CN105092560A - Device and method for detecting signal intensity of frequency-shift excitation raman spectrum based on tunable laser - Google Patents

Abstract

A signal intensity detection device and method based on tunable laser frequency shift excitation Raman spectroscopy, relating to the technical field of signal intensity detection of Raman spectroscopy. In order to solve the problem of complex structure of the frequency-shifting excitation device, poor real-time performance and inability to detect broad-spectrum substances, the process of inverting the original Raman spectrum signal from the differential Raman spectrum signal is computationally intensive and will introduce errors. The grating controller controls the yaw and pitch attitude of the grating, changes the output wavelength of the semiconductor laser by changing the yaw angle of the grating, and adjusts the excitation light power by controlling the coupling efficiency of the beam to the excitation fiber. The Mann spectrum signal is integrated and normalized to obtain a normalized differential Raman spectrum signal, and N data points are uniformly extracted and summed by absolute values to obtain the Raman spectrum signal intensity value. The present invention can be used to obtain the signal intensity of Raman spectrum.

Description

A signal intensity detection device and method based on tunable laser frequency shift excitation Raman spectroscopy

technical field

The invention relates to the technical field of Raman spectrum signal intensity detection.

Background technique

Raman spectroscopy is a detection technology with significant advantages such as fast detection speed, no need for pretreatment, no damage to the measured substance, and the ability to completely reflect the internal structure information of the molecule. It is widely used in food safety, chemical analysis and material analysis, etc. field. However, most Raman detection processes will be accompanied by the generation of fluorescent signals. Weak fluorescent signals will seriously interfere with the identification of weak Raman signals, and strong fluorescent signals will even drown out Raman signals. Interference can be very effective in improving detection efficiency.

At present, the effective methods of suppressing fluorescence widely used mainly include fluorescence quenching method, time-resolved method, numerical processing method and frequency-shift excitation method. The fluorescence quenching method is to reduce the fluorescence yield by adding a specific fluorescence quencher to the sample to be tested or increasing the exposure time of the sample. This method can only be used for a small number of specific samples, and the additional conditions introduced in the measurement process bring great impact on the measurement results. big uncertainty. The time-resolved method takes advantage of the fact that the Raman light lifetime is much shorter than the fluorescence lifetime, and separates the two in the time domain by using ultrashort pulse light or high-frequency modulation light source. However, the Raman system built based on this method needs to adopt high-speed response Devices significantly increase the cost. The numerical processing method uses the different spectral characteristics of the Raman signal and the fluorescent signal, and extracts the weak Raman signal from the fluorescent background through Fourier transform and curve fitting. However, this method is greatly affected by the software algorithm, and the consistency of the measurement results is poor. .

The frequency-shift excitation method is based on the fact that fluorescence is independent of the excitation wavelength. Under the same collection conditions, when the sample is excited by two laser beams with slightly different wavelengths, the fluorescence signals in the two spectra obtained hardly change, while All Raman signals are slightly shifted. Subtract the two collected signals to obtain the differential Raman spectrum signal that removes the fluorescence interference, and then invert the original Raman spectrum signal, and then realize the analysis of the sample to be tested. The process of inverting the original Raman spectrum signal is computationally intensive. , and will introduce errors. The key to the realization of the frequency-shift excitation method is to ensure that there are at least two stable excitation lights with different wavelengths. In the existing technologies, most of them use two lasers with different wavelength output. The wavelength of the laser needs to be controlled by high-precision current and temperature to ensure the stability of the laser wavelength output. Using multiple lasers is not conducive to system integration and increases costs. Another widely used technology is to use a single wavelength-tunable laser to change the excitation wavelength by adjusting the operating temperature and current of the laser or through external cavity feedback. The advantage of this technology is that only one laser source is used to reduce the The system volume is small and the cost is reduced. However, the wavelength change achieved by current adjustment can usually only reach 0.5nm, which cannot meet the detection of substances with a wide spectrum; the temperature adjustment wavelength speed is slow, and the time required for stable adjustment of 1nm is more than 30s, resulting in poor real-time performance of the entire system; The precision level of the device is high, and strict temperature control is required to ensure stable wavelength output, which greatly increases the complexity and cost of the system.

Contents of the invention

The present invention aims to solve the problems of complex structure of the frequency-shift excitation device, poor real-time performance and inability to detect broad-spectrum substances. The method of reversing the original Raman spectrum signal based on the differential Raman spectrum signal has a large amount of calculation and will introduce errors, thereby providing a A signal intensity detection device and method based on tunable laser frequency shift excitation Raman spectroscopy.

A signal strength detection device based on a frequency-shifted excitation Raman spectrum of a tunable laser according to the present invention includes a current driver, a semiconductor laser, a grating, a grating controller, a mirror, a band-pass filter, a first convex lens, Excitation fiber, second convex lens, sample container, high-pass filter, coupling lens group, collection fiber, spectrometer and spectrum analysis module;

The control signal output terminal of the current driver is connected to the control signal input terminal of the semiconductor laser. The collimated beam emitted by the semiconductor laser is incident on the grating, and the grating is fixed on the grating controller. The zeroth order beam diffracted by the grating is incident on the mirror and reflected The light beam reflected by the mirror enters the band-pass filter, and the light beam exiting the band-pass filter enters the first convex lens. Incident to the second convex lens, the second convex lens converges the light beam to the sample container, and the Raman scattered light of the sample in the sample container enters the coupling lens group after passing through the high-pass filter, and the coupling lens group converges the light beam to one end of the collection fiber, collecting The other end of the optical fiber is connected to the optical interface of the spectrometer, and the signal output end of the spectrometer is connected to the signal input end of the spectrum analysis module.

The optical power of the zero-order light beam diffracted by the grating is greater than 100mW, the line width is less than 0.5nm, and the wavelength tuning range is greater than 10nm.

The range of the distance between the first convex lens and the exciting optical fiber is (f ₁ -5 mm) to (f ₁ +5 mm), where f ₁ is the focal length of the first convex lens.

The incident angle θ of the light beam emitted by the above-mentioned semiconductor laser incident on the grating is in the range of: 10°<θ<80°, and θ, the output wavelength λ of the semiconductor laser and the spatial structure period d of the grating satisfy the relationship: λ=2dsinθ.

The above grating swing angle variation Where Δλ is the Raman spectrum linewidth of the substance to be measured.

The optical power of the zeroth-order light beam diffracted by the grating is in the range of 100 mW to 300 mW.

The detection method based on the above-mentioned detection device includes the signal intensity acquisition process and analysis process of Raman spectroscopy:

The signal intensity acquisition process of Raman spectroscopy includes the following steps:

Step 11, the sample to be tested is placed in the sample container, the current driver is turned on, and the laser with a wavelength _of λ1 is irradiated on the sample;

Steps 1 and 2, the spectrometer collects the initial spectrum and sends it to the spectrum analysis module, and the spectrum analysis module conducts a preliminary analysis of the received spectrum to determine the time stability and fluorescence background level of the spectrum;

Step 13, according to the spectral time stability and fluorescence background level in step 12, judge whether the laser power is appropriate, that is, neither destroy the molecular structure of the sample, nor cause the light detection unit of the spectrometer to be saturated by the excited fluorescence. If yes, then execute step 14, if the judgment result is no, then adjust the distance between the first convex lens and the incident end face of the excitation fiber, and return to step 12;

Step 14, the spectral analysis module collects and records the spectral signal intensity R1 _when the excitation wavelength is λ1 _;

Step 15, adjust the deflection angle of the grating through the grating feedback controller so that the excitation wavelength is λ ₂ , and the spectral analysis module collects and records the spectral signal intensity R _{2 when the excitation wavelength is λ 2 ;}

The signal intensity analysis process of Raman spectroscopy includes the following steps:

Step 21, making a difference between the spectral signal intensities R ₁ and R ₂ at two different excitation wavelengths collected and recorded by the spectral analysis module to obtain the initial differential Raman spectral signal intensity D ₀ , D ₀ =R ₂ −R ₁ ;

Step 22, obtain the central wavenumber of the differential signal with the highest intensity in the initial differential Raman spectrum signal intensity D ₀ Respectively for the spectral signal intensities _R1 and _R2 at Integrate within the range of wavenumbers to obtain the values I ₁ and I ₂ representing the excitation light power respectively;

Step two and three, perform power normalization on the spectral signal intensities R ₁ and R ₂ respectively, and then make a difference between the two to obtain a normalized differential Raman spectral signal intensity D, D=R ₂ /I ₂ -R ₁ / I ₁ ;

Step two and four, in Extract normalized differential Raman spectrum signal intensity uniformly over the range A total of N data points, is the Raman spectrum linewidth of the substance to be measured, i=1～N, N is an integer greater than 1;

Step two five, yes The N data points extracted in the range are summed point by point to obtain the Raman spectrum signal intensity value A,

A signal intensity detection device based on tunable laser frequency shift excitation Raman spectroscopy according to the present invention uses a single, no temperature control, no precision mechanical device and tunable wavelength laser combined with the spectrum described in the present invention The signal intensity analysis method realizes the detection device and method of the Raman signal intensity of a strong fluorescent substance. Using a wavelength tunable laser can make the structure of the whole frequency shift excitation system more simplified and compact, which is beneficial to the miniaturization and portability of the system. The output wavelength of the external cavity semiconductor laser is mainly dependent on the grating feedback angle, the physical characteristics of insensitivity to operating temperature changes, and the amplitude and wavelength of the differential spectral signal when the wavelength difference of the excitation light is greater than the Raman spectrum linewidth of the substance to be measured. Difference-independent spectral characteristics, combined with the spectral analysis method described in the present invention, the laser does not need temperature control, has good real-time performance, can ensure the accuracy of measurement, reduces system complexity, reduces system volume and cost, and improves system integration. And stability, the output wavelength of the laser is adjusted by changing the grating feedback angle, the wavelength tuning range is large, and the detection of wide-spectrum substances can be realized. The adjustment of the excitation light power is realized by controlling the coupling efficiency of the free light to the excitation fiber, instead of changing the output power by changing the laser injection current in the traditional technology, which can ensure that the output spectral characteristics of the excitation light do not change, and achieve pure Optical power adjustment. The device of the invention has good compatibility with the existing commercial small-scale spectrometer, and is easy to be applied to build a new Raman spectrum detection system.

A signal intensity detection method based on frequency-shifted excitation Raman spectroscopy of tunable lasers according to the present invention integrates and normalizes the obtained initial differential Raman spectral signals to obtain normalized differential Raman spectral signals, Evenly extract N data points and take the absolute value summation to obtain the Raman spectrum signal intensity value, and then realize the analysis of the sample to be tested. The analysis of the sample to be tested can be realized without inverting the original Raman spectrum signal, the calculation amount is small, and the calculation result is accurate.

Description of drawings

FIG. 1 is a schematic structural diagram of a signal intensity detection device based on frequency-shifted excitation Raman spectroscopy of a tunable laser according to the first embodiment.

Fig. 2 is the normalized Raman spectrum obtained under the excitation of two different wavelengths of the industrial technical material of the fungicide tricyclazole in Embodiment 7.

Fig. 3 is the normalized differential Raman spectrum of the industrial technical material of the fungicide tricyclazole in Embodiment 7.

Detailed ways

Specific Embodiment 1: This embodiment is specifically described in conjunction with FIG. 1. A signal strength detection device based on frequency-shifted excitation Raman spectroscopy of a tunable laser described in this embodiment includes a current driver 1, a semiconductor laser 2, and a grating 3. , grating controller 4, mirror 5, bandpass filter 6, first convex lens 7, excitation fiber 8, second convex lens 9, sample container 10, high-pass filter 11, coupling lens group 12, collection fiber 13, Spectrometer 14 and spectral analysis module 15;

The control signal output terminal of the current driver 1 is connected to the control signal input terminal of the semiconductor laser 2, the collimated beam emitted by the semiconductor laser 2 is incident on the grating 3, and the grating 3 is fixed on the grating controller 4, and the zeroth order after diffraction by the grating 3 The light beam is incident on the reflector 5, the light beam reflected by the reflector 5 is incident on the bandpass filter 6, the light beam emitted by the bandpass filter 6 is incident on the first convex lens 7, and the first convex lens 7 converges the light beam and couples it into the excitation One end of the optical fiber 8, the light beam emitted from the other end of the excitation optical fiber 8 enters the second convex lens 9, the second convex lens 9 converges the light beam to the sample container 10, and the Raman scattered light of the sample in the sample container 10 passes through the high-pass filter 11 After incident to the coupling lens group 12, the coupling lens group 12 converges the light beam to one end of the collection fiber 13, the other end of the collection fiber 13 is connected to the optical interface of the spectrometer 14, and the signal output end of the spectrometer 14 is connected to the signal input end of the spectrum analysis module 15 .

The control signal output terminal of the current driver 1 is connected to the control signal input terminal of the semiconductor laser 2 to provide current excitation for the semiconductor laser 2 and energy for the gain medium in the semiconductor laser 2 chip to make it emit optimal output power. The laser light emitted by the semiconductor laser 2 is collimated by its own collimating mirror and then incident on the grating 3 , which is installed on the grating controller 4 . The yaw and pitch attitude of the grating 3 is controlled by the grating controller 4 to a specific position, and the first-order light beam diffracted by the grating 3 can be fed back to the resonator of the semiconductor laser 2, thereby realizing the functions of longitudinal mode selection and line width compression, through Changing the deflection angle of the grating 3 changes the emission wavelength of the semiconductor laser 2 . The satisfying relationship between the deflection angle θ of the grating 3 and the output wavelength λ of the semiconductor laser 2 and the period d of the spatial structure of the grating 3 is determined by the grating equation: λ=2dsinθ. The zero-order light beam diffracted by the grating 3 is incident on the reflector 5, and the reflector 5 and the grating are installed on the same base to ensure that the propagation direction of the laser beam does not change due to the adjustment of the deflection angle of the grating 3. The light beam reflected by the mirror 5 enters the band-pass filter 6, which only allows the light in the wavelength range of about 10nm near the laser wavelength to pass through, and the transmittance of other bands is less than one thousandth, effectively suppressing Interference of the measurement by the spontaneous emission fluorescence of the semiconductor laser 2. The light beam passing through the band-pass filter 6 is incident on the first convex lens 7, converged and coupled into one end of the excitation fiber 8 through the first convex lens 7, and then emerges from the other end of the excitation fiber 8 and enters the second convex lens 9, passes through the second The light beam converged by the convex lens 9 enters the sample container 10 . The sample container can accommodate both solid and liquid substances, which can realize the detection of substances in both solid and liquid forms. The Raman scattered light of the sample in the sample container 10 enters the coupling lens group 12 after passing through the high-pass filter 11. The high-pass filter 11 is a cut-off filter, and the transmittance of light smaller than the excitation wavelength is less than one thousandth. , can further suppress the interference of the spontaneous emission fluorescence of the semiconductor laser 2 and other background light on the measurement. The scattered light from the sample is converged by the coupling lens group 12 and then incident on one end of the collection fiber 13, the other end of the collection fiber 13 is connected to the optical interface of the spectrometer 14, and the signal output end of the spectrometer 14 is connected to the signal input end of the spectrum analysis module 15. The spectrometer 14 is a miniature grating spectrometer common in the market.

Specific embodiment 2: This embodiment is a further description of the signal strength detection device based on the frequency-shifted excitation Raman spectrum of the tunable laser described in the specific embodiment 1. In this embodiment, the grating 3 diffracted The optical power of the zeroth order beam is greater than 100mW, the line width is less than 0.5nm, and the wavelength tuning range is greater than 10nm.

In the prior art, the wavelength change achieved by current regulation can only reach 0.5 nm, but the wavelength tuning range of this embodiment is greater than 10 nm, which can realize the detection of broadband substances.

Specific Embodiment 3: This embodiment is a further description of the signal strength detection device based on the frequency-shifted excitation Raman spectrum of the tunable laser described in the specific embodiment 1. In this embodiment, the first convex lens 7 and the excitation The distance range of the optical fiber 8 is (f ₁ −5 mm)˜(f ₁ +5 mm), and f ₁ is the focal length of the first convex lens 7 .

When the distance between the first convex lens 7 and the excitation fiber 8 is within the range of (f ₁ -5mm) to (f ₁ +5mm), the light beam can be coupled into the excitation fiber 8, and when the distance exceeds this range, almost no light beam is coupled into the fiber.

Embodiment 4: This embodiment is a further description of the signal strength detection device based on the frequency-shifted excitation Raman spectrum of the tunable laser described in Embodiment 1. In this embodiment, the light beam emitted by the semiconductor laser 2 The range of the incident angle θ to the grating 3 is: 10°<θ<80°, and θ and the output wavelength λ of the semiconductor laser 2 and the spatial structure period d of the grating 3 satisfy the relationship: λ=2dsinθ.

Embodiment 5: This embodiment is a further description of the signal strength detection device based on the frequency-shifted excitation Raman spectrum of the tunable laser described in Embodiment 1. In this embodiment, the swing angle of the grating 3 changes quantity Where Δλ is the Raman spectrum linewidth of the substance to be measured.

Embodiment 6: This embodiment is a further description of the signal strength detection device based on the frequency-shifted excitation Raman spectrum of the tunable laser described in Embodiment 2. In this embodiment, the grating 3 diffracted The optical power of the zeroth order light beam ranges from 100mW to 300mW.

Specific Embodiment 7: This embodiment is described in detail in conjunction with Fig. 2 and Fig. 3. This embodiment is based on the detection method of a signal strength detection device based on frequency-shifted excitation Raman spectroscopy of a tunable laser described in Embodiment 1. , including the signal intensity acquisition process and analysis process of Raman spectroscopy:

The signal intensity acquisition process of Raman spectroscopy includes the following steps:

Step 11, the sample to be tested is placed in the sample container 10, the current driver ₁ is turned on, and the laser with a wavelength of λ1 is irradiated on the sample;

Steps one and two, the spectrometer 14 collects the initial spectrum and sends it to the spectrum analysis module 15, and the spectrum analysis module 15 performs a preliminary analysis on the received spectrum to determine the temporal stability and fluorescence background level of the spectrum;

Step 13, according to the spectral time stability and fluorescence background level in step 12, judge whether the laser power is appropriate, that is, neither destroy the molecular structure of the sample, and the excited fluorescence will not cause the light detection unit of the spectrometer 14 to saturate, if judged If the result is yes, then perform step 14, if the judgment result is no, then adjust the distance between the first convex lens 7 and the incident end face of the excitation fiber 8, and return to step 12;

In step 14, the spectral analysis module 15 collects and records the spectral signal intensity R _{1 when the excitation wavelength is λ 1 ;}

Step 15, adjust the deflection angle of the grating 3 through the grating feedback controller 4, so that the excitation wavelength is λ ₂ , and the spectral analysis module 15 collects and records the spectral signal intensity R _{2 when the excitation wavelength is λ 2 ;}

The signal intensity analysis process of Raman spectroscopy includes the following steps:

Step 21, making a difference between the spectral signal intensities R ₁ and R ₂ at two different excitation wavelengths collected and recorded by the spectral analysis module 15 to obtain the initial differential Raman spectral signal intensity D ₀ , D ₀ =R ₂ −R ₁ ;

Step 22, obtain the central wavenumber of the differential signal with the highest intensity in the initial differential Raman spectrum signal intensity D ₀ Respectively for the spectral signal intensities _R1 and _R2 at Integrate within the range of wavenumbers to obtain the values I ₁ and I ₂ representing the excitation light power respectively;

Step two and three, perform power normalization on the spectral signal intensities R ₁ and R ₂ respectively, and then make a difference between the two to obtain a normalized differential Raman spectral signal intensity D, D=R ₂ /I ₂ -R ₁ / I ₁ ;

Step two and four, in Extract normalized differential Raman spectrum signal intensity uniformly over the range A total of N data points, is the Raman spectrum linewidth of the substance to be measured, i=1～N, N is an integer greater than 1;

Step two five, yes The N data points extracted in the range are summed point by point to obtain the Raman spectrum signal intensity value A,

The Raman spectrum signal intensity represents the concentration of the sample to be tested, and the Raman spectrum signal intensity can be used for quantitative analysis of the concentration of the sample to be tested. The Raman spectral analysis method of the spectral analysis module 15 is based on two points: 1) the output wavelength of the semiconductor laser 2 mainly depends on the deflection angle of the grating 3, and is insensitive to changes in the operating temperature; 2) when the wavelength difference of the excitation light is greater than the In the case of the Raman spectrum linewidth of the measured substance, the amplitude of the differential spectral signal has nothing to do with the wavelength difference. Therefore, as long as the wavelength difference of the excitation light is guaranteed to be greater than the Raman spectrum linewidth of the substance to be measured, even if the laser wavelength fluctuates at the nm level, under the guarantee of the novel Raman spectrum analysis method in the spectrum analysis module 15, the semiconductor laser 2 is also No temperature control is required. Figure 2 is the normalized Raman spectrum obtained under the excitation of two different wavelengths for the industrial technical fungicide tricyclazole. It can be seen that the normalized Raman spectra of the two wavelengths almost overlap, and the two The spectral signal intensities at different wavelengths are subtracted to obtain a normalized differential Raman spectrum, as shown in FIG. 3 .

Claims (7)

1. the shift frequency based on tunable laser excites the signal strength detection device of Raman spectrum, it is characterized in that, it comprises current driver (1), semiconductor laser (2), grating (3), grid controller (4), catoptron (5), bandpass filter (6), first convex lens (7), excitation fiber (8), second convex lens (9), sampling receptacle (10), high-pass filter (11), coupled lens group (12), collect optical fiber (13), spectrometer (14) and spectral analysis module (15),

The control signal output terminal of current driver (1) connects the control signal input end of semiconductor laser (2), the collimated light beam that semiconductor laser (2) sends is incident to grating (3), grating (3) is fixed on grid controller (4), zero order beam after grating (3) diffraction is incident to catoptron (5), light beam after catoptron (5) reflection is incident to bandpass filter (6), the light beam of bandpass filter (6) outgoing is incident to the first convex lens (7), first convex lens (7) are by beams converge and be coupled into one end of excitation fiber (8), the second convex lens (9) are incident to from the light beam of the other end outgoing of excitation fiber (8), second convex lens (9) by beams converge to sampling receptacle (10), in sampling receptacle (10), the Raman diffused light of sample is incident to coupled lens group (12) after high-pass filter (11), coupled lens group (12) is by beams converge one end to collection optical fiber (13), the other end collecting optical fiber (13) connects the optical interface of spectrometer (14), the signal output part of spectrometer (14) connects the signal input part of spectral analysis module (15).

2. a kind of shift frequency based on tunable laser according to claim 1 excites the signal strength detection device of Raman spectrum, it is characterized in that, the luminous power of described zero order beam after grating (3) diffraction is greater than 100mW, live width is less than 0.5nm, and wavelength tuning range is greater than 10nm.

3. a kind of shift frequency based on tunable laser according to claim 1 excites the signal strength detection device of Raman spectrum, it is characterized in that, the distance range of described first convex lens (7) and excitation fiber (8) is (f ₁-5mm) ~ (f ₁+ 5mm), f ₁it is the focal length of the first convex lens (7).

4. a kind of shift frequency based on tunable laser according to claim 1 excites the signal strength detection device of Raman spectrum, it is characterized in that, the scope that the light beam that semiconductor laser (2) sends is incident to the incidence angle θ of grating (3) is: 10 ° of < θ <80 °, and the space structure cycle d of the output wavelength λ of θ and semiconductor laser (2) and grating (3) meets relational expression: λ=2dsin θ.

5. a kind of shift frequency based on tunable laser according to claim 1 excites the signal strength detection device of Raman spectrum, it is characterized in that, grating (3) pendulum inclination angle variable quantity wherein △ λ is test substance Raman spectrum live width.

6. a kind of shift frequency based on tunable laser according to claim 2 excites the signal strength detection device of Raman spectrum, it is characterized in that, the scope of the luminous power of the zero order beam after grating (3) diffraction is 100mW ~ 300mW.

7. excite the detection method of the signal strength detection device of Raman spectrum based on a kind of shift frequency based on tunable laser according to claim 1, it is characterized in that, comprise signal intensity gatherer process and the analytic process of Raman spectrum:

The signal intensity gatherer process of Raman spectrum comprises the following steps:

One by one, be placed on by testing sample in sampling receptacle (10), firing current driver (1), wavelength is λ to step ₁laser be radiated on sample;

Step one two, spectrometer (14) gathers initial spectrum and is delivered to spectral analysis module (15), spectral analysis module (15) does initial analysis to the spectrum received, and judges time degree of stability and the fluorescence background level of spectrum;

Step one three, according to the spectral temporal degree of stability in step one two and fluorescence background level, judge that whether laser power is suitable and namely neither destroy sample molecule structure, the fluorescence excited can not cause again the photo detecting unit of spectrometer (14) saturated, if judged result is yes, then perform step one four, if judged result is no, distance between the incident end face then adjusting the first convex lens (7) and excitation fiber (8), and return step one two;

Step one four, spectral analysis module (15) acquisition and recording excitation wavelength is λ ₁time spectral signal intensity R ₁;

The step First Five-Year Plan, by the deflection angle of grating feedback controller (4) adjustment grating (3), excitation wavelength is made to be λ ₂, spectral analysis module (15) acquisition and recording excitation wavelength is λ ₂time spectral signal intensity R ₂;

The signal strength analysis process of Raman spectrum comprises the following steps:

Step 2 one, by the spectral signal intensity R under two different excitation wavelengths of spectral analysis module (15) acquisition and recording ₁and R ₂do difference, obtain initial differential raman spectral signal intensity D ₀, D ₀=R ₂-R ₁;

Step 2 two, obtains initial differential raman spectral signal intensity D ₀the center wave number of the differential signal that middle intensity is maximum respectively to spectral signal intensity R ₁and R ₂? wave-number range in do integration, obtain respectively and characterize the value I of excitation light power ₁and I ₂;

Step 2 three, to spectral signal intensity R ₁and R ₂carry out power normalization respectively, then the two is done difference and obtain normalized difference raman spectral signal intensity D, D=R ₂/ I ₂-R ₁/ I ₁;

Step 2 four, evenly normalized difference raman spectral signal intensity is extracted in scope amount to N number of data point, for test substance Raman spectrum live width, i=1 ~ N, N be greater than 1 integer;

Step 2 five is right the N number of data point extracted in scope divides pointwise to take absolute value summation, acquisition raman spectral signal intensity level A,