A scanning printing device and a printing method of XY axis overlap

Abstract

The application relates to a scanning printing device and a printing method with XY-axis overlap, belonging to the field of laser processing, and the device comprises a rotating mirror module and a flat-field lens; the rotating mirror module comprises an upper rotating mirror and a lower rotating mirror, the upper rotating mirror and the lower rotating mirror are of the same size and are arranged in a spaced-apart mode, and the axial centers of the upper rotating mirror and the lower rotating mirror are taken as rotating shafts for independently controlling rotation; the incident surface of the upper rotating mirror is a plane, and the exit surface is uniformly distributed with first sawteeth; the incident surface of the lower rotating mirror is uniformly distributed with second sawteeth, and the exit surface is a plane; the first sawteeth and the second sawteeth are of the same number, structure and size. The rotation of the upper rotating mirror and the lower rotating mirror is independently controlled to realize scanning with two degrees of freedom, deflect the incident laser into exit laser with an arbitrary angle of inclination, and be equivalent to the effect of an XY-axis galvanometer, the refractive positions of the upper rotating mirror and the lower rotating mirror are very close, the requirement of the flat-field lens in correcting field curvature is reduced, and the flat-field lens with a single lens can be applied to a scanning system with a two-axis galvanometer.

Description

Technical Field

[0001] This invention belongs to the field of laser processing, specifically relating to an XY-axis overlapping scanning and printing device and printing method. Background Technology

[0002] Laser scanning processing is widely used in various industries such as laser drilling, cutting, welding, and 3D printing. Based on the scanning optical path of the galvanometer, there are currently two methods for laser scanning focusing: front-focusing galvanometer and rear-focusing galvanometer. In the rear-focusing galvanometer method, the laser beam emitted from the laser first passes through a collimating lens and a beam expander, then through a scanning galvanometer, and finally through a field lens (also called an f-theta lens or f-θ field lens) to scan onto the processing surface. The scanning galvanometer deflects the laser beam by changing the reflection angles of two mirrors along the X and Y axes, thereby controlling the laser beam to move along a specified scanning path. An f-theta lens, without altering the optical characteristics of the optical system, changes the position of the imaging beam to achieve uniform focusing of the laser spot across the entire processing surface.

[0003] The F-Theta flat field lens used in the back focusing mainly achieves two functions: first, it corrects the curved image field of the laser focus at different scanning angles in the front focusing system into a planar image field; second, it changes the relationship between the scanning angle and the scanning position of the printing work surface from F / tan(θ) to F / θ, that is, the scanning angle is proportional to the position of the light spot.

[0004] Patent applications with publication numbers CN101846791A, CN114994866A, and CN203909385U demonstrate the basic structure of an F-Theta flat-field lens. F-Theta flat-field lenses are relatively complex, large in size, and expensive. At large scanning angles of the galvanometer, the field curvature that needs correction is significant. Therefore, high-precision F-Theta flat-field lenses typically contain four or more optical elements, the main function of which is to correct the curved field curvature into a planar field.

[0005] Based on the above problems, the invention patent application CN117215050A proposes a simplified F-Theta flat field lens solution, which cites a solution using a single lens as the flat field lens. However, because a single-lens flat field lens has only one lens, its area for achieving a flat image field is very small. The galvanometer system can only be placed at a specific distance to ensure a planar image plane. Therefore, this solution is only applicable to single-axis galvanometer systems, which can only print lines on a plane. For the most commonly used two-axis galvanometer system, printing a pattern requires at least two scanning degrees of freedom. Since there is a certain distance between the rotation axes of the X and Y axis galvanometer transmitters, the aforementioned single-lens flat field lens cannot simultaneously ensure that the beams scanned by the X and Y galvanometer mirrors form a planar image field on the printing surface, making it unsuitable for two-axis galvanometer scanning systems. Summary of the Invention

[0006] The purpose of this invention is to provide an XY-axis overlapping scanning and printing device and printing method to solve the problems of traditional F-Theta plan lenses being complex in structure, large in size, and high in cost, and the inability of a single lens as an F-Theta plan lens to be used in a two-axis galvanometer scanning system.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] This invention relates to an XY-axis overlapping scanning and printing device, comprising a rotating mirror module and a flat-field lens. The rotating mirror module is positioned in front of the optical path of the flat-field lens. The rotating mirror module includes an upper rotating mirror and a lower rotating mirror, which are of the same size and spaced apart vertically. The upper and lower rotating mirrors are independently controlled to rotate, with their axes of rotation as the rotation axis. The upper rotating mirror has a planar incident surface and a uniformly distributed first serration on its exit surface. The lower rotating mirror has a uniformly distributed second serration on its incident surface and a planar exit surface. The first and second serrations are identical in number, structure, and size.

[0009] Preferably, both the first and second saw teeth are triangular saw teeth.

[0010] The present invention also relates to a printing method based on the above-mentioned XY-axis overlapping scanning printing apparatus, which includes the following steps:

[0011] S1. Define the rotation angle of the upper and lower rotating mirrors as zero when the laser beam passes through the rotating mirror module in the same direction. At the same time, define the coordinates of the laser beam on the printing surface at this time as the origin coordinates.

[0012] S2. During the printing process, the rotation angles of the upper and lower rotating mirrors are calculated in real time based on the coordinates of the printing position. The rotation angles of the upper and lower rotating mirrors are obtained by combining the following two formulas:

[0013] ,

[0014] ,

[0015] Where (x1, y1) represents the coordinates of the printing position, f(α) is the deflection angle α of the laser beam after refraction by the upper rotating mirror and the distortion of the flat field lens, and β1 and β2 are the rotation angles of the upper rotating mirror and the lower rotating mirror, respectively.

[0016] The formula for calculating the deflection angle α of the laser beam after refraction by the upward rotating mirror is:

[0017] ,

[0018] Where n is the refractive index of the upper rotating mirror, and θ is the angle between the first sawtooth inclined surface and the incident surface of the upper rotating mirror.

[0019] Preferably, the flat-field lens is a standard FTheta lens, and the expression for the function relating the deflection angle α of the laser beam after refraction by the upper rotating mirror to the distortion of the flat-field lens is as follows:

[0020] f(α) = α·f,

[0021] Where f is the focal length of a standard FTheta lens.

[0022] Preferably, during the S2 printing process, the laser beam scans at a constant speed V, and the rotational speeds of the upper and lower rotating mirrors are calculated using the following two formulas:

[0023] ,

[0024] ,

[0025] Where (x0, y0) represents the coordinates of the origin, and ω1 and ω2 represent the rotation speeds of the upper and lower rotating mirrors, respectively.

[0026] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0027] The rotating mirror module of the XY-axis overlapping scanning and printing device of the present invention includes an upper rotating mirror and a lower rotating mirror. The upper and lower rotating mirrors are the same size and are spaced apart vertically. The incident surface of the upper rotating mirror is a plane, and the exit surface is uniformly distributed with a first serration. The incident surface of the lower rotating mirror is uniformly distributed with a second serration, and the exit surface is a plane. By independently controlling the rotation of the upper and lower rotating mirrors, scanning with two degrees of freedom is achieved, and the incident laser is deflected into an exit laser with an arbitrary angle of inclination. This is equivalent to the function of an XY-axis galvanometer. The refraction positions of the upper and lower rotating mirrors are very close together, so the requirements for field curvature correction of the flat field lens can be greatly reduced, resulting in a simpler field lens structure. This also makes the single-lens flat field lens suitable for scanning systems with two-axis galvanometers. Attached Figure Description

[0028] Figure 1 Equivalent optical path diagram of a scanning and printing device with overlapping X and Y axes;

[0029] Figure 2 This is the equivalent optical path diagram of the laser beam after passing through the rotating mirror module;

[0030] Figure 3 This is a close-up view of the rotating mirror.

[0031] Illustration: 1- Rotating lens module, 2- Flat field lens, 11- Upper rotating lens, 12- Lower rotating lens, 13- First sawtooth, 14- Second sawtooth. Detailed Implementation

[0032] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments. The following embodiments are used to illustrate the invention, but are not intended to limit the scope of the invention.

[0033] See attached document Figure 1 As shown, the present invention relates to a scanning and printing device with XY axis overlap, comprising a rotating mirror module 1 and a flat field lens 2, wherein the rotating mirror module 1 is disposed in front of the optical path of the flat field lens 2.

[0034] See attached document Figure 2 As shown, the rotating mirror module 1 includes an upper rotating mirror 11 and a lower rotating mirror 12. The upper rotating mirror 11 and the lower rotating mirror 12 are of the same size and are spaced apart vertically. The rotation of the upper rotating mirror 11 and the lower rotating mirror 12 is controlled independently, with their respective axes of rotation as the rotation axis. The incident surface of the upper rotating mirror 11 is a plane, and the exit surface is evenly distributed with first serrations 13. The incident surface of the lower rotating mirror 12 is evenly distributed with second serrations 14, and the exit surface is a plane. The first serrations 12 and the second serrations 14 are both triangular serrations, and their number, structure, and size are all the same.

[0035] Assuming the distance between the upper rotating mirror 11 and the lower rotating mirror 12, including the sawtooth height, is h, then h should satisfy the distance deviation required for a flat image field of a flat-field lens. Taking a single-lens flat-field lens with a focal length of 500mm and an incident laser of 14mm as an example, when its imaging plane is flat, assuming the allowable error in the position of the deflected laser is 5mm, then... Figure 2 In the case of h ≤ 5mm, when the numerical aperture of the focused beam increases, the required value of the distance h between the upper rotating mirror 11 and the lower rotating mirror 12, including the sawtooth height, will decrease. At this time, the size of a single sawtooth can be reduced, the number of sawtooths can be increased, and the sawtooth height can be reduced to obtain a smaller h value to meet the system requirements. However, it should be ensured that the motion of the first sawtooth 12 and the second sawtooth 14 is complementary and interferes.

[0036] The incident laser enters the rotating mirror module 1, and through the upper rotating mirror 11 and the lower rotating mirror 12, the incident laser is deflected into an outgoing laser tilted at an arbitrary angle, which is equivalent to the function of a traditional XY axis galvanometer. The outgoing laser is focused and imaged onto the printing work surface by the flat field lens 2.

[0037] The printing method based on the XY-axis overlapping scanning printing device described above includes the following steps:

[0038] S1. Define the rotation angle of the upper and lower rotating mirrors as zero when the laser beam passes through the rotating mirror module 1 with the same forward and backward direction. At the same time, define the coordinates of the laser beam at the printing work surface as the origin coordinates. At this time, the inclined plane of the first sawtooth 12 is parallel to the inclined plane of the corresponding second sawtooth 14. After the laser beam is deflected by the first sawtooth 12 by α, it is deflected again by the second sawtooth 14 by -α. After the deflection angles cancel each other out, the rotation angle of the upper and lower rotating mirrors is zero when the laser beam passes through the rotating mirror module 1 with the same forward and backward direction. According to the calculation formula of the rotation angle of the upper rotating mirror 11 and the lower rotating mirror 12, x1 and y1 are both 0.

[0039] S2. During the printing process, the rotation angles of the upper rotating mirror 11 and the lower rotating mirror 12 are calculated in real time based on the coordinates of the printing position. The rotation angles of the upper rotating mirror 11 and the lower rotating mirror 12 are calculated using the following two formulas:

[0040] ,

[0041] ,

[0042] Where (x1, y1) represents the coordinates of the printing position, and f(α) is a function relating the deflection angle α of the laser beam after refraction by the upper rotating mirror to the distortion of the flat-field lens 2. It is related to the distortion of the flat-field lens 2. When the flat-field lens is a standard FTheta lens, the expression for the function relating the deflection angle α of the laser beam after refraction by the upper rotating mirror to the distortion of the flat-field lens 2 is: f(α) = α·f, where f is the focal length of the standard FTheta lens. The formula for calculating the deflection angle α of the laser beam after refraction by the upper rotating mirror is as follows: Figure 3 As shown, it is: , n is the refractive index of the upper rotating mirror, θ is the angle between the inclined surface of the first sawtooth 13 and the incident surface of the upper rotating mirror; β1 and β2 are the rotation angles of the upper rotating mirror 11 and the lower rotating mirror 12, respectively.

[0043] During the printing process, the laser beam is typically required to scan at a constant speed V. The rotational speeds of the upper and lower rotating mirrors are calculated using the following two formulas:

[0044] ,

[0045] ,

[0046] Where (x0, y0) represents the coordinates of the origin, and ω1 and ω2 represent the rotational velocities of the upper and lower rotating mirrors, respectively. As shown in the formula above, the calculated rotational velocities ω1 and ω2 can be positive or negative. A positive rotational velocity indicates clockwise rotation, and a negative rotational velocity indicates counterclockwise rotation. Therefore, this formula also determines the rotational directions of the upper and lower rotating mirrors.

[0047] The present invention has been described in detail above with reference to the embodiments, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made in accordance with the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A scanning and printing device with overlapping XY axes, characterized in that: It includes a rotating mirror module and a planar lens, with the rotating mirror module positioned in front of the optical path of the planar lens. The rotating mirror module includes an upper rotating mirror and a lower rotating mirror, which are the same size and spaced apart vertically. The upper and lower rotating mirrors are independently controlled to rotate, with their axes of rotation as the rotation axis. The upper rotating mirror has a planar incident surface and a first serration evenly distributed on its exit surface. The lower rotating mirror has a second serration evenly distributed on its incident surface and a planar exit surface. The number, structure, and size of the first and second serrations are the same.

2. The XY-axis overlapping scanning and printing apparatus according to claim 1, characterized in that: Both the first and second saw teeth are triangular saw teeth.

3. A printing method based on the XY-axis overlapping scanning printing apparatus of claim 1, characterized in that, It includes the following steps: S1. Define the rotation angle of the upper and lower rotating mirrors as zero when the laser beam passes through the rotating mirror module in the same direction. At the same time, define the coordinates of the laser beam on the printing surface at this time as the origin coordinates. S2. During the printing process, the rotation angles of the upper and lower rotating mirrors are calculated in real time based on the coordinates of the printing position. The rotation angles of the upper and lower rotating mirrors are obtained by combining the following two formulas: ， ， Where (x1, y1) represents the coordinates of the printing position, f(α) is the deflection angle α of the laser beam after refraction by the upper rotating mirror and the distortion of the flat field lens, and β1 and β2 are the rotation angles of the upper rotating mirror and the lower rotating mirror, respectively. The formula for calculating the deflection angle α of the laser beam after refraction by the upward rotating mirror is: ， Where n is the refractive index of the upper rotating mirror, and θ is the angle between the first sawtooth inclined surface and the incident surface of the upper rotating mirror.

4. The printing method of the XY-axis overlapping scanning printing device according to claim 3, characterized in that: The flat-field lens is a standard FTheta lens. The expression for the function relating the deflection angle α of the laser beam after refraction by the upward rotating mirror to the distortion of the flat-field lens is as follows: f(α) = α·f, Where f is the focal length of a standard FTheta lens.

5. The printing method of the XY-axis overlapping scanning printing device according to claim 3, characterized in that: During the S2 printing process, the laser beam scans at a constant speed V. The rotational speeds of the upper and lower rotating mirrors are calculated using the following two formulas: ， ， Where (x0, y0) represents the coordinates of the origin, and ω1 and ω2 represent the rotation speeds of the upper and lower rotating mirrors, respectively.

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