Comprehensive tester of portable laser altimeter

Abstract

The utility model discloses a comprehensive tester of a portable laser altimeter, which mainly solves the problem of low precision of detecting the laser altimeter in the prior art, and comprises a receiving unit, a transmitting unit and a signal processing unit, the receiving unit comprises a receiving coupling module, an optical attenuator, a photoelectric mutual converter and an optical switch, a laser signal enters the optical attenuator through the receiving coupler to be attenuated, then enters the photoelectric converter to be converted, and then enters the input end of the optical switch. The transmitting unit comprises a transmitting coupling module and a time-delay optical fiber; a laser signal of the input end of the optical switch is delayed by the time-delay optical fiber and then enters the laser altimeter through transmitting coupling; the signal processing unit comprises a driving module, a communication module and a liquid crystal display screen, and the driving module switches the optical switch to the delay optical fiber, calculates a height value corresponding to the laser signal, and compares the height value with an initial value to generate a precision value of the laser altimeter. According to the utility model, the test absolute error can be reduced, the test precision of the laser altimeter is improved, and the device can be used for calibration and debugging of the laser altimeter.

Description

Technical Field

[0001] The utility model belongs to the technical field of laser ranging, and specifically relates to a comprehensive tester, which can be used for calibration, debugging and software upgrading of laser ranging devices such as laser altimeters and laser rangefinders. Background Art

[0002] As an essential instrument on helicopters, the altimeter provides ground clearance measurement information for the flight control management system, provides altitude information for the altitude holding function of the aircraft and during autonomous takeoff and landing, and ensures the smooth operation and takeoff / landing of the helicopter. At present, existing radio altimeter products are widely equipped on various types of helicopters, fixed-wing aircraft, drones and missiles. The foreign Smart company launched a miniature radio altimeter at the Berlin Air Show. It is small in size, weighs only 160g, has low power requirements for the system, can measure altitudes in the range of 0.5m - 500m, and is small in weight and low in power consumption. In recent years, the new digital radio altimeters developed by Shaanxi Changling Electronic Technology Co., Ltd. in China, such as the 261 and 291 series, have strong stability.

[0003] However, these radio altimeters all have the problem of low measurement accuracy for the ground clearance height, and it is difficult to achieve high-precision measurement. Therefore, with the development and popularization of laser ranging technology, designers began to develop laser devices such as laser altimeters and laser rangefinders for low-altitude or ground-hugging flight altitude measurement, which can provide high-precision altitude information for helicopters. The laser altimeter developed by Bushnell in the United States is combined with a binocular telescope, which can perform high magnification and long-distance ranging. For example, the 202310 telescope it developed integrates laser ranging function, and the ranging range can reach 1760 meters, and it can ensure high reliability even in a poor environment. Jiangsu Changzhou Laisei Co., Ltd. established a laser measurement laboratory in 2018. The LS208 non-cooperative target ultra-long-range safety laser altimeter it developed has a measurement range of 100m - 5000m, can store 1000 measurement data, and the ranging accuracy is ±0.5mm.

[0004] However, in practical applications, due to the high sensitivity of lasers, they are easily affected by various factors such as temperature and reflecting surfaces. As a result, the accuracy of laser altimeters is sometimes high and sometimes low, unstable, which affects the measurement accuracy. Therefore, during the debugging stage of laser altimeters, supporting laser debugging equipment is required to verify the accuracy of laser altimeters and achieve accurate height measurement of helicopters. Currently, both at home and abroad, for the developed laser altimeters, only the traditional field measurement method can be used to verify the equipment accuracy, resulting in a relatively large relative error. During the development of laser equipment, the high sensitivity of lasers is extremely sensitive to the material of the reflecting surface, and different reflecting surfaces will have different measurement accuracies. Therefore, it is impossible to accurately evaluate the measurement accuracy of laser equipment, causing considerable difficulties in the debugging of laser equipment. During small-batch production, the actual conditions in the indoor or process environment often fail to reach the required measurement range of the equipment, resulting in the equipment being unable to accurately evaluate the measurement range. During the actual application process of laser altimeters, unified special instruments are required for the debugging and software upgrade of laser altimeters. Therefore, a comprehensive tester for portable laser altimeters is very necessary for laser altimeters. Moreover, most laser debugging equipment often has multiple sub-units, each sub-unit is relatively large in volume, heavy, inconvenient to maintain, not easy to carry, causing serious inconvenience to the debugging of laser equipment. Utility Model Content

[0005] The purpose of the present utility model is to propose a comprehensive tester for portable laser altimeters in view of the above-mentioned deficiencies of the existing technologies, so as to improve the calibration accuracy of laser altimeters at various stages, reduce the volume and weight of the debugging equipment, and meet the high-precision requirements for portable testing of laser altimeters by helicopters.

[0006] The technical idea to achieve the above purpose is as follows: During the R & D and production stage of laser altimeters, by using multi-segment high-precision delay optical fibers to convert different optical signals into different height signals, simulating the transmission of lasers in an ideal state, enabling the laser altimeter to simulate different measurement distances in indoor or process environment tests, reducing the absolute error during the debugging of the laser altimeter, and improving the accuracy of the laser altimeter. By adopting a compact design, directly connecting to the laser altimeter using an adapter plug, and using the same power supply and the same communication bus as the laser altimeter, reducing the volume and weight of the comprehensive tester for laser altimeters, making it easy to carry, facilitating software upgrade and distance simulation of the laser altimeter at any time during the field application stage, ensuring the debugging of the laser altimeter, reducing errors caused by factors such as environment and temperature, and improving the accuracy of the laser altimeter.

[0007] According to the above idea, the technical solution of the present utility model is as follows:

[0008] 1. A comprehensive tester for portable laser altimeters, comprising a receiving unit, a transmitting unit, and a signal processing unit, characterized in that:

[0009] The receiving unit includes: a receiving coupling module, an optical attenuator, an optoelectronic converter, and an optical switch. The laser signal emitted by the laser altimeter passes through an optical coupler and enters the optical attenuator. After attenuation, it enters the optoelectronic converter to convert the optical signal into an electrical signal, and then enters the selected optical switch to complete the reception of the laser signal.

[0010] The transmitting unit includes: a transmitting coupling module and a delay optical fiber. The laser signal passes through the optical switch, is delayed by the delay optical fiber, and then is transmitted through the transmitting coupler and enters the receiving module of the laser altimeter.

[0011] The signal processing unit includes a driving module, an RS422 communication module, and a liquid crystal display. The driving module is used to switch the optical switch to the corresponding delay optical fiber to achieve the delay of the laser signal. The laser altimeter calculates the height value corresponding to the laser signal and compares it with the height value of the laser altimeter input manually to generate the accuracy value of the laser altimeter, which is transmitted to the liquid crystal display through the RS422 communication module.

[0012] Further, the receiving coupling module includes:

[0013] A spot shaping optical path, which uses a 0.4X cylindrical lens 14 beam expansion system to reduce the long axis of the spot and reduce the spot aspect ratio.

[0014] A focusing optical path, which is used to couple the laser signal into a 50 / 125μm multimode optical fiber. The total received power is 3.64E-4W, i.e., -4.4dBm, and the total received power at the core + cladding end face is 2.29E-3W, i.e., 3.6dBm.

[0015] Input parameter setting: Set its divergence angle to a fixed value according to different spots at different depths, and the output optical power is between 190mw - 300mw to ensure that the laser altimeter comprehensive tester receives the optical signal emitted by the laser altimeter.

[0016] Further, the transmitting coupling module includes a collimating lens and a connecting optical fiber: The collimating lens is located at the receiving end of the laser altimeter, and its light transmittance is greater than 99%. It is used to collimate the laser signal and then transmit it so that it is received by the receiving end of the laser altimeter. The connecting optical fiber has a diameter matching that of the collimating lens.

[0017] Further, the optical switch is connected to the optical attenuator and is used to switch the received laser signal to the corresponding delay optical fiber. The number of the optical switch is the same as the number of the delay optical fibers, and the wavelength is the same as the wavelength of the transmitted laser signal.

[0018] Further, the optoelectronic converter is connected to the optical attenuator and is used to convert the laser signal and the electrical signal mutually.

[0019] Further, the optical attenuator is connected to the receiving coupling module and is used to adjust the laser signal that enters the laser altimeter integrated tester through the optical coupler. The minimum value of the adjustment is greater than the maximum value of the optical power of the receiving coupling module, and the maximum value of the adjustment is jointly determined by the maximum value of the delay optical fiber, the insertion loss during connection of each part, and the coupling efficiency of the receiving coupling module.

[0020] Further, the delay optical fiber is connected to the optical switch and is used to delay the laser signal received by the laser altimeter integrated tester. The number of the delay optical fibers is consistent with the number of test points in the measurement range, the precision of the optical fiber length is less than the precision value of the laser altimeter, and its length is calculated according to the measurement range of the laser altimeter, the propagation time of light in the corresponding space, the precision of the laser altimeter, and the precision of the optical fiber length.

[0021] Further, the driving module includes an initialization module and a driving circuit. The initialization module is used to convert the test value of the laser altimeter into the input value of the laser altimeter integrated tester. It is set to n gears according to the measurement range of the laser altimeter, and m test points are set for each gear. The intervals between adjacent two test points are evenly set to ensure that the range from the initial test point to the final test point completely covers the measurement range of the laser altitude. The driving circuit is used to amplify the electrical signal generated by the initialization module and then drive the optical switch to switch to the corresponding delay optical fiber and drive the optical switch to turn off.

[0022] Further, the RS422 communication module is connected to the laser altimeter and is used to perform full-duplex communication with the laser altimeter. That is, the communication module RS422 sends a self-check control status word, receives the self-check information of the laser altimeter, the height measurement data information, the data refresh rate, the data delay time, and the overall power consumption replied by the laser altimeter, and decodes the Chinese characters of these received information into "normal" or "fault" and sends them to the liquid crystal display screen.

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

[0024] 1. The present utility model uses a spot shaping optical path and a focusing optical path to receive the laser signal, effectively removing the error caused by different reflection surfaces during the debugging of the laser signal, and improving the calibration accuracy of the laser altimeter.

[0025] 2. The present utility model uses a delay optical fiber to delay the laser signal, simulating the transmission of the laser signal in an ideal state, solving the problem that it is difficult to comprehensively detect the measurement range of the laser altimeter due to insufficient distance in indoor or process environment tests, reducing the absolute error during the debugging of the laser altimeter, and further improving the calibration accuracy of the laser altimeter.

[0026] 3. The utility model uses an RS422 communication module to communicate with a laser altimeter, enabling debugging and software upgrade of the laser altimeter, thus filling the gap in the market for laser altimeter debugging equipment.

[0027] 4. The utility model is connected to the laser altimeter via a cable and uses the dual power supply of the laser altimeter, ensuring its working state, reducing weight, and facilitating portability. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 2 is a schematic diagram of the optical path of the receiving coupling module in the utility model;

[0030] Figure 3 is a schematic diagram of the optical path of the optical switch in the utility model;

[0031] Figure 4 is a schematic diagram of the optical path of the transmitting coupling module in the utility model;

[0032] Figure 5 is a block diagram for implementing the detection of the calibration accuracy of the laser altimeter in the utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following describes the embodiments of the present invention in detail with reference to the accompanying drawings.

[0034] Refer to Figure 1 , the laser altimeter comprehensive tester in this embodiment includes a receiving unit 1, a transmitting unit 2, and a signal processing unit 3. The receiving unit 1 receives the laser signal emitted by the laser altimeter. After the received laser signal is delayed, it enters the transmitting unit 2. The transmitting unit transmits the laser signal to the laser altimeter, and the laser altimeter processes the laser signal to generate height measurement data and sends it to the signal processing unit 3. The signal processing unit 3 calculates the height measurement data to obtain the accuracy value of the laser altimeter.

[0035] The receiving unit 1 includes a receiving coupling module 11, an optical attenuator 12, an optoelectronic converter 13, and an optical switch 14. The receiving coupling module 11 receives the laser signal, and the laser signal enters the optical attenuator 12 for adjustment. After the adjustment is completed, it enters the optoelectronic converter 13, and after the conversion is completed, it enters the input end of the optical switch 14.

[0036] Refer to Figure 2, the receiving and coupling module 11 includes a spot shaping optical path 111 and a focusing optical path 112. The laser signal enters the spot shaping optical path 111, and after shaping, it enters the focusing optical path 112 to complete the reception of the laser signal. The spot shaping optical path 111 uses a 0.4X cylindrical lens beam expander system to reduce the long axis of the spot and reduce the aspect ratio of the spot; the focusing optical path 112 is used to couple the laser signal into a 50 / 125μm multimode optical fiber. The total power received by the fiber core is 3.64E-4W, i.e., -4.4dBm, and the total power received by the fiber core + cladding end face is 2.29E-3W, i.e., 3.6dBm.

[0037] The optical attenuator 12 is used to adjust the laser signal in the range of 1 - 7dB. The maximum value of the adjustment range of the optical attenuator is related to the fiber receiving power, and the fiber receiving power is calculated as follows:

[0038] When it is completely aligned, the total power received by the core of the 50 / 125μm multimode optical fiber is 3.64E-4W, i.e., -4.4dBm, and the total power received by the core + cladding is 2.29E-3W, i.e., 3.6dBm;

[0039] When the vertical deviation is 0.5°, the total power received by the core of the 50 / 125μm multimode optical fiber is 3.18E-4W, i.e., -5.0dBm, and the total power received by the core + cladding is 1.99E-3W, i.e., 3.0dBm;

[0040] When the vertical deviation is 1°, the total power received by the core of the 50 / 125μm multimode optical fiber is 2.02E-4W, i.e., -6.9dBm, and the total power received by the core + cladding is 1.24E-3W, i.e., 0.9dBm;

[0041] When the horizontal deviation is 0.5°, the total power received by the core of the 50 / 125μm multimode optical fiber is 2.02E-4W, i.e., -5.2dBm, and the total power received by the core + cladding is 1.24E-3W, i.e., 2.8dBm;

[0042] When the horizontal deviation is 1°, the total power received by the core of the 50 / 125μm multimode optical fiber is 1.71E-4W, i.e., -7.7dBm, and the total power received by the core + cladding is 1.07E-3W, i.e., 0.3dBm;

[0043] Considering the system deviation analyzed above, when the laser signal is coupled into a 50 / 125μm multimode optical fiber, the total power received by its core is 1.71E-4W, i.e., -7.7dBm, that is, the maximum value of the adjustment range of the optical attenuator is 7dB;

[0044] The optoelectronic converter 13 is connected to the optical attenuator 12 and is used to convert the laser signal and the electrical signal into each other.

[0045] Refer toFigure 3 The optical switch 14 is connected to the delay optical fiber 22, with a total of 1×20 fibers, having a wavelength of 905 nm, and is configured to switch the received laser signal to the delay optical fiber.

[0046] The transmitting unit 2 includes a transmitting coupling module 21 and a delay optical fiber 22. The laser signal located at the input end of the optical switch 14 is delayed by the selected delay optical fiber 22 and then transmitted through the transmitting coupling 21 and enters the receiving module of the laser altimeter.

[0047] Refer to Figure 4 The transmitting coupling module 21 includes a collimating lens 211 and a connecting optical fiber 212. The laser signal is connected to the connecting optical fiber 212 through the collimating lens 211 to transmit the laser signal. The collimating lens 211 is located at the receiving end of the laser altimeter, and its light transmittance is greater than 99%. It is used to collimate the laser signal and then transmit it so that it can be received by the receiving end of the laser altimeter. The connecting optical fiber 212 is selected as NA0.2, but is not limited to this model, and it is matched with the collimating lens 211.

[0048] The delay optical fiber 22 is configured to delay the laser signal received by the laser altimeter integrated tester. In this example, there are 20 delay optical fibers with different lengths. Each fiber loop composed of each optical fiber has 5 grids, and each grid winds 4 segments of optical fiber. Each optical fiber uses OM3 optical fiber to transmit the 905 nm laser signal. The length of each delay optical fiber is calculated according to the measured height and the propagation time of light in the corresponding space. Among them, the measurement accuracy of the laser altimeter is not greater than 0.075 m, which is converted to a time accuracy of 0.25×10 -9 s, the optical fiber length accuracy is ±25 mm, the measurement range of the laser altimeter is 0.1 m - 255 m, and the optical fiber length results are shown in the following table:

[0049]

[0050] The signal processing unit 3 includes a driving module 31, an RS422 communication module 32, and a liquid crystal display screen 33. After the laser altimeter receives the laser signal, it calculates the height value corresponding to the laser signal, compares it with the input height value of the laser altimeter, generates the accuracy value of the laser altimeter, and transmits it to the liquid crystal display screen 33 through the RS422 communication module 32. Among them:

[0051] The driving module 31 includes an initialization module 311 and a driving circuit 312. The initialization module 311 sends an input value to the driving circuit 312 to complete the switching of the optical switch 14. The initialization module 311 is set to 4 gears according to the measurement range of the laser altimeter, with 5 test points set for each gear, and the intervals between adjacent test points are evenly set to ensure that the range from the initial test point to the final test point completely covers the measurement range of the laser height, which is 0 - 255m. The driving circuit 312 is used to receive the electrical signal generated by the initialization module 311, amplify it, drive the optical switch 14 to switch to the corresponding delay optical fiber 15, and drive the optical switch 14 to turn off.

[0052] The RS422 communication module 32 is connected to the laser altimeter and is used for full-duplex communication with the laser altimeter. That is, the communication module RS422 sends a self-check control status word, receives the self-check information of the laser altimeter, altitude measurement data information, data refresh rate, data delay time, and the overall power consumption of the laser altimeter replied by the laser altimeter, and decodes the Chinese characters of these received information into "normal" or "fault" and sends them to the liquid crystal display screen 33.

[0053] Refer to Figure 5 , the implementation of testing the accuracy of the laser altimeter using the above comprehensive tester is as follows:

[0054] 1) Turn on the power supply and supply power to the laser altimeter and the laser altimeter comprehensive tester simultaneously through the cable;

[0055] 2) The laser altimeter emits a laser signal. After the laser signal converges, it enters the laser altimeter comprehensive tester. Through its receiving coupling module 11, after passing through the optical attenuator 12, and then through the optoelectronic converter 13, it enters the input end of the optical switch 14;

[0056] 3) Input the altitude value on the laser altimeter comprehensive tester, and drive the optical switch 14 to switch to the corresponding delay optical fiber 15 through the signal processing unit 3 to delay the laser signal;

[0057] 4) The laser signal after the delay ends enters the transmitting coupling module 12 for laser signal convergence, and then enters the receiving module of the laser altimeter;

[0058] 5) The laser altimeter amplifies the received laser convergence signal and then detects it to obtain the time difference when the laser signal is received and transmitted. The altitude measurement data M corresponding to the laser signal is calculated using the following formula n ;

[0059]

[0060] In the formula: c is the propagation speed of the laser signal in the air, t is the total propagation time of the laser signal, and N is the number of full cycles of the laser signal in the full journey. is the phase ratio less than one period, and f is the signal frequency of the laser signal;

[0061] 6) The signal processing unit 3 compares the height measurement data M calculated by the laser altimeter n with the height value input on the laser altimeter integrated tester in step 3), calculates the accuracy ε of the laser altimeter by using the following formula, and displays it through the liquid crystal screen 33.

[0062] ε = M n - M 0

[0063] where: M 0 is the input height value of the laser altimeter integrated tester.

[0064] The above description is only a specific example of the present invention and does not constitute any limitation to the present invention. Obviously, for professionals in the field, after understanding the content and principle of the present invention, various modifications and changes in form and details may be made 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 protection scope of the claims of the present invention.

Claims

1. A comprehensive tester for a portable laser altimeter, comprising a receiving unit (1), a transmitting unit (2), and a signal processing unit (3), characterized in that: The receiving unit (1) comprises: a receiving coupling module (11), an optical attenuator (12), a photoelectric converter (13), and an optical switch (14); a laser signal emitted by a laser altimeter passes through the receiving coupling module (11), enters the photoelectric attenuator (12), and after attenuation, enters the photoelectric converter (13) to convert the laser signal into an electrical signal, and then enters the selected input end of the optical switch (14), completing the reception of the laser signal; The transmitting unit (2) comprises: a transmitting coupling module (21) and a delay optical fiber (22); the laser signal at the input end of the optical switch (14) is delayed by the selected delay optical fiber (22), then transmitted through the transmitting coupling module (21) and enters the receiving module of the laser altimeter; The signal processing unit (3) comprises a driving module (31), an RS422 communication module (32) and a liquid crystal display screen (33). The driving module (31) causes the optical switch (14) to switch to the corresponding delay optical fiber (22) to achieve the delay of the laser signal, and calculates the altitude value corresponding to the laser signal through the laser altimeter, compares it with the input laser altimeter altitude value, generates the accuracy value of the laser altimeter, and transmits it to the liquid crystal display screen (33) through the RS422 communication module (32).

2. The comprehensive tester according to claim 1, characterized in that: The receiving coupling module (11) comprises a light spot shaping optical path (111) and a focusing optical path (112): The light spot shaping optical path (111) uses a 0.4X cylindrical mirror 14 beam expansion system to reduce the long axis of the light spot and reduce the aspect ratio of the light spot; The focusing optical path (112) is used to couple the laser signal into the 50 / 125 μm multimode optical fiber. The total received power is 3.64E-4W, i.e. -4.4dBm, and the total received power at the core+cladding end face is 2.29E-3W, i.e. 3.6dBm.

3. The comprehensive tester according to claim 1, characterized in that: The emission coupling module (21) comprises a collimating lens (211) and a connecting optical fiber (212): The collimating lens (211) is located at the receiving end of the laser altimeter and has a light transmittance greater than 99%, and is used to collimate the laser signal before transmitting it so that it is received by the receiving end of the laser altimeter; The connecting optical fiber (212) has a diameter that matches the collimating lens.

4. The comprehensive tester according to claim 1, characterized in that: The optical attenuator (12) is connected to the receiving coupling module (11) and is used to adjust the laser signal entering the laser altimeter comprehensive tester through the optical coupler, wherein the minimum value of the adjustment is greater than the maximum value of the optical power of the receiving coupling module, and the maximum value of the adjustment is jointly determined by the minimum value of the delay optical fiber (22), the insertion loss of each part when connected, and the coupling efficiency of the receiving coupling module (11).

5. The comprehensive tester according to claim 1, characterized in that: The optical switch (14) is connected to the optical attenuator (12) and is used to switch the received laser signal to the corresponding delay optical fiber (22). The number of the optical switch (14) is consistent with the number of the delay optical fiber (22), and the wavelength is consistent with the wavelength of the transmitted laser signal.

6. The comprehensive tester according to claim 1, characterized in that: The delay optical fiber (22) is connected to the optical switch (14) and is used to delay the laser signal received by the laser altimeter comprehensive tester. The number of the delay optical fiber (22) is consistent with the number of test points in the measurement range. The optical fiber length accuracy is less than the laser altimeter accuracy value. The length is calculated based on the laser altimeter measurement range, the propagation time of light in the corresponding space, the accuracy of the laser altimeter and the accuracy of the optical fiber length.

7. The comprehensive tester according to claim 1, characterized in that: The driving module (31) comprises an initialization module (311) and a driving circuit (312): The initialization module (311) is used to convert the test value of the laser altimeter into an input value of the laser altimeter comprehensive tester, and is set to n gears according to the measurement range of the laser altimeter, and each gear is set to m test points, and the interval between two adjacent test points is evenly set to ensure that the range from the initial test point to the final test point completely covers the measurement range of the laser height; The driving circuit (312) is used to receive the electrical signal generated by the initialization module (311), amplify the signal, drive the optical switch (14) to switch to the corresponding delay optical fiber (22), and drive the optical switch (14) to be turned off.

8. The comprehensive tester according to claim 1, characterized in that: The RS422 communication module (32) is connected to the laser altimeter and is used to perform full-duplex communication with the laser altimeter, that is, the RS422 communication module sends a self-test control status word, receives the laser altimeter self-test information, height measurement data information, data refresh rate, data delay time and whole machine power consumption replied by the laser altimeter, and decodes the received information into Chinese characters as "normal" or "fault" and sends it to the liquid crystal display screen (33).

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