Constant linear velocity scanning method based on far-field elliptic laser beam

Abstract

The invention relates to the technical field of wireless optical communication, in particular to an equal-linear-velocity scanning method based on a far-field elliptic laser beam, which comprises the following steps of: measuring the ovality of the far-field elliptic laser beam to obtain a scanning parameter; configuring a scanning overlapping rate and a scanning speed; calculating and configuring a spiral scanning path; and the driving mechanism controls the actuator to scan based on the scanning path. According to the invention, the scanning efficiency is improved, and the problems of large control error and scanning omission caused by speed change or inflection point deviation are obviously reduced. The method is high in engineering realizability, adapts to complex interference conditions, and improves the link establishment speed and reliability of a laser communication link. The technology can be applied to a scene in which a wireless optical communication system quickly establishes a link, and can be popularized to related fields such as target scanning and capturing, so that the problem of low scanning efficiency of an existing constant-linear-speed scanning method is solved.

Description

Technical Field

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

[0002] Wireless optical communication systems usually need to go through a scanning and capturing process at the beginning of establishing 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 better cover the scanning range, but it takes a long time to scan and has low scanning efficiency.

[0003] Although hexagonal scanning and spiral grating scanning can overcome the disadvantage of long grating scanning time, there will be large control deviations at the turning points. At the same time, platform vibration and other external interferences have a great impact on spiral grating scanning and hexagonal scanning, which can easily cause capture failure. In addition to the scanning methods introduced above, there are also rose scanning and Lissajous scanning, but these solutions are not easy to implement in engineering, and during the execution process, due to the drastic speed changes, the control accuracy is reduced, resulting in scanning leakage areas, which can easily cause capture failure. Summary of the invention

[0004] The object of the present invention is to provide a constant linear velocity scanning method based on a far-field elliptical laser beam, aiming to solve the problem of low scanning efficiency of the existing constant linear velocity scanning method.

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

[0006] Measure the ellipticity of the far-field elliptical laser beam and obtain the scanning parameters;

[0007] Configure scan overlap and scan speed;

[0008] Calculate and configure the spiral scanning path;

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

[0010] Among them, in “measuring the ellipticity of the far-field elliptical laser beam to obtain scanning parameters”, the scanning parameters are the major semi-axis and the minor semi-axis of the far-field elliptical laser beam.

[0011] Among them, in “the scanning parameters are the major semi-axis and the minor semi-axis of the long-range elliptical laser beam”, the major semi-axis and the minor semi-axis are used as input quantities of the initial scanning parameters.

[0012] The following steps are included in "Configuring Scan Overlap Rate and Scan Speed":

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

[0014] Set the scanning speed based on the comprehensive detector performance, link distance and control system performance.

[0015] Among them, in "according to system performance and vibration conditions, set a reasonable scanning overlap rate range to balance scanning quality and time", the value range of the scanning overlap rate is [0,1).

[0016] The present invention provides a method for scanning at a constant linear velocity 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 the scanning speed; calculating and configuring the spiral scanning path; and a driving mechanism controlling the actuator to scan based on the scanning path. The present invention improves the scanning efficiency and significantly reduces the large control errors and missed scans caused by speed changes or inflection point deviations. It has strong engineering feasibility, adapts to complex interference conditions, and improves the link establishment speed and reliability of the laser communication link. This technology can be applied to scenarios where wireless optical communication systems quickly establish links, and can also be extended to related fields such as target scanning and capture, thereby solving the problem of low scanning efficiency of existing constant linear velocity scanning methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The present invention provides a flow chart of a method for scanning a constant linear velocity based on a far-field elliptical laser beam.

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

[0020] Figure 3 It is a scanning diagram. DETAILED DESCRIPTION

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

[0022] See also Figures 1 to 3The present invention provides a method for scanning a constant linear velocity based on a far-field elliptical laser beam, comprising the following steps:

[0023] S1 measures the ellipticity of the far-field elliptical laser beam and obtains the scanning parameters;

[0024] The scanning parameters are the long semi-axis and the short semi-axis of the long-range elliptical laser beam, which are used as input quantities of the initial scanning parameters.

[0025] Specifically, the major and minor axes ae and be of the laser beam are measured according to the actual output spot quality of the laser, and the values ​​are used as input quantities of the initial scanning parameters.

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

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

[0028] The scanning overlap ratio has a value range of [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 spiral scan rotates to the total scanning area of ​​the previous scan. The value range of the scanning overlap rate is usually set to [0,1). When the scanning overlap rate is too small, it will cause missed scans due to control system errors, platform vibration, and low beam edge power. When the scanning overlap rate is too large, it will cause the scanning time to be too long, reducing the scanning efficiency.

[0030] S22 sets the scanning speed based on the comprehensive 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. The scanning speed is the distance traveled by the actuator per unit time. The setting of the scanning speed is mainly affected by the sampling frame rate of the detector. Too fast a scanning speed will cause the scanned end to be unable to effectively confirm the accurate position of the scanning end, resulting in capture failure.

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

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

[0034] S4 driving mechanism controls the actuator to scan based on the scanning path.

[0035] Specifically, the actuator is controlled by the driving 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. The scanning curve expression is shown in [1]:

[0037]

[0038] [1] In the formula, ae and be are the long and short semi-axis of the remote elliptical laser beam. The polar coordinate calculation expression of the two rotation axis execution quantity in the line of sight coordinate system o-xyz is shown in [2], and θ is the rotation angle of the helix.

[0039]

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

[0041] The total time of scanning coverage of the uncertain area 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 first calculate the scanning spiral length s(θ). The expression of 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 expressed as formula [4].

[0044]

[0045] Here, s'(θ) can be expressed by formula [5].

[0046]

[0047] In order to ensure that the dwell time in the uncertain angle region is the same within the unit sampling time, that is, to obtain a scanning step size with constant linear velocity, the formula [6] can be obtained.

[0048] s(θ)=v e t[6]

[0049] Taking the time partial derivative of equation [6], we obtain the differential equation with respect to θ.

[0050]

[0051] The ideal control system is a continuous model, but continuous output is not possible in actual engineering. Calculating differential equations using the Runge-Kutta method can improve the calculation accuracy of discrete systems and make the calculation output closer to the true value. For differential equations [7], the fourth-order Runge-Kutta function expression is shown in formulas [8] and [9].

[0052]

[0053] θ i+1 =θ i +h×(k 1 +2×k 2 +2×k 3 +k 4 ) / 6[9]

[0054] Where t0 is the starting point of the calculation time; i is the control cycle count; θ 0 is the rotation angle of the starting scanning point; h is the time step; k1, k2, k3, k4 are the intermediate variables of the calculation process.

[0055] For discrete control systems with a fixed sampling interval, h is usually set to 1. After converting the single scan step length into polar coordinates, the best approximation θ value can be calculated by iterative method, and then the horizontal axis angle x and the vertical axis angle y values ​​in the line of sight coordinate system can be obtained by using formula [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 the far-field elliptical laser beam provided by the present invention are as follows:

[0057] 1. The present invention provides a constant linear velocity scanning method based on a far-field elliptical laser beam, which can effectively utilize the coverage of the elliptical laser beam and avoid repeated scanning of a large uncertain area, thereby improving the link establishment efficiency of the laser communication system;

[0058] 2. The present invention provides a method for scanning with a constant linear velocity based on a far-field elliptical laser beam. The differential equation is calculated by the Runge-Kutta method, which can improve the calculation accuracy of the scanning control quantity and prevent the scanning execution process from being greatly delayed.

[0059] 3. The present invention provides a constant linear velocity scanning method based on a far-field elliptical laser beam, which uses an iterative method to calculate the scanning path, which can effectively reduce the complexity of the calculation and improve the efficiency of the query and calculation.

[0060] What is disclosed above is only a preferred embodiment of the constant linear velocity scanning method based on a far-field elliptical laser beam of the present invention. Of course, this cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A constant linear velocity scanning method based on a far-field elliptical laser beam, characterized in that: The following steps are involved: Measure the ellipticity of the far-field elliptical laser beam and obtain the scanning parameters; Configure scan overlap and scan speed; Calculate and configure the spiral scanning path; The driving mechanism controls the actuator to scan based on the scanning path.

2. The method for scanning with a constant linear velocity based on a far-field elliptical laser beam as claimed in claim 1, characterized in that: In “measuring the ellipticity of a far-field elliptical laser beam and obtaining scanning parameters”, the scanning parameters are the major semi-axis and the minor semi-axis of the far-field elliptical laser beam.

3. The method for scanning with a constant linear velocity based on a far-field elliptical laser beam as claimed in claim 2, characterized in that: In “the scanning parameters are the major and minor axes of the long-range elliptical laser beam”, the major and minor axes are used as input quantities for the initial scanning parameters.

4. The method for scanning with a constant linear velocity based on a far-field elliptical laser beam according to claim 1, characterized in that: In "Configuring Scan Overlap and Scan Speed", include the following steps: According to system performance and vibration conditions, set a reasonable scanning overlap rate range to balance scanning quality and time; Set the scanning speed based on the comprehensive detector performance, link distance and control system performance.

5. The method for scanning with a constant linear velocity based on a far-field elliptical laser beam as claimed in claim 4, characterized in that: In "According to system performance and vibration conditions, set a reasonable scanning overlap rate range to balance scanning quality and time", the value range of the scanning overlap rate is [0,1).

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