Fourier spectroscopic analysis device

Abstract

The Fourier spectroscopic analysis device includes: a light source; an interferometer that obtains a first interferogram and a second interferogram with mutually inverted intensity distributions from the light emitted from the light source; a multiplexing optical system that multiplexes the first interferogram and the second interferogram and irradiates the sample; a demultiplexing optical system that demultiplexes the first interferogram and the second interferogram included in the light that has passed through the sample; a light receiving unit that outputs a first light receiving signal obtained by receiving the demultiplexed first interferogram and a second light receiving signal obtained by receiving the demultiplexed second interferogram; and a signal processing device that performs processing to obtain a noise-removed spectrum of the wavelength components in the analysis band using the first light receiving signal and the second light receiving signal.

Description

Technical Field

[0001] The present invention relates to a Fourier spectroscopic analysis apparatus.

[0002] This application claims priority based on Japanese Patent Application No. 2019-196080 filed in Japan on October 29, 2019, and incorporates its content herein. Background Art

[0003] A Fourier spectroscopic analysis apparatus irradiates an interference light (i.e., an interferogram) to a sample, receives the light (i.e., reflected light or transmitted light) passing through the sample, and performs Fourier transform processing on the obtained light reception signal to obtain a spectrum (e.g., a wave spectrum) of the light passing through the sample. Thus, the Fourier spectroscopic analysis apparatus analyzes the sample. The sample as an analysis object of such a Fourier spectroscopic analysis apparatus is basically premised on a sample having no temporal change in optical characteristics (or a sample having little change).

[0004] In the following Patent Document 1, a Fourier spectroscopic analysis apparatus capable of achieving high analysis accuracy even for a sample in which temporal variations in optical characteristics occur is disclosed. Specifically, the Fourier spectroscopic analysis apparatus disclosed in the following Patent Document 1 receives a wavelength component in a first band that is a band for obtaining a spectrum and a wavelength component in a second band different from the first band included in the light passing through the sample. Moreover, the Fourier spectroscopic analysis apparatus disclosed in Patent Document 1 uses the noise included in the wavelength component in the second band to remove the noise in the wavelength component in the first band.

[0005] Prior Art Documents

[0006] Non-Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-52994 Summary of the Invention

[0008] Problems to be Solved by the Present Application

[0009] However, in a Fourier spectroscopic analysis apparatus, if the S / N ratio (i.e., the signal-to-noise ratio) of the light reception signal obtained by receiving the light passing through the sample is low, the analysis accuracy may be reduced. This is the same for the Fourier spectroscopic analysis apparatus disclosed in the above Patent Document 1. Therefore, in a Fourier spectroscopic analysis apparatus, in order to obtain a light reception signal with a high S / N ratio, it is important to effectively use the light used in the analysis of the sample without waste.

[0010] Several aspects of the present invention have been completed in view of the above circumstances, and an object thereof is to provide a Fourier spectroscopic analysis apparatus that can effectively use the light for analysis without waste and thereby achieve high analysis accuracy.

[0011] Means for Solving the Problem

[0012] [1] To solve the above problems, a Fourier spectroscopic analysis apparatus (1) according to one embodiment of the present invention includes: a light source (10) that emits light (L0) including wavelength components in an analysis band, where the wavelength components in the analysis band are bands for obtaining a spectrum of light that has passed through a sample (SP) to be analyzed; an interferometer (20) that obtains a first interferogram (L11) and a second interferogram (L12) whose intensity distributions are inverted with respect to each other from the light emitted from the light source as interference light, i.e., an interferogram (L2); a multiplexing optical system (30) that multiplexes the first interferogram and the second interferogram and irradiates the sample therewith; a demultiplexing optical system (40) that demultiplexes the first interferogram (L41) and the second interferogram (L42) included in the light (L3) that has passed through the sample; a light receiving unit (50) that outputs a first light receiving signal (S1) obtained by receiving the demultiplexed first interference pattern and a second light receiving signal (S2) obtained by receiving the demultiplexed second interference pattern; and a signal processing device (60) that performs processing to obtain a spectrum of the wavelength components in the analysis band, which is noise-removed, using the first light receiving signal and the second light receiving signal.

[0013] [2] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the signal processing device includes: a noise removal unit (61) that removes noise by obtaining a difference between the first light receiving signal and the second light receiving signal; and a Fourier transform unit (62) that performs a Fourier transform process on a signal representing the difference obtained by the noise removal unit to obtain a spectrum of the wavelength components in the analysis band.

[0014] [3] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the multiplexing optical system includes a first lens (LS1) that irradiates the first interferogram and the second interferogram incident at different positions on a front focal plane onto a predetermined irradiation area (A1) of the sample, and the demultiplexing optical system includes a second lens (LS2) that condenses the first interferogram and the second interferogram included in the light that has passed through the sample at different positions (FP1, FP2) on a rear focal plane.

[0015] [4] Further, in a Fourier spectroscopic analysis apparatus according to an aspect of the present invention, the multiplex optical system includes a polarization multiplexing element (31) that multiplexes the first interferogram in the first polarization state in the first interferogram obtained by the interferometer and the second interferogram in the second polarization state different from the first polarization state in the second interferogram obtained by the interferometer. The demultiplex optical system includes a polarization demultiplexing element (41) that demultiplexes the first interferogram and the second interferogram included in the light passing through the sample according to the polarization state.

[0016] [5] Further, in a Fourier spectroscopic analysis apparatus according to an aspect of the present invention, the multiplex optical system includes: a first polarizer (32) that sets the first interferogram obtained by the interferometer to the first polarization state; and a second polarizer (33) that sets the second interferogram obtained by the interferometer to the second polarization state.

[0017] [6] Further, in a Fourier spectroscopic analysis apparatus according to an aspect of the present invention, the multiplex optical system includes a first deflection element (M1) that directs the first interferogram in the second polarization state and the second interferogram in the first polarization state that have passed through the polarization multiplexing element toward the sample. The demultiplex optical system includes a second deflection element (M2) that directs the light reflected by the first deflection element and passing through the sample toward the polarization demultiplexing element.

[0018] [7] Further, in a Fourier spectroscopic analysis apparatus according to an aspect of the present invention, the interferometer includes: a beam splitter (21) that splits the light emitted from the light source into a first branch light (L01) and a second branch light (L02), and causes the first branch light and the second branch light passing through different optical paths to interfere to obtain the first interferogram and the second interferogram; a fixed mirror (22) that reflects the first branch light split by the beam splitter and makes it incident on the beam splitter; a moving mirror (23) that is configured to reciprocate along the optical path of the second branch light, reflects the second branch light split by the beam splitter, and makes it incident on the beam splitter; a first output unit (PT1) that outputs the first interferogram to the outside; and a second output unit (PT2) that outputs the second interferogram to the outside.

[0019] [8] Further, in a Fourier spectroscopic analysis apparatus according to an aspect of the present invention, the light source is a halogen lamp having a bandwidth of 350 [nm] to 4500 [nm].

[0020] [9] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the light receiving unit includes a detector capable of receiving wavelength components of 1 [μm] to 2.5 [μm].

[0021]

[10] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the first interferogram and the second interferogram are incident on different positions of the front focal plane of the first lens.

[0022]

[11] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the first lens is a Fourier transform lens or a telecentric lens.

[0023]

[12] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the second lens is a Fourier transform lens or a telecentric lens.

[0024]

[13] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the first polarization state is p-polarized light, and the second polarization state is s-polarized light.

[0025]

[14] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the polarization beam combiner transmits the first interferogram in which the first polarizer is in the first polarization state, and reflects the second interferogram in which the second polarizer is in the second polarization state.

[0026]

[15] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the polarization beam splitter transmits the light in the first polarization state included in the light passing through the sample, and reflects the light in the second polarization state included in the light passing through the sample.

[0027]

[16] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the polarization beam combiner transmits the first polarization state component of the first interferogram, reflects the second polarization state component of the first interferogram, transmits the first polarization state component of the second interferogram, and reflects the second polarization state component of the second interferogram.

[0028]

[17] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the polarization beam combiner irradiates the sample with the first polarization state component of the first interferogram that is transmitted and the second polarization state component of the second interferogram that is reflected.

[0029]

[18] Further, in the Fourier spectroscopic analysis apparatus according to one embodiment of the present invention, the first deflection element and the second deflection element are mirrors.

[0030]

[19] Further, in the Fourier spectroscopic analysis device according to one embodiment of the present invention, the polarization multiplexing element emits the second polarization light state component of the reflected first interferogram and the first polarization light state component of the transmitted second interferogram to the first deflection element.

[0031]

[20] Further, in the Fourier spectroscopic analysis device according to one embodiment of the present invention,

[0032] The signal processing device removes the noise overlapping the first received light signal and the second received light signal by performing a process of subtracting the second received light signal from the first received light signal.

[0033] Advantageous Effects of Invention

[0034] According to one embodiment of the present invention, there is an effect that high analysis accuracy can be achieved by efficiently using the light for analysis without waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a block diagram showing the main part structure of a Fourier spectroscopic analysis device according to an embodiment of the present invention.

[0036] Figure 2 is a diagram showing a structural example of an interferometer included in a Fourier spectroscopic analysis device according to an embodiment of the present invention.

[0037] Figure 3 is a diagram showing a first structural example of a multiplexing optical system and a demultiplexing optical system included in a Fourier spectroscopic analysis device according to an embodiment of the present invention.

[0038] Figure 4 is a diagram showing a second structural example of a multiplexing optical system and a demultiplexing optical system included in a Fourier spectroscopic analysis device according to an embodiment of the present invention.

[0039] Figure 5 is a diagram showing a third structural example of a multiplexing optical system and a demultiplexing optical system included in a Fourier spectroscopic analysis device according to an embodiment of the present invention.

[0040] Figure 6 is a diagram showing a fourth structural example of a multiplexing optical system and a demultiplexing optical system included in a Fourier spectroscopic analysis device according to an embodiment of the present invention.

[0041] Figure 7 is a block diagram showing a structural example of a signal processing device included in a Fourier spectroscopic analysis device according to an embodiment of the present invention.

[0042] Figure 8A is a first diagram for explaining the principle of removing noise overlapping a received light signal in an embodiment of the present invention.

[0043] Figure 8B It is the second figure for explaining the principle of removing noise overlapping the received optical signal in an embodiment of the present invention. Detailed Embodiment

[0044] Hereinafter, with reference to the accompanying drawings, a Fourier spectroscopic analysis apparatus according to an embodiment of the present invention will be described in detail.

[0045] [Summary]

[0046] The embodiment of the present invention relates to achieving high analysis accuracy by efficiently using the light for analysis without waste. Specifically, by efficiently using the light for analysis without waste, a received optical signal with a high S / N ratio is obtained, thereby achieving high analysis accuracy. In the embodiment of the present invention, even when the sample has temporal variations in optical properties, high analysis accuracy can be achieved by efficiently using the light for analysis without waste.

[0047] The Fourier spectroscopic analysis apparatus includes an interferometer in order to obtain an interferogram (interference pattern) irradiated onto the sample. As such an interferometer, for example, a Michelson interferometer including a beam splitter, a fixed mirror, and a movable mirror can be used. This interferometer branches the light emitted from the light source into a first branched light toward the fixed mirror and a second branched light toward the movable mirror by the beam splitter, and causes the first branched light reflected by the fixed mirror and the second branched light reflected by the movable mirror to interfere by the beam splitter, thereby obtaining an interferogram irradiated onto the sample.

[0048] However, in the Fourier spectroscopic analysis apparatus, an interferogram as a modulated light is obtained by using the change in the optical path length difference (i.e., the difference between the optical path lengths of the first branched light and the second branched light) generated by the movable mirror provided in the interferometer. Therefore, it is basically assumed that the sample to be analyzed by the Fourier spectroscopic analysis apparatus has no temporal change in optical properties, or even if there is a temporal change in optical properties, the speed of the change is sufficiently slower than the moving speed of the movable mirror provided in the interferometer.

[0049] However, in the case where the Fourier spectroscopic analysis apparatus is to be used in various fields, it can be considered that a sample whose optical properties change relatively quickly with respect to the moving speed of the movable mirror becomes the analysis object. For example, in industrial processes and chemical processes, a fluid in which particles float (which may also be powder), a moving body having a light-scattering surface with irregularities formed on the surface, a suspended and fluid sample stirred in a stirring container, etc. can be considered as the analysis object of the Fourier spectroscopic analysis apparatus.

[0050] If a sample with rapidly changing optical properties is to be analyzed by a Fourier spectroscopic analysis device, fluctuations corresponding to the temporal change in the optical properties of the sample are generated via the interferogram of the sample. In other words, the interferogram via the sample can be said to be a diagram that has been modulated corresponding to the temporal change in the optical properties of the sample. As a result, noise containing a relatively large number of low-frequency components (so-called "colored noise") is superimposed on the interferogram via the sample. Since the noise superimposed on the interferogram appears as noise even after Fourier transform processing, the analysis accuracy is reduced.

[0051] In addition, in a Fourier spectroscopic analysis device, if the S / N ratio of the light reception signal obtained by receiving the light via the sample is low, the analysis accuracy may be reduced. This is the same in the case of analyzing a sample in which temporal fluctuations in optical properties occur. Therefore, in a Fourier spectroscopic analysis device, in order to obtain a light reception signal with a high S / N ratio, it is important to effectively utilize the light used in the analysis of the sample without waste as much as possible.

[0052] In an embodiment of the present invention, there are provided: an interferometer that obtains a first interferogram and a second interferogram whose intensity distributions are inverted with respect to each other; a multiplexing optical system that multiplexes the first interferogram and the second interferogram and irradiates the sample therewith; and a demultiplexing optical system that demultiplexes the first interferogram and the second interferogram included in the light via the sample. Then, using a first light reception signal obtained by receiving the demultiplexed first interferogram and a second light reception signal obtained by receiving the demultiplexed second interferogram, a spectrum from which noise has been removed for the wavelength components in the analysis band that is the band for obtaining the spectrum is obtained. Thereby, the light used for analysis can be effectively utilized without waste, and high analysis accuracy can be achieved.

[0053] [Embodiment]

[0054] <Main structure of Fourier spectroscopic analysis device>

[0055] Figure 1 is a block diagram showing the main structure of a Fourier spectroscopic analysis device 1 according to an embodiment of the present invention. As Figure 1 shown, the Fourier spectroscopic analysis device 1 of the present embodiment includes a light source 10, an interferometer 20, a multiplexing optical system 30, a demultiplexing optical system 40, a light receiving unit 50, and a signal processing device 60. Such a Fourier spectroscopic analysis device 1 irradiates a sample SP with light containing a plurality of wavelength components (i.e., an interferogram L2), receives the light L3 via the sample SP, performs Fourier transform processing on the obtained light reception signals S1 and S2, and obtains the spectrum (e.g., a wave spectrum) of the light L3 via the sample SP, thereby analyzing the sample SP.

[0056] The above-mentioned sample SP can be any sample, but in this embodiment, a sample whose optical characteristics change over time is used. For example, in industrial processes and chemical processes, it can be a fluid in which particles are suspended (it can also be powder), a moving body with a light-scattering surface having irregularities formed on its surface, a suspended and fluid sample stirred in a stirring container, etc. In addition, as the light L3 passing through the above-mentioned sample SP, the reflected light reflected by the sample SP and the transmitted light passing through the sample SP can be cited, but in this embodiment, the light L3 is the transmitted light passing through the sample SP.

[0057] The light source 10 emits light L0 including multiple wavelength components. As this light source 10, any light source can be used according to the optical characteristics of the sample SP. For example, a light source having a wide bandwidth such as a halogen lamp, a semiconductor light-emitting element such as an LD (Laser Diode) or an LED (Light Emitting Diode) can be used. In addition, in this embodiment, a halogen lamp is used as the light source 10. The bandwidth of the halogen lamp is, for example, in the range of about 350 [nm] to 4500 [nm] in wavelength.

[0058] The interferometer 20 causes the light L0 emitted from the light source 10 to interfere, and obtains the light (i.e., interference light: interference pattern) irradiated onto the sample SP. Here, the interferometer 20 of this embodiment obtains an interference pattern L11 (i.e., the first interference pattern) and an interference pattern L12 (i.e., the second interference pattern) whose intensity distributions are inverted with respect to each other as the above-mentioned interference pattern. Obtaining such interference patterns L11 and L12 is to achieve high analysis accuracy by effectively using the light for analyzing the sample SP without waste. In addition, the details of the interferometer 20 will be described later.

[0059] The multiplexing optical system 30 multiplexes the interference patterns L11 and L12 obtained by the interferometer 20, and irradiates the sample SP as the interference pattern L2. The multiplexing of the interference patterns L11 and L12 obtained by the interferometer 20 by the multiplexing optical system 30 is to irradiate the interference patterns L11 and L12 onto the same area (or substantially the same area) of the sample SP. By irradiating in this way, the interference patterns L11 and L12 are modulated in the same way (i.e., modulated corresponding to the temporal change of the optical characteristics of the sample SP). In addition, the details of the multiplexing optical system 30 will be described later.

[0060] The wavelength-division optical system 40 separates the interference patterns L41 and L42 included in the light L3 that has passed through the sample SP (i.e., the transmitted light of the interference pattern L2). Here, the light L3 that has passed through the sample SP is the interference pattern L2 that has undergone absorption corresponding to the optical characteristics of the sample SP and has been modulated corresponding to the temporal change in the optical characteristics of the sample SP. Therefore, the interference pattern L41 is the interference pattern L11 that has undergone absorption corresponding to the optical characteristics of the sample SP and has been modulated corresponding to the temporal change in the optical characteristics of the sample SP. The interference pattern L42 is the interference pattern L12 that has undergone absorption corresponding to the optical characteristics of the sample SP and has been modulated corresponding to the temporal change in the optical characteristics of the sample SP. In addition, details of the wavelength-division optical system 40 will be described later.

[0061] The light-receiving unit 50 receives the interference patterns L41 and L42 that have been wavelength-divided by the wavelength-division optical system 40, and outputs a light-receiving signal S1 (also referred to as the first light-receiving signal) and a light-receiving signal S2 (also referred to as the second light-receiving signal), respectively. The light-receiving unit 50 includes, for example: a detector (not shown) that receives the wavelength-divided interference pattern L41 and outputs the light-receiving signal S1; and a detector (not shown) that receives the wavelength-divided interference pattern L42 and outputs the light-receiving signal S2.

[0062] As the detector included in the light-receiving unit 50, a detector that can receive wavelength components in a preset wavelength band to be analyzed (i.e., the analysis band) is used. For example, the analysis band of the detector is about 1 [μm] to 2.5 [μm]. In addition, at the time of designing the Fourier spectroscopic analysis device 1, the analysis band of the detector can be set to any band.

[0063] The signal processing device 60 performs processing to obtain a spectrum from which noise caused by the temporal change in the optical characteristics of the sample SP has been removed, using the light-receiving signals S1 and S2 output from the light-receiving unit 50. The signal processing device 60 outputs a signal representing the spectrum obtained through the above processing to the outside, or causes a display device (not shown) (e.g., a liquid crystal display device) to display it. In addition, the signal processing device 60 will be described in detail later.

[0064] <Configuration example of the interferometer>

[0065] Figure 2 is a diagram showing a configuration example of the interferometer 20 included in the Fourier spectroscopic analysis device 1 (refer to Figure 1 ) according to an embodiment of the present invention. The interferometer 20 is a Michelson interferometer including a beam splitter 21, a fixed mirror 22, a movable mirror 23, an output port PT1 (also referred to as the first output unit), and an output port PT2 (also referred to as the second output unit). In addition, the interferometer 20 is not limited to a Michelson interferometer, and any interferometer can be used.

[0066] The beam splitter 21 splits the light L0 emitted from the light source 10 into a branched light L01 directed toward the fixed mirror 22 and a branched light L02 directed toward the movable mirror 23. The beam splitter 21 splits the light L0 emitted from the light source 10, for example, at an intensity ratio of 1:1. In addition, the beam splitter 21 causes the branched light L01 reflected by the fixed mirror 22 and the branched light L02 reflected by the movable mirror 23 to interfere, obtaining an interference pattern L11 and an interference pattern L12.

[0067] The fixed mirror 22 is disposed on the optical path of the branched light L01 with its reflecting surface facing the beam splitter 21. The fixed reflecting mirror 22 causes the branched light L01 branched by the beam splitter 21 to move a predetermined amount in a direction orthogonal to its optical path and reflects it back to the beam splitter 21. As the fixed reflecting mirror 22, for example, a reflecting mirror such as a corner cube mirror can be used.

[0068] The movable reflecting mirror 23 is disposed on the optical path of the branched light L02 with its reflecting surface facing the beam splitter 21. The movable reflecting mirror 23 causes the branched light L02 branched by the beam splitter 21 to move a predetermined amount (i.e., the same amount as the offset of the fixed mirror 22) in a direction orthogonal to its optical path and reflects it back to the beam splitter 21. As the movable reflecting mirror 23, similar to the fixed reflecting mirror 22, for example, a reflecting mirror such as a corner cube reflector can be used. The movable reflecting mirror 23 is configured to be able to reciprocate along the optical path of the branched light L02 by a driving mechanism (not shown). The reciprocating speed of the movable mirror 23 is set to about 5 times per second, for example.

[0069] Here, by the reciprocating motion of the movable mirror 23, the wavelength components included in the light L0 emitted from the light source 10 are intensity-modulated at different frequencies. For example, the wavelength components with relatively shorter wavelengths are intensity-modulated at a higher frequency than the wavelength components with relatively longer wavelengths. The interference patterns L11 and L12 obtained by the interferometer 20 are formed by overlapping such wavelength components intensity-modulated at different frequencies.

[0070] In addition, the interference patterns L11 and L12 are obtained by causing the branched lights L01 and L02 to interfere. Therefore, from the law of conservation of energy, it can be known that the intensity distributions of the interference patterns L11 and L12 are inverted with respect to each other. That is, if the intensity distribution of the interference pattern L11 is inverted, it becomes the intensity distribution of the interference pattern L12. In addition, if the intensity distribution of the interference pattern L12 is inverted, it becomes the intensity distribution of the interference pattern L11.

[0071] The output port PT1 is a port for outputting the interference pattern L11 to the outside. The output port PT1 is configured to be able to connect to an optical fiber (i.e., the optical fiber FB1). When the optical fiber FB1 is connected to the output port PT1, the interference pattern L11 output from the output port PT1 is guided by the optical fiber FB1.

[0072] The output port PT2 is a port for outputting the interference pattern L12 to the outside. The output port PT2 is configured in the same manner as the output port PT1 so as to be connectable to an optical fiber (i.e., the optical fiber FB2). When the optical fiber FB2 is connected to the output port PT2, the interference pattern L12 output from the output port PT2 is guided by the optical fiber FB2.

[0073] <First Structural Example of the Wave Combining Optical System and the Wave Splitting Optical System>

[0074] Figure 3 is a diagram showing a first structural example of the wave combining optical system 30 and the wave splitting optical system 40 included in the Fourier spectroscopic analysis apparatus 1 (see Figure 1 ) according to an embodiment of the present invention. As Figure 3 shown, the wave combining optical system 30 of the first structural example includes a lens LS1 (also referred to as a first lens). The wave combining optical system 30 of the first structural example spatially combines the interference patterns L11 and L12 guided by the optical fibers FB1 and FB2 and irradiates a predetermined irradiation area A1 of the sample SP. The wave splitting optical system 40 of the first structural example includes a lens LS2 (also referred to as a second lens). The wave splitting optical system 40 of the first structural example spatially splits the light L3 that has passed through the irradiation area A1 of the sample SP.

[0075] As the lens LS1 of the wave combining optical system 30, for example, a Fourier transform lens, an object-side telecentric lens, or other lenses can be used. The lens LS1 is provided, for example, such that the ends of the optical fibers FB1 and FB2 are arranged at different positions on the front focal plane and the sample SP is arranged on the rear focal plane. Thereby, the interference patterns L11 and L12 incident on different positions on the front focal plane of the lens LS1 can be irradiated onto the irradiation area A1 of the sample SP.

[0076] As the lens LS2 of the wave splitting optical system 40, for example, a Fourier transform lens, an image-side telecentric lens, or other lenses can be used. The lens LS2 is provided such that, for example, the sample SP is arranged on the front focal plane and detectors (not shown) of the light receiving unit 50 are arranged at different positions FP1 and FP2 within the rear focal plane. Thereby, the interference L41 and L42 included in the light L3 that has passed through the irradiation area A1 of the sample SP can be condensed at different positions FP1 and FP2 on the rear focal plane.

[0077] <Second Structural Example of the Wave Combining Optical System and the Wave Splitting Optical System>

[0078] Figure 4 is a diagram showing a second configuration example of the wave combining optical system 30 and the wave splitting optical system 40 included in the Fourier spectroscopic analysis apparatus 1 (see Figure 1 ) according to an embodiment of the present invention. As Figure 4As shown, the multiplexing optical system 30 of the second structural example includes a polarization beam splitter 31 (also referred to as a polarization multiplexing element), a polarizer 32 (also referred to as a first polarizer), and a polarizer 33 (also referred to as a second polarizer). The multiplexing optical system 30 of the second structural example multiplexes the interference patterns L11 and L12 guided by the optical fibers FB1 and FB2 with different polarization states. The demultiplexing optical system 40 of the second structural example includes a polarization beam splitter 41 (also referred to as a polarization demultiplexing element). The demultiplexing optical system 40 of the second structural example demultiplexes the light L3 passing through the sample SP according to the polarization state.

[0079] The polarization beam splitter 31 is disposed between the end of the optical fiber FB1 and the sample SP. The polarization beam splitter 31 transmits the incident light of p-polarization (also referred to as the first polarization state) and reflects the incident light of s-polarization (also referred to as the second polarization state). In addition, in Figure 4 , the p-polarized light is illustrated as the light parallel to the paper surface, and the s-polarized light is illustrated as the light perpendicular to the paper surface. In addition, in Figure 4 , for easy understanding, the polarization components associated with the interference pattern L11 and the polarization components associated with the interference pattern L12 are marked differently.

[0080] The polarizer 32 is disposed between the end of the optical fiber FB1 and the polarization beam splitter 31. The polarizer 32 makes the interference pattern L11 emitted from the optical fiber FB1 become p-polarized light. The polarizer 33 is disposed between the end of the optical fiber FB2 and the polarization beam splitter 31. The polarizer 33 makes the interference pattern L12 emitted from the optical fiber FB2 become s-polarized light.

[0081] The interference pattern L11 emitted from the optical fiber FB1 is made into p-polarized light by passing through the polarizer 32, and the interference pattern L12 emitted from the optical fiber FB2 is made into s-polarized light by passing through the polarizer 33. The interference pattern L11 of p-polarized light passes through the polarization beam splitter 31 and advances toward the sample SP. The interference pattern L12 of s-polarized light is reflected by the polarization beam splitter 31 and advances toward the sample SP. In this way, the interference pattern L2 obtained by multiplexing the interference pattern L11 of p-polarized light and the interference pattern L12 of s-polarized light is irradiated onto the sample SP.

[0082] The polarization beam splitter 41 is disposed between the sample SP and the light receiving unit 50 ( Figure 4 not shown in the figure). The polarization beam splitter 41 demultiplexes the light L3 passing through the sample SP according to its polarization state. Specifically, the polarization beam splitter 41 transmits the interference pattern L41 of p-polarized light included in the light L3 and reflects the interference pattern L42 of s-polarized light included in the light L3. In this way, the interference pattern L41 and the interference pattern L42 included in the light L3 are demultiplexed.

[0083] <Third Structural Example of the Wave Combining Optical System and the Wave Splitting Optical System>

[0084] Figure 5 This is a diagram showing a third configuration example of the wave combining optical system 30 and the wave splitting optical system 40 included in the Fourier spectroscopic analysis apparatus 1 (see Figure 1 ). As shown in Figure 5 , in the wave combining optical system 30 of the third structural example, the polarizers 32 and 33 of the wave combining optical system 30 shown in Figure 4 are omitted. The wave splitting optical system 40 of the third structural example has the same structure as the wave splitting optical system 40 shown in Figure 4 . Therefore, the description of the wave splitting optical system 40 is omitted.

[0085] When the interference pattern L11 emitted from the optical fiber FB1 is incident on the polarization beam splitter 31, the p-polarized light component passes through the polarization beam splitter 31 and advances toward the sample SP, and the s-polarized light component is reflected by the polarization beam splitter 31. When the interference pattern L12 emitted from the optical fiber FB2 is incident on the polarization beam splitter 31, the s-polarized light component is reflected by the polarization beam splitter 31 and advances toward the sample SP, and the p-polarized light component passes through the polarization beam splitter 31.

[0086] In this way, the interference pattern L2 formed by combining the p-polarized light component of the interference pattern L11 and the s-polarized light component of the interference pattern L12 is irradiated onto the sample SP.

[0087] Furthermore, in the third structural example, an interference pattern L2a is obtained by combining the s-polarized light component of the interference pattern L11 and the p-polarized light component of the interference pattern L12. Since the interference pattern L2a is not irradiated onto the sample SP, it is not used in the analysis of the sample SP.

[0088] <Fourth Configuration Example of the Wave Combining Optical System and the Wave Splitting Optical System>

[0089] Figure 6 This is a diagram showing a fourth configuration example of the wave combining optical system 30 and the wave splitting optical system 40 included in the Fourier spectroscopic analysis apparatus 1 (see Figure 1 ). As shown in Figure 6 , the wave combining optical system 30 of the fourth structural example is obtained by adding a mirror M1 (also referred to as a first deflection element) to the wave combining optical system 30 shown in Figure 5 . The wave splitting optical system 40 of the fourth structural example is obtained by adding a mirror M2 (also referred to as a second deflection element) to the wave splitting optical system 40 shown in Figure 4 , Figure 5 .

[0090] The mirror M1 reflects the interference pattern L2a obtained by the polarization beam splitter 31 (i.e., the interference pattern formed by combining the s-polarized light component of the interference pattern L11 and the p-polarized light component of the interference pattern L12), and directs it towards the sample SP. Preferably, the position where the interference pattern L2a is irradiated onto the sample SP is extremely close to the position where the interference pattern L2 is irradiated onto the sample SP. This is because the interference patterns L2 and L2a are modulated as similarly as possible according to the temporal changes in the optical characteristics of the sample SP. Any mirror can be used as long as it can reflect the interference pattern L2a and direct it towards the sample SP.

[0091] The mirror M2 reflects the light L3a that has passed through the sample SP and directs it towards the polarization beam splitter 41. Here, the light L3a that has passed through the sample SP is the interference pattern L2a that has undergone absorption corresponding to the optical characteristics of the sample SP and has been modulated according to the temporal changes in the optical characteristics of the sample SP. Any mirror can be used as long as it can reflect the light L3a that has passed through the sample SP and direct it towards the polarization beam splitter 41.

[0092] In the fourth structural example, the interference pattern L2a obtained by the polarization beam splitter 31 is reflected by the mirror M1 and irradiated onto the sample SP. Then, the light L3a that has passed through the sample SP is reflected by the mirror M2 and then incident on the polarization beam splitter 41. The polarization beam splitter 41 reflects the s-polarized light component contained in the light L3a that has passed through the sample SP, allows the p-polarized light component to pass through, and splits it into the components of the interference pattern L41 and the components of the interference pattern L42.

[0093] <Configuration example of the signal processing device>

[0094] Figure 7 is a block diagram showing a structural example of the signal processing device 60 included in the Fourier spectroscopic analysis device 1 (refer to Figure 1 ) according to an embodiment of the present invention. As Figure 7 shown, the signal processing device 60 includes: a noise removal unit 61 that takes the received light signals S1 and S2 as inputs; and a Fourier transform unit 62 that takes the output signal of the noise removal unit 61 as an input.

[0095] The noise removal unit 61 uses the received light signals S1 and S2 to remove the noise overlapping the received light signals S1 and S2. Specifically, the noise removal unit 61 removes the noise overlapping the received light signals S1 and S2 by obtaining the difference between the received light signal S1 and the received light signal S2. For example, the noise removal unit 61 removes the noise overlapping the received light signals S1 and S2 by performing the process of subtracting the received light signal S2 from the received light signal S1. In addition, as long as the noise overlapping the received light signals S1 and S2 can be removed, the process performed by the noise removal unit 61 can be any process, not limited to the process of subtracting the received light signal S2 from the received light signal S1.

[0096] The Fourier transform unit 62 performs Fourier transform processing on the signal output from the noise removal unit 61 to obtain the spectrum of the wavelength components in the analysis band. Here, the signal output from the noise removal unit 61 is a signal from which the noise caused by the temporal change in the optical characteristics of the sample SP has been removed. Therefore, the spectrum of the wavelength components in the analysis band obtained by the Fourier transform unit 62 becomes a spectrum from which the noise caused by the temporal change in the optical characteristics of the sample SP has been removed.

[0097] <Operation of Fourier spectroscopic analysis device>

[0098] Next, the operation of the Fourier spectroscopic analysis device in the above structure will be described. Hereinafter, for ease of understanding, it is assumed that the multiplexing optical system 30 and the demultiplexing optical system 40 provided in the Fourier spectroscopic analysis device 1 are the systems shown in Figure 4 in the figure.

[0099] When light L0 including a plurality of wavelength components is emitted from the light source 10, the light L0 is incident on the interferometer 20. As Figure 2 shown, the light L0 incident on the interferometer 20 is branched by the beam splitter 21 into a branched light L01 directed toward the fixed mirror 22 and a branched light L02 directed toward the movable mirror 23.

[0100] The branched light L01 branched by the beam splitter 21 is reflected by the fixed mirror 22 and shifted by a predetermined amount, and then travels in the opposite direction and is incident on the beam splitter 21. In addition, the branched light L02 branched by the beam splitter 21 is reflected by the movable mirror 23 and shifted by a predetermined amount, and then travels in the opposite direction and is incident on the beam splitter 21. When the branched lights L01 and L02 are incident on the beam splitter 21, interference occurs, thereby obtaining interference patterns L11 and L12.

[0101] Here, since the movable mirror 23 provided on the interferometer 20 reciprocates, the wavelength components included in the light L0 emitted from the light source 10 are intensity-modulated at different frequencies. For example, the wavelength components with relatively shorter wavelengths are intensity-modulated at a higher frequency than the wavelength components with relatively longer wavelengths. The interference patterns L11 and L12 formed by overlapping the wavelength components intensity-modulated at such different frequencies are obtained through the interferometer 20.

[0102] The interference pattern L11 obtained by the interferometer 20 is output from the output port PT1 and guided to the multiplexing optical system 30 through the optical fiber FB1. The interference pattern L12 obtained by the interferometer 20 is output from the output port PT2 and guided to the multiplexing optical system 30 through the optical fiber FB2. Then, in the multiplexing optical system 30, the p-polarized light component of the interference pattern L11 and the s-polarized light component of the interference pattern L12 are multiplexed by the multiplexing optical system 30 and irradiated onto the sample SP as the interference pattern L2.

[0103] When the light L3 passing through the sample SP is incident on the demultiplexing optical system 40, demultiplexing is performed according to the polarization state by the polarization beam splitter 41 provided in the demultiplexing optical system 40. Specifically, the interference pattern L41 of the p-polarized light included in the light L3 passes through the polarization beam splitter 41, and the interference pattern L42 of the s-polarized light included in the light L3 is reflected by the polarization beam splitter 41 and demultiplexed. The demultiplexed interference pattern L41 of the p-polarized light and the interference pattern L12 of the s-polarized light are incident on the light receiving unit 50.

[0104] The interference pattern L41 of the p-polarized light and the interference pattern L12 of the s-polarized light incident on the light receiving unit 50 are received by a detector (not shown) provided in the light receiving unit 50. And, a light reception signal S1 obtained by receiving the interference pattern L41 of the p-polarized light and a light reception signal S2 obtained by receiving the interference pattern L12 of the s-polarized light are output from the light receiving unit 50. The light reception signals S1 and S2 output from the light receiving unit 50 are input to the signal processing device 60 (see Figure 7 ).

[0105] When the signal processing device 60 is input with the light reception signals S1 and S2, the noise removal unit 61 removes the noise overlapping the light reception signals S1 and S2 using the light reception signals S1 and S2. For example, the noise removal unit 61 performs a process of subtracting (subtraction) the light reception signal S2 from the light reception signal S1 to obtain the difference between the light reception signal S1 and the light reception signal S2, thereby removing the noise overlapping the light reception signals S1 and S2.

[0106] Figure 8A And Figure 8B are diagrams for explaining the principle of removing the noise overlapping the light reception signal in one embodiment of the present invention. Here, since the light reception signals S1 and S2 are obtained by receiving the interference patterns L41 and L42, the principle of removing the above noise is explained using the interference patterns.

[0107] FIG. 8A is a diagram schematically showing the interference patterns L11 and L12 irradiated onto the sample SP. Figure 8B is a diagram schematically showing the interference patterns L41 and L42 included in the light L3 passing through the sample SP. In addition, in Figure 8A , Figure 8BIn this case, the displacement of the movable mirror 23 included in the interferometer 20 is taken as the horizontal axis, and the intensity of the interference pattern is taken as the vertical axis.

[0108] As shown in FIG. 8, the interference patterns L11 and L12 are in a relationship where their intensity distributions are inverted with respect to each other. That is, they have the following relationship: if the intensity distribution of the interference pattern L11 is inverted, it becomes the intensity distribution of the interference pattern L12; if the intensity distribution of the interference pattern L12 is inverted, it becomes the intensity distribution of the interference pattern L11. In addition, since the interference patterns L11 and L12 are irradiated onto the sample SP, the noise caused by the temporal change in the optical characteristics of the sample SP does not overlap.

[0109] Since the interference patterns L41 and L42 are obtained by splitting the interference patterns L11 and L12 that have passed through the sample SP, they are, like the interference patterns L11 and L12, generally in a relationship where their intensity distributions are inverted with respect to each other. Here, when the interference patterns L41 and L42 pass through the sample SP, they are similarly affected by the temporal change in the optical characteristics of the sample SP. Therefore, as Figure 8B shown, the same noise is superimposed on the interference patterns L41 and L42.

[0110] Therefore, for example, if a process of subtracting the received light signal S2 (that is, the signal obtained by receiving the interference pattern L42) from the received light signal S1 (that is, the signal obtained by receiving the interference pattern L41) is performed, the noise superimposed on the received light signals S1 and S2 can be removed.

[0111] Furthermore, if the above process is performed, the inverted received light signal S2 (that is, the interference pattern L42) and the received light signal S1 (that is, the interference pattern L41) are added. Therefore, the signal intensity of the received light signal obtained by subtracting the received light signals S1 and S2 becomes twice that of the received light signals S1 and S2.

[0112] If the above process is completed, the received light signal obtained by subtracting the received light signals S1 and S2 is output from the noise removal unit 61 to the Fourier transform unit 62. Then, a Fourier transform process is performed on the received light signal output from the noise removal unit 61, and a process of obtaining a spectrum of the wavelength components in the analysis band is performed by the Fourier transform unit 62. By performing such a process, a spectrum from which the noise caused by the temporal change in the optical characteristics of the sample SP has been removed (that is, a spectrum of the wavelength components in the analysis band) is obtained.

[0113] As described above, in the present embodiment, there are provided: an interferometer 20 that obtains interference patterns L11 and L12 with inverted intensity distributions; a multiplexing optical system 30 that multiplexes the interference patterns L11 and L12 and irradiates a sample SP with the multiplexed interference pattern L2; and a demultiplexing optical system 40 that demultiplexes the interference patterns L41 and L42 included in the light L3 that has passed through the sample SP. Then, using the light reception signal S1 obtained by receiving the demultiplexed interference pattern L41 and the light reception signal S2 obtained by receiving the demultiplexed interference pattern L42, a spectrum of the wavelength components in the analysis band, which is the band for obtaining the spectrum, with noise removed is obtained. Thereby, the light used for analysis can be effectively utilized without waste, and high analysis accuracy can be achieved.

[0114] Here, it is assumed that there is no light loss in the multiplexing optical system 30 and the demultiplexing optical system 40. When the structures of the multiplexing optical system 30 and the demultiplexing optical system 40 are Figure 3 , Figure 6 as shown in the first structural example and the fourth structural example, most of the interference patterns L11 and L12 can be effectively utilized without waste. When the structures of the multiplexing optical system 30 and the demultiplexing optical system 40 are Figure 4 , Figure 5 as shown in the second structural example and the third structural example, about half of the interference patterns L11 and L12 are wasted. However, the interference patterns L11 and L12 can be effectively utilized to a level equal to or higher than that of existing Fourier spectroscopic analysis devices.

[0115] In this way, in the present embodiment, the light used for analyzing the sample SP can be effectively utilized without waste to a level equal to or higher than that of conventional Fourier spectroscopic analysis devices, and the S / N ratios of the light reception signals S1 and S2 can be increased. Thereby, high analysis accuracy can be achieved. This is also the case when analyzing a sample SP that exhibits temporal variations in optical properties.

[0116] The Fourier spectroscopic analysis device according to the embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment and can be freely modified within the scope of the present invention. For example, in the above embodiment, an example in which the light reception signals S1 and S2 output from the light receiving unit 50 are directly processed by the signal processing device 60 has been described. However, the light reception signals S1 and S2 output from the light receiving unit 50 may be stored in a memory and then processed by the signal processing device 60.

[0117] Description of Reference Numerals

[0118] 1 Fourier spectroscopic analysis device; 10 light source; 20 interferometer; 21 beam splitter; 22 fixed mirror; 23 movable mirror; 30 multiplex optical system; 31 polarization beam splitter; 32, 33 polarizer; 40 demultiplex optical system; 41 polarization beam splitter; 50 light receiving section; 60 signal processing device; 61 noise removal section; 62 Fourier transform section; Al irradiation area; FP1, FP2 positions; L0 light; L01, L02 branched light; L2 interferogram; L11, L12 interferograms; L41, L42 interferograms; LSI, LS2 lenses; M1, M2 mirrors; PT1, PT2 output ports; S1, S2 received optical signals; SP sample.

Claims

1. A Fourier spectroscopic analysis device that irradiates a sample to be analyzed with an interference pattern as interference light, performs Fourier transform processing on a light reception signal obtained by receiving the light that has passed through the sample, and obtains a spectrum of the light that has passed through the sample. The Fourier spectroscopic analysis device includes: A light source that emits light including wavelength components in an analysis band, where the analysis band is the band for obtaining the spectrum; An interferometer that obtains a first interference pattern and a second interference pattern with mutually inverted intensity distributions from the light emitted by the light source as the interference pattern; A multiplexing optical system that multiplexes the first interference pattern and the second interference pattern and irradiates the sample; A demultiplexing optical system that demultiplexes the first interference pattern and the second interference pattern included in the light that has passed through the sample; A light receiving unit that outputs a first light reception signal obtained by receiving the demultiplexed first interference pattern and a second light reception signal obtained by receiving the demultiplexed second interference pattern; and A signal processing device that uses the first light reception signal and the second light reception signal to perform processing for obtaining a spectrum of the wavelength components in the analysis band with noise removed, The multiplexing optical system includes a polarization multiplexing element that multiplexes the first interference pattern in a first polarization state in the first interference pattern obtained by the interferometer and the second interference pattern in a second polarization state different from the first polarization state in the second interference pattern obtained by the interferometer, The demultiplexing optical system includes a polarization demultiplexing element that demultiplexes the first interference pattern and the second interference pattern included in the light that has passed through the sample according to the polarization state.

2. The Fourier spectroscopic analysis device according to claim 1, wherein The signal processing device includes: A noise removal unit that removes noise by obtaining the difference between the first light reception signal and the second light reception signal; and A Fourier transform unit that performs Fourier transform processing on the signal representing the difference obtained by the noise removal unit to obtain a spectrum of the wavelength components in the analysis band.

3. The Fourier spectroscopic analysis device according to claim 1 or 2, wherein The multiplexing optical system includes a first lens that irradiates the first interference pattern and the second interference pattern incident at different positions on the front focal plane to a predetermined irradiation area of the sample, The demultiplexing optical system includes a second lens that condenses the first interference pattern and the second interference pattern included in the light that has passed through the sample at different positions on the rear focal plane.

4. The Fourier spectroscopic analysis device according to claim 1, wherein The multiplexing optical system includes: A first polarizer that sets the first interference pattern obtained by the interferometer to the first polarization state; And A second polarizer that sets the second interference pattern obtained by the interferometer to the second polarization state.

5. The Fourier spectroscopic analysis device according to claim 1, wherein The multiplexing optical system includes a first deflection element that directs the first interference pattern in the second polarization state and the second interference pattern in the first polarization state via the polarization multiplexing element toward the specimen. The demultiplexing optical system includes a second deflection element that directs the light reflected by the first deflection element and passing through the specimen toward the polarization demultiplexing element.

6. The Fourier spectroscopic analysis apparatus according to claim 1 or 2, wherein the interferometer includes: a beam splitter that branches the light emitted from the light source into first branch light and second branch light, and causes the first branch light and the second branch light passing through different optical paths to interfere to obtain the first interference pattern and the second interference pattern; a fixed mirror that reflects the first branch light branched by the beam splitter and causes it to enter the beam splitter; a movable mirror configured to reciprocate along the optical path of the second branch light, reflect the second branch light branched by the beam splitter, and cause it to enter the beam splitter; a first output unit that outputs the first interference pattern to the outside; and a second output unit that outputs the second interference pattern to the outside.

7. The Fourier spectroscopic analysis apparatus according to claim 1 or 2, wherein the light source is a halogen lamp with a bandwidth of 350 nm to 4500 nm.

8. The Fourier spectroscopic analysis apparatus according to claim 1 or 2, wherein the light receiving unit includes a detector capable of receiving wavelength components of 1 μm to 2.5 μm.

9. The Fourier spectroscopic analysis apparatus according to claim 3, wherein the first interference pattern and the second interference pattern enter different positions on the front focal plane of the first lens.

10. The Fourier spectroscopic analysis apparatus according to claim 3, wherein the first lens is a Fourier transform lens or a telecentric lens.

11. The Fourier spectroscopic analysis apparatus according to claim 3, wherein the second lens is a Fourier transform lens or a telecentric lens.

12. The Fourier spectroscopic analysis apparatus according to claim 4, wherein the first polarization state is p-polarized light, the second polarization state is s-polarized light.

13. The Fourier spectroscopic analysis apparatus according to claim 4, wherein the polarization multiplexing element transmits the first interference pattern in which the first polarizer is in the first polarization state, and reflects the second interference pattern in which the second polarizer is in the second polarization state.

14. The Fourier spectroscopic analysis apparatus according to claim 1, wherein the polarization demultiplexing element transmits the light in the first polarization state included in the light passing through the specimen, and reflects the light in the second polarization state included in the light passing through the specimen.

15. The Fourier spectroscopic analysis apparatus according to claim 1, wherein The polarization beam combining element transmits the first polarization state component of the first interference pattern, reflects the second polarization state component of the first interference pattern, transmits the first polarization state component of the second interference pattern, and reflects the second polarization state component of the second interference pattern.

16. The Fourier spectroscopic analysis device according to claim 15, wherein the polarization beam combining element irradiates the sample with the transmitted first polarization state component of the first interference pattern and the reflected second polarization state component of the second interference pattern.

17. The Fourier spectroscopic analysis device according to claim 5, wherein the first deflection element and the second deflection element are mirrors.

18. The Fourier spectroscopic analysis device according to claim 5, wherein the polarization beam combining element emits the reflected second polarization state component of the first interference pattern and the transmitted first polarization state component of the second interference pattern to the first deflection element.

19. The Fourier spectroscopic analysis device according to claim 2, wherein the signal processing device removes the noise overlapping the first received light signal and the second received light signal by performing a process of subtracting the second received light signal from the first received light signal.

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