between the front surface 336a and the back surface 336b of the second mirror member 336, is reduced. As a result, for example, the optical axis of the measurement light L2 is shifted by an angle θ with respect to the optical axis of the analysis light L1a.

[0039] It is not easy to suppress manufacturing errors in the movable mirror 33 shown in FIG. 2 and to increase the dimensional accuracy of the members shown in FIG. 3, as this increases the manufacturing cost of the movable mirror 33.

[0040] Therefore, in this embodiment, the spectrometer 100 is calibrated using the gas cell 6 described later, and the decrease in the measurement accuracy of the position of the movable mirror 33 is compensated for.

[0041] The fixed mirror 34 is fixed in position relative to the beam splitter 32 and reflects the analytical light L1b. The analytical light L1b reflected by the fixed mirror 34 is mixed with the analytical light L1a by the beam splitter 32 and received as interference light by the first light receiving element 36. In the analytical optical system 3, an optical path difference occurs between the optical paths of the analytical light L1a and the analytical light L1b depending on the position of the movable mirror 33. Therefore, the intensity of the interference light changes depending on the position of the movable mirror 33.

[0042] The movable mirror 33 and the fixed mirror 34 may each be a flat mirror or a retroreflective optical element such as a corner cube mirror. The reflective surface of each mirror may be coated with a metal coating using a metal such as Al, Au, or Ag, or a dielectric multilayer film.

[0043] The condenser lens 35 condenses the interference light, that is, the mixed analytical light L1a and L1b, onto the first light receiving element 36.

[0044] The first light receiving element 36 receives the interference light and acquires its intensity. It then outputs a signal indicating the change in intensity over time as a first light receiving signal F(t). This first light receiving signal F(t) includes a sample-derived signal generated by the interaction between the analytical light L1 and the sample 9, the first modulation signal described above, and the light absorption signal described above. Among these, the sample-derived signal may be, for example, light absorption of a specific wavelength by the sample 9 when the analytical light L1 acts on the sample 9.

[0045] The first light receiving element 36 may be, for example, a photodiode, a phototransistor, etc. Among these, the photodiode may be, for example, an InGaAs-based photodiode, a Si-based photodiode, an avalanche photodiode, etc.

[0046] Furthermore, by using an element capable of acquiring a two-dimensional light intensity distribution as the first light receiving element 36, the spectroscopic device 100 can also be applied to, for example, a white light interferometry measuring device, an optical coherence tomography (OCT) imaging device, and the like.

[0047] 1.2.2. Length measurement optical system The distance measurement optical system 4 is a Michelson-type interference optical system, and includes a second light source 41 and a distance measurement unit 40. The distance measurement unit 40 acquires a displacement signal corresponding to the position of the movable mirror 33 by laser interference using measurement light L2 (laser light). This allows the position of the movable mirror 33 to be measured with high precision. The distance measurement unit 40 shown in FIG. 1 includes a second light splitting element 42, a light feedback unit 43, and a second light receiving element 45. Note that the distance measurement optical system 4 may omit some of these optical elements, may include optical elements other than these, or may replace these optical elements with other optical elements having equivalent functions.

[0048] A light source that emits light with a narrow spectral linewidth is preferably used as the second light source 41. Examples of the second light source 41 include gas lasers such as He-Ne lasers and Ar lasers, semiconductor laser elements such as DFB-LDs (Distributed Feedback Laser Diodes), FBG-LDs (Fiber Bragg Grating Laser Diodes), VCSELs (Vertical Cavity Surface Emitting Lasers), and FP-LDs (Fabry-Perot Laser Diodes), and crystal lasers such as YAG (Yttrium Aluminum Garnet).

[0049] It is particularly preferable that the second light source 41 is a semiconductor laser element, which allows the optical device 1 and the spectroscopic instrument 100 to be made smaller and lighter.

[0050] The second light dividing element 42 includes a beam splitter 422 , a half-wave plate 46 , a quarter-wave plate 47 , a quarter-wave plate 48 and an analyzer 49 .

[0051] Beam splitter 422 is a polarizing beam splitter that transmits P-polarized light and reflects S-polarized light. Half-wave plate 46 is disposed with its optical axis rotated with respect to the polarization axis of measurement light L2. As a result, measurement light L2 becomes linearly polarized light containing P-polarized light and S-polarized light by passing through half-wave plate 46, and is then split by beam splitter 422 into two, P-polarized light and S-polarized light.

[0052] The measurement light L2a, which is S-polarized light, is converted into circularly polarized light by the quarter-wave plate 48 and enters the light feedback unit 43. The light feedback unit 43 reflects the measurement light L2a to return it to the beam splitter 422. At this time, the measurement light L2a is converted into P-polarized light by the quarter-wave plate 48.

[0053] On the other hand, measurement light L2b, which is P-polarized light, is converted into circularly polarized light by the quarter-wave plate 47 and enters the movable mirror 33. The movable mirror 33 reflects measurement light L2b. As a result, the phase of measurement light L2b changes depending on the position of the movable mirror 33. As a result, the movable mirror 33 adds a displacement signal to measurement light L2b. Measurement light L2b reflected by the movable mirror 33 returns to the beam splitter 422. At this time, measurement light L2b is converted into S-polarized light by the quarter-wave plate 47.

[0054] The beam splitter 422 also transmits the measurement light L2a returned from the light feedback unit 43 toward the second light receiving element 45, and reflects the measurement light L2b reflected by the movable mirror 33 toward the second light receiving element 45. Therefore, the beam splitter 422 has the function of mixing the split measurement light L2a and L2b. The mixed measurement light L2a and L2b pass through the analyzer 49 and enter the second light receiving element 45.

[0055] Note that a non-polarizing beam splitter may be used instead of a polarizing beam splitter for the beam splitter 422. In this case, a wave plate or the like is not required, and the number of parts can be reduced, thereby enabling the optical device 1 to be made smaller.

[0056] The light feedback section 43 includes a light reflector 442, which reflects the light that has been reflected by the beam splitter 422 and is incident thereon, and returns the light to the beam splitter 422. The light reflector 442 is formed of, for example, a mirror. This simplifies the configuration of the light feedback section 43, which can contribute to miniaturization of the optical device 1.

[0057] The second light receiving element 45 receives the mixed measurement light L2a, L2b as interference light and acquires its intensity. It then outputs a signal indicating the change in intensity over time as a second received light signal S2. This second received light signal S2 includes a displacement signal of the movable mirror 33. The displacement signal is a phase change added to the measurement light L2b depending on the position of the movable mirror 33. In this way, the measurement unit 40 acquires a displacement signal indicating the position of the movable mirror 33.

[0058] The second light receiving element 45 may be, for example, a photodiode or a phototransistor.

[0059] The analytical optical system 3 and the length measurement optical system 4 have been described above, but of the optical elements included in these optical systems, those that require light to be incident thereon are preferably subjected to anti-reflection treatment, which can increase the S / N ratio of the first received light signal F(t) and the second received light signal S2.

[0060] 1.3.Signal Generation Section FIG. 4 is a schematic diagram showing the main parts of the analytical optical system 3, the length measurement optical system 4, the signal generating unit 8, and the computing device 7 of FIG.

[0061] 4 generates a periodic signal and outputs it as a reference signal Ss. Examples of the signal generator 8 include a function generator, a signal generator, and a numerically controlled signal generator. A calculation device 7 (described later) generates a moving mirror position signal X(t) based on the reference signal Ss and the displacement signal described above.

[0062] 1.4. Arithmetic device The calculation device 7 shown in Fig. 4 has a moving mirror position calculation unit 72, a light intensity calculation unit 74, a Fourier transform unit 76, and a moving mirror position correction unit 78. The functions performed by these functional units are realized by hardware including, for example, a processor, memory, an external interface, an input unit, a display unit, etc. Specifically, the functions are realized by the processor reading and executing a program stored in memory. These components are capable of communicating with each other via an external bus.

[0063] Examples of processors include a CPU (Central Processing Unit), a DSP (Digital Signal Processor), etc. Instead of using these processors to execute software, a system in which an FPGA (Field-Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), etc., realizes the above-mentioned functions may be adopted.

[0064] Examples of memory include HDD (Hard Disk Drive), SSD (Solid State Drive), EEPROM (Electrically Erasable Programmable Read-Only Memory), ROM (Read-Only Memory), and RAM (Random Access Memory).

[0065] Examples of the external interface include a digital input / output port such as a USB (Universal Serial Bus), an Ethernet (registered trademark) port, and the like.

[0066] Examples of the input unit include various input devices such as a keyboard, a mouse, a touch panel, a touch pad, etc. Examples of the display unit include a liquid crystal display panel, an organic EL (Electro Luminescence) display panel, etc. The input unit and the display unit may be provided as needed, and may be omitted.

[0067] 1.4.1. Moving mirror position calculation unit The movable mirror position calculation unit 72 generates a movable mirror position signal X(t) from the second received light signal S2, which includes a displacement signal of the movable mirror 33, based on the reference signal Ss output from the signal generation unit 8. When the movable mirror 33 moves, the intensity of the interference light in the length measurement optical system 4 changes accordingly. In this case, the second received light signal S2 becomes, for example, a signal whose amplitude changes periodically depending on the interference conditions. The displacement of the movable mirror 33 can be calculated from the change in the amplitude of the second received light signal S2, and the movable mirror position signal X(t) is obtained.

[0068] 1.4.2. Light Intensity Calculation Unit The light intensity calculation unit 74 generates a waveform (interferogram F(x)) that represents the intensity of the interference light relative to the position of the movable mirror 33 based on the first light reception signal F(t) and the movable mirror position signal X(t).

[0069] As described above, the first received light signal F(t) includes a sample-derived signal, a first modulation signal, and a light absorption signal. The light intensity calculation unit 74 generates an interferogram F(x) based on the position of the movable mirror 33 determined from the movable mirror position signal X(t) and the intensity of the first received light signal F(t). The interferogram F(x) is expressed as a function of the optical path difference between the light reflected by the movable mirror 33 and the light reflected by the fixed mirror 34 in the analysis optical system 3, and the intensity of the interference light received by the first light receiving element 36 (the intensity of the first received light signal F(t)).

[0070] Fig. 5 is a diagram showing an example of the first received light signal F(t) and the second received light signal S2 acquired by the spectroscopic device 100 shown in Fig. 1. The horizontal axis of Fig. 5 represents time t, and the vertical axis represents the intensity of the interference light incident on the first light receiving element 36 or the intensity of the interference light incident on the second light receiving element 45.

[0071] Fig. 6 is a diagram showing an example of an interferogram F(x). The horizontal axis of Fig. 6 represents the optical path difference of the analytical optical system 3, and the vertical axis represents the intensity of the interference light. The optical path difference of the analytical optical system 3 is the difference between the optical path length between the beam splitter 32 and the movable mirror 33 and the optical path length between the beam splitter 32 and the fixed mirror 34. In Fig. 6, the origin of the horizontal axis is set to zero optical path difference.

[0072] FIG. 7 is a partially enlarged view of the second received light signal S2 shown in FIG. 5. The second received light signal S2 shown in FIG. 7 is a signal that oscillates at a predetermined period, and the point at which the amplitude is maximum is the characteristic point FP. The light intensity calculation unit 74 extracts the intensity of the first received light signal F(t) shown in FIG. 5 at the time of this characteristic point FP, thereby correlating the position of the movable mirror 33 with the intensity of the first received light signal F(t). This makes it possible to acquire digital data of the interferogram F(x). Note that in this case, since measurement is based on the shortest interval between the characteristic points FP, the shortest measurement interval for the position of the movable mirror 33 is ¼ of the wavelength λ of the measurement light L2.

[0073] 1.4.3.Fourier transform section The Fourier transform unit 76 performs a Fourier transform on the interferogram F(x), thereby generating a spectral pattern specific to the sample 9.

[0074] The spectral pattern reflects, as absorption peaks, signals originating from the sample 9 that are generated when the analytical light L1 acts on the sample 9. Based on this spectral pattern, the characteristics of the sample 9, such as the material, structure, and amount of components, can be analyzed.

[0075] 1.4.4. Moving mirror position correction unit The movable mirror position corrector 78 calculates a correction value for correcting the measured value of the movable mirror position using a method described below. This allows the displacement of the movable mirror 33 included in the movable mirror position signal X(t) to approach its true value. As a result, the accuracy of the wavenumber axis (wavelength axis) of the spectrum pattern finally obtained can be improved.

[0076] 1.5.Gas Cell Next, the gas cell 6 will be described. The gas cell 6 is filled with a gas that absorbs light of a predetermined wavelength. Examples of the gas that can be filled include alkali metals such as gaseous cesium and rubidium, halogens such as gaseous iodine, and rare gases such as krypton, as well as hydrogen cyanide and acetylene. These atoms or molecules absorb and emit light of a predetermined wavelength. The gas cell 6 may be provided with a temperature adjustment mechanism (not shown). This allows the vapor pressure of the gas to be sufficiently increased even when the gas cell 6 is made smaller. As a result, the gas cell 6 can be made smaller.

[0077] Table 1 below shows examples of combinations of gases (atoms or molecules) filled in the gas cell 6 and the wavelengths of light irradiated onto the gases.

[0078] [Table 1]

[0079] As shown in Table 1, the wavelength to be absorbed can be changed by selecting the gas to be filled in the gas cell 6. When selecting the gas, a gas whose absorbing wavelength overlaps with the emission spectrum of the first light source 51 is selected.

[0080] When the analytical light L1 is incident on the gas cell 6, the analytical light L1 is irradiated onto the gas sealed in the gas cell 6. As a result, the atoms and molecules that make up the gas transition from the ground state to a state with higher energy (excited state) according to the energy of the analytical light L1.

[0081] FIG. 8 is an energy level diagram showing the hyperfine structure of the Cs(D1) line of the cesium atom. As shown in Figure 8, the cesium atom has a ground state of 6S 1 / 2 The energy level is expressed as 6P as the excited level 1 / 2 and the energy level is represented by 6S. 1 / 2 and 6P 1 / 2 Each energy level of 6S has a hyperfine structure split into multiple energy levels. 1 / 2 has two ground levels, F=3 and F=4. 1 / 2 has two excited levels denoted F'=3 and F'=4.

[0082] A cesium atom in the ground level transitions to an excited level by absorbing, for example, the Cs(D1) line shown in FIG.

[0083] For example, a cesium atom in the ground level of F=4 transitions to an excited level of F'=3 by absorbing energy between levels indicated by arrow (1) in Figure 8. Also, by absorbing energy between levels indicated by arrow (2) in Figure 8, it transitions to an excited level of F'=4.

[0084] Also, a cesium atom in the ground level of F=3 transitions to an excited level of F'=3 by absorbing energy between levels indicated by arrow (3) in Figure 8. Also, by absorbing energy between levels indicated by arrow (4) in Figure 8, it transitions to an excited level of F'=4. The resonance wavelengths corresponding to the transitions indicated by the arrows (1) to (4) in FIG. 8 are shown in Table 2 below.

[0085] [Table 2]

[0086] Figure 9 shows the absorption spectrum AS1 of the Cs(D1) line shown in Figure 8. Four absorption peaks P1 to P4 are observed in the absorption spectrum AS1 shown in Figure 9. The frequencies of these absorption peaks P1 to P4 correspond to the four transition frequencies indicated by arrows (1) to (4) in Figure 8.

[0087] For example, when the analytical light L1 is incident on the gas cell 6 in which cesium atoms are sealed, the absorption spectrum AS1 shown in FIG.

[0088] FIG. 10 is an example of a spectral pattern SP1 obtained by the spectroscopic device 100 shown in FIG.

[0089] The spectral pattern SP1 shown in Figure 10 includes absorption peak X9 derived from sample 9 and absorption peaks XCsD1 and XCsD2 due to cesium atoms. Absorption peak X9 corresponds to the signal derived from the sample described above. Absorption peak XCsD1 is a peak due to absorption of the Cs(D1) line described above. Note that absorption peak XCsD1 shown in Figure 10 represents a state in which the four fine peaks shown in Table 2 are not resolved and appear as a single peak. Absorption peak XCsD2 is a peak due to absorption of the Cs(D2) line shown in Table 1, and also represents a state in which multiple fine peaks are not resolved and appear as a single peak. Absorption peaks XCsD1 and XCsD2 correspond to the optical absorption signals described above.

[0090] The wavelengths of the absorption peaks XCsD1 and XCsD2 included in the spectral pattern SP1 correspond to the energy between the levels described above, and therefore have extremely high accuracy and stability. Furthermore, fluctuations due to temperature changes are less than pm order. Therefore, the "true values ​​(fundamental wavelengths)" of the wavelengths of the absorption peaks XCsD1 and XCsD2 can be said to be known. Therefore, if there is a "wavelength deviation Δλ" between the measured wavelengths of the absorption peaks XCsD1 and XCsD2 included in the spectral pattern SP1, which is the analysis result, and the true values ​​(fundamental wavelengths), the wavelength deviation Δλ is likely to be caused by various errors inherent in the spectroscopic device 100.

[0091] Here, let us consider the effect of a measurement error when it occurs in the measurement value of the moving distance of the moving mirror 33 by the aforementioned length measurement optical system 4. For example, assume that when the true value L [mm] of the moving distance of the moving mirror 33 is measured, a measurement value L(1+σ) [mm] including an error σ is obtained. In this case, the error σ causes a deviation from the true wavelength value λ on the spectrum pattern SP1. This deviation can be expressed as σλ using the error σ. This error σ becomes the correction value for obtaining the corrected moving mirror position signal X(t).

[0092] As an example, let's assume that the hyperfine structure contained in the absorption peak XCsD1 shown in Figure 10 can be resolved, and consider the case where the measured wavelength of the hyperfine structure corresponding to absorption peak P1 in Figure 9 is 892.0000 nm. As shown in Table 2, the true value of the resonance wavelength of transition (1) is 894.6054 nm, so the wavelength shift Δλ is Δλ = 894.6054 - 892.0000 = 2.6054 [nm]. Then, since Δλ = σλ, 2.6054 = σ × 894.6054 is obtained. As a result, σ = 0.002912. If the moving mirror position signal before correction is X'(t), the moving mirror position signal after correction, X(t), can be calculated as X(t) = X'(t) / (1 + σ).

[0093] It should be noted that the error σ may be calculated from each of a plurality of absorption peaks, and then the correction may be performed based on the average value or other calculations. The method of calculating the correction value is not limited to the above.

[0094] The movable mirror position correction unit 78 of the calculation device 7 has the function of calculating a correction value for correcting the measured value of the position of the movable mirror 33 based on the difference between the actual measured value of the wavelength of the absorption peak XCsD1 (the actual measured value of the wavelength of the peak based on the optical absorption signal) and the true value of the wavelength of the absorption peak XCsD1 (the fundamental wavelength of the gas cell 6), and correcting the movable mirror position signal X(t) based on this correction.

[0095] Furthermore, in this embodiment, the gas cell 6 is disposed between the first light source 51 and the beam splitter 32. Therefore, when the analytical light L1 is irradiated onto the sample 9, the analytical light L1 is also always irradiated onto the gas cell 6. Therefore, in this embodiment, the absorption peak XCsD1 can be acquired in addition to the absorption peak X9 derived from the sample 9. As a result, the correction value can be calculated simultaneously with the acquisition of the spectral pattern SP1, allowing the spectroscopic instrument 100 to be calibrated in real time, enabling particularly highly accurate spectroscopic analysis.

[0096] Furthermore, because the energy between the levels of the atoms and molecules sealed in the gas cell 6 is extremely accurate and stable, the above-mentioned effect can be obtained even if the wavelength stability of the measurement light L2 emitted from the second light source 41 is low. Therefore, even if a small, inexpensive element such as a semiconductor laser element is used for the second light source 41, there is no need to provide additional equipment such as a light source temperature control system. This allows the optical device 1 to be made smaller, lighter, and consume less power and at lower costs.

[0097] The arrangement of the gas cell 6 is not limited to the above arrangement, as long as it is a position where the analytical light L1 can be incident. For example, the gas cell 6 may be arranged between the beam splitter 32 and the sample 9 shown in FIG. 1, or between the sample 9 and the condenser lens 35.

[0098] The arrangement of the sample 9 is not limited to the above. For example, the sample 9 may be arranged between the first light source 51 and the beam splitter 32 shown in Fig. 1. Furthermore, the spectroscopic device 100 may be configured to acquire a reflection spectrum instead of the above-described spectral pattern SP1, which is a transmission spectrum, by changing the arrangement of the sample 9.

[0099] 1.6.Spectroscopy method Next, a spectroscopic method including a method for calibrating the spectroscopic device according to the first embodiment will be described.

[0100] FIG. 11 is a flowchart for explaining a spectroscopic method including a method for calibrating the spectroscopic device according to the first embodiment.

[0101] The calibration method for a spectroscopic device shown in Fig. 11 includes a mirror position measurement step S102, an analytical light irradiation step S104, a waveform generation step S106, a Fourier transform step S108, and a correction value calculation step S110. The spectroscopic method shown in Fig. 11 also includes a step of executing this calibration method (calibration step S100) and a spectrum information correction step S112.

[0102] In the mirror position measurement step S102, measurement light L2 (laser light) is made incident on the length measurement unit 40 of the optical device 1 to start measuring the position of the movable mirror 33. As a result, acquisition of a displacement signal corresponding to the position of the movable mirror 33 starts.

[0103] In the analytical light irradiation step S104, the gas cell 6 and the sample 9 are placed on the optical path of the analytical light L1, and the analytical light is made incident on the gas cell 6 and the sample 9 while changing the position of the movable mirror 33. The analytical light L1 emitted from the gas cell 6 and the sample 9 is then received by the first light receiving element 36, and a first light receiving signal F(t) is output. Note that the analytical light L1 may be incident on the gas cell 6 and the analytical light L1 on the sample 9 simultaneously or at different times. In the spectroscopic instrument 100 shown in FIG. 1, these can be done simultaneously.

[0104] In waveform generation step S106, a movable mirror position signal X(t) is generated based on the displacement signal corresponding to the position of the movable mirror 33. Then, based on the first received light signal F(t) and the movable mirror position signal X(t) (position of the movable mirror 33), an interferogram F(x) (a waveform indicating the intensity of the first received light signal F(t) at each position of the movable mirror 33) originating from both the gas cell 6 and the sample 9 is generated.

[0105] In the Fourier transform step S108, the interferogram F(x) is subjected to a Fourier transform to generate a spectral pattern including an absorption peak X9 (a peak due to a signal originating from the sample) and an absorption peak XCsD1 (a peak due to a light absorption signal).

[0106] In the correction value calculation step S110, a correction value for correcting the measured value of the position of the movable mirror 33 is calculated based on the difference between the wavelength of the absorption peak XCsD1 and the fundamental wavelength of the gas cell 6. In other words, the correction value is calculated based on the position of the absorption peak XCsD1.

[0107] In the spectral information correction step S112, the spectral pattern including the absorption peak X9 is corrected based on the correction value.

[0108] According to the above-described method for calibrating a spectroscopic device, even if the parallelism between first reflecting surface 331 and second reflecting surface 332 of movable mirror 33 is reduced, it is possible to compensate for the reduction in the length measurement accuracy (length measurement precision) of the position of movable mirror 33. Therefore, according to the above-described spectroscopic method, by calibrating spectroscopic device 100, a highly accurate spectral pattern can be generated.

[0109] 2. Second embodiment Next, a spectroscopic device according to a second embodiment will be described.

[0110] FIG. 12 is a schematic diagram showing the configuration of a spectroscopic device 100 according to the second embodiment. The second embodiment will be described below, focusing on the differences from the first embodiment and omitting a description of similarities. Note that in Fig. 12, the same reference numerals are used to designate the same components as those in the first embodiment.

[0111] The spectroscopic instrument 100 shown in FIG. 12 is similar to the spectroscopic instrument 100 shown in FIG. 1 except that the configuration of the analytical optical system 3 is different.

[0112] The analytical optical system 3 shown in FIG. 12 includes a sample switching unit 61 disposed between the beam splitter 32 and the condenser lens 35. The sample switching unit 61 has an insertion / removal mechanism 63 for inserting and removing the sample 9 and the gas cell 6 in the optical path through which the analytical beams L1a and L1b pass. This allows for mutually exclusive switching between a state in which the sample 9 is placed on the optical path and a state in which the gas cell 6 is placed on the optical path. As a result, a function is realized that allows for flexible switching between a spectroscopic analysis mode in which spectroscopic analysis of the sample 9 is performed and a calibration mode in which the spectroscopic instrument 100 is calibrated using the gas cell 6. This allows for the spectroscopic instrument 100 to be automatically calibrated by executing the calibration mode as needed. Furthermore, in the spectroscopic analysis mode, the gas cell 6 is not present on the optical path, thereby suppressing light loss due to the gas cell 6.

[0113] In the second embodiment as described above, the same effects as in the first embodiment can be obtained. The sample switching unit 61 may be disposed between the first light source 51 and the beam splitter 32.

[0114] 12 may be omitted, and both the gas cell 6 and the sample 9 may be disposed between the beam splitter 32 and the first light receiving element 36. In this case, when the analytical light L1 is irradiated onto the sample 9, the analytical light L1 is also always irradiated onto the gas cell 6. Therefore, in this embodiment, the absorption peak XCsD1 can be acquired along with the absorption peak X9 derived from the sample 9. As a result, the correction value can be calculated simultaneously with the acquisition of the spectral pattern SP1, allowing the spectroscopic instrument 100 to be calibrated in real time, enabling particularly highly accurate spectroscopic analysis.

[0115] 3. Third embodiment Next, a spectroscopic device according to a third embodiment will be described.

[0116] Fig. 13 is a schematic diagram showing the configuration of a spectroscopic device 100 according to the third embodiment. Fig. 14 is a schematic diagram showing the main parts of the analytical optical system 3, the length measurement optical system 4, the signal generating unit 8, and the arithmetic unit 7 shown in Fig. 13.

[0117] The third embodiment will be described below, focusing on the differences from the first embodiment and omitting a description of similarities. Note that in Fig. 13, the same reference numerals are used to designate the same components as those in the first embodiment.

[0118] The optical feedback section 43 of the length measurement optical system 4 shown in Figure 13 is similar to the length measurement optical system 4 shown in Figure 1, except that it has an optical modulator 444 instead of the optical reflector 442 and the configuration of the signal generation section 8 is different.

[0119] The optical modulator 444 shown in Fig. 13 has a vibration element 446 and shifts the frequency of the measurement light L2a. An example of such an optical modulator 444 is the optical modulator disclosed in Japanese Patent Application Laid-Open No. 2022-38156. This publication lists a quartz AT vibrator as the vibration element. Alternatively, an SC-cut quartz vibrator, a tuning fork-type quartz vibrator, a quartz surface acoustic wave element, or the like may be used for the vibration element 446.

[0120] The signal generating unit 8 shown in FIG. 13 has a function of generating a drive signal Sd. The signal generating unit 8 shown in FIG. 13 includes an oscillator circuit 81. The oscillator circuit 81 uses a vibrating element 446 as a signal source to generate a highly accurate periodic signal. In the signal generating unit 8 shown in FIGS. 13 and 14, the vibrating element 446 is oscillated by the drive signal Sd, and the periodic signal generated by the oscillator circuit 81 is output as a reference signal Ss. In this manner, the second modulated signal added via the optical modulator 444 driven by the drive signal Sd and the reference signal Ss are affected by the same factors. Therefore, when the second received light signal S2 and the reference signal Ss are subjected to calculations in the calculation device 7, the effects of disturbances contained in both signals can be canceled out or reduced during the calculation process. As a result, the calculation device 7 can accurately determine the position of the movable mirror 33 even when subjected to disturbances. Furthermore, the spectroscopic device 100 can be made smaller, lighter, and consume less power.

[0121] An example of the oscillator circuit 81 is the oscillator circuit disclosed in Japanese Patent Application Laid-Open No. 2022-38156.

[0122] The movable mirror position calculation unit 72 shown in Figure 14 identifies the position of the movable mirror 33 by optical heterodyne interferometry and generates a movable mirror position signal X(t) based on the results. By providing the length measurement optical system 4 with an optical modulator 444, a second modulation signal can be added to the length measurement light L2a. In this way, when the length measurement light L2a and L2b are made to interfere with each other, phase information corresponding to the position of the movable mirror 33 can be obtained with higher accuracy from the obtained interference light. Then, the calculation device 7 can determine the position of the movable mirror 33 with high accuracy from the phase information.

[0123] 14 includes a pre-processing unit 722, a demodulation processing unit 724, and a moving mirror position signal output unit 726. The pre-processing unit 722 and the demodulation processing unit 724 may be, for example, the pre-processing unit and the demodulation unit disclosed in Japanese Patent Application Laid-Open No. 2022-38156.

[0124] The pre-processing unit 722 pre-processes the second received light signal S2 based on the reference signal Ss. The demodulation processing unit 724 demodulates the pre-processed signal output from the pre-processing unit 722 into a displacement signal corresponding to the position of the movable mirror 33 based on the reference signal Ss.

[0125] The movable mirror position signal output unit 726 generates and outputs a movable mirror position signal X(t) based on the displacement signal of the movable mirror 33 demodulated by the demodulation processing unit 724. The movable mirror position signal X(t) obtained in this manner captures the displacement of the movable mirror 33 at intervals sufficiently narrower than the wavelength of the measurement light L2. For example, when the wavelength of the measurement light L2 is several hundred nanometers, the position resolution of the movable mirror 33 indicated by the displacement signal can be achieved to be less than 10 nanometers. In contrast, in the first embodiment, the limit of the position resolution is one-quarter of the wavelength of the measurement light L2. Therefore, the light intensity calculation unit 74 can generate digital data of the interferogram F(x) at finer intervals than in the first embodiment.

[0126] Fig. 15 is a diagram showing an example of the first light receiving signal F(t) and the movable mirror position signal X(t) acquired by the spectroscopic device 100 shown in Fig. 13. The horizontal axis of Fig. 15 represents time t, and the vertical axis represents the intensity of the interference light incident on the first light receiving element 36 or the position of the movable mirror 33.

[0127] The movable mirror position signal X(t) shown in FIG. 15 is a result of continuously detecting changes in the position of the movable mirror 33, and is represented by a smooth curve, indicating that high position resolution has been achieved. Therefore, by generating an interferogram F(x) based on this signal, an interferogram F(x) with a larger number of data points can be obtained. A larger number of data points means that the sampling interval of the interferogram F(x) is short and the accuracy is high. Therefore, by using the interferogram F(x) obtained in this manner, a spectral pattern with high resolution can ultimately be obtained.

[0128] Furthermore, by shortening the sampling interval, it is possible to acquire a spectral pattern over a wider wavenumber range (wider wavelength range), that is, a spectral pattern over a wider band.

[0129] 16 is a graph showing the relationship between the measurement interval Δx of the position of the movable mirror 33 and the maximum measurement wavenumber and minimum measurement wavelength in the spectral pattern. As shown in FIG. 16, the smaller the measurement interval Δx, the larger the maximum measurement wavenumber and the shorter the minimum measurement wavelength. Therefore, by reducing the measurement interval Δx, it becomes possible to obtain a spectral pattern over a wider wavenumber range (wavelength range).

[0130] Note that the vibration element 446 may be a silicon vibrator, a ceramic vibrator, a piezoelectric element, or the like, in addition to the above-mentioned quartz crystal vibrator. Of these, the vibration element 446 is preferably a quartz crystal vibrator, a silicon vibrator, or a ceramic vibrator. Unlike other vibrators, such as piezoelectric elements, these vibrators utilize the mechanical resonance phenomenon, and therefore have a high Q value and can easily stabilize the natural frequency.

[0131] A silicon vibrator is a vibrator that includes a single-crystal silicon piece manufactured from a single-crystal silicon substrate using MEMS technology, and a piezoelectric film. MEMS (Micro Electro Mechanical Systems) stands for microelectromechanical systems. Examples of the shape of the single-crystal silicon piece include cantilever beam shapes such as two-legged tuning fork and three-legged tuning fork, and doubly supported beam shapes. The oscillation frequency of a silicon vibrator is, for example, about 1 kHz to several hundred MHz.

[0132] A ceramic vibrator is a vibrator that includes electrodes and piezoelectric ceramic pieces manufactured by baking and hardening piezoelectric ceramics. Examples of piezoelectric ceramics include lead zirconate titanate (PZT) and barium titanate (BTO). The oscillation frequency of a ceramic vibrator is, for example, from several hundred kHz to several tens of MHz.

[0133] The optical modulator 444 may also be an acousto-optic modulator (AOM), an electro-optic modulator (EOM), or the like. However, the optical modulator 444 having the vibration element 446 can be significantly reduced in volume and weight compared to an AOM or an EOM. This can contribute to making the spectroscopic device 100 smaller, lighter, and less power-consuming.

[0134] 7. Effects of the above embodiments The spectroscopic device 100 according to each of the above embodiments includes an analytical optical system 3, a length measurement optical system 4, and a computing device 7, and performs spectroscopic analysis of a sample 9.

[0135] The analytical optical system 3 includes a movable mirror 33, a gas cell 6, and a first light-receiving element 36. The movable mirror 33 reflects the analytical light L1 emitted from the first light source 51 and has a first reflecting surface 331 that adds a first modulation signal to the analytical light L1, and a second reflecting surface 332 located on the opposite side of the first reflecting surface 331, and is driven to move in translation. The gas cell 6 is filled with a gas that absorbs light of a predetermined wavelength, and adds a light absorption signal to the analytical light L1 when the analytical light L1 is incident on the gas cell 6. The first light-receiving element 36 receives the analytical light L1, which includes a sample-derived signal, a first modulation signal, and a light absorption signal generated by the interaction between the analytical light L1 and the sample 9, and outputs a first received light signal F(t).

[0136] The distance measurement optical system 4 includes a second light source 41 and a distance measurement unit 40. The second light source 41 emits distance measurement light L2, which is a laser beam. The distance measurement unit 40 irradiates the distance measurement light L2 onto the second reflecting surface 332 and acquires a displacement signal corresponding to the position of the movable mirror 33 from the distance measurement light L2 reflected by the second reflecting surface 332.

[0137] The calculation device 7 includes a moving mirror position calculation unit 72, a light intensity calculation unit 74, a Fourier transform unit 76, and a moving mirror position correction unit 78. The moving mirror position calculation unit 72 generates a moving mirror position signal X(t) based on the displacement signal acquired by the length measurement optical system 4. The light intensity calculation unit 74 generates an interferogram F(x) (a waveform representing the intensity of the first received light signal F(t) at each position of the moving mirror 33) based on the first received light signal F(t) and the moving mirror position signal X(t). The Fourier transform unit 76 performs a Fourier transform on the interferogram F(x) to generate a spectral pattern including peaks due to light absorption signals. The moving mirror position correction unit 78 calculates a correction value for correcting the moving mirror position signal X(t) based on the position of the peak due to the light absorption signal.

[0138] With this configuration, when measuring the position of movable mirror 33 using a displacement signal, the extremely high precision and stability of the energy between the levels of atoms and molecules sealed in gas cell 6 can be utilized to calculate a correction value for correcting the measurement value based on the light absorption signal derived from gas cell 6. In other words, a correction value for measuring the position of movable mirror 33 with high precision can be calculated. Therefore, even if the parallelism of the two light reflecting surfaces (first reflecting surface 331 and second reflecting surface 332) of movable mirror 33 is reduced, it is possible to compensate for the decrease in measurement precision. This makes it possible to realize spectroscopic device 100 that can generate highly accurate spectral patterns.

[0139] Furthermore, to obtain the above effects, there is no need to provide additional equipment such as a light source temperature control system, even if a small, inexpensive element such as a semiconductor laser element is used for the second light source 41. This allows the spectroscopic device 100 to be made smaller, lighter, consume less power, and be less expensive.

[0140] In the spectroscopic device 100 according to each of the above embodiments, the first reflecting surface 331 is the surface 335a of the first mirror member 335, and the second reflecting surface 332 is the surface 336a of the second mirror member 336 attached to the back surface 335b of the first mirror member 335.

[0141] According to this configuration, the movable mirror 33 is configured by combining two mirror members, which makes it easy to increase the reflectance of both the first reflecting surface 331 and the second reflecting surface 332. This increases the S / N ratio (signal-to-noise ratio) of the interference light including the analytical light L1 reflected by the first reflecting surface 331. Similarly, the S / N ratio of the interference light including the measurement light L2 reflected by the second reflecting surface 332 is also increased.

[0142] In the spectroscopic device 100 according to each of the above embodiments, the analytical optical system 3 includes a beam splitter 32 (light splitter) that splits the analytical light L1 emitted from the first light source 51. The gas cell 6 is disposed between the first light source 51 and the beam splitter 32.

[0143] With this configuration, when the analytical light L1 is irradiated onto the sample 9, the analytical light L1 is also always irradiated onto the gas cell 6. Therefore, the spectroscopic device 100 can be calibrated simultaneously with the acquisition of the spectral pattern, enabling particularly highly accurate spectroscopic analysis.

[0144] In the spectroscopic device 100 according to each of the above embodiments, the analytical optical system 3 includes a beam splitter 32 (light splitter) that splits the analytical light L1 emitted from the first light source 51. The gas cell 6 is disposed between the beam splitter 32 and the first light receiving element 36.

[0145] With this configuration, when the analytical light L1 is irradiated onto the sample 9, the analytical light L1 is also always irradiated onto the gas cell 6. Therefore, the spectroscopic device 100 can be calibrated simultaneously with the acquisition of the spectral pattern, enabling particularly highly accurate spectroscopic analysis.

[0146] In the spectroscopic device 100 according to each of the above embodiments, the length measurement unit 40 includes an optical modulator 444 that shifts the frequency of the length measurement light L2 (laser light) emitted from the second light source 41. The length measurement unit 40 obtains a displacement signal corresponding to the position of the movable mirror 33 by interference between the length measurement light L2 reflected by the second reflecting surface 332 and the length measurement light L2 whose frequency has been shifted by the optical modulator 444.

[0147] With this configuration, it is possible to capture the displacement of the movable mirror 33 at intervals that are sufficiently narrower than the wavelength of the measurement light L2, and therefore it is possible to acquire a spectral pattern over a wider wavenumber range (wider wavelength range), i.e., a spectral pattern over a wider band.

[0148] The method for calibrating the spectroscopic device according to the above embodiments is a method for calibrating a spectroscopic device 100 that performs spectroscopic analysis of a sample 9, and includes a mirror position measurement step S102, an analytical light irradiation step S104, a waveform generation step S106, a Fourier transform step S108, and a correction value calculation step S110. In the mirror position measurement step S102, in the spectroscopic device 100 according to the above embodiments, a gas cell 6 is placed on the optical path of the analytical light L1, and then the spectroscopic device 100 acquires a displacement signal corresponding to the position of the movable mirror 33 to measure the position of the movable mirror 33. In the analytical light irradiation step S104, the analytical light L1 is incident on the gas cell 6 while changing the position of the movable mirror 33, and the analytical light L1 emitted from the gas cell 6 is received by the first light receiving element 36, and a first received light signal F(t) is output. In a waveform generation step S106, an interferogram F(x) (a waveform indicating the intensity of the first light receiving signal F(t) originating from the gas cell 6 at each position of the movable mirror 33) is generated based on the first light receiving signal F(t) originating from the gas cell 6 and the measured value of the position of the movable mirror 33. In a Fourier transform step S108, a Fourier transform is performed on the interferogram F(x) to generate a spectral pattern including a peak due to the optical absorption signal. In a correction value calculation step S110, a correction value for correcting the measured value of the position of the movable mirror 33 is calculated based on the difference between the wavelength of the peak due to the optical absorption signal and the fundamental wavelength of the gas cell 6.

[0149] With this configuration, when measuring the position of movable mirror 33 using a displacement signal, the extremely high precision and stability of the energy between levels of atoms and molecules sealed in gas cell 6 can be utilized to calculate a correction value for correcting the measurement value based on the light absorption signal derived from gas cell 6. In other words, a correction value for measuring the position of movable mirror 33 with high precision can be calculated. Therefore, even if the parallelism of the two light reflecting surfaces (first reflecting surface 331 and second reflecting surface 332) of movable mirror 33 is reduced, it is possible to compensate for the decrease in measurement precision. This allows spectroscopic device 100 to be calibrated so as to generate a highly accurate spectral pattern.

[0150] The spectroscopic method according to the embodiment is a method for spectroscopic analysis of a sample 9, and includes a calibration step S100 and a spectral information correction step S112. In the calibration step S100, the calibration method for the spectroscopic device according to the embodiment is executed. In the spectral information correction step S112, after placing the sample 9 on the optical path of the analytical light L1 in the spectroscopic device 100, a spectral pattern including information derived from the sample 9 is acquired, and the spectral pattern including information derived from the sample 9 is corrected based on a correction value.

[0151] With this configuration, even if the parallelism of the two light reflecting surfaces (first reflecting surface 331 and second reflecting surface 332) of movable mirror 33 is reduced, the reduction in measurement accuracy can be compensated for, and a highly accurate spectral pattern can be generated.

[0152] Although the spectroscopic device, the method for calibrating the spectroscopic device, and the spectroscopic method of the present invention have been described above based on the preferred embodiments shown in the drawings, the embodiments of the present invention are not limited to the above. For example, the configuration of each part of the above embodiments may be replaced with any configuration having a similar function, or any other configuration may be added. Furthermore, two or more of the above embodiments may be combined.

[0153] Furthermore, the method for calibrating a spectroscopic device and the spectroscopic method of the present invention may be such that any step for any purpose is added to the above-described embodiments.

[0154] Furthermore, in the above embodiment, a Michelson type interference optical system is used, but other types of interference optical systems may also be used.

[0155] Furthermore, the sample placement is not limited to the illustrated placement, and since the sample-derived signal is generated by applying analytical light to the sample, the sample may be placed at a position other than the above, as long as the analytical light emitted from the sample is incident on the first light-receiving element. [Explanation of symbols]

[0156] 1...optical device, 3...analysis optical system, 4...length measurement optical system, 6...gas cell, 7...arithmetic unit, 8...signal generation unit, 9...sample, 32...beam splitter, 33...moving mirror, 34...fixed mirror, 35...condensing lens, 36...first light receiving element, 40...length measurement unit, 41...second light source, 42...second light splitting element, 43...light feedback unit, 45...second light receiving element, 46...half wave plate, 47...quarter wave plate, 48...quarter wave plate, 49...analyzer, 51...first light source, 61 ...Sample switching unit, 63...insertion / removal mechanism, 72...moving mirror position calculation unit, 74...light intensity calculation unit, 76...Fourier transform unit, 78...moving mirror position correction unit, 81...oscillating circuit, 100...spectroscopic device, 331...first reflecting surface, 332...second reflecting surface, 335...first mirror member, 335a...front surface, 335b...rear surface, 336...second mirror member, 336a...front surface, 336b...rear surface, 337...adhesive layer, 422...beam splitter, 442...optical reflector, 444...optical Modulator, 446...vibration element, 722...preprocessing unit, 724...demodulation processing unit, 726...moving mirror position signal output unit, AS1...absorption spectrum, F(t)...first received light signal, F(x)...interferogram, FP...characteristic point, L1...analysis light, L1a...analysis light, L1b...analysis light, L2...measurement light, L2a...measurement light, L2b...measurement light, P1...absorption peak, P2...absorption peak, P3...absorption peak, P4...absorption peak, S100...calibration step, S10 2...mirror position measurement step, S104...analysis light irradiation step, S106...waveform generation step, S108...Fourier transform step, S110...correction value calculation step, S112...spectral information correction step, S2...second light receiving signal, SP1...spectral pattern, Sd...driving signal, Ss...reference signal, X(t)...moving mirror position signal, X9...absorption peak, XCsD1...absorption peak, XCsD2...absorption peak, Δx...measurement interval, θ...angle

Claims

1. A spectroscopic device that performs spectroscopic analysis of a sample, the spectroscopic device comprising an analytical optical system, a length measurement optical system, and a calculation device, The analytical optical system includes: a movable mirror that is driven to move in translation, the movable mirror having a first reflecting surface that reflects the analytical light emitted from the first light source and adds a first modulation signal to the analytical light, and a second reflecting surface that is located on the opposite side to the first reflecting surface; a gas cell filled with a gas that absorbs light of a predetermined wavelength, and which adds a light absorption signal to the analytical light when the analytical light is incident thereon; a first light-receiving element that receives the analytical light, which includes a sample-derived signal generated by an interaction between the analytical light and the sample, the first modulated signal, and the light absorption signal, and outputs a first received light signal; Equipped with The length measurement optical system includes: a second light source that emits laser light; a length measuring unit that irradiates the laser light onto the second reflecting surface and acquires a displacement signal corresponding to a position of the movable mirror from the laser light reflected by the second reflecting surface; Equipped with The computing device a moving mirror position calculation unit that generates a moving mirror position signal based on the displacement signal; a light intensity calculation unit that generates a waveform representing the intensity of the first light reception signal at each position of the movable mirror based on the first light reception signal and the movable mirror position signal; a Fourier transform unit that performs a Fourier transform on the waveform to generate a spectral pattern including a peak due to the optical absorption signal; a moving mirror position correcting unit that calculates a correction value for correcting the moving mirror position signal based on the position of the peak; A spectroscopic device comprising:

2. the first reflecting surface is a surface of a first mirror member, The spectroscopic device according to claim 1 , wherein the second reflecting surface is a surface of a second mirror member attached to a rear surface of the first mirror member.

3. the analytical optical system includes a beam splitter that splits the analytical light emitted from the first light source, 3. The spectroscopic device according to claim 1, wherein the gas cell is disposed between the first light source and the light splitter.

4. the analytical optical system includes a beam splitter that splits the analytical light emitted from the first light source, 3. The spectroscopic device according to claim 1, wherein the gas cell is disposed between the light splitter and the first light receiving element.

5. the length measuring unit includes an optical modulator that shifts the frequency of the laser light emitted from the second light source, The spectroscopic device according to claim 1 or 2, wherein the length measuring unit acquires the displacement signal by interference between the laser light reflected by the second reflecting surface and the laser light whose frequency has been shifted by the optical modulator.

6. A method for calibrating a spectroscopic device that performs spectroscopic analysis of a sample, comprising:

2. The spectroscopic instrument according to claim 1, further comprising the steps of: after arranging the gas cell on an optical path of the analytical light, causing the spectroscopic instrument to acquire the displacement signal and measure the position of the movable mirror; a step of irradiating the analytical light to the gas cell while changing the position of the movable mirror, causing the first light receiving element to receive the analytical light emitted from the gas cell, and outputting the first light receiving signal derived from the gas cell; generating a waveform indicating the intensity of the first light receiving signal derived from the gas cell at each position of the movable mirror based on measurements of the first light receiving signal derived from the gas cell and the position of the movable mirror; performing a Fourier transform on the waveform from the gas cell to generate a spectral pattern including peaks due to the optical absorption signal; calculating a correction value for correcting the measurement value of the position of the movable mirror based on a difference between the wavelength of the peak and the fundamental wavelength of the gas cell; A method for calibrating a spectroscopic instrument, comprising:

7. 1. A spectroscopic method for performing spectroscopic analysis of a sample, comprising: Executing the method for calibrating a spectroscopic device according to claim 6; in the spectroscopic device, after placing the sample on an optical path of the analytical light, acquiring a spectral pattern including information derived from the sample, and correcting the spectral pattern including information derived from the sample based on the correction value; A spectroscopic method comprising:

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