An equal-line-velocity scanning method based on a far-field elliptical laser beam

Abstract

The present application relates to the technical field of wireless optical communication, and particularly relates to an equal linear velocity scanning method based on a far-field elliptical laser beam, comprising the following steps: measuring the ellipticity of the far-field elliptical laser beam to obtain scanning parameters; configuring a scanning overlap rate and a scanning velocity; calculating a configured spiral scanning path; and driving a mechanism to control an executor to perform scanning based on the scanning path. The present application improves scanning efficiency and significantly reduces larger control errors and missing scanning problems caused by velocity changes or inflection point deviations. The present application has strong engineering implementation and is suitable for complex interference conditions, and improves the link establishment speed and reliability of a laser communication link. The present application can be applied to scenarios of rapidly establishing a link in a wireless optical communication system, and can be popularized to related fields such as target scanning and acquisition, thereby solving the problem of low scanning efficiency of existing equal linear velocity scanning methods.

Description

Technical Field

[0001] This invention relates to the field of wireless optical communication technology, and in particular to a constant linear velocity scanning method based on a far-field elliptical laser beam. Background Technology

[0002] Wireless optical communication systems typically require a scanning and acquisition process to establish a communication link. Common scanning methods include raster scanning, rectangular spiral scanning, hexagonal scanning, and spiral scanning. Raster scanning is relatively simple in software design and implementation and can cover the scanning range well, but it has a long scanning time and low scanning efficiency.

[0003] While hexagonal scanning and spiral grating scanning can overcome the drawback of long scanning times, they exhibit significant control deviations at inflection points. Furthermore, platform vibrations and other external disturbances greatly affect spiral and hexagonal scanning, easily leading to capture failures. Besides the scanning methods mentioned above, there are also rose scanning and Lissajous scanning, but these schemes are difficult to implement in engineering, and the drastic speed changes during execution reduce control accuracy, resulting in scan gaps and easily causing capture failures. Summary of the Invention

[0004] The purpose of this invention is to provide a constant linear velocity scanning method based on a far-field elliptical laser beam, which aims to solve the problem of low scanning efficiency in existing constant linear velocity scanning methods.

[0005] To achieve the above objectives, the present invention provides a constant linear velocity scanning method based on a far-field elliptical laser beam, comprising the following steps:

[0006] The ellipticity of the far-field elliptic laser beam is measured to obtain the scanning parameters;

[0007] Configure scan overlap and scan speed;

[0008] Calculate and configure the spiral scan path;

[0009] The drive mechanism controls the actuator to perform scanning based on the scan path.

[0010] In the section "measuring the ellipticity of the far-field elliptical laser beam to obtain scanning parameters", the scanning parameters are the major and minor semi-axis of the remote elliptical laser beam.

[0011] In the phrase “the scanning parameters are the major and minor semi-axis of the remote elliptical laser beam”, the major and minor semi-axis are used as input values ​​for the initial scanning parameters.

[0012] The "Configure Scan Overlap Rate and Scan Speed" section includes the following steps:

[0013] Based on system performance and vibration conditions, set a reasonable range of scanning overlap rate to balance scanning quality and time;

[0014] The scanning speed is set based on the overall detector performance, link distance, and control system performance.

[0015] In the phrase "Based on system performance and vibration conditions, set a reasonable range of scanning overlap rate to balance scanning quality and time", the range of the scanning overlap rate is [0,1).

[0016] This invention discloses a constant linear velocity scanning method based on a far-field elliptical laser beam, comprising the following steps: measuring the ellipticity of the far-field elliptical laser beam to obtain scanning parameters; configuring the scanning overlap rate and scanning speed; calculating and configuring a helical scanning path; and a drive mechanism controlling the actuator to perform scanning based on the scanning path. This invention improves scanning efficiency and significantly reduces large control errors and missed scans caused by speed variations or inflection point deviations. It has strong engineering feasibility, adapts to complex interference conditions, and improves the link establishment speed and reliability of laser communication links. This technology is applicable to scenarios requiring rapid link establishment in wireless optical communication systems and can be extended to related fields such as target scanning and acquisition, thereby solving the problem of low scanning efficiency in existing constant linear velocity scanning methods. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a constant linear velocity scanning method based on a far-field elliptical laser beam provided by the present invention.

[0019] Figure 2 This is a flowchart for configuring the scan overlap rate and scan speed.

[0020] Figure 3 This is a schematic diagram of the scan. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] Please see Figures 1 to 3This invention provides a constant linear velocity scanning method based on a far-field elliptical laser beam, comprising the following steps:

[0023] S1 measures the ellipticity of the far-field elliptic laser beam to obtain the scanning parameters;

[0024] The scanning parameters are the major and minor semi-axis of the remote elliptical laser beam. The major and minor semi-axis are used as input values ​​for the initial scanning parameters.

[0025] Specifically, the major and minor axes ae and be of the laser beam are measured based on the actual output spot quality of the laser, and these values ​​are used as inputs for the initial scanning parameters.

[0026] S2 configures scan overlap rate and scan speed;

[0027] S21 sets a reasonable range of scanning overlap rate based on system performance and vibration conditions to balance scanning quality and time;

[0028] The range of the scan overlap rate is [0, 1].

[0029] Specifically, the scanning overlap rate is determined based on factors such as control system performance and platform vibration conditions. The scanning overlap rate is the ratio of the area repeatedly covered after one rotation of the helical scanner to the total area of ​​the previous rotation. The scanning overlap rate is usually set to a range of [0,1). When the scanning overlap rate is too small, missed scans may occur due to factors such as control system errors, platform vibration, and low beam edge power. When the scanning overlap rate is too large, the scanning time will be too long, reducing scanning efficiency.

[0030] S22 sets the scanning speed based on the overall detector performance, link distance, and control system performance.

[0031] Specifically, the scanning speed is determined based on factors such as detector performance, link distance, and control system performance. Scanning speed is the distance traveled by the actuator per unit time. The setting of the scanning speed is primarily affected by the detector's sampling frame rate. An excessively fast scanning speed will prevent the scanned end from effectively confirming the accurate position of the scanning end, resulting in acquisition failure.

[0032] S3 calculates and configures the spiral scan path;

[0033] Specifically, after completing the scanning parameter configuration, the spiral scanning path can be calculated based on the constant linear velocity scanning method of the far-field elliptical laser beam. The FIFO buffer mechanism is configured through software to avoid data loss while ensuring that the controller outputs effective control quantities at regular intervals.

[0034] The S4 drive mechanism performs scanning based on the scan path control actuator.

[0035] Specifically, the actuator is controlled by the drive mechanism to complete the constant linear velocity scanning based on the far-field elliptical laser beam according to the scanning path.

[0036] This scanning method is similar to the conventional scanning method, but the single-circle scanning speed is faster and the scanning efficiency is higher under the same scanning time increment. Its scanning curve expression is shown in [1]:

[0037]

[0038] [1] In the formula, ae and be are the major and minor semi-axis of the remote elliptical laser beam. The polar coordinate calculation expressions of the two rotation axes in the line-of-sight coordinate system o-xyz are shown in [2], where θ is the rotation angle of the helix.

[0039]

[0040] [2] In the formula, η is the scan overlap rate, usually η∈(0.2,0.6).

[0041] The total scanning time for the uncertain region is an important indicator for evaluating the performance of the scanning capture algorithm. In order to obtain the scanning time t of this scanning method, it is necessary to calculate the scanning spiral length s(θ) first. The expression for the scanning spiral length can be obtained by integrating along the scanning angle, as shown in formula [3].

[0042]

[0043] The simplified formula [3] can be represented by formula [4].

[0044]

[0045] s'(θ) can be represented by equation [5].

[0046]

[0047] In order to ensure that the dwell time of the uncertain angular domain is the same within a unit sampling time, that is, to obtain the scanning step size of the constant linear velocity, we can obtain formula [6].

[0048] s(θ)=v e ·t[6]

[0049] By taking the time partial derivative of equation [6], we obtain the differential equation in terms of θ.

[0050]

[0051] Ideal control systems are continuous models, but continuous output cannot be achieved in actual engineering. Calculating differential equations using Runge-Kutta can improve the computational accuracy of discrete systems and make the calculated output results closer to the true values. For the differential equation [7], the function expression of the fourth-order Runge-Kutta is shown in formulas [8] and [9].

[0052]

[0053] θ i+1 =θ i +h×(k1+2×k2+2×k3+k4) / 6[9]

[0054] In the formula, t0 is the starting point of the calculation time; i is the control cycle count; θ0 is the rotation angle of the starting scan point; h is the time step; k1, k2, k3, and k4 are intermediate variables in the calculation process.

[0055] For discrete control systems with a fixed sampling interval, h = 1 is usually set. After converting the single scan step length into polar coordinates, the optimal approximation θ value can be calculated by iterative method, and then the horizontal axis rotation angle x and vertical axis rotation angle y in the line-of-sight coordinate system are obtained by using equation [2] as the control quantities of the two axes of the final actuator.

[0056] The advantages and gain effects of the constant linear velocity scanning method based on a far-field elliptical laser beam provided by this invention are as follows:

[0057] I. The isolinear velocity scanning method based on a far-field elliptical laser beam provided by this invention can effectively utilize the coverage of the elliptical laser beam, avoid repeated scanning of large uncertain areas, and thus improve the link establishment efficiency of the laser communication system.

[0058] Second, the constant linear velocity scanning method based on far-field elliptical laser beam provided by this invention can improve the calculation accuracy of scanning control quantities by calculating differential equations in the Runge-Kutta manner, so that the scanning execution process will not have significant sluggishness.

[0059] Third, the constant linear velocity scanning method based on far-field elliptical laser beam provided by this invention uses an iterative method to calculate the scanning path, which can effectively reduce the computational complexity and improve the efficiency of querying and calculation.

[0060] The above-disclosed embodiments are merely preferred embodiments of the present invention's isolinear velocity scanning method based on a far-field elliptical laser beam. They should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that implementing all or part of the above embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for scanning with constant linear velocity based on a far-field elliptical laser beam, characterized in that: Includes the following steps: The ellipticity of the far-field elliptical laser beam is measured to obtain scanning parameters, which are the major and minor semi-axes of the remote elliptical laser beam. The major and minor semi-axes are used as input values ​​for the initial scanning parameters. Configure scan overlap and scan speed; Calculate and configure the spiral scan path; The drive mechanism controls the actuator to perform scanning based on the scanning path, specifically including the following: its scanning curve expression is shown in [1]: [1] In the formula, ae and be are the major and minor semi-axis of the remote elliptical laser beam; their coordinates in the line-of-sight coordinate system The polar coordinate calculation expressions for the execution quantities of the two rotation axes are shown in [2], where θ is the rotation angle of the helix; [2] In the formula, η is the scan overlap rate, which is usually η∈(0.2,0.6); The total time for scanning coverage of uncertain regions is an important indicator for evaluating the performance of scanning capture algorithms. In order to obtain the scanning time t of this scanning method, it is necessary to calculate the scanning spiral length s(θ) first. The expression for the scanning spiral length can be obtained by integrating along the scanning angle as shown in formula [3]. The simplified formula [3] can be expressed by formula [4]; in It can be represented by formula [5]; In order to ensure that the dwell time of the uncertain angular domain is the same within a unit sampling time, that is, to obtain the scanning step size of the constant linear velocity, we can obtain the formula [6]; Taking the time partial derivative of equation [6], we obtain the following about Differential equations; [7] The Runge-Kutta method can improve the computational accuracy of discrete systems and make the computational output results closer to the true values. For the differential equation [7], the function expression of the fourth-order Runge-Kutta is shown in formulas [8] and [9]. In the formula, t0 is the starting point of the calculation time; i is the control cycle count; θ0 is the rotation angle of the starting scan point; h is the time step; k1, k2, k3, and k4 are intermediate variables in the calculation process.

2. The isolinear velocity scanning method based on a far-field elliptical laser beam as described in claim 1, characterized in that: The "Configure Scan Overlap Rate and Scan Speed" section includes the following steps: Based on system performance and vibration conditions, set a reasonable range of scanning overlap rate to balance scanning quality and time; The scanning speed is set based on the overall detector performance, link distance, and control system performance.

3. The isolinear velocity scanning method based on a far-field elliptical laser beam as described in claim 1, characterized in that: In the phrase "Based on system performance and vibration conditions, set a reasonable range of scanning overlap rate to balance scanning quality and time", the range of the scanning overlap rate is [0,1).

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