Spectroscopic device, calibration method for spectroscopic device, and spectroscopic method

Abstract

The present invention relates to a spectroscopic apparatus, a calibration method for the spectroscopic apparatus, and a spectroscopic method, the spectroscopic apparatus performing spectroscopic analysis of a sample, the spectroscopic apparatus comprising: an analysis optical system comprising: a moving mirror having a first reflecting surface and a second reflecting surface and being driven in translation; a gas cell in which a gas is sealed and which adds a light absorption signal to the analysis light; and a first light receiving element that receives analysis light including a sample source signal, a first modulation signal, and a light absorption signal, the length measurement optical system being provided with a length measurement unit that acquires a displacement signal corresponding to the position of the moving mirror from the laser light reflected by the second reflection surface. A calculation device is provided with a moving mirror position calculation unit, a light intensity calculation unit, a Fourier transform unit, and a moving mirror position correction unit.

Description

Technical Field

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

[0002] Patent Document 1 discloses an optical module that acquires spectral information of light emitted or absorbed by a sample and uses it for spectroscopic analysis based on this spectral information to analyze components in the sample. The optical module includes a reflector unit, a beam splitter unit, a light incident portion, a first photodetector, a second light source, and a second photodetector. The reflector unit includes a movable reflector that moves in a predetermined direction and a fixed mirror that remains fixed in position. In this optical module, the beam splitter unit, the movable reflector, and the fixed mirror constitute an interference optical system into which the measurement light and laser light are incident.

[0003] Measurement light incident from the first light source via the measurement object is split by the beam splitter unit through the light incident portion. A portion of the split measurement light is reflected by the movable reflector 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 returns 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 this optical module, the position of the movable mirror is measured based on the results of detecting the interference light of the laser beam. Furthermore, spectroscopic analysis of the measurement object can be performed based on the results of the movable mirror position measurement and the results of detecting the interference light of the measurement light. Specifically, by calculating the intensity of the measurement light at each position of the movable mirror, a waveform called an interference pattern can be obtained. By performing a Fourier transform on this interference pattern, the spectral pattern of the measurement object can be determined. Therefore, the optical module described in Patent Document 1 is used in FTIR (Fourier transform infrared spectrometer).

[0006] Patent Document 1: International Publication No. 2019 / 009404

[0007] In Fourier transform spectrometers, the accuracy of measuring the position of the movable mirror (moving mirror) is directly related to the accuracy of the wavenumber axis (wavelength axis) of the spectral pattern. Therefore, research is underway to use laser length measurement technology to accurately measure the position of the movable mirror. As part of this technology, the use of a movable mirror with two light-reflecting surfaces positioned in a mutually opposite relationship is being investigated. In order to accurately measure the change in the optical path length of the measurement light using laser light, it is necessary to achieve sufficient parallelism between the light-reflecting surface reflecting the measurement light and the light-reflecting surface reflecting the laser light.

[0008] However, improving the parallelism of the two reflecting surfaces is not easy, and lower parallelism leads to length measurement errors, which reduce the accuracy of the wavenumber axis (wavelength axis) of the spectrum pattern obtained for the measurement object.

[0009] Therefore, it has become a technical problem to realize a spectroscopic device that can compensate for the reduction in length measurement accuracy and generate a high-precision spectrum pattern even when the parallelism of the two light reflecting surfaces of the movable mirror is reduced. Summary of the Invention

[0010] The spectroscopic device according to the application example of the present invention comprises an analyzing optical system, a length measuring optical system, and an arithmetic device, and performs spectroscopic analysis of a sample, wherein:

[0011] The analytical optical system comprises:

[0012] a movable reflector having a first reflective surface and a second reflective surface, and being driven to translate, wherein the first reflective surface reflects analysis light emitted from the first light source and adds a first modulation signal to the analysis light, and the second reflective surface is located on a side opposite to the first reflective surface;

[0013] a gas cell enclosing a gas that absorbs light of a predetermined wavelength, into which the analysis light is incident, and adds a light absorption signal to the analysis light; and

[0014] a first light receiving element receiving the analysis light and outputting a first light receiving signal, wherein the analysis light includes a sample source signal generated by the interaction between the analysis light and the sample, the first modulation signal, and the light absorption signal;

[0015] The length measuring optical system comprises:

[0016] a second light source emitting laser light; and

[0017] The length measuring unit irradiates the second reflecting surface with the laser light, and obtains a displacement signal corresponding to the position of the movable reflecting mirror from the laser light reflected by the second reflecting surface.

[0018] The computing device comprises:

[0019] a moving mirror position calculation unit, which generates a moving mirror position signal based on the displacement signal;

[0020] a light intensity calculation unit that generates a waveform representing the intensity of the first light reception signal at each position of the movable reflector based on the first light reception signal and the movable reflector position signal;

[0021] a Fourier transform unit that performs Fourier transform on the waveform to generate a spectrum pattern including a peak of the light absorption signal; and

[0022] The moving mirror position correcting unit calculates a correction value for correcting the moving mirror position signal based on the position of the peak value.

[0023] A method for calibrating a spectrometer according to an application example of the present invention calibrates a spectrometer for performing spectroscopic analysis of a sample, and includes the following steps:

[0024] In the spectroscopic device according to the application example of the present invention, after the gas cell is arranged on the optical path of the analysis light, the spectroscopic device is caused to acquire the displacement signal and measure the position of the movable mirror;

[0025] while changing the position of the movable reflective mirror, causing the analysis light to enter the gas cell, causing the first light receiving element to receive the analysis light emitted from the gas cell, and outputting the first light receiving signal originating from the gas cell;

[0026] generating a waveform representing the intensity of the first light reception signal from the gas cell at each position of the movable reflecting mirror based on the first light reception signal from the gas cell and a measured value of the position of the movable reflecting mirror;

[0027] performing Fourier transform on the waveform originating from the gas cell to generate a spectrum pattern including a peak of the light absorption signal; and

[0028] A correction value for correcting the measured value of the position of the movable mirror is calculated based on the difference between the wavelength of the peak and the fundamental wavelength of the gas cell.

[0029] The spectroscopic method according to the application example of the present invention comprises the following steps:

[0030] Executing the calibration method of the spectroscopic device according to the application example of the present invention; and

[0031] In the spectroscopic device, after the sample is arranged on the optical path of the analysis light, a spectral pattern including information derived from the sample is acquired, and the spectral pattern including information derived from the sample is corrected based on the correction value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a diagram schematically showing the configuration of the spectroscopic device according to the first embodiment.

[0033] Figure 2 It shows Figure 1 A cross-sectional view of an example of the structure of a movable reflector.

[0034] Figure 3 It shows Figure 1 A cross-sectional view of an example of the structure of a movable reflector.

[0035] Figure 4 It shows Figure 1 Schematic diagram of the main parts of the analysis optical system, length measurement optical system, signal generation unit and computing device.

[0036] Figure 5 It is shown by Figure 1 FIG. 1 is a diagram showing an example of a first light receiving signal and a second light receiving signal obtained by the spectroscopic device shown.

[0037] Figure 6 is a diagram showing an example of an interference pattern.

[0038] Figure 7 yes Figure 5 A partially enlarged view of the second light-receiving signal is shown.

[0039] Figure 8 This is an energy level diagram showing the ultrastructure of the Cs(D1) line of a cesium atom.

[0040] Figure 9 yes Figure 8 Absorption spectrum of the Cs(D1) line is shown.

[0041] Figure 10 is Figure 4 An example of a spectral pattern obtained by the spectroscopic apparatus is shown.

[0042] Figure 11 This is a flowchart for explaining the spectroscopic method including the calibration method of the spectroscopic device according to the first embodiment.

[0043] Figure 12 It is a diagram schematically showing the configuration of a spectroscopic device according to the second embodiment.

[0044] Figure 13It is a diagram schematically showing the configuration of a spectroscopic device according to a third embodiment.

[0045] Figure 14 It shows Figure 13 Schematic diagram of the main parts of the analysis optical system, length measurement optical system, signal generation unit and computing device.

[0046] Figure 15 It is shown by Figure 13 FIG. 1 is a diagram showing an example of a first light receiving signal and a movable mirror position signal obtained by the spectroscopic device.

[0047] Figure 16 This is a graph showing the relationship between the measurement interval of the position of the moving reflective mirror and the maximum measured wave number and the minimum measured wavelength in the spectrum pattern.

[0048] Description of Reference Numerals

[0049] 1: Optical device, 3: Analytical optical system, 4: Length measurement optical system, 6: Gas chamber, 7: Calculation device, 8: Signal generation unit, 9: Sample, 32: Beam splitter, 33: Movable reflector, 34: Fixed mirror, 35: Converging lens, 36: First light receiving element, 40: Length measurement unit, 41: Second light source, 42: Second spectroscopic element, 43: Optical feedback unit, 45: Second light receiving element, 46: Half-wavelength plate, 47: Quarter-wavelength plate, 48: Quarter-wavelength plate, 49: Analyzer, 51: First light source , 61: sample switching unit, 63: plug-in mechanism, 72: movable mirror position calculation unit, 74: light intensity calculation unit, 76: Fourier transform unit, 78: movable mirror position correction unit, 81: oscillation circuit, 100: spectrometer, 331: first reflection surface, 332: second reflection surface, 335: first reflection mirror component, 335a: front, 335b: back, 336: second reflection mirror component, 336a: front, 336b: back, 337: adhesive layer, 422: beam splitter, 442: Optical reflector, 444: Optical modulator, 446: Vibration element, 722: Preprocessing unit, 724: Demodulation processing unit, 726: Movable reflector position signal output unit, AS1: Absorption spectrum, F(t): First light-receiving signal, F(x): Interference pattern, FP: Feature point, L1: Analysis light, L1a: Analysis light, L1b: Analysis light, L2: Length measurement light, L2a: Length measurement light, L2b: Length measurement light, P1: Absorption peak, P2: Absorption peak, P3: Absorption peak, P4: Absorption peak, S100 : Calibration step, S102: Reflector position measuring step, S104: Analysis light irradiation step, S106: Waveform generating step, S108: Fourier transform step, S110: Correction value calculating step, S112: Spectral information correction step, S2: Second light receiving signal, SP1: Spectral pattern, Sd: Drive signal, Ss: Reference signal, X(t): Moving reflector position signal, X9: Absorption peak, XCsD1: Absorption peak, XCsD2: Absorption peak, Δx: Measurement interval, θ: Angle. DETAILED DESCRIPTION

[0050] Hereinafter, the spectroscopic device and the calibration method of the spectroscopic device according to the present invention will be described in detail based on the embodiments shown in the drawings.

[0051] 1. First Implementation

[0052] First, a spectroscopic device and a calibration method of the spectroscopic device according to the first embodiment will be described.

[0053] Figure 1 1 is a diagram schematically showing the configuration of a spectroscopic device 100 according to the first embodiment.

[0054] Spectroscopic device

[0055] exist Figure 1 In the spectroscopic device 100 shown, analysis light L1 emitted from a first light source 51 is irradiated onto a sample 9 serving as a test object. The analysis light L1 emitted from the sample 9 is passed through a Michelson-type interference optical system. The intensity changes of the obtained interference light are detected, and the calculations described below are performed to obtain an interference pattern. The obtained interference pattern is Fourier transformed to generate a spectral pattern (spectral information) containing information derived from the sample 9. By selecting the wavelength of the analysis light L1, Figure 1 The spectroscopic device 100 shown can be applied to, for example, FT-IR (Fourier infrared spectroscopy), FT-NIR (Fourier near infrared spectroscopy), FT-VIS (Fourier visible spectroscopy), FT-UV (Fourier ultraviolet spectroscopy), FT-THz (Fourier terahertz spectroscopy), etc. for the sample 9.

[0056] The spectroscopic apparatus 100 includes an optical device 1 , a signal generating unit 8 , and a computing device 7 .

[0057] Among them, such as Figure 1 As shown, the optical device 1 includes an analyzing optical system 3 and a length measuring optical system 4 .

[0058] In the analysis optical system 3, analysis light L1 is irradiated onto the sample 9. To extract the sample-derived signal from the analysis light L1, the analysis light L1 is split and mixed while changing its optical path length to generate interference. The length measurement optical system 4 uses length measurement light L2, a laser beam, to measure the change in the optical path length of the analysis light L1.

[0059] The signal generating unit 8 has the function of outputting a reference signal Ss to the computing device 7, and an example thereof may be a function generator, described later. The computing device 7 has the function of determining a waveform representing the intensity of the interfering light relative to the optical path length, namely, the aforementioned interferogram, based on the signal representing the intensity of the interfering light output from the analyzing optical system 3 and the signal representing the change in the optical path length output from the length measuring optical system 4. The computing device 7 also has the function of performing a Fourier transform on the interferogram to obtain a spectral pattern.

[0060] 1.2. Optical equipment

[0061] Next, the optical device 1 will be described.

[0062] As described above, the optical device 1 includes the analyzing optical system 3 and the length measuring optical system 4 .

[0063] 1.2.1. Analytical optical system

[0064] The analytical optical system 3 includes a first light source 51, a gas cell 6, a beam splitter 32, a movable reflector 33, a fixed mirror 34, a focusing lens 35, and a first light receiving element 36, which constitute a Michelson-type interference optical system. It should be noted that in the analytical optical system 3, some of these optical elements may be omitted, optical elements other than these may be included, and these optical elements may be replaced by other optical elements having equivalent functions.

[0065] The first light source 51 is a light source that emits, for example, white light, i.e., light of a wide wavelength, as analysis light L1. The wavelength range of analysis light L1, i.e., the type of first light source 51, is appropriately selected based on the purpose of the spectroscopic analysis to be performed on the sample 9. For infrared spectroscopic analysis, examples of the first light source 51 include halogen lamps, infrared lamps, tungsten filament lamps, and blackbody lamps. For visible light spectroscopic analysis, examples of the first light source 51 include halogen lamps. For ultraviolet spectroscopic analysis, examples of the first light source 51 include deuterium lamps and UV-LEDs (ultraviolet light-emitting diodes).

[0066] It should be noted that by selecting a wavelength of 100 nm or greater and less than 760 nm for the analysis light L1, a spectroscopic device 100 capable of ultraviolet or visible light spectroscopic analysis can be realized. Furthermore, by selecting a wavelength of 760 nm or greater and less than 20 μm for the analysis light L1, a spectroscopic device 100 capable of infrared or near-infrared spectroscopic analysis can be realized. Furthermore, by selecting a wavelength of 30 μm or greater and less than 3 mm for the analysis light L1, a spectroscopic device 100 capable of terahertz wave spectroscopic analysis can be realized.

[0067] It should be noted that the first light source 51 may also be disposed externally to the spectroscopic device 100. In this case, the analysis light L1 emitted from the externally disposed first light source 51 is simply directed to the spectroscopic device 100. On the other hand, as shown in this embodiment, the spectroscopic device 100 includes the first light source 51, thereby significantly improving the alignment accuracy between the first light source 51 and the beam splitter 32, thereby minimizing the loss of analysis light L1 caused by misalignment.

[0068] After being collimated using a lens, concave mirror, or other device (not shown), analysis light L1 enters gas cell 6. Gas cell 6 contains a gas that absorbs light of a specific wavelength. When analysis light L1 enters gas cell 6, a light absorption signal is added to analysis light L1. The light absorption signal represents the absorption of light of a specific wavelength by the gas. Gas cell 6 will be described in detail later.

[0069] After passing through the gas cell 6, the analysis light L1 enters the beam splitter 32. The beam splitter 32 is a non-polarizing beam splitter that splits the analysis light L1 into two components, analysis light L1a and analysis light L1b. Specifically, the beam splitter 32 functions as follows: it reflects a portion of the analysis light L1 as analysis light L1a toward the movable reflector 33, and transmits the remaining portion of the analysis light L1 as analysis light L1b toward the fixed mirror 34, thereby splitting the analysis light L1 into two components.

[0070] As the type of the beam splitter 32, for example, in addition to Figure 1 In addition to the prism-type element (cube-type element) shown, other examples include flat-plate elements and stacked-type elements. When a flat-plate beam splitter 32 is used, wavelength dispersion occurs in the analysis light L1a and the analysis light L1b. Therefore, a wavelength dispersion compensation plate may be placed between the beam splitter 32 and the fixed mirror 34 as needed.

[0071] The beam splitter 32 transmits the analyzed light L1a reflected by the movable mirror 33 toward the first light receiving element 36 and reflects the analyzed light L1b reflected by the fixed mirror 34 toward the first light receiving element 36. Therefore, the beam splitter 32 has a function of mixing the split analyzed light L1a and L1b.

[0072] Figure 2 and Figure 3 They are shown respectively Figure 1 A cross-sectional view of an example of the structure of the movable reflector 33.

[0073] like Figure 2 and Figure 3 As shown, the movable reflector 33 has a first reflective surface 331 and a second reflective surface 332 which are maintained in a positive and negative relationship with each other, and is driven to move in translation.

[0074] The movable mirror 33 moves relative to the beam splitter 32 in the incident direction of the analysis light L1a and reflects the analysis light L1a off the first reflection surface 331. The phase of the analysis light L1a reflected by the movable mirror 33 changes depending on the position of the movable mirror 33. As a result, the movable mirror 33 adds a first modulation signal to the analysis light L1a. The first modulation signal is the phase change added to the analysis light L1a depending on the position of the movable mirror 33.

[0075] The position of the movable mirror 33 is measured by the length measuring optical system 4 described later. The length measuring laser light emitted from the length measuring optical system 4 is reflected by the second reflecting surface 332. The length measuring optical system 4 measures the position of the movable mirror 33 based on the reflected laser light.

[0076] The moving mechanism (not shown) for moving the movable mirror 33 is not particularly limited, and examples thereof include a single-axis linear stage, a piezoelectric drive device, and a microactuator using MEMS (Micro Electro Mechanical Systems) technology.

[0077] like Figure 2 and Figure 3 As shown, the movable reflector 33 has a first reflective surface 331 and a second reflective surface 332 that are in a positive and negative relationship with each other. Figure 2 and Figure 3 The movable reflector 33 shown includes a first reflector member 335 and a second reflector member 336. The first reflective surface 331 is the front surface 335a of the first reflector member 335, and the second reflective surface 332 is the front surface 336a of the second reflector member 336 attached to the back surface 335b of the first reflector member 335. Furthermore, the back surface 335b of the first reflector member 335 and the back surface 336b of the second reflector member 336 are bonded together by an adhesive layer 337.

[0078] With this configuration, the movable mirror 33 is constructed by combining two mirror components. This makes it easier to increase the reflectivity of both the first reflective surface 331 and the second reflective surface 332. This improves the S / N ratio (signal-to-noise ratio) of the interference light including the analysis light L1 reflected by the first reflective surface 331. Similarly, the S / N ratio of the interference light including the length measurement laser light reflected by the second reflective surface 332 can also be improved.

[0079] On the other hand, the first reflecting surface 331 and the second reflecting surface 332 of the movable reflector 33 are required to be parallel to each other. However, in reality, the parallelism may be reduced due to manufacturing errors of the movable reflector 33, the accuracy of the components, etc. This reduction in parallelism reduces the measurement accuracy of the position of the movable reflector 33.

[0080] Specifically, if the first reflecting surface 331 and the second reflecting surface 332 are not parallel to each other, the optical axis of the analysis light L1 incident on the first reflecting surface 331 and the optical axis of the length-measuring laser light incident on the second reflecting surface 332 are not parallel. This results in an error between the actual travel distance of the movable mirror 33 and the travel distance of the movable mirror 33 measured by the length-measuring optical system 4. This length-measuring error reduces the accuracy of the spectrum pattern acquired by the spectroscopic device 100.

[0081] exist Figure 2 , the reduction in parallelism caused by the manufacturing error of the movable mirror 33 is schematically shown.

[0082] exist Figure 2The adhesive layer 337 shown in the figure has thickness irregularities. When the adhesive layer 337 has thickness irregularities, the parallelism between the first reflective surface 331 and the second reflective surface 332 is reduced. Consequently, for example, the optical axis of the length measurement light L2 deviates from the optical axis of the analysis light L1a by an angle θ.

[0083] exist Figure 3 The dimensional accuracy of the first and second reflector components 335 and 336 is reduced. Specifically, the parallelism between the front surface 335a and the back surface 335b of the first reflector component 335 and the parallelism between the front surface 336a and the back surface 336b of the second reflector component 336 is reduced. As a result, for example, the optical axis of the length measurement light L2 deviates from the optical axis of the analysis light L1a by an angle θ.

[0084] inhibition Figure 2 The manufacturing error of the movable reflector 33 shown in FIG. Figure 3 Achieving the dimensional accuracy of the components shown here will increase the manufacturing cost of the movable reflective mirror 33 and is therefore not easy.

[0085] Therefore, in this embodiment, the spectroscopic device 100 is calibrated using the gas cell 6 described later, thereby compensating for the reduction in the length measurement accuracy of the position of the movable mirror 33 .

[0086] Fixed mirror 34 is fixed relative to beam splitter 32, reflecting analysis light L1b. Analysis light L1b reflected by fixed mirror 34 is mixed with analysis light L1a through beam splitter 32 and received by first light receiving element 36 as interference light. In analysis optical system 3, the position of movable mirror 33 creates an optical path difference between the optical paths of analysis light L1a and analysis light L1b. Consequently, the intensity of the interference light varies depending on the position of movable mirror 33.

[0087] The movable reflector 33 and the fixed mirror 34 may be flat reflectors or retroreflective optical elements such as corner cubes. A metal coating using a metal such as Al, Au, or Ag, or a dielectric multilayer film may be formed on the reflective surface of each reflector.

[0088] The condenser lens 35 condenses the interference light, ie, the mixed analysis light L1 a and L1 b , onto the first light receiving element 36 .

[0089] The first light receiving element 36 receives the interfering light and obtains its intensity. Furthermore, it outputs a signal representing the temporal variation in intensity 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 analysis light L1 and the sample 9, the aforementioned first modulation signal, and the aforementioned light absorption signal. The sample-derived signal includes, for example, the absorption of light of a specific wavelength by the sample 9 when the analysis light L1 acts on the sample 9.

[0090] Examples of the first light receiving element 36 include photodiodes and phototransistors. Examples of the photodiodes include InGaAs-based photodiodes, Si-based photodiodes, and avalanche photodiodes.

[0091] 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 interference shape measurement device, an optical tomography (OCT) imaging device, and the like.

[0092] 1.2.2. Length measurement optical system

[0093] The length measurement optical system 4 is a Michelson-type interference optical system comprising a second light source 41 and a length measurement unit 40. The length measurement unit 40 uses laser interferometry using the length measurement light L2 (laser light) to obtain a displacement signal corresponding to the position of the movable mirror 33. This enables precise length measurement of the position of the movable mirror 33. Figure 1 The length measuring unit 40 shown includes a second spectroscopic element 42, a light feedback unit 43, and a second light receiving element 45. It should be noted that some of these optical elements may be omitted from the length measuring optical system 4, or additional optical elements may be included. These optical elements may also be replaced with other optical elements having equivalent functions.

[0094] The second light source 41 preferably uses a light source that emits light with a narrow spectral linewidth. 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 YAGs (Yttrium Aluminum Garnets).

[0095] The second light source 41 is preferably a semiconductor laser element, thereby enabling the optical device 1 and the spectroscopic apparatus 100 to be miniaturized and lightweight.

[0096] The second spectroscopic element 42 includes a beam splitter 422 , a half-wavelength plate 46 , a quarter-wavelength plate 47 , a quarter-wavelength plate 48 , and an analyzer 49 .

[0097] Beam splitter 422 is a polarization beam splitter that transmits P-polarized light and reflects S-polarized light. Half-wave plate 46 is positioned so that its optical axis is rotated relative to the polarization axis of length measurement light L2. As a result, length measurement light L2 passes through half-wave plate 46 and becomes linearly polarized light consisting of both P-polarized and S-polarized light. This light is then split by beam splitter 422 into two components: P-polarized light and S-polarized light.

[0098] The length measurement light L2a, which is S-polarized light, is converted into circularly polarized light by the quarter-wave plate 48 and enters the optical feedback unit 43. The optical feedback unit 43 reflects the length measurement light L2a and feeds it back to the beam splitter 422. At this time, the length measurement light L2a is converted into P-polarized light by the quarter-wave plate 48.

[0099] Meanwhile, the length 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 the length measurement light L2b. As a result, the phase of the length measurement light L2b changes depending on the position of the movable mirror 33. The movable mirror 33 then adds a displacement signal to the length measurement light L2b. The length measurement light L2b reflected by the movable mirror 33 returns to the beam splitter 422. At this point, the length measurement light L2b is converted into S-polarized light by the quarter-wave plate 47.

[0100] Furthermore, the beam splitter 422 transmits the length measurement light L2a fed back from the optical feedback unit 43 toward the second light receiving element 45, and reflects the length measurement light L2b reflected by the movable mirror 33 toward the second light receiving element 45. Thus, the beam splitter 422 functions to mix the split length measurement lights L2a and L2b. The mixed length measurement lights L2a and L2b pass through the analyzer 49 and are incident on the second light receiving element 45.

[0101] Note that a non-polarization beam splitter may be used instead of a polarization beam splitter in the beam splitter 422. In this case, a wave plate or the like is not required, and thus the optical device 1 can be miniaturized by reducing the number of components.

[0102] The optical feedback unit 43 includes a light reflector 442 that reflects the incident light reflected by the beam splitter 422 and feeds it back to the beam splitter 422. The light reflector 442 is formed of a mirror, for example. This simplifies the structure of the optical feedback unit 43 and contributes to miniaturization of the optical device 1.

[0103] The second light receiving element 45 receives the mixed length measurement light beams L2a and L2b as interference light and obtains its intensity. Furthermore, it outputs a signal representing the temporal variation in intensity as a second light receiving signal S2. This second light receiving signal S2 includes a displacement signal of the movable mirror 33. The displacement signal is the phase variation of the length measurement light beam L2b that is added to the phase of the length measurement light beam L2b according to the position of the movable mirror 33. As described above, the length measurement unit 40 obtains a displacement signal representing the position of the movable mirror 33.

[0104] Examples of the second light receiving element 45 include a photodiode and a phototransistor.

[0105] While the analysis optical system 3 and the length measurement optical system 4 have been described above, it is preferable to perform anti-reflection treatment on the optical elements required for incident light in these optical elements. This improves the S / N ratio of the first light-receiving signal F(t) and the second light-receiving signal S2.

[0106] 1.3. Signal generation department

[0107] Figure 4 It shows Figure 1 Schematic diagram of the main parts of the analysis optical system 3, the length measurement optical system 4, the signal generation unit 8 and the operation device 7.

[0108] Figure 4 The signal generator 8 shown 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. The calculation device 7, described later, generates the moving mirror position signal X(t) based on the reference signal Ss and the aforementioned displacement signal.

[0109] 1.4. Computing Device

[0110] Figure 4 The illustrated computing device 7 includes a movable mirror position computing unit 72, a light intensity computing unit 74, a Fourier transform unit 76, and a movable mirror position correction unit 78. The functions performed by these functional units are implemented by hardware including, for example, a processor, memory, an external interface, an input unit, and a display unit. Specifically, these components are implemented by the processor reading and executing programs stored in the memory. It should be noted that these components can communicate with each other via an external bus.

[0111] Examples of processors include CPUs (Central Processing Units) and DSPs (Digital Signal Processors). It should be noted that, instead of using these processors to execute software, the aforementioned functions can be implemented using FPGAs (Field-Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits).

[0112] Examples of memories 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).

[0113] Examples of the external interface include a digital input / output port such as a USB (Universal Serial Bus) port, an Ethernet (registered trademark) port, and the like.

[0114] Examples of the input unit include various input devices such as a keyboard, mouse, touch panel, and touchpad. Examples of the display unit include a liquid crystal display panel and an organic EL (electroluminescence) display panel. It should be noted that the input unit and display unit can be provided as needed and may be omitted.

[0115] 1.4.1. Moving mirror position calculation unit

[0116] The moving mirror position calculation unit 72 generates a moving mirror position signal X(t) based on the reference signal Ss output from the signal generation unit 8 and the second light reception signal S2, which includes the displacement signal of the moving mirror 33. As the moving mirror 33 moves, the intensity of the interfering light in the length measurement optical system 4 changes accordingly. In this case, the amplitude of the second light reception signal S2 periodically changes depending on the interference conditions, for example. Based on the amplitude changes of the second light reception signal S2, the displacement of the moving mirror 33 can be calculated, and the moving mirror position signal X(t) can be obtained.

[0117] 1.4.2. Light intensity calculation unit

[0118] The light intensity calculation unit 74 generates a waveform (interference pattern F(x)) indicating the intensity of interference light with respect 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).

[0119] As described above, the first light-receiving signal F(t) includes the sample source signal, the first modulation signal, and the light absorption signal. The light intensity calculation unit 74 generates an interference pattern 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 light-receiving signal F(t). The interference pattern F(x) is represented by a function that combines the optical path difference between the light reflected from the movable mirror 33 and the light reflected from the fixed mirror 34 in the analysis optical system 3, and the intensity of the interfering light (the intensity of the first light-receiving signal F(t)) received by the first light-receiving element 36.

[0120] Figure 5 It is shown by Figure 1 FIG. 1 is a diagram showing an example of a first light receiving signal F(t) and a second light receiving signal S2 acquired by the spectroscopic device 100 . Figure 5 The horizontal axis 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 .

[0121] Figure 6 : is a figure which shows an example of the interference pattern F(x). Figure 6 The horizontal axis is the optical path difference of the analysis optical system 3, and the vertical axis is the intensity of the interference light. It should be noted that the optical path difference of the analysis optical system 3 is the difference between the optical path length of the beam splitter 32 and the movable reflector 33 and the optical path length of the beam splitter 32 and the fixed mirror 34. Figure 6 In the figure, the optical path difference zero is taken as the origin of the horizontal axis.

[0122] Figure 7 yes Figure 5 The figure shows a partially enlarged view of the second light receiving signal S2. Figure 7The second light receiving signal S2 shown is a signal that vibrates at a predetermined period, and the point where the amplitude is the largest is the feature point FP. The light intensity calculation unit 74 extracts the time at which the feature point FP is used. Figure 5 The intensity of the first light-receiving signal F(t) shown in the figure can be used to correlate the position of the movable mirror 33 with the intensity of the first light-receiving signal F(t). This allows the acquisition of digital data for the interference pattern F(x). Note that in this case, measurement is based on the shortest interval between feature points FP. Therefore, the shortest measurement interval for the position of the movable mirror 33 is ¼ of the wavelength λ of the length measurement light L2.

[0123] 1.4.3. Fourier Transform

[0124] The Fourier transform unit 76 performs Fourier transform on the interference pattern F(x), thereby generating a spectral pattern unique to the sample 9 .

[0125] In the spectral pattern, the sample-derived signal generated when the analytical light L1 acts on the sample 9 is reflected as an absorption peak. Based on this spectral pattern, the characteristics of the sample 9, such as the material, structure, and component amount, can be analyzed.

[0126] 1.4.4. Moving the mirror position correction unit

[0127] The movable mirror position correction unit 78 calculates a correction value for the measured movable mirror position using a method described below. This allows the displacement of the movable mirror 33, as reflected in the movable mirror position signal X(t), to be closer to the true value. Consequently, the accuracy of the wavenumber axis (wavelength axis) of the resulting spectral pattern can be improved.

[0128] 1.5. Air chamber

[0129] Next, the gas chamber 6 will be described. A gas that absorbs light of a predetermined wavelength is enclosed in the gas chamber 6. Examples of the enclosed gas include gaseous alkali metals such as cesium and rubidium, gaseous halogens such as iodine, and rare gases such as krypton, as well as hydrogen cyanide and acetylene. These atoms or molecules absorb or emit light of a predetermined wavelength. A temperature adjustment mechanism (not shown) may also be provided in the gas chamber 6. This allows the vapor pressure of the gas to be sufficiently increased even if the gas chamber 6 is further miniaturized. Consequently, miniaturization of the gas chamber 6 can be achieved.

[0130] Table 1 below shows examples of combinations of gases (atoms or molecules) sealed in the gas cell 6 and wavelengths of light irradiating the gases.

[0131] Table 1

[0132]

[0133] As shown in Table 1, the absorption wavelength can be changed by selecting the gas sealed in the gas cell 6. It should be noted that when selecting the gas, a gas whose absorption wavelength overlaps with the emission spectrum of the first light source 51 is selected.

[0134] When analysis light L1 enters gas cell 6, analysis light L1 irradiates the gas sealed in gas cell 6. As a result, atoms and molecules constituting the gas transition from a ground state to a higher energy state (excited state) according to the energy of analysis light L1.

[0135] Figure 8 This is an energy level diagram showing the ultrastructure of the Cs(D1) line of a cesium atom.

[0136] like Figure 8 As shown, the cesium atom has 6S 1 / 2 The energy level represented by 6P is used as the ground state energy level. 1 / 2 The energy level represented by is used as the excitation energy level. In addition, 6S 1 / 2 and 6P 1 / 2 Each energy level has an ultrastructure that is split into multiple energy levels. Specifically, 6S 1 / 2 It has two ground state energy levels represented by F=3 and F=4. 1 / 2 There are two excited energy levels represented by F'=3 and F'=4.

[0137] The cesium atom in the ground state, for example, absorbs Figure 8 The Cs(D1) line shown is converted to an excited energy level.

[0138] For example, a cesium atom in the ground state of F=4 absorbs Figure 8 The energy between the energy levels indicated by the arrow (1) is converted to the excited energy level F'=3. In addition, by absorbing Figure 8 The energy between the energy levels shown by the arrow (2) is converted into the excited energy level F'=4.

[0139] In addition, the cesium atom in the ground state energy level F=3 absorbs Figure 8 The energy between the energy levels indicated by the arrow (3) is converted to the excited energy level F'=3. In addition, by absorbing Figure 8 The energy between the energy levels shown by the arrow (4) is transformed into the excited energy level F'=4.

[0140] Table 2 below shows Figure 8 The resonance wavelengths corresponding to the transitions of arrows (1) to (4) are shown.

[0141] Table 2

[0142]

[0143] Figure 9 yes Figure 8 The absorption spectrum of the Cs (D1) line is shown in AS1. Figure 9 Four absorption peaks P1 to P4 are observed in the absorption spectrum AS1 shown. The frequencies of the absorption peaks P1 to P4 are Figure 8 The four transition frequencies indicated by arrows (1) to (4) correspond to each other.

[0144] For example, when the analysis light L1 enters the gas cell 6 enclosed with cesium atoms, Figure 9 The absorption spectrum AS1 shown is superimposed on the spectrum pattern output from the Fourier transform unit 76 .

[0145] Figure 10 is Figure 4 An example of a spectrum pattern SP1 obtained by the spectroscopic device 100 is shown.

[0146] exist Figure 10 The spectrum pattern SP1 shown includes the absorption peak X9 originating from sample 9 and the absorption peaks XCsD1 and XCsD2 of cesium atoms. The absorption peak X9 corresponds to the aforementioned sample source signal. The absorption peak XCsD1 is the absorption peak of the aforementioned Cs (D1) line. It should be noted that Figure 10 The absorption peak XCsD1 shown shows that the four fine peaks shown in Table 2 are not resolved and are considered as a single peak. Furthermore, the absorption peak XCsD2 is the absorption peak of the Cs(D2) line shown in Table 1, and it also shows that multiple fine peaks are not resolved and are considered as a single peak. The absorption peaks XCsD1 and XCsD2 correspond to the aforementioned light absorption signals.

[0147] The wavelengths of the absorption peaks XCsD1 and XCsD2 included in the spectral pattern SP1 correspond to the energies between the aforementioned energy levels, resulting in extremely high accuracy and stability. Furthermore, fluctuations due to temperature changes are less than pm. Therefore, the "true values ​​(fundamental wavelengths)" of the wavelengths of the absorption peaks XCsD1 and XCsD2 can be said to be known. Thus, if a "wavelength deviation Δλ" exists between the measured values ​​of the wavelengths of the absorption peaks XCsD1 and XCsD2 included in the spectral pattern SP1 as an analysis result and the true values ​​(fundamental wavelengths), it can be assumed that the wavelength deviation Δλ is caused by various errors within the spectroscopic device 100.

[0148] Here, if the distance measurement value of the movable mirror 33 by the aforementioned length-measuring optical system 4 contains a measurement error, the effect of this measurement error should be considered. For example, assume that the true value L [mm] of the movable mirror 33's movement is measured, and the measured value L(1 + σ) [mm] includes an error σ. In this case, the error σ causes the spectral pattern SP1 to deviate from the true value λ of the wavelength. This deviation can be expressed as σλ using the error σ. This error σ is the correction value used to obtain the corrected movable mirror position signal X(t).

[0149] As an example, suppose Figure 10 The ultrastructure of the absorption peak XCsD1 shown has been decomposed, where the Figure 9 The measured value of the wavelength of the ultrafine structure corresponding to the absorption peak P1 is 892.0000 nm. As shown in Table 2, since the true value of the resonance wavelength of transition (1) is 894.6054 nm, the wavelength deviation Δλ is Δλ=894.6054-892.0000=2.6054 [nm]. Thus, since Δλ=σλ, 2.6054=σ×894.6054. As a result, σ=0.002912. When the moving mirror position signal before correction is set to X'(t), the moving mirror position signal after correction X(t) can be calculated based on X(t)=X'(t) / (1+σ).

[0150] It should be noted that, after calculating the errors σ from a plurality of absorption peaks, correction may be performed based on their average or other calculations.

[0151] The movable mirror position correction unit 78 of the computing device 7 only needs to have the following function: 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 of the light absorption signal) and the true value of the wavelength of the absorption peak XCsD1 (the fundamental wavelength of the gas cell 6), calculate a correction value for correcting the measured value of the position of the movable mirror 33, and correct the movable mirror position signal X(t) based on this correction.

[0152] Furthermore, in this embodiment, the gas cell 6 is positioned between the first light source 51 and the beam splitter 32. Therefore, when the analysis light L1 is irradiated on the sample 9, the analysis light L1 is also constantly irradiated on the gas cell 6. Therefore, in this embodiment, the absorption peak XCsD1 can be acquired simultaneously with the absorption peak X9 originating from the sample 9. As a result, the correction value can be calculated simultaneously with the acquisition of the spectral pattern SP1, enabling real-time calibration of the spectroscopic device 100 and particularly high-precision spectroscopic analysis.

[0153] It should be noted that the energy between the energy levels of the atoms and molecules enclosed in the gas cell 6 is extremely precise and stable. Therefore, even if the wavelength stability of the length measurement light L2 emitted by the second light source 41 is low, the above-mentioned effect can be achieved. Therefore, even if a small and inexpensive element such as a semiconductor laser element is used in the second light source 41, there is no need for additional equipment such as a light source constant temperature system. This allows the optical device 1 to be miniaturized, lightweight, and have low power consumption and low cost.

[0154] It should be noted that the arrangement of the gas cell 6 is not limited to the above arrangement as long as it is a position where the analysis light L1 can be incident. For example, the gas cell 6 can also be arranged at Figure 1 The beam splitter 32 shown is disposed between the sample 9 and the sample 9 , and may also be disposed between the sample 9 and the condenser lens 35 .

[0155] In addition, the configuration of sample 9 is not limited to the above configuration. For example, sample 9 can also be configured in Figure 1 between the first light source 51 and the beam splitter 32. Furthermore, the spectroscopic device 100 may be configured to obtain a reflection spectrum instead of the above-described spectral pattern SP1 as a transmission spectrum by changing the arrangement of the sample 9.

[0156] 1.6. Spectroscopic method

[0157] Next, a spectroscopic method including a calibration method of the spectroscopic device according to the first embodiment will be described.

[0158] Figure 11 This is a flowchart for explaining the spectroscopic method including the calibration method of the spectroscopic device according to the first embodiment.

[0159] Figure 11 The calibration method of the spectroscopic device shown in the figure includes: a reflector position measuring step S102, an analysis light irradiation step S104, a waveform generating step S106, a Fourier transform step S108, and a correction value calculating step S110. Figure 11 The spectroscopic method shown includes a step of executing the correction method (correction step S100 ) and a spectrum information correction step S112 .

[0160] In the mirror position measurement step S102 , the length measurement light L2 (laser light) is incident on the length measurement unit 40 of the optical device 1 to start measuring the position of the movable mirror 33 . This starts acquiring a displacement signal corresponding to the position of the movable mirror 33 .

[0161] In the analysis light irradiation step S104, the gas cell 6 and the sample 9 are arranged on the optical path of the analysis light L1, and the analysis light is made incident on the gas cell 6 and the sample 9 while changing the position of the movable reflector 33. In addition, the analysis light L1 emitted from the gas cell 6 and the sample 9 is received by the first light receiving element 36, and a first light receiving signal F(t) is output. It should be noted that the incidence of the analysis light L1 on the gas cell 6 and the incidence of the analysis light L1 on the sample 9 can be performed simultaneously or at different times. Figure 1 In the spectroscopic device 100 shown, these operations can be performed simultaneously.

[0162] In the waveform generation step S106, a moving mirror position signal X(t) is generated based on the displacement signal corresponding to the position of the moving mirror 33. Furthermore, based on the first light reception signal F(t) and the moving mirror position signal X(t) (the position of the moving mirror 33), an interference pattern F(x) (a waveform representing the intensity of the first light reception signal F(t) at each position of the moving mirror 33) originating from both the gas cell 6 and the sample 9 is generated.

[0163] In the Fourier transform step S108 , the interference pattern F(x) is Fourier transformed to generate a spectrum pattern including an absorption peak X9 (peak of the sample source signal) and an absorption peak XCsD1 (peak of the light absorption signal).

[0164] 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. That is, the correction value is calculated based on the position of the absorption peak XCsD1.

[0165] In the spectrum information correction step S112 , the spectrum pattern including the absorption peak X9 is corrected based on the correction value.

[0166] According to the above-described method for calibrating a spectroscopic device, even if the parallelism between the first reflecting surface 331 and the second reflecting surface 332 of the movable reflector 33 is reduced, the reduction in the length measurement accuracy (length measurement precision) of the position of the movable reflector 33 can be compensated. Therefore, according to the above-described spectroscopic method, by calibrating the spectroscopic device 100, a high-precision spectral pattern can be generated.

[0167] 2. Second Implementation

[0168] Next, a spectroscopic device according to a second embodiment will be described.

[0169] Figure 12 1 is a diagram schematically showing the configuration of a spectroscopic device 100 according to the second embodiment.

[0170] Next, the second embodiment will be described. However, in the following description, the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. Figure 12 In the present invention, the same components as those in the first embodiment are denoted by the same reference numerals.

[0171] exist Figure 12 The spectroscopic device 100 shown in FIG. 1 is similar to the spectroscopic device 100 except that the structure of the analyzing optical system 3 is different. Figure 1 The spectroscopic device 100 shown is identical.

[0172] Figure 12 The analytical optical system 3 shown has a sample switching unit 61 provided between the beam splitter 32 and the condensing lens 35. The sample switching unit 61 has an insertion and extraction mechanism 63 for inserting and removing the sample 9 and the gas cell 6 on the optical path through which the analytical light L1a and L1b pass. Thus, the state in which the sample 9 is arranged on the optical path and the state in which the gas cell 6 is arranged can be switched exclusively with each other. As a result, it is possible to realize the function of freely switching between the spectroscopic analysis mode for performing spectroscopic analysis of the sample 9 and the correction mode for performing correction of the spectroscopic device 100 using the gas cell 6. Thus, it is possible to realize the spectroscopic device 100 as follows: the spectroscopic device 100 can be automatically calibrated at the desired timing by executing the correction mode. In addition, in the spectroscopic analysis mode, since the gas cell 6 is not present on the optical path, the generation of light loss caused by the gas cell 6 can be suppressed.

[0173] In the second embodiment described above, the same effects as those of the first embodiment can be obtained.

[0174] It should be noted that the sample switching unit 61 may also be disposed between the first light source 51 and the beam splitter 32 .

[0175] In addition, you can also omit Figure 12 The sample switching unit 61 shown in FIG. 1 is configured to position both the gas cell 6 and the sample 9 between the beam splitter 32 and the first light receiving element 36. In this case, when the analysis light L1 is irradiated on the sample 9, the analysis light L1 is also constantly irradiated on the gas cell 6. Therefore, in this embodiment, the absorption peak XCsD1 can be acquired simultaneously with the absorption peak X9 originating from the sample 9. As a result, the correction value can be calculated simultaneously with the acquisition of the spectral pattern SP1. This allows for real-time calibration of the spectroscopic device 100, enabling highly accurate spectroscopic analysis.

[0176] 3. Third Implementation

[0177] Next, a spectroscopic device according to a third embodiment will be described.

[0178] Figure 131 is a diagram schematically showing the configuration of a spectroscopic device 100 according to the third embodiment. Figure 14 It shows Figure 13 Schematic diagram of the main parts of the analysis optical system 3, the length measurement optical system 4, the signal generation unit 8 and the operation device 7.

[0179] Next, the third embodiment will be described. However, the following description will focus on the differences from the first embodiment, and descriptions of the same matters will be omitted. Figure 13 In the drawings, the same components as those in the first embodiment are denoted by the same reference numerals.

[0180] exist Figure 13 The optical feedback unit 43 of the length measuring optical system 4 shown in FIG. 1 is different from the optical feedback unit 43 except that the optical modulator 444 is provided instead of the optical reflector 442 and the structure of the signal generating unit 8 is different. Figure 1 The length measuring optical system 4 shown is the same.

[0181] Figure 13 The optical modulator 444 shown includes a vibrating element 446 that shifts the frequency of the length-measuring light L2a. An example of such an optical modulator 444 is the one disclosed in Japanese Patent Application Laid-Open No. 2022-38156. This publication lists a quartz crystal AT resonator as the vibrating element. Alternatively, an SC-cut quartz crystal resonator, a tuning-fork quartz crystal resonator, or a surface acoustic wave device may be used as the vibrating element 446.

[0182] Figure 13 The signal generating unit 8 shown has a function of generating a drive signal Sd. Figure 13 The signal generating unit 8 shown in FIG. 8 is provided with an oscillation circuit 81. In the oscillation circuit 81, the vibration element 446 operates as a signal source to generate a high-precision periodic signal. Figure 13 and Figure 14 In the signal generating unit 8 shown, the vibrating element 446 oscillates based on the drive signal Sd, and the periodic signal generated by the oscillation circuit 81 is output as the reference signal Ss. In this way, the second modulated signal added by the optical modulator 444 driven by the drive signal Sd and the reference signal Ss are mutually affected in the same way. Therefore, when the second light-receiving signal S2 and the reference signal Ss are provided to the operation in the computing device 7, the influence of the interference included in both can be offset or reduced during the operation. As a result, in the computing device 7, even if it is subject to interference, the position of the movable reflector 33 can be determined with excellent accuracy. In addition, the spectroscopic device 100 can be miniaturized, lightweight, and have low power consumption.

[0183] As the oscillation circuit 81 , for example, there can be mentioned an oscillation circuit disclosed in Japanese Patent Application Laid-Open No. 2022-38156.

[0184] Figure 14 The illustrated moving mirror position calculation unit 72 specifies the position of the moving mirror 33 using optical heterodyne interferometry and generates a moving mirror position signal X(t) based on the result. The length measurement optical system 4 includes an optical modulator 444, which allows the addition of a second modulation signal to the length measurement light L2a. This allows for more accurate phase information corresponding to the position of the moving mirror 33 to be obtained from the resulting interference light when the length measurement lights L2a and L2b are interfering. Furthermore, the calculation unit 7 can accurately determine the position of the moving mirror 33 based on this phase information.

[0185] Figure 14 The illustrated moving mirror position calculation unit 72 includes a preprocessing unit 722, a demodulation unit 724, and a moving mirror position signal output unit 726. The preprocessing unit 722 and the demodulation unit 724 may be those disclosed in Japanese Patent Application Laid-Open No. 2022-38156.

[0186] The preprocessing unit 722 preprocesses the second light receiving signal S2 based on the reference signal Ss. The demodulation unit 724 demodulates the displacement signal corresponding to the position of the movable mirror 33 based on the reference signal Ss from the preprocessed signal output from the preprocessing unit 722.

[0187] The moving mirror position signal output unit 726 generates and outputs the moving mirror position signal X(t) based on the displacement signal of the moving mirror 33 demodulated by the demodulation processing unit 724. The moving mirror position signal X(t) obtained in this way captures the displacement of the moving mirror 33 at intervals sufficiently narrow relative to the wavelength of the length measurement light L2. For example, when the wavelength of the length measurement light L2 is several hundred nanometers, the position resolution of the moving mirror 33 represented by the displacement signal can be less than 10 nanometers. In contrast, in the first embodiment, the position resolution limit is ¼ of the wavelength of the length measurement light L2. Therefore, the light intensity calculation unit 74 can generate digital data for the interference pattern F(x) at even finer intervals than in the first embodiment.

[0188] Figure 15 It is shown by Figure 13 FIG. 1 is a diagram showing an example of the first light receiving signal F(t) and the moving mirror position signal X(t) obtained by the spectroscopic device 100 . Figure 15 The horizontal axis 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 reflecting mirror 33 .

[0189] Figure 15 The moving mirror position signal X(t) shown is the result of continuously detecting changes in the position of the moving mirror 33. It is represented by a smooth curve, demonstrating that high position resolution can be achieved. Therefore, by generating an interferogram F(x) based on this signal, an interferogram F(x) with a larger amount of data can be obtained. A larger amount of data means that the sampling interval of the interferogram F(x) is short, resulting in higher accuracy. Therefore, by using the interferogram F(x) obtained in this way, a high-resolution spectral pattern can ultimately be acquired.

[0190] Furthermore, since the sampling interval can be shortened, a spectral pattern in a wider wavenumber range (wide wavelength range), that is, a spectral pattern in a wider frequency band can be obtained.

[0191] Figure 16 : is a graph showing the relationship between the measurement interval Δx of the position of the movable reflector 33 and the maximum measured wave number and the minimum measured wavelength in the spectrum pattern. Figure 16 As shown in FIG. 1 , the smaller the measurement interval Δx, the larger the maximum measured wavenumber and the shorter the minimum measured wavelength. Therefore, by reducing the measurement interval Δx, a spectrum pattern in a wider wavenumber range (wavelength range) can be obtained.

[0192] It should be noted that, in addition to the aforementioned crystal resonator, the vibration element 446 may also be a silicon resonator, a ceramic resonator, a piezoelectric element, or the like. Among them, the vibration element 446 is preferably a crystal resonator, a silicon resonator, or a ceramic resonator. These resonators, unlike other resonators such as piezoelectric elements, utilize mechanical resonance, resulting in high Q values ​​and easy stabilization of the natural frequency.

[0193] A silicon resonator is a resonator that features a single-crystal silicon wafer, manufactured from a single-crystal silicon substrate using MEMS technology, and a piezoelectric film. MEMS (Micro Electro Mechanical Systems) stands for micro-electromechanical systems. Examples of single-crystal silicon wafer shapes include cantilever beams, such as two-legged tuning forks and three-legged tuning forks, and double cantilever beams. The oscillation frequency of a silicon resonator ranges from 1 kHz to several hundred MHz.

[0194] A ceramic resonator is composed of a piezoelectric ceramic sheet made from sintered piezoelectric ceramics and electrodes. Examples of piezoelectric ceramics include lead zirconate titanate (PZT) and barium titanate (BTO). The oscillation frequency of a ceramic resonator ranges from several hundred kHz to several tens of MHz.

[0195] Alternatively, the optical modulator 444 may be an acousto-optic modulator (AOM), an electro-optic modulator (EOM), or the like. However, the optical modulator 444 having the vibrating element 446 can be significantly smaller and lighter than an AOM or EOM. This can contribute to the miniaturization, weight reduction, and power consumption reduction of the spectroscopic device 100.

[0196] 7. Effects of the above-mentioned embodiments

[0197] The spectroscopic device 100 according to each of the above-described embodiments includes an analysis optical system 3 , a length-measuring optical system 4 , and a calculation device 7 , and performs spectroscopic analysis of a sample 9 .

[0198] The analysis optical system 3 includes a movable reflector 33, a gas cell 6, and a first light receiving element 36. The movable reflector 33 has a first reflective surface 331 and a second reflective surface 332, and is driven for translation. The first reflective surface 331 reflects the analysis light L1 emitted from the first light source 51, adding a first modulation signal to the analysis light L1. The second reflective surface 332 is located opposite the first reflective surface 331. The gas cell 6 contains a gas that absorbs light of a predetermined wavelength. When the analysis light L1 enters the gas cell 6, a light absorption signal is added to the analysis light L1. The first light receiving element 36 receives the analysis light L1 and outputs a first light reception signal F(t). This signal includes a sample origin signal generated by the interaction between the analysis light L1 and the sample 9, the first modulation signal, and the light absorption signal.

[0199] The length measurement optical system 4 includes a second light source 41 and a length measurement unit 40. The second light source 41 emits length measurement light L2 as a laser beam. The length measurement unit 40 irradiates the second reflecting surface 332 with the length measurement light L2 and obtains a displacement signal corresponding to the position of the movable mirror 33 from the length measurement light L2 reflected by the second reflecting surface 332.

[0200] The computing device 7 includes a moving mirror position computing unit 72, a light intensity computing unit 74, a Fourier transform unit 76, and a moving mirror position correction unit 78. The moving mirror position computing unit 72 generates a moving mirror position signal X(t) based on the displacement signal acquired by the length measuring optical system 4. The light intensity computing unit 74 generates an interference pattern F(x) (a waveform representing the intensity of the first light receiving signal F(t) at various positions of the moving mirror 33) based on the first light receiving signal F(t) and the moving mirror position signal X(t). The Fourier transform unit 76 performs a Fourier transform on the interference pattern F(x) to generate a spectral pattern including the peak of the light absorption signal. 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 of the light absorption signal.

[0201] With this configuration, when measuring the position of the movable mirror 33 using the displacement signal, a correction value can be calculated based on the light absorption signal from the gas cell 6, taking advantage of the extremely high precision and stability of the energy levels between atoms and molecules enclosed in the gas cell 6. This correction value is used to correct the measured value. In other words, it is possible to calculate a correction value for accurately measuring the position of the movable mirror 33. Therefore, even if the parallelism of the two light-reflecting surfaces (the first reflection surface 331 and the second reflection surface 332) of the movable mirror 33 is reduced, the reduction in length measurement accuracy can be compensated. This achieves a spectroscopic device 100 capable of generating a highly accurate spectral pattern.

[0202] Furthermore, when achieving the above-mentioned effects, even if a small and inexpensive element such as a semiconductor laser element is used as the second light source 41, there is no need to install ancillary equipment such as a light source constant temperature system. This allows the spectrometer 100 to be miniaturized, lightweight, power-efficient, and cost-effective.

[0203] In the spectroscopic device 100 according to the above embodiments, the first reflecting surface 331 is the front surface 335 a of the first reflector member 335 , and the second reflecting surface 332 is the front surface 336 a of the second reflector member 336 attached to the back surface 335 b of the first reflector member 335 .

[0204] With this configuration, the movable mirror 33 is constructed by combining two mirror components. This facilitates improving the reflectivity of both the first reflecting surface 331 and the second reflecting surface 332. This improves the S / N ratio (signal-to-noise ratio) of the interference light including the analysis light L1 reflected by the first reflecting surface 331. Similarly, the S / N ratio of the interference light including the length measurement light L2 reflected by the second reflecting surface 332 can also be improved.

[0205] In the spectroscopic device 100 according to the above embodiments, the analysis optical system 3 includes a beam splitter 32 (spectrometer) that splits the analysis 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 .

[0206] With this configuration, when analysis light L1 is irradiated on sample 9, analysis light L1 is also always irradiated on gas cell 6. Therefore, spectroscopic device 100 can be calibrated while acquiring a spectral pattern, thereby achieving particularly high-precision spectroscopic analysis.

[0207] In the spectroscopic device 100 according to the above embodiments, the analyzing optical system 3 includes a beam splitter 32 (spectrometer) for splitting the analysis 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 .

[0208] With this configuration, when analysis light L1 is irradiated on sample 9, analysis light L1 is also always irradiated on gas cell 6. Therefore, spectroscopic device 100 can be calibrated while acquiring a spectral pattern, thereby achieving highly accurate spectroscopic analysis.

[0209] In the spectroscopic device 100 according to each of the aforementioned embodiments, the length measuring unit 40 includes an optical modulator 444 that shifts the frequency of the length measuring light L2 (laser light) emitted from the second light source 41. The length measuring unit 40 obtains a displacement signal corresponding to the position of the movable mirror 33 by generating interference between the length measuring light L2 reflected by the second reflecting surface 332 and the length measuring light L2 whose frequency has been shifted by the optical modulator 444.

[0210] With this configuration, the displacement of the moving mirror 33 can be captured at sufficiently narrow intervals relative to the wavelength of the length measuring light L2. Therefore, a spectral pattern can be acquired over a wider wavenumber range (wide wavelength range), that is, a wider bandwidth spectral pattern.

[0211] The spectroscopic device calibration method according to the above-described embodiments is a method for calibrating a spectroscopic device 100 that performs spectroscopic analysis on a sample 9. The method includes a mirror position measurement step S102, an analysis 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, after placing the gas cell 6 in the optical path of the analysis light L1 in the spectroscopic device 100 according to each of the above-described embodiments, the spectroscopic device 100 acquires a displacement signal corresponding to the position of the movable mirror 33, thereby measuring the position of the movable mirror 33. In the analysis light irradiation step S104, while changing the position of the movable mirror 33, the analysis light L1 is incident on the gas cell 6, and the first light receiving element 36 receives the analysis light L1 emitted from the gas cell 6, thereby outputting a first light reception signal F(t). In the waveform generation step S106, an interference pattern F(x) (a waveform representing the intensity of the first light reception signal F(t) from the gas cell 6 at each position of the movable mirror 33) is generated based on the first light reception signal F(t) from the gas cell 6 and the measured value of the position of the movable mirror 33. In the Fourier transform step S108, the interference pattern F(x) is Fourier transformed to generate a spectral pattern including the peak of the light absorption signal. 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 peak of the light absorption signal and the fundamental wavelength of the gas cell 6.

[0212] With this configuration, when the position of the movable mirror 33 is measured using the displacement signal, a correction value can be calculated based on the light absorption signal from the gas cell 6, taking advantage of the extremely high precision and stability of the energy levels between atoms and molecules enclosed in the gas cell 6. This correction value is used to calibrate the measured value. In other words, it is possible to calculate a correction value for accurately measuring the position of the movable mirror 33. Therefore, even if the parallelism of the two light-reflecting surfaces (the first and second light-reflecting surfaces 331 and 332) of the movable mirror 33 is reduced, the reduced length measurement accuracy can be compensated. This allows the spectroscopic device 100 to be calibrated to generate a highly accurate spectral pattern.

[0213] The spectroscopic method according to the embodiment is a method for performing spectroscopic analysis on a sample 9, and includes a calibration step S100 and a spectral information calibration step S112. In calibration step S100, the calibration method for the spectroscopic device according to the embodiment is performed. In spectral information calibration step S112, after placing the sample 9 on the optical path of analysis 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 calibrated based on a calibration value.

[0214] According to this configuration, even when the parallelism of the two light reflecting surfaces (the first reflecting surface 331 and the second reflecting surface 332 ) of the movable reflecting mirror 33 is reduced, the reduction in length measurement accuracy can be compensated, thereby generating a high-precision spectrum pattern.

[0215] The spectroscopic device, spectroscopic device calibration method, and spectroscopic method of the present invention have been described above based on the preferred embodiments shown in the figures. However, the embodiments of the present invention are not limited to the above. For example, the components of the above embodiments may be replaced with any other components having the same function, or any other components may be added. Furthermore, two or more of the above embodiments may be combined.

[0216] Furthermore, the calibration method of a spectroscopic device and the spectroscopic method of the present invention may add steps for arbitrary purposes to the above-described embodiments.

[0217] Furthermore, in the above-described embodiment, a Michelson interference optical system is used; however, other interference optical systems may also be used.

[0218] The sample origin signal is generated by allowing analysis light to act on the sample, so the sample can be placed at any position other than the above, as long as the analysis light emitted from the sample enters the first light receiving element.

Claims

1. A spectroscopic device, characterized in that: The spectrometer is a spectrometer that includes an analysis optical system, a length measurement optical system, and a calculation device, and performs spectroscopic analysis of a sample. The analytical optical system comprises: a movable reflector having a first reflective surface and a second reflective surface and being driven to translate, wherein the first reflective surface reflects the analysis light emitted from the first light source and adds a first modulation signal to the analysis light, and the second reflective surface is located on a side opposite to the first reflective surface; a gas cell enclosing a gas that absorbs light of a predetermined wavelength and adding a light absorption signal to the analysis light upon the incidence of the analysis light; as well as a first light receiving element receiving the analysis light and outputting a first light receiving signal, wherein the analysis light includes a sample source signal generated by the interaction between the analysis light and the sample, the first modulation signal, and the light absorption signal; The length measuring optical system comprises: a second light source emitting laser light; and The length measuring unit irradiates the second reflecting surface with the laser light and obtains a displacement signal corresponding to the position of the movable reflecting mirror from the laser light reflected by the second reflecting surface. The computing device comprises: a moving mirror position calculation unit, which 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 reflector based on the first light reception signal and the movable reflector position signal; a Fourier transform unit that performs Fourier transform on the waveform and generates a spectrum pattern including a peak of the light absorption signal; as well as The moving mirror position correcting unit calculates a correction value for correcting the moving mirror position signal based on the position of the peak value.

2. The spectroscopic device according to claim 1, wherein The first reflecting surface is the front surface of the first reflector component, The second reflective surface is the front surface of the second reflective mirror component attached to the back surface of the first reflective mirror component.

3. The spectroscopic device according to claim 1 or 2, wherein: The analysis optical system includes a spectrometer for splitting the analysis light emitted from the first light source. The gas cell is disposed between the first light source and the beam splitter.

4. The spectroscopic device according to claim 1 or 2, wherein: The analysis optical system includes a spectrometer for splitting the analysis light emitted from the first light source. The gas cell is arranged between the spectrometer and the first light receiving element.

5. The spectroscopic device according to claim 1 or 2, wherein: The length measuring unit includes a light modulator that shifts the frequency of the laser light emitted from the second light source. 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 is shifted by the optical modulator.

6. A method for calibrating a spectroscopic device, characterized in that: The method for calibrating a spectrometer for performing spectroscopic analysis of a sample comprises the following steps: In the spectroscopic device according to claim 1, after the gas cell is arranged on the optical path of the analysis light, the spectroscopic device is caused to acquire the displacement signal and measure the position of the movable mirror; while changing the position of the movable reflective mirror, causing the analysis light to enter the gas cell, causing the first light receiving element to receive the analysis light emitted from the gas cell, and outputting the first light receiving signal originating from the gas cell; generating a waveform representing the intensity of the first light reception signal from the gas cell at each position of the movable reflecting mirror based on the first light reception signal from the gas cell and a measured value of the position of the movable reflecting mirror; performing Fourier transformation on the waveform originating from the gas cell and generating a spectrum pattern including a peak of the light absorption signal; as well as A correction value for correcting the measured value of the position of the movable mirror is calculated based on the difference between the wavelength of the peak and the fundamental wavelength of the gas cell.

7. A spectroscopic method, characterized in that: The spectroscopic method for performing spectroscopic analysis of a sample comprises the following steps: Executing the calibration method of the spectrometer according to claim 6; and In the spectroscopic device, after the sample is arranged on the optical path of the analysis light, a spectrum pattern including information derived from the sample is acquired, and the spectrum pattern including information derived from the sample is corrected based on the correction value.

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