Dual-detector ellipsoid reflective bowl receiving diffuse reflectance spectrometer based on AOTF

Abstract

The present invention discloses a dual-detector ellipsoid reflector receiving diffuse reflection spectrometer based on AOTF. The invention is based on the electrically controlled spectral characteristics of the acousto-optic tunable filter, and adopts dual-detector beam splitting reference calibration to realize real-time spectral calibration and light source performance detection. By adding spatial shielding of 0-order light, two beam splitters and a reflector, the ±1-order diffracted light is irradiated on the same position of the sample surface to increase the irradiation light energy. The sample is placed at one focus of the ellipsoid reflector using diffuse reflection detection, and the signal light receiving device is located at the other focus of the ellipsoid reflector, so as to increase the receiving efficiency of the diffusely emitted signal light of the sample; and the characteristic that the phase-locked circuit is insensitive to 0-order light is utilized to improve the signal-to-noise ratio of spectral detection.

Description

Technical Field

[0001] The invention relates to spectrum detection technology, and in particular to an AOTF-based dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer, which is suitable for the field of material spectrum detection and analysis. Background Art

[0002] Spectroscopic analysis is a technique that uses the absorption spectrum information of a substance to conduct qualitative and quantitative analysis of a substance. It is widely used in agriculture, textiles, pharmaceuticals, biomedicine and other fields. Compared with the spectroscopic devices used in traditional spectral analysis instruments, the AOTF near-infrared spectrometer uses an acousto-optic tunable filter (AOTF), which is a narrow-band tunable filter. It is a spectroscopic device made based on the principle of acousto-optic action. By changing the frequency of the RF drive applied to the crystal, the spectroscopic wavelength is selected to achieve wavelength scanning. It has the advantages of large electrical tuning area, high diffraction rate and good reproducibility. AOTF spectrometers have the advantages of no moving parts, fast wavelength conversion speed, and online analysis, and are increasingly widely used in various occasions.

[0003] There are methods for spectrum detection based on AOTF spectroscopic characteristics in public literature and patents. For example, application publication number CN208902595U discloses an active illumination spectrum detector. The patent uses an active polychromatic light source to converge and illuminate the sample surface, receives diffuse reflected light from the sample surface into the AOTF spectrometer, filters out +1-order diffracted light and 0-order light through a Glan prism, and only detects -1-order diffracted light that converges and enters the detector to achieve spectrum detection. However, the instrument illuminates a very small sample surface area, which easily leads to inaccurate detection results. In addition, this method is not suitable for AOTF spectrometers. Before detecting the sample, it is easy to introduce stray light and waste the -1 order diffraction light energy; the application publication number CN205898677U discloses an acousto-optic modulated dual-path dual-detector near-infrared spectrometer. The patent adopts a dual-path dual-detector design. The monochromatic light after being split by the acousto-optic tunable filter is divided by an adjustable beam splitter into a reference light and a measurement light with a controllable energy splitting ratio for detection. However, the 0th order light is not processed, which is easy to generate a noise floor that affects the signal-to-noise ratio. In addition, the existing spectrometers only use the signal light of a certain angle of the diffusely reflected light, and the receiving efficiency is low. Summary of the invention

[0004] The technical problems that the present invention focuses on solving with respect to the prior art are: failure to fully utilize the ±1 level signal light separated by the AOTF and failure to fully receive the diffusely reflected signal light of the sample, thereby reducing the signal-to-noise ratio of the instrument.

[0005] The purpose of the present invention is to provide a dual-detector ellipsoid reflector receiving diffuse reflection spectrometer based on AOTF. The invention is based on the electrically controlled spectral characteristics of an acousto-optic tunable filter (AOTF), and adopts dual-detector beam splitting reference calibration to realize real-time spectral calibration and light source performance detection. By adding spatial shielding of 0-order light, two beam splitters and a reflector, the ±1-order diffracted light is irradiated on the same position of the sample surface to increase the irradiation light energy. The sample is placed at one focus of the ellipsoid reflector by diffuse reflection detection, and the signal light receiving device is located at the other focus of the ellipsoid reflector, thereby increasing the receiving efficiency of the diffusely emitted signal light of the sample. The phase-locked circuit is insensitive to 0-order light to improve the signal-to-noise ratio of spectral detection. The invention has high signal-to-noise ratio, compact structure, fast detection speed, and is easy and convenient to use. It is suitable for the detection of ingredients such as food and medicine.

[0006] The light source spectroscopic module 1 is composed of a wide-spectrum halogen light source 11, a collimating lens group 12, an acousto-optic tunable filter 13, a primary converging lens group 14 and a 0-order light baffle 15; the light beam emitted by the wide-spectrum halogen light source 11 passes through the collimating lens group 12 to emit collimated light and enter the acousto-optic tunable filter 13. When the acousto-optic tunable filter 13 is not working, diffracted light cannot be generated. When the acousto-optic tunable filter 13 works at a certain radio frequency, light of a certain wavelength will be separated into two beams of orthogonally polarized single-wavelength diffracted light and a beam of 0-order complex color light. The three beams of light are converged and separated after passing through the primary converging lens group 14. The 0-order light baffle 15 blocks the 0-order light, and the ±1-order diffracted light is emitted from both sides.

[0007] The wide-spectrum halogen light source 11 is a halogen bulb with a lens at the front end.

[0008] The collimating lens group 12 is a two-piece lens group with a small aperture stop inside, and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

[0009] The acousto-optic tunable filter 13 is a spectrometer light splitting device, which has no internal achromatic design and can separate 0th order complex light and ±1st order monochromatic diffracted light with a certain angle.

[0010] The primary converging lens group 14 is a two-piece lens group, and the lens surface is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

[0011] The ±1-level signal light reference and output module 2 is composed of a -1-level flat plate beam splitter 21, a +1-level flat plate beam splitter 22, a secondary converging lens 23, a reference detector 24, a -1-level reflector 25, a +1-level reflector 26 and a sample stage 27; the ±1-level diffracted light is respectively reflected into the secondary converging lens 23 and the reference detector 24 in sequence through the common optical path of the -1-level flat plate beam splitter 21 and the +1-level flat plate beam splitter 22 to complete the reference detection, and the ±1-level diffracted light transmitted through the -1-level flat plate beam splitter 21 and the +1-level flat plate beam splitter 22 is respectively irradiated onto the sample surface on the sample stage 27 through the -1-level reflector 25 and the +1-level reflector 26 to generate diffuse reflected light.

[0012] The -1 level flat beam splitter 21 and the +1 level flat beam splitter (22) are flat window plates, the surfaces of which are coated with a transflective film having a wavelength band suitable for the spectrometer and a ratio of 90:10;

[0013] The secondary converging lens 23 is a plano-convex lens, and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

[0014] The reference detector 24 is a unit detector corresponding to the applicable waveband of the spectrometer.

[0015] The surfaces of the -1st-level reflector 25 and the +1st-level reflector (26) are coated with a reflective film of a wavelength band applicable to the spectrometer.

[0016] The sample stage 27 is a quartz glass flat plate, and the surface of the flat plate is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

[0017] The spectrum receiving module 3 is composed of an ellipsoid reflective bowl 31, a receiving lens group 32 and a receiving detector 33; the diffusely reflected signal light on the sample surface is converged into the receiving lens group 32 through the ellipsoid reflective bowl 31, and finally collected into the receiving detector 33, thereby realizing the characteristic spectrum detection of the material.

[0018] The ellipsoid reflective bowl 31 uses aluminum as a base material, and the inside of the reflective bowl is coated with a reflective film of a wavelength band applicable to the spectrometer.

[0019] The receiving lens group 32 is a three-piece lens group, and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

[0020] The receiving detector 33 adopts the same unit detector as the reference detector (24).

[0021] The data acquisition and control module 4 is composed of a main control module 41, a radio frequency power amplifier 42, an analog signal processing circuit 43, a reference detector preamplifier circuit 44 and a receiving detector preamplifier circuit 45, wherein the main control module 41 further includes a computer 411, a USB communication circuit 412, an FPGA main control circuit 413, a radio frequency drive signal generating circuit 414, a TEC closed-loop cooling circuit 415, a reference optical path A / D conversion circuit 416 and a receiving optical path A / D conversion circuit 417; when the spectrum detector is working, the computer 411 in the main control module 41 sends a spectrum acquisition instruction to the USB communication circuit 412, and controls the spectrum acquisition system to work through the FPGA main control circuit 413; the FPGA main control circuit 413 controls the radio frequency drive signal generating circuit 414 to generate a radio frequency signal of the required frequency and modulate the output, and the radio frequency power amplifier 43 amplification, and applied to the acousto-optic tunable filter 13; the FPGA main control circuit 413 controls the TEC closed-loop cooling circuit 415 to perform closed-loop cooling control on the infrared detector; the analog signal processing circuit 44 performs phase-locked amplification processing on the weak modulated spectral signal received by the reference detector preamplifier circuit 44 and the receiving detector preamplifier circuit 45, the FPGA main control circuit 413 controls the reference optical path A / D conversion circuit 416 and the receiving optical path A / D conversion circuit 417 to perform A / D conversion on the spectral signal output by the analog signal processing circuit 44, and the FPGA main control circuit 413 packages the spectral data and sends it to the computer 411 through the USB communication circuit 412; the optical signal received by the detector is amplified by phase-locked amplification, and the gain of the system can be adjusted programmably to improve the signal-to-noise ratio and flexibility of spectral acquisition while ensuring the sampling speed.

[0022] The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF is characterized by the following steps:

[0023] 1) Equipment power-on self-test

[0024] Connect the power supply to the wide-spectrum halogen light source 11 and the data acquisition and control module 4, connect the computer 411 and the USB communication circuit 412, and open the host computer software to establish a communication connection with the spectrometer;

[0025] 2) Preheat the equipment and prepare before work

[0026] 2-1) Turn on the TEC closed-loop cooling circuit 415 to perform closed-loop cooling control on the reference detector 24 and the receiving detector 33 until the detector cooling is stable;

[0027] 2-2) The optical signal output by the wide-spectrum halogen light source 11 becomes more stable after being powered on for a period of time, and a sample to be tested is placed on the sample stage 27 .

[0028] 3) Spectral data collection

[0029] 3-1) The FPGA main control circuit 413 controls the operation of the RF drive signal generating circuit 414, applies RF drive signals of different frequencies to the acousto-optic tunable filter 13, performs spectral scanning on scattered light of different wavelengths of the object to be measured, and simultaneously detects the monochromatic light after the acousto-optic tunable filter 13 and the monochromatic light diffusely reflected by the sample to be measured through the reference detector 24 and the receiving detector 33;

[0030] 3-2) The weak light signals detected by the reference detector 24 and the receiving detector 33 are synchronously entered into the analog signal processing circuit 43 after being amplified in the pre-stage, and the FPGA main control circuit 413 synchronously controls the reference light path A / D conversion circuit 416 and the receiving light path A / D conversion circuit 417 to sample and save the signals output by the analog signal processing circuit 43. After the full spectrum scan is completed, the reference calibration spectrum and the target spectrum are transmitted to the host computer through the USB communication circuit 412;

[0031] 4) Data analysis and processing

[0032] 4-1) Calculate the absorbance curve of the sample to be tested within the measurement wavelength range by comparing the reference calibration spectrum curve and the target spectrum curve;

[0033] 4-2) Determine the composition and content of the sample by comparing the absorbance curve of the sample with the standard model.

[0034] The advantages of this invention are mainly reflected in: 1. The 0-order light generated after AOTF splitting is blocked, and the ±1-order diffracted light is reflected to the same optical path through two plane beam splitters for reference reception, which can be used for real-time calibration detection and monitoring of light source stability; 2. Two plane reflectors are used to irradiate the ±1-order diffracted light to the same position of the sample stage, making full use of the ±1-order diffracted light, enhancing the light energy irradiated on the sample and thus increasing the diffuse reflection signal light of the sample; 3. The reflection principle of the ellipsoid reflective bowl is used to make the diffuse reflection signal light of the sample fully reflected to the receiving lens group, effectively improving the signal-to-noise ratio of the instrument. The spectral detection method based on this model can be used in other optical detection fields, and has important application value and reference significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the overall structure of the instrument.

[0036] Figure 2 Schematic diagram of the working principle of the data acquisition and control module 4. DETAILED DESCRIPTION

[0037] The present invention is a dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF, which includes a light source spectroscopic module 1, a ±1 level signal light reference and emission module 2, a spectrum receiving module 3 and a data acquisition and control module 4. Figure 1 The structure features and implementation methods of the present invention are shown.

[0038] The main components used in the present invention are described as follows:

[0039] 1) Broad-spectrum halogen light source 11: In this embodiment, the broad-spectrum halogen light source 11 adopts a stable infrared tungsten light source from Thorlabs, with a spectral range of 350-2500nm.

[0040] 2) Collimating lens group 12, primary converging lens group 14, secondary converging lens 23, -1 level flat plate beam splitter 21, +1 level flat plate beam splitter 22, -1 level reflector 25, +1 level reflector 26 and receiving lens group 32: The collimating lens group 12, primary converging lens group 14, secondary converging lens 23, -1 level flat plate beam splitter 21, +1 level flat plate beam splitter 22, -1 level reflector 25, +1 level reflector 26 and receiving lens group 32 used in this embodiment are all self-designed components, and their operating wavelength range is 1100-2300nm to achieve collimation, convergence, transflection and reception of diffuse reflection signal light in the optical path.

[0041] 3) Acousto-optic tunable filter 13: The acousto-optic tunable filter 13 used in this embodiment is a customized product of the 26th Institute of China Electronics Technology Group Corporation, and its main technical indicators are:

[0042] a) Working wavelength: 1100nm-2300nm

[0043] b) Spectral resolution: 2nm-12nm

[0044] c) Primary deflection angle: 2.6°

[0045] d) Separation angle: >=6.1°

[0046] e) Diffraction efficiency: >=60%

[0047] f) Dimensions: 560mm*400mm*315mm

[0048] g) Driving power: <=2W

[0049] h) Driving frequency range: 37MHz-112MHz

[0050] 4) Sample stage 27: In this embodiment, double-sided polished quartz is used as the window piece of sample stage 27, which can ensure that the light source with a wavelength of 900-2500nm can illuminate the object to be measured through the quartz window. The surface accuracy requirement of the double-sided polished surface of quartz is that the RMS value is less than λ / 10@632.8nm.

[0051] 5) Reference detector 24 and receiving detector 33: In this embodiment, the Judson J23TE2-66C InGaAs infrared detector is selected, and its main technical indicators are: its photosensitive area is The spectral response range is 0.9~2.5μm, the maximum dark current is 1.0E-5A; detection rate: 8.4E 11 cmHz 1 / 2 W -1 ,2-stage TEC cooling.

[0052] The present invention relates to a dual-detector ellipsoid reflector receiving diffuse reflection spectrometer based on AOTF, which has the characteristics of compact structure, small size, high signal-to-noise ratio, high accuracy and simple detection method. Compared with the traditional AOTF spectrum detection method, the dual-detector beam splitting reference can be used for real-time calibration detection and monitoring of light source performance stability. By adding spatial shielding of 0-order light, two beam splitters and a reflector, the ±1-order diffracted light is irradiated on the same position of the sample surface to increase the irradiation light energy. The sample is placed at one focus of the ellipsoid reflector by diffuse reflection detection, and the signal light receiving device is located at the other focus of the ellipsoid reflector, thereby increasing the receiving efficiency of the sample diffusely emitted signal light; and the characteristic that the phase-locked circuit is insensitive to 0-order light is utilized to improve the spectrum detection signal-to-noise ratio.

Claims

1. A dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF, comprising a light source spectroscopic module (1), a ±1 level signal light reference and output module (2), a spectrum receiving module (3) and a data acquisition and control module (4); characterized in that: The light source spectrometer module (1) provides an active light source and splits it to generate level 0 and level ±1 signal light. Subsequently, the level ±1 signal light enters the level ±1 signal light reference and output module (2), a portion of which is used for reference calibration, and a portion of the diffuse reflection light generated by irradiating the sample enters the spectrum receiving module (3) for sample spectrum acquisition and detection. The data acquisition and control module (4) is used to control the operation of the whole machine and the acquisition and processing of the spectrum. The light source splitting module (1) is composed of a wide-spectrum halogen light source (11), a collimating lens group (12), an acousto-optic tunable filter (13), a primary converging lens group (14) and a 0-order light baffle (15); the light beam emitted by the wide-spectrum halogen light source (11) passes through the collimating lens group (12) to emit collimated light and enters the acousto-optic tunable filter (13); when the acousto-optic tunable filter (13) is not working, diffracted light cannot be generated; when the acousto-optic tunable filter (13) works at a certain radio frequency frequency, light of a certain wavelength is separated into two beams of orthogonally polarized single-wavelength diffracted light and a beam of 0-order complex color light; the three beams of light are converged and separated after passing through the primary converging lens group (14); the 0-order light baffle (15) blocks the 0-order light, and ±1-order diffracted light is emitted from both sides; The ±1-level signal light reference and output module (2) is composed of a -1-level flat plate beam splitter (21), a +1-level flat plate beam splitter (22), a secondary convergence lens (23), a reference detector (24), a -1-level reflector (25), a +1-level reflector (26) and a sample stage (27); the ±1-level diffracted light is respectively reflected into the secondary convergence lens (23) and the reference detector (24) in sequence through the common optical path of the -1-level flat plate beam splitter (21) and the +1-level flat plate beam splitter (22) to complete the reference detection; the ±1-level diffracted light transmitted through the -1-level flat plate beam splitter (21) and the +1-level flat plate beam splitter (22) is respectively irradiated onto the sample surface on the sample stage (27) through the -1-level reflector (25) and the +1-level reflector (26) to generate diffuse reflected light.

2. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The wide-spectrum halogen light source (11) is a halogen bulb with a lens at the front end.

3. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The collimating lens group (12) is a two-piece lens group with a small aperture stop inside, and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

4. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The acousto-optic tunable filter (13) is a spectrometer light splitting device, has no internal achromatic design, and can separate 0th order complex light and ±1st order monochromatic diffracted light with a certain angle.

5. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The primary converging lens group (14) is a two-piece lens group, and the lens surface is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

6. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The -1 level flat beam splitter (21) and the +1 level flat beam splitter (22) are flat window plates, the surfaces of which are coated with a transflective film having a wavelength band suitable for the spectrometer and a ratio of 90:

10.

7. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The secondary converging lens (23) is a plano-convex lens, and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

8. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The reference detector (24) is a unit detector corresponding to the applicable wavelength band of the spectrometer.

9. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The surfaces of the -1-level reflector (25) and the +1-level reflector (26) are coated with a reflective film of a wavelength band applicable to the spectrometer.

10. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The sample stage (27) is a quartz glass flat plate, and the surface of the flat plate is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

11. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 1, characterized in that: The spectrum receiving module (3) is composed of an ellipsoid reflective bowl (31), a receiving lens group (32) and a receiving detector (33); the sample and the receiving lens group (32) are respectively placed at two focal points of the ellipsoid reflective bowl, and the diffusely reflected signal light on the surface of the sample is converged into the receiving lens group (32) through the ellipsoid reflective bowl (31), and finally collected into the receiving detector (33), thereby realizing the characteristic spectrum detection of the material.

12. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 11, characterized in that: The ellipsoid reflective bowl (31) uses aluminum as a base material, and the interior of the reflective bowl is coated with a reflective film of a wavelength band applicable to the spectrometer.

13. The dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer based on AOTF according to claim 11, characterized in that: The receiving lens group (32) is a three-piece lens group, and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

14. The AOTF-based dual-detector ellipsoidal reflective bowl receiving diffuse reflection spectrometer according to claim 11, characterized in that: The receiving detector (33) adopts the same unit detector as the reference detector (24).

15. The AOTF-based dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer according to claim 11, characterized in that: The data acquisition and control module (4) is composed of a main control module (41), a radio frequency power amplifier (42), an analog signal processing circuit (43), a reference detector preamplifier circuit (44) and a receiving detector preamplifier circuit (45), wherein the main control module (41) further comprises a computer (411), a USB communication circuit (412), an FPGA main control circuit (413), a radio frequency drive signal generating circuit (414), a TEC closed-loop cooling circuit (415), a reference optical path A / D conversion circuit (416) and a receiving optical path A / D conversion circuit (417); when the spectrum detector is working, the computer (411) in the main control module (41) sends a spectrum acquisition instruction to the USB communication circuit (412), and controls the spectrum acquisition system to work through the FPGA main control circuit (413); The FPGA main control circuit (413) controls the radio frequency drive signal generating circuit (414) to generate a radio frequency signal of a required frequency and modulates the signal for output, amplifies the signal through the radio frequency power amplifier (42), and applies the signal to the acousto-optic tunable filter (13); the FPGA main control circuit (413) controls the TEC closed-loop cooling circuit (415) to perform closed-loop cooling control on the infrared detector; the analog signal processing circuit (43) performs phase-locked amplification processing on the weak modulated spectrum signal received by the reference detector preamplifier circuit (44) and the receiving detector preamplifier circuit (45); The PGA main control circuit (413) controls the reference optical path A / D conversion circuit (416) and the receiving optical path A / D conversion circuit (417) to perform A / D conversion on the spectral signal output by the analog signal processing circuit (43); the FPGA main control circuit (413) packages the spectral data and sends it to the computer (411) via the USB communication circuit (412); a phase-locked amplification method is used to amplify the optical signal received by the detector, and the gain of the system can be adjusted programmably, thereby improving the signal-to-noise ratio and flexibility of spectral acquisition while ensuring the sampling speed.

16. A method for implementing the AOTF-based dual-detector ellipsoid reflective bowl receiving diffuse reflection spectrometer as claimed in claim 15, characterized in that The steps are as follows: 1) Equipment power-on self-test Connecting a power source to power the wide-spectrum halogen light source (11) and the data acquisition and control module (4), connecting the computer (411) and the USB communication circuit (412), and opening the upper computer software to establish a communication connection with the spectrometer; 2) Preheat the equipment and prepare before work 2-1) turning on the TEC closed-loop cooling circuit (415) to perform closed-loop cooling control on the reference detector (24) and the receiving detector (33) until the cooling of the detectors is stable; 2-2) The optical signal output by the wide-spectrum halogen light source (11) becomes more stable after being powered on for a period of time, and a sample to be tested is placed on the sample stage (27); 3) Spectral data collection 3-1) The FPGA main control circuit (413) controls the operation of the radio frequency drive signal generating circuit (414), applies radio frequency drive signals of different frequencies to the acousto-optic tunable filter (13), performs spectral scanning on scattered light of different wavelengths of the object to be measured, and simultaneously detects the monochromatic light after being split by the acousto-optic tunable filter (13) and the monochromatic light diffusely reflected by the sample to be measured through the reference detector (24) and the receiving detector (33); 3-2) The weak light signals detected by the reference detector (24) and the receiving detector (33) are synchronously entered into the analog signal processing circuit (43) after being amplified in the pre-stage, and the FPGA main control circuit (413) synchronously controls the reference light path A / D conversion circuit (416) and the receiving light path A / D conversion circuit (417) to sample and save the signal output by the analog signal processing circuit (43), and after the full spectrum scan is completed, the reference calibration spectrum and the target spectrum are transmitted to the host computer through the USB communication circuit (412); 4) Data analysis and processing 4-1) By comparing the reference calibration spectrum curve and the target spectrum curve, calculate the absorbance curve of the sample to be tested within the measurement wavelength range; 4-2) Determine the composition and content of the sample by comparing the absorbance curve of the sample with the standard model.

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