High-precision laser altimeter with temperature compensation

Abstract

The utility model relates to a high-precision laser altimeter with temperature compensation. The high-precision laser altimeter mainly solves the problem that an existing laser altimeter is unstable in output or has no height data output at the low temperature of minus 40 DEG C to minus 25 DEG C and the high temperature of 50 DEG C to 70 DEG C. The device comprises a laser emitting unit, a laser receiving unit, a lens unit, a digital signal processing unit and an EMI power supply filtering unit. Laser emitted by the laser emitting unit is collimated and parallel through the lens unit and then is emitted to the ground, and a reflected optical signal is converged to the laser receiving unit through the lens unit and is converted into an electric signal to enter the digital signal processing unit for height measurement; the EMI power supply filtering unit supplies power to the laser emitting unit, the laser receiving unit and the digital signal processing unit. According to the utility model, the height measurement precision and stability at the environment temperature of-40 DEG C to 70 DEG C are improved, the requirements of the helicopter for high precision and wide temperature range of matched height measurement equipment when the helicopter flies at a low altitude or close to the ground and lands at a fixed point are met, and the device can be used for helicopters and various aircrafts.

Description

Technical Field

[0001] The utility model belongs to the technical field of electronic instruments, in particular to a high-precision laser altimeter which can be used for aviation flight control systems. Background Art

[0002] When a helicopter is flying at low altitude or close to the ground and landing at a fixed point, it needs to be equipped with altimeter equipment to provide accurate ground height information for the helicopter flight control management system. At present, the altimeter product equipped with helicopters is a radio altimeter, but its error is large and cannot meet the high-precision requirements of helicopter altitude measurement. Therefore, in order to meet the high-precision requirements of aircraft for low-altitude flight and close to the ground, laser altimeter technology is used. Compared with radio altimeters, laser altimeters have the advantages of long measurement distance, high measurement accuracy, small size and light weight. The research on laser altimeter technology has been relatively mature, various new products have emerged in an endless stream, product design has been continuously innovated and promoted, and has been widely used in various fields of social life. For example, the Swiss LEICA phase laser altimeter has a measurement range of 0.05m to 60m, a measurement accuracy of ±1.5mm, and a laser light source wavelength of 620nm to 690nm; the American FLUCE phase laser altimeter F416D has a measurement range of 0.05m to 60m, a measurement accuracy of ±1.5mm, and a laser light source wavelength of 635nm.

[0003] Zhang Kunfeng, Hong Guanglie and others from the Shanghai Institute of Technical Physics, Chinese Academy of Sciences, designed and built a dual-coherent optical path tunable FMCW laser altimeter system, which added a reference optical path with a fixed delay to the system. Although the frequency modulation bandwidth measured by this system is in the terahertz order, the high resolution is about 200μm, which is only 80μm different from the theoretical value.

[0004] Lu Lu and others from Harbin Institute of Technology used an external cavity laser as the light source and built a set of swept frequency interferometers to compensate for the dispersion of optical fibers. When measuring the height of a target at 3.9 meters, the height measurement accuracy can reach 0.74μm and the high resolution is 45.9μm.

[0005] However, the above-mentioned existing laser altimeter products are greatly affected by temperature. The reverse breakdown voltage of the APD photodiode commonly used in the laser receiving module changes with temperature, affecting the gain size, which ultimately leads to the laser altimeter product output being unstable or having no altitude data output in low temperature environments of -40℃ to -25℃ and high temperature environments of 50℃-70℃, seriously affecting the height measurement accuracy and stability, and failing to meet the helicopter's requirements for high precision and wide temperature range of the supporting height measurement equipment. Therefore, there is an urgent need for a high-precision laser altimeter that is not affected by ambient temperature. Utility Model Content

[0006] The purpose of the utility model is to provide a high-precision laser altimeter with temperature compensation in view of the deficiencies of the above-mentioned prior art, so as to solve the problem that the existing laser altimeter has unstable output or no altitude data output in low temperature environments of -40℃ to -25℃ and high temperature environments of 50℃-70℃, and to improve the laser altimeter's height measurement accuracy and stability in an ambient temperature of -40℃-70℃.

[0007] In order to achieve the above-mentioned purpose, the utility model provides a high-precision laser altimeter with temperature compensation;

[0008] 1. A high-precision laser altimeter with temperature compensation, comprising a laser emitting unit 1, a laser receiving unit 2, a lens unit 3, a digital signal processing unit 4 and an EMI power supply filter unit 5, characterized in that: the laser receiving unit 2 comprises a photoelectric conversion module 21 and a temperature compensation module 22;

[0009] The photoelectric conversion module 21 includes a photoelectric conversion circuit 211 and an amplifying and filtering circuit 212. The photoelectric conversion circuit 211 uses an APD photodiode as a photoelectric conversion chip to convert an optical signal into an electrical signal and transmit it to the amplifying and filtering circuit 212 for amplification and filtering.

[0010] The temperature compensation module 22 includes a temperature sensor 221, an operational amplifier 222 and a boost chip 223. The temperature sensor 221 collects the surrounding temperature parameters and converts them into analog voltages, which are output to the boost chip 223 through the operational amplifier 222 for boosting and then output to the photoelectric conversion circuit in the photoelectric conversion module 21 to provide a bias voltage for the APD photodiode. The output voltage of the boost chip changes with temperature, thereby realizing automatic compensation of the bias voltage of the APD photodiode with temperature.

[0011] Further, the laser emitting unit 1 includes a driving module 11 and a semiconductor laser 12;

[0012] The driving module 11 includes a DC bias circuit 111 and an adder circuit 112, wherein the DC bias circuit 111 provides a stable DC bias signal for the semiconductor laser 12, and the adder circuit 112 is used to superimpose the sinusoidal modulation signal generated by the DDS signal sinusoidal generator 42 with the DC bias signal;

[0013] The semiconductor laser 12 is connected to the driving unit 11, and is used to receive a DC bias signal sent by the driving unit and emit 905nm laser.

[0014] Furthermore, the lens unit 3 includes a transmitting lens 31 and a receiving lens 32. The transmitting lens 31 is located in front of the semiconductor laser 12 and is used to compress the laser divergence angle to achieve collimated and parallel emission of the laser; the receiving lens 32 is located in front of the photoelectric conversion module 21 and is used to receive the echo reflected from the ground and focus the echo to the photoelectric conversion module 21 to convert it into an electrical signal and amplify and filter it.

[0015] Further, the digital signal processing unit 4 includes: a SOC chip 41, a DDS sinusoidal signal generator 42, a comparator 43, a high-frequency AD conversion chip 44, a high-frequency AD conversion chip 45, a power distributor 46, a software module 47, and a power distributor 48;

[0016] The software module 47 is fixed in the SOC chip 41, and is used for clock counting and phase difference calculation, and resolves the counting result and phase difference into initial altitude information, and periodically sends it to the flight and control computer, which includes:

[0017] A self-test submodule 471, for performing power-on self-test, periodic self-test and maintenance self-test;

[0018] The height measurement submodule 472 is used to perform clock counting and phase difference calculation, that is, to calculate the phase difference between the received signal and the transmitted signal through multiplication operation, CIC filter and CORDIC phase angle algorithm, to solve the initial height information, and to filter the initial height through the filtering algorithm;

[0019] The height status word setting submodule 473 is used to set the self-test result to the fault / normal state of the laser altimeter;

[0020] RS422 command receiving submodule 474, for receiving instructions transmitted by the flight control and management computer, including maintenance self-check, query remaining altitude, and zeroing commands;

[0021] The data packaging and output submodule 475 is used to package the altitude information, status information and self-test results, and send them to the flight control and management computer through the RS422 interface.

[0022] Furthermore, the EMI power supply filter unit 5 is respectively connected to the laser emitting unit 1, the laser receiving unit 2 and the digital signal processing module 4, and is used to perform EMI electromagnetic compatibility processing on the onboard power supply and transform the power supply after preprocessing to provide a low-voltage DC power supply that meets the requirements for each power supply object.

[0023] Compared with the prior art, the utility model has the following advantages:

[0024] 1. In the utility model, since a photoelectric conversion module 21 and a temperature compensation module 22 are provided in the laser receiving unit 2, when the ambient temperature rises or falls, the temperature compensation module 22 can realize automatic compensation of the bias voltage of the APD photodiode that changes with the temperature, so that the gain K of the APD photodiode is stable and unchanged, thereby solving the problem that the output of the existing laser altimeter is unstable or there is no altitude data output in the low temperature environment of -40℃ to -25℃ and the high temperature environment of 50℃-70℃, improving the laser altimeter's height measurement accuracy and stability in the ambient temperature of -40℃-70℃, and being suitable for flight altitude measurement in cold areas.

[0025] 2. The utility model has small size, low power consumption, light weight, high measurement range of 0.1m-240m, high measurement accuracy of 0.075m, and the chip used meets 100% localization.

[0026] 3. Compared with the traditional laser altimeter and ranging equipment which adopts a single pulse / phase measurement method, the laser altimeter provided by the utility model adopts a pulse-phase method for altimeter measurement through a compatible design. It has both the performance of pulsed laser altimeter to achieve long-distance measurement and the high measurement accuracy of phase-type laser altimeter. At the same time, it does not require cooperative targets or the installation of cooperative devices on non-cooperative targets, which greatly expands the application scenarios of laser altimeters.

[0027] 4. Except for the necessary laser transmitting circuit and laser receiving circuit in the laser transceiver module, the laser altimeter can realize all logic and control using only a single SOC chip. The SOC chip uses the domestic chip FMQL20S484-N, which integrates 1 high-performance FPGA and 2 ARM hard cores, integrating the hardware programmability of FPGA and the software programmability of ARM. The system has excellent performance and is highly flexible and scalable. Compared with the hardware architecture of the traditional FPGA chip + CPU chip, the SOC chip has obvious advantages in cost and power consumption, and there is no need to design additional communication and data interaction interfaces between the FPGA and the CPU, so the development difficulty is low and the work efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the principle of the utility model;

[0029] Figure 2 This is a schematic diagram of the principle of the laser emission unit in the utility model;

[0030] Figure 3 This is a schematic diagram of the principle of the photoelectric conversion module in the utility model;

[0031] Figure 4 This is a schematic diagram of the principle of the temperature compensation module in the utility model;

[0032] Figure 5 It is a software module block diagram in the utility model. DETAILED DESCRIPTION

[0033] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0034] Reference Figure 1 The utility model provides a laser altimeter with temperature compensation, which includes a laser emitting unit 1, a laser receiving unit 2, a lens unit 3, a digital signal processing unit 4 and an EMI power supply filtering unit 5. Wherein: the laser emitting unit 1 is connected to the digital signal processing unit 4 and the lens unit 3 respectively, and is used to receive the semi-continuous sinusoidal modulation signal emitted by the digital signal processing unit 4, and emit a 905nm laser; the laser receiving unit 2 is connected to the digital signal processing unit 4 and the lens unit 3 respectively, and is used to receive the optical signal reflected by the target and convert it into an electrical signal, and send it to the digital signal processing unit 4; the lens unit 3 is located in front of the laser emitting unit 1 and the laser receiving unit 2, and is used to collimate and parallelize the laser emitted by the laser emitting unit 1 to the ground, and focus the echo reflected by the ground to the photoelectric conversion module 21 in the laser receiving unit 2; the digital signal processing unit 4 is connected to the laser emitting unit 1 and the laser receiving unit 2 respectively, and is used to calculate the pulse counting and phase delay of the emission signal and the echo signal, and send them to the flight and control computer periodically after filtering; the EMI power supply filter unit 5 is connected to the laser emitting unit 1, the laser receiving unit 2 and the digital signal processing module 4 respectively, and is used to perform EMI electromagnetic compatibility processing on the onboard power supply, and transform the power supply after preprocessing, so as to provide a low-voltage DC power supply that meets the requirements for each power supply object.

[0035] Reference Figure 2 The laser emitting unit 1 includes a driving module 11 and a semiconductor laser 12, wherein the driving module 11 is connected to the semiconductor laser 12, and includes a DC bias circuit 111 and an adder circuit 112, wherein the DC bias circuit 111 provides a stable DC bias signal for the semiconductor laser 12, and the adder circuit 112 is used to superimpose the sinusoidal modulation signal generated by the DDS signal sinusoidal generator 42 with the DC bias signal, and send the superimposed signal to the semiconductor laser 12, so that the semiconductor laser 12 emits a 905nm laser;

[0036] The laser receiving unit 2 includes a photoelectric conversion module 21 and a temperature compensation module 22. The photoelectric conversion module 21, as shown in FIG. Figure 3As shown, it includes a photoelectric conversion circuit 211 and an amplifying and filtering circuit 212. The photoelectric conversion circuit 211 uses an APD photodiode as a photoelectric conversion chip to convert an optical signal into an electrical signal and transmit it to the amplifying and filtering circuit 212 for amplification and filtering; the temperature compensation module 22, as shown Figure 4 As shown, it includes a temperature sensor 221, an operational amplifier 222 and a boost chip 223, wherein:

[0037] The temperature sensor 221 uses a HYM590 temperature sensor to collect ambient temperature parameters, converts them into analog voltages and outputs them to the inverting input terminal of the operational amplifier 222;

[0038] The operational amplifier 222 adopts a subtractor circuit, whose in-phase input terminal is connected to the output terminal of the boost chip 223 through a voltage-dividing feedback resistor, and whose inverting input terminal receives the analog voltage converted by the temperature parameter collected by the temperature sensor 221, and the output voltage is sent to the control input terminal of the boost chip 223. It is used to output the difference between the output voltage of the boost chip 223 after voltage division and the analog voltage converted by the temperature sensor 221 to the control input terminal of the boost chip 223;

[0039] The control input of the boost chip 223 is connected to the output of the operational amplifier 222, and the chip CN5120 is used for boost control. Its internal reference voltage V ref =1.205V, when the control input voltage is lower than the internal reference voltage V ref , the boost chip 223 adjusts the output duty cycle to increase the output voltage, otherwise it reduces the output voltage. After the output voltage is divided, it is fed back to the control input terminal of the boost chip 223 through the operational amplifier 222. The output voltage is repeatedly adjusted until the control input voltage is equal to the internal reference voltage V ref Its output voltage is sent to the photoelectric conversion module 21 to provide a bias voltage for the APD photodiode.

[0040] The lens unit 3 includes a transmitting lens 31 and a receiving lens 32. The transmitting lens 31 is located in front of the semiconductor laser 12 and is used to compress the laser divergence angle to achieve collimated parallel emission of the laser. The receiving lens 32 is located in front of the photoelectric conversion module 21 and is used to receive the echo reflected from the ground and focus the echo to the photoelectric conversion module 21 to convert it into an electrical signal and amplify and filter it.

[0041] The digital signal processing unit 4 includes: a SOC chip 41, a DDS sinusoidal signal generator 42, a comparator 43, a high-frequency AD conversion chip 44, a high-frequency AD conversion chip 45, a power distributor 46, a software module 47, and a power distributor 48. The SOC chip 41 is connected to the DDS sinusoidal signal generator 42, the comparator 43, the high-frequency AD conversion chip 44, and the high-frequency AD conversion chip 45, respectively, and a data preprocessing module 411 and a data processing module 412 are integrated therein.

[0042] The data preprocessing module 411 is connected to the data processing module 412, and a phase-locked loop PLL is embedded in the data preprocessing module 411. The phase-locked loop is used to perform multiple phase shifts on the initial counting clock to form several groups of counting clocks with fixed phase differences. The input pulse signals are counted respectively, that is, the initial counting clock is multiplied, and clock counting, digital signal sampling and phase difference measurement are completed. The counting result and phase difference are sent to the data processing module 412 for height resolution.

[0043] The DDS sinusoidal signal generator 42 is connected to the SOC chip 41 and the power distributor 48 respectively. The SOC chip 41 configures the frequency control word and the phase control word of the DDS sinusoidal signal generator 42 to control the frequency and phase of the output signal of the DDS sinusoidal signal generator 42 so that it generates a semi-continuous sinusoidal signal. At the same time, the data preprocessing module 411 counts the clock and starts counting to obtain the initial time.

[0044] The input end of the power divider 48 is connected to the DDS sinusoidal signal generator 42, and the two output ends are respectively connected to the driving module 11 and the high-frequency AD conversion chip 45, and are used to divide the semi-continuous sinusoidal signal into two transmission signals, wherein the first transmission signal enters the driving module 11, and the second transmission signal enters the high-frequency AD conversion chip 45;

[0045] The input end of the power distributor 46 is connected to the photoelectric conversion module 21, and the two output ends are connected to the comparator 43 and the high-frequency AD conversion chip 44 respectively, and is used to divide the high-frequency sinusoidal signal output by the photoelectric conversion module 21 into two paths, and output them to the comparator 43 and the high-frequency AD conversion chip 44 respectively;

[0046] The comparator 43 is connected to one signal of the photoelectric conversion module 21 and the SOC chip 41 respectively, and is used to convert the high-frequency sinusoidal signal output by the photoelectric conversion module 21 into a pulse signal and output it to the SOC chip 41, count the clock termination pulse count to obtain the termination time, and record the number of clock cycles between the initial time and the termination time;

[0047] The high-frequency AD conversion chip 44 is connected to the other signal of the photoelectric conversion module 21 and the SOC chip 41 respectively, and is used to convert the high-frequency sinusoidal signal output by the photoelectric conversion module 21 into a digital signal and send it to the SOC chip 41;

[0048] The high-frequency AD conversion chip 45 is connected to the second signal of the DDS signal sine generator 42 and the SOC chip 41 respectively, and is used to convert the sine signal generated by the DDS signal sine generator 42 into a digital signal and send it to the SOC chip 41. The two AD digital signals realize phase difference measurement;

[0049] Reference Figure 5 The software module 47 includes a self-test submodule 471, a height measurement submodule 472, a height status word setting submodule 473, an RS422 command receiving submodule 474, and a data packaging and output submodule 475. It is solidified in the SOC chip 41, wherein:

[0050] A self-test submodule 471, for performing power-on self-test, periodic self-test and maintenance self-test;

[0051] The height measurement submodule 472 is used to perform clock counting and phase difference calculation, that is, to calculate the phase difference between the received signal and the transmitted signal through multiplication operation, CIC filter and CORDIC phase angle algorithm, to solve the initial height information, and to filter the initial height through the filtering algorithm;

[0052] The height status word setting submodule 473 is used to set the self-test result to the fault / normal state of the laser altimeter;

[0053] RS422 command receiving submodule 474 is used to receive instructions transmitted by the flight control and management computer, including maintenance self-check, query remaining altitude, and zeroing commands, among which;

[0054] The maintenance self-check command is used to force the altimeter to enter the self-check state; the query remaining altitude command is used to save the set remaining altitude in the fixed address of the laser altimeter storage device. The query remaining altitude command can read the remaining altitude value in the local storage device; the zero adjustment command is used to solve the problem that the altitude display of the carrier when it stops on the ground is not zero due to reasons such as the carrier load and cable length, and adjust the current output altitude to 0m to achieve the purpose of zero adjustment;

[0055] The data packaging and output submodule 475 is used to package the altitude information, status information and self-test results, and send them to the flight control and management computer through the RS422 interface.

[0056] The utility model uses the above-mentioned high-precision laser altimeter with temperature compensation to measure the height according to the following principles:

[0057] 1) The laser altimeter starts self-test.

[0058] Run the self-test submodule 471 to perform power-on self-test and periodic self-test, that is, after the laser altimeter is powered on, the software sends a self-test control signal to make the laser altimeter enter the self-test mode and perform self-test on each functional module of the laser altimeter; during the operation of the laser altimeter software, the laser altimeter performs self-test on each functional module periodically; these two self-test items include: detection of the presence or absence of laser pulses, detection of frequency modulation frequency, detection of power supply function, self-test of laser transmitting unit, self-test of laser receiving unit, self-test of digital signal processing unit, self-loop detection of RS422 module function, etc.

[0059] 2) The temperature compensation module 22 performs automatic temperature compensation on the APD photodiode bias voltage.

[0060] Reference Figure 4 , the implementation principle of this step is as follows:

[0061] When the ambient temperature is T0 = 22°C, the APD breakdown voltage U BR0 is 130V, the temperature coefficient is α=0.45V / ℃, the bias voltage U R =KU BR0 =123.5V, where the gain K = 0.95, the bias voltage output by the boost chip 223 is adjusted to the target value U R =123.5V, at this time, the voltage at the input terminal of the boost chip 223 is controlled by the internal reference voltage V ref =1.205V is equal;

[0062] When the ambient temperature is higher than T0 = 22°C, the breakdown voltage of the APD changes to U BR0 +α(T-T0), the analog voltage converted from the temperature parameter collected by the temperature sensor 221 increases, further making the voltage at the control input end of the boost chip 223 lower than the internal reference voltage. At this time, it adjusts the duty cycle so that the output bias voltage U R Increase.

[0063] When the outside temperature is lower than T0 = 22°C, the voltage at the control input of the boost chip 223 is higher than the internal reference voltage, and the bias voltage U output by the boost chip 223 is R The bias voltage satisfies U R =K[U BR0 +α(T-T0)]=123.5+0.428(T-T0).

[0064] The ambient temperature of this example is -40℃-70℃, and the APD bias voltage U RThe temperature compensation module 22 can automatically compensate the bias voltage of the APD photodiode at different temperatures to maintain the gain stability of the APD photodiode.

[0065] 3) The laser altimeter operates the altitude measurement submodule 472 to simultaneously measure the pulse-phase of the transmitted signal and the received signal to obtain the time for a round trip of the light pulse.

[0066] 3.1) The SOC chip 41 count clock generates four count clocks clk_0, clk_90, clk_180, clk_270 with a phase difference of 90° through a phase-locked loop, and counts the pulses respectively, that is, counts at 4 times the clock frequency, and the coarse time interval t1 is measured by recording the number of clock cycles;

[0067] 3.2) The SOC chip 41 calculates the phase delay φ of the portion of the received signal that is less than a complete pulse cycle relative to the transmitted signal through multiplication operation, CIC filtering and CORDIC phase angle algorithm:

[0068] 3.2.1) The SOC chip 41, the high-frequency AD conversion chip 44, and the high-frequency AD conversion chip 45 share a crystal oscillator, and start to extract the sampling data of the first point at the rising edge of the fourth clock of the FPGA to obtain the laser emission signal S A and the received signal S B :

[0069] S A =Acos(wt+θ1),

[0070] S B =Bcos(wt+θ2)

[0071] Where θ1 is S A The initial phase of S B The initial phase, S 01 and S 02 is a quadrature signal S with a phase difference of 90° 01 =Csin(wt+θ0),S 02 =Ccos(wt+θ0), θ0 is S 01 and S 02 The initial phase of

[0072] 3.2.2) Use the internal multiplier resources of SOC chip 41 to implement S A ×S 01 , and get the double frequency signal and DC signal:

[0073]

[0074] in, is the double frequency part, It is the DC signal part;

[0075] 3.2.3) Extract S through CIC filtering A ×S 01 The DC signal in the product result is Simultaneously perform S A ×S 02 Operation, and then extract the DC signal after CIC filtering:

[0076] 3.2.4) The two DC signals extracted in 3.2.3) are calculated using the CORDIC phase angle algorithm to obtain θ0-θ1; similarly, for S B =Bcos(wt+θ2) is subjected to the above process, and θ0-θ2 is calculated by multiplication operation, CIC filtering and CORDIC phase angle algorithm, and the phase delay φ=θ1-θ2 can be obtained, and the detailed flight time interval can be calculated:

[0077]

[0078] Where f is the frequency of the sinusoidal modulation signal.

[0079] 3.2.5) The round trip time t of the light pulse is calculated based on the coarse measurement time interval t1 and the fine measurement flight time interval t2:

[0080] t=t1+t2.

[0081] 4) Based on the round-trip flight time t of the light pulse, the altitude is calculated and sent to the flight control and management computer.

[0082] According to the flight time t, the initial altitude information H=ct / 2 is calculated;

[0083] The obtained initial altitude is filtered by the filtering algorithm, and converted into the agreed data type for packaging, and sent to the flight control and management computer through the 422 bus;

[0084] The flight control and management computer calculates the current vertical distance based on the aircraft attitude information, and the height measurement range it outputs is 0.1m-240m. When the height is greater than 240m, it outputs "overrange", and when the height is less than 0.1m, it outputs 0m.

[0085] The actual measurement results show that the height measurement accuracy of the utility model is less than 0.075m, and the power consumption is not more than 6W; the outer dimensions of the laser altimeter are not more than 60mm×100mm×104mm, and the weight is not more than 0.6kg.

[0086] The above description is only a specific example of the present invention and does not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principle of the present invention, they may make various modifications and changes in form and details without departing from the principle and structure of the present invention. However, these modifications and changes based on the idea of ​​the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A high-precision laser altimeter with temperature compensation, comprising a laser emitting unit (1), a laser receiving unit (2), a lens unit (3), a digital signal processing unit (4) and an EMI power supply filtering unit (5), characterized in that: A laser receiving unit (2), comprising a photoelectric conversion module (21) and a temperature compensation module (22); The photoelectric conversion module (21) comprises a photoelectric conversion circuit (211) and an amplifying and filtering circuit (212); the photoelectric conversion circuit (211) uses an APD photodiode as a photoelectric conversion chip, and is used to convert an optical signal into an electrical signal, which is transmitted to the amplifying and filtering circuit (212) for amplification and filtering; The temperature compensation module (22) comprises a temperature sensor (221), an operational amplifier (222) and a boost chip (223); the temperature sensor (221) collects ambient temperature parameters and converts the temperature parameters into analog voltages, which are output to the boost chip (223) through the operational amplifier (222) for boosting and then output to the photoelectric conversion circuit in the photoelectric conversion module (21), thereby providing a bias voltage for the APD photodiode. The output voltage of the boost chip changes with temperature, thereby achieving automatic compensation of the bias voltage of the APD photodiode with temperature.

2. The altimeter according to claim 1, characterized in that: The laser emitting unit (1) comprises a driving module (11) and a semiconductor laser (12); The driving module (11) comprises a DC bias circuit (111) and an adder circuit (112), wherein the DC bias circuit (111) provides a stable DC bias signal for the semiconductor laser (12), and the adder circuit (112) is used to superimpose a sinusoidal modulation signal generated by a DDS sinusoidal signal generator (42) and the DC bias signal; The semiconductor laser (12) is connected to the driving module (11) and is used to receive a DC bias signal sent by the driving module and emit 905nm laser.

3. The altimeter according to claim 1, characterized in that: The lens unit (3) comprises a transmitting lens (31) and a receiving lens (32); The emission lens (31) is located in front of the semiconductor laser (12) and is used to compress the laser divergence angle to achieve collimated parallel emission of the laser; The receiving lens (32) is located in front of the photoelectric conversion module (21) and is used to receive the echo reflected from the ground, focus the echo to the photoelectric conversion module (21), convert it into an electrical signal, and amplify and filter it.

4. The altimeter according to claim 1, characterized in that: The EMI power supply filter unit (5) is respectively connected to the laser emitting unit (1), the laser receiving unit (2) and the digital signal processing unit (4), and is used to perform EMI electromagnetic compatibility processing on the onboard power supply and transform the power supply after pre-processing to provide low-voltage direct current power supply that meets the requirements for each power supply object.

Images