Interferometer and analysis apparatus

Abstract

To provide a means capable of accurately detecting the position of a moving mirror of an interferometer by using a light source.SOLUTION: The interferometer 11 includes a semiconductor laser 25, a beam splitter 21 that splits a laser beam emitted from the semiconductor laser 25 into a first split laser beam 41 and a second split laser beam 42, a fixed mirror 22 that reflects the first split laser beam 41, a first turning mirror 26 that reflects the first split laser beam 41 reflected by the fixed mirror 22, a moving mirror 23 that reflects the second split laser beam 42, a second turning mirror 27 that reflects the second split laser beam 42 reflected by the moving mirror 23, and a moving mechanism 24 that moves the moving mirror 23 so as to change the distance from the beam splitter 21.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to interferometers and analytical instruments. [Background technology]

[0002] A Fourier transform infrared spectrophotometer (FTIR) is an analytical device that uses Fourier transform infrared spectroscopy. This analytical device splits infrared light emitted from a light source using a beam splitter, and reflects one of the split beams on a fixed mirror and the other on a movable mirror. The reflected split beams are combined by the beam splitter to generate an interference wave. The amplitude of the interference wave changes over time as the movable mirror moves continuously. The composition ratio or concentration of the object to be measured is analyzed using a spectrum obtained by Fourier transforming this interference wave. To accurately measure this interference wave, the position of the movable mirror must be detected with high precision. In Patent Document 1, the position of the movable mirror is detected using laser light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7099530 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-333371 Summary of the Invention [Problem to be solved by the invention]

[0004] Traditionally, He-Ne lasers (wavelength: 0.633 μm) have been used as lasers to control moving mirrors. However, in order to miniaturize the equipment or extend the life of the laser, they are being replaced with other light sources. For example, when using a semiconductor laser as the light source, the laser light characteristics required for FTIR include a stable wavelength, a single wavelength with a narrow linewidth, and small beam divergence. To satisfy these conditions, the use of lasers emitting near-infrared light (wavelength: approximately 800 nm to 2500 nm) is being considered. However, because near-infrared light has a longer wavelength than the laser light of a He-Ne laser, there is a problem in that the accuracy of detecting the position of the moving mirror is inferior.

[0005] The present invention has been made in view of the above circumstances, and its object is to provide a means for accurately detecting the position of a moving mirror of an interferometer using a variety of light sources. [Means for solving the problem]

[0006] (1) An interferometer according to the present invention comprises a laser, a beam splitter that splits light emitted from the laser into first and second divided beams, a fixed mirror that reflects the first divided beam, a first folding mirror that reflects the first divided beam reflected by the fixed mirror, a movable mirror that reflects the second divided beam, a second folding mirror that reflects the second divided beam reflected by the movable mirror, a moving mechanism that moves the movable mirror so that the distance from the beam splitter varies, and a light receiving unit that receives the first and second divided beams that are reflected by the first folding mirror, the fixed mirror, the second folding mirror, and the movable mirror, respectively, and combined by the beam splitter.

[0007] The second divided light split by the beam splitter and directed toward the movable mirror is reflected by the movable mirror, then reflected by the second turning mirror, and then reflected by the movable mirror again. The light receiving unit receives the first divided light and the second divided light combined by the beam splitter. The difference in optical path between the first divided light and the second divided light is 4n times (n is a natural number) the moving distance of the movable mirror, improving the resolution of detecting the position of the movable mirror.

[0008] (2) The first folding mirror reflects the first split light beam while shifting its optical axis, The second folding mirror may reflect the second split light beam with its optical axis shifted.

[0009] Since the first and second divided beams are reflected with their optical axes shifted, the first and second divided beams do not return to the laser, which prevents the laser from becoming unstable.

[0010] (3) The laser may be a semiconductor laser.

[0011] (4) The light emitted from the laser may be near-infrared light.

[0012] (5) The beam splitter may have a film for infrared light laminated on one portion thereof and a film for laser light laminated on the other portion thereof.

[0013] (6) The moving mirror may be a corner reflector.

[0014] Even when the moving mirror is moved by the moving mechanism, the second divided light is reflected in parallel.

[0015] (7) The fixed mirror may be a corner reflector.

[0016] (8) The interferometer may further include a frame, and the laser, the beam splitter, the first folding mirror, the second folding mirror, and the light receiving unit may be fixed to the frame to form a unit.

[0017] The laser, beam splitter, first return mirror, second return mirror, and light receiving section are unitized, which makes it easy to adjust the arrangement of these components.

[0018] (9) The present invention may be an analytical device comprising the interferometer, an infrared light source that emits infrared light, a sample cell, and a detection unit, wherein the beam splitter splits the infrared light into first divided infrared light and second divided infrared light, the fixed mirror reflects the first divided infrared light, the movable mirror reflects the second divided infrared light, the sample cell transmits the first divided infrared light and the second divided infrared light combined by the beam splitter, and the detection unit receives the first divided infrared light and the second divided infrared light that have transmitted through the sample cell. [Effects of the Invention]

[0019] According to the present invention, the position of the moving mirror of the interferometer can be detected with high precision using a variety of light sources. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a block diagram showing the configuration of an analysis device 10 according to the first embodiment. [Figure 2] FIG. 2 is a perspective view showing the frame 29. As shown in FIG. [Figure 3] 3A is a cross-sectional view showing the AA cross section of FIG. 2, and FIG. 3B is a cross-sectional view showing the second BB cross section. [Figure 4] FIG. 4 is a block diagram showing an interferometer 11 according to a modification of the first embodiment. [Figure 5] FIG. 5 is a block diagram showing an interferometer 50 according to the second embodiment. [Figure 6]FIG. 6 is a block diagram showing an interferometer 50 according to a first modification of the second embodiment. [Figure 7] FIG. 7 is a block diagram showing an interferometer 50 according to the second modification of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] A preferred embodiment of the present invention will be described below. It should be noted that this embodiment is merely one example of the present invention, and it goes without saying that the example can be modified without departing from the spirit and scope of the present invention.

[0022] [First embodiment] The analytical device 10 according to the first embodiment is, for example, an FTIR. As shown in FIG. 1 , the analytical device 10 includes an interferometer 11, an infrared light source 12, a sample cell 13, a detector 14, multiple parabolic mirrors 15, a concentration calculator 16, a display 17, and a controller 18. Although not shown in the figures, the interferometer 11, the infrared light source 12, the sample cell 13, the detector 14, and the multiple parabolic mirrors 15 are arranged and fixed in the internal space of the housing of the analytical device 10. The controller 18 controls the operation of the interferometer 11, the infrared light source 12, the detector 14, the concentration calculator 16, the display 17, and the like. The controller 18 also controls the operation of a movement mechanism 24 in the interferometer 11.

[0023] The infrared light source 12 emits infrared light as continuous light having many wave numbers. As the infrared light source 12, for example, a tungsten-iodine lamp or a high-intensity ceramic light source is used.

[0024] The sample cell 13 is a container into which a sample is introduced. The sample cell 13 has an entrance window and an exit window. Infrared light enters the sample cell 13 through the entrance window, irradiates the sample, and is emitted to the outside through the exit window. In this embodiment, the sample is automobile exhaust gas, factory exhaust gas, atmospheric gas, gas generated in a manufacturing process, or the like.

[0025] The detection unit 14 detects the infrared light transmitted through the sample cell 13 and outputs a detection signal to the concentration calculation unit 16. The concentration calculation unit 16 performs a fast Fourier transform (FFT) on the detection signal to separate it and calculate the light intensity (spectrum) for each wavelength. The obtained light intensity is displayed on the display unit 17 and is compared with known light intensities to analyze the composition or concentration of the sample.

[0026] Interferometer 11 generates interference waves that trace different sine curves for each wavelength from infrared light emitted from infrared light source 12. The configuration of interferometer 11 will be described later.

[0027] As shown in FIG. 1, the interferometer 11 includes a beam splitter 21, a fixed mirror 22, a movable mirror 23, a moving mechanism 24, a semiconductor laser 25, a first folding mirror 26, a second folding mirror 27, a light receiving unit 28, and a frame 29.

[0028] The beam splitter 21 is a half mirror that splits the irradiated light into transmitted light that transmits the light and reflected light that reflects the light. A semi-transparent film for infrared light (an example of a film for infrared light) is laminated on most of the beam splitter 21, including the center. A semi-transparent film for laser light (an example of a film for laser light) is laminated on part of the periphery of the beam splitter 21. The semi-transparent film for infrared light splits the infrared light emitted from the infrared light source 12 into transmitted light and reflected light. The semi-transparent film for laser light splits the laser light emitted from the semiconductor laser 25 into transmitted light and reflected light.

[0029] The fixed mirror 22 is, for example, a corner reflector in which three plane mirrors are arranged at right angles to each other. The fixed mirror 22 is fixed at a constant distance from the beam splitter 21. The light transmitted through or reflected by the beam splitter 21 is reflected in parallel by the fixed mirror 22 with its optical axis changed.

[0030] The movable mirror 23 is, for example, a corner reflector. The movable mirror 23 is moved by a moving mechanism 24 so that the distance from the beam splitter 21 varies. Although not shown in detail in the figures, the moving mechanism 24 has a guide that extends parallel to the light reflected by or transmitted through the beam splitter 21, a carriage that moves along the guide, and an actuator that moves the carriage. The actuator is, for example, a voice coil motor. The movable mirror 23 is mounted on the carriage and moves, thereby varying the distance from the beam splitter 21.

[0031] The semiconductor laser 25 emits laser light. Laser light is near-infrared light with a wavelength in the range of approximately 800 nm to 2500 nm. The semiconductor laser 25 is an example of a laser. Laser light is an example of light.

[0032] The first folding mirror 26 is, for example, a roof mirror in which two plane mirrors are arranged at a right angle. The first folding mirror 26 reflects the first divided laser beam 41 reflected by the fixed mirror 22 while shifting the optical axis of the first divided laser beam 41.

[0033] The second folding mirror 27 is, for example, a roof mirror, and reflects the second divided laser beam 42 reflected by the movable mirror 23 with its optical axis shifted.

[0034] The light receiving section 28 is, for example, a photodiode, which detects the received laser light and outputs a detection signal.

[0035] 2 and 3, frame 29 is a unit that fixes semiconductor laser 25, beam splitter 21, first folding mirror 26, second folding mirror 27, and light receiving unit 28. Frame 29 may be, for example, a rectangular parallelepiped block cut from aluminum, or multiple steel plates fastened together to form a rectangular parallelepiped shape. Frame 29 has openings 29A appropriately positioned therein to allow infrared light and laser light to pass through.

[0036] Beam splitter 21 is fixed in the internal space of frame 29. Light that enters frame 29 through opening 29A hits beam splitter 21. Semiconductor laser 25, first folding mirror 26, second folding mirror 27, and light receiving unit 28 are fixed to frame 29 so as to be at predetermined positions and angles relative to fixed beam splitter 21.

[0037] The following describes the optical path of the infrared light in the interferometer 11. Note that the infrared light is shown by a solid line in FIG. The infrared light emitted from the infrared light source 12 is split by the beam splitter 21 into a first split infrared light 31 and a second split infrared light 32. The first split infrared light 31 is transmitted light that passes through the beam splitter 21. The second split infrared light 32 is reflected light that is reflected by the beam splitter 21. The fixed mirror 22 reflects the first split infrared light 31 back to the beam splitter 21. The movable mirror 23 reflects the second split infrared light 32 back to the beam splitter 21. The movable mirror 23 is moved back and forth by the movement mechanism 24. As a result, the second split infrared light 32 that is reflected by the movable mirror 23 and returns to the beam splitter 21 and the first split infrared light 31 that is reflected by the fixed mirror 22 and returns to the beam splitter 21 are combined as an interference wave 33. The interference wave 33 traces a different sine curve for each wavelength. Interference wave 33 is reflected by parabolic mirror 15 and enters sample cell 13. Interference wave 33 emitted from sample cell 13 is reflected by parabolic mirror 15 and enters detection unit 14. Note that parabolic mirror 15 is not an essential component and may be omitted if there is no need to fold the optical path of the infrared light.

[0038] The following describes the optical path of the laser light in the interferometer 11. Note that the laser light is indicated by a broken line in FIG. The laser light emitted from the semiconductor laser 25 is split by the beam splitter 21 into a first divided laser light 41 and a second divided laser light 42. The first divided laser light 41 is a reflected light that is reflected by the beam splitter 21. The second divided laser light 42 is a transmitted light that is transmitted through the beam splitter 21. The first divided laser light 41 is an example of a first divided light. The second divided laser light 42 is an example of a second divided light.

[0039] The fixed mirror 22 reflects the first divided laser beam 41 toward the first folding mirror 26. The first divided laser beam 41 reflected by the first folding mirror 26 shifts its optical axis and returns to the fixed mirror 22. The first divided laser beam 41 that has returned to the fixed mirror 22 is reflected to the beam splitter 21.

[0040] Movable mirror 23 reflects second divided laser beam 42 toward second folding mirror 27. Second divided laser beam 42 reflected by second folding mirror 27 shifts its optical axis and returns to movable mirror 23. Second divided laser beam 42 that has returned to movable mirror 23 is reflected to beam splitter 21.

[0041] The light receiving unit 28 receives the first divided laser beam 41 and the second divided laser beam 42 combined by the beam splitter 21. Because the second divided laser beam 42 is reflected by the second folding mirror 27, the optical path difference between the first divided laser beam 41 and the second divided laser beam 42 becomes four times the moving distance of the movable mirror 23. This improves the resolution of detecting the position of the movable mirror 23 based on the detection signal of the light receiving unit 28.

[0042] [Effects of the first embodiment] In the interferometer 11 described above, the second divided laser beam 42, which is split by the beam splitter 21 and travels toward the movable mirror 23, is reflected by the movable mirror 23 and then reflected by the second folding mirror 27. The light receiving unit 28 receives the first divided laser beam 41 and the second divided laser beam 42 combined by the beam splitter 21. The optical path difference between the first divided laser beam 41 and the second divided laser beam 42 is four times the moving distance of the movable mirror 23, thereby improving the resolution for detecting the position of the movable mirror 23.

[0043] Furthermore, since the semiconductor laser 25, the beam splitter 21, the first folding mirror 26, the second folding mirror 27, and the light receiving unit 28 are fixed to the frame 29 and formed into a unit, it is easy to adjust the position of these components in the interferometer 11.

[0044] Furthermore, the first folding mirror 26 is a roof mirror that reflects the first divided laser beam 41 with its optical axis shifted, and the second folding mirror 27 is a roof mirror that reflects the second divided laser beam 42 with its optical axis shifted, so the first divided laser beam 41 and the second divided laser beam 42 do not return to the semiconductor laser 25. As a result, the semiconductor laser 25 is prevented from becoming unstable, and optical noise is reduced.

[0045] Furthermore, since the movable mirror 23 is a corner reflector, even if the movable mirror 23 is moved by the moving mechanism 24, the second divided laser beam 42 is reflected in parallel.

[0046] [Modification of the first embodiment] Although the interferometer 11 described above has one second folding mirror 27, multiple second folding mirrors 27 may be provided. For example, as shown in FIG. 4, a third folding mirror 30 may be provided that reflects the second divided laser beam 42 reflected by the second folding mirror 27 and returns it to the second folding mirror 27. The third folding mirror 30 is an example of a second folding mirror. As a result, the optical path difference between the first divided laser beam 41 and the second divided laser beam 42 becomes 8 (4n (n is a natural number)) times the moving distance of the movable mirror 23, further improving the resolution of detecting the position of the movable mirror 23. Note that n corresponds to the number of folding mirrors in the optical path on the movable mirror 23 side, and in this modification, n=2.

[0047] [Second embodiment] The analysis device according to the second embodiment differs from the analysis device 10 according to the first embodiment in the configuration of the interferometer 11. Therefore, the configuration of the interferometer 50 according to the second embodiment will be described below, and descriptions of the configurations of the other analysis devices will be omitted.

[0048] As shown in Figure 5, the interferometer 50 has a first beam splitter 51, a fixed mirror 52, a movable mirror 53, a moving mechanism 54, a semiconductor laser 55, a second beam splitter 56, a first folding mirror 57, a second folding mirror 58, a corner reflector 59, and a light receiving unit 60.

[0049] The fixed mirror 52 is, for example, a corner reflector in which three plane mirrors are arranged at right angles to each other. The fixed mirror 52 is fixed at a constant distance from the first beam splitter 51. The transmitted light from the first beam splitter 51 is reflected by the fixed mirror 52 in a parallel manner.

[0050] The movable mirror 53 is, for example, a corner reflector. The movable mirror 53 is moved by a moving mechanism 54 so that the distance from the first beam splitter 51 varies. Although not shown in detail in the figures, the moving mechanism 54 has a guide that extends parallel to the light reflected by the first beam splitter 51, a carriage that moves along the guide, and an actuator that moves the carriage. The actuator is, for example, a voice coil motor. The movable mirror 53 is mounted on the carriage and moves, thereby varying the distance from the first beam splitter 51.

[0051] The semiconductor laser 55 emits laser light. The laser light is near-infrared light with a wavelength in the range of approximately 800 nm to 2500 nm. The semiconductor laser 55 is located on the opposite side of the first beam splitter 51 (on the left side in FIG. 5 ) across the movable mirror 53. The semiconductor laser 55 is an example of a laser. The laser light is an example of light.

[0052] The second beam splitter 56 is a half mirror that splits the irradiated light into transmitted light that transmits the light and reflected light that reflects the light. A semi-transparent film for laser light is laminated on the second beam splitter 56. The second beam splitter 56 is located between the semiconductor laser 55 and the movable mirror 53. The second beam splitter 56 splits the laser light emitted from the semiconductor laser 55 into transmitted light and reflected light.

[0053] The first folding mirror 57 is, for example, a roof mirror in which two plane mirrors are arranged at a right angle. The first folding mirror 57 reflects the first divided laser beam 61 reflected by the second beam splitter 56 while shifting the optical axis of the first divided laser beam 61.

[0054] The corner reflector 59 is located between the movable mirror 53 and the second beam splitter 56. The corner reflector 59 is mounted on a carriage in the moving mechanism 54. The corner reflector 59 is moved synchronously with the movable mirror 53 by the moving mechanism 54. In other words, when the movable mirror 53 moves away from the first beam splitter 51, the corner reflector 59 also moves away from the first beam splitter 51 and approaches the second beam splitter 56. When the movable mirror 53 approaches the first beam splitter 51, the corner reflector 59 also moves closer to the first beam splitter 51 and moves away from the second beam splitter 56. The corner reflector 59 reflects the second divided laser beam 62 that has passed through the second beam splitter 56, shifting its optical axis. The first divided laser beam 61 is an example of a first divided beam. The second divided laser beam 62 is an example of the second divided beam.

[0055] The second folding mirror 58 is, for example, a roof mirror. The second folding mirror 58 reflects the second split laser beam 62 reflected by the corner reflector 59 while shifting the optical axis of the second split laser beam 62. The position of the second folding mirror 58 is fixed.

[0056] The light receiving section 60 is, for example, a photodiode, which detects the received laser light and outputs a detection signal.

[0057] The following describes the optical path of the laser light in the interferometer 50. Note that the laser light is indicated by a broken line in FIG. The laser beam emitted from the semiconductor laser 55 is split by the second beam splitter 56 into a first divided laser beam 61 and a second divided laser beam 62. The first divided laser beam 61 is a reflected beam that is reflected by the second beam splitter 56. The second divided laser beam 62 is a transmitted beam that is transmitted through the second beam splitter 56.

[0058] The first folding mirror 57 reflects the first divided laser beam 61 toward the second beam splitter 56. The first divided laser beam 61 that has returned to the second beam splitter 56 passes through the second beam splitter 56.

[0059] The corner reflector 59 reflects the second divided laser beam 62 toward the second folding mirror 58. The second divided laser beam 62 reflected by the second folding mirror 58 shifts its optical axis and returns to the corner reflector 59. The second divided laser beam 62 that returned to the corner reflector 59 is reflected toward the second beam splitter 56 and is reflected by the second beam splitter 56.

[0060] The light receiving unit 60 receives the first divided laser beam 61 and the second divided laser beam 62 combined by the second beam splitter 56. Because the second divided laser beam 62 is reflected by the second folding mirror 58, the difference in the optical paths of the first divided laser beam 61 and the second divided laser beam 62 becomes four times the moving distance of the corner reflector 59. Since the movement of the corner reflector 59 is linked to the movement of the movable mirror 53, the resolution of detecting the position of the movable mirror 53 based on the detection signal of the light receiving unit 60 is improved.

[0061] In the interferometer 50 according to the second embodiment, infrared light emitted from the infrared light source 12 is split by the first beam splitter 51 and reflected by the fixed mirror 52 and the movable mirror 53. On the other hand, the laser light emitted from the semiconductor laser 55 does not reach the first beam splitter 51 but is split by the second beam splitter 56. In other words, the interference optical system for infrared light and the optical system for detecting the position of the movable mirror 53 are separated. As a result, the first beam splitter 51 is dedicated to infrared light, so that the loss of light due to the first beam splitter 51 is suppressed, and the S / N ratio of the analytical device 10 is improved.

[0062] [Modification 1 of the second embodiment] 6, the interferometer 50 described above may further include a third folding mirror 70. The third folding mirror 70 is, for example, a roof mirror. The third folding mirror 70 reflects the second split laser beam 62 reflected by the corner reflector 59 while shifting its optical axis.

[0063] The laser beam emitted from the semiconductor laser 55 is split by the second beam splitter 56 into a first divided laser beam 61 and a second divided laser beam 62. The first divided laser beam 61 is a reflected beam that is reflected by the second beam splitter 56. The second divided laser beam 62 is a transmitted beam that is transmitted through the second beam splitter 56.

[0064] The first folding mirror 57 reflects the first divided laser beam 61 toward the second beam splitter 56. The first divided laser beam 61 that has returned to the second beam splitter 56 passes through the second beam splitter 56.

[0065] The corner reflector 59 reflects the second divided laser beam 62 toward the second folding mirror 58. The second divided laser beam 62 reflected by the second folding mirror 58 shifts its optical axis and returns to the corner reflector 59. The second divided laser beam 62 that returned to the corner reflector 59 is reflected toward the third folding mirror 70 and is reflected by the third folding mirror 70.

[0066] The corner reflector 59 reflects the second divided laser beam 62 again toward the second folding mirror 58. The second divided laser beam 62 reflected by the second folding mirror 58 shifts its optical axis and returns to the corner reflector 59. The second divided laser beam 62 that returned to the corner reflector 59 is reflected toward the second beam splitter 56 and is reflected by the second beam splitter 56.

[0067] The light receiving unit 60 receives the first divided laser beam 61 and the second divided laser beam 62 combined by the second beam splitter 56. Because the second divided laser beam 62 is reflected by the second folding mirror 58 and the third folding mirror 70, the difference in the optical paths of the first divided laser beam 61 and the second divided laser beam 62 becomes eight times the moving distance of the corner reflector 59. Because the movement of the corner reflector 59 is linked to the movement of the movable mirror 53, the resolution of detecting the position of the movable mirror 53 based on the detection signal of the light receiving unit 60 is improved.

[0068] [Modification 2 of the Second Embodiment] 7 , the interferometer 50 described above has a first corner reflector 71 and a second corner reflector 72 instead of the corner reflector 59, and may further have a third folding mirror 70. The first corner reflector 71 and the second corner reflector 72 are aligned so as to be in approximately the same position as the second beam splitter 56, and are moved synchronously with the movable mirror 53 by the moving mechanism 54. In other words, when the movable mirror 53 moves away from the first beam splitter 51, the first corner reflector 71 and the second corner reflector 72 also move away from the first beam splitter 51 and closer to the second beam splitter 56. When the movable mirror 53 moves closer to the first beam splitter 51, the first corner reflector 71 and the second corner reflector 72 also move closer to the first beam splitter 51 and away from the second beam splitter 56. The first corner reflector 71 and the second corner reflector 72 each reflect the second split laser beam 62 while shifting its optical axis.

[0069] The second folding mirror 58 faces the first corner reflector 71. The first corner reflector 71 reflects the second divided laser beam 62 toward the second folding mirror 58. The second divided laser beam 62 reflected by the second folding mirror 58 shifts its optical axis and travels toward the second corner reflector 72.

[0070] The third folding mirror 70 faces the second corner reflector 72. The second corner reflector 72 reflects the second divided laser beam 62 toward the third folding mirror 70. The second divided laser beam 62 reflected by the third folding mirror 70 is reflected toward the second corner reflector 72 with its optical axis shifted.

[0071] The laser beam emitted from the semiconductor laser 55 is split by the second beam splitter 56 into a first divided laser beam 61 and a second divided laser beam 62. The first divided laser beam 61 is a reflected beam that is reflected by the second beam splitter 56. The second divided laser beam 62 is a transmitted beam that is transmitted through the second beam splitter 56.

[0072] The first folding mirror 57 reflects the first divided laser beam 61 toward the second beam splitter 56. The first divided laser beam 61 that has returned to the second beam splitter 56 passes through the second beam splitter 56.

[0073] The first corner reflector 71 reflects the second divided laser beam 62 toward the second folding mirror 58. The second divided laser beam 62 reflected by the second folding mirror 58 is reflected toward the second corner reflector 72 with its optical axis shifted. The second divided laser beam 62 reflected by the second corner reflector 72 is reflected toward the third folding mirror 70 and is reflected by the third folding mirror 70.

[0074] The second corner reflector 72 reflects the second divided laser beam 62 again toward the second folding mirror 58. The second divided laser beam 62 reflected by the second folding mirror 58 shifts its optical axis and returns to the first corner reflector 71. The second divided laser beam 62 that returned to the first corner reflector 71 is reflected toward the second beam splitter 56 and is reflected by the second beam splitter 56.

[0075] The light receiving unit 60 receives the first divided laser beam 61 and the second divided laser beam 62 combined by the second beam splitter 56. Because the second divided laser beam 62 is reflected by the first corner reflector 71, the second corner reflector 72, the second turning mirror 58, and the third turning mirror 70, the difference in the optical paths of the first divided laser beam 61 and the second divided laser beam 62 becomes eight times the moving distance of the corner reflector 59. Because the movement of the first corner reflector 71 and the second corner reflector 72 is linked to the movement of the movable mirror 53, the resolution of detecting the position of the movable mirror 53 based on the detection signal of the light receiving unit 60 is improved.

[0076] It should be noted that a gas laser such as a He-Ne laser, a solid-state laser such as a YAG laser, a fiber laser, or a liquid laser such as a dye laser may be used instead of the semiconductor lasers 25 and 55. In each of the above embodiments, the folding mirror may be a roof mirror or a rectangular prism. [Explanation of symbols]

[0077] 10...Analyzer 11,50...Interferometer 12. Infrared light source 13. Sample cell 14. Detection unit 21. Beam splitter 22 Fixed mirror 23. Moving mirror 24...Moving mechanism 25,55... Semiconductor laser (laser) 26. First turning mirror 27. Second folding mirror 28... Light receiving section 29...frame 30···Third folding mirror (second folding mirror)

Claims

1. A laser, a beam splitter that splits the light emitted from the laser into a first split light and a second split light; a fixed mirror that reflects the first divided light; a first return mirror that reflects the first divided light reflected by the fixed mirror; a movable mirror that reflects the second divided light; a second folding mirror that reflects the second divided light reflected by the movable mirror; a moving mechanism that moves the movable mirror so that the distance to the beam splitter varies; an interferometer comprising: a light receiving unit that receives the first divided light and the second divided light that are reflected by the first folding mirror, the fixed mirror, the second folding mirror, and the movable mirror, respectively, and are combined by the beam splitter.

2. the first folding mirror reflects the first divided light beam while shifting its optical axis; 2. An interferometer according to claim 1, wherein said second folding mirror reflects said second split light with its optical axis shifted.

3. 2. The interferometer of claim 1, wherein the laser is a semiconductor laser.

4. 4. The interferometer according to claim 3, wherein the light emitted from the laser is near-infrared light.

5. 5. An interferometer according to claim 3, wherein the beam splitter has a film for infrared light laminated on one side and a film for laser light laminated on the other side.

6. 3. An interferometer according to claim 1, wherein the movable mirror is a corner reflector.

7. 3. The interferometer according to claim 1, wherein the fixed mirror is a corner reflector.

8. Further comprising a frame, 3. The interferometer according to claim 1, wherein the laser, the beam splitter, the first folding mirror, the second folding mirror, and the light receiving section are fixed to the frame to form a unit.

9. an interferometer according to claim 1; an infrared light source that emits infrared light; a sample cell; An analytical device comprising a detection unit, the beam splitter splits the infrared light into a first split infrared light and a second split infrared light; the fixed mirror reflects the first split infrared light, the movable mirror reflects the second split infrared light, the sample cell transmits the first split infrared light and the second split infrared light combined by the beam splitter; The detection unit is an analytical device that receives the first divided infrared light and the second divided infrared light that have passed through the sample cell.

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