A rotating cup detection diffuse reflection spectrometer based on AOTF and its implementation method

Abstract

The present invention discloses a rotating cup detection diffuse reflection spectrometer based on AOTF and an implementation method. The invention is based on the electrically controlled spectroscopic characteristics of an acousto-optic tunable filter. The monochromatic light after diffraction and spectrometry by the AOTF is irradiated onto the sample surface in the rotating cup. The light diffusely reflected by the surface sample is detected by a receiving device. A dual-detector beam splitting reference calibration is used to realize real-time spectrum calibration and light source performance detection. By adding a spatial shielding, a spectrometer and a plane reflector to the 0-order light, the ±1-order diffracted light is irradiated onto the sample surface together, increasing the light energy irradiated onto the sample. Different areas of the same sample are detected by a rotating cup, the sample is fully and evenly analyzed, and the accuracy of spectrum detection is improved. The characteristic of the phase-locked circuit being insensitive to the 0-order light is used in electronics to improve the signal-to-noise ratio of spectrum detection.

Description

Technical Field

[0001] The present invention relates to spectrum detection technology, in particular to a rotating cup detection diffuse reflection spectrometer based on AOTF, which is suitable for the field of spectrum detection and analysis of powder, granule and liquid substances. Background Art

[0002] Acousto-optic tunable filter (AOTF) is a narrowband tunable filter, which is a spectroscopic device made according to the principle of acousto-optic action. The wavelength of the spectroscopic light is selected by changing the frequency of the RF drive applied to the crystal, thereby realizing wavelength scanning. The monochromatic light diffracted by the AOTF at a certain frequency is irradiated on the object to be tested, and the monochromatic light of the same wavelength is scattered. The monochromatic light can reflect the absorption characteristics of the material, thereby realizing the detection of the spectral characteristics of the material. At present, this technology has been widely used in various types of spectral instruments.

[0003] There are methods for spectral detection based on the AOTF spectroscopic characteristics in public documents and patents. For example, application publication number CN208902595U discloses an active illumination spectroscopic detector. The patent uses an active polychromatic light source to converge and illuminate the sample surface, receives diffuse reflected light from the sample surface and enters the AOTF spectroscopic method, 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 spectral detection. However, the instrument illuminates a very small area on the sample surface, which easily leads to inaccurate detection results. In addition, this method detects the sample before AOTF spectroscopic method, which easily introduces stray light and wastes the -1-order diffracted light energy. 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 into reference light and measurement light with controllable energy splitting ratio by an adjustable beam splitter for detection. However, the 0-order light is not processed, which easily generates a noise floor that affects the signal-to-noise ratio. Summary of the invention

[0004] The technical problems that the present invention needs to solve with respect to the prior art are: the prior AOTF detection technology cannot fully utilize the ±1 level signal light separated by the AOTF, which reduces the signal-to-noise ratio of the instrument, and the uniformity of the sample detection cannot be guaranteed when detecting a spectrum of the sample, thereby affecting the accuracy of the spectrum detection. The present invention fully utilizes the ±1 level signal light and combines the rotating sample cup detection method to effectively solve the above problems, thereby improving the signal-to-noise ratio of the instrument and the accuracy of spectrum detection.

[0005] The purpose of the present invention is to provide a rotating cup detection diffuse reflection spectrometer based on AOTF and an implementation method. The invention is based on the splitting function of electrically controllable splitting devices such as acousto-optic tunable filters, uses an active illumination light source and a splitting module to generate monochromatic light to illuminate the object to be tested, and the diffuse scattered light of the object to be tested enters the detector through a receiving lens group, thereby detecting the spectral characteristics of the scattered light, and at the same time, before irradiating the object to be tested, a part is separated for standard calibration spectrum detection, and the two are compared to analyze the component information of the object to be tested, and a dual-detector beam splitting reference calibration is used to realize real-time spectrum calibration and light source performance detection, and by adding a spatial shielding of 0-level light, a splitter and a plane reflector, the ±1-level diffracted light is irradiated on the sample surface together, increasing the light energy irradiated on the sample, and detecting different areas of the same sample by a rotating cup, fully and evenly analyzing the sample, improving the accuracy of spectrum detection, and using the characteristics of the phase-locked circuit being insensitive to 0-level light in electronics to improve the spectrum detection signal-to-noise ratio. The overall instrument has a compact structure, fast detection speed and high precision.

[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 diaphragm 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 0-order complex light and ±1-order monochromatic diffracted light with a certain angle;

[0010] The primary converging lens group 14 is a two-piece lens group, which is used to converge the light beam after being split by the acousto-optic tunable filter 13, and the surface of the lens 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 convergence lens 23, a reference detector 24, a -1-level reflector 25, a +1-level reflector 26 and a sample cup 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, 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 to be tested in the sample cup 27 through the -1-level reflector 25 and the +1-level reflector 26.

[0012] The -1 level flat beam splitter 21 and +1 level flat beam splitter 22 are quartz plane windows, with the surface coated with a transflective film with a wavelength band suitable for the spectrometer and a ratio of 90:10;

[0013] The secondary converging lens 23 is a plano-convex lens, which converges the ±1-level signal light reflected by the flat beam splitter into the reference detector 24, 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 -1 level reflector 25 and +1 level reflector 26 are 45° plane reflectors, which refract the ±1 level signal light transmitted by the flat beam splitter to the sample stage 27. The reflector surface is coated with a reflective film of a wavelength band applicable to the spectrometer.

[0016] A quartz glass plate is installed at the bottom of the sample cup 27 for carrying samples and transmitting light, and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer;

[0017] The spectrum receiving module 3 is composed of a receiving lens group 31 and a receiving detector 32; the signal light diffusely reflected by the sample part is collected by the receiving lens group 31 and enters the receiving detector 32, thereby realizing the characteristic spectrum detection of the material.

[0018] The receiving lens group 31 is a three-piece lens group, which gathers the light received from the sample cup 27 into the receiving detector 32, and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer;

[0019] The receiving detector 32 uses the same unit detector as the reference detector 24;

[0020] The rotating cup control module 4 is composed of a rotating motor drive module 41, a rotating cup rotation control motor 42, a rotating cup rotation driving gear 43 and a rotating cup rotation driven gear 44; the rotating motor drive module 41 controls the rotating cup rotation control motor 42, and the motor drives the rotating cup rotation driving gear 43 to rotate, thereby rotating the rotating cup rotation driven gear 44 to realize spectral detection of different positions of the sample in the rotating cup.

[0021] The data acquisition and control module 5 is composed of a main control module 51, a radio frequency power amplifier 52, an analog signal processing circuit 53, a reference detector preamplifier circuit 54 and a receiving detector preamplifier circuit 55, wherein the main control module 51 further includes a computer 511, a USB communication circuit 512, an FPGA main control circuit 513, an RS485 communication circuit 514, a radio frequency drive signal generating circuit 515, a TEC closed-loop cooling circuit 516, a reference optical path A / D conversion circuit 517 and a receiving optical path A / D conversion circuit 518; when the spectrum detector is working, the computer 511 in the main control module 51 sends a spectrum acquisition instruction to the USB communication circuit 512, and controls the spectrum acquisition system to work through the FPGA main control circuit 513; the FPGA main control circuit 513 sends a motor drive instruction via the RS485 communication circuit 514 to control the rotating motor drive module 41 to drive the rotating cup control module 4 to work, and the FPGA main control circuit 513 controls the radio frequency drive The signal generating circuit 515 generates a radio frequency signal of the required frequency and modulates the output, which is amplified by the radio frequency power amplifier 52 and applied to the acousto-optic tunable filter 13; the FPGA main control circuit 513 controls the TEC closed-loop cooling circuit 516 to perform closed-loop cooling control on the infrared detector; the analog signal processing circuit 53 performs phase-locked amplification processing on the weak modulated spectral signal received by the reference detector preamplifier circuit 54 and the receiving detector preamplifier circuit 55, the FPGA main control circuit 513 controls the reference optical path A / D conversion circuit 517 and the receiving optical path A / D conversion circuit 518 to perform A / D conversion on the spectral signal output by the analog signal processing circuit 53, and the FPGA main control circuit 513 packages the spectral data and sends it to the computer through the USB communication circuit 512; 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 method of the rotating cup detection diffuse reflectance spectrometer based on AOTF is characterized in that the method steps are as follows:

[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 5, connect the computer 511 and the USB communication circuit 512, 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 516 to perform closed-loop cooling control on the reference detector 24 and the receiving detector 32 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. A sample to be tested is placed in the sample cup 27 .

[0028] 2-3) Sending a rotation instruction to enable the rotating cup to rotate the control motor 42, the motor drives the rotating cup to rotate the driving gear 43, and the rotating cup rotates the driven gear 44 to obtain uniform spectrum data of the sample to be tested, and then go to step 2) to collect spectrum data to obtain spectrum data of the sample to be tested;

[0029] 3) Spectral data collection

[0030] 3-1) The FPGA main control circuit 513 controls the operation of the RF drive signal generating circuit 515, 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 32;

[0031] 3-2) The weak light signals detected by the reference detector 24 and the receiving detector 32 are synchronously entered into the analog signal processing circuit 53 after being amplified in the pre-stage, and the FPGA main control circuit 513 synchronously controls the reference optical path A / D conversion circuit 517 and the receiving optical path A / D conversion circuit 518 to sample and save the signals output by the analog signal processing circuit 53. 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 512;

[0032] 4) Data analysis and processing

[0033] 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;

[0034] 4-2) Determine the composition and content of the sample by comparing the absorbance curve of the sample with the standard model.

[0035] The advantages of this invention are mainly reflected in: 1. The 0-order light generated after AOTF splitting is blocked, and the ±1-order diffraction light is reflected to the same optical path through two plane beam splitters for reference reception to achieve real-time calibration detection and light source stability monitoring; 2. Two plane reflectors are used to irradiate the ±1-order diffraction light to the same position of the quartz window, making full use of the ±1-order diffraction light, enhancing the detection signal intensity, and improving the signal-to-noise ratio; 3. The rotating cup device is used to detect different areas of the same sample, fully and evenly analyzing the sample and improving the accuracy of spectral detection. 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

[0036] Figure 1 This is a schematic diagram of the overall structure of the instrument.

[0037] Figure 2 Schematic diagram of the working principle of the data acquisition and control module 5. DETAILED DESCRIPTION

[0038] The present invention is a rotating cup detection diffuse reflectance spectrometer based on AOTF, which includes a light source spectrometer module 1, a ±1 level signal light reference and output module 2, a spectrum receiving module 3, a rotating cup control module 4 and a data acquisition and control module 5; as shown in the figure, it is used to illustrate the structural features and implementation methods of the present invention.

[0039] The main components used in the present invention are described as follows:

[0040] 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.

[0041] 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 31: 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 31 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.

[0042] 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:

[0043] a) Working wavelength: 1100nm-2300nm

[0044] b) Spectral resolution: 2nm-12nm

[0045] c) Primary deflection angle: 2.6°

[0046] d) Separation angle: >=6.1°

[0047] e) Diffraction efficiency: >=60%

[0048] f) Dimensions: 560mm*400mm*315mm

[0049] g) Driving power: <=2W

[0050] h) Driving frequency range: 37MHz-112MHz

[0051] 4) Sample cup 27: In this embodiment, the cup bottom uses a double-sided polished quartz plate as the cup bottom, and the surface of the plate is coated with a 900-2300nm anti-reflection film. The surface accuracy requirement of the double-sided polished quartz is that the RMS value is less than λ / 10@632.8nm.

[0052] 5) Reference detector 24 and receiving detector 32: 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.

[0053] The present invention relates to a rotating cup detection diffuse reflectance 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 0th order light generated after AOTF splitting is blocked, and the ±1st order diffraction light is reflected to the same optical path through two plane beam splitters for reference reception. Two plane reflectors are used to irradiate the ±1st order diffraction light to the same position of the quartz window, which makes full use of the ±1st order diffraction light, enhances the detection signal intensity, improves the signal-to-noise ratio, uses a rotating cup to rotate and detect different areas of the same sample, fully and evenly analyzes the sample, and improves the accuracy of spectrum detection.

Claims

1. A rotating cup detection diffuse reflectance spectrometer based on AOTF, comprising a light source spectrometer module (1), a ±1 level signal light reference and output module (2), a spectrum receiving module (3), a rotating cup control module (4) and a data acquisition and control module (5); That The basic characteristics are: The light source spectroscopic 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 emission module (2), a portion of which is used for reference calibration, and a portion of which is irradiated on the sample. The diffuse reflection signal light generated by the sample enters the spectrum receiving module (3) for sample spectrum collection and detection. The rotating cup control module (4) is used to rotate the sample for uniform detection. The data collection and control module (5) is used to control the operation of the whole machine and the collection 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 cup (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 to be tested in the sample cup (27) through the -1-level reflector (25) and the +1-level reflector (26).

2. The rotating cup detection diffuse reflectance 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 AOTF-based rotating cup detection diffuse reflectance spectrometer 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 rotating cup detection diffuse reflectance 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 AOTF-based rotating cup detection diffuse reflectance spectrometer according to claim 1, characterized in that: The primary converging lens group (14) is a two-piece lens group, which is used to converge the light beam after being split by the acousto-optic tunable filter (13), and the surface of the lens is coated with an anti-reflection film of a wavelength band applicable to the spectrometer.

6. The AOTF-based rotating cup detection diffuse reflectance spectrometer according to claim 1, characterized in that: The -1 level flat plate beam splitter (21) and the +1 level flat plate beam splitter (22) are quartz plane 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 AOTF-based rotating cup detection diffuse reflectance spectrometer 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 AOTF-based rotating cup detection diffuse reflectance spectrometer 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 rotating cup detection diffuse reflectance spectrometer based on AOTF according to claim 1, characterized in that: The -1-level reflector (25) and the +1-level reflector (26) are 45-degree plane reflectors, and the surfaces of the reflectors are coated with a reflective film of a wavelength band applicable to the spectrometer.

10. The AOTF-based rotating cup detection diffuse reflectance spectrometer according to claim 1, characterized in that: A quartz glass flat plate is installed at the bottom of the sample cup (27), and a reflectivity-enhancing film of a wavelength band applicable to the spectrometer is coated on the surface.

11. The rotating cup detection diffuse reflectance spectrometer based on AOTF according to claim 1, characterized in that: The spectrum receiving module (3) is composed of a receiving lens group (31) and a receiving detector (32); the signal light diffusely reflected by the sample portion is collected by the receiving lens group (31) and enters the receiving detector (32), thereby realizing the characteristic spectrum detection of the material.

12. The AOTF-based rotating cup detection diffuse reflectance spectrometer according to claim 11, characterized in that: The receiving lens group (31) 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.

13. The AOTF-based rotating cup detection diffuse reflectance spectrometer according to claim 11, characterized in that: The receiving detector (32) adopts the same unit detector as the reference detector (24).

14. The rotating cup detection diffuse reflectance spectrometer based on AOTF according to claim 11, characterized in that: The rotating cup control module (4) is composed of a rotating motor driving module (41), a rotating cup rotation enabling control motor (42), a rotating cup rotation driving gear (43) and a rotating cup rotation driven gear (44); the rotating motor driving module (41) controls the rotating cup rotation enabling control motor (42), and the motor drives the rotating cup rotation driving gear (43) to rotate, thereby rotating the rotating cup rotation driven gear (44) to realize spectral detection of different positions of the sample in the rotating cup.

15. The AOTF-based rotating cup detection diffuse reflectance spectrometer according to claim 14, characterized in that: The data acquisition and control module (5) is composed of a main control module (51), a radio frequency power amplifier (52), an analog signal processing circuit (53), a reference detector preamplifier circuit (54) and a receiving detector preamplifier circuit (55), wherein the main control module (51) further comprises a computer (511), a USB communication circuit (512), an FPGA main control circuit (513), an RS485 communication circuit (514), a radio frequency drive signal generating circuit (515), a TEC closed-loop cooling circuit (516), a reference optical path A / D conversion circuit (517) and a receiving optical path A / D conversion circuit (518); when the spectrum detector is working, the computer (511) in the main control module (51) sends a spectrum acquisition instruction to the USB communication circuit (512), and controls the spectrum acquisition system to work through the FPGA main control circuit (513); the FPGA main control circuit (513) sends a motor drive instruction via the RS485 communication circuit (514) to control the rotating motor drive module (41) to drive the rotating cup control module (4) to work, The FPGA main control circuit (513) controls the radio frequency drive signal generating circuit (515) to generate a radio frequency signal of a required frequency and modulates the signal for output, which is amplified by the radio frequency power amplifier (52) and applied to the acousto-optic tunable filter (13); the FPGA main control circuit (513) controls the TEC closed-loop cooling circuit (516) to perform closed-loop cooling control on the infrared detector; the analog signal processing circuit (53) performs phase-locked amplification processing on the weak modulated spectrum signal received by the reference detector preamplifier circuit (54) and the receiving detector preamplifier circuit (55); the FPGA main control circuit (513) controls the reference optical path A / D conversion circuit (517) and the receiving optical path A / D conversion circuit (518) to perform A / D conversion on the spectrum signal output by the analog signal processing circuit (53); the FPGA main control circuit (513) packages the spectrum data and sends it to the computer via the USB communication circuit (512); the optical signal received by the detector is amplified by a phase-locked amplification method, and the gain of the system can be adjusted programmably, thereby improving the signal-to-noise ratio and flexibility of spectrum acquisition while ensuring the sampling speed.

16. A method for implementing a rotating cup detection diffuse reflectance spectrometer based on AOTF 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 (5), connecting the computer (511) and the USB communication circuit (512), 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 (516) to perform closed-loop cooling control on the reference detector (24) and the receiving detector (32) 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 in a sample cup (27); 2-3) Sending a rotation instruction to enable the rotating cup to rotate the control motor (42), the motor drives the rotating cup to rotate the driving gear (43), thereby rotating the rotating cup and the driven gear (44), so as to obtain uniform spectrum data of the sample to be tested, and then proceeding to step 2) to collect spectrum data and obtain spectrum data of the sample to be tested; 3) Spectral data collection 3-1) The FPGA main control circuit (513) controls the operation of the radio frequency drive signal generating circuit (515), 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 (32); 3-2) The weak light signals detected by the reference detector (24) and the receiving detector (32) are synchronously entered into the analog signal processing circuit (53) after being amplified in the pre-stage, and the FPGA main control circuit (513) synchronously controls the reference light path A / D conversion circuit (517) and the receiving light path A / D conversion circuit (518) to sample and save the signal output by the analog signal processing circuit (53), 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 (512); 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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