WO2017119389A1 - フーリエ変換型分光装置 - Google Patents
フーリエ変換型分光装置 Download PDFInfo
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- WO2017119389A1 WO2017119389A1 PCT/JP2016/089069 JP2016089069W WO2017119389A1 WO 2017119389 A1 WO2017119389 A1 WO 2017119389A1 JP 2016089069 W JP2016089069 W JP 2016089069W WO 2017119389 A1 WO2017119389 A1 WO 2017119389A1
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Definitions
- the present invention relates to a Fourier transform spectrometer.
- FT-IR Fourier transform infrared spectroscopy
- FT-CARS Fourier transform coherent anti-Stokes Raman scattering
- light emitted from a light source is demultiplexed into reference light propagating through a first arm having a fixed mirror and scanning light propagating through a second arm having a movable mirror by a beam splitter.
- An interference wave is generated using a Michelson interferometer that combines a reference beam reflected by a fixed mirror of one arm and a scanning beam reflected by a movable mirror of a second arm by a beam splitter, and the interference wave is detected. Irradiate objects.
- the scanning mirror is delayed with respect to the reference light by moving the movable mirror in one direction and changing the optical path length of the second arm.
- An interferogram is generated, and a molecular vibration spectrum is obtained by Fourier-transforming the interferogram.
- FT-IR generates an interferogram of transmitted light generated by interference waves passing through the test object, and obtains a molecular vibration spectrum of the test object by Fourier transforming the interferogram.
- FT-CARS spectroscopy generates an interferogram of anti-Stokes light emitted by coherent anti-Stokes Raman scattering generated in a test object by being irradiated with interference waves, and Fourier-transforms the interferogram. A molecular vibration spectrum of the test object is obtained.
- a Michelson interferometer is used to generate the interferogram by delaying the scanning light with respect to the reference light, and the interferogram is Fourier transformed to generate molecular vibrations. A spectrum is obtained.
- the optical path length difference between the first arm and the second arm is changed by moving the position of the movable mirror during measurement, so that an interferogram is generated.
- the generation speed of the interferogram is limited by the moving speed of the movable mirror and it is difficult to improve the acquisition speed of the molecular vibration spectrum.
- an object of the present invention is to provide a Fourier transform type spectroscopic device capable of improving the acquisition speed of a molecular vibration spectrum.
- the Fourier transform type spectroscopic device of the present invention includes a beam splitter that demultiplexes light emitted from a light source into reference light and scanning light, and a first mirror that reflects the reference light by a first mirror and re-enters the beam splitter.
- One arm and a second arm that reflects the scanning light by a second mirror and re-enters the beam splitter, and combines the reference light and the scanning light that re-enter the beam splitter to interfere with each other.
- An interferometer that generates a wave
- a photodetector that detects the intensity of detected light emitted from the object irradiated with the interference wave, and the interference wave obtained by repeatedly irradiating the object
- a spectroscopic spectrum generation unit configured to generate an interferogram based on a plurality of the intensities of the detected light and Fourier-transform the interferogram
- the second arm includes the beam splitter and
- a scanning mirror is disposed on the optical path of the scanning light between the second mirrors, and the scanning light is delayed or preceded by the reference light according to a rotation angle from an initial position of the scanning mirror.
- the Fourier transform type spectroscopic device of the present invention changes the optical path length of the scanning light by rotating the scanning mirror, and delays or precedes the scanning light with respect to the reference light according to the rotation angle from the initial position of the scanning mirror. Compared to the case where the position of the movable mirror is moved and the scanning light is delayed with respect to the reference light as in the conventional Fourier transform spectrometer, the scanning mirror can be moved at a higher speed, and the molecular vibration spectrum acquisition speed Can be improved.
- FIG. 9A is a graph showing the temporal change of the molecular vibration spectrum obtained by measuring the change of the mixed state
- FIG. 9B shows the temporal change of the concentration of each liquid obtained from the temporal change of the molecular vibration spectrum. It is a graph to show. It is explanatory drawing which shows the measurement state at the time of making the bead which flows in a microchannel into a measuring object using the Fourier-transform-type spectrometer which concerns on embodiment of this invention, and FIG. 10A was seen from the side of the microchannel FIG. 10B is a view as seen from above the microchannel.
- FIG. 11A is an interferogram generated when the beads flowing in the microchannel are measured
- FIG. 11B is a molecular vibration spectrum obtained from the interferogram.
- the Fourier transform spectrometer 1 of the embodiment of the present invention includes a light source 2, an interferometer 3, and a compensator 4.
- PC personal computer
- the Fourier transform type spectroscopic device 1 emits the anti-Stokes light 15 as the detected light emitted by the coherent anti-Stokes Raman scattering generated in the test object 7 when the interference wave 14 generated by the interferometer 3 is irradiated.
- This is a Fourier transform type coherent anti-Stokes Raman scattering (FT-CARS) spectrometer that generates an interferogram using an interferometer 3 and Fourier transforms the interferogram using a PC 12 to obtain a molecular vibration spectrum.
- FT-CARS Fourier transform type coherent anti-Stokes Raman scattering
- the light source 2 is a laser light source that emits ultra-short pulse laser light with high coherency, and is a pulse laser that emits a light pulse 13 having a broadband spectrum at a predetermined repetition frequency.
- the light source 2 is a Ti: Sapphire femtosecond laser (product name: Synergy, which emits an optical pulse 13 having a center frequency of 792 nm, a bandwidth of 47 nm, and a pulse width of 17 fs at a repetition frequency of 75 MHz. (Registered trademark)).
- various pulse lasers solid laser, fiber laser, dye laser, etc. having a high repetition frequency can be used.
- the interferometer 3 includes a beam splitter 23, a first arm 21 having a dispersion lens 24 and a first mirror 25, and a second arm 22 having a resonant scanner 26, a condenser lens 27, and a second mirror 28. Yes.
- the interferometer 3 demultiplexes the light pulse 13 emitted from the light source 2 into reference light propagating through the first arm 21 and scanning light propagating through the second arm 22, and the first arm 21.
- the reference light reflected by the first mirror 25 and the scanning light reflected by the second mirror 28 of the second arm 22 are re-incident on the beam splitter 23, and the reference light and scanning light re-entered on the beam splitter 23 are It is a Michelson interferometer that generates an interference wave 14 by multiplexing. Both the reference light and the scanning light demultiplexed by the beam splitter 23 are optical pulses similar to the optical pulse 13.
- a polarization beam splitter can be used in addition to such a polarization-independent beam splitter.
- the first arm 21 includes a dispersion lens 24 on the optical path of the reference light between the beam splitter 23 and the first mirror 25 so that the reference light passes through the dispersion lens 24 and enters the first mirror 25.
- the dispersion lens 24 is disposed at the same distance as the focal length f of the dispersion lens 24 from the first mirror 25.
- the dispersion lens 24 is a lens similar to a condenser lens 27 of the second arm 22 described later.
- the dispersion lens 24 causes the reference light to generate a group velocity dispersion similar to the group velocity dispersion generated in the scanning light when the scanning light passes through the condenser lens 27.
- the pulse shapes of the reference light and the scanning light can be made uniform.
- the intensity of anti-Stokes light described below can be increased, and a molecular vibration spectrum can be obtained with higher sensitivity.
- the first arm 21 is preferably provided with a dispersion lens 24, but may not be provided with a dispersion lens.
- the first mirror 25 is a plane mirror and is arranged perpendicular to the light beam of the reference light. Therefore, the reference light enters the mirror surface of the first mirror 25 perpendicularly and is reflected, and the reflected reference light exits perpendicularly from the mirror surface and passes through the same path as that at the time of incidence in the direction opposite to that at the time of incidence. Therefore, in the first arm 21, when the reference light demultiplexed by the beam splitter 23 is reflected by the first mirror 25, it passes through the same path in the reverse direction and reenters the beam splitter 23.
- the second arm 22 is configured such that the scanning light demultiplexed by the beam splitter 23 is reflected by the scanning mirror 26 b of the resonant scanner 26, passes through the condenser lens 27, and enters the second mirror 28.
- a scanning mirror 26b is attached to one end of a rotating shaft 26a, and the rotating shaft 26a is rotated by a rotation control unit (not shown in FIG. 1) connected to the other end of the rotating shaft 26a.
- the scanning mirror 26b resonates with the rotation of the rotating shaft 26a.
- the scanning mirror 26b periodically moves at a predetermined deflection angle.
- the resonant scanner 26 is a CRS manufactured by Cambridge Technology, in which the scanning mirror 26b vibrates at 8 kHz.
- other types of resonant scanners may be used.
- the vibration frequency of the scanning mirror 26b can be appropriately selected according to the parameters (repetition frequency, pulse width, etc.) of the optical pulse 13 to be used, but about 10 kHz is preferable.
- the resonant scanner 26 having the scanning mirror 26 b that vibrates at a vibration frequency of about 76 kHz is used.
- the resonant scanner 26 is arranged such that the scanning light demultiplexed by the beam splitter 23 always hits a portion where the displacement due to the resonance vibration of the scanning mirror 26b is large, in this case, near the outer edge of the scanning mirror 26b during the resonance vibration. Is arranged.
- the scanning mirror 26b of the resonant scanner 26 is disposed on the optical path of the scanning light, and the position closest to the beam splitter 23 (position A of the scanning mirror 26b shown by a broken line in FIG. 1) is set as an initial position of the rotating shaft 26a. It is arranged so as to be displaced to a position farthest from the beam splitter 23 (position B of the scanning mirror 26b shown by a solid line in FIG. 1) by the resonance vibration caused by the rotation, and then return to the initial position. Thus, the scanning mirror 26b periodically moves between the position A and the position B.
- the rotation angle is the rotation angle of the rotation shaft 26a when the scanning mirror 26b rotates.
- the rotation shaft 26a rotates in the reverse direction, the rotation angle of the scanning mirror 26b decreases, and the optical path length of the scanning light also decreases, so that the scanning mirror 26b returns to the position A that is the initial position.
- the optical path length of the scanning light periodically changes.
- the change width of the optical path length of the scanning light when the scanning mirror 26b changes between the position A and the position B is about 1 mm.
- the change width of the optical path length can be adjusted.
- the scanning mirror 26b since the scanning mirror 26b resonates at a frequency of 8 kHz, the scanning mirror 26b performs a periodic motion that reciprocates between the position A and the position B at a period of 125 ⁇ s.
- the scanning mirror 26b and the condensing lens 27 of the resonant scanner 26, and the condensing lens 27 and the second mirror 28 are separated by the same distance as the focal length f of the condensing lens 27, respectively. 27 and the second mirror 28 form a so-called 4f optical system.
- the condensing lens 27 refracts the incident scanning light, condenses the scanning light on the mirror surface of the second mirror 28, which is a plane mirror, and makes it incident vertically, and is reflected by the second mirror 28 and re-entered. Is refracted and condensed on the scanning mirror 26b.
- the angle between the scanning mirror 26b and the light beam of the scanning light changes according to the rotation angle of the scanning mirror 26b, and the direction in which the scanning light is reflected by the scanning mirror 26b also changes. Therefore, the condensing lens 27 and the second mirror 28 are selected in size and adjusted in position so that the scanning light is incident on the second mirror 28 vertically regardless of the rotation angle of the scanning mirror 26b. Yes.
- the condenser lens 27 (dispersion lens 24) is a circular spherical lens having a focal length of 100 mm and a diameter of 2 inches.
- the first mirror 25 and the second mirror 28 are circular mirrors having a diameter of 2 inches.
- the optical path length of the reference light of the first arm 21 (the optical path length of the reciprocating reference light from the beam splitter 23 to the first mirror 25) and the scanning mirror 26b of the resonant scanner 26 are in the initial position. Arrangement of components of the first arm 21 and the second arm 22 so that the optical path length of the scanning light of the second arm 22 (the optical path length of the reciprocating scanning light from the beam splitter 23 to the second mirror 28) becomes equal. Has been adjusted.
- the scanning mirror 26b when the scanning mirror 26b is in the initial position, the scanning light propagating through the second arm 22 reaches the beam splitter 23 without being delayed by the reference light propagating through the first arm 21, and the reference light and the scanning light are Since both are demultiplexed from the same optical pulse 13, they are superimposed and strengthened to generate an interference wave 14.
- the interference wave 14 is a collinear optical pulse in which the scanning light delayed on the same optical axis as the reference light is aligned and superimposed with the scanning light delayed on the reference light.
- the delay of the scanning light with respect to the reference light increases according to the rotation angle of the scanning mirror 26b because the optical path length of the scanning light becomes longer according to the rotation angle of the scanning mirror 26b and the optical path length difference between the reference light and the scanning light becomes larger. growing.
- the scanning mirror 26b reaches the position B and the rotation angle of the scanning mirror 26b becomes maximum, the optical path length difference between the reference light and the scanning light becomes maximum, and the delay of the scanning light with respect to the reference light also becomes maximum.
- the rotation shaft 26a rotates in the opposite direction, the rotation angle of the scanning mirror 26b decreases, the scanning mirror 26b moves from the position B to the position A, the optical path length of the scanning light decreases, and the optical path lengths of the reference light and the scanning light Since the difference is small, the delay of the scanning light with respect to the reference light is also small. Since the scanning mirror 26b resonates and oscillates between the position A and the position B due to the rotation of the rotating shaft 26a, such a process is repeated.
- the interferometer 3 generates the interference wave 14 in which the scanning light is delayed with respect to the reference light in accordance with the rotation angle from the initial position of the scanning mirror 26b.
- the compensator 4 is designed so as to compensate the group velocity dispersion of the interference wave 14 and to minimize the pulse width of the interference wave 14 at the position of the test object 7, that is, when the test object 7 is irradiated. ing.
- the compensator 4 is a so-called chirp mirror pair, and includes a first chirp mirror 4a and a second chirp mirror 4b parallel to the first chirp mirror 4a.
- the first chirp mirror 4a and the second chirp mirror 4b are arranged so that their mirror surfaces face each other, and the interference wave 14 incident from one end of the compensator 4 is generated between the first chirp mirror 4a and the second chirp mirror 4b.
- the first chirp mirror 4a and the second chirp mirror 4b only need to be arranged with an interval of about several centimeters. In the present embodiment, the first chirp mirror 4a and the second chirp mirror 4b are arranged with an interval of about 2 cm.
- the compensator 4 compensates for the group velocity dispersion of the interference wave 14 and reduces the pulse width.
- the compensator 4 is not particularly limited as long as the pulse width can be reduced by compensating for the group velocity dispersion of the interference wave 14, and an element that can compensate for other types of group velocity dispersion can be used.
- a pair of diffraction gratings, a photonic crystal fiber (Photonic Crystal Fiber: PCF), a chirped FBG (Chirped Fiber Bragg Grating), or the like may be used as the compensator 4.
- PCF Photonic Crystal Fiber
- FBG Carbon Fiber Bragg Grating
- a compensator 4 that compensates for higher order (third order or higher) dispersion such as a prism pair and a grism pair may be used. preferable.
- the interference wave 14 compensated for the group velocity dispersion by the compensator 4 passes through the long pass filter 5, is condensed by the first objective lens 6, and is irradiated on the test object 7.
- the long-pass filter 5 has a cut-off wavelength set so as not to transmit light at the bottom wavelength side in the spectrum of the interference wave 14. Thereby, since the light having the same wavelength as the anti-Stokes light 15 generated in the test object 7 to be described later can be cut by the long pass filter 5, the anti-Stokes light 15 can be easily detected, and the molecular vibration is more reliably performed. A spectrum can be obtained.
- the long pass filter 5 has a cutoff wavelength set to 750 nm.
- the test object 7 is arranged at the focal position of the first objective lens 6.
- the reference light first hits the test object 7.
- light with a certain frequency included in the reference light becomes pump light
- light with a certain frequency different from the pump light becomes Stokes light.
- the same vibration frequency as the frequency difference between the pump light and Stokes light is obtained.
- a molecular vibration having is induced.
- the scanning light delayed with respect to the pulse of the reference light hits the test object 7, the scanning light and the induced molecular vibration act, and the frequency of the light contained in the scanning light is shifted and scattered light. Is released.
- the scattered light includes anti-Stokes light 15 having a frequency increased by the frequency of molecular vibration induced by the reference light with respect to the frequency of the scanning light, and molecules induced by the reference light with respect to the frequency of the scanning light. Stokes light whose frequency is reduced by the frequency of vibration is included.
- a molecular vibration spectrum can be obtained by generating an interferogram of and performing Fourier transform on the interferogram.
- the reference light is a broadband optical pulse and has a wide range of wavelength components
- various molecular vibrations are induced by the combination of pump light and Stokes light of various frequencies.
- Corresponding anti-Stokes light 15 and Stokes light can be emitted. Therefore, a molecular vibration spectrum in a wide wavenumber region can be obtained by generating an interferogram once.
- the scanning light when the scanning light precedes the reference light, the scanning light first strikes the object 7 to induce molecular vibration. Thereafter, the reference light strikes the test object 7, and anti-Stokes light 15 and Stokes light are emitted.
- the interferometer 3 changes the time that the scanning light precedes and changes the time difference between the scanning light and the reference light to generate an anti-Stokes light 15 or an interferogram of the Stokes light.
- the anti-Stokes light 15 and the Stokes light are detected by the second objective lens 8 arranged so that the focal position overlaps the focal position of the first objective lens 6 and faces the first objective lens 6 across the focal position.
- the light is collimated together with the interference wave 14 that has passed through the object 7 and enters the short pass filter 9.
- the cut-off wavelength of the short pass filter 9 is set to a short wavelength equal to or shorter than the cut-off wavelength of the long pass filter 5. Since most of the wavelength components of the interference wave 14 that are not longer than the cutoff wavelength of the long pass filter 5 are cut by the long pass filter 5, there are few wavelength components that can pass through the short pass filter 9. In addition, since the Stokes light is obtained by shifting the light included in the scanning light to the low frequency side, there are many wavelength components having a longer wavelength than the interference wave 14 obtained by combining the scanning light and the reference light. Similar to the interference wave 14, there are few wavelength components that can pass through the short pass filter 9. Therefore, the short pass filter 9 can remove most of the interference wave 14 and the Stokes light. In this embodiment, the short-pass filter 9 has a cutoff wavelength set to 750 nm.
- the anti-Stokes light 15 that has passed through the short pass filter 9 is detected by the photodetector 10, and the intensity of the anti-Stokes light 15 is converted into an electric signal.
- the electric signal having the intensity of the anti-Stokes light 15 passes through the low-pass filter 11 connected to the photodetector 10 through the conducting wire 16.
- the low pass filter 11 removes high frequency noise.
- the electric signal from which the noise has been removed is sent to the PC 12 connected to the low-pass filter 11 via the conductor 17.
- the avalanche photodetector APD120A / M manufactured by Thorlabs is used as the photodetector 10.
- another type of photodetector such as a photomultiplier PIN photodiode may be used. .
- the PC 12 serving as the spectral spectrum generation unit is equipped with a digitizer board, and a conducting wire 17 is connected to the digitizer board.
- the electrical signal having the intensity of the anti-Stokes light 15 transmitted from the low-pass filter 11 is converted from analog to digital (A / D) by the digitizer board, and is stored in the storage device of the PC 12 as electronic data together with the detection time (not shown in FIG. 1). ).
- ATS9440 manufactured by AlzarTech is used as a digitizer board.
- the detection time and the intensity of the anti-Stokes light 15 emitted from the test object 7 irradiated with the interference wave 14. are sequentially stored as electronic data.
- interferogram electronic data in which the intensity values of the anti-Stokes light 15 are arranged at the same time interval as the repetition period of the optical pulse 13 is generated.
- the interferogram of the anti-Stokes light 15 is generated based on the intensity of the anti-Stokes light 15.
- the electronic data of the interferogram does not need to store the detection time and the intensity of the anti-Stokes light 15 every time the optical pulse 13 is generated, and the number of data is increased by increasing the detection interval of the anti-Stokes light 15. May be thinned out as appropriate, or may be oversampled with a short detection interval.
- the scanning mirror 26b reciprocates between the initial position and the position B on the optical path of the scanning light, and in the region other than the initial position and the position B, the speed of the scanning mirror 26b is almost equal. It is constant. As a result, in the region other than the initial position and the vicinity of the position B, the amount of change in the optical path length of the scanning light per unit time is substantially constant, and the optical path length of the scanning light changes linearly with respect to time. It can be considered that the delay of the scanning light with respect to the light also changes linearly with respect to time.
- the speed of the scanning mirror 26b changes.
- the amount of change in the optical path length of the scanning light per unit time changes according to the speed, and the optical path length of the scanning light does not change linearly with respect to time.
- the delay of the scanning light with respect to the reference light also does not change linearly with respect to time.
- the interferogram generated by the above method also includes the intensity of the anti-Stokes light 15 detected in the time domain where the delay of the scanning light with respect to the reference light does not change linearly with respect to time. Therefore, when the molecular vibration spectrum is acquired by performing Fourier transform on the interferogram, the acquired molecular vibration spectrum is distorted.
- the optical path length of the scanning light changes linearly with respect to time even in the vicinity of the initial position and position B, and the delay time of the scanning light with respect to the reference light changes linearly with respect to time.
- the time axis is corrected.
- the Fourier transform spectroscopic device 1 includes a light source 50 that emits CW (continuous wave) laser light 54 and the CW laser light 54 superimposed on the same optical axis as the optical pulse 13 to interferometer 3. Is further provided with a beam splitter 51 that enters the beam, a beam splitter 52 that separates the interference wave 55 of the CW laser light 54 emitted from the interferometer 3, and a photodetector 53 that detects the interference wave 55 and converts it into an electrical signal. ing.
- CW continuous wave
- the light source 50 is a QLDaser QLD1061 that emits CW laser light having a wavelength of 1064 nm.
- the photodetector 53 is connected to the digitizer board of the PC 12 through the conducting wire 56, and sends an electric signal having the intensity of the interference wave 55 to the digitizer board.
- the electrical signal is A / D converted into digital data.
- the detection time and the intensity of the interference wave 55 are sequentially stored at the repetition period of the optical pulse 13. In this way, an interferogram of the interference wave 55 is generated.
- PDA10CF-EC manufactured by Thorlabs is used as the photodetector 53, but other general photodetectors can be used.
- the interferogram of the interference wave 55 is shaped like a sine wave whose intensity changes periodically with respect to time.
- the speed of the scanning mirror 26b is constant, and the optical path length difference changes linearly with respect to time, so the intensity frequency is constant.
- the speed of the scanning mirror 26b changes as described above, the optical path length difference changes nonlinearly with respect to time, and the intensity frequency changes.
- the optical path length difference can be corrected so as to change linearly.
- the delay time of the scanning light with respect to the reference light is also increased in time near the initial position and position B.
- the time axis is corrected so as to change linearly with respect to.
- the interferogram of the anti-Stokes light 15 can also be corrected by using the interference wave 55 as a sampling clock and digitizing the electric signal of the anti-Stokes light 15.
- the delay of the scanning light with respect to the reference light in the interference wave 14 generated by the interferometer 3 changes periodically according to the rotation angle from the initial position of the scanning mirror 26b of the resonant scanner 26, and becomes the maximum in a half cycle. Therefore, the molecular vibration spectrum of the test object 7 can be acquired by taking out the electronic data of the interferogram corresponding to a half cycle of the change in the rotation angle of the scanning mirror 26b and Fourier-transforming the electronic data of the interferogram.
- a fast Fourier transform program in which interferogram electronic data is stored in a storage device of the PC 12 is executed by a processor (not shown in FIG. 1) of the PC 12, and fast Fourier transform is performed to obtain a molecular vibration spectrum.
- Electronic data is stored in the storage device of the PC 12 and acquired.
- the PC 12 may include display means for displaying the acquired molecular vibration spectrum.
- the electric signal having the intensity of the anti-Stokes light 15 is digitized using a digitizer board mounted on the PC 12, but a digitizer is prepared separately from the PC 12, and the intensity of the anti-Stokes light 15 is obtained by the digitizer.
- the electrical signal may be digitized.
- the electronic data of the interferogram is first Fourier transformed by the fast Fourier transform program stored in the storage device of the PC 12, but hardware such as a circuit specialized for Fourier transform operation is prepared,
- the electronic data of the interferogram may be Fourier transformed by hardware.
- the present invention is not limited to this, and the position farthest from the beam splitter 23 (shown in FIG. 1).
- the position B) of the scanning mirror 26b indicated by the solid line is the initial position of the scanning mirror 26b, the optical path length of the reference light of the first arm 21, and the optical path of the scanning light of the second arm 22 when the scanning mirror 26b is at the initial position. You may make it arrange
- the interferometer 3 when the scanning mirror 26b is displaced from the initial position, the optical path length of the scanning light is shortened, and the scanning light reaches the beam splitter 23 before the reference light. Therefore, the interferometer 3 generates the interference wave 14 in which the scanning light precedes the reference light according to the rotation angle from the initial position of the scanning mirror 26b.
- an interferogram is created using the anti-Stokes light 15 as the scattered light emitted from the test object 7 and the molecular vibration spectrum is acquired has been described, but the present invention is not limited thereto. Instead, an interferogram may be created using Stokes light as scattered light emitted from the test object 7, and the interferogram may be Fourier transformed to obtain a molecular vibration spectrum.
- a short-pass filter 9 having a cutoff wavelength set to 850 nm is disposed at a position where the long-pass filter 5 shown in FIG. 1 is disposed, and a cutoff wavelength is disposed at a position where the short-pass filter 9 is disposed.
- the long pass filter 5 set to 850 nm is arranged.
- the short-pass filter 9 prevents the light at the bottom of the long wavelength side in the spectrum of the interference wave 14 from being transmitted, and cuts light having the same wavelength as the Stokes light generated in the test object 7.
- the long-pass filter can remove most of the interference wave 14 that has passed through the test object 7 and the anti-Stokes light 15 that is emitted from the test object 7 and has a shorter wavelength than the interference wave 14.
- the Stokes light emitted from the test object 7 can be detected by the photodetector 10, an interferogram of the Stokes light can be generated, and a molecular vibration spectrum can be acquired from the Stokes light.
- the present invention is not limited to this, and the optical path length of the reference light of the first arm 21 may be changed to delay the scanning light with respect to the reference light.
- the configuration of the first arm 21 is the same as the configuration of the second arm 22. That is, the first arm 21 is replaced with the dispersion lens 24 and the first mirror 25 and includes the same resonant scanner, condenser lens, and mirror as the second arm 22 in the same arrangement as the second arm 22. . In such a first arm 21, this mirror is the first mirror.
- the first arm 21 is the initial position of the scanning mirror. Further, the optical path length of the reference light when the scanning mirror of the first arm 21 is at the initial position, and the optical path length of the scanning light when the scanning mirror 26b (second scanning mirror) of the second arm 22 is at the initial position, The first arm 21 and the second arm 22 are adjusted so as to be equal.
- the reference light propagating through the first arm 21 reaches the beam splitter 23 earlier than at the initial position, and propagates through the second arm 22.
- the scanning light to reach the beam splitter 23 later than at the initial position, and the delay of the scanning light with respect to the reference light becomes larger than in the above embodiment. This delay is twice as much as the maximum in the above embodiment. Therefore, the molecular vibration spectrum can be measured with higher spectral resolution.
- the configuration of the first arm 21 is not necessarily the same as that of the second arm 22, and may be the same as that of the second arm 22A, the second arm 22B, and the second arm 22C described later. Also in this case, in the first arm 21, it is preferable to adjust each component so that when the scanning mirror rotates, the reference light reaches the beam splitter 23 earlier than when it is at the initial position.
- the Fourier transform spectroscopic device 1 of the present embodiment splits the light pulse 13 of the pulsed laser light emitted from the light source 2 into reference light and scanning light.
- the interferometer 3 is configured to generate the interference wave 14 by combining the reference light and the scanning light re-entering the beam splitter 23.
- the Fourier transform spectrometer 1 of the present embodiment includes a photodetector 10 that detects the intensity of the anti-Stokes light 15 (detected light) emitted from the test object 7 irradiated with the interference wave 14, and the interference wave 14. Generates an interferogram based on the intensities of the plurality of anti-Stokes lights 15 obtained by repeatedly irradiating the test object 7 while changing the delay time of the scanning light with respect to the reference light, and Fourier-transforms the interferogram A spectral spectrum generation unit (PC12) is provided.
- PC12 spectral spectrum generation unit
- the second arm 22 is provided with the scanning mirror 26b of the resonant scanner 26 on the optical path of the scanning light between the beam splitter 23 and the second mirror 28.
- the scanning light is configured to be delayed with respect to the reference light according to the rotation angle from the initial position.
- the Fourier transform spectroscopic device 1 of the present embodiment changes the optical path length of the scanning light by rotating the scanning mirror 26b by the rotation of the rotation shaft 26a, and scans according to the rotation angle from the initial position of the scanning mirror 26b. Since the light is delayed with respect to the reference light, the rotation shaft 26a is rotated as compared with the case where the scanning light is delayed with respect to the reference light by moving the position of the movable mirror as in the conventional Fourier transform type spectroscopic device. Therefore, the scanning mirror 26b can be moved at a higher speed, and the acquisition speed of the molecular vibration spectrum can be improved.
- the Fourier transform spectrometer 1 of the present embodiment delays the scanning light with respect to the reference light due to the displacement of the scanning mirror 26b due to resonance vibration, it is faster than the conventional Fourier transform spectrometer.
- the optical path length of the scanning light can be changed to improve the acquisition speed of the molecular vibration spectrum.
- the Fourier transform spectroscopic device 1 since the Fourier transform spectroscopic device 1 repeatedly generates an interferogram using the periodic motion caused by the resonant vibration of the scanning mirror 26b, the conventional Fourier transform spectroscopic device that needs to repeatedly accelerate and stop the movable mirror. Compared to the above, the time required for acceleration and stop can be shortened, and the acquisition speed of the molecular vibration spectrum can be further improved particularly when the molecular vibration spectrum of the test object 7 is continuously acquired.
- the Fourier transform spectroscopic device 1 of the present embodiment allows the scanning light demultiplexed by the beam splitter 23 to enter the vicinity of the outer edge of the scanning mirror 26b, thereby reducing the optical path length difference between the reference light and the scanning light.
- the spectral resolution can be improved.
- the interferometer 3A of the Fourier transform type spectroscopic device 1A includes a beam splitter 23, The first arm 21 ⁇ / b> A having one mirror 25 and the second arm 22 ⁇ / b> A having a resonant scanner 26, a curved mirror 30, and a second mirror 28 similar to the Fourier transform type spectroscopic device 1 are included.
- the first mirror 25 is a plane mirror and is arranged so that the mirror surface is perpendicular to the optical path of the reference light demultiplexed from the optical pulse 13 by the beam splitter 23. Therefore, in the first arm 21A, the reference light vertically enters the first mirror 25, and the reference light reflected by the first mirror reenters the beam splitter 23 through the same path in the reverse direction.
- the second arm 22A is configured such that the scanning light demultiplexed by the beam splitter 23 is reflected by the scanning mirror 26b of the resonant scanner 26, reflected by the curved mirror 30, and incident on the second mirror 28.
- the resonant scanner 26 is arranged in the same manner as in the above embodiment, and the scanning mirror 26b is located closest to the beam splitter 23 on the optical path of the scanning light (scanning mirror 26b indicated by a broken line shown in FIG. 2).
- the position A) is an initial position, and is periodically moved between the position farthest from the beam splitter 23 (position B of the scanning mirror 26b shown by the solid line in FIG. 2).
- the distance between the beam splitter 23 and the scanning mirror 26b changes according to the rotation angle of the scanning mirror 26b from the initial position, and as a result, the optical path length of the scanning light changes.
- the scanning mirror 26b, the curved mirror 30, and the second mirror 28 are arranged such that the second mirror 28 is disposed adjacent to the scanning mirror 26b, and the curved mirror 30 is opposed to the scanning mirror 26b and the second mirror 28. Between the scanning mirror 26b and the curved mirror 30, and between the curved mirror 30 and the second mirror 28, the same distance as the focal length f of the curved mirror 30 is arranged.
- the curved mirror 30 reflects the incident scanning light and makes the scanning light incident perpendicularly on the mirror surface of the second mirror 28 which is a plane mirror.
- the curved mirror 30 and the second mirror 28 are configured so that the scanning light reflected by the scanning mirror 26b is reflected by the curved mirror 30 and enters the second mirror 28 vertically regardless of the rotation angle of the scanning mirror 26b.
- the size is selected and the position is adjusted.
- the second arm 22A re-enters the beam splitter 23 through the same path in the reverse direction. Incident.
- the optical path length of the reference light of the first arm 21A is equal to the optical path length of the scanning light of the second arm 22A when the scanning mirror 26b is in the initial position. The arrangement of the constituent elements of the first arm 21A and the second arm 22A is adjusted.
- the interferometer 3A when the scanning mirror 26b of the resonant scanner 26 is in the initial position (position A), the reference light propagating through the first arm 21 and the scanning propagating through the second arm 22 are scanned.
- the light simultaneously reaches the beam splitter 23 and overlaps to generate an interference wave 14, and then scans the reference light according to the rotation angle of the scanning mirror 26 b (the optical path length difference between the reference light and the scanning light).
- the light is delayed and the scanning light is overlapped with the reference light in a delayed state, and an interference wave 14 that is a collinear optical pulse is generated.
- the interferometer 3A like the interferometer 3 of the above embodiment, generates the interference wave 14 in which the scanning light is delayed with respect to the reference light according to the rotation angle from the initial position of the scanning mirror 26b. Generate.
- the scanning light is incident on the second mirror 28 by using the curved mirror 30 without using the condensing lens 27, so that the second arm 22A has a path on the scanning light path.
- Modification 1 has a configuration for correcting the time axis of the interferogram of the anti-Stokes light 15 similar to that in the above embodiment, and the same method is used. The time axis of the interferogram of the anti-Stokes light 15 is corrected.
- the interferometer 3B of the Fourier transform type spectroscopic device 1B includes a beam splitter 23, a dispersion It comprises a first arm 21B having lenses 33a and 33b and a first mirror 34, and a second arm 22B having a diffractive optical element 36, a condenser lens 37, a polygon scanner 38, and a second mirror 35.
- the first arm 21B is configured such that the reference light passes through the dispersion lenses 33a and 33b and enters the first mirror 34.
- the dispersion lenses 33a and 33b are lenses similar to the condensing lens 37 of the second arm 22B described later, and are disposed on the optical path of the reference light.
- the first arm 21B since the scanning light passes through the condenser lens 37 twice before reaching the second mirror 35 from the beam splitter 23, the first arm 21B includes two dispersion lenses 33a and 33b. ing.
- the dispersion lenses 33a and 33b cause the reference light to generate group velocity dispersion similar to the group velocity dispersion generated in the scanning light by allowing the scanning light to pass through the condenser lens 37 twice, and the pulses of the reference light and the scanning light.
- the shape can be aligned.
- Such dispersion lenses 33a and 33b are arranged with an interval twice as large as the focal length f of the dispersion lens 33a, that is, with a distance 2f.
- the first mirror 34 is disposed at the same distance as the focal length f of the dispersion lens 33b from the dispersion lens 33b, and the dispersion lens 33a, the dispersion lens 33b, and the first mirror 34 are so-called.
- the 4f optical system is configured.
- the dispersive lens 33a and the dispersive lens 33b are only required to be spaced apart by 2f, and the dispersive lens 33a, the dispersive lens 33b, and the first mirror 34 do not need to form a 4f optical system.
- the first arm 21B preferably includes two dispersion lenses 33a and 33b. However, the first arm 21B may not include the dispersion lens and may include only one dispersion lens.
- the first mirror 34 is a plane mirror and is disposed perpendicular to the light beam of the reference light emitted from the beam splitter 23, and the reference light is incident on the mirror surface perpendicularly. Therefore, in the first arm 21 ⁇ / b> B, when the reference light is reflected by the first mirror 34, it passes through the same path in the reverse direction and reenters the beam splitter 23.
- the scanning light diffracted by the diffractive optical element 36 is condensed by the condensing lens 37 onto the scanning mirror 38b of the polygon scanner 38, reflected by the scanning mirror 38b, and the scanning light is re-applied to the condensing lens 37.
- the light is incident and condensed on the diffractive optical element 36 by the condenser lens 37.
- the scanning light condensed on the diffractive optical element 36 is combined and incident on the second mirror 35.
- the diffractive optical element 36 is a plate-like diffraction grating in which, for example, about 600 grooves per mm are formed on the surface of a metal plate, the scanning light is diffracted and split into light of each wavelength component.
- the scanning light a plurality of wavelength components having different wavelengths included in the scanning light, which is an optical pulse, are separated for each wavelength to become light of each wavelength component, and light of each wavelength component is light that is one-dimensionally distributed.
- the diffracted scanning light is scanned by scanning light 13a corresponding to light having the shortest wavelength component in the scanning light and scanning corresponding to light having the longest wavelength component in the scanning light.
- the scanning lights 13a and 13b will be described as representative of the scanning light diffracted by the diffractive optical element 36.
- the description of the scanning light 13a and the scanning light 13b is the same for the light of other frequency components.
- the diffractive optical element 36 a diffraction grating having about 300 to 600 grooves per 1 mm or other types of diffraction gratings can be used.
- the diffractive optical element 36, the condensing lens 37, and the scanning mirror 38b are located between the diffractive optical element 36 and the condensing lens 37 and between the condensing lens 37 and the scanning mirror 38b. Are arranged at the same interval to constitute a so-called 4f optical system.
- the condensing lens 37 refracts the incident scanning lights 13a and 13b, condenses the scanning lights 13a and 13b separated by the diffractive optical element 36 on the scanning mirror 38b, and reflects the scanning lights 13a and 13b reflected by the scanning mirror 38b. 13 b is condensed on the diffractive optical element 36.
- the polygon scanner 38 is connected to a polygonal column-shaped rotating body 38c having a rotating shaft 38a as a center, a plurality of scanning mirrors 38b arranged on each side of the rotating body 38c, and the rotating shaft 38a.
- a motor (not shown in FIG. 3) that rotates the rotating body 38c by rotating
- a rotation control unit (not shown in FIG. 3) that controls the rotation of the rotating body 38c by controlling the motor.
- the rotary shaft 38a rotates
- the rotary body 38c performs a periodic motion that rotates in a fixed direction around the rotary shaft 38a.
- the scanning mirror 38b is also periodically moved by the rotation of the polygon scanner 38.
- the polygon scanner 38 uses a 7-sided polygon laser scanner manufactured by Nidec Copal, and a scanning mirror 38b is provided on each of the seven side surfaces of a heptagonal prism-shaped rotating body 38c with an inscribed circle diameter of 40 mm. I have.
- the polygon scanner 38 periodically moves at a frequency of 167 Hz in the clockwise direction. That is, the polygon scanner 38 rotates clockwise with a period of 6 ms.
- other commercially available general polygon scanners such as RTA series manufactured by Lincoln Laser can be used.
- the rotating body 38c of the polygon scanner 38 rotates clockwise in the direction of the arrow in FIG. 3, and the focal plane (Fourier plane) of the scanning light diffracted by the scanning mirror 38b and the diffractive optical element 36.
- the distance between the position where the scanning light 13a hits the scanning mirror 38b and the diffractive optical element 36 is the distance between the position where the scanning light 13b hits the scanning mirror 38b and the diffractive optical element 36. Is equal to As a result, the optical path length of the scanning light 13a is equal to the optical path length of the scanning light 13b. At this time, the optical path lengths of the light of other wavelength components dispersed by the diffractive optical element 36 are also equal.
- the scanning mirror 38b is further rotated by the rotation of the rotating shaft 38a, and the inclination is changed.
- One end of the scanning mirror 38b in the rotation direction is moved away from the diffractive optical element 36, and the other end is moved closer to the diffractive optical element 36 side.
- the position where the scanning light 13 b hits the scanning mirror 38 b moves to the back side with respect to the diffractive optical element 36, and the position where the scanning light 13 a hits moves to the near side with respect to the diffractive optical element 36. Therefore, the distance between the position where the scanning light 13a hits the scanning mirror 38b and the diffractive optical element 36 is different from the distance between the position where the scanning light 13b hits the scanning mirror 38b and the diffractive optical element 36.
- the optical path length between the diffractive optical element 36 and the scanning mirror 38b of the scanning light 13a is different from the optical path length between the diffractive optical element 36 and the scanning mirror 38b of the scanning light 13b.
- the light of each wavelength component between the scanning light 13a and the scanning light 13b also has different optical path lengths according to the inclination of the scanning mirror 38b. In this way, the scanning light has a different optical path length for each wavelength component light.
- the rotation shaft 38a further rotates, the scanning mirror 38b is further tilted, one end on the rotation direction side is further away, and the other end is further closer, so that the difference in optical path length between the scanning light 13a and the scanning light 13b becomes larger.
- the optical path length difference between the component lights increases.
- the initial position is caused by the periodic motion of the rotating body 38c due to the rotation of the rotating shaft 38a.
- the rotation angle of the scanning mirror 38b is the rotation angle of the rotation shaft 38a when the scanning mirror 38b rotates.
- the difference in optical path length between the scanning light 13a and the scanning light 13b is obtained by increasing the rotation angle from the initial position of the scanning mirror 38b until the scanning light 13a hits the boundary with the adjacent scanning mirror 38b. Will increase.
- the rotation shaft 38a further rotates, the scanning light 13a hits the scanning mirror 38b adjacent to the scanning mirror 38b on which the current scanning light 13b hits, and the scanning light strikes across the two adjacent scanning mirrors 38b. Become.
- the scanning light 13b also comes into contact with the scanning mirror 38b on which the current scanning light 13a strikes, and the reference light again comes into contact with one scanning mirror 38b.
- the focal plane of the scanning light and the scanning mirror 38b become parallel, and the scanning mirror 38b moves to the initial position.
- the polygon scanner 38 includes a plurality of scanning mirrors 38b, the above process is repeated for each scanning mirror 38b, and the rotation of the rotating shaft 38a increases or decreases the optical path length difference between the scanning light 13a and the scanning light 13b. Repeated. In addition, after the scanning light hits two adjacent scanning mirrors 38b, the reference light hits one scanning mirror 38b again, and the scanning mirror 38b moves to the initial position. Is a dead time in which a molecular vibration spectrum cannot be obtained.
- the scanning lights 13 a and 13 b reflected by the scanning mirror 38 b are collected by the condenser lens 37 and enter the diffractive optical element 36.
- the scanning lights 13 a and 13 b are combined by the diffractive optical element 36 and are emitted from the diffractive optical element 36 as an optical pulse.
- the scanning light emitted from the diffractive optical element 36 enters the second mirror 35 that is a plane mirror.
- the second mirror 35 is arranged so that the scanning light emitted from the diffractive optical element 36 enters the mirror surface perpendicularly.
- the scanning light reflected by the second mirror 35 passes through the same path in the opposite direction and reenters the beam splitter 23.
- the optical path length of the reference light of the first arm 21B (the optical path length of the reciprocating reference light from the beam splitter 23 to the first mirror 25) and the scanning mirror 38b of the polygon scanner 38 are in the initial position. Arrangement of components of the first arm 21B and the second arm 22B so that the optical path length of the scanning light of the second arm 22B (the optical path length of the reciprocating scanning light from the beam splitter 23 to the second mirror 35) becomes equal. Has been adjusted.
- the scanning mirror 38b when the scanning mirror 38b is in the initial position, the scanning light propagating through the second arm 22B reaches the beam splitter 23 without being delayed by the reference light propagating through the first arm 21B. Since both are demultiplexed from the same optical pulse 13, they are superimposed and strengthened to generate an interference wave 14.
- the distance between the position where the scanning light hits the scanning mirror 38b and the diffractive optical element 36 is the longest when the scanning light 13b (light having the longest wavelength in the reference light) hits the scanning mirror 38b.
- the position where the scanning light 13a (light having the shortest wavelength in the reference light) hits the scanning mirror 38b is the shortest.
- the light of each wavelength component of the scanning light is arranged in the order of short wavelength between the scanning light 13a and the scanning light 13b, and is irradiated linearly on the surface of the scanning mirror 38b, so from the position where the scanning light 13a hits.
- the wavelength of the scanning light hitting the scanning mirror 38b becomes longer as it goes to the position where the scanning light 13b hits. Therefore, the distance between the position where the light of each wavelength component of the scanning light hits the scanning mirror 38b and the diffractive optical element 36 becomes longer as the wavelength of the light of each wavelength component of the scanning light becomes longer, and is proportional to the wavelength. It changes linearly. Therefore, the optical path length of each wavelength component also changes linearly in proportion to the wavelength.
- the light of each wavelength component of the scanning light When light of each wavelength component of the scanning light is combined by the diffractive optical element 36, the light of each wavelength component has a phase delay corresponding to the optical path length difference from the scanning light 13a having the shortest optical path length. . Since the optical path length of the light of each wavelength component changes linearly in proportion to the wavelength, the phase delay also changes linearly in proportion to the wavelength.
- the phase of the light of each wavelength component of the scanning light changes, the timing at which the phases of the light of each wavelength component are aligned changes, and group delay occurs.
- the phase state of light means the degree of overlap of light of each wavelength component, that is, the degree of delay of the phase of each wavelength component.
- the scanning light has a group delay without increasing the pulse width. Since the optical path length difference between the scanning light 13a and the scanning light 13b increases in proportion to the rotation angle of the scanning mirror 38b, the group delay of the scanning light also increases in proportion to the rotation angle of the scanning mirror 38b.
- the second arm 22B delays the scanning light according to the rotation angle of the scanning mirror 38b. Due to the delay in the scanning light, the scanning light reaches the beam splitter 23 with a delay with respect to the reference light.
- the interference wave 14 is a collinear optical pulse in which the scanning light delayed on the same optical axis as the reference light is aligned and superimposed with the scanning light delayed on the reference light.
- the scanning light delay with respect to the reference light changes because the optical path length difference between each wavelength component of the scanning light changes according to the rotation angle of the scanning mirror 38b, and the delay time of the light of each wavelength component changes. It changes according to the rotation angle of 38b.
- the delay of the scanning light with respect to the reference light becomes the maximum, and the rotation angle from the initial position of the scanning mirror 38b at this time is the rotation angle. The maximum value of.
- the rotating body 38c rotates at a constant speed and the rotation angle of the scanning mirror 38b changes at a constant speed, the scanning light is delayed with respect to the reference light during the period from the initial position until the rotation angle reaches the maximum value. Varies linearly with time. Therefore, by using the intensity of the anti-Stokes light 15 detected during the period from the initial position until the rotation angle reaches the maximum value, the time axis does not need to be corrected as in the above embodiment. .
- the interferometer 3B changes the optical path length for each wavelength component of the scanning light according to the rotation angle from the initial position of the scanning mirror 38b, and changes the phase state of each wavelength component in the scanning light for scanning.
- An interference wave 14 in which the light is delayed with respect to the reference light is generated.
- the Fourier transform spectroscopic device 1B changes the optical path length of the light of each wavelength component of the scanning light by rotating the scanning mirror 38b by the rotation of the rotation shaft 38a, and the initial of the scanning mirror 38b. Since the scanning light is delayed with respect to the reference light according to the rotation angle from the position, compared with the case where the scanning light is delayed with respect to the reference light by moving the position of the movable mirror as in the conventional Fourier transform spectrometer. Since the rotation shaft 38a only needs to be rotated, the scanning mirror 26b can be moved at a higher speed, and the acquisition speed of the molecular vibration spectrum can be improved.
- the Fourier transform type spectroscopic device 1B of Modification 2 can continuously acquire the molecular vibration spectrum for each scanning mirror 38b of the rotator 38c by continuously rotating the rotator 38c in the fixed direction.
- a conventional Fourier transform spectrometer that needs to repeatedly accelerate and stop, it is possible to eliminate the time required for acceleration and stop, particularly when the molecular vibration spectrum of the test object 7 is continuously acquired.
- the acquisition speed of the molecular vibration spectrum can be improved.
- the Fourier transform type spectroscopic device 1B of the modification 2 can acquire the molecular spectrum spectrum by the number of the scanning mirrors 38b provided in the rotating body 38c while the rotating body 38c makes one rotation, thus, when acquiring a molecular vibration spectrum, the acquisition speed of the molecular vibration spectrum can be further improved.
- the scanning light may precede the reference light.
- the initial position of the scanning mirror 38b is set.
- the optical path length of the reference light is changed by adjusting the position of the component of the first arm 21B so that the delay of the scanning light with respect to the reference light becomes zero. In this way, the scanning light can precede the reference light.
- the rotational frequency of the rotating body 38c, the number of surfaces of the scanning mirror 38b, and the inscribed circle diameter of the rotating body 38c depend on the parameters (repetition frequency, pulse width, etc.) of the optical pulse 13 to be used and the target measurement rate. It can be selected as appropriate.
- the polygon scanner 38 includes a 54-prism-shaped rotating body 38c having an inscribed circle diameter of 60 mm. , And rotating the rotating body 38c at a frequency of 916.7 Hz, a delay equivalent to about 1 mm is generated when the scanning light is converted into an optical path length difference with respect to the reference light, and can be measured at a measurement rate of about 50 kHz. .
- the rotating body 38c has a prismatic shape with 54 or less vertices. Further, when the number of vertices is increased and the number of surfaces of the scanning mirror 38b is increased, the spectral resolution is greatly reduced.
- the Fourier transform spectrometer of Modification 3 is that the polygon scanner of the second arm 22B of the Fourier transform spectrometer 1B of Modification 2 is replaced with a resonant scanner. Is different from the Fourier transform spectrometer 1B. Since other configurations are the same, description thereof is omitted.
- the scanning light diffracted by the diffractive optical element 40 and dispersed is condensed by the condenser lens 41 onto the scanning mirror 42b of the resonant scanner 42 and reflected by the scanning mirror 42b.
- the scanning light reenters the condensing lens 41 and is condensed on the diffractive optical element 40 by the condensing lens 41.
- the scanning light condensed on the diffractive optical element 40 is combined and made incident on the second mirror 43.
- the configuration of the diffractive optical element 40 is the same as that of the second modification.
- the split scanning light is divided into scanning light 13 c corresponding to light having the longest wavelength component in the scanning light and scanning light corresponding to light having an intermediate wavelength component in the scanning light.
- 13d and scanning light 13e corresponding to the light having the shortest wavelength component in the scanning light, but the separated light of each wavelength component is between the scanning light 13c and the scanning light 13d. They are continuously arranged between the scanning light 13d and the scanning light 13e.
- the scanning lights 13c, 13d, and 13e will be described as representative of the scanning light that is split by the diffractive optical element 40.
- the description of the scanning lights 13c, 13d, and 13e is the same for the other scanning lights.
- the condenser lens 41 is disposed so as to be parallel to the diffractive optical element 40 at the same distance as the focal length of the condenser lens 41 from the diffractive optical element 40.
- the condensing lens 41 refracts the incident scanning lights 13c, 13d, and 13e, condenses the scanning lights 13c, 13d, and 13e on the scanning mirror 42b, and also reflects the scanning lights 13c, 13d, and 13e reflected by the scanning mirror 42b. Is condensed on the diffractive optical element 40.
- the resonant scanner 42 has the same configuration as the resonant scanner 26 of the above-described embodiment, and the scanning mirror 42b is parallel to the condenser lens 41, and the same distance as the focal length of the condenser lens 41 is set away from the condenser lens 41. Has been placed.
- the diffractive optical element 40, the condenser lens 41, and the scanning mirror 42b constitute a so-called 4f optical system.
- the scanning mirror 42b of the resonant scanner 42 is resonantly oscillated by the rotation of the rotating shaft 42a, and is positioned closest to the condenser lens 41 and the initial position (position A indicated by a broken line in FIG. 4) that is farthest from the condenser lens. (Position B indicated by a solid line in FIG. 4) is periodically moved.
- the scanning mirror 42b has a mirror surface parallel to the focal plane (Fourier plane) of the scanning light condensed by the condenser lens 41 at the initial position.
- the scanning mirror 42b When the scanning mirror 42b is in the initial position, the optical path lengths of the scanning lights 13c, 13d, and 13e are equal, and the optical path lengths of the respective wavelength components of the scanning light are equal. Therefore, when the light of each wavelength component of the scanning light reaches the diffractive optical element 40, the phases are aligned, and when the light of each wavelength component is combined by the diffractive optical element 40, the scanning light is not delayed.
- the distance between the scanning mirror 42b and the diffractive optical element 40 is changed.
- the distance between the scanning mirror 42b and the diffractive optical element 40 is determined by the position where the light of each wavelength component of the scanning light hits. The closer to the outer edge of the mirror 42b, the shorter.
- the optical path length of the light of each wavelength component is the shortest in the scanning light 13c that hits the position closest to the outer edge of the scanning mirror 42b, and the scanning light 13e that hits the scanning mirror 42b in the position farthest from the outer edge. long. Similar to the second modification, the optical path length linearly changes in proportion to the wavelength of light of each wavelength component. The delay time of the light of each wavelength component changes linearly in proportion to the wavelength of the light of each wavelength component.
- the second arm 22C delays the scanning light by the group according to the rotation angle of the scanning mirror 42b, similarly to the second arm 22B of the second modification.
- the configuration of the second arm 22C can be simplified, and the Fourier transform is performed.
- Type spectroscope can be miniaturized.
- the interference wave 14 can be generated at the same interval as the repetition frequency of the optical pulse 13, and the optical pulse 13 is generated. Regardless, the state where the interference wave 14 is not generated can be eliminated, and the dead time during which the molecular vibration spectrum cannot be acquired can be eliminated.
- the molecular vibration spectrum is acquired using only the interferogram of the anti-Stokes light 15 in the time domain in which the delay of the scanning light with respect to the reference light changes linearly with respect to time.
- the time axis of the interferogram of the anti-Stokes light 15 may be corrected as in the above embodiment.
- the Fourier transform spectroscopic device of Modification 4 is obtained by modifying the Fourier transform spectroscopic device 1 of the above-described embodiment so that a molecular vibration spectrum based on the light absorption characteristics of the test object 7 can be acquired.
- the same configuration as the Fourier transform spectrometer 1 of the embodiment shown in FIG. 1 is given the same number, and as shown in FIG. 5, the Fourier transform spectrometer 1D includes the light source 2 and the interferometer 3D. And a photodetector 10, a low-pass filter 11, and a PC 12.
- the Fourier transform spectrometer 1D generates an interferogram of transmitted light 45 as detected light generated by the interference wave 14 passing through the test object 7 using the interferometer 3, and the interferogram Is a Fourier transform spectroscopic device that obtains a molecular vibration spectrum by performing Fourier transform on the PC12.
- the long pass filter 5 and the short pass filter 9 are removed in order to detect the transmitted light 45 emitted from the test object 7. Further, since light absorption by the test object 7 is not a nonlinear optical phenomenon such as coherent anti-Stokes Raman scattering but a linear optical phenomenon, the compensator 4, the first objective lens 6, the second objective lens 8, and The dispersive lens 24 may not be provided in the Fourier transform spectrometer 1D. Therefore, in the Fourier transform spectrometer 1D, the first arm 21D does not have a dispersion lens, and does not have a compensator, a first objective lens, and a second objective lens. Other configurations of the Fourier transform spectroscopic device 1D such as the second arm 22D are the same as those of the Fourier transform spectroscopic device 1 and have the same functions, and thus description thereof is omitted.
- the interferometer 3D has the same function as the interferometer 3 and generates an interference wave 14 in which the scanning light is delayed with respect to the reference light according to the rotation angle from the initial position of the scanning mirror 26b.
- the interference wave 14 hits the test object 7
- the intensity of the light decreases, and the transmitted light 45 is emitted from the test object 7.
- An interferogram having the intensity value of the transmitted light 45 is generated at the same time interval as the repetition period of the light pulse 13.
- the delay of the scanning light with respect to the reference light in the interference wave 14 generated by the interferometer 3D changes periodically according to the rotation angle from the initial position of the scanning mirror 26b of the resonant scanner 26, and becomes the maximum in a half cycle. Therefore, the molecular vibration spectrum of the test object 7 can be acquired by taking out an interferogram corresponding to a half cycle of the change in the rotation angle of the scanning mirror 26b and Fourier-transforming the interferogram.
- the Fourier transform spectrometer 1 is modified so as to obtain a molecular vibration spectrum based on the light absorption characteristic of the test object.
- the Fourier transform spectroscopic apparatus 1A, 1B and the Fourier transform spectroscopic apparatus 1B of Modification 2 to which the second arm 22C of Modification 3 is applied are modified so that a molecular vibration spectrum can be obtained. You can also.
- an interferogram of the transmitted light 45 as the detected light generated by the interference wave 14 passing through the test object 7 is generated. To do.
- a broadband pulse laser is used as the light source 2, but the present invention is not limited to this, and an incoherent light source such as a high-intensity ceramic light source or a tungsten / iodine lamp can be used as the light source 2.
- the reference light and the scanning light are not optical pulses but continuous waves.
- the molecular vibration spectrum is acquired using only the interferogram of the transmitted light 45 in the time domain in which the delay of the scanning light with respect to the reference light changes linearly with respect to time.
- the time axis of the interferogram of the transmitted light 45 may be corrected.
- the interferogram is generated using the transmitted light 45 emitted from the test object 7 as the detection light, and the molecular vibration spectrum based on the light absorption characteristic is acquired.
- the invention is not limited to this, and an interferogram is generated using the reflected light generated by the interference wave 14 being reflected by the test object 7 as the detected light, and the interferogram is Fourier transformed to absorb light. A molecular vibration spectrum based on the above may be acquired.
- FIG. 6 shows an interferogram of the anti-Stokes light 15 generated when the molecular vibration spectrum is acquired
- FIG. 7 shows a molecular vibration spectrum obtained by Fourier transforming the interferogram.
- the horizontal axis is the time axis ( ⁇ s)
- the vertical axis is the relative intensity of the anti-Stokes light 15 detected by the photodetector 10.
- the numbers “1, 2, 3,... N” shown in the interferogram correspond to the numbers of the measurement times of the molecular vibration spectrum in FIG.
- FIG. 7 and correspond to the half period of the vibration period of the scanning mirror 26b. It is attached to each interferogram.
- the horizontal axis of FIG. 7 is the wave number (cm ⁇ 1 ), and the number of measurement times of the molecular vibration spectrum and the measurement time are shown on the right side of FIG.
- FIG. 7 shows a plurality of molecular vibration spectra repeatedly measured in order of measurement time from the front.
- the molecular vibration spectrum represents the relative intensity of anti-Stokes light for each wave number.
- the scanning mirror 26b of the resonant scanner 26 of the Fourier transform spectroscopic device 1 vibrates at a frequency of 8 kHz and periodically moves with a period of 125 ⁇ s.
- molecular vibration spectra can be obtained from the interferogram for a half cycle, and therefore molecular vibration spectra can be obtained every 62.5 ⁇ s. Therefore, the time shown in FIG. 7 is 62.5 ⁇ s.
- the Fourier transform spectrometer 1 can acquire one molecular vibration spectrum every 62.5 ⁇ s, can acquire 16,000 molecular vibration spectra per second, and obtains a molecular vibration spectrum acquisition speed conventionally. It was confirmed that can be improved.
- the temporal change in the mixed state of toluene 61 and benzene 62 was measured as a change in the molecular vibration spectrum using the Fourier transform spectrometer 1A.
- a cuvette 64 containing toluene 61 is disposed between the first objective lens 6 and the second objective lens 8, and the focal point of the interference wave 14 (the focal position of the first objective lens 6) is within the cuvette 64.
- the liquid in the cuvette 64 was adjusted to irradiate the interference wave 14.
- a plurality of drops of benzene 62 were dropped from the pipette 65 onto the toluene 61 in the cuvette 64, and measurement by the Fourier transform spectrometer 1A was started. The results of the above measurement are shown in FIGS. 9A and 9B.
- FIG. 9A shows the temporal change of the molecular vibration spectrum, where the vertical axis is the time axis (ms) and the horizontal axis is the wave number (cm ⁇ 1 ).
- wavenumber 786cm -1 of specific molecular vibrations in toluene 61 from start of measurement 1003 cm -1
- a large peak in the vicinity of 1031cm -1 appears, about 40ms from the time measurement start has elapsed From the time point, a peak of molecular vibration wave number 990 cm ⁇ 1 inherent to benzene 62 appeared. It was observed that when the peak of the molecular vibration wave number unique to the benzene 62 was strengthened, the peak of the molecular vibration wave number inherent to the toluene 61 was weakened to contradict it.
- the graph shown in FIG. 9B shows temporal changes in the concentrations of toluene 61 and benzene 62 at the measurement position, the horizontal axis is the time axis (ms), and the vertical axis is the concentration of toluene 61 and benzene 62. It is.
- the temporal change in the concentration of toluene 61 and benzene 62 is obtained from the temporal change in the measured molecular vibration spectrum. That is, the concentration of toluene 61 are converted from the intensity of the peak of toluene 61 (wavenumber 786cm -1), the concentration of benzene 62 was converted from the intensity of the peak of benzene 62 (wave number 990 cm -1). Thus, it was confirmed that the Fourier transform spectrometer 1 is suitable for observation of a state that changes in a short time because the molecular vibration spectrum acquisition speed is improved.
- the applicability of the Fourier transform spectrometer to flow cytometry was verified.
- a Fourier transform spectrometer 1A was used. 10A and 10B, the microchannel 71 formed in the microfluidic device (not shown) is irradiated with the interference wave 14 from above as shown in FIG.
- the micro flow path 71 has the focal point fs of the interference wave 14 located at the center and the focal point fs of the interference wave 14 located substantially at the center in the width direction (horizontal direction) of the micro flow path 71 as shown in FIG. 10B.
- the position of was adjusted.
- a plurality of beads 72 were allowed to flow along with the water 73 in the microchannel 71, and the molecular vibration spectrum was measured.
- the diameter of the interference wave 14 at the focal point fs was 2.1 ⁇ m.
- the beads 72 were made of polystyrene having an average diameter of 16 ⁇ m and flowed into the microchannel 71 at a flow rate of 0.04 m / s.
- the anti-Stokes light 15 is detected every time the beads pass through the focal point fs of the interference wave 14 as shown in FIG. 11A, and the portion of the interferogram where the anti-Stokes light 15 is detected is shown.
- the molecular vibration spectrum shown in FIG. 11B was obtained by performing Fourier transform. In the obtained molecular vibration spectrum, the peak of the wave number of molecular vibration specific to polystyrene was confirmed.
- the horizontal axis is the time axis (ms)
- the vertical axis is the relative intensity of the anti-Stokes light 15 detected by the photodetector 10.
- the horizontal axis represents the wave number (cm ⁇ 1 )
- the vertical axis represents the relative intensity of the anti-Stokes light 15.
- the Fourier transform spectroscopic device 1A repeatedly generates a high-speed interferogram using the periodic motion caused by the resonance vibration of the scanning mirror 26b, so that the test object is focused on the interference wave 14 like the bead 72. It can be seen that the molecular vibration spectrum of the specimen can be obtained reliably even when the time to pass through fs is short and the timing of passing is irregular, confirming that it is suitable for flow cytometry. did it.
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Abstract
Description
(1)本発明の実施形態のフーリエ変換型分光装置の全体構成
図1に示すように、本発明の実施形態のフーリエ変換型分光装置1は、光源2と、干渉計3と、補償器4と、ロングパスフィルタ5と、第1対物レンズ6と、第2対物レンズ8と、ショートパスフィルタ9と、光検出器10と、ローパスフィルタ11と、分光スペクトル生成部としてのパーソナルコンピュータ(以下、PCという。)12とを備えている。
以上の構成において、本実施形態のフーリエ変換型分光装置1は、光源2から放出されたパルスレーザー光の光パルス13を参照光と走査光とに分波するビームスプリッタ23と、参照光を第1ミラー25で反射させてビームスプリッタ23に再入射させる第1アーム21と、走査光を第2ミラー28で反射させてビームスプリッタ23に再入射させる第2アーム22とを有し、ビームスプリッタ23に再入射した参照光及び走査光を合波して干渉波14を生成する干渉計3を備えるように構成した。
(3-1)変形例1のフーリエ変換型分光装置
以下では、変形例1のフーリエ変換型分光装置について説明する。変形例1のフーリエ変換型分光装置は、上記実施形態のフーリエ変換型分光装置1とは、干渉計の構成が異なるが、他の構成は同様なので、干渉計の構成を中心に説明する。
以下では、変形例2のフーリエ変換型分光装置について説明する。変形例2のフーリエ変換型分光装置は、上記実施形態のフーリエ変換型分光装置1とは、干渉計の構成が異なるが、他の構成は同様なので、干渉計の構成を中心に説明する。
変形例3のフーリエ変換型分光装置は、変形例2のフーリエ変換型分光装置1Bの第2アーム22Bのポリゴンスキャナをレゾナントスキャナに変えた点がフーリエ変換型分光装置1Bと異なる。他の構成は同様であるので、説明は省略する。
上記の実施形態、変形例1~3では、コヒーレントアンチストークスラマン散乱(CARS)で生じたアンチストークス光15から分子振動スペクトルを得るフーリエ変換型分光装置について説明してきたが、本発明はこれに限られず、本発明のフーリエ変換型分光装置は、被検物の吸光特性に基づく分子振動スペクトルを取得できるように変形することができる。
検証試験として上記の実施形態のフーリエ変換型分光装置1を用いて、液体トルエンの分子振動スペクトルを取得した。分子振動スペクトルを取得した際に生成されたアンチストークス光15のインターフェログラムを図6に、またインターフェログラムをフーリエ変換して得られた分子振動スペクトルを図7にそれぞれ示す。図6のインターフェログラムでは、横軸が時間軸(μs)であり、縦軸が光検出器10で検出されたアンチストークス光15の相対的な強度である。また、インターフェログラムに示した番号「1、2、3・・・n」は、図7の分子振動スペクトルの測定回の番号に対応しており、スキャニングミラー26bの振動周期の半周期分のインターフェログラムごとに付してある。図7の横軸は波数(cm-1)であり、図7の右側には、分子振動スペクトルの測定回の番号と、測定時間が示されている。図7には、繰り返し測定した複数の分子振動スペクトルが手前から測定時間の順に示されている。分子振動スペクトルは、波数ごとのアンチストークス光の相対的な強度を表している。
2 光源
3、3A、3B、3D 干渉計
4 補償器
7 被検物
10 光検出器
12 PC
21、21A、21B、21D 第1アーム
22、22A、22B、22C、22D 第2アーム
23 ビームスプリッタ
25、34 第1ミラー
26、42 レゾナントスキャナ
26b、38b、42b スキャニングミラー
28、35、43 第2ミラー
36、40 回折光学素子
38 ポリゴンスキャナ
Claims (8)
- 光源から放出された光を参照光と走査光とに分波するビームスプリッタと、前記参照光を第1ミラーで反射させて前記ビームスプリッタに再入射させる第1アームと、前記走査光を第2ミラーで反射させて前記ビームスプリッタに再入射させる第2アームとを有し、前記ビームスプリッタに再入射した前記参照光及び前記走査光を合波して干渉波を生成する干渉計と、
前記干渉波が照射された被検物から出射した被検出光の強度を検出する光検出器と、
前記干渉波が前記被検物に繰り返し照射されて得られた複数の前記被検出光の強度に基づいてインターフェログラムを生成し、該インターフェログラムをフーリエ変換する分光スペクトル生成部とを備え、
前記第2アームは、前記ビームスプリッタと前記第2ミラー間の前記走査光の光路上にスキャニングミラーが配置され、前記スキャニングミラーの初期位置からの回転角度に応じて前記走査光を前記参照光に対して遅延又は先行させる
ことを特徴とするフーリエ変換型分光装置。 - 前記干渉波の群速度分散を補償する補償器を備える
ことを特徴とする請求項1に記載のフーリエ変換型分光装置。 - 前記第2アームが前記走査光を前記スキャニングミラーに集光する集光レンズを備え、
前記第1アームが前記集光レンズによって前記走査光に生じた群速度分散を前記参照光に生じさせる分散レンズを前記ビームスプリッタと前記第1ミラー間の参照光の光路上に備える
ことを特徴とする請求項1又は2に記載のフーリエ変換型分光装置。 - 前記第2アームが、
前記ビームスプリッタと前記スキャニングミラー間の前記走査光の光路上に設けられ、前記走査光を回折させる回折光学素子を備え、
前記スキャニングミラーの初期位置からの回転角度に応じて、前記走査光の各波長成分の光に光路長差をつけ、前記走査光における前記波長成分の光の位相状態をかえて前記参照光に対して前記走査光を遅延又は先行させる
ことを特徴とする請求項1~3のいずれか1項に記載のフーリエ変換型分光装置。 - 前記スキャニングミラーは、回転軸を中心に回転する多角柱形状の回転体の各側面に設けられている
ことを特徴とする請求項4に記載のフーリエ変換型分光装置。 - 前記スキャニングミラーが共振振動により周期運動する
ことを特徴とする請求項1~4のいずれか1項に記載のフーリエ変換型分光装置。 - 前記被検物から出射した前記被検出光が、前記干渉波が照射されることで前記被検物において生じたコヒーレントラマン散乱により放出された散乱光である
ことを特徴とする請求項1~6のいずれか1項に記載のフーリエ変換型分光装置。 - 前記被検物から出射した前記被検出光が、透過光又は反射光である
ことを特徴とする請求項1~6のいずれか1項に記載のフーリエ変換型分光装置。
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WO2024080301A1 (ja) * | 2022-10-11 | 2024-04-18 | 国立大学法人東京大学 | 高速スキャンフーリエ変換分光器及び分光方法 |
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DE102019210999B4 (de) * | 2019-07-24 | 2023-07-13 | Carl Zeiss Ag | Vorrichtung und Verfahren zur scannenden Abstandsermittlung eines Objekts |
US11237111B2 (en) * | 2020-01-30 | 2022-02-01 | Trustees Of Boston University | High-speed delay scanning and deep learning techniques for spectroscopic SRS imaging |
US11982612B2 (en) * | 2022-04-19 | 2024-05-14 | Bayspec, Inc. | Systems and methods for color-scalable flow cytometry with Raman tags |
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