A galvanometer scanning system with simplified flat-field lens

Abstract

The present invention relates to a galvanometer scanning system for simplifying a flat field lens, belonging to the technical field of laser 3D printing equipment, and comprising an auxiliary lens, a scanning galvanometer and a flat field lens group arranged in sequence on a laser beam path; the focal length of the auxiliary lens is f1, the spacing between the auxiliary lens and the scanning galvanometer is L1, the maximum inclination angle beam optical path between the scanning galvanometer and the flat field lens group is L2, and the focal length of the auxiliary lens satisfies the following formula: f1<L1+L2; the flat field lens group comprises at least one convex lens. After the light beam of the present invention passes through the auxiliary lens, the image distance of the inclined light beam becomes longer than the light beam on the optical axis, so that the light beam length between the flat field lens group and the printing work surface is greater than the focal length of the flat field lens group, thereby changing the image field after the flat field lens group into a plane image field, and no longer achieving the purpose of changing the curved image field into a plane image field by increasing the number of lenses in the flat field lens group, thereby simplifying the structure of the flat field lens group and reducing the volume.

Description

Technical Field

[0001] The invention belongs to the technical field of laser 3D printing equipment, and in particular relates to a galvanometer scanning system of a simplified flat-field lens. Background Art

[0002] Galvanometer scanning processing is widely used in laser drilling, cutting, welding, 3D printing and other industries. The principle is to use a galvanometer to reflect the laser beam and perform image scanning and printing on the printing work surface. There are two current laser scanning focusing methods: front focusing galvanometer (PRE-SCAN) and post focusing galvanometer (POST-SCAN). The front focusing galvanometer focuses after scanning, and the post focusing galvanometer focuses before scanning.

[0003] In the front focusing solution, the laser beam first passes through the collimator and beam expander, then through the dynamic focusing lens that can move in real time, and then through the galvanometer to reflect the laser to achieve the scanning and printing of the laser on the printing work surface. This solution requires the use of a program compensation algorithm to control the focusing lens in real time, and to compensate the focal length with the position of the galvanometer scanning to achieve dynamic focusing, so that the laser beam can be imaged on the printing work surface in real time. The dynamic focusing device requires the lens to move back and forth more than 10 billion times to compensate the focal length within a one-year working period, so it has very high requirements for the stability of the voice coil motor and the linear guide. Based on the actual performance of current products in the industry, the front focusing dynamic focusing solution is less stable than the rear focusing flat field lens solution. In addition, the front focusing system is limited by the principle of the optical system. When it scans the printed pattern, the beam vertically scans the center of the pattern and the beam tilts the edge of the pattern. The spot deformation is close to twice that of the rear focusing system. Therefore, the quality of the edge printing of its parts is worse.

[0004] The post-focusing galvanometer method means that the laser beam emitted by the laser first passes through the collimator, beam expander, scanning galvanometer, and finally scans the processing surface through the field lens (also called f-theta flat field lens, f-θ field lens). The scanning galvanometer realizes the deflection of the laser beam by changing the reflection angle of the two mirrors in the X and Y axis directions, and then controls the laser beam to move along the specified scanning path. The f-theta flat field lens changes the position of the imaging beam without changing the optical characteristics of the optical system, so as to achieve uniform focus of the light spot on the entire processing surface.

[0005] The F-Theta flat-field lens used in post-focusing mainly achieves two functions. One is to correct the curved image field of the laser focus at different scanning angles in the front-focusing system into a flat image field. The other is to change 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 light spot position. In practical applications, the function of correcting the curved image field is more important in the F-Theta flat-field lens. This function can save the motor and driver for focusing, making the control system simpler.

[0006] The structure of the f-theta flat-field lens is shown in the Chinese patent application publication numbers CN101846791A, CN114994866A and the authorization announcement number CN203909385U. Since the value of the field curvature that needs to be corrected is very large under the large scanning angle of the galvanometer, the high-precision F-Theta flat-field lens optical lenses usually contain more than 4 pieces, resulting in a relatively complex structure and a large size of the F-Theta flat-field lens. Summary of the invention

[0007] The object of the present invention is to provide a galvanometer scanning system with a simplified flat-field lens, so as to solve the problems of the F-Theta flat-field lens used in the existing post-focusing galvanometer scanning system being complex in structure and large in size.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] The present invention relates to a galvanometer scanning system of a simplified flat field lens, which comprises an auxiliary lens, a scanning galvanometer and a flat field lens group which are sequentially arranged on a laser beam path; the focal length of the auxiliary lens is f1, the spacing between the auxiliary lens and the scanning galvanometer is L1, the maximum inclination angle beam optical path between the scanning galvanometer and the flat field lens group is L2, and the focal length of the auxiliary lens satisfies the following formula: f1<L1+L2; the flat field lens group comprises at least one convex lens.

[0010] Preferably, the auxiliary lens is a concave lens, and the focal length f1 of the auxiliary lens is less than 0.

[0011] Preferably, the auxiliary lens is a convex lens, and the focal length of the auxiliary lens is 0<f1<L1+L2.

[0012] Preferably, the field-flattening lens group includes 1 to 2 convex lenses.

[0013] Preferably, the field flattening lens group comprises two convex lenses, and the two convex lenses are arranged in parallel and spaced apart.

[0014] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0015] The galvanometer scanning system of the simplified flattening lens of the present invention is an improvement on the post-focusing galvanometer scanning system. An auxiliary lens is arranged in front of the scanning galvanometer, and the focal length f1 of the auxiliary lens, the spacing L1 between the auxiliary lens and the scanning galvanometer, and the maximum inclination angle light beam optical path L2 between the scanning galvanometer and the flattening lens group satisfy f1<L1+L2. After the light beam passes through the auxiliary lens, the image distance of the inclined light beam becomes longer than the light beam on the optical axis, so that the light beam length between the flattening lens group and the printing work surface is greater than the focal length of the flattening lens group, thereby changing the image field behind the flattening lens group into a flat image field, and the purpose of changing the curved image field into a flat image field is no longer achieved by increasing the number of lenses in the flattening lens group, thereby simplifying the structure of the flattening lens group and reducing the volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural diagram of a galvanometer scanning system of a simplified flat-field lens according to the present invention;

[0017] Figure 2 A simplified optical path schematic diagram of a galvanometer scanning system of a simplified flat-field lens according to the present invention;

[0018] Figure 3 This is an optical simulation diagram of using a single flat field lens without an auxiliary lens;

[0019] Figure 4 This is an optical simulation diagram of using a single flat field lens when an auxiliary lens is provided in Example 2;

[0020] Figure 5 This is an optical simulation diagram of using a single flat field lens when an auxiliary lens is provided in Example 3;

[0021] Figure 6 This is an optical simulation diagram of using a single flat field lens when an auxiliary lens is provided in Example 4;

[0022] Figure 7 This is a distortion curve diagram of the F / θ relationship in Example 4.

[0023] Figure numerals: 1-laser beam, 2-auxiliary lens, 3-scanning galvanometer, 4-flat field lens group, 41-convex lens, 5-printing working surface. DETAILED DESCRIPTION

[0024] The present invention is described in detail below, and the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] For the scanning system without auxiliary lens 2 and with flat-field lens group 4 being a convex lens, the incident laser beam is collimated laser beam 1 with a diameter of 20 mm. The laser beam 1 reflected by scanning galvanometer 3 has a scanning angle of ±20°, a wavelength of 1064 nm, and a working distance of 600 mm. A single convex lens 41 is used for flat-field lens design. The final optical simulation optimization results are shown in FIG. Figure 3 The optical path parameters are shown in Table 1:

[0027] Table 1: Optical path parameter diagram when no auxiliary lens is set and the flat field lens group is a convex lens

[0028]

[0029] It can be seen that if a single lens is used to correct a curved image field into a flat image field, the correction of the image field curvature by the single lens is limited, and ultimately the curved image field cannot be corrected into a flat image field, and the curvature radius of the image field after correction is still 860 mm. In this regard, in this embodiment, while maintaining the design of the flat field lens group 4 using a single convex lens 41, an auxiliary lens 2 is arranged in front of the scanning galvanometer 3 to improve the scanning system.

[0030] Example 2

[0031] See attached Figure 1 and 2 As shown, this embodiment is one of the improved solutions based on embodiment 1. This embodiment involves a galvanometer scanning system with a simplified flat-field lens, which includes an auxiliary lens 2, a scanning galvanometer 3, and a flat-field lens group 4, which are sequentially arranged on the path of the laser beam 1. The laser beam 1 is a collimated parallel beam, and the collimation is achieved by a collimator, which is a prior art and does not belong to the protection scope of the present invention. Therefore, the collimator is not drawn in the attached drawings. The focal length of the auxiliary lens 2 is f1, the distance between the auxiliary lens 2 and the scanning galvanometer 3 is L1, the maximum inclination angle beam optical path between the scanning galvanometer 3 and the flat-field lens group 4 is L2, and the maximum inclination angle beam optical path between the flat-field lens group 4 and the printing work surface 5 is L3. According to the lens imaging formula, there is the following relationship: Referring to Example 1, for an inclined light beam, the auxiliary lens 1 needs to make the image distance of the inclined light beam longer than the light beam on the optical axis on the basis of Example 1, that is, L3>f2, so that the image field behind the flattening lens group 4 can be turned into a plane, so the above formula must satisfy: Therefore, the focal length of the auxiliary lens satisfies the following formula: f1<L1+L2.

[0032] In this embodiment, the auxiliary lens 2 is a concave lens with a focal length f1 < 0; the flat field lens group is a convex lens 41 for flat field design. Figure 4The optical path parameters are shown in Table 2:

[0033] Table 2: Optical path parameter diagram of the scanning system involved in Example 2

[0034]

[0035] Therefore, after adding a single concave lens at the position of the auxiliary lens 2, the correction capability of the field flattening lens group 4 for the curved image field is greatly improved, and the field curvature can be perfectly corrected by using a single convex lens 41 as the field flattening lens group 4.

[0036] Example 3

[0037] In this embodiment, the auxiliary lens 2 is a convex lens, and the focal length satisfies 0<f1<L1+L2; a convex lens 41 is used to design the flat field lens group 4, and the optical simulation diagram is as follows: Figure 5 The optical path parameters are shown in Table 3:

[0038] Table 3: Optical path parameter diagram of the scanning system involved in Example 3

[0039]

[0040] In this embodiment, after adding a single convex lens at the position of the auxiliary lens 2, the field flattening lens group 4 can also use a single convex lens 41 to perfectly correct the image field curvature, but its ability to correct geometric aberrations is slightly worse than the concave lens in Example 2. In actual use, it is recommended to use a concave lens or a concave lens group as the auxiliary lens 2.

[0041] Example 4

[0042] In this embodiment, the auxiliary lens 2 is a concave lens, and the focal length satisfies f1<0; two convex lenses 41 are used to design the flat field lens group 4, and the optical simulation diagram is as follows: Figure 6 The optical path parameters are shown in Table 4:

[0043] Table 4: Optical path parameter diagram of the scanning system involved in Example 4

[0044]

[0045] In this embodiment, a single concave lens is added at the position of the auxiliary lens 2, and the field flattening lens group 4 uses two convex lenses 41, which not only realizes the correction of the curved image field, but also the distortion correction of the F / θ relationship, and also meets the use requirements. That is, after adding an auxiliary lens at the position of the auxiliary lens 2 through this solution, only two convex lenses 41 are needed to design and realize a high-quality F-Theta field flattening lens. Figure 7This is a distortion curve diagram of the F / θ relationship in Example 4. The distortion value of the F / θ relationship in the full field of view does not exceed ±0.01%. This embodiment is a lens with a printing format of 360*360mm. In the entire field of view, the maximum deviation of the distortion of the image at the printing work surface and the F / θ relationship does not exceed 180mm*0.01%=18um, which meets the accuracy requirements of laser scanning printing for patterns.

[0046] The present invention is described in detail above in conjunction with the embodiments, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A galvanometer scanning system with a simplified flat-field lens, characterized in that: It includes an auxiliary lens, a scanning galvanometer and a flat field lens group which are sequentially arranged on the laser beam path; the focal length of the auxiliary lens is f 1. The distance between the auxiliary lens and the scanning galvanometer is L1, the maximum inclination beam optical path between the scanning galvanometer and the flat field lens group is L2, and the focal length of the auxiliary lens satisfies the following formula: f 1<L1+ L2, so that after the laser beam passes through the auxiliary lens, the image distance of the inclined light beam becomes longer than the light beam on the optical axis, so that the light beam length between the flattening lens group and the printing work surface is greater than the focal length of the flattening lens group, thereby changing the image field after the flattening lens group into a plane image field; the flattening lens group includes at least one convex lens.

2. The galvanometer scanning system of the simplified flat-field lens according to claim 1, characterized in that: The auxiliary lens is a concave lens, and the focal length of the auxiliary lens is f 1<0.

3. The galvanometer scanning system of the simplified flat-field lens according to claim 1, characterized in that: The auxiliary lens is a convex lens, and the focal length of the auxiliary lens is 0< f 1<L1+ L2.

4. The galvanometer scanning system of the simplified flat-field lens according to claim 1, characterized in that: The field flattening lens group includes 1 to 2 convex lenses.

5. The galvanometer scanning system of the simplified flat-field lens according to claim 1, characterized in that: The field flattening lens group comprises two convex lenses, which are arranged in parallel and spaced apart.

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