Dynamic focusing printing method based on depth-of-field layering of optical system

Abstract

The invention relates to a dynamic focusing printing method based on depth-of-field layering of an optical system, which belongs to the field of laser processing and comprises the following steps of: for a workpiece to be printed with an irregular printing working surface, dividing the printing working surface into a plurality of printing layers by taking the depth of field of the optical system as a unit in the height direction; the position of a focusing lens is adjusted, and a laser focus is adjusted to the working distance position of a certain printing layer; the galvanometer unit is adjusted to enable laser to scan on the printing layer, and then a pattern is printed on the printing working face, at the corresponding height, of the printing layer; and the steps are repeated until all the printing layers are printed. In the process of printing each printing layer, the laser focus is always in an allowable depth-of-field range, the focusing lens keeps still or moves at a constant speed according to a rule, the focal length tracking motion with high frequency response is not needed all the time, and even if the scanning speed is higher, a user does not need to worry that the focal length adjustment cannot follow up. And the printing efficiency is obviously improved, and the printing precision is not lost.

Description

Technical Field

[0001] This invention belongs to the field of laser processing, specifically relating to a dynamic focusing printing method based on optical system depth-of-field layering. Background Technology

[0002] Laser processing, such as laser cutting, laser welding, laser marking, and laser 3D printing, typically employs a single laser beam reflected by a galvanometer to scan a curved image on a two-dimensional working plane or curved surface. Laser processing is an advanced rapid manufacturing technology. Based on the galvanometer scanning optical path, current laser scanning focusing methods include front-focusing galvanometers and rear-focusing galvanometers.

[0003] In the front-focusing galvanometer method, the focusing lens is used to adjust the focal length position of the laser beam. A program compensation algorithm controls the focusing lens in real time, working in conjunction with the galvanometer scanning position to compensate for the focal length, ensuring the laser beam can be imaged onto the processing surface in real time. When the surface being processed by the laser is not planar but arbitrarily curved, only the front-focusing method can be used. The position of the focusing lens is adjusted according to the working distance at different positions on the surface being processed, ensuring the laser spot is always focused on the printing surface. A schematic diagram of the focal length of the scanning laser for a working surface of arbitrary irregular height is shown below. Figure 1 As shown, when the laser moves along the scanning direction, the focusing motor must dynamically adjust the focal length in real time to ensure that the focal length always coincides with the printing surface. In practical applications, the drive motor of the focal length adjusting lens is also limited by frequency response. In areas where the height of the printing surface changes drastically, it may not be able to respond in time to instantly change the focal length to the correct position, resulting in the laser not being properly focused at that location and affecting the laser printing or processing effect, such as... Figure 2 As shown in the image above, in order to reduce the error caused by the laser spot due to the height jump of the printed working surface, the laser scanning speed must be reduced, which greatly affects the efficiency of laser printing or processing. Summary of the Invention

[0004] The purpose of this invention is to provide a dynamic focusing printing method based on optical system depth-of-field layering to solve the problem that height jumps affect processing quality or processing speed when printing irregular height printing surfaces.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: The present invention relates to a dynamic focusing printing method based on optical system depth-of-field layering, which includes the following steps: S1. For workpieces with irregular printing surfaces, the printing surface is divided into several printing layers in the height direction, using the depth of field h of the optical system as the unit. S2. Adjust the position of the focusing lens to adjust the laser focus to the working distance position of a certain printing layer; S3. Adjust the galvanometer unit to make the laser scan the printing layer, and then print the pattern on the printing surface at the corresponding height of the printing layer; S4. Determine if all print layers have been printed. If not, return to S2; otherwise, end printing.

[0006] Preferably, when an FTheta lens is provided behind the galvanometer unit of the optical system, the printed layer in S1 is planar; in S3, the focusing lens is kept stationary, and the galvanometer unit is adjusted so that the laser scans the printed layer.

[0007] Preferably, when there is no FTheta lens behind the galvanometer unit of the optical system, the printed layer in S1 is a curved surface; in S3, the focusing lens is kept stationary, and the galvanometer unit is adjusted so that the laser scans the printed layer.

[0008] Preferably, when the galvanometer unit of the optical system is not provided with an FTheta lens, the printing working surface is continuously fitted with a curve, and the printing working surface is divided by the continuous curve; S3 keeps the focusing lens moving in a continuous manner, while adjusting the galvanometer unit so that the laser scans the printing layer.

[0009] Compared with the prior art, the technical solution provided by this invention has the following advantages: This invention relates to a dynamic focusing printing method based on optical system depth-of-field layering. For workpieces with irregular printing surfaces, the printing surface is first divided into several printing layers in the height direction using the depth of field h of the optical system as the unit. Then, the position of the focusing lens is adjusted to adjust the laser focus to the working distance position of a certain printing layer, and then the pattern is printed on the printing surface at the corresponding height of the printing layer, realizing layer-by-layer printing. During the printing of each printing layer, the laser focus is always within its allowable depth of field, and the focusing lens remains stationary or moves at a constant speed according to a certain pattern. It does not require the focusing motor to perform high-frequency focus tracking movement at all times. Even if the scanning speed is faster, there is no need to worry about the focus adjustment not keeping up, thus significantly improving printing efficiency without sacrificing printing accuracy. Attached Figure Description

[0010] Figure 1 A schematic diagram of laser printing on a working surface with irregular height; Figure 2 A schematic diagram illustrating the errors that occur during laser processing of work surfaces with irregular heights; Figure 3 This is a diagram of the optical system of the printing apparatus according to Example 1; Figure 4 This is a schematic diagram of the dynamic focusing printing process based on optical system depth-of-field layering in Example 1; Figure 5This is a diagram of the optical system of the printing apparatus involved in Examples 2 and 3; Figure 6 This is a schematic diagram of the dynamic focusing printing process based on optical system depth-of-field layering in Example 2; Figure 7 This is a schematic diagram of the dynamic focusing printing process based on optical system depth-of-field layering in Example 3. Detailed Implementation

[0011] 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.

[0012] Example 1 See attached document Figure 3 As shown, the optical system involved in this embodiment includes a focusing lens 1, a galvanometer unit 2, and an FTheta lens 3. Based on the above optical system, a dynamic focusing printing method based on optical system depth-of-field layering in this embodiment includes the following steps: S1. For workpieces with irregular printing surfaces, the printing surface is divided into several printing layers in the height direction, using the depth of field h of the optical system as the unit. Due to the presence of the FTheta lens 3, the imaging surface of the focused spot is a horizontal plane; therefore, the printing layers are also planar, such as... Figure 4 As shown; S2. Adjust the position of focusing lens 1 to adjust the laser focus to the working distance position of a certain printing layer. In order to reduce the travel of subsequent adjustments, adjust in the order of printing layers from top to bottom or from bottom to top. S3. Keep the focusing lens 1 stationary, adjust the galvanometer unit 2 so that the laser scans the printing layer, and then prints the pattern on the printing surface at the corresponding height of the printing layer; S4. Determine if all print layers have been printed. If not, return to S2; otherwise, end printing.

[0013] Example 2 See attached document Figure 5 As shown, the optical system involved in this embodiment only includes a focusing lens 1 and a galvanometer unit 2 and 3. Based on the above optical system, the dynamic focusing printing method based on optical system depth-of-field layering involved in this embodiment includes the following steps: S1. For workpieces with irregular printing surfaces, the printing surface is divided into several printing layers in the height direction, using the depth of field h of the optical system as the unit. For optical systems without an FTheta lens, when the focusing lens remains stationary to change its focal length, the imaging surface of the focused spot during galvanometer scanning is an arc surface centered on the galvanometer's reflecting surface. Therefore, the printing layer is also an arc surface, such as... Figure 6 As shown; S2. Adjust the position of focusing lens 1 to adjust the laser focus to the working distance position of a certain printing layer. In order to reduce the travel of subsequent adjustments, adjust in the order of printing layers from top to bottom or from bottom to top. S3. Keep the focusing lens 1 stationary, adjust the galvanometer unit 2 so that the laser scans the printing layer, and then prints the pattern on the printing surface at the corresponding height of the printing layer; S4. Determine if all print layers have been printed. If not, return to S2; otherwise, end printing.

[0014] Example 3 See attached document Figure 5 As shown, the optical system involved in this embodiment only includes a focusing lens 1 and a galvanometer unit 2 and 3. Based on the above optical system, the dynamic focusing printing method based on optical system depth-of-field layering involved in this embodiment includes the following steps: S1. For workpieces with irregular printing surfaces, the printing surface is divided into several printing layers in the height direction, using the depth of field h of the optical system as the unit. For optical systems without FTheta lenses, when the focusing lens remains stationary to change its focal length, the imaging surface of the focused spot during galvanometer scanning is an arc centered on the galvanometer's reflecting surface. Continuous curve fitting can be performed on the workpiece to be scanned and printed, and the workpiece can be divided into multiple layers using this continuous curve. Figure 7 As shown; S2. Adjust the position of focusing lens 1 to adjust the laser focus to the working distance position of a certain printing layer. In order to reduce the travel of subsequent adjustments, adjust in the order of printing layers from top to bottom or from bottom to top. S3. Keep the focusing lens 1 moving continuously, while adjusting the galvanometer unit 2 so that the laser scans the printing layer, and then prints the pattern on the printing surface at the corresponding height of the printing layer; since the curve of each printing layer is a continuous curve and the bending amplitude does not exceed the adjustment capability of the focusing lens 1 drive motor, there will be no tracking error in the focal length due to the abrupt change in focal length adjustment. S4. Determine if all print layers have been printed. If not, return to S2; otherwise, end printing.

[0015] 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 dynamic focus printing method based on depth of field layering of an optical system, characterized by: It comprises the following steps: S1. For the irregular workpiece to be printed on the printing work surface, the printing work surface is divided into several printing layers in the height direction with the depth of field h of the optical system as the unit; S2. Adjust the position of the focusing lens to adjust the laser focal point to the working distance position of a printing layer; S3. Adjust the galvanometer unit so that the laser scans in the printing layer, and then prints the pattern on the printing work surface corresponding to the height of the printing layer; S4. Determine whether all the printing layers are printed, if not, return to S2, if yes, end the printing.

2. The dynamic focus printing method based on optical system depth of field layering according to claim 1, characterized in that: When the galvanometer unit of the optical system is provided with a FTheta lens behind, the printing layer in S1 is a plane; S3 keeps the focusing lens stationary, and adjusts the galvanometer unit so that the laser scans in the printing layer.

3. The method of claim 1, wherein the method further comprises: determining a depth of field of the optical system; and determining a depth of field of the optical system. When the galvanometer unit of the optical system is not provided with a FTheta lens behind, the printing layer in S1 is a curved surface; S3 keeps the focusing lens stationary, and adjusts the galvanometer unit so that the laser scans in the printing layer.

4. The dynamic focus printing method based on optical system depth of field layering according to claim 1, characterized in that: When the galvanometer unit of the optical system is not provided with a FTheta lens behind, the printing work surface is fitted with a continuous curve, and the printing work surface is divided into printing layers with the continuous curve; S3 keeps the focusing lens moving in a continuous manner, and adjusts the galvanometer unit so that the laser scans in the printing layer.

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