Automatic Calibration System and Method for Fast Steering Mirror Angle Based on PSD Sensor

Abstract

A fast steering mirror angle automatic calibration system and method based on a PSD sensor belong to the technical field of fast steering mirror surface calibration. It solves the technical problems of low efficiency and accuracy in the conventional fast steering mirror surface angle calibration. By utilizing the high resolution and fast response characteristics of the PSD, the present invention proposes an efficient automatic calibration method. A narrowband filter is used in combination with power supply ripple to remove the influence of noise, effectively suppressing the problem that the position calculation of the PSD sensor is vulnerable to optoelectronic noise interference and improving the measurement stability. During the calibration process, real-time data filtering and automatic acquisition are adopted to reduce manual intervention and the influence of the observation errors brought by it. Compared with the traditional calibration method, this method does not require an autocollimator, has a faster calibration speed and lower cost. The present invention breaks through the limitation of the application of the PSD as a linear displacement sensor in high-precision angle measurement, providing an efficient and low-cost solution for the calibration of the fast steering mirror angle.

Description

Technical Field

[0001] The present invention belongs to the technical field of fast steering mirror mirror calibration, and particularly relates to a fast steering mirror angle automatic calibration system and method based on a PSD sensor. Background Art

[0002] A fast steering mirror (FSM) is an optical device used for precisely and rapidly controlling and adjusting the direction of a light beam. It is commonly used in optical systems that require high precision and fast response, such as laser communication, optical imaging, and adaptive optics. It features high angular resolution, fast response speed, and high bandwidth.

[0003] Due to the fact that the eddy current position sensor in the fast steering mirror belongs to an analog device, affected by factors such as the non-linear characteristics of components and the structural installation error, when the fast steering mirror mirror is at different angular positions, the output value (AD code value) of the eddy current sensor has a non-linear relationship with it, resulting in a poor pointing accuracy of the fast steering mirror mirror, and it is necessary to perform fitting correction to improve the accuracy.

[0004] Usually, the calibration of the fast steering mirror mirror angle is carried out by using an autocollimator. At different code values output by the eddy current, the actual value of the mirror angle corresponding to it is read by the autocollimator, and through the corresponding relationship curve of the two sets of values, a non-linear formula is fitted or interpolation calculation is performed to improve the angular pointing accuracy of the fast steering mirror mirror. A complete calibration process for a two-axis fast steering mirror requires manually reading and recording nearly a hundred angular position data for the X and Y axes, and then performing fitting processing with mathematical processing software, which makes the calibration efficiency of the fast steering mirror very low, and there is also a problem of low calibration accuracy. Summary of the Invention

[0005] In order to solve the technical problems of low calibration efficiency and accuracy of the fast steering mirror mirror angle in the past, the present invention provides a fast steering mirror angle automatic calibration system and method based on a PSD sensor.

[0006] The system includes a calibration control board and a computer. The calibration control board includes a central axis alignment laser module, an X-axis laser module, a Y-axis laser module, an X-axis one-dimensional PSD sensor, a Y-axis one-dimensional PSD sensor, an X-axis ready indicator light, and a Y-axis ready indicator light;

[0007] The centers of the X-axis laser module, the Y-axis laser module, the centers of the X-axis one-dimensional PSD sensor, and the Y-axis one-dimensional PSD sensor together form a circle with the central axis alignment laser module as the center and a radius of r. The connection line between the center of the X-axis laser module and the center of the X-axis one-dimensional PSD sensor is parallel to the horizontal plane, and the connection line between the center of the Y-axis laser module and the center of the Y-axis one-dimensional PSD sensor is parallel to the vertical plane.

[0008] Further, narrowband filters are attached to the surfaces of the one-dimensional PSD sensors on the X-axis and the one-dimensional PSD sensors on the Y-axis to filter out external optical noise.

[0009] The method is carried out using the fast mirror angle automatic calibration system based on the PSD sensor as described above. Specifically, the method is as follows:

[0010] S1. Calibration preparation: The mirror surface of the fast mirror is parallel to the calibration control board and aligned with the central axis. Adjust the emission angles of the X-axis laser module and the Y-axis laser module so that the parallel light emitted by them is reflected by the mirror surface of the fast mirror, and the light spots respectively irradiate the central positions of the one-dimensional PSD sensor on the X-axis and the one-dimensional PSD sensor on the Y-axis. The calibration preparation work is completed.

[0011] S2. Start calibration: The computer sends calibration instructions to the fast mirror and the calibration control board, and sends the AD code value instructions of eddy current to the X-axis of the fast mirror at regular intervals, and then sends the AD code value instructions of eddy current to the Y-axis of the fast mirror at regular intervals... 、 、 … 、 、 … The AD code value instructions of eddy current, and then sends the AD code value instructions of eddy current to the Y-axis of the fast mirror at regular intervals... 、 、 … 、 、 … The AD code value instructions of eddy current;

[0012] S3. After receiving the computer control instructions, the fast mirror runs to the specified AD code value position in sequence. At the same time, the calibration control board returns the calculated fast mirror angle data to the computer in sequence, and the computer stores the AD code value and the corresponding fast mirror angle data information returned in sequence.

[0013] S4. Use mathematical tool software to perform fitting or interpolation calculations on the data stored in the computer, select a non-linear mathematical model to fit out a formula or generate a difference table, and substitute the fitting formula or difference table into the calculation of the actual mirror surface angle in the fast mirror controller for correction.

[0014] Further, the parallel and aligned central axes are specifically as follows: The fast steering mirror is placed on a fixed platform, and the calibration control board is placed on an adjustable two-dimensional platform. After the computer sends a preparation instruction, the fast steering mirror is powered on and the mirror surface is locked and remains stationary at the zero position on the X and Y axes. At the same time, the central axis alignment laser module vertically placed at the center of the calibration control board is lit. The two-dimensional platform and the placement angle of the calibration control board are adjusted so that the parallel light emitted by the central axis alignment laser module vertically placed at the center of the calibration control board is perpendicularly irradiated onto the center of the mirror surface of the fast steering mirror and then returns to the center position of the calibration control board. At this time, the mirror surface of the fast steering mirror is parallel to the calibration control board and the centers are aligned, and the distance L between the two is measured and recorded.

[0015] Further, the specific adjustment of the emission angles of the X-axis laser module and the Y-axis laser module is as follows: The mirror surface of the fast steering mirror remains stationary at the zero position on the X and Y axes. The parallel light emitted by the X-axis laser module and the Y-axis laser module is reflected by the mirror surface of the fast steering mirror. By respectively adjusting the mounting angle screws of the X-axis laser module and the Y-axis laser module, the returned light spot is made to fall on the center position of the corresponding axis PSD sensor. When the light spot position is correct, the X-axis ready indicator light and the Y-axis ready indicator light automatically light up, indicating that the calibration preparation work between the fast steering mirror and the calibration control board is completed and calibration can be carried out.

[0016] Further, after the fast steering mirror receives the computer control instruction, it runs to the specified AD code value position in sequence. The difference between the maximum and minimum eddy current code values of the total travel of the X-axis of the fast steering mirror is , The code value at the center position is , and the step code value each time is , N is the number of steps, that is , , … , , … The position code values are equivalent to , , …… , , …… , and the Y-axis of the fast steering mirror adopts the same calculation method.

[0017] Further, the specific calculation of the angle data of the fast steering mirror is as follows:

[0018] When the mirror surface of the fast steering mirror runs to the specified AD code value position, the angle value of the mirror surface of the fast steering mirror rotating with respect to the zero position of the X-axis is , and the relational expression for calculating the mirror surface angle change amount by the calibration control board is:

[0019] ;

[0020] Wherein, is the distance between the spot of the X-axis one-dimensional PSD sensor and the zero position of the X-axis one-dimensional PSD sensor when the mirror surface of the fast steering mirror runs to the specified AD code value position. , wherein and are the photocurrent code values of the two electrodes at both ends of the X-axis one-dimensional PSD sensor. is half of the effective photosensitive surface length of the X-axis one-dimensional PSD sensor. The angle value of the fast steering mirror rotating corresponding to the zero position of the Y-axis is solved in the same way.

[0021] The beneficial effects of the present invention are as follows:

[0022] The system described in the present invention can simultaneously realize the continuous calibration of the X-axis and Y-axis of the fast steering mirror, save the calibration time of the mirror surface angle of the fast steering mirror, and adopt the structure that the center of the X-axis laser module, the center of the Y-axis laser module, the center of the X-axis one-dimensional PSD sensor, and the center of the Y-axis one-dimensional PSD sensor jointly form a circle with the center-aligned laser module as the center and a radius of r, which can minimize the calibration error between the X-axis and the Y-axis, and this is very important for accurately calibrating the fast steering mirror.

[0023] When calibrating, the method described in the present invention sends , , … , , … AD code value commands of eddy current to the X-axis of the fast steering mirror at regular intervals. is the code value of the center position, and the step code value each time is , N is the number of steps, that is , , … , , … The position code values are equivalent to , , …… , , …… ; This calibration method is different from the conventional calibration method of gradually increasing the code value. The calibration method described in the present invention first determines the center position code value, and then expands from this until , and then returns to again and is adjacent to , this step is approximately equivalent to confirming the center position again and then calibrating outward; the above calibration method can better improve the calibration accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the calibration control board in the embodiment of the present invention;

[0025] Figure 2 Schematic diagram of the fast steering mirror angle automatic calibration system based on PSD sensor in the embodiment of the present invention;

[0026] Figure 3 Schematic diagram of the fast steering mirror calibration in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] This embodiment provides a fast steering mirror angle automatic calibration system based on a PSD sensor, as Figure 1-2 shown. The system includes a calibration control board 1 and a computer 9. The calibration control board 1 includes a central axis alignment laser module 2, an X-axis laser module 3, a Y-axis laser module 4, an X-axis one-dimensional PSD sensor 5, a Y-axis one-dimensional PSD sensor 6, an X-axis ready indicator light 7, and a Y-axis ready indicator light 8.

[0029] The centers of the X-axis laser module 3, the Y-axis laser module 4, the centers of the X-axis one-dimensional PSD sensor 5, and the Y-axis one-dimensional PSD sensor 6 together form a circle with the central axis alignment laser module 2 as the center and a radius of r. In this embodiment, r = 100 mm. The line connecting the center of the X-axis laser module 3 and the center of the X-axis one-dimensional PSD sensor 5 is parallel to the horizontal plane, and the line connecting the center of the Y-axis laser module 4 and the center of the Y-axis one-dimensional PSD sensor 6 is parallel to the vertical plane.

[0030] To reduce the influence of environmental light source noise on the PSD signal calculation, narrowband filters are pasted on the surfaces of the X-axis one-dimensional PSD sensor 5 and the Y-axis one-dimensional PSD sensor 6 to filter out external light noise. The purpose is to filter out the noise interference generated by stray light and only receive the spot signals emitted by the laser module wavelength. In one implementation, the spectral range passed by the narrowband filter is 808 nm ± 10 nm. At the same time, to reduce the influence of electronic noise, the laser module, PSD, and amplifier processing circuits all use LDO power chips to reduce the influence of power supply ripple on the PSD signal. In one implementation, the power supply ripple is controlled within ±5 mv.

[0031] The calibration control board 1 conducts data instruction communication through the RS422 interface.

[0032] This embodiment also provides a method for automatically calibrating the angle of a fast steering mirror based on a PSD sensor. The method is carried out using the above-mentioned automatic calibration system for the angle of a fast steering mirror based on a PSD sensor. Specifically, the method is as follows:

[0033] S1. Calibration preparation: The mirror surface of the fast steering mirror is parallel to and aligned with the central axis of the calibration control board 1. Adjust the emission angles of the X-axis laser module 3 and the Y-axis laser module 4 so that the parallel light emitted by them is reflected by the mirror surface of the fast steering mirror, and the light spots respectively irradiate the central positions of the X-axis one-dimensional PSD sensor 5 and the Y-axis one-dimensional PSD sensor 6. The calibration preparation work is completed;

[0034] S2. Start calibration: The computer 9 sends calibration instructions to the fast steering mirror and the calibration control board 1, and sends the AD code value instructions of eddy current to the X-axis of the fast steering mirror at regular intervals, and then sends the AD code value instructions of eddy current to the Y-axis of the fast steering mirror at regular intervals; 、 、 … 、 、 … The AD code value instructions of eddy current, and then sends the AD code value instructions of eddy current to the Y-axis of the fast steering mirror at regular intervals; 、 、 … 、 、 … The AD code value instructions of eddy current;

[0035] S3. After receiving the control instructions from the computer 9, the fast steering mirror runs to the specified AD code value positions in sequence. At the same time, the calibration control board 1 returns the calculated angle data of the fast steering mirror to the computer 9 in sequence, and the computer 9 stores the AD code values and the corresponding fast steering mirror angle data information in order;

[0036] S4. Use mathematical tool software to perform fitting or interpolation calculations on the data stored in the computer 9, select a non-linear mathematical model to fit the formula or generate a difference table, and substitute the fitting formula or difference table into the calculation of the actual mirror surface angle in the fast steering mirror controller for correction.

[0037] The mirror surface of the fast steering mirror runs to the specified DN code value positions in sequence according to the instruction order. After all the Y-axis positions are completed, the fast steering mirror returns to Zero-position DN position retention. In one implementation, the time for the fast steering mirror to move to the specified AD code value position is in the millisecond range. The computer 9 sends commands at intervals of 1 second. After each AD code value is sent and the mirror reaches the position, the calibration control board 1 calculates the mirror angle and returns it to the computer 9 for recording.

[0038] Specifically, the parallel and axis-aligned center line means that the fast steering mirror is placed on a fixed platform, and the calibration control board 1 is placed on an adjustable two-dimensional platform. After the computer 9 sends a preparation command, the fast steering mirror is powered on and the mirror is locked and remains stationary at the zero-position on the X and Y axes. At the same time, the central axis alignment laser module 2 vertically placed on the calibration control board 1 is lit. The angle of the two-dimensional platform and the calibration control board 1 is adjusted so that the parallel light emitted by the central axis alignment laser module 2 vertically placed on the calibration control board 1 is vertically incident on the center of the fast steering mirror surface and then returns to the center position of the calibration control board 1. At this time, the fast steering mirror surface is parallel to the calibration control board 1 and the centers are aligned, and the distance L between them is measured and recorded.

[0039] Specifically, the emission angles of the X-axis laser module 3 and the Y-axis laser module 4 are adjusted as follows: The fast steering mirror surface remains stationary at the zero-position on the X and Y axes. The parallel light emitted by the X-axis laser module 3 and the Y-axis laser module 4 is reflected by the fast steering mirror surface. By adjusting the installation angle screws of the X-axis laser module 3 and the Y-axis laser module 4 respectively, the returned light spot is made to fall on the center position of the corresponding axis PSD sensor. When the light spot position is correct, the X-axis ready indicator 7 and the Y-axis ready indicator 8 automatically light up, indicating that the calibration preparation work between the fast steering mirror and the calibration control board 1 is completed and calibration can be performed.

[0040] After receiving the control command from the computer 9, the fast steering mirror runs to the specified AD code value position in sequence. The difference between the maximum and minimum eddy current code values of the total travel of the X-axis of the fast steering mirror is , that is is the difference between the maximum and minimum AD code values of the left and right limits of the X-axis, the code value of the center position is , and the step code value each time is , N is the number of steps, that is 、 、 … 、 、 … The position code value is equivalent to 、 、 …… 、 、 …… , the same calculation method is used for the Y-axis of the fast steering mirror; the larger the N value, the more accurate the calibration, and at the same time, the longer the calibration time. In one implementation, the X-axis is 1204 code values, N is taken as 100, and the stepping code value of the X-axis is taken as 12 code values.

[0041] The specific calculation of the fast steering mirror angle data is as follows:

[0042] As Figure 3 shown, when the computer 9 periodically sends an AD code value instruction sequence to the X-axis of the fast steering mirror, the X-axis of the fast steering mirror moves to the specified AD code value position in sequence. At the same time, the light beam emitted by the X-axis laser module is reflected by the fast steering mirror, and the position of the light spot on the PSD photosensitive surface of the X-axis also changes in sequence. The calibration control board 1 calculates the distance d between the light spot and the PSD zero-position center. Then, according to the distance L between the fast steering mirror and the center of the calibration control board 1, the angle of rotation of the fast steering mirror mirror surface can be calculated, and the data sequence of the fast steering mirror X-axis angle is returned to the computer 9 in sequence , , … , , … , where is the center position when the light spot is projected onto the center of the X-axis one-dimensional PSD sensor 5, that is, the X-axis center zero-degree position of the fast steering mirror.

[0043] The calculation principle of the calibration control board 1 is that is the angle of rotation of the fast steering mirror under the instruction, that is, the angle value of the fast steering mirror mirror surface corresponding to the X-axis zero-position rotation , and the relationship formula for the calibration control board 1 to calculate the mirror surface angle change amount is:

[0044] ;

[0045] This is to use the principle of the double angle of the mirror rotation, that is, when the mirror rotates angle, the reflected light will rotate angle. Then, using the relationship that the central angle radian value is equal to the arc length divided by the radius, under the condition that the distance L is much larger than d, d is approximately equal to the arc length, and then multiplying by 57.3 to convert the radian value to an angle value, the light rotation angle is obtained:

[0046] ;

[0047] The length of the light spot position d can be calculated by collecting the photocurrent value generated by the light spot on the PSD sensor by the calibration control board 1. The formula is as follows:

[0048] ;

[0049] Among them and are the photocurrent code values of the two electrodes at both ends of the one-dimensional PSD sensor 5 on the X-axis. S is half of the effective length of the effective photosensitive surface of the PSD device, and the spot position d is the calculated offset position relative to the zero position of the center of the PSD. Similarly, … , , … and , , … , , … the mirror angle values of...

[0050] Using mathematical tool software to fit or interpolate the data stored in the computer 9, specifically including:

[0051] The data of the X-axis and Y-axis recorded by the computer 9 are respectively the given AD code values and the returned angle values, which are represented by matrices as follows:

[0052]

[0053] The data stored in the computer 9 is opened using mathematical tool software such as MATLAB and Origin, and a non-linear mathematical model is selected to fit the formula or perform interpolation calculation. When calculating the actual mirror angle in the fast steering mirror controller, the fitting formula or interpolation table is substituted for correction.

[0054] In one implementation, the distance L between the calibration control board 1 and the fast steering mirror surface is set to 500 mm.

[0055] The angular travel ranges of the X and Y axes of the fast steering mirror are ±1°. It is calculated that the maximum length d of the distance from the center of the one-dimensional PSD sensors 5 and 6 to one end is not less than 8.73 mm, and a one-dimensional PSD sensor with a total photosensitive surface length of 20 mm is selected.

Claims

1. A method for automatically calibrating the angle of a fast steering mirror based on a PSD sensor, which is performed using an automatic calibration system for the angle of a fast steering mirror based on a PSD sensor. The system includes a calibration control board (1) and a computer (9). The calibration control board (1) includes a central axis alignment laser module (2), an X-axis laser module (3), a Y-axis laser module (4), an X-axis one-dimensional PSD sensor (5), a Y-axis one-dimensional PSD sensor (6), an X-axis ready indicator light (7), and a Y-axis ready indicator light (8). The centers of the X-axis laser module (3), the Y-axis laser module (4), the centers of the X-axis one-dimensional PSD sensor (5), and the Y-axis one-dimensional PSD sensor (6) together form a circle with the central axis alignment laser module (2) as the center and a radius of r. The line connecting the center of the X-axis laser module (3) and the center of the X-axis one-dimensional PSD sensor (5) is parallel to the horizontal plane, and the line connecting the center of the Y-axis laser module (4) and the center of the Y-axis one-dimensional PSD sensor (6) is parallel to the vertical plane. It is characterized in that, The specific method is as follows: S1. Calibration preparation: The mirror surface of the fast steering mirror is parallel to and aligned with the central axis of the calibration control board (1). Adjust the emission angles of the X-axis laser module (3) and the Y-axis laser module (4) so that the parallel light emitted by them is reflected by the mirror surface of the fast steering mirror, and the light spots respectively irradiate the central positions of the X-axis one-dimensional PSD sensor (5) and the Y-axis one-dimensional PSD sensor (6), completing the calibration preparation work. S2. Start calibration. The computer (9) sends calibration instructions to the fast steering mirror and the calibration control board (1), and sends the AD code value instructions of eddy current to the X-axis of the fast steering mirror at regular intervals, and then sends the AD code value instructions of eddy current to the Y-axis of the fast steering mirror at regular intervals. 、 、 … 、 、 … 、 、 … 、 、 … ​ S3. After the fast steering mirror receives the control instruction from the computer (9), it runs to the specified AD code value position in sequence. At the same time, the calibration control board (1) returns the calculated fast steering mirror angle data to the computer (9) in sequence, and the computer (9) stores the AD code value and the corresponding fast steering mirror angle data information returned in sequence. S4. Use mathematical tool software to perform fitting or interpolation calculations on the data stored in the computer (9), select a non-linear mathematical model to fit the formula or generate a difference table, and substitute the fitting formula or difference table into the calculation of the actual mirror surface angle in the fast steering mirror controller for correction.

2. The automatic calibration method for the angle of a fast steering mirror based on a PSD sensor according to claim 1, characterized in that, The specific meaning of "parallel and aligned with the central axis" is as follows: The fast steering mirror is placed on a fixed platform, and the calibration control board (1) is placed on an adjustable two-dimensional platform. After the computer (9) sends a preparation instruction, the fast steering mirror is powered on and the mirror surface is locked and remains stationary at the zero position of the X and Y axes. At the same time, the central axis alignment laser module (2) vertically placed at the center of the calibration control board (1) is lit. Adjust the placement angle of the two-dimensional platform and the calibration control board (1) so that the parallel light emitted by the central axis alignment laser module (2) vertically placed at the center of the calibration control board (1) is vertically irradiated onto the center of the mirror surface of the fast steering mirror and then returns to the center position of the calibration control board (1). At this time, the mirror surface of the fast steering mirror is parallel to and centered with the calibration control board (1), and the distance L between the two is measured and recorded.

3. The automatic calibration method for the angle of the fast steering mirror based on the PSD sensor according to claim 2, characterized in that, The specific adjustment of the emission angles of the X-axis laser module (3) and the Y-axis laser module (4) is as follows: The mirror surface of the fast steering mirror remains stationary at the zero position of the X and Y axes. The parallel light emitted by the X-axis laser module (3) and the Y-axis laser module (4) is reflected by the mirror surface of the fast steering mirror. By respectively adjusting the installation angle screws of the X-axis laser module (3) and the Y-axis laser module (4), the returned light spot is made to fall on the central position of the corresponding axis PSD sensor. When the light spot position is correct, the X-axis ready indicator light (7) and the Y-axis ready indicator light (8) automatically light up, indicating that the calibration preparation work between the fast steering mirror and the calibration control board (1) is completed and calibration can be carried out.

4. The automatic calibration method for the angle of a fast steering mirror based on a PSD sensor according to claim 3, characterized in that After receiving the control instruction from the computer (9), the fast steering mirror runs to the specified AD code value position in sequence. The difference between the maximum and minimum eddy current code values of the total travel of the X-axis of the fast steering mirror is , The code value at the center position is , and the step code value each time is , N is the number of steps, that is , , … , , … The position code value is equivalent to , , …… , , …… . The same calculation method is adopted for the Y-axis of the fast steering mirror.

5. The automatic calibration method for the angle of a fast steering mirror based on a PSD sensor according to claim 4, wherein The specific calculation of the fast steering mirror angle data is as follows: When the mirror surface of the fast steering mirror runs to the specified AD code value position, the angular value of the mirror surface of the fast steering mirror rotating corresponding to the zero position of the X-axis is , and the calibration control board (1) calculates the relational expression of the mirror surface angle change amount as: ； Among them, is the distance between the light spot of the X-axis one-dimensional PSD sensor (5) and the zero position of the X-axis one-dimensional PSD sensor (5) when the mirror surface of the fast steering mirror runs to the specified AD code value position, , is the distance between the calibration control board (1) and the mirror surface of the fast steering mirror, where and are the photocurrent code values of the two ends of the electrodes of the X-axis one-dimensional PSD sensor (5), is half of the effective photosensitive surface length of the X-axis one-dimensional PSD sensor (5). The angle value of the rotation of the mirror surface of the fast steering mirror corresponding to the zero position of the Y-axis is solved in the same way.

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