Laser seeker calibration test equipment and calibration test methods

Abstract

This invention belongs to the field of laser seeker testing, specifically relating to a laser seeker calibration and testing device and method. It includes a control computer, a simulated target, a three-axis turntable, and a laser seeker to be calibrated. The simulated target outputs uniformly collimated laser beams of different powers and divergence angles. The three-axis turntable has rotational degrees of freedom in yaw, pitch, and roll. The laser seeker to be calibrated is mounted on the three-axis turntable, with its entrance pupil center coinciding with the central axis of the simulated target. This invention increases the calibration dataset for the laser seeker under different operating conditions, effectively improving the accuracy of the laser seeker's line-of-sight angle calculation; effectively eliminating the seeker's zero-position deviation; and effectively improving the calibration and testing efficiency of the laser seeker.

Description

Technical Field

[0001] This invention belongs to the field of laser seeker testing, specifically relating to a laser seeker calibration testing device and calibration testing method. Background Technology

[0002] A laser seeker is a common weapon system used in terminal guidance. It receives laser signals from the target and calculates the line-of-sight angle (LAS) between the seeker and the target. The laser seeker consists of optical components, a four-quadrant detector, and signal processing components. Changes in the LAS cause a relative displacement of the image formed on the target surface of the four-quadrant detector by the optical components. The four-quadrant detector divides the imaged spot into four parts, thus allowing the determination of the energy percentage of the imaged spot along the yaw or pitch axis, which is linearly related to the yaw or pitch angle. Calibration tests establish a one-to-one mapping between the energy percentage and the LAS, ensuring the seeker outputs accurate LAS information during actual use. The calibration test process is crucial, directly affecting the guidance accuracy of the laser seeker.

[0003] Existing calibration and testing methods often only perform two-axis calibration (yaw and pitch), resulting in limited calibration datasets and large errors in the off-axis line-of-sight angles. To address this issue, Chen Qinggui of the China Air-to-Air Missile Research Institute proposed a refined gridded calibration method in his paper "Research on Gridded Calibration of a Certain Type of Strapdown Laser Seeker," published in *Henan Science and Technology*, 2022. This method increases the calibration dataset by 10 times and effectively improves the accuracy of off-axis line-of-sight angle calculations. However, this method has several shortcomings: First, the increased dataset size leads to longer calibration testing times. Second, the dynamic range of laser energy during terminal guidance spans 50-60 dB, causing the axial energy ratio output by the laser seeker to vary under different laser energy conditions at the same line-of-sight angle. This results in discrepancies in the line-of-sight angle calculated using a single calibration dataset, leading to decreased angle accuracy. Third, the beam divergence angle of the target spot relative to the seeker constantly changes during terminal guidance, causing the imaging spot to change accordingly. This also results in varying axial energy ratios output by the laser seeker at different distances, leading to discrepancies in the line-of-sight angle calculated using a single calibration dataset, further reducing angle accuracy. Expanding the calibration dataset is necessary to improve angle calculation accuracy; however, this significantly increases calibration testing time and consumes considerable manpower and resources. Summary of the Invention

[0004] The purpose of this invention is to provide a laser seeker calibration and testing device and a calibration and testing method to effectively perform laser seeker calibration and testing.

[0005] The technical solution to achieve the purpose of this invention is: a laser seeker calibration and testing device, comprising a control computer, a simulated target, a three-axis turntable, and a laser seeker to be calibrated and tested;

[0006] The simulated target is used to output uniformly collimated laser beams with different laser powers and divergence angles. The three-axis turntable has rotational degrees of freedom in three directions: yaw, pitch, and roll. The laser seeker to be calibrated is mounted on the three-axis turntable, and the entrance pupil center of the laser seeker to be calibrated coincides with the central axis of the simulated target.

[0007] The control computer controls the simulated target to output a uniformly collimated laser beam with a set power and divergence angle. The control computer also controls a three-axis turntable to rotate around three rotation axes: yaw, pitch, and roll, and to move according to a predetermined calibration grid. The turntable stops at each calibration grid point to allow the control computer to collect data output from the laser seeker to be calibrated. The laser power and divergence angle output by the simulated target are calculated based on the set target distance. The laser power and divergence angle are changed, and the seeker data acquisition process is repeated to obtain multiple sets of calibration datasets at different target distances.

[0008] Furthermore, the simulated target includes, in sequence, a laser, an electrically adjustable optical attenuator, an optical homogenizer, an electrically adjustable aperture, an optical beam splitter, a beam expander and collimating lens group, and an optical power meter.

[0009] The laser, electrically adjustable optical attenuator, electrically adjustable aperture, optical power meter, and control computer are connected. The laser power and beam divergence angle of the laser beam are adjusted by the electrically adjustable optical attenuator and electrically adjustable aperture to simulate different target distances. The optical homogenizer is used to shape the originally Gaussian distributed light spot into a uniformly distributed light spot to simulate the light spot energy distribution of the diffuse reflection light from the target. After the laser passes through the optical beam splitter, part of the light enters the beam expanding and collimating lens group to form a simulated light spot, and part of the light enters the optical power meter to monitor the laser power.

[0010] Furthermore, the laser is a fiber laser, capable of generating pulsed lasers with instantaneous power exceeding 1kW, pulse width adjustable between 5ns and 20ns, and pulse repetition frequency adjustable between 1Hz and 100Hz.

[0011] Furthermore, the electrically adjustable optical attenuator includes an optical fiber and a mechanical adjustment structure. The coupling degree between the end faces of the incident and output optical fibers is controlled by the mechanical adjustment structure, so as to achieve a continuously adjustable attenuation ratio in the range of 0~60dB.

[0012] Furthermore, by connecting two electrically adjustable optical attenuators in series, a higher attenuation ratio can be achieved for the output.

[0013] Furthermore, the three-axis rotary table includes a yaw rotary table, a pitch rotary table, a roll rotary table, and adapter components.

[0014] The yaw turntable rotates around the y-axis to simulate the motion of the laser seeker in the yaw direction, the pitch turntable rotates around the z-axis to simulate the motion of the laser seeker in the pitch direction, and the roll turntable rotates around the x-axis to eliminate zero-position deviation. The roll turntable is mounted on the pitch turntable, the pitch turntable is mounted on the yaw turntable, and the laser seeker to be calibrated and tested is mounted on the roll turntable through an adapter. The rotation axes of the three turntables intersect perpendicularly in pairs, forming a spatial rectangular coordinate system.

[0015] A method for calibrating and testing a laser seeker based on the above-mentioned calibration and testing equipment includes the following steps:

[0016] Step (1): Find the zero position;

[0017] Step (2): Divide the calibration grid;

[0018] Step (3): Calculate the laser power and beam divergence angle based on the set target distance, and set the parameters of the electrically adjustable optical attenuator and the aperture of the electrically adjustable aperture based on the calculation results;

[0019] Step (4): Control the yaw and pitch turntables to rotate in a zigzag scanning pattern, pause when passing the calibration point, and collect the output coefficient value of the seeker at the calibration point;

[0020] Step (5): Move according to the calibration grid trajectory in step (2), repeat step (4) until the calibration grid has been traversed;

[0021] Step (6): Change the target distance and repeat steps (3)-(5) until the target distance is traversed.

[0022] Furthermore, step (1) specifically involves:

[0023] First, control the turntable to rotate while reading the yaw energy ratio and pitch energy ratio output by the laser seeker to be calibrated, until both are 0.

[0024] Subsequently, only the yaw turntable is controlled to rotate, with the rotation angle being the maximum detectable angle of the laser seeker. At the same time, the pitch energy percentage output by the laser seeker is read. If it is not 0, the roll turntable is rotated until the pitch energy percentage is 0.

[0025] Control the rotation of the yaw turntable to bring the yaw energy percentage back to 0.

[0026] Further, step (2) specifically involves dividing the yaw and pitch angles into 21 parts to form a 21×21 calibration grid, totaling 441 calibration points.

[0027] Furthermore, in step (3), the laser power P is calculated according to the following formula:

[0028] ,

[0029] Where k is the scaling factor and R is the target distance;

[0030] The beam divergence angle α is calculated according to the following formula:

[0031] ,

[0032] Where d is the aperture of the electrically adjustable aperture, f is the focal length of the beam expander collimating lens group, D is the diameter of the light spot in the actual scene, and f and D are fixed values. The aperture of the electrically adjustable aperture is controlled by the above formula and the set target distance value.

[0033] Compared with the prior art, the significant advantages of this invention are:

[0034] This invention effectively simulates the energy change and beam divergence angle change of the laser spot during the entire terminal guidance process of the laser seeker by using an electrically adjustable optical attenuator and an electrically adjustable aperture, thereby increasing the calibration dataset of the laser seeker under different working conditions and effectively improving the line-of-sight angle calculation accuracy of the laser seeker.

[0035] The zero-position deviation of the laser seeker can be effectively eliminated by using a rotating turntable; the calibration and testing efficiency of the laser seeker can be effectively improved by using a zigzag scanning method.

[0036] By controlling the turntable's movement trajectory via computer and the data acquisition of the laser guide head, the calibration and testing process can be automated, effectively reducing labor costs. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the overall composition of the automated calibration and testing equipment for the laser seeker of the present invention.

[0038] Figure 2 This is a schematic diagram of the simulated target composition of the present invention.

[0039] Figure 3 This is a schematic diagram of the three-axis rotary table of the present invention.

[0040] Figure 4 This is a schematic diagram of the automatic calibration and testing method for the laser guide head of the present invention.

[0041] Figure 5 This is a schematic diagram of the calibration test method of the present invention. Detailed Implementation

[0042] The details and operation of the specific device proposed according to the present invention will be described in detail below with reference to the accompanying drawings.

[0043] As attached Figure 1As shown, the laser seeker calibration and testing equipment consists of a control computer 1, a simulated target 2, a three-axis turntable 3, and a laser seeker 4 to be calibrated. The control computer 1 controls the energy and beam divergence angle of the uniformly collimated laser beam output from the simulated target 2, and controls the three-axis turntable 3 to rotate around its yaw, pitch, and roll axes, as well as reading the energy percentage data in each direction output by the laser seeker to be calibrated. The laser seeker 4 to be calibrated is mounted on the three-axis turntable 3, with its entrance pupil center coinciding with the central axis of the simulated target 2. The three-axis turntable 3 moves according to a predetermined calibration grid, pausing briefly at each grid point to allow the control computer 1 to stably acquire the data output by the laser seeker 4. Based on the actual target distance, the laser power and beam divergence angle output from the simulated target 2 are calculated. By changing the laser power and beam divergence angle, the seeker data acquisition process is repeated to obtain multiple sets of calibration datasets at different target distances.

[0044] As attached Figure 2 As shown, the simulated target 2 consists of a laser 21, an electrically adjustable optical attenuator 22, an optical homogenizer 23, an electrically adjustable aperture 24, an optical beam splitter 25, a beam expander and collimating lens group 26, and an optical power meter 27. The laser 21, electrically adjustable optical attenuator 22, electrically adjustable aperture 24, and optical power meter 27 are connected to the control computer 1. After the laser passes through the electrically adjustable optical attenuator 22 and the electrically adjustable aperture 24, the laser energy and beam divergence angle can be effectively controlled to simulate different target distances. After the laser passes through the optical homogenizer 23, the originally Gaussian distributed light spot can be shaped into a uniformly distributed light spot to simulate the energy distribution of diffusely reflected light from the target. After the laser passes through the optical beam splitter 25, part of the light enters the beam expander and collimating lens group 26 to form a simulated light spot, and part of the light enters the optical power meter 27 to monitor the laser power.

[0045] The laser is a fiber laser, specifically, capable of generating pulsed lasers with instantaneous power exceeding 1kW, pulse width adjustable between 5ns and 20ns, and pulse repetition frequency adjustable between 1Hz and 100Hz.

[0046] Electrically adjustable optical attenuators consist of optical fibers and mechanical adjustment structures. Specifically, the optical attenuation ratio can be controlled by adjusting the coupling degree between the end faces of the incident and output optical fibers through the mechanical adjustment structure, achieving a continuously adjustable attenuation ratio within the range of 0~60dB. Alternatively, a large attenuation output can be achieved by connecting two electrically adjustable optical attenuators in series.

[0047] As attached Figure 3As shown, the three-axis turntable 3 consists of a yaw turntable 31, a pitch turntable 32, a roll turntable 33, and an adapter 34. The yaw turntable 31 rotates around the y-axis to simulate the movement of the laser seeker in the yaw direction, the pitch turntable 32 rotates around the z-axis to simulate the movement of the laser seeker in the pitch direction, and the roll turntable 33 rotates around the x-axis to eliminate zero-position deviation. The installation sequence of each turntable is as follows: the roll turntable 33 is mounted on the pitch turntable 32, the pitch turntable 32 is mounted on the yaw turntable 31, and the laser seeker 4 to be calibrated and tested is mounted on the roll turntable 33 via the adapter 34. The three rotation axes intersect perpendicularly in pairs, forming a spatial rectangular coordinate system.

[0048] The calibration test method is as follows:

[0049] First, control the turntable to rotate while simultaneously reading the yaw energy percentage and pitch energy percentage output by the laser seeker to be calibrated, until both are 0. Then, control only the yaw turntable to rotate, with the rotation angle equal to the maximum detectable angle of the laser seeker, while simultaneously reading the pitch energy percentage output by the laser seeker. If it is not 0, rotate the roll turntable until the pitch energy percentage is 0. Control the yaw turntable to rotate again until the yaw energy percentage is 0. Divide the calibration grid, as shown in the attached diagram. Figure 4 As shown, the yaw and pitch angles are divided into 21 equal parts, forming a 21×21 calibration grid with a total of 441 calibration points. The yaw and pitch turntables are controlled to rotate in a zigzag scanning pattern, briefly pausing at each calibration point to wait for the seeker to output the yaw and pitch energy percentages and store the data. The movement of the turntables and the acquisition of laser seeker data are pre-programmed into the control computer, achieving automatic control without human intervention. After acquiring one set of calibration datasets, the laser energy and laser beam divergence are adjusted as needed, and the above calibration test process is repeated to obtain multiple sets of calibration datasets. The control logic of the laser seeker calibration test equipment is as follows: Figure 5 As shown.

[0050] The relationship between laser power and target distance is expressed as follows:

[0051] Where k is a proportionality coefficient, determined based on atmospheric transmittance and illumination conditions, and R is the target distance. The control computer automatically controls the attenuation ratio of the electrically adjustable optical attenuator until the optical power value measured by the optical power meter equals P.

[0052] The relationship between beam divergence angle and target distance can be expressed as:

[0053] Where d is the aperture of the electrically adjustable aperture, f is the focal length of the beam expander and collimator lens group, D is the diameter of the light spot in the actual scene, and R is the target distance. f and D are fixed values. The aperture of the electrically adjustable aperture is controlled using the above formula and the set distance value.

Claims

1. A laser seeker calibration and testing device, characterized in that, It includes a control computer (1), a simulated target (2), a three-axis turntable (3), and a laser guide head to be calibrated and tested (4). The simulated target (2) is used to output uniformly collimated laser beams with different laser powers and divergence angles. The three-axis turntable (3) has rotational degrees of freedom in three directions: yaw, pitch, and roll. The laser guide head (4) to be calibrated is mounted on the three-axis turntable (3). The entrance pupil center of the laser guide head (4) to be calibrated coincides with the central axis of the simulated target (2). The control computer (1) controls the simulated target (2) to output a uniform collimated laser beam with a set power and divergence angle. The control computer (1) controls the three-axis turntable (3) to rotate around the three rotation axes of yaw, pitch and roll, and to move according to the predetermined calibration grid. It stops at each calibration grid point and waits for the control computer (1) to collect the data output by the laser seeker (4) to be calibrated. The laser power and divergence angle output by the simulated target (2) are calculated according to the set target distance. The laser power and divergence angle are changed, and the seeker data acquisition process is repeated to obtain multiple sets of calibration datasets at different target distances.

2. The calibration and testing equipment according to claim 1, characterized in that, The simulated target (2) includes a laser (21), an electrically adjustable optical attenuator (22), an optical homogenizer (23), an electrically adjustable aperture (24), an optical beam splitter (25), a beam expander collimating lens group (26), and an optical power meter (27) connected in sequence. The laser (21), electrically adjustable optical attenuator (22), electrically adjustable aperture (24), and optical power meter (27) are connected to the control computer (1). The laser power and beam divergence angle of the laser beam are adjusted by the electrically adjustable optical attenuator (22) and electrically adjustable aperture (24) to simulate different target distances. The light homogenizer (23) is used to shape the originally Gaussian distributed light spot into a uniformly distributed light spot to simulate the light spot energy distribution of the diffuse reflection light of the target. After the laser passes through the optical beam splitter (25), part of the light enters the beam expanding collimating lens group (26) to form a simulated light spot, and part of the light enters the optical power meter (27) to monitor the laser power.

3. The calibration test equipment according to claim 2, characterized in that, The laser (21) is a fiber laser that can generate pulsed laser with instantaneous power higher than 1kW, pulse width adjustable between 5ns and 20ns, and pulse repetition frequency adjustable between 1Hz and 100Hz.

4. The calibration test equipment according to claim 3, characterized in that, The electrically adjustable optical attenuator (22) includes an optical fiber and a mechanical adjustment structure. The coupling degree of the end faces of the incident and outgoing optical fibers is controlled by the mechanical adjustment structure to achieve a continuously adjustable attenuation ratio in the range of 0~60dB.

5. The calibration test equipment according to claim 4, characterized in that, A larger attenuation ratio can be achieved by connecting two electrically adjustable optical attenuators in series.

6. The calibration test equipment according to claim 5, characterized in that, The three-axis turntable (3) includes a yaw turntable (31), a pitch turntable (32), a roll turntable (33), and a connector (34). The yaw turntable (31) rotates around the y-axis to simulate the movement of the laser seeker in the yaw direction, the pitch turntable (32) rotates around the z-axis to simulate the movement of the laser seeker in the pitch direction, and the roll turntable (33) rotates around the x-axis to eliminate zero position deviation. The roll turntable (33) is mounted on the pitch turntable (32), the pitch turntable (32) is mounted on the yaw turntable (31), and the laser seeker (4) to be calibrated and tested is mounted on the roll turntable (33) through the adapter (34). The rotation axes of the three turntables intersect perpendicularly in pairs, forming a spatial rectangular coordinate system.

7. A method for calibrating and testing a laser seeker head based on the calibration and testing equipment according to any one of claims 1-6, characterized in that, Includes the following steps: Step (1): Find the zero position; Step (2): Divide the calibration grid; Step (3): Calculate the laser power and beam divergence angle based on the set target distance, and set the parameters of the electrically adjustable optical attenuator (22) and the aperture of the electrically adjustable aperture (24) based on the calculation results; Step (4): Control the yaw and pitch turntables to rotate in a zigzag scanning pattern, pause when passing the calibration point, and collect the output coefficient value of the seeker at the calibration point; Step (5): Move according to the calibration grid trajectory in step (2), repeat step (4) until the calibration grid has been traversed; Step (6): Change the target distance and repeat steps (3)-(5) until the target distance is traversed.

8. The method according to claim 7, characterized in that, Step (1) is as follows: First, control the turntable to rotate while reading the yaw energy ratio and pitch energy ratio output by the laser seeker to be calibrated, until both are 0. Subsequently, only the yaw turntable is controlled to rotate, with the rotation angle being the maximum detectable angle of the laser seeker. At the same time, the pitch energy percentage output by the laser seeker is read. If it is not 0, the roll turntable is rotated until the pitch energy percentage is 0. Control the rotation of the yaw turntable to bring the yaw energy percentage back to 0.

9. The method according to claim 8, characterized in that, Step (2) specifically involves dividing the yaw and pitch angles into 21 parts to form a 21×21 calibration grid, resulting in a total of 441 calibration points.

10. The method according to claim 9, characterized in that, In step (3), the laser power P is calculated according to the following formula: ， Where k is the scaling factor and R is the target distance; The beam divergence angle α is calculated according to the following formula: ， Where d is the aperture of the electrically adjustable aperture, f is the focal length of the beam expander collimating lens group, D is the diameter of the light spot in the actual scene, and f and D are fixed values. The aperture of the electrically adjustable aperture is controlled by the above formula and the set target distance value.

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