Laser doppler velocimetry system and method based on detector temperature control

Abstract

The application relates to a laser Doppler velocimetry system and method based on detector temperature control. The system comprises an optical path detection component for acquiring an electric signal, and a signal processing component for processing the electric signal. A temperature control assembly is arranged in the optical path detection component, the temperature control assembly is used for temperature control of the optical path detection component, so that the signal-to-noise ratio of the output signal of the optical path detection component is adjusted; the signal processing component is electrically connected with the optical path detection component, the signal quality of the electric signal is judged according to the signal-to-noise ratio at the corresponding temperature, then the temperature control assembly is controlled according to the electric signal not meeting the requirements, and the electric signal meeting the requirements is calculated, so that the velocity of a to-be-measured motion surface is obtained. The application can improve the signal-to-noise ratio of the Doppler signal, and improves the detection capability of the weak signal.

Description

Technical Field

[0001] This application relates to the fields of laser and precision measurement technology, and in particular to a laser Doppler velocimetry system and method based on detector temperature control. Background Technology

[0002] Laser Doppler Velocimeters (LDVs) offer numerous advantages, including high accuracy, non-contact measurement, and high spatial resolution, making them widely used in fluid velocity measurement, solid surface vibration measurement, and displacement measurement. Furthermore, compared to traditional velocity measurement methods such as odometers, accelerometers, and Global Navigation Satellite Systems (GNSS), LDVs possess complete autonomy, enabling all-weather and highly reliable operation. This provides an independent velocity measurement method for vehicle navigation and positioning, and thus they are increasingly being used in conjunction with inertial navigation systems and GNSS to form integrated navigation systems. In recent years, the application of LDVs in high-speed trains, underwater vehicles, and aircraft has attracted widespread attention from researchers.

[0003] Laser Doppler velocimeters acquire Doppler signals by receiving scattered light from moving surfaces, resulting in extremely weak signals received by the detector. Furthermore, increasing the measurement distance and changes in the transmission medium further attenuate the signal strength. The quality of the Doppler signal directly determines the accuracy of the velocimeter's speed acquisition and its operating distance. Summary of the Invention

[0004] Therefore, it is necessary to provide a detector-temperature-controlled laser Doppler velocimetry system and method that can improve the signal-to-noise ratio of Doppler signals and is beneficial for measuring weak signals, in order to address the above-mentioned technical problems.

[0005] A laser Doppler velocimetry system based on detector temperature control includes an optical path detection component for acquiring electrical signals and a signal processing component for processing the electrical signals. The optical path detection component is provided with a temperature control component, which controls the temperature of the optical path detection component to adjust the signal-to-noise ratio of the optical path detection component.

[0006] The signal processing component is electrically connected to the optical path detection component. It judges the signal quality of the electrical signal by the signal-to-noise ratio at the corresponding temperature, then controls the temperature control component based on the electrical signal that does not meet the requirements, and calculates the electrical signal that meets the requirements to obtain the speed of the moving surface to be measured.

[0007] In one embodiment, the optical path detection component includes:

[0008] A laser, used to emit a laser beam;

[0009] A beam splitter, located in the path of the laser beam, is used to split the laser beam into a reference beam and a measurement beam. The measurement beam forms scattered light after diffuse reflection from the surface to be moved.

[0010] A photodetector, located on the path of the reference beam and the scattered light, is used to collect the reference beam and the scattered light and convert them into electrical signals;

[0011] A temperature control component is disposed on the photodetector and is used to control the temperature of the photodetector in order to adjust the signal-to-noise ratio of the output signal of the photodetector.

[0012] In one embodiment, the temperature control component includes a heat-conducting sheet and a thermoelectric cooler, the cold end of the thermoelectric cooler is attached to the heat-conducting sheet, and the photodetector is embedded in the heat-conducting sheet.

[0013] In one embodiment, a receiving portion is provided at one end of the heat-conducting sheet away from the semiconductor cooling sheet, and a through hole is formed in the receiving portion, and the photodetector is embedded in the through hole of the receiving portion.

[0014] In one embodiment, both the heat-conducting sheet and the semiconductor cooling sheet have through holes. When the cold end of the semiconductor cooling sheet is in contact with the heat-conducting sheet, the two through holes are aligned, and the photodetector is embedded in the through hole of the heat-conducting sheet.

[0015] In one embodiment, the signal processing component includes:

[0016] The signal conditioning unit is electrically connected to the photodetector and is used to process the electrical signal output by the photodetector to obtain a Doppler signal.

[0017] The signal quality judgment unit, electrically connected to the signal conditioning unit, is used to judge the signal quality of the Doppler signal; when the signal quality does not meet the requirements, it sends a temperature control command to the PID control unit; when the signal quality meets the requirements, it sends the Doppler signal to the calculation unit.

[0018] The PID control unit controls the temperature control component according to the received temperature control command to adjust the temperature;

[0019] The calculation unit calculates the velocity of the moving surface under test based on the Doppler signal of the conformal quality.

[0020] In one embodiment, the signal conditioning unit includes:

[0021] A preamplifier, electrically connected to the photodetector, is used to amplify the amplitude of the electrical signal;

[0022] A filter, electrically connected to the preamplifier, is used to filter the amplified electrical signal.

[0023] The AD acquisition unit is electrically connected to the filter and is used to convert the filtered electrical signal into a digital signal.

[0024] The Fourier transform unit is electrically connected to the AD acquisition unit and is used to process the digital signal to obtain the Doppler signal.

[0025] A laser Doppler velocimetry method based on detector temperature control, the method comprising:

[0026] The temperature of the photodetector is adjusted by a temperature control component to obtain the electrical signal output by the photodetector at the current temperature; then the electrical signal is processed by a signal conditioning unit to obtain a Doppler signal.

[0027] The signal-to-noise ratio is calculated based on the Doppler signal.

[0028] The signal quality of the current Doppler signal is determined based on the signal-to-noise ratio. When the signal quality does not meet the requirements, the temperature is readjusted by the temperature control component until the signal quality requirements are met.

[0029] The velocity of the moving surface under test is obtained by solving the Doppler signal that meets the signal quality requirements.

[0030] In one embodiment, determining the signal quality of the current Doppler signal based on the signal-to-noise ratio includes:

[0031] A threshold is set, and it is determined whether the signal-to-noise ratio meets the threshold requirement. If not, the temperature control component is controlled by a PID control algorithm to adjust the temperature. If yes, the velocity of the moving surface to be measured is obtained by solving the Doppler signal.

[0032] Compared with existing technologies, the laser Doppler velocimetry system and method based on detector temperature control provided by this invention have the following beneficial technical effects:

[0033] 1. This invention uses a temperature control component to control the temperature of the optical path detection component, thereby changing the amplification factor of the optical path detection component, thus improving the signal-to-noise ratio of the Doppler signal and enhancing the optical path detection component's ability to detect weak signals.

[0034] 2. This invention, through its signal processing component, can automatically control and adjust the temperature of the optical path detection component to improve the signal-to-noise ratio of the Doppler signal, thereby ensuring the accuracy of the laser Doppler velocimetry system calculations. Attached Figure Description

[0035] Figure 1This is a schematic diagram of a laser Doppler velocimetry system based on detector temperature control in one embodiment;

[0036] Figure 2 This is a schematic diagram of the temperature control component in one embodiment; wherein Figure 2 (a) is a schematic diagram of the first type of temperature control component. Figure 2 (b) is a schematic diagram of the second type of temperature control component;

[0037] Figure 3 This is a schematic flowchart of a laser Doppler velocimetry method based on detector temperature control in one embodiment.

[0038] Explanation of reference numerals in the attached figures: Laser 1, Collimating lens group 2, Beam splitter 3, Attenuator 4, Reflector 5, First pinhole aperture 61, Second pinhole aperture 62, Filter 7, Photodetector 8, Semiconductor cooling chip 81, Heat-conducting sheet 82, Receiving part 821, Signal processing unit 9, Preamplifier 91, Filter 92, AD acquisition unit 93, Fourier transform unit 94, Signal quality judgment unit 95, PID control unit 96, Solving unit 97, Surface to be measured 10. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0040] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0041] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly and specifically defined.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0044] Example 1

[0045] See Figure 1 and Figure 2 The structure of the laser Doppler velocimetry system based on detector temperature control provided in this embodiment includes an optical path detection component for acquiring electrical signals and a signal processing component for processing the electrical signals. The optical path detection component is equipped with a temperature control component to control the temperature of the optical path detection component and adjust the signal-to-noise ratio of the output signal of the optical path detection component. The signal processing component is electrically connected to the optical path detection component and judges the signal quality of the electrical signal by the signal-to-noise ratio at the corresponding temperature. Then, it controls the temperature control component based on the electrical signal that does not meet the requirements and calculates the electrical signal that meets the requirements to obtain the velocity of the moving surface to be measured.

[0046] Specifically, the optical path detection component includes a laser 1, a collimating lens group 2, a beam splitter 3, an attenuator 4, a reflector 5, a first pinhole aperture 61, a second pinhole aperture 62, a filter 7, and a photodetector 8. The photodetector 8 is equipped with a temperature control component.

[0047] More specifically, the laser 1, collimating lens group 2, beam splitter 3, and first pinhole aperture 61 are sequentially spaced along a first straight line, with the emission direction of the laser 1 forming a certain angle with the beam splitter 3 along the first straight line. The angle between the emission direction of the laser 1 and the moving surface 10 to be measured is θ, and θ≠90°. The reflecting mirror 5, attenuator 4, beam splitter 3, filter 7, second pinhole aperture 62, and photodetector 8 are sequentially spaced along a second straight line, with the reflecting mirror 5 forming a certain angle with the beam splitter 3. The first and second straight lines intersect perpendicularly on the beam splitter 3. The basic structure of the velocimeter is a Michelson interferometer, and the laser 1 is a single-longitudinal-mode solid-state laser. The collimating lens group 5 can be composed of a convex lens and a concave lens, or multiple lenses. It is worth noting that the angles between the first straight line and the beam splitter 3, and between the reflecting mirror 5 and the beam splitter 3, are between 0° and 90°, preferably 30°, 45°, or 60°. The first and second straight lines are not limited to being perpendicular; as long as the split beam can be collected by the photodetector 8, it is acceptable.

[0048] The temperature control component includes a thermoelectric cooler 81 and a heat-conducting plate 82. The cold end of the thermoelectric cooler 81 is in contact with the heat-conducting plate 82, and a photodetector 8 is embedded in the heat-conducting plate. The thermoelectric cooler 81 and the heat-conducting plate 82 have two structures: The first structure has a receiving portion 821 at the end of the heat-conducting plate 82 away from the thermoelectric cooler 81, with a through-hole in the receiving portion 821, into which the photodetector 8 is embedded. The position of the through-hole in the receiving portion 821 can be determined according to actual conditions, generally located at the center of the receiving portion 821. The second structure has through-holes in both the heat-conducting plate 82 and the thermoelectric cooler 81. When the cold end of the thermoelectric cooler 81 is in contact with the heat-conducting plate 82, the two through-holes are aligned, and the photodetector 8 is embedded in the through-hole of the heat-conducting plate. The position of the through hole of the semiconductor refrigeration chip 81 is set according to the position of the through hole of the heat conduction chip 82. When the through hole of the heat conduction chip 82 is opened in the center position, the through hole of the semiconductor refrigeration chip 81 is also opened in the center position.

[0049] When the first temperature control component structure is adopted, the end of the photodetector 8 with the detection surface in the housing 821 is oriented towards the beam splitter 3, and the split beam is directly collected by the photodetector 8.

[0050] When the second temperature control component structure is adopted, one side of the semiconductor cooling chip 81 in the temperature control component is placed facing the beam splitter 3, and the detection surface of the photodetector 8 faces the through hole of the semiconductor cooling chip 81. The split beam passes through the through hole of the semiconductor cooling chip 81 and is collected by the detection surface of the photodetector 8.

[0051] The temperature of the photodetector 8 is controlled by the aforementioned temperature control component, thereby adjusting the signal-to-noise ratio of the output signal of the photodetector 8.

[0052] When the optical path detection component is working, the laser 1 emits a laser beam along the direction of the first straight line. After the collimation of the laser beam is improved by the collimating lens group 2, it illuminates the beam splitter 3. The beam splitter 3 divides the laser beam into a reference beam and a measurement beam. The beam that passes through the beam splitter 3 and illuminates the moving surface 10 to be measured along the direction of the first straight line is the measurement beam. The beam that is reflected by the beam splitter 3 and illuminates the reflecting mirror 5 along the direction of the second straight line is the reference beam.

[0053] After being reflected again by the reflector 5, the reference beam passes sequentially through the attenuator 4, beam splitter 3, filter 7 and second pinhole aperture 62 in the opposite direction of the second straight line and then illuminates the detection surface of the photodetector 8, where it is collected by the photodetector 8.

[0054] After the measuring beam passes through the beam splitter 3, it passes through the first pinhole aperture 61 and illuminates the moving surface 10 to be measured at an angle θ. The diffuse reflection of the moving surface 10 will generate scattered light in various directions. The scattered light along the first straight line is reflected by the beam splitter 3 to the opposite direction of the second straight line. After the filter 7 removes impurities, it passes through the second pinhole aperture 62 and illuminates the detection surface of the photodetector 8, where it is collected by the photodetector 8. The two beams generate beat frequency signals on the surface of the photodetector 8. The photodetector 8 converts the beat frequency signals into electrical signals and sends them to the signal processing unit 9 for processing.

[0055] The signal processing unit 9 includes a signal conditioning unit, a signal quality judgment unit 95, a PID control unit 96, and a calculation unit 97; the signal conditioning unit further includes a preamplifier 91, a filter 92, an AD acquisition unit 93, and a Fourier transform unit 94.

[0056] The signal conditioning unit is electrically connected to the photodetector 8 and processes the electrical signal output by the photodetector 8 to obtain the Doppler signal. Specifically, the preamplifier 91 is electrically connected to the photodetector 8 and amplifies the electrical signal. The filter 92 is electrically connected to the preamplifier 91 and filters the amplified electrical signal. The AD acquisition unit 93 is electrically connected to the filter 92 and converts the filtered electrical signal into a digital signal. The Fourier transform unit 94 is electrically connected to the AD acquisition unit 93 and processes the digital signal to obtain the Doppler signal.

[0057] The signal quality judgment unit 95 is electrically connected to the Fourier transform unit 94 and is used to judge the signal quality of the Doppler signal. When the signal quality does not meet the requirements, a temperature control command is sent to the PID control unit 96. When the signal quality meets the requirements, the Doppler signal is sent to the calculation unit 97.

[0058] The PID control unit 96 controls the temperature control component according to the received temperature control command to adjust the temperature.

[0059] The calculation unit 97 identifies the Doppler frequency based on the Doppler signal of the conforming quality, and then calculates the velocity of the moving surface to be measured based on the Doppler frequency.

[0060] Example 2

[0061] See Figure 3 A laser Doppler velocimetry method based on detector temperature control is provided, comprising the following steps:

[0062] Step 202: The temperature of the photodetector is adjusted by the temperature control component to obtain the electrical signal output by the photodetector at the current temperature; then the electrical signal is processed by the signal conditioning unit to obtain the Doppler signal.

[0063] Step 204: Calculate the signal-to-noise ratio based on the Doppler signal.

[0064] Step 206: Determine the signal quality of the current Doppler signal based on the signal-to-noise ratio. If the signal quality does not meet the requirements, readjust the temperature through the temperature control component until the signal quality requirements are met.

[0065] Step 208: Solve the Doppler signal that meets the signal quality requirements to obtain the velocity of the moving surface to be measured.

[0066] The principle of controlling the signal-to-noise ratio of a photodetector by adjusting the temperature is explained below:

[0067] The relationship between the breakdown voltage and temperature of a photodetector is as follows:

[0068] V BR =0.45*T+b (1)

[0069] In the formula, T represents temperature, and b is a constant related to the detector. It can be seen from formula (1) that the breakdown voltage of the photodetector increases as the temperature increases.

[0070] The multiplication factor expression for a photodetector is:

[0071]

[0072] In the formula, V B Let n be the bias voltage of the detector, and n depends on the semiconductor material, doping concentration, and radiation wavelength. As can be seen from formula (2), when the reverse bias voltage of the detector is constant, the multiplication factor of the detector will increase as the temperature decreases.

[0073] The electrical signal output by the photodetector is represented as:

[0074]

[0075] In the formula, I s The Doppler electrical signal output by the detector; i D P represents the photocurrent of the Doppler signal received by the detector. D η is the power of the Doppler optical signal received by the detector; e is the quantum efficiency of the detector; λ is the charge constant; h is Planck's constant; and c is the speed of light in vacuum. From formula (3), it can be seen that the electrical signal output by the detector will increase with the increase of the multiplication factor.

[0076] It's understandable that changing the temperature will alter the detector's output noise. The detectors in laser Doppler velocimetry systems primarily output thermal noise and shot noise.

[0077] Thermal noise can be expressed as:

[0078]

[0079] Where K is Boltzmann's constant; B is the noise bandwidth; and R is the equivalent load resistance. It can be seen that thermal noise is not amplified by the photodetector and is only related to temperature.

[0080] Shot noise in photodetectors is caused by the DC current flowing through the pn junction, and mainly includes shot noise caused by signal photocurrent, background photocurrent, and dark current, expressed as:

[0081]

[0082] Where P b υ is the background optical power; i is the optical frequency; dg For dark current; F m This is an excess noise factor.

[0083] Dark current and excess noise factor can be expressed as follows:

[0084]

[0085] F m =M χ (7)

[0086] Where γ is a scaling factor determined by the photocathode material; A is the area of ​​the photocathode; χ is the work function; χ is the excess noise index.

[0087] Therefore, the signal-to-noise ratio of the output signal of the laser Doppler velocimetry system can be expressed as:

[0088]

[0089] The above analysis shows that reducing the temperature of the photodetector can improve the signal-to-noise ratio of the Doppler signal, thereby enhancing the laser Doppler velocimetry system's ability to measure weak signals and improving the system's speed measurement accuracy and distance.

[0090] Then, a threshold is set, and it is determined whether the signal-to-noise ratio meets the threshold requirement. If not, a temperature control command is sent to the PID control unit, and the temperature control component is controlled by the PID control algorithm to readjust the temperature. If yes, the velocity of the moving surface to be measured is obtained by solving the Doppler signal.

[0091] Finally, by identifying the Doppler frequency based on the Doppler signal that meets the signal quality requirements, the Doppler frequency f of the beat frequency signal can be obtained. D The Doppler frequency of the beat frequency signal is proportional to the velocity of the moving surface; that is, the Doppler frequency is expressed as:

[0092]

[0093] Therefore, the velocity of the moving surface can be expressed as:

[0094]

[0095] In the formula It is called the scaling factor, where V is the running speed of the carrier, λ is the wavelength of the incident light, and θ is the angle between the direction of the incident light and the direction of the velocity.

[0096] It is understood that this invention performs temperature control on the photodetector of a laser Doppler velocimeter. The Doppler signal quality is determined in the signal processing unit. When the Doppler signal quality meets the requirements, velocity calculation is performed directly. When the Doppler signal quality does not meet the requirements, a PID control algorithm is used to control the photodetector, reducing the temperature of the heat-conducting sheet to lower the photodetector's breakdown voltage, thereby increasing the photodetector's multiplication factor, improving the signal-to-noise ratio, and ultimately enhancing the photodetector's sensitivity. This allows the photodetector to detect weak laser signals, ultimately enabling the laser Doppler velocimeter system to detect the velocity of the moving surface being measured.

[0097] By improving the signal-to-noise ratio of the Doppler signal to meet the threshold requirements, and then performing velocity calculation, the accuracy of the velocity calculation of the velocimeter is guaranteed. This provides a highly reliable, simple, and low-cost laser Doppler velocimetry system and method.

[0098] It should be understood that, although Figure 3The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 3 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A laser Doppler velocimetry system based on detector temperature control, comprising an optical path detection component for acquiring electrical signals, and a signal processing component for processing the electrical signals, characterized in that: The optical path detection component is equipped with a temperature control component, which controls the temperature of the optical path detection component to adjust the signal-to-noise ratio of the optical path detection component. The signal processing component is electrically connected to the optical path detection component. It judges the signal quality of the electrical signal by the signal-to-noise ratio at the corresponding temperature, then controls the temperature control component based on the electrical signal that does not meet the requirements, and calculates the electrical signal that meets the requirements to obtain the velocity of the moving surface to be measured. The temperature control component includes a heat-conducting sheet and a semiconductor cooling sheet, wherein the cold end of the semiconductor cooling sheet is attached to the heat-conducting sheet, and a photodetector is embedded in the heat-conducting sheet; The signal processing component includes: The signal conditioning unit is electrically connected to the photodetector and is used to process the electrical signal output by the photodetector to obtain a Doppler signal. The signal quality judgment unit, electrically connected to the signal conditioning unit, is used to judge the signal quality of the Doppler signal; when the signal quality does not meet the requirements, it sends a temperature control command to the PID control unit; when the signal quality meets the requirements, it sends the Doppler signal to the calculation unit. The PID control unit controls the temperature control component according to the received temperature control command to adjust the temperature; The calculation unit calculates the velocity of the moving surface under test based on the Doppler signal of the conformal quality.

2. The laser Doppler velocimetry system based on detector temperature control according to claim 1, characterized in that, The optical path detection component includes: A laser, used to emit a laser beam; A beam splitter, located in the path of the laser beam, is used to split the laser beam into a reference beam and a measurement beam. The measurement beam forms scattered light after diffuse reflection on the moving surface to be measured. A photodetector, located on the path of the reference beam and the scattered light, is used to collect the reference beam and the scattered light and convert them into electrical signals; A temperature control component is disposed on the photodetector and is used to control the temperature of the photodetector in order to adjust the signal-to-noise ratio of the output signal of the photodetector.

3. The laser Doppler velocimetry system based on detector temperature control according to claim 1 or 2, characterized in that, The heat-conducting sheet has a receiving portion at one end away from the semiconductor cooling sheet, and the receiving portion has a through hole, into which the photodetector is embedded.

4. The laser Doppler velocimetry system based on detector temperature control according to claim 1 or 2, characterized in that, Both the heat-conducting sheet and the semiconductor cooling sheet have through holes. When the cold end of the semiconductor cooling sheet is in contact with the heat-conducting sheet, the two through holes are aligned, and the photodetector is embedded in the through hole of the heat-conducting sheet.

5. The laser Doppler velocimetry system based on detector temperature control according to claim 1 or 2, characterized in that, The signal conditioning unit includes: A preamplifier, electrically connected to the photodetector, is used to amplify the amplitude of the electrical signal; A filter, electrically connected to the preamplifier, is used to filter the amplified electrical signal. The AD acquisition unit is electrically connected to the filter and is used to convert the filtered electrical signal into a digital signal. The Fourier transform unit is electrically connected to the AD acquisition unit and is used to process the digital signal to obtain the Doppler signal.

6. A laser Doppler velocimetry method based on detector temperature control, employing the laser Doppler velocimetry system based on detector temperature control as described in any one of claims 1 to 5, characterized in that, The method includes: The temperature of the photodetector is adjusted by a temperature control component to obtain the electrical signal output by the photodetector at the current temperature; then the electrical signal is processed by a signal conditioning unit to obtain a Doppler signal. The signal-to-noise ratio is calculated based on the Doppler signal; The signal quality of the current Doppler signal is determined based on the signal-to-noise ratio. When the signal quality does not meet the requirements, the temperature is readjusted by the temperature control component until the signal quality requirements are met. The velocity of the moving surface under test is obtained by solving the Doppler signal that meets the signal quality requirements.

7. The laser Doppler velocimetry method based on detector temperature control according to claim 6, characterized in that, Determining the signal quality of the current Doppler signal based on the signal-to-noise ratio includes: A threshold is set, and it is determined whether the signal-to-noise ratio meets the threshold requirement. If not, the temperature control component is controlled by a PID control algorithm to adjust the temperature. If yes, the velocity of the moving surface to be measured is obtained by solving the Doppler signal.

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