An integrated optical fiber spectrometer based on AOTF and its implementation method

Abstract

The present invention discloses a transceiver-integrated optical fiber spectrometer based on AOTF and an implementation method thereof. The spectrometer is based on the electrically controlled splitting characteristics of an acousto-optic tunable filter, and utilizes a built-in active light source to converge into a transmitting optical fiber after splitting, and a receiving optical fiber is connected to a receiving device. The transceiver optical fiber can realize absorption spectrum detection of solids or liquids by connecting different accessories, and adopts dual-detector beam splitting reference calibration to realize real-time spectrum calibration and light source performance monitoring. By adding a 0-level light shield, a beam splitter, and a concave reflector, the ±1-level diffracted light is all transmitted into the same optical fiber to irradiate the sample surface, thereby enhancing the energy of the signal light, and combining with a phase-locked circuit to further improve the spectrum detection signal-to-noise ratio. The invention has a compact structure, a fast detection speed, and a high signal-to-noise ratio. It can measure solid and liquid substances by connecting different optical fiber accessories, and can realize detection far away from the instrument by combining the use of long optical fibers, and has a wide range of applications.

Description

Technical Field

[0001] The present invention relates to spectrum detection technology, and in particular to an AOTF-based optical fiber spectrometer with integrated transceiver and an implementation method thereof, which is applicable to the field of material spectrum detection and analysis. Background Art

[0002] As the representative of "green detection technology", spectrum analysis technology has the advantages of high efficiency, rapidity, low cost, non-destructiveness and green environmental protection. As a spectroscopic system, AOTF (acousto-optic turnable filter) is known as "the most outstanding progress in the 1990s" in near-infrared spectrometers. Based on the characteristics of AOTF: light and small size, dual light path design; high precision, effective elimination of background interference, strong anti-interference ability; good reproducibility, real-time and rapid detection; scanning controlled by electronic signals, high resolution; fast wavelength switching speed and good stability within the full spectrum scanning range; large signal energy; no moving parts. Therefore, AOTF-type spectrometers are flexible, lightweight, and easy to analyze online, and have been increasingly widely used in agriculture, food testing, soil analysis, water quality testing and other fields.

[0003] There are methods for spectrum detection based on AOTF spectral characteristics in public documents and patents. For example, application publication number CN109115682A discloses a spectrometer and detection method for detecting both liquid and solid components. The patent uses an active polychromatic light source to converge and irradiate the sample surface, receives diffuse reflected light from the sample surface and enters 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 realize spectrum detection, which wastes the -1-order diffracted light energy. In addition, the instrument irradiates a very small area on the sample surface. The method detects samples before AOTF spectroscopy, which easily leads to inaccurate detection results. In addition, this method detects samples before AOTF spectroscopy, which easily introduces stray light, and liquid measurement can only be sampled with a cuvette. 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 spectroscopy 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 0-level 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 inability to fully utilize the ±1 level signal light separated by the AOTF, which reduces the signal-to-noise ratio of the instrument, and the inflexible application scenarios of the instrument, which can only detect in specific places. The present invention fully utilizes the ±1 level signal light, and uses an external optical fiber interface to integrate the irradiation and reception of the signal light source. While improving the signal-to-noise ratio of the instrument, it can detect different samples such as solids and liquids by connecting different detection accessories. By using long optical fibers, it can realize detection far away from the instrument, expanding the application range of the instrument.

[0005] The purpose of the present invention is to provide an integrated optical fiber 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, and uses a light source splitting module to generate monochromatic light, which is transmitted through optical fibers to irradiate the sample. The diffuse scattered light of the sample or the transmitted light of the object to be tested enters the detector through the receiving optical fiber, thereby detecting the spectral characteristics of the sample signal light. At the same time, before irradiating the sample, 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. By adding spatial shielding of 0-order light, two splitters and a concave reflector, ±1-order diffracted light is fully received, which effectively increases the energy of the signal light, and the phase-locked circuit is insensitive to 0-order light to improve the signal-to-noise ratio of spectral detection. At the same time, different detection accessories are connected to realize detection of different samples such as solids and liquids. By using long optical fibers, detection far away from the instrument can be realized. The application range is wide, the structure is compact, the detection speed is fast, and the accuracy is high.

[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, 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 concave reflector 25, a +1-level concave reflector 26 and a transmitting optical fiber interface 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 calibration 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 converged into the transmitting optical fiber interface 27 through the -1-level concave reflector 25 and the +1-level concave reflector 26.

[0012] The -1 level flat beam splitter 21 and the +1 level flat beam splitter 22 are flat window plates, and the surfaces are coated with a transflective film having a wavelength band applicable to 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 concave reflecting mirror 25 and the +1st level concave reflecting mirror 26 are coated with a reflective film of a wavelength band applicable to the spectrometer.

[0016] The transmitting optical fiber interface 27 is a SMA optical fiber interface.

[0017] The external detection accessory 3 is composed of a solid diffuse reflection fiber optic measurement accessory 31 and a liquid transmission fiber optic measurement accessory 32; when testing, the solid diffuse reflection fiber optic measurement accessory 31 or the liquid transmission fiber optic measurement accessory 32 is connected to the transmitting fiber optic interface 27 to irradiate the signal light onto the solid or liquid sample.

[0018] The spectral receiving module 4 is composed of an incident optical fiber interface 41, a receiving lens group 42 and a receiving detector 43; the optical fiber at the other end of the external accessory 3 is connected to the incident optical fiber interface 41, and the signal light reflected or transmitted by the sample to be tested enters the incident optical fiber interface 41 through the optical fiber, is collected by the receiving lens group 42 and enters the receiving detector 43, thereby realizing the characteristic spectrum detection of the material.

[0019] The incident optical fiber interface 41 adopts the same interface as the transmitting optical fiber interface (27).

[0020] The receiving lens group 42 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.

[0021] The receiving detector 43 adopts the same unit detector as the reference detector (24).

[0022] 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, a radio frequency drive signal generating circuit 514, a TEC closed-loop cooling circuit 515, a reference optical path A / D conversion circuit 516 and a receiving optical path A / D conversion circuit 517; 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 controls the radio frequency drive signal generating circuit 514 to generate a radio frequency signal of the required frequency and modulate the output, and the radio frequency power amplifier 53 amplification, and applied to the acousto-optic tunable filter 13; the FPGA main control circuit 513 controls the TEC closed-loop cooling circuit 515 to perform closed-loop cooling control on the infrared detector; the analog signal processing circuit 54 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 516 and the receiving optical path A / D conversion circuit 517 to perform A / D conversion on the spectral signal output by the analog signal processing circuit 54, and the FPGA main control circuit 513 packages the spectral data and sends it to the computer 511 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.

[0023] A line of sight method for an integrated optical fiber spectrometer based on AOTF, characterized in that the method steps are as follows:

[0024] 1) Equipment power-on self-test

[0025] 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;

[0026] 2) Preheat the equipment and prepare before work

[0027] 2-1) Turn on the TEC closed-loop cooling circuit 515 to perform closed-loop cooling control on the reference detector 24 and the receiving detector 43 until the detector cooling is stable;

[0028] 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. The sample to be tested is placed on the optical fiber attachment connecting the transmitting optical fiber interface 27 and the incident optical fiber interface 41 .

[0029] 3) Spectral data collection

[0030] 3-1) The FPGA main control circuit 513 controls the operation of the RF drive signal generating circuit 514, 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 43;

[0031] 3-2) The weak light signals detected by the reference detector 24 and the receiving detector 43 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 516 and the receiving optical path A / D conversion circuit 517 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 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, which can calibrate the detection and monitor the stability of the light source in real time; 2. Two plane reflectors are used to irradiate the ±1st order diffraction light to the same position of the transmitting optical fiber interface, making full use of the ±1st order diffraction light, enhancing the detection signal intensity, and improving the signal-to-noise ratio; 3. By connecting different detection accessories, different samples such as solids and liquids can be detected. By using long optical fibers, detection far away from the instrument can be achieved, expanding the application range of the instrument. The spectral detection method based on this model can be used in other optical detection fields, which 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 It is a schematic diagram of the working principle of the data acquisition and control module 5. DETAILED DESCRIPTION

[0038] An integrated optical fiber spectrometer based on AOTF includes a light source splitting module 1, a ±1 level signal light reference and emission module 2, an external detection accessory 3, a spectrum receiving module 4 and a data acquisition and control module 5. Figure 1 The structure features and implementation methods of the present invention are shown.

[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 concave reflector 25, +1 level concave reflector 26 and receiving lens group 42: 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 concave reflector 25, +1 level concave reflector 26 and receiving lens group 42 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 of 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) Reference detector 24 and receiving detector 43: 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 an integrated optical fiber 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, by shielding the 0th order light generated after AOTF splitting, the ±1st order diffraction 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. Two concave reflectors are used to irradiate the ±1st order diffraction light to the same position of the transmitting optical fiber interface, which makes full use of the ±1st order diffraction light, enhances the detection signal intensity, improves the signal-to-noise ratio, and can measure solid and liquid substances by connecting different optical fiber accessories. In combination with the use of long optical fiber, detection far away from the instrument can be achieved, and the application range is wide.

Claims

1. An AOTF-based transceiver integrated optical fiber spectrometer, comprising a light source spectrometer module (1), a ±1 level signal light reference and output module (2), an external detection accessory (3), a spectrum receiving module (4) and a data acquisition and control module (5); 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. Then, a portion of the level ±1 signal light enters the level ±1 signal light reference and output module (2) for reference calibration, and a portion enters the external detection accessory (3) to irradiate the sample. The signal light generated by diffuse reflection of the sample enters the spectrum receiving module (4) for sample spectrum collection and 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 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 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, 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 emission module (2) is composed of a -1-level flat beam splitter (21), a +1-level flat beam splitter (22), a secondary convergence lens (23), a reference detector (24), a -1-level concave reflector (25), a +1-level concave reflector (26) and a transmitting optical fiber interface (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 beam splitter (21) and the +1-level flat beam splitter (22) to complete reference calibration detection, and the ±1-level diffracted light transmitted through the -1-level flat beam splitter (21) and the +1-level flat beam splitter (22) is respectively converged into the transmitting optical fiber interface (27) through the -1-level concave reflector (25) and the +1-level concave reflector (26).

2. The AOTF-based fiber optic spectrometer 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 fiber optic 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 AOTF-based fiber optic spectrometer 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 integrated optical fiber 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 fiber optic spectrometer 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 applicable to the spectrometer and a ratio of 90:

10.

7. The AOTF-based fiber optic 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 fiber optic spectrometer according to claim 1, characterized in that: The reference detector (24) is a unit detector corresponding to the applicable waveband of the spectrometer.

9. The AOTF-based fiber optic spectrometer according to claim 1, characterized in that: The surfaces of the -1st-level concave reflecting mirror (25) and the +1st-level concave reflecting mirror (26) are coated with a reflective film of a wavelength band applicable to the spectrometer.

10. The AOTF-based fiber optic spectrometer with integrated transmitter and receiver according to claim 1, characterized in that: The transmitting optical fiber interface (27) is an SMA optical fiber interface.

11. The AOTF-based fiber optic spectrometer according to claim 1, characterized in that: The external detection accessory (3) is composed of a solid diffuse reflection optical fiber measurement accessory (31) and a liquid transmission optical fiber measurement accessory (32); when testing, one end of the solid diffuse reflection optical fiber measurement accessory (31) or the liquid transmission optical fiber measurement accessory (32) is connected to the transmitting optical fiber interface (27) so that the signal light can be irradiated onto the solid or liquid sample.

12. The AOTF-based fiber optic spectrometer according to claim 1, characterized in that: The spectrum receiving module (4) is composed of an incident optical fiber interface (41), a receiving lens group (42) and a receiving detector (43); the signal light reflected or transmitted by the sample to be tested enters the incident optical fiber interface (41) through the optical fiber, is collected by the receiving lens group (42) and enters the receiving detector (43), thereby realizing the material characteristic spectrum detection.

13. The AOTF-based integrated optical fiber spectrometer according to claim 12, characterized in that: The incident optical fiber interface (41) adopts the same interface as the transmitting optical fiber interface (27).

14. The AOTF-based fiber optic spectrometer according to claim 12, characterized in that: The receiving lens group (42) 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.

15. The AOTF-based integrated optical fiber spectrometer according to claim 12, characterized in that: The receiving detector (43) adopts the same unit detector as the reference detector (24).

16. The AOTF-based fiber optic spectrometer with integrated transmitter and receiver according to claim 1, 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), a radio frequency drive signal generating circuit (514), a TEC closed-loop cooling circuit (515), a reference optical path A / D conversion circuit (516) and a receiving optical path A / D conversion circuit (517); 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) controls the radio frequency drive signal generating circuit (514) to generate a radio frequency signal of a required frequency and modulate the output, and the radio frequency power is used to generate the radio frequency signal. The FPGA main control circuit (513) controls the TEC closed-loop cooling circuit (515) to perform closed-loop cooling control on the infrared detector; the analog signal processing circuit (54) 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 (516) and the receiving optical path A / D conversion circuit (517) to perform A / D conversion on the spectral signal output by the analog signal processing circuit (54); the FPGA main control circuit (513) packages the spectral data and sends it to the computer (511) through 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 spectral acquisition while ensuring the sampling speed.

17. A method for implementing the AOTF-based integrated optical fiber spectrometer as claimed in claim 12, characterized in that The steps are as follows: 1) Equipment power-on self-test Connect a power source to power 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; 2) Preheat the equipment and prepare before work 2-1) turning on the TEC closed-loop cooling circuit (515) to perform closed-loop cooling control on the reference detector (24) and the receiving detector (43) 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. The sample to be tested is placed on the optical fiber attachment connecting the transmitting optical fiber interface (27) and the incident optical fiber interface (41); 3) Spectral data collection 3-1) The FPGA main control circuit (513) controls the operation of the radio frequency drive signal generating circuit (514), 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 (43); 3-2) The weak light signals detected by the reference detector (24) and the receiving detector (43) 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 (516) and the receiving light path A / D conversion circuit (517) 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) 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; 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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