An in-situ calibration system and method for a laser rangefinder

Abstract

The present invention discloses a method and system for in-situ calibration of a laser rangefinder, which relates to the field of laser technology. It is improved on the basis of existing detection and calibration equipment and consists of a host computer, a calibration host, and a multi-dimensional adjustment frame. The calibration host can measure the parameters of laser pulses, the time of transmission in the air, and the echo power reflected by the target to calibrate the maximum measurement range, minimum measurement range, and ranging accuracy of the laser rangefinder. This solution designs the calibration host into a device capable of multi-level alignment, and realizes the rapid alignment of the optical axis of the in-situ calibration system and the laser rangefinder under test through the cooperation of the calibration host and the multi-dimensional adjustment frame, solving the problem of in-situ online calibration of the laser rangefinder.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular, to a laser rangefinder in-situ calibration system and method. Background Art

[0002] Pulsed laser rangefinders have been widely used in various fields such as military, aerospace, surveying and mapping, and construction. During the use of a laser rangefinder, its performance may decline or even become unusable due to factors such as attenuation of the laser energy, drift of the optical axis, damage to components, and deterioration of the use environment. In order to ensure that the laser rangefinder is in good working condition, it is necessary to periodically calibrate the ranging range (maximum range and minimum range) and ranging accuracy of the laser rangefinder.

[0003] Most of the existing detection and calibration equipment tests and evaluates the performance of the laser ranging system in a laboratory. For a rangefinder that has been installed on a carrying platform, it must be disassembled and calibrated in a laboratory environment, which brings great inconvenience to the use and maintenance of the rangefinder. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing detection and calibration equipment requires the disassembling of the rangefinder installed on the carrying platform and calibration in a laboratory environment, which brings great inconvenience to the use and maintenance of the rangefinder. The purpose of the present invention is to provide a laser rangefinder in-situ calibration system and method. The calibration host has the functions of multi-level alignment and adjustable transmitting and receiving optical axes. Through the cooperation of the calibration host and the multi-dimensional adjustment frame, the rapid alignment of the optical axis of the in-situ calibration system and the measured laser rangefinder is achieved, and the problem of in-situ online calibration of the laser rangefinder is solved.

[0005] The present invention is achieved by the following technical solutions:

[0006] The present solution provides a laser rangefinder in-situ calibration system, including:

[0007] A calibration host, which is used to perform multi-level alignment of the optical axis after receiving the incident pulsed laser of the laser rangefinder to be measured, and send a return laser pulse to the laser rangefinder to be measured based on the incident pulsed laser;

[0008] The calibration host is further used to in-situ calibrate the maximum range, minimum range and ranging accuracy of the laser rangefinder to be measured based on the incident pulsed laser after multi-level alignment of the optical axis;

[0009] A multi-dimensional adjustment frame, which is used to adjust the attitude of the calibration host, and the calibration host is installed on the multi-dimensional adjustment frame;

[0010] An upper computer, which is used to interact with the calibration host to control the calibration host and its calibration work.

[0011] Working principle of this solution: Existing detection and calibration equipment for rangefinders already installed on the carrier platform must disassemble the rangefinder and calibrate it in a laboratory environment, which brings great inconvenience to the use and maintenance of the rangefinder. The in-situ calibration system for laser rangefinders provided by this solution improves the structure on the basis of existing detection and calibration equipment. It consists of a host computer, a calibration host, and a multi-dimensional adjustment frame. The calibration host measures the parameters of laser pulses, and simulates the time of laser ranging transmission in the air and the echo power of target reflection to calibrate the maximum range, minimum range, and ranging accuracy of the laser rangefinder. The calibration host provided by this solution has the functions of multi-level alignment and adjustable distance between the transmitting and receiving optical axes. Through the cooperation of the calibration host and the multi-dimensional adjustment frame, the optical axis of the in-situ calibration system and the measured laser rangefinder can be quickly aligned under field conditions, realizing on-line in-situ calibration, without disassembling the laser rangefinder to be measured, and solving the problem of in-situ on-line calibration of laser rangefinders.

[0012] A further optimized solution is that the calibration host includes:

[0013] A laser parameter measurement module, which is used to achieve multi-level alignment of the optical axis of the incident pulsed laser, and is also used to measure the basic parameters of the incident pulsed laser and transmit them to the host computer; the host computer sets the delay transmission time and echo laser signal based on the basic parameters of the incident pulsed laser and the system parameters of the measured laser rangefinder;

[0014] A delay module, which is used to delay the incident pulsed laser after multi-level alignment of the optical axis according to the delay transmission time;

[0015] An echo module, which is used to send an echo laser pulse to the laser rangefinder to be measured according to the echo laser signal.

[0016] A further optimized solution is that the laser parameter measurement module includes: a laser receiving window, a first beam splitter, a second beam splitter, an electro-optic attenuator, a third beam splitter, a fourth beam splitter, and a fifth beam splitter;

[0017] After the incident pulsed laser enters the laser parameter measurement module from the laser receiving window, it passes through the first beam splitter, the second beam splitter, the electro-optic attenuator, the third beam splitter, and the fourth beam splitter in sequence and then enters the delay module. Among them: the spectral information split by the first beam splitter enters the first visible light imaging component for imaging, the incident pulsed laser split by the second beam splitter enters the laser energy measurement component for energy measurement, and the incident pulsed laser split by the third beam splitter enters the quadrant detection component;

[0018] The reflecting mirror receives the reflected pulsed laser of the echo module, and converges with the incident pulsed laser split by the fourth beam splitter to the fifth beam splitter for merging. The pulsed laser output by the fifth beam splitter is imaged on the near-infrared CCD imaging component.

[0019] The incident laser pulse of the laser rangefinder to be measured enters through the laser receiving window and is received by the laser parameter measurement module; the first visible light imaging component is used to align with the emission optical axis of the laser rangefinder to be measured (first-level alignment); the laser energy measurement component is used to measure the laser pulse energy of the laser rangefinder to be measured; the quadrant detection component is used to further align with the emission optical axis of the laser rangefinder to be measured (second-level alignment); the near-infrared CCD imaging component is used to further align with the emission optical axis of the laser rangefinder to be measured (third-level alignment), and at the same time, the laser beam divergence angle of the laser rangefinder to be measured can be measured; the first beam splitter to the fifth beam splitter are used to split the incident laser; the electronic control attenuator is used to attenuate the energy of the incident laser pulse.

[0020] The alignment accuracy gradually increases during the first-level alignment, second-level alignment, and third-level alignment processes, realizing the rapid alignment of the calibration system and the optical axis of the laser rangefinder to be measured in the calibration host, achieving on-line in-situ calibration with high calibration efficiency.

[0021] A further optimized solution is that the delay module includes: a focusing lens, an APD detector, and a delay circuit;

[0022] The incident pulsed laser entering the delay module is focused on the focusing lens and then enters the APD detector for measurement. The delay circuit triggers the echo module after the delay transmission time.

[0023] The focusing lens focuses the laser split by the laser parameter measurement module onto the focal plane of the APD detector, and then the APD detector converts the optical signal into a trigger pulse signal to start the delay circuit. The delay circuit delays for a corresponding time according to the simulated distance set by the host computer, and outputs an electrical pulse signal after the delay ends.

[0024] A further optimized solution is that the echo module includes: a laser emission component, an electronic control fiber optic attenuator, a reflective collimator, a sixth beam splitter, a seventh beam splitter, and a second visible light imaging component;

[0025] The echo laser pulse emitted by the laser emission component passes through the electronic control fiber optic attenuator, the reflective collimator, the sixth beam splitter, and the seventh beam splitter in sequence and then emits from the laser emission window to the laser rangefinder to be measured. Among them, the echo laser pulse split by the sixth beam splitter enters the reflector, and the spectral information split by the seventh beam splitter enters the second visible light imaging component for imaging.

[0026] The laser emission component consists of a 1064nm fiber laser, a 1540nm fiber laser, a 1570nm fiber laser, and a 650nm fiber laser. Among them, the 1064nm fiber laser, 1540nm fiber laser, and 1570nm fiber laser are lasers with working wavelengths. The host computer can control the laser component to output echo pulses with the same wavelength, the same pulse width, and the same repetition frequency according to the laser pulse parameters of the laser rangefinder to be measured. The 650nm fiber laser is used as an indicating wavelength laser; the electrically controlled fiber optic attenuator adjusts the laser power output by the laser component according to the echo power set by the host computer; the reflective collimator is used to collimate the laser emitted by the laser component; the sixth beam splitter is mainly used to split the laser emitted by the laser component, and enters the near-infrared CCD imaging component through the mirror and the fourth beam splitter in the laser parameter measurement module, which is used for the calibration of the consistency of the light emission and reception optical axes of the system itself;

[0027] A further optimized solution is that the echo module further includes an electric translation guide rail, which is used to adjust the distance between the light emission and reception optical axes of the calibration host.

[0028] The seventh beam splitter is used to reflect the image of the receiving window of the laser rangefinder to be measured to the second visible light imaging component; the reflective collimator, the sixth beam splitter, the seventh beam splitter, and the second visible light imaging component are all placed on the electric translation guide rail and can be translated as a whole according to the instructions issued by the host computer, so as to adjust the distance between the laser emission and reception optical axes, and cooperate with the four-dimensional adjustment frame to achieve alignment with the receiving optical axis of the laser rangefinder to be measured; the laser echo pulse is emitted through the laser emission window and received by the laser rangefinder to be measured, and the length of the laser emission window is not less than the stroke of the electric translation guide rail.

[0029] This solution also provides a method for in-situ calibration of a laser rangefinder, which is implemented based on the laser rangefinder in-situ calibration system described in the above solution, including:

[0030] Step 1, obtain the basic parameters of the laser rangefinder to be measured, and build a laser rangefinder in-situ calibration system;

[0031] Step 2, according to the wavelength of the laser rangefinder to be measured, the host computer issues an instruction to trigger the laser emission component to emit pulsed laser with the same wavelength. The pulsed laser emitted by the laser emission component enters the near-infrared CCD imaging component through the sixth beam splitter, the mirror and the fifth beam splitter for imaging, and records the coordinate points (x 0 , y 0 ) of the centroid of the pulsed laser spot on the near-infrared CCD target surface at this time;

[0032] Step 3: Image the transmitting window and receiving window of the laser rangefinder under test through the first visible light imaging component and the second visible light imaging component respectively, and at the same time adjust the position of the calibration host so that the geometric centers of the transmitting window and receiving window of the laser rangefinder under test coincide with the field-of-view centers of the first visible light imaging component and the second visible light imaging component respectively;

[0033] The laser rangefinder under test emits laser pulses, and introduces the laser pulses of the laser rangefinder under test into the field of view of the quadrant detection component; by observing the position of the laser pulse spot of the laser rangefinder under test on the target surface of the quadrant detector, finely adjust the three-dimensional adjustment frame so that the laser pulses of the laser rangefinder under test are incident on the near-infrared CCD imaging component; by observing the position of the laser pulse spot of the laser rangefinder under test on the near-infrared CCD target surface, finely adjust the four-dimensional adjustment frame again so that the centroid coordinates of the laser pulse spot of the laser rangefinder under test coincide with the coordinate point (x 0 , y 0 );

[0034] Step 4: Calibrate the maximum range, minimum range and ranging accuracy of the laser rangefinder under test.

[0035] The further optimized solution is that the calibration method for the maximum range includes the steps of:

[0036] Step a1: The upper computer configures the working wavelength of the calibration host and sets the simulated distance to the maximum range;

[0037] Step a2: After the laser parameter measurement module receives the incident laser pulses of the laser rangefinder under test, measure the average power P a , pulse width ω and repetition frequency f of the incident laser pulses, and calculate the peak power P p = P a / (fω), and calculate the attenuation magnification M p between the ranging pulse power and the peak power P output by the echo laser according to the formula; l ; 2

[0038] Step a3: Adjust the electro-optic fiber attenuator to the state of maximum attenuation magnification;

[0039] Step a4: The laser rangefinder under test emits ranging pulses, which trigger the delay module to start delaying after passing through the laser parameter measurement module. After the delay ends, trigger the echo module to emit echo laser pulses, and check whether the laser rangefinder under test reaches the critical stable ranging state at this time;

[0040] Step a5: If the laser rangefinder under test does not reach the critical stable ranging state, gradually reduce the attenuation ratio of the electro-controlled optical fiber attenuator and repeat step a4; if the laser rangefinder under test reaches the critical stable ranging state, record the attenuation ratio M of the electro-controlled optical fiber attenuator at this time 3 ;

[0041] Step a6: Calculate the measured extinction ratio S of the laser rangefinder under test at the maximum range real = 10lg{M 1 M 2 M 3 M 4}, where M 1 is the fixed attenuation rate ratio of the receiving system of the in-situ calibrator; M 4 is the fixed attenuation ratio of the transmitting system of the in-situ calibrator

[0042] A further optimized solution is that the calibration method for the minimum range includes:

[0043] Step b1: The upper computer configures the working wavelength of the calibration host and sets the simulated distance to the minimum range

[0044] Step b2: The laser rangefinder under test emits a ranging pulse. After passing through the laser parameter measurement module, it triggers the delay module to start delaying. After the delay ends, it triggers the echo module to emit an echo laser pulse

[0045] Step b3: Adjust the attenuation ratio of the electro-controlled optical fiber attenuator so that the laser rangefinder under test can receive the echo laser pulse

[0046] Step b4: Calculate the error rate, omission rate, and accurate measurement rate of the laser rangefinder under test

[0047] When the error rate ≤ the error threshold, the omission rate ≤ the omission threshold, and the accurate measurement rate ≥ the accurate measurement threshold, it is determined that the minimum range of the laser rangefinder under test is qualified

[0048] A further optimized solution is that the calibration method for the ranging accuracy includes:

[0049] Step c1: The upper computer configures the working wavelength of the calibration host and sets the simulated distance to the standard distance L

[0050] Step c2: The laser rangefinder under test emits a ranging pulse. After passing through the laser parameter measurement module, it triggers the delay module to start delaying. After the delay ends, it triggers the echo module to emit an echo laser pulse

[0051] Step c3: Adjust the attenuation ratio of the electro-controlled optical fiber attenuator so that the laser rangefinder under test can receive the echo laser pulse

[0052] Step c4, calculate the ranging compliance rate, echo rate, and ranging accuracy of the laser rangefinder under test. When the compliance rate and echo rate meet the specified thresholds, it is determined that the ranging accuracy of the laser rangefinder to be tested is qualified.

[0053] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0054] A laser rangefinder in-situ calibration system and method provided by the present invention are improved on the basis of existing detection and calibration equipment, and consist of a host computer, a calibration host, and a multi-dimensional adjustment frame. The calibration host can measure the parameters of laser pulses, and the calibration host simulates the time of transmission of ranging laser in the air and the echo power of target reflection to calibrate the maximum range, minimum range, and ranging accuracy of the laser rangefinder. This solution endows the calibration host with the functions of multi-level alignment and adjustable transmitting and receiving optical axes. Through the cooperation of the calibration host and the multi-dimensional adjustment frame, the rapid alignment of the optical axis of the in-situ calibration system and the laser rangefinder under test is realized, solving the problem of in-situ online calibration of the laser rangefinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0056] Figure 1 is a schematic structural diagram of a laser rangefinder in-situ calibration system;

[0057] Figure 2 is a schematic diagram of the detection principle of the maximum range;

[0058] Figure 3 is a schematic diagram of the detection principle of the maximum range in the real environment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] To make the purpose, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the embodiments and the drawings. The illustrative embodiments and descriptions thereof of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0060] Embodiment 1

[0061] This embodiment provides a laser rangefinder in-situ calibration system, as Figure 1 shown, including:

[0062] A calibration host, which is used to perform multi-level optical axis alignment after receiving the incident pulsed laser of the laser rangefinder to be tested, and send a return laser pulse to the laser rangefinder to be tested based on the incident pulsed laser;

[0063] The calibration host is also used to in-situ calibrate the maximum measurement range, minimum measurement range and ranging accuracy of the laser rangefinder to be tested based on the incident pulsed laser after multi-level optical axis alignment;

[0064] A multi-dimensional adjustment frame, which is used to adjust the posture of the calibration host, and the calibration host is installed on the multi-dimensional adjustment frame; in this embodiment, the multi-dimensional adjustment frame is a four-dimensional adjustment frame with four-dimensional adjustment of azimuth, pitch, roll and height, mainly used to realize the alignment of the receiving and emitting optical axes of the calibration host and the measured laser rangefinder.

[0065] A host computer, which is used to interact with the calibration host to control the calibration host and its calibration work.

[0066] The calibration host includes:

[0067] A laser parameter measurement module, which is used to perform multi-level optical axis alignment of the incident pulsed laser, and is also used to measure the basic parameters of the incident pulsed laser and transmit them to the host computer; the host computer sets the delay transmission time and the return laser signal based on the basic parameters of the incident pulsed laser;

[0068] A delay module, which is used to delay the incident pulsed laser after multi-level optical axis alignment according to the delay transmission time;

[0069] A return wave module, which is used to send a return laser pulse to the laser rangefinder to be tested according to the return laser signal.

[0070] The laser parameter measurement module includes: a laser receiving window, a first beam splitter, a second beam splitter, an electro-optic attenuator, a third beam splitter, a fourth beam splitter, and a fifth beam splitter;

[0071] After the incident pulsed laser enters the laser parameter measurement module from the laser receiving window, it passes through the first beam splitter, the second beam splitter, the electro-optic attenuator, the third beam splitter and the fourth beam splitter in sequence and then enters the delay module, where: the spectral information split by the first beam splitter enters the first visible light imaging component for imaging, the incident pulsed laser split by the second beam splitter enters the laser energy measurement component for energy measurement, and the incident pulsed laser split by the third beam splitter enters the quadrant detection component;

[0072] The reflecting mirror receives the reflected pulsed laser of the return wave module, and converges with the incident pulsed laser split by the fourth beam splitter to the fifth beam splitter for combination, and the pulsed laser output by the fifth beam splitter is imaged on the near-infrared CCD imaging component.

[0073] The delay module includes: a focusing lens, an APD detector and a delay circuit;

[0074] The incident pulse laser entering the delay module is focused on the focusing lens and then enters the APD detector for measurement. The delay circuit triggers the echo module after the delayed transmission time.

[0075] The echo module includes: a laser emission component, an electrically controlled optical fiber attenuator, a reflective collimator, a sixth beam splitter, a seventh beam splitter, and a second visible light imaging component;

[0076] The echo laser pulse emitted by the laser emitting component passes through the electrically-controlled optical fiber attenuator, the reflective collimator, the sixth beam splitter and the seventh beam splitter in sequence, and is emitted from the laser emitting window to the laser rangefinder to be measured. The echo laser pulse separated by the sixth beam splitter enters the reflector, and the spectral information separated by the seventh beam splitter enters the second visible light imaging component for imaging.

[0077] The echo module also includes an electric translation guide rail for adjusting the spacing between the receiving and emitting light axes of the calibration host.

[0078] Example 2

[0079] This embodiment provides a laser rangefinder in-situ calibration method, which is implemented based on the laser rangefinder in-situ calibration system described in the previous embodiment, and includes:

[0080] Step 1: Obtain the basic parameters of the laser rangefinder to be tested and build an in-situ calibration system for the laser rangefinder;

[0081] Step 2: According to the wavelength of the laser rangefinder to be measured, the host computer sends a command to trigger the laser emitting component to emit a pulsed laser of the same wavelength. The pulsed laser emitted by the laser emitting component passes through the sixth beam splitter, the reflector and the fifth beam splitter and enters the near-infrared CCD imaging component for imaging. The coordinate point (x 0 ,y 0 );

[0082] Step 3, imaging the transmitting window and receiving window of the laser rangefinder to be measured respectively through the first visible light imaging component and the second visible light imaging component, and adjusting the posture of the calibration host at the same time, so that the geometric centers of the transmitting window and the receiving window of the laser rangefinder to be measured coincide with the fields of view centers of the first visible light imaging component and the second visible light imaging component respectively;

[0083] The attitude of the calibration host is further adjusted to introduce the incident laser pulse into the field of view of the four-quadrant detection assembly;

[0084] Then further adjust the posture of the calibration host so that the incident laser pulse enters the near-infrared CCD imaging component and the centroid coordinates of the incident laser pulse spot are consistent with the coordinate point (x 0 ,y 0 )coincide;

[0085] Step 4: Calibrate the maximum measurement range, minimum measurement range, and ranging accuracy of the laser rangefinder under test.

[0086] As Figure 2 and Figure 3 shown, where Figure 2 and Figure 3 respectively represent the maximum measurement range detection state of the in-situ calibration host (in-situ calibration system in the figure) and the true detection state of the maximum measurement range of the laser rangefinder. Among them, P t is the output optical power of the laser rangefinder laser, P r is the received echo power of the laser rangefinder, K t and K r are the system transmittances of the laser rangefinder for transmission and reception respectively, L 1 and L max are the working distance of the in-situ calibrator in the in-situ calibration system and the maximum measurement range of the laser rangefinder respectively, M 1 is the fixed attenuation rate magnification of the in-situ calibrator reception system (factory calibration), M 2 is the attenuation magnification between the ranging pulse power measured by the laser energy meter and the peak power P l (factory calibration) output by the echo laser, M 3 is the adjustable attenuation magnification of the fiber optic attenuator; M 4 is the fixed attenuation magnification of the in-situ calibrator transmission system (factory calibration).

[0087] Figure 2 and Figure 3 In two cases, when the laser rangefinder is in the critical working state, the received optical powers are P r,1 and P r,2 respectively, then the detection threshold of the laser rangefinder can be expressed as:

[0088] P o = P r,1 G max = P r,2 G(L max ) (1)

[0089] According to the test principles of the two states, it can be obtained that:

[0090] P r,1 = P t K t K r exp(-2α 1 L 1 )(M 1 M 2 M 3 M 4 ) -1(2)

[0091]

[0092] Substituting equations (2) and (3) into equation (1) gives

[0093]

[0094] Then the theoretical extinction ratio of the laser rangefinder at the maximum range is:

[0095]

[0096] where the F(θ) correction factor is as follows:

[0097]

[0098] In the formula: L 1 represents the total atmospheric distance from the laser rangefinder to the maximum range detection device, with the unit of meter (m); x L am represents the maximum range of the laser rangefinder, with the unit of meter (m); ρ represents the diffuse reflection coefficient of the tactical target; θ t represents the beam divergence angle, with the unit of radian (rad); θ r represents the receiving field of view angle, with the unit of radian (rad); α represents the atmospheric attenuation coefficient specified by the tactical and technical indicators. For a 1.06um wavelength laser, it can be approximately calculated as α = 2.7 / V. For a 1.54um or 1.57um wavelength laser, it can be approximately calculated as α = 2.14 / V; α 1 represents the atmospheric attenuation coefficient during the maximum range test. For a 1.06um wavelength laser, it can be approximately calculated as α = 2.7 / V. For a 1.54um or 1.57um wavelength laser, it can be approximately calculated as α = 2.14 / V; A represents the actually measured target area specified by the tactical and technical indicators, with the unit of square meter (㎡); A r represents the receiving field of view area of the laser rangefinder, with the unit of square meter (㎡); V represents the visibility specified by the tactical and technical indicators; V 1 represents the visibility during the maximum range test; S represents the extinction ratio of the laser rangefinder at the maximum range; G(L max ) represents the gain of the receiving amplifier at the distance L max ; G max represents the maximum gain of the receiving amplifier.

[0099] The calibration method for the maximum range includes the steps:

[0100] Step a1, the upper computer configures the working wavelength of the calibration host and sets the simulated distance to the maximum range;

[0101] Step a2, after the laser parameter measurement module receives the incident laser pulse of the laser rangefinder to be measured, it measures the average power P of the incident laser pulse a , pulse width ω and repetition frequency f, and calculates the peak power P p = P a / (fω), and calculates the attenuation magnification M p between the ranging pulse power and the peak power P output by the echo laser according to the formula l ; 2

[0102] Step a3, adjust the electro-optic fiber attenuator to the state of maximum attenuation magnification;

[0103] Step a4, the laser rangefinder to be measured emits a ranging pulse, which triggers the delay module to start delaying after passing through the laser parameter measurement module. After the delay ends, it triggers the echo module to emit an echo laser pulse, and check whether the laser rangefinder to be measured reaches the critical stable ranging state at this time;

[0104] Step a5, if the laser rangefinder to be measured does not reach the critical stable ranging state, gradually reduce the attenuation magnification of the electro-optic fiber attenuator and repeat step a4; if the laser rangefinder to be measured reaches the critical stable ranging state, record the attenuation magnification M 3 of the electro-optic fiber attenuator at this time;

[0105] Step a6, calculate the measured extinction ratio S real = 10lg{M 1 M 2 M 3 M 4}, where M 1 is the fixed attenuation rate magnification of the in-situ calibrator receiving system; M 4 is the fixed attenuation magnification of the in-situ calibrator transmitting system.

[0106] Calculate the theoretical extinction ratio S of the measured laser rangefinder, and then compare and judge it with the extinction ratio S real measured by the system for the laser rangefinder to be measured, judge the ratio of S and S real , when S / S real ≥ 1, the maximum ranging distance of the measured laser rangefinder meets the index requirements, and when S / S real < 1, the maximum ranging distance of the measured laser rangefinder does not meet the index requirements.

[0107] The calibration method for the minimum ranging distance includes:

[0108] Step b1, the upper computer configures the working wavelength of the calibration host and sets the simulated distance to the minimum ranging distance;

[0109] ​Step b2: The laser rangefinder under test emits a ranging pulse. After passing through the laser parameter measurement module, it triggers the delay module to start timing. After the timing ends, it triggers the echo module to emit an echo laser pulse.

[0110] Step b3: Adjust the attenuation ratio of the electro-control fiber optic attenuator so that the laser rangefinder under test can receive the echo laser pulse.

[0111] Step b4: Calculate the error rate, omission rate, and accurate measurement rate of the laser rangefinder under test.

[0112] When the error rate ≤ error threshold, the omission rate ≤ omission threshold, and the accurate measurement rate ≥ accurate measurement threshold, it is determined that the minimum ranging distance of the laser rangefinder under test is qualified.

[0113] The formula for the error rate P C is: In the formula, N C is the number of error times, and N is the total number of effective ranging times.

[0114] The formula for the omission rate P L is: In the formula, N L is the number of omission times.

[0115] The formula for the accurate measurement rate P Z is: In the formula, N Z is the number of ranging times with an error not greater than the specified allowable value.

[0116] The calibration method for ranging accuracy includes:

[0117] Step c1: The host computer configures the working wavelength of the calibration host and sets the simulated distance to the standard distance L.

[0118] Step c2: The laser rangefinder under test emits a ranging pulse. After passing through the laser parameter measurement module, it triggers the delay module to start timing. After the timing ends, it triggers the echo module to emit an echo laser pulse.

[0119] Step c3: Adjust the attenuation ratio of the electro-control fiber optic attenuator so that the laser rangefinder under test can receive the echo laser pulse.

[0120] Step c4: Calculate the accurate measurement rate, echo rate, and ranging accuracy of the laser rangefinder under test. When the accurate measurement rate and echo rate meet the specified thresholds, it is determined that the ranging accuracy of the laser rangefinder under test is qualified.

[0121] The formula for the error rate P C is: In the formula, N C is the number of error times, and N is the total number of effective ranging times.

[0122] The formula for the omission rate P LCalculation formula: In the formula, N L is the number of missing counts;

[0123] The criterion rate P Z Calculation formula: In the formula, N Z is the number of ranging measurements with an error not greater than the specified allowable value.

[0124] This embodiment is based on a three - level imaging alignment method and is combined with a four - dimensional adjustment frame, which can quickly align with the optical axis of the laser rangefinder under field conditions, achieving in - line in - situ calibration with high calibration efficiency; it integrates the function of laser parameter measurement and can in - situ online detect important parameters such as the pulse energy, pulse width, pulse repetition frequency, and beam divergence angle of the measured laser rangefinder, improving the calibration accuracy and reliability; it uses the photoelectric conversion delay method to simulate the time for the ranging laser pulse to transmit in the air, with advantages such as high distance simulation accuracy and strong anti - interference ability; it has the calibration function for laser rangefinders with different wavelengths (1064nm, 1540nm, 1570nm) and different transceiver spacings (the spacing between the transmitting optical axis and the receiving optical axis).

[0125] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above - mentioned are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A laser rangefinder in-situ calibration system, characterized in that, it includes: A calibration host, which is used to perform multi-level optical axis alignment after receiving the incident pulsed laser of the laser rangefinder to be measured, and send a return pulsed laser to the laser rangefinder to be measured based on the incident pulsed laser; The calibration host is also used to in-situ calibrate the maximum range, minimum range and ranging accuracy of the laser rangefinder to be measured based on the incident pulsed laser after multi-level optical axis alignment; A multi-dimensional adjustment frame, which is used to adjust the attitude of the calibration host, and the calibration host is installed on the multi-dimensional adjustment frame; A host computer, which is used to interact with the calibration host to control the calibration host and its calibration work; The calibration host includes: A laser parameter measurement module, which is used to perform multi-level optical axis alignment of the incident pulsed laser, measure the basic parameters of the incident pulsed laser and transmit them to the host computer; the host computer sets the delay transmission time and the return laser signal based on the basic parameters of the incident pulsed laser and the system parameters of the laser rangefinder to be measured; A delay module, which is used to delay the incident pulsed laser after multi-level optical axis alignment according to the delay transmission time; A return wave module, which is used to send a return pulsed laser to the laser rangefinder to be measured according to the return laser signal; The laser parameter measurement module includes: a laser receiving window, a first beam splitter, a second beam splitter, an electro-optic attenuator, a third beam splitter, a fourth beam splitter and a fifth beam splitter; The incident pulsed laser passes through the laser receiving window, the first beam splitter, the second beam splitter, the electro-optic attenuator, the third beam splitter and the fourth beam splitter in sequence and then enters the delay module, where: the spectral information split by the first beam splitter enters the first visible light imaging component for imaging, the incident pulsed laser split by the second beam splitter enters the laser energy measurement component for energy measurement, and the incident pulsed laser split by the third beam splitter enters the quadrant detection component; The reflecting mirror receives the reflected pulsed laser of the return wave module, and converges with the incident pulsed laser split by the fourth beam splitter to the fifth beam splitter for combination, and the pulsed laser output by the fifth beam splitter is imaged on the near-infrared CCD imaging component; The delay module includes: a focusing lens, an APD detector and a delay circuit; The incident pulsed laser from the laser parameter measurement module is focused on the focusing lens and then enters the APD detector for measurement, and the delay circuit triggers the return wave module after the delay transmission time; The return wave module includes: a laser emission component, an electro-optic fiber attenuator, a reflective collimator, a sixth beam splitter, a seventh beam splitter and a second visible light imaging component; The return pulsed laser emitted by the laser emission component passes through the electro-optic fiber attenuator, the reflective collimator, the sixth beam splitter and the seventh beam splitter in sequence and then is sent from the laser emission window to the laser rangefinder to be measured, where: the return pulsed laser split by the sixth beam splitter enters the reflecting mirror, and the spectral information split by the seventh beam splitter enters the second visible light imaging component for imaging.

2. The laser rangefinder in-situ calibration system according to claim 1, characterized in that, The return wave module further includes an electric translation guide rail, which is used to adjust the distance between the light emission and reception optical axes of the calibration host.

3. A laser rangefinder in-situ calibration method, characterized in that, Implementation of the in-situ calibration system for a laser rangefinder according to claim 1 or 2, comprising: Step 1: Obtain the basic parameters of the laser rangefinder to be measured and build an in-situ calibration system for the laser rangefinder; Step 2: Configure the working wavelength of the calibration host, send a command to trigger the laser emission component to emit pulsed laser of the same wavelength, and the pulsed laser emitted by the laser emission component is incident on the near-infrared CCD imaging component through the sixth beam splitter, the reflector and the fifth beam splitter for imaging. Record the coordinate points (x 0 , y 0 ) of the centroid of the pulsed laser spot on the near-infrared CCD target surface at this time; Step 3: Image the emission window and the reception window of the laser rangefinder to be measured through the first visible light imaging component and the second visible light imaging component respectively, and at the same time adjust the attitude of the calibration host so that the geometric centers of the emission window and the reception window of the laser rangefinder to be measured coincide with the field-of-view centers of the first visible light imaging component and the second visible light imaging component respectively; Further adjust the attitude of the calibration host to introduce the incident laser pulse into the field of view of the quadrant detection component; Further adjust the attitude of the calibration host so that the incident laser pulse enters the near-infrared CCD imaging component and the centroid coordinates of the incident laser pulse spot coincide with the coordinate points (x 0 , y 0 ); Step 4: Calibrate the maximum range, minimum range and ranging accuracy of the laser rangefinder to be measured.

4. An in-situ calibration method for a laser rangefinder according to claim 3, characterized in that the calibration method for the maximum range in Step 4 includes the following steps: Step a1: Configure the working wavelength of the calibration host and set the simulated distance of the calibration host to the maximum range; Step a2: After the laser parameter measurement module receives the incident laser pulse of the laser rangefinder to be measured, it measures the average power P of the incident laser pulse a , pulse width ω, and repetition frequency. From the formula P p = P a / (ωf), the peak power P p is calculated. According to the formula M 2 = P p / P l , the attenuation magnification M l between the ranging pulse power and the peak power P 2 of the echo laser output is calculated; Step a3: Adjust the electro-control fiber optic attenuator to the state of maximum attenuation ratio; Step a4: The laser rangefinder to be measured emits a ranging pulse. After passing through the laser parameter measurement module, it triggers the delay module to start delaying. After the delay ends, it triggers the echo module to emit an echo laser pulse. Check whether the laser rangefinder to be measured reaches the critical stable ranging state at this time; Step a5, if the laser rangefinder under test does not reach the critical stable ranging state, gradually reduce the attenuation ratio of the electro-control fiber optic attenuator, and repeat step a4; if the laser rangefinder under test reaches the critical stable ranging state, record the attenuation ratio M of the electro-control fiber optic attenuator at this time 3 ; Step a6: Calculate the measured extinction ratio when the laser rangefinder to be measured reaches the maximum range ， Among them, M 1 is the fixed attenuation rate magnification of the in-situ calibrator receiving system; M 4 is the fixed attenuation magnification of the in-situ calibrator transmitting system.

5. An in-situ calibration method for a laser rangefinder according to claim 3, characterized in that the calibration method for the minimum range includes: Step b1: Configure the working wavelength of the calibration host and set the simulated distance of the calibration host to the minimum range; Step b2: The laser rangefinder to be measured emits a ranging pulse. After passing through the laser parameter measurement module, it triggers the delay module to start delaying. After the delay ends, it triggers the echo module to emit an echo laser pulse; Step b3: Adjust the attenuation ratio of the electro-control fiber optic attenuator so that the laser rangefinder to be measured can receive the echo laser pulse; Step b4: Calculate the error rate, omission rate and accurate measurement rate of the laser rangefinder to be measured for ranging; When the error rate ≤ the error threshold, the omission rate ≤ the omission threshold and the accurate measurement rate ≥ the accurate measurement threshold, it is determined that the minimum range of the laser rangefinder to be measured is qualified.

6. An in-situ calibration method for a laser rangefinder according to claim 3, characterized in that the calibration method for the ranging accuracy includes: Step c1: Configure the working wavelength of the calibration host and set the simulated distance of the calibration host to the standard distance; Step c2: The laser rangefinder to be measured emits a ranging pulse. After passing through the laser parameter measurement module, it triggers the delay module to start delaying. After the delay ends, it triggers the echo module to emit an echo laser pulse; Step c3: Adjust the attenuation ratio of the electro-control fiber optic attenuator so that the laser rangefinder to be measured can receive the echo laser pulse; Step c4: Calculate the accurate measurement rate, echo rate and ranging accuracy of the laser rangefinder to be measured for ranging. When the accurate measurement rate and the echo rate meet the specified thresholds, it is determined that the ranging accuracy of the laser rangefinder to be measured is qualified.

Images