Error compensation device and method for a laser rotary scanning system

Abstract

The application discloses an error compensation device and method of a laser rotary scanning system and belongs to the optical technical field. The device comprises a light beam processing unit, a rotary scanning unit, an error compensation unit, a scanning track detection unit and a control unit connected with each unit respectively. The rotary scanning unit is used for circular scanning of the laser light beam processed by the light beam processing unit. The error compensation unit is used for generating a compensation vector circle and compensating the angle error of the rotary scanning unit in real time. The scanning track detection unit focuses the outgoing light to form a focused light spot and detects the scanning track of the laser on the machining plane of the workpiece to be machined. The control unit is used for synchronizing the rotary scanning unit and the error compensation unit. The application analyzes the influence of the manufacturing and installation angle error of the scanner in the rotary scanning system and provides an error compensation device and method of the laser rotary scanning system with high precision and high flexibility.

Description

Technical Field

[0001] This invention belongs to the field of optical technology, and more specifically, relates to an error compensation device and method for a laser rotation scanning system. Background Technology

[0002] Optical components such as Dove prisms, Abbe-Koni prisms, and K-shaped triple-reflector arrays, combined with a rotating motor, can form a rotary scanner, causing the emitted beam to rotate at twice its own speed. This has great potential applications in many fields, such as laser micro-hole processing, medical devices, and optical measurement. However, scanning systems based on these rotary scanners have extremely high requirements for the installation and manufacturing accuracy of the optical components themselves. These stringent operating conditions limit their practical application range, resulting in limited use in high-precision laser scanning.

[0003] Several solutions exist to reduce the impact of installation and manufacturing errors in optical components. The most common method is to design a fine-tuning mechanism for the optical component to ensure its optical axis is roughly aligned with its rotation axis. However, this adjustment process is undoubtedly time-consuming and cannot eliminate the effects of manufacturing errors. Therefore, Chinese patent CN203592234U proposes to eliminate errors by adding compensation devices to the optical path, specifically by adding an optical wedge group and a parallel plate group after the Dowell prism. The advantage of this compensation method is that it can simultaneously compensate for both manufacturing and installation errors of the Dowell prism. However, it still requires a precise adjustment mechanism for the optical wedge group and the parallel plate group, and the adjustment process is complex, time-consuming, and inconvenient in practical applications. Additionally, there are methods to reduce the impact of errors by adjusting the incident beam. For example, Chinese patent CN115815790A proposes using a dual galvanometer group to adjust the angle and position of the incident beam to improve scanning accuracy. However, this solution ignores the impact of installation errors, assuming that the preset angle between the optical axis and the rotation axis of the optical component is acceptable. It does not address the impact of installation errors in optical components. Currently, there is no flexible and convenient method to compensate for the rotational errors of optical components such as Dove prisms, Abbe-Coni prisms, and K-shaped three-reflector arrays. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an error compensation device and method for a laser rotating scanning system, which is designed to compensate for the rotational error of a laser rotating scanning system with optical elements such as Dowell prisms, Abbe-Coni prisms, and K-shaped three-reflector arrays.

[0005] A laser beam is incident along the optical axis onto a rotating scanner with a rotational speed of ω. The emitted laser beam rotates at a speed of 2ω. After being focused by a focusing lens, the effect of angular error on the scanning trajectory can be observed at the focal plane. When the incident angle α = 0°, i.e., the principal ray of the incident laser beam coincides with the optical axis, and there is no angular error, the scanning trajectory at the focal point is a point. At the focal plane, a self-rotating spot with the same size as the focal point is observed. When an angular error exists, a circular trajectory with a rotational speed of ω can be observed. This trajectory is independent of the rotational scanning characteristics of the Dove prism; it is formed by the error as the scanner rotates, so the rotational speed is ω, not 2ω. When the incident angle α ≠ 0°, in the absence of angular error, due to the scanner's rotational scanning characteristics, a circular trajectory with a rotational speed of 2ω can be observed at the focal plane; this is the target's trajectory. However, due to the presence of angular error, the circular trajectory is distorted into a Pascal's clam trajectory. The formation of Pascal's clam can be understood as the synthesis of a circular trajectory with a rotational speed of ω and a circular trajectory with a rotational speed of 2ω. The parametric equation of the trajectory can be expressed as:

[0006]

[0007] Where f is the focal length of the beam focusing unit, and θ is the rotation angle of the rotating scanner. Δα is the deflection angle of the outgoing beam caused by the angular error Δβ. It is the phase difference between the error circle trajectory and the target circle trajectory. After the Dowell prism is installed, Δα and... These are all fixed values. The error circle is expressed as a vector circle, hereinafter referred to as the error vector circle, which has a modulus Δα and an initial phase. And the scanning angular velocity is ω. Therefore, only a modulus Δα needs to be introduced. ′ =Δα initial phase Furthermore, a compensation vector circle with the same scanning angular velocity ω can compensate for the scanner's angular error.

[0008] To achieve the above objectives, the present invention provides an error compensation device for a laser rotation scanning system, comprising a beam processing unit, a rotation scanning unit, an error compensation unit, a scanning trajectory detection unit, and control units connected to each unit respectively.

[0009] The system input is a laser beam. Preferably, the laser beam is a laser beam generated by a laser source that can interact with the material being processed. This interaction includes effects such as photo-induced fracture, photo-etching, photo-crosslinking, photothermal effects, and photochemical reactions. The laser source can be a continuous laser or a pulsed laser. The exposure time or repetition frequency and laser energy of the laser source can be adjusted. The pulsed laser has one or more fixed, selectable fundamental frequencies.

[0010] The beam processing unit can adjust the angle at which the laser beam is incident on the rotating scanning unit, etc.

[0011] The rotating scanning unit can perform a circular scan of the laser beam with a certain deflection angle. During the circular scan, the beam is always on the same side near the scanning center, meaning the beam itself can rotate, and its rotational angular velocity is consistent with the circular scanning angular velocity. The rotating scanning unit can be a Dove prism driven by a motor, an Abbe-Coni prism, or a K-shaped arrangement of three reflecting mirrors.

[0012] The error compensation unit can compensate for angular errors caused by installation or manufacturing of the rotating scanning unit in real time. The error compensation unit can generate a compensation vector circle and the compensation value can be flexibly changed through the control unit. The error compensation unit can be a galvanometer, a rotating mirror, etc.

[0013] The scanning trajectory detection unit can capture and record the laser scanning trajectory generated by the scanning system. The scanning trajectory detection unit can be a CCD camera, CMOS camera, etc. Preferably, a beam focusing element can be added in front of the detection unit to focus the laser beam, forming a focused spot on the scanning trajectory detection unit. The beam focusing element can be a field lens or an objective lens.

[0014] The control unit can synchronously rotate the scanning unit and the error compensation unit, so that the angle error of the rotating scanning unit can be compensated by the error compensation unit at any rotation angle.

[0015] Beneficial effects: This device can flexibly, conveniently, and with high precision compensate for the trajectory error of a laser rotation scanning system that uses optical elements such as Dowell prisms, Abbe-Koni prisms, and K-shaped three-reflector arrays as scanners. This makes the correction of this type of scanning system faster and the maintenance simpler in practical applications, and it can be widely used in the field of high-precision laser scanning.

[0016] Based on the aforementioned system and compensation principle, this invention also proposes an error compensation method for a laser rotation scanning system. The steps are as follows:

[0017] 1. Start the rotating scanning unit and stop the error compensation unit. The incident angle α of the laser beam incident on the rotating scanning unit is adjusted to 0° by the beam processing unit. The scanning trajectory detection unit records the current circular scanning trajectory as the error vector circle and calculates the trajectory radius R of the error vector circle. e .

[0018] 2. Stop the rotating scanning unit and start the error compensation unit. Change the radius R of the compensation vector circle through the control unit. ′ e Make the scan trajectory radius R ′ e →Re At this point, the vector circular modulus Δα′→Δα generated by the error compensation unit is recorded as compensation value Δα′.

[0019] 3. Set the initial phase of the compensation vector circle With a modulus of Δα′, the rotating scanning unit and error compensation unit are activated to synchronize their rotational scanning. The scanning trajectory detection unit records the current circular scanning trajectory and calculates the radius R of the circular scanning trajectory. s Through R s Calculate the phase difference between the compensation vector circle and the error vector circle.

[0020] Preferably, the circular phase difference between two vectors can be calculated using the cosine formula.

[0021]

[0022] Preferably, the phase difference between two circular vectors can be calculated using the vector cosine theorem.

[0023]

[0024] in It is the vector of the error vector circle. It is the vector of the compensation vector circle.

[0025] 4. According to The initial phase of the compensation vector circle is set to be complementary to that of the error vector circle, with a modulus of Δα′. The rotating scanning unit and the error compensation unit are then activated to rotate and scan synchronously. At this point, the scanning trajectory detected by the scanning trajectory detection unit is a single point, and error compensation is complete.

[0026] Furthermore, the error compensation method can be implemented semi-automatically or automatically.

[0027] Compared with existing technologies, this invention proposes a high-precision, highly flexible error compensation device and method for a laser rotary scanning system by analyzing the influence of manufacturing and installation angle errors of the scanner in the rotary scanning system. This compensation method has a simple process for obtaining compensation values, and can flexibly change the compensation values ​​qualitatively and quantitatively. It achieves high compensation accuracy and is easy to maintain. If installation or manufacturing errors change after long-term system operation, the compensation values ​​need to be re-obtained and modified. It requires no complex or precise mechanical structures, has low cost in practical applications, and is very convenient. Attached Figure Description

[0028] Figure 1 A schematic diagram of the structure of the high-precision laser rotation scanning system provided by the present invention;

[0029] Figure 2This is a schematic diagram showing the installation angle error of the Daowei prism;

[0030] Figure 3 This is a schematic diagram illustrating the manufacturing angle error of the Daowei prism.

[0031] Figure 4 To ensure there is no angular error, the scanning trajectory of the Daowei prism when the laser incident angle α = 0°;

[0032] Figure 5 To account for angular errors, the scanning trajectory of the Daowei prism when the laser incident angle α = 0°;

[0033] Figure 6 To ensure there is no angular error, the scanning trajectory of the Daowei prism when the laser incident angle α≠0°;

[0034] Figure 7 To account for angular errors, the scanning trajectory of the Daowei prism when the laser incident angle α ≠ 0°;

[0035] Figure 8 This is a schematic diagram of error compensation;

[0036] Figure 9 The process for obtaining the error compensation amount;

[0037] Figure 10 The actual rotational scanning trajectory (cockle line) before error compensation;

[0038] Figure 11 The actual rotating scan trajectory (circle) after error compensation;

[0039] Reference numerals: 1. Beam processing unit; 2. Rotation scanning unit; 3. Error compensation unit; 4. Scan trajectory detection unit; 5. Control unit; 6. Laser beam. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0041] This embodiment provides a high-precision laser rotation scanning system, such as... Figure 1As shown, the system includes a beam processing unit 1, a rotating scanning unit 2, an error compensation unit 3, a scanning trajectory detection unit 4, and a control unit 5. The system input is a light beam, preferably a laser beam 6, generated by a laser source. This laser beam interacts with the processed material through photo-induced fracture, photo-etching, photo-crosslinking, photothermal, and photochemical reactions. The wavelength of the laser source is preferably between 800 nm and 1500 nm, the repetition frequency is preferably between 10 kHz and 10 MHz, and the laser power is preferably between 0.1 W and 1000 W. The beam processing unit 1 can adjust the incident angle of the laser beam onto the rotating scanning unit. The beam processing unit 1 can be one or more manually adjustable mirrors; it can also be one or more electrically adjustable mirrors, such as galvanometers. The rotating scanning unit 2 can perform a circular scan of the laser beam with a certain deflection angle. During the circular scan, the beam closest to the scanning center is on the same side, meaning the beam itself can rotate, and the rotation angular velocity is consistent with the circular scanning angular velocity. The rotating scanning unit 2 can be a Dowell prism, an Abbe-Coni prism, or a K-shaped arrangement of three reflecting mirrors driven by a motor. The error compensation unit 3 can compensate for angular errors in the rotating scanning unit due to installation or manufacturing defects in real time. The error compensation unit 3 can generate a compensation vector circle and its compensation value can be flexibly changed by the control unit. The error compensation unit 3 can be a galvanometer, a rotating mirror, etc. The scanning trajectory detection unit 4 can capture and record the laser scanning trajectory generated by the scanning system. The scanning trajectory detection unit 4 can be a CCD camera, a CMOS camera, etc. The control unit 5 can synchronously rotate the scanning unit 2 and the error compensation unit 3, ensuring that the angular error of the rotating scanning unit is compensated by the error compensation unit at any rotation angle.

[0042] Figure 2 This is a schematic diagram of the installation angle error of the Daowei prism. After the Daowei prism 20 is installed, there is an installation angle error 23 between its central axis 22 and rotation axis 21.

[0043] Figure 3 This is a schematic diagram of the manufacturing angle error of the Dowell prism. During the manufacturing process of the Dowell prism 20, the actual angle between the refractive surface 25 and the reflective surface 27 is not the ideal 45°, and there is a manufacturing angle error 26 between it and the ideal refractive surface 24.

[0044] like Figure 4 As shown, when there is no angular error and the laser incident angle α = 0°, the scanning trajectory of the Dowell prism captured by the scanning trajectory detection unit 4 should be a point 42a. Figure 5 As shown, when there is an angular error and the laser incident angle α = 0, the scanning trajectory of the Daowei prism captured by the scanning trajectory detection unit 4 becomes a circular trajectory 40b. The circular trajectory 42b is caused by the angular error, and its trajectory scanning angular velocity is consistent with the rotation speed of the Daowei prism 20. Figure 6There is no angular error. When the laser incident angle α≠0°, the scanning trajectory of the Dowell prism captured by the scanning trajectory detection unit 4 should be a circular trajectory 42c with an angular velocity twice the rotational speed of the Dowell prism. This is the rotational scanning characteristic of the Dowell prism, and the circular trajectory 42c is the target trajectory. However, in practical applications, installation angle error 23 and manufacturing angle error 26 are unavoidable. When the laser incident angle α≠0°, the scanning trajectory of the Dowell prism captured by the scanning trajectory detection unit 4 is a Pascal's cirrus line 42d, as shown below. Figure 7 As shown, compensation is needed to transform the scan trajectory 42d into the ideal target trajectory 42c. The parametric equation of the scan trajectory 42d can be expressed as:

[0045]

[0046] Where f is the focal length of the beam focusing element, and θ is the rotation angle of the rotating scanner. Δα is the deflection angle of the outgoing beam caused by the angular error 23. It is the phase difference between the error circle trajectory and the target circle trajectory. After the Dowell prism is installed, Δα and... They are all fixed values. For example... Figure 8 As shown, the error circle is expressed as a vector circle 28, which has a modulus Δα and an initial phase. And the scanning angular velocity is ω. Therefore, only a modulus Δα needs to be introduced. ′ =Δα initial phase Furthermore, the compensation vector circle 30, which has the same scanning angular velocity as ω, can compensate for the scanner's angular error.

[0047] based on Figure 1 The present invention proposes a high-precision, high-flexibility error compensation method for a laser rotating scanning system, based on the described system and compensation principle. Figure 9 As shown, the steps are as follows:

[0048] Step S1: Start the rotating scanning unit 2 and stop the error compensation unit 3. The incident angle α = 0° is adjusted to the rotating scanning unit 2 by the beam processing unit 1. The scanning trajectory detection unit 4 records the current circular scanning trajectory and calculates the radius R of the circular trajectory. e .

[0049] Step S2: Stop the rotating scanning unit 2 and start the error compensation unit 3. Change the radius R of the compensation vector circle via the control unit 5. ′ e Make the scan trajectory radius R ′ e →R e At this point, the vector circular modulus Δα′→Δα generated by the error compensation unit is recorded as compensation value Δα′.

[0050] Step S3: Set the initial phase of the compensation vector circle. With a modulus of Δα′, the rotating scanning unit 2 and error compensation unit 3 are activated to perform synchronous rotating scanning. The scanning trajectory detection unit 4 records the current circular scanning trajectory and calculates the radius R of the circular trajectory. s R s It is a vector circle formed by the combination of the error vector circle and the compensation vector circle. The phase difference between the two vector circles can be calculated using the cosine formula.

[0051]

[0052] Step S4: Set the initial phase of the galvanometer vector circle. (or With a modulus of Δα′, the rotating scanning unit 2 and the error compensation unit 3 are activated to rotate and scan synchronously. At this time, the scanning trajectory detected by the scanning trajectory detection unit 4 is a single point, and the error compensation is completed.

[0053] Figure 10 The actual rotational scan trajectory before error compensation. Figure 11 It is the actual rotational scanning trajectory after error compensation using the compensation method described in this invention.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An error compensation method for a laser rotating scanning system, applied to an error compensation device for the laser rotating scanning system, the error compensation device comprising a beam processing unit, a rotating scanning unit, an error compensation unit, a scanning trajectory detection unit, and control units respectively connected to each unit; the beam processing unit is used to adjust the angle at which the laser beam is incident on the rotating scanning unit; the rotating scanning unit is used to perform a circular scan of the laser beam passing through the beam processing unit to obtain an outgoing light; the error compensation unit is used to generate a compensation vector circle to compensate for the angle error of the rotating scanning unit in real time; the scanning trajectory detection unit focuses the outgoing light to form a focused spot and detects on the processing plane of the workpiece to obtain the laser scanning trajectory; the control unit is used to synchronize the rotating scanning unit and the error compensation unit, so that the angle error of the rotating scanning unit can be compensated by the error compensation unit at any rotation angle; characterized in that... include: starting the rotation scanning unit; adjusting, by the light beam processing unit, an incident angle of a laser light beam incident to the rotation scanning unit ; the scan trajectory detection unit records the current circular scan trajectory as an error vector circle and calculates a trajectory radius of the error vector circle ; stopping the rotation scanning unit; The error compensation unit is activated; the modulus of the compensation vector circle generated by the error compensation unit is changed through the control unit, thus adjusting the radius of the scanning trajectory. ,Record Modulus at time Stop error compensation unit; Set the phase of the compensation vector circle to The rotating scanning unit and error compensation unit are activated, enabling them to rotate and scan synchronously. The scanning trajectory detection unit records the current circular scanning trajectory and calculates its radius. ;pass Calculate the phase difference between the compensation vector circle and the error vector circle. ; according to Set the phase of the compensation vector circle to be complementary to that of the error vector circle, and set the modulus to be... The rotating scanning unit and the error compensation unit are activated to rotate and scan synchronously. At this time, the scanning trajectory detected by the scanning trajectory detection unit is a single point, and the error compensation is completed.

2. The error compensation method of claim 1, wherein, Phase difference between compensation vector circle and error vector circle .

3. The error compensation method of claim 1, wherein, Phase difference between the compensation vector circle and the error vector circle ,in It is the vector of the error vector circle. It is the vector of the compensation vector circle.

4. The error compensation method of claim 1, wherein, The rotating scanning unit is a Dowell prism, an Abbe-Coni prism, or a K-shaped arrangement of three reflecting mirrors driven by a motor.

5. The error compensation method of claim 1, wherein, The error compensation unit is a galvanometer or a rotating mirror.

6. The error compensation method of claim 1, wherein, The scanning trajectory detection unit includes a beam focusing element and a viewing element. The beam focusing element is a field lens or an objective lens, and the viewing element is a CCD camera or a CMOS camera.

7. The error compensation method of claim 1, wherein, After compensation, the scanning trajectory of the laser rotating scanning system changes from a line to a circle.

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