Fine pointing method for laser communication based on spatial beam scanning

Abstract

The application relates to the technical field of laser communication, in particular to a laser communication fine aiming method based on spatial beam scanning, which can complete laser signal direction positioning and further improve the fine aiming efficiency and accuracy of optical signals, utilizes the reflection characteristics of light, projects signal light onto a CCD with the aid of a scanning component in a fine aiming assembly; meanwhile, an image processing algorithm is integrated to judge the geometric parameters of the light spot, so that the following tracking is facilitated, specifically as follows: after coarse aiming is completed, signal light is emitted to the area near the receiving end and has an angle deviation, a scanning mechanism reflects the signal light to the side CCD array, so that the signal light is projected onto the CCD to form a light spot; the light spot received on the CCD is converted into geometric parameters through a graphic processing unit, so that the incidence angle of the signal light on the CCD is determined; in combination with the rotating position of the scanning mechanism corresponding to the light spot, the direction of the signal light is determined through a calculation unit, so that fine aiming work is quickly completed.

Description

Technical fields:

[0001] This invention relates to the field of laser communication technology, specifically a laser communication precision aiming method based on spatial beam scanning that can achieve laser signal direction positioning, thereby improving the precision aiming efficiency and accuracy of optical signals. Background technology:

[0002] In the acquisition process between terminals in a laser communication system, coarse aiming is first performed using a beacon beam with a large beam divergence angle, followed by fine aiming using a signal beam with a smaller diameter and beam divergence angle. However, aiming is bidirectional. According to traditional methods, to make the optical axes of the terminals coincide, multiple alignment operations are required using an optical power meter to find the maximum power value. This relies on iteration to improve aiming accuracy, resulting in wasted time and low efficiency. Summary of the Invention:

[0003] This invention addresses the shortcomings and deficiencies of existing technologies by providing a spatial beam scanning-based precision aiming method that can directly locate the direction of signal light, thereby improving precision aiming efficiency.

[0004] This invention achieves its purpose through the following measures:

[0005] A precision aiming method based on spatial beam scanning is characterized by utilizing the reflection characteristics of light and employing a scanning component in the precision aiming assembly to project signal light onto a CCD. Simultaneously, an integrated image processing algorithm determines the geometric parameters of the light spot for subsequent tracking. Specifically, after coarse aiming, the signal light is emitted near the receiving end area with an angular deviation. A scanning mechanism reflects the signal light onto a side-mounted CCD array, projecting the signal light onto the CCD to form a light spot. An image processing unit converts the received light spot on the CCD into geometric parameters, thereby determining the incident angle of the signal light on the CCD. Combined with the rotational position of the scanning mechanism corresponding to the light spot, a calculation unit determines the direction of the signal light, thus quickly completing the precision aiming process.

[0006] The scanning component in the precision aiming assembly of this invention consists of a rotating shaft and a plane mirror. The plane mirror is circular with a diameter of Φ18. The angle between the mirror and the rotating shaft is 45°, and the center of the mirror is located on the straight line of the rotating shaft. The rotating shaft has a diameter of Φ12 and is controlled by a stepper motor. The stepper motor is an OUKEDA brand 20STH38EC1 motor, which is equipped with an encoder to read the real-time rotation angle during the scanning process. The surface of the mirror is coated with a reflective film. The material of the rotating shaft can be 45# steel. There should be no relative movement between the two. The two components can be connected by welding, bonding, threading, or directly cut from a single blank.

[0007] The precision aiming component of this invention comprises a CCD array consisting of four planar CCDs, model Kodak KAF-5100CE, each 17*13 cm in size. The assembled CCDs form a 17*13*13 cuboid shape. Adjacent CCDs are vertically mounted, forming the four sides of the cube. The center of the planar reflector surface coincides with the solid center of the cube, and the rotation axis is aligned with the straight line connecting the geometric centers of the bottom and top surfaces of the cube. In other words, each CCD plane should be parallel to the rotation axis of the scanning mechanism and equidistant from it. Each CCD is equipped with a processor capable of recording the real-time spot shape. The four CCD processors can be integrated with the graphics processing unit and computing unit (mentioned later) on the same FPGA board. The FPGA used is an AMD Xilinx FPGA. model.

[0008] The function of the graphics processing unit in the precision aiming component of this invention is implemented by pixel counting and centroid algorithm. The graphics processing unit obtains the area of ​​the elliptical spot by using pixel counting based on the shape recorded by the CCD processor, and then determines the centroid of the spot by using the centroid algorithm. Next, it traverses all the pixels covered by the spot to find the point farthest from the centroid and records the orientation and distance of the point relative to the centroid in the CCD coordinate system (i.e., the center coordinates, the endpoint coordinates of the major axis, and the length of the semi-major axis of the ellipse).

[0009] The precision aiming component of this invention includes a calculation unit 1 for calculating relative direction and a calculation unit 2 for calculating absolute direction. The calculation unit 1 collects data provided by the image processing unit to calculate the direction of the signal light after reflection by the plane mirror. Then, with the help of data provided by the encoder on the stepper motor, the relative direction of the signal light in the scanning coordinate system is calculated according to the law of light reflection. If it is necessary to calculate the absolute direction, an orientation measurement system (IMU or GNSS) can be used to complete the coordinate transformation of the signal light from the scanning coordinate system to the inertial coordinate system on the calculation unit 2, and finally determine the original direction of the signal light.

[0010] The precision aiming component of this invention also includes a main control module and a motor drive component. The main control module is used for user interaction and data transmission with external devices (such as turntable control). The motor drive component controls the stepper motor, and the main control module determines whether to perform scanning, the scanning method (continuous or step), and the speed.

[0011] The precision aiming method based on spatial beam scanning described in this invention is specifically as follows:

[0012] The signal light is reflected by a plane mirror and projected onto one of the CCDs to form a light spot. The shape of the light spot is recorded by the CCD processor and transmitted to the graphics processing unit for recording. The area S of the elliptical light spot is obtained by counting pixels, as follows:

[0013]

[0014] Where m i This indicates whether a light spot is projected onto the pixel unit; if yes, it is 1, otherwise it is 0, and so on.

[0015] Determine the centroid C(x) of the light spot using the centroid algorithm. C ,y C The process of finding the centroid is as follows:

[0016]

[0017] Find the point A furthest from the centroid using pixel counting, and record its orientation (Δx, Δy) and distance d relative to the centroid in the CCD coordinate system. For the furthest point A(x...y...d...), find the point A(x...y...d...). A ,y A ),have Where Δx=x A -x C Δy=y A -y C The largest d-value obtained is the length of the major semi-axis of the elliptical spot;

[0018] The angle φ between the signal light projected onto the CCD and the CCD plane is...

[0019] The azimuth angle ψ of the signal light projected onto the CCD is... Right now:

[0020]

[0021]

[0022] Determine the direction vector R of the projected signal light. This can be represented as...

[0023] R=(cosφcosψcosφsinψsinφ) T

[0024] The normal vector n of the plane mirror at that moment is obtained from the rotation angle measurement θ obtained from the encoder. Assuming the direction of the rotation axis is parallel to the positive y-axis, and the mirror surface is initially parallel to the x-axis and pointing downwards, then the vector of the mirror normal at the rotation angle θ is...

[0025]

[0026] By solving the system of equations: R = I - 2I T The direction vector of the incident signal light I is obtained by solving nn.

[0027] Compared with existing optical communication terminal designs, this invention has the following advantages: (1) It uses spatial beam scanning to acquire signal light, thus expanding the acquisition range. (2) It uses a CCD array, which covers all the directional information of the signal light in space. (3) It can directly determine the direction of the signal light, saving the time of fine-tuning the alignment multiple times with an optical power meter. Attached image description:

[0028] Appendix Figure 1 This is a schematic diagram of the precision aiming component in this invention.

[0029] Appendix Figure 2 This is a schematic diagram of the scanning component in this invention. Detailed implementation method:

[0030] The present invention will be further described below with reference to the accompanying drawings.

[0031] Example:

[0032] This example provides a precision aiming method based on spatial beam scanning. Utilizing the reflection properties of light, a scanning component in the precision aiming assembly projects the signal light onto a CCD. Simultaneously, an integrated image processing algorithm determines the geometric parameters of the light spot, facilitating subsequent tracking. Specifically, after coarse aiming, the signal light is emitted near the receiving area with an angular deviation. A scanning mechanism reflects the signal light onto a side-mounted CCD array, projecting it onto the CCD to form a light spot. An image processing unit converts the received light spot on the CCD into geometric parameters, determining the incident angle of the signal light on the CCD. Combined with the rotational position of the scanning mechanism corresponding to the light spot, a calculation unit determines the direction of the signal light, thus quickly completing the precision aiming process.

[0033] As attached Figure 1 and appendix Figure 2 As shown, the scanning component in the precision aiming assembly described in this example consists of a rotating shaft and a plane mirror. The plane mirror is circular with a diameter of Φ18. The angle between the mirror and the rotating shaft is 45°, and the center of the mirror is located on the straight line of the rotating shaft. The rotating shaft has a diameter of Φ12 and is controlled by a stepper motor. The stepper motor is an OUKEDA brand 20STH38EC1 motor, which is equipped with an encoder to read the real-time rotation angle during the scanning process. The surface of the mirror is coated with a reflective film. The material of the rotating shaft can be 45# steel. There should be no relative movement between the two. It can be connected by welding, bonding, threading, or directly cut from a single blank.

[0034] In this example, the precision aiming assembly uses a CCD array composed of four planar CCDs, model Kodak KAF-5100CE, each 17*13 cm in size. The assembled array forms a 17*13*13 cuboid. Adjacent CCDs are mounted vertically, forming the four sides of the cube. The center of the planar mirror surface coincides with the solid center of the cube, and the rotation axis is aligned with the straight line connecting the geometric centers of the bottom and top surfaces of the cube. In other words, each CCD plane should be parallel to and equidistant from the rotation axis of the scanning mechanism. Each CCD is equipped with a processor capable of recording the real-time spot shape. The four CCD processors can be integrated with the graphics processing unit and computing unit (mentioned later) on the same FPGA board. The FPGA used is an AMD Xilinx FPGA. model.

[0035] In this example, the graphics processing unit in the precision aiming component is implemented by pixel counting and centroid algorithm. The graphics processing unit obtains the area of ​​the elliptical spot by using pixel counting based on the shape recorded by the CCD processor, and then uses the centroid algorithm to determine the centroid of the spot. Next, it traverses all the pixels covered by the spot to find the point farthest from the centroid and records the orientation and distance of the point relative to the centroid in the CCD coordinate system (i.e., the center coordinates, the endpoint coordinates of the major axis, and the length of the semi-major axis of the ellipse).

[0036] The precision aiming component described in this example includes a calculation unit 1 for calculating relative direction and a calculation unit 2 for calculating absolute direction. Calculation unit 1 collects data provided by the image processing unit to calculate the direction of the signal light after reflection by the plane mirror. Then, using data provided by the encoder on the stepper motor, it calculates the relative direction of the signal light in the scanning coordinate system based on the law of light reflection. If the absolute direction needs to be calculated, an orientation measurement system (IMU or GNSS) can be used to perform the coordinate transformation of the signal light from the scanning coordinate system to the inertial coordinate system on calculation unit 2, ultimately determining the original direction of the signal light.

[0037] The precision aiming component described in this example also includes a main control module and a motor drive component. The main control module is used for user interaction and data transmission with external devices (such as turntable control). The motor drive controls the stepper motor, and the main control module determines whether to perform scanning, the scanning method (continuous or step), and the speed.

[0038] The precision aiming method based on spatial beam scanning described in this example is as follows:

[0039] The signal light is reflected by a plane mirror and projected onto one of the CCDs to form a light spot. The shape of the light spot is recorded by the CCD processor and transmitted to the graphics processing unit for recording. The area S of the elliptical light spot is obtained by counting pixels, as follows:

[0040]

[0041] Where m i This indicates whether a light spot is projected onto the pixel unit; if yes, it is 1, otherwise it is 0, and so on.

[0042] Determine the centroid C(x) of the light spot using the centroid algorithm. C ,y C The process of finding the centroid is as follows:

[0043]

[0044] Find the point A furthest from the centroid using pixel counting, and record its orientation (Δx, Δy) and distance d relative to the centroid in the CCD coordinate system. For the furthest point A(x...y...d...), find the point A(x...y...d...). A ,y A ),have Where Δx=x A -x C Δy=y A -y C The largest d-value obtained is the length of the major semi-axis of the elliptical spot;

[0045] The angle φ between the signal light projected onto the CCD and the CCD plane is...

[0046] The azimuth angle ψ of the signal light projected onto the CCD is... Right now:

[0047]

[0048]

[0049] Determine the direction vector R of the projected signal light. This can be represented as...

[0050] R=(cosφcosψcosφsinψsinφ) T

[0051] The normal vector n of the plane mirror at that moment is obtained from the rotation angle measurement θ obtained from the encoder. Assuming the direction of the rotation axis is parallel to the positive y-axis, and the mirror surface is initially parallel to the x-axis and pointing downwards, then the vector of the mirror normal at the rotation angle θ is...

[0052]

[0053] By solving the system of equations: R = I - 2I T The direction vector of the incident signal light I is obtained by solving nn.

[0054] Compared with existing optical communication terminal designs, this invention has the following advantages: (1) It uses spatial beam scanning to acquire signal light, thus expanding the acquisition range. (2) It uses a CCD array, which covers all the directional information of the signal light in space. (3) It can directly determine the direction of the signal light, saving the time of fine-tuning the alignment multiple times with an optical power meter.

Claims

1. A precision aiming method based on spatial beam scanning, characterized in that, Utilizing the reflective properties of light, the signal light is projected onto the CCD using a scanning component within the precision aiming assembly. Simultaneously, an integrated image processing algorithm determines the geometric parameters of the light spot, facilitating subsequent tracking. Specifically: after coarse aiming, the signal light is emitted near the receiving area with an angular deviation. A scanning mechanism reflects the signal light onto the side-mounted CCD array, projecting it onto the CCD to form a light spot. The image processing unit converts the received light spot on the CCD into geometric parameters, thereby determining the incident angle of the signal light on the CCD. Combined with the rotational position of the scanning mechanism corresponding to the light spot, a calculation unit determines the direction of the signal light, thus quickly completing the precision aiming process. The precision aiming method based on spatial beam scanning is specifically as follows: The signal light is reflected by a plane mirror and projected onto one of the CCDs to form a light spot. The shape of the light spot is recorded by the CCD processor and transmitted to the graphics processing unit for recording. The area S of the elliptical light spot is obtained by counting pixels, as follows: ， in This indicates whether a light spot is projected onto the pixel unit; if yes, it is 1, otherwise it is 0, and so on. The centroid C of the light spot is determined using the centroid algorithm. The process of finding the centroid is as follows: ， Find the point A furthest from the centroid using pixel counting, and record the point's orientation (Δx, Δy) and distance d relative to the centroid in the CCD coordinate system. For the furthest point A ( ), there are, among them , The largest d value obtained is the length of the major semi-axis of the elliptical spot; The angle φ between the signal light projected onto the CCD and the CCD plane is... ; The azimuth angle ψ of the signal light projected onto the CCD has ;Right now: ， ， The direction vector R of the projected signal light is determined as follows: ， The normal vector n of the plane mirror at that moment is obtained from the rotation angle measurement θ obtained from the encoder. Assuming the direction of the rotation axis is parallel to the positive y-axis, and the mirror surface is initially parallel to the x-axis and pointing downwards, then the vector of the mirror normal at the rotation angle θ is... ， By solving the system of equations: Solve for the direction vector of the incident signal light I.

2. The precision aiming method based on spatial beam scanning according to claim 1, characterized in that, The scanning component in the precision aiming assembly consists of a rotating shaft and a plane mirror. The plane mirror is circular with a diameter of Φ18. The angle between the mirror and the rotating shaft is 45°, and the center of the mirror is located on the straight line of the rotating shaft. The rotating shaft has a diameter of Φ12 and is controlled by a stepper motor. The stepper motor is an OUKEDA brand 20STH38EC1 motor, which is equipped with an encoder to read the real-time rotation angle during the scanning process. The surface of the mirror is coated with a reflective film, and the rotating shaft is made of 45# steel. There should be no relative movement between the two. The two components are connected by welding, bonding, threading, or directly cut from a single blank.

3. The precision aiming method based on spatial beam scanning according to claim 1, characterized in that, The precision aiming assembly consists of a CCD array composed of four planar CCDs, model Kodak KAF-5100CE, each 17*13 cm in size. The assembled array forms a 17*13*13 cuboid shape. Adjacent CCDs are vertically mounted, forming the four sides of the cube. The center of the planar reflector surface coincides with the solid center of the cube, and the direction of the rotation axis is the same as the straight line connecting the geometric centers of the bottom and top surfaces of the cube. In other words, each CCD plane should be parallel to the rotation axis of the scanning mechanism and equidistant from the rotation axis. Each CCD is equipped with a processor capable of recording the real-time spot shape. The four CCD processors, along with the graphics processing unit and computing unit, are integrated on the same FPGA board. The FPGA used is an AMD Xilinx Spartan®-7 model.

4. The precision aiming method based on spatial beam scanning according to claim 1, characterized in that, The function of the graphics processing unit in the precision aiming component is implemented by pixel counting and centroid algorithm. The graphics processing unit obtains the area of ​​the elliptical spot by using pixel counting based on the shape recorded by the CCD processor, and then uses the centroid algorithm to determine the centroid of the spot. Next, it traverses all the pixels covered by the spot to find the point farthest from the centroid and records the orientation and distance of the point relative to the centroid in the CCD coordinate system, that is, the center coordinates, the endpoint coordinates of the major axis, and the length of the semi-major axis of the ellipse.

5. The precision aiming method based on spatial beam scanning according to claim 1, characterized in that, The precision aiming component includes a calculation unit 1 for calculating relative direction and a calculation unit 2 for calculating absolute direction. Calculation unit 1 collects data from the image processing unit to calculate the direction of the signal light after reflection by the plane mirror. Then, using data from the encoder on the stepper motor, it calculates the relative direction of the signal light in the scanning coordinate system based on the laws of light reflection. If the absolute direction needs to be calculated, a direction determination system is used to perform the coordinate transformation of the signal light from the scanning coordinate system to the inertial coordinate system on the calculation unit, ultimately determining the original direction of the signal light.

6. The precision aiming method based on spatial beam scanning according to claim 1, characterized in that, The precision aiming component also includes a main control module and a motor drive component. The main control module is used for user interaction and data transmission with external devices. The motor drive controls the stepper motor, and the main control module determines whether to perform scanning, the scanning method (continuous or step), and the speed.

Images