Raman scattered light measurement system, Raman scattered light measurement method

Abstract

[Problem] To make it easy to determine a peak in a Raman spectrum. [Solution] This Raman scattered light measuring system comprises: a Stokes light generating unit for generating wide bandwidth Stokes light; a pump light generating unit for generating narrow bandwidth pump light; and a wavelength converting unit for changing the central wavelength of the pump light in two ways.

Description

Technical Field

[0001] The present invention relates to a Raman scattered light measurement system and a Raman scattered light measurement method.

Background Art

[0002] Information obtained by measuring Raman scattered light is used in various technical fields and is also widely used in cell observation. Although observation using a phosphor is widely known in cell observation, there is a problem that it has a certain influence on the observation target. Patent Document 1 discloses a coherent Raman scattering microscope including: first pulse laser generation means for generating first pulse light having a first wavelength component; second pulse laser generation means for generating second pulse light having a second wavelength component different from the first wavelength component; irradiation means for irradiating a specimen with the first pulse light and the second pulse light simultaneously; condensing means for condensing scattered light generated from the specimen; wavelength band blocking means for blocking at least the first wavelength component and the second wavelength component from the condensed scattered light and allowing coherent Raman scattered light to pass through; and detection means for detecting the coherent Raman scattered light, wherein the wavelength band blocking means includes spectroscopic means.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention described in Patent Document 1, it is not easy to discriminate peaks in the Raman spectrum.

Means for Solving the Problems

[0005] The Raman scattering light measurement system according to the first aspect of the present invention includes a Stokes light generation unit that generates broadband Stokes light, a pump light generation unit that generates narrowband pump light, and a wavelength change unit that changes the center wavelength of the pump light in two ways. , a measurement unit that measures the signal intensity for each frequency of the reflected light obtained by irradiating the sample with the pump light and the Stokes light to obtain a signal intensity measurement value; a calculation unit that calculates the difference in the signal intensity measurement values for each frequency before and after the wavelength changing unit changes the central wavelength of the pump light; to provided obtain. According to the second aspect of the present invention The Raman scattering light measurement system includes a Stokes light generation unit that generates broadband Stokes light, a pump light generation unit that generates narrowband pump light, and a wavelength changing unit that changes the central wavelength of the pump light in two ways. The wavelength changing unit includes a band-pass filter disposed in the optical path of the pump light and an operating mechanism that moves or rotates the band-pass filter. By moving or rotating the band-pass filter by the wavelength changing unit, the incident angle of the pump light incident on the band-pass filter is changed, and the wavelength of the pump light is changed. According to the third aspect of the present invention The Raman scattering light measurement method includes generating broadband Stokes light, generating narrowband pump light, changing the center wavelength of the pump light in two ways, measuring the signal intensity for each frequency of the reflected light obtained by irradiating the sample with the pump light and the Stokes light, and calculating the difference in the signal intensity for each frequency before and after the center wavelength of the pump light is changed.

Advantages of the Invention

[0006] According to the present invention, peaks in the Raman spectrum can be easily discriminated.

Brief Description of the Drawings

[0007]

Figure 1

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Figure 11

Embodiments for Carrying Out the Invention

[0008] —First Embodiment— Hereinafter, with reference to FIGS. 1 to 7, a first embodiment of the Raman scattering light measurement system according to the present invention will be described.

[0009] (Configuration) FIG. 1 is an overall configuration diagram of a Raman scattering light measurement system S. The Raman scattering light measurement system S includes an SC light source 11 that outputs SC (Super Continuum) light, an LPF (Long Pass Filter) 20 that filters visible light components from the SC light, a first ULPF (Ultra LPF) 21 that divides the SC light into Stokes light Ls (angular frequency: ωs) and pump light Lp (angular frequency: ωp), a BPF 24 that narrows the frequency band of the pump light Lp, an incident angle changing device 25 that changes the incident angle of the pump light Lp to the BPF 24, an objective lens 26 disposed close to the sample 9, a second ULPF 22 and a third ULPF 23 that separate reflected light from the sample 9 and laser light, a measuring instrument 14 that measures the reflected light, and an arithmetic unit 15 that processes the signal measured by the measuring instrument 14.

[0010] The SC light source 11 is a broadband pulse light source that emits intense light with a uniform phase over a wide wavelength range. The SC light source 11 includes a mode-locked laser 12 and a highly nonlinear fiber 13. The mode-locked laser 12 in the present embodiment has a central wavelength of 1064 nm and a pulse width of 5 picoseconds. The wavelength of the SC light passing through the highly nonlinear fiber 13 is 400 nm to 2400 nm. The LPF 20 is a filter that transmits light having a wave number longer than visible light and blocks light having a short wave number equal to or less than visible light.

[0011] The first ULPF 21 is an ultra-steep long-pass filter. The SC light L1 is split by the first ULPF 21 into Stokes light Ls and pump light Lp. Specifically, among the SC light L1, light with a wavelength longer than a predetermined threshold (for example, 1070 nm) becomes Stokes light Ls, and light with a wavelength shorter than the aforementioned predetermined threshold becomes pump light Lp.

[0012] The BPF 24 is a filter that transmits only light of a predetermined wavelength, and the full width at half maximum of the transmitted light is, for example, 0.7 nm. The central wavelength of the pump light Lp that has passed through the BPF 24 is approximately 1064 nm, and the central wavelength of the pump light Lp that is transmitted changes slightly according to the incident angle. In the present embodiment, the incident angle is set in two ways, and the central wavelength changes by 0.4 nm. That is, the central wavelength of the pump light Lp in the present embodiment is two types: wavelength λp + 0.2 nm and wavelength λp - 0.2 nm. Hereinafter, in order to distinguish pump lights with different central wavelengths, the one with a shorter wavelength may be called the first pump light Lp1, and the one with a longer wavelength may be called the second pump light Lp2.

[0013] The incident angle changing device 25 changes the incident angle of the pump light Lp to the BPF 24 by changing the position or posture of the BPF 24. The incident angle changing device 25 is, for example, a galvanometer scanner to which the BPF 24 is fixed. The incident angle changing device 25 changes the incident angle of the pump light Lp to the BPF 24 at short time intervals based on an operation command from a controller (not shown). In FIG. 1, for reasons of drawing, the incident angle changing device 25 is shown at a position separated from the BPF 24, but actually the BPF 24 is fixed to the incident angle changing device 25.

[0014] The Stokes light Ls and the pump light Lp are combined by the first ULPF 21 after adjusting the optical path length. By passing this combined light through the second ULPF 22, light with a wavelength shorter than a predetermined value is blocked. This predetermined value is, for example, 1058 nm.

[0015] The objective lens 26 focuses the Stokes light Ls and the pump light Lp on the sample 9. Further, this objective lens 26 guides the reflected light L4 obtained by irradiating the sample 9 with the Stokes light Ls and the pump light Lp to the second ULPF. Note that the reflected light L4 is the light reflected from the sample 9, but it is given a different name in order to distinguish it from the pump light Lp. The sample 9 is placed on an XY table (not shown), and the observation position of the sample 9, that is, the position where the Stokes light Ls and the pump light Lp are focused, can be adjusted by operating the XY table.

[0016] The second ULPF 22 and the third ULPF 23 are ultra-steep long-pass filters. The second ULPF 22 and the third ULPF 23 separate the light irradiated on the sample 9 from the reflected light L4, that is, the Stokes light Ls and the pump light Lp. However, a short-pass filter having a steep edge at 1064 nm may be used instead of the second ULPF 22 and the third ULPF 23.

[0017] The measuring device 14 includes a spectroscope 141, an optical sensor 142, an AD converter 143, and an arithmetic unit 144. The spectroscope 141 is, for example, a prism. The spectroscope 141 spatially disperses the light of various wavelengths included in the reflected light L4 for each wavelength and inputs it to the optical sensor 142. The optical sensor 142 is a plurality of light receiving elements. When the reflected light L4 is irradiated on the optical sensor 142, each light receiving element generates a current according to the intensity of the received light at predetermined time intervals. The optical sensor 142 is a plurality of light receiving elements having sensitivity to the frequency to be measured, a high saturation light detection intensity, and a fast response, for example, a photodiode array using indium gallium arsenide (InGaAs).

[0018] The AD converter 143 converts the current generated by the optical sensor 142, i.e., the analog signal, into a digital signal and outputs it to the arithmetic unit 144. This digital signal indicates the signal intensity of a specific frequency contained in the reflected light L4. The arithmetic unit 144 is, for example, a microcomputer. The arithmetic unit 144 arranges the digital signal output by the AD converter 143 into a predetermined format and outputs information on the signal intensity for each frequency of the reflected light L4 to the arithmetic device 15. Hereinafter, the information on the signal intensity for each frequency of the reflected light L4 is also referred to as the "signal intensity measurement value". However, the wavelength may be used instead of the frequency, or the Raman shift amount may be used. For example, the arithmetic unit 144 may add frequency information to the signal intensity information output by the AD converter 143 and output it to the arithmetic device 15, or may sort the signal intensity information output by the AD converter 143 in descending or ascending order of frequency and output it to the arithmetic device 15.

[0019] The arithmetic device 15 processes a plurality of signal intensity measurement values measured by the measuring device 14. Specifically, the arithmetic device 15 evaluates the difference in the signal intensity measurement values using two types of pump light Lp for each frequency. For example, the arithmetic device 15 evaluates the difference in the signal intensity between the reflected light L4 when the central wavelength of the pump light Lp is the wavelength λp + 0.2 nm and the reflected light L4 when the central wavelength of the pump light Lp is the wavelength λp - 0.2 nm. The processing of the arithmetic device 15 will be described in detail later. The arithmetic device 15 may display the processing result or record it in a storage device. The display and recording by the arithmetic device 15 may be only numerical values that simply indicate the calculation result, or may be accompanied by a graph.

[0020] Figure 2 is a hardware configuration diagram of the arithmetic device 15. The arithmetic device 15 includes a CPU 151 that is a central processing unit, a ROM 152 that is a read-only storage device, a RAM 153 that is a readable and writable storage device, an input / output device 154 that is a user interface, a communication device 155, and a storage device 156. The CPU 151 performs the above-described operations by expanding and executing the program stored in the ROM 152 in the RAM 153.

[0021] The arithmetic unit 15 may be implemented by an FPGA (Field Programmable Gate Array), which is a rewritable logic circuit, or an ASIC (Application Specific Integrated Circuit), which is an integrated circuit for specific applications, instead of a combination of the CPU 151, the ROM 152, and the RAM 153. Further, the arithmetic unit 15 may be implemented by a combination of different configurations, for example, a combination of the CPU 151, the ROM 152, the RAM 153, and the FPGA, instead of the combination of the CPU 151, the ROM 152, and the RAM 153.

[0022] The input / output device 154 includes a keyboard, a mouse, and a display. The input / output device 154 displays the calculation result of the CPU 151 and the information stored in the storage device 156 on the display. The communication device 155 is a communication interface with the measuring instrument 14 and conforms to a known communication standard such as IEEE802.3. The communication device 155 receives the measurement result from the measuring instrument 14 and stores it in the storage device 156. The storage device 156 is a non-volatile storage device, for example, a flash memory or a hard disk drive. The measurement result measured by the measuring instrument 14 and the calculation result by the CPU 151 are stored in the storage device 156.

[0023] (Energy diagram) FIG. 3 is an energy diagram in the present embodiment. Each of ωp and ωs is the energy of the pump light Lp and the Stokes light Ls, and Ωi is the energy corresponding to the angular frequency in the vibration mode of the sample 9.

[0024] (Wavelength of pump light Lp) FIG. 4 is a diagram showing the wavelength characteristics of the pump light Lp and the Stokes light Ls. In the upper right of FIG. 4, the wavelength characteristics of the pump light Lp before and after passing through the BPF24 are shown. The pump light Lp shown by the solid line in FIG. 4 has a strong intensity at a specific wavelength, and the Stokes light Ls shown by the broken line has a weaker intensity than the pump light Lp in a wide wavelength range. In the upper right of FIG. 4, the pump light Lp before passing through the BPF24 is shown by a dashed-dotted line, and the pump light Lp after passing through the BPF24 is shown by a solid line. As shown in the upper right of FIG. 4, by passing through the BPF24, it is limited to a very narrow wavelength centered around about 1064 nm. As described above, by moving or routing the BPF24 to change the incident angle of the pump light Lp to the BPF24, the central wavelength of the pump light Lp is changed by 0.4 nm.

[0025] (Waveform) FIG. 5 is a diagram showing the relationship between Ωi, which is the angular frequency in the vibration mode of the sample 9, and the CARS signal waveform. However, since the waveform differs depending on the magnitude relationship between the intensity of the CARS signal and the intensity of the non-resonant background (hereinafter referred to as "NRB") signal not related to Raman scattering, the waveforms are shown by case division. The left side of FIG. 5 shows the waveform when the CARS signal is sufficiently weaker than the NRB signal, and the right side of FIG. 5 shows the waveform when the CARS signal is stronger than the NRB signal.

[0026] In FIG. 5, the CARS signals corresponding to the frequencies of two types of pump lights are shown together. The broken line shows the CARS signal corresponding to the first pump light Lp1 with a lower frequency, and the solid line shows the CARS signal corresponding to the second pump light Lp2 with a higher frequency. The dashed-dotted line shown at the bottom indicates the difference between the two CARS signals. When the CARS signal is sufficiently weaker than the NRB signal, as shown on the left side of FIG. 5, the difference between the two CAS signals has a peak at the vibration frequency ωi. On the other hand, when the CARS signal is larger than the NRB signal, a spectrum as shown on the right side of FIG. 5 appears at the vibration frequency ωi.

[0027] (Processing of the program) The processing performed by the CPU 151 incorporated in the arithmetic unit 15 will be described. The CPU 151 processes two signal intensity measurement values with the same conditions except for the pump light Lp and different central wavelengths of the pump light Lp, and calculates the difference in signal intensity for each frequency. Any of the following three methods can be used to identify the processing target. Whether the arithmetic unit 15 adopts any of the following three methods may be set by the input / output device 154 or may be specified in advance.

[0028] The first method is a method of identifying the processing target in the order of the data input from the measuring device 14 on the premise that the order of measurement is determined in advance. For example, assuming that the measurement values output by the measuring device 14 use the first pump light Lp1 and the second pump light Lp2 alternately, and the two consecutive measurement conditions are the same except for the wavelength of the pump light, the arithmetic unit 15 identifies and processes the processing target as follows. That is, the arithmetic unit 15 calculates the difference between the first and second signal intensity measurement values for each frequency, calculates the difference between the third and fourth signal intensity measurement values for each frequency, and calculates the difference between the fifth and sixth signal intensity measurement values for each frequency.

[0029] The second method is a method of receiving a designation by an operator. For example, the signal intensity measurement values received from the measuring device 14 are stored in the storage device 156 in advance, and the difference in signal intensity for each frequency is calculated for the set of signal intensity measurement values designated by the operator.

[0030] The third method is a method in which the arithmetic unit 15 summarizes the measurements and actively processes them. In this case, the arithmetic unit 15 can control at least the operations of the incident angle changing device 25 and the measuring device 14, and the arithmetic unit 15 sets the incident angle changing device 25 to, for example, either the first angle or the second angle. When the arithmetic unit 15 sets the incident angle changing device 25 to the first angle and causes the measuring device 14 to perform a measurement, the arithmetic unit 15 sets the incident angle changing device 25 to the second angle and causes the measuring device 14 to perform a measurement again. The arithmetic unit 15 calculates the difference between the two signal intensity measurement values thus obtained.

[0031] FIG. 6 is a diagram showing the calculation by the arithmetic unit 15. The horizontal axis in FIG. 6 indicates the Raman shift amount, and the vertical axis indicates the scattering intensity. In FIG. 6, the dashed-dotted line indicates the CARS signal corresponding to the first pump light Lp1 with a low frequency, and the dashed line indicates the CARS signal corresponding to the second pump light Lp2 with a high frequency. The values of the two CARS signals are almost the same except in the vicinity of 50 cm -1 and overlap in FIG. 6.

[0032] The solid line indicates the difference in intensity between the two CARS signals for each Raman shift amount, and in FIG. 6, it is multiplied by 3 for convenience of drawing. The dashed line shown at the bottom of FIG. 6 is the amount obtained by numerically differentiating the CARS signal indicated by the dashed-dotted line with respect to the Raman shift amount.

[0033] From the measurement results shown by the dashed line and the dashed-dotted line at the top of FIG. 6, it can be seen that there are peaks at 470 cm -1 and 220 cm -1 . Also, from the measurement results shown by the dashed line and the dashed-dotted line, there seem to be peaks at 150 cm -1 and 70 cm -1 , but it is difficult to determine whether they are peaks. From the calculation results shown by the solid line, it can be confirmed that there are peaks at 470 cm -1 , 220 cm -1 , and 150 cm -1 , and there is no peak at 70 cm -1 . Also, these three waveforms are in the shape shown on the right in FIG. 5, indicating that they are not affected by interference. In the calculation result shown by the dashed line at the bottom of FIG. 6, not only at 470 cm -1 and 220 cm -1 , and 150 cm -1 , but also a peak exists at 170 cm -1 . The peak at 170 cm -1 is an over-detection, indicating that the peak cannot be properly detected by differentiation.

[0034] FIG. 7 is a diagram showing the change in Raman scattering with respect to temperature change, specifically, the result of calculating the difference in signal intensity between the CARS signal corresponding to the first pump light Lp1 and the CARS signal corresponding to the second pump light Lp2 for each Raman shift amount. Each spectrum is normalized by the intensity at 470 cm -1 . In FIG. 7, sample 9 was measured while being changed to seven temperatures from 25 degrees to 120 degrees. Specifically, L1 shown in FIG. 7 corresponds to 25 degrees, and L7 corresponds to 120 degrees. The calculation result at 25 degrees in FIG. 7 is the same as the data shown by the solid line in FIG. 6. In FIG. 7, at 470 cm -1 , 220 cm -1 , and 150 cm -1 , it can be seen that the signal intensity changes with temperature. Specifically, the signal at 150 cm -1 increases as the temperature rises, and the signal at 220 cm -1 decreases as the temperature rises.

[0035] In the present embodiment, as shown in FIG. 4, the broadband Stokes light Ls is generated by the SC light source 11, the LPF 20, and the first ULPF 21. Therefore, the SC light source 11, the LPF 20, and the first ULPF 21 can be collectively referred to as a "Stokes light generation unit". Further, as shown in FIG. 4, the narrowband pump light Lp is generated by the SC light source 11, the LPF 20, the first ULPF 21, and the BPF 24. Therefore, the SC light source 11, the LPF 20, the first ULPF 21, and the BPF 24 can be collectively referred to as a "pump light generation unit". Furthermore, the incident angle changing device 25 changes the center wavelength of the pump light Lp to two values, for example, 1064 nm + 0.2 nm and 1064 nm - 0.2 nm, by moving or rotating the BPF 24. Therefore, the BPF 24 and the incident angle changing device 25 can be referred to as a "wavelength changing unit".

[0036] According to the first embodiment described above, the following operational effects can be obtained. (1) The Raman scattered light measurement system S includes a Stokes light generation unit that generates broadband Stokes light Ls, a pump light generation unit that generates narrowband pump light Lp, and a wavelength change unit including a BPF24 and an incident angle change device 25 that change the center wavelength of the pump light Lp in two ways. As described above, the Stokes light generation unit includes an SC light source 11, an LPF20, and a first ULPF21. The pump light generation unit includes an SC light source 11, an LPF20, a first ULPF21, and a BPF24. Therefore, by calculating the difference between the reflected lights L4 obtained using each of the two pump lights Lp, as shown by the solid line in FIG. 6, the peak in the Raman spectrum can be easily discriminated.

[0037] (2) The Raman scattered light measurement system S includes a measuring device 14 that measures the signal intensity for each frequency of the reflected light L4 obtained by irradiating a sample 9 with the pump light Lp and the Stokes light Ls to obtain a signal intensity measurement value, and an arithmetic device 15 that calculates the difference between the signal intensity measurement values for each frequency before and after the incident angle change device 25, which is a wavelength change unit, changes the center wavelength of the pump light Lp. Therefore, from the calculation result of the arithmetic device 15, as shown by the solid line in FIG. 6, the peak in the Raman spectrum can be easily discriminated.

[0038] (3) The wavelength change unit includes a BPF24 arranged in the optical path of the pump light Lp and an operating mechanism that moves or rotates the BPF24, that is, an incident angle change device 25. By moving or rotating the BPF24 by the incident angle change device 25, the incident angle of the pump light Lp incident on the BPF24 is changed, and the wavelength of the pump light Lp is changed. Therefore, the wavelength of the pump light Lp can be changed by rotating the BPF24.

[0039] (4) The operating mechanism for operating the BPF24 is a galvanometer scanner. Therefore, since the angle of the BPF24 can be changed quickly, the measurement with the changed center frequency of the pump light Lp is completed in a short time. Therefore, when performing a large number of measurements, for example, when a certain area is divided into 100 sections x 100 sections and measured 10,000 times, the time required for the entire measurement can be shortened, and the advantage becomes significant.

[0040] (5) The pump light Lp and the Stokes light Ls are infrared light. Therefore, compared with a configuration using visible light for the pump light Lp and the Stokes light Ls, the configuration in the present embodiment is less likely to damage the sample 9.

[0041] (6) The Raman scattered light measurement method in the Raman scattered light measurement system S includes generating broadband Stokes light Ls, generating narrowband pump light Lp, changing the center wavelength of the pump light Lp in two ways, measuring the signal intensity for each frequency of the reflected light L4 obtained by irradiating the sample 9 with the pump light Lp and the Stokes light Ls, and calculating the difference in the signal intensity for each frequency before and after the center wavelength of the pump light Lp is changed. Therefore, the peaks in the Raman spectrum can be easily discriminated.

[0042] (Modification 1) In the above-described first embodiment, the light output from one SC light source 11 is used as the pump light Lp and the Stokes light Ls, and the pump light Lp is changed to the first pump light Lp1 and the second pump light Lp2 by changing the incident angle to the BPF 24. However, the Stokes light Ls, the first pump light Lp1, and the second pump light Lp2 may be output from different light sources respectively.

[0043] FIG. 8 is a configuration diagram of the Raman scattered light measurement system S in Modification 1. Comparing FIG. 8 with FIG. 1, it has a first light source 11-1, a second light source 11-2, a third light source 11-3, a first shutter 28-1, and a second shutter 28-2 instead of the SC light source 11. In this modification, it does not include the BPF 24 disposed on the optical path of the pump light Lp in FIG. 1, and further does not include the incident angle changing device 25 for moving or rotating the BPF 24.

[0044] The first light source 11-1 outputs Stokes light Ls. The second light source 11-2 outputs the first pump light Lp1. The third light source 11-3 outputs the second pump light Lp2. The first shutter 28-1 and the second shutter 28-2 are opening and closing doors that cannot be open simultaneously at most. That is, in this modified example, depending on which of the first shutter 28-1 and the second shutter 28-2 is in the open state, either the first pump light Lp1 or the second pump light Lp2 is selectively output.

[0045] The first light source 11-1 can be realized by the combination of the SC light source 11, the LPF 20, and the first ULPF 21 in the first embodiment. The second light source 11-2 can be realized by the combination of the SC light source 11, the LPF 20, the first ULPF 21, and the BPF 24 in the first embodiment. The third light source 11-3 can be realized by the combination of the SC light source 11, the LPF 20, the first ULPF 21, and the BPF 24 in the first embodiment. However, the angle at which the light emitted from the second light source 11-2 enters the BPF 24 is set in advance to be different from the angle at which the light emitted from the third light source 11-3 enters the BPF 24.

[0046] The first shutter 28-1 and the second shutter 28-2 may be electrically operated opening and closing doors or a rotating plate having a slit. Also, the first shutter 28-1 and the second shutter 28-2 may be integrally configured.

[0047] According to this modified example, the following operational effects can be obtained. (7) The Raman scattering light measurement system S includes a second light source 11-2 that outputs a first pump light having a center wavelength of a first wavelength, a third light source 11-3 that outputs a second pump light having a center wavelength of a second wavelength, and a first shutter 28-1 and a second shutter 28-2 that selectively irradiate the sample 9 with either of the two pump lights. Therefore, the same effects can be achieved with a configuration different from that of the first embodiment.

[0048] (Modified Example 2) In the above-described Modification 1, three light sources were used. However, two light sources, i.e., a light source that outputs pump light Lp and a light source that outputs Stokes light Ls, may be used.

[0049] FIG. 9 is a configuration diagram of the Raman scattering light measurement system S in Modification 2. Comparing FIG. 9 with FIG. 1, it has a first light source 11-1 and a fourth light source 11-4 instead of the SC light source 11. The function and configuration of the first light source 11-1 are the same as those in Modification 1. The first light source 11-1 outputs Stokes light Ls.

[0050] The fourth light source 11-4 can be realized by a combination of the SC light source 11, the LPF 20, and the first ULPF 21 in the first embodiment. The pump light Lp output from the fourth light source 11-4 is guided to the same path as the Stokes light Ls after passing through the BPF 24. The BPF 24 is moved or rotated by the incident angle changing device 25 as in the first embodiment, and the angle at which the pump light Lp is incident on the BPF 24 is changed. As a result, the central wavelength of the pump light Lp is changed by, for example, 0.4 nm. According to this modification, the same effect can be achieved with a configuration different from that of the first embodiment.

[0051] (Modification 3) In the above-described first embodiment, the incident angle changing device 25 was a galvanometer scanner that moves or rotates the BPF 24. However, the incident angle changing device 25 may be a rotary stage that rotates the BPF 24, or a single-axis or multi-axis stage that moves or rotates the BPF 24. Further, the incident angle changing device 25 may be a moving and rotating mechanism that moves or rotates a mirror (not shown) placed in the optical path until the pump light Lp reflected from the first ULPF 21 is incident on the BPF 24.

[0052] (Modification 4) The arithmetic device 15 may detect a Raman shift amount having a peak in the signal intensity from the measurement result by the measuring device 14 and record it together with the signal intensity. For the detection of the peak, for example, pattern matching having a shape indicated by a one-dot chain line in FIG. 5 can be used.

[0053] (Modification Example 5) In the above-described first embodiment, light in the infrared region was used as the pump light Lp and the Stokes light Ls irradiated on the sample 9. However, the wavelengths of the pump light Lp and the Stokes light Ls may be appropriately changed according to the type of the sample 9, the purpose of measurement, etc. For example, the pump light Lp and the Stokes light Ls can be arbitrarily combined with X-rays, ultraviolet rays, visible rays, infrared rays, and microwaves.

[0054] (Modification Example 6) In the above-described first embodiment, an example was shown in which the wavelength of the pump light Lp was changed to 1064 nm + 0.2 nm and 1064 nm - 0.2 nm using the BPF 24. However, this wavelength is only an example, and other wavelengths may be used as the center wavelength, and the change width may also be arbitrarily changed. However, this change width is restricted by the full width at half maximum, which is a characteristic of the BPF 24 to be used. That is, the larger the full width at half maximum, which is a characteristic of the BPF 24 to be used, the larger the width of the wavelength to be changed needs to be.

[0055] - Second Embodiment - With reference to FIG. 10, a second embodiment of the Raman scattered light measurement system will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the differences will be mainly described. Points not particularly described are the same as those in the first embodiment. This embodiment is different from the first embodiment mainly in that it further includes an optical amplifier that amplifies the pump light.

[0056] FIG. 10 is a configuration diagram of a Raman scattered light measurement system S2 in the second embodiment. The Raman scattered light measurement system S2 in this embodiment includes a pump light amplification unit 50 in addition to the configuration in the first embodiment. The pump light amplification unit 50 includes an excitation light source 51, an amplification medium 52, and a dichroic mirror 53. The excitation light source 51 is, for example, a semiconductor laser that emits continuous oscillation with a wavelength of 808 nm. The laser light output from the excitation light source 51 excites the amplification medium 52. The amplification laser medium 52 is, for example, an Nd:YVO4 crystal.

[0057] In this embodiment, the pump light Lp that has passed through the BPF 24 is guided to the dichroic mirror 53. Then, the pump light Lp is amplified by the amplification laser medium 52 excited by the excitation light source 51, and the amplified pump light Lp is irradiated onto the sample 9. Since the signal of Raman scattering is also amplified when the pump light Lp is amplified, there are advantages that it is less affected by noise and that the exposure time can be reduced.

[0058] According to the second embodiment described above, the following operational effects can be obtained. (7) It includes a pump light amplification unit 50 that amplifies the intensity of the pump light Lp. Therefore, the signal intensity of the reflected light L4 obtained by irradiating the pump light Lp can be increased.

[0059] - Third Embodiment - Referring to FIG. 11, a third embodiment of the Raman scattering light measurement system will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the differences will be mainly described. Points not particularly described are the same as those in the first embodiment. In this embodiment, it is mainly different from the first embodiment in that interference measurement is performed.

[0060] FIG. 11 is a configuration diagram of the Raman scattering light measurement system S3 in the third embodiment. The Raman scattering light measurement system S3 in this embodiment further includes a first optical member 61 that is a branching mirror and a second optical member 62 that is a half mirror, in addition to the configuration in the first embodiment. The first optical member 61 is arranged in front of the FPF 20 that filters the visible light component, and extracts a part of the output light from the SC light source 11 as the reference light Lr. The reference light Lr is guided to the same optical path as the reflected light L4 by the second optical member 62 and reaches the measuring instrument 14 together with the reflected light L4. Hereinafter, the reflected light L4 and the reference light Lr are collectively referred to as the evaluation light L5.

[0061] Focusing on the light-receiving element of the optical sensor 142 included in the measuring device 14, the light incident on the light-receiving element is the reflected light L4 having a specific wavelength and the reference light Lr. Therefore, each digital signal input to the arithmetic unit 144 is the intensity of the combined light of the reflected light L4 having a specific wavelength and the reference light Lr. Here, let the light intensity of the reference light Lr with a certain wavelength λ be Er, and the light intensity of the evaluation light L5 with a certain wavelength λ be Es. Further, assume that Er is sufficiently larger than Es. In this case, the following relationship holds for the light intensity Ed of the light with wavelength λ detected by the arithmetic unit as shown in Equation 1.

[0062]

Equation

[0063] Here, since the light intensity Er of the reference light Lr is equal to, for example, the light intensity Ed of the light with wavelength λ when the reflected light L4 is temporarily blocked, it can be easily measured individually. Therefore, even if the reflected light L4 is weak, the arithmetic unit 144 can calculate the intensity of the reflected light L4 by satisfying the following two conditions. The first condition is that the magnitude of the second term on the right side of Equation 1 has a sufficient intensity with respect to the sensitivity of the optical sensor 142 included in the measuring device 14. The second condition is that the entire right side of Equation 1 is within the measurement range of the arithmetic unit 144, in other words, the measured value of the arithmetic unit 144 is not saturated. This will be described in detail below.

[0064] Describe the first condition in detail. The component of the evaluation light L5 exists only in the second term on the right side of Equation 1. Therefore, it is necessary for the magnitude of this second term to have a sufficient magnitude with respect to the sensitivity of the optical sensor 142, that is, the measurement resolution. It is desirable for this second term to have a magnitude that is at least several times, preferably 10 times or more, that of the measurement resolution of the optical sensor 142. To satisfy this first condition, it is effective to increase the output of the SC light source 11 or increase the ratio of the reference light Lr in the first optical member 61 which is a branching mirror.

[0065] Here, the above-described second condition becomes a problem. The greater the light intensity Er of the reference light Lr, the more likely the photosensor 142 is to saturate, which hinders measurement. Therefore, it is desirable that the photosensor 142 is less likely to saturate, and more specifically, that the saturation light detection intensity at the frequency at which the light intensity is to be calculated in the arithmetic unit 144 is high. That is, it is desirable to select the SC light source 11 and the photosensor 142 included in the measuring instrument 14 according to the wavelength to be calculated in the arithmetic unit 144.

[0066] According to the third embodiment described above, the following operational effects can be obtained. (8) The pump light Lp and the Stokes light Ls are generated from the same light source, the SC light source 11. A first optical member 61 that branches the light output from the SC light source 11 to obtain a reference light, a second optical member 62 that guides the reflected light L4 and the reference light Lr as an evaluation light L5 onto the same optical path, a spectroscope 141 that spatially disperses the evaluation light L5 for each wavelength, a photosensor 142 that receives the spatially dispersed evaluation light L5, and an arithmetic unit 144 that calculates the light intensity of the reflected light at at least one wavelength using the output of the photosensor 142.

[0067] In each of the above-described embodiments and modifications, the configuration of the functional blocks is merely an example. Some of the functional configurations shown as separate functional blocks may be integrally configured, or the configuration represented by one functional block diagram may be divided into two or more functions. Also, a configuration may be adopted in which a part of the functions of each functional block is provided by other functional blocks. The configurations shown in each of the above-described embodiments and modifications are merely examples. For example, although a large number of optical members that are not particularly described are shown in FIGS. 1 and 8 to 11, they are merely arranged so as not to cause contradictions in the optical path for convenience of drawing, and may be omitted or alternative components may be used.

[0068] Each of the above-described embodiments and modifications may be combined. Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

Explanation of Symbols

[0069] 11…SC light source 11-1…First light source 11-2…Second light source 11-3…Third light source 14…Measurer 15…Arithmetic unit 20…LPF 21…First ULPF 22…Second ULPF 23…Third ULPF 24…BPF 25…Incident angle changing device 26…Objective lens 28-1…First shutter 28-2…Second shutter 51…Excitation light source 52…Amplifying laser medium 53…Dichroic mirror 61…First optical member 62…Second optical member 141…Spectroscope 142…Optical sensor 143…AD converter 144…Arithmetic section L1…SC light L4…Reflected light L5…Evaluation light Lp…Pump light Lr…Reference light Ls…Stokes light S, S2, S3…Raman scattering light measurement system

Claims

1. A Stokes light generation unit that generates broadband Stokes light, A pump light generation unit that generates narrowband pump light, A wavelength changing unit that changes the center wavelength of the pump light in two ways, A measurement unit that measures the signal intensity for each frequency of the reflected light obtained by irradiating the sample with the pump light and the Stokes light, and obtains a signal intensity measurement value, A Raman scattering light measurement system comprising a calculation unit that calculates the difference in the signal intensity measurement values for each frequency before and after the wavelength changing unit changes the center wavelength of the pump light.

2. A Stokes light generation unit that generates broadband Stokes light, A pump light generation unit that generates narrowband pump light, A wavelength changing unit that changes the center wavelength of the pump light in two ways, and The wavelength changing unit includes a band-pass filter arranged in the optical path of the pump light, and an operating mechanism that moves or rotates the band-pass filter, A Raman scattering light measurement system in which the wavelength changing unit changes the incident angle of the pump light incident on the band-pass filter by moving or rotating the band-pass filter, thereby changing the wavelength of the pump light.

3. In the Raman scattering light measurement system according to claim 2, The operating mechanism is a galvanometer scanner, a Raman scattering light measurement system.

4. In the Raman scattering light measurement system according to any one of claims 1 to 3, The pump light and the Stokes light are light in the infrared region, a Raman scattering light measurement system.

5. In the Raman scattering light measurement system according to claim 1 or claim 2, The Raman scattering light measurement system further comprises a pump light amplification unit that amplifies the intensity of the pump light.

6. In the Raman scattering light measurement system according to claim 1, The pump light generation unit and the Stokes light generation unit include the same light source, A first optical member that branches the light output from the light source to obtain reference light, A second optical member that guides the reflected light and the reference light onto the same optical path as evaluation light, A spectroscope that spatially disperses the evaluation light for each wavelength, An optical sensor that receives the spatially dispersed evaluation light, A Raman scattering light measurement system comprising an arithmetic unit that calculates the intensity of the light of the reflected light at at least one wavelength using the output of the optical sensor.

7. Generating broadband Stokes light, Generating narrowband pump light, changing the center wavelength of the pump light to two values; measuring the signal intensity for each frequency of the reflected light obtained by irradiating the sample with the pump light and the Stokes light; calculating the difference in the signal intensity for each frequency before and after the center wavelength of the pump light is changed, and a Raman scattering light measurement method comprising the steps of:

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