Large relative aperture telecentric scanning field lens system

Abstract

The present application discloses a large relative aperture telecentric scanning field lens system, comprising: a negative lens, a first positive meniscus lens, a second positive meniscus lens, a positive lens, a third positive meniscus lens, a fourth positive meniscus lens and a negative meniscus lens, which are sequentially arranged along the optical axis direction from the entrance pupil position. The present application can avoid the problem of insufficient telecentricity caused by the difference in the installation positions of the two reflectors in the existing two-dimensional scanning galvanometer system, and can achieve telecentric focusing and telecentric scanning processing with large scanning angles and large focusing angles. The present application has a wide range of applications, including but not limited to the cutting and processing of hard transparent materials by laser Bessel beams, and the movement operation of optical tweezers.

Description

Technical Field

[0001] The present application relates to a laser scanning field lens, belonging to the field of optics, and in particular to a large relative aperture telecentric scanning field lens system. Background Art

[0002] The laser scanning field lens is the core optical component of the laser processing system, which is used to focus the laser. The laser can be controlled to change direction through the galvanometer or optical wedge at the front end, and the focus point position can be moved by focusing the field lens. This feature is used for laser scanning processing. In some applications where high quality of processing cuts is required, the laser beam is required to be incident on the processing surface in a vertical direction. The edge scanning light of the existing field lens optical system has a large principal light angle, which will produce a slope effect during processing, such as the light spot becomes larger, resulting in a decrease in energy density and affecting the processing quality; in some application scenarios, such as laser drilling, the large-angle focused light beam is also easily blocked by the surface structure of the workpiece, affecting the drilling depth and aperture ratio, so it is necessary to design a special telecentric scanning system to solve the above problems. Summary of the invention

[0003] The present application provides a large relative aperture telecentric scanning field lens system, which, in response to laser processing requirements, enables wide range movement of the focus point position through field lens focusing, and the main ray (center ray) of the focused light beam can be perpendicular to the processing surface.

[0004] The large relative aperture telecentric scanning field lens system described in the present application comprises: a negative lens, a first positive meniscus lens, a second positive meniscus lens, a positive lens, a third positive meniscus lens, a fourth positive meniscus lens and a negative meniscus lens, which are sequentially arranged along the optical axis direction from the entrance pupil position; wherein the concave surface of the negative lens, the convex surface of the third positive meniscus lens and the convex surface of the fourth positive meniscus lens are on the side close to the entrance pupil position, and the convex surface of the first positive meniscus lens, the convex surface of the second positive meniscus lens and the concave surface of the negative meniscus lens are on the side away from the entrance pupil position; when the light beam passes through the large relative aperture telecentric scanning field lens system, the main light ray is perpendicular to the processing surface.

[0005] Preferably, the negative lens is a plano-concave lens.

[0006] Preferably, the negative lens and the negative meniscus lens are in a nearly symmetrical relationship, and the focal length ratio between the two is between 0.5 and 1.5.

[0007] Preferably, the first positive meniscus lens and the fourth positive meniscus lens are in a nearly symmetrical relationship, and a focal length ratio between the two is between 0.5 and 1.5.

[0008] Preferably, the second positive meniscus lens and the third positive meniscus lens are in a nearly symmetrical relationship, and the focal length ratio between the two is between 0.5 and 1.5.

[0009] Furthermore, the operating wavelength range of the large relative aperture telecentric scanning field lens system is 1.06 to 1.1 microns, which can be extended to 0.4 to 0.7 microns.

[0010] Furthermore, the scanning angle of the large relative aperture telecentric scanning field lens system is -20° to 20°.

[0011] Furthermore, the relative aperture F value (focal length of the system / incident beam diameter) of the large relative aperture telecentric scanning field lens system is 1.8 to 3.2.

[0012] Preferably, the relative aperture F value is 2.6.

[0013] Furthermore, the large relative aperture telecentric scanning field lens system performs scanning with a changed beam angle in the range of (-0.5f, 0.5f) near the entrance pupil position, where f is the focal length of the field lens, and can obtain a scanning focusing spot with a near vertical incidence at the rear end.

[0014] The beneficial effects of this application include:

[0015] 1) This application avoids the problem of insufficient telecentricity in the prior art and can realize telecentric scanning processing;

[0016] 2) The scanning field lens system provided in this application is suitable for telecentric focusing with large scanning angles and large focusing angles;

[0017] 3) This application can be used in the following application scenarios, including but not limited to: laser drilling, laser cutting, laser engraving, laser metal 3D printing, laser Bessel beam cutting and processing of hard transparent materials, and mobile operation of optical tweezers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the large relative aperture telecentric scanning field lens system described in this application;

[0019] Figure 2 This is a schematic diagram of the structure of a large relative aperture telecentric scanning system in one embodiment of the present application;

[0020] Figure 3 It is a distribution diagram of different field of view points of ray tracing in one embodiment of the present application;

[0021] Figure 4 It is a field curvature and distortion curve diagram of an implementation manner of the present application.

[0022] List of parts and reference numerals:

[0023] M1-entrance pupil position, L1-negative lens, L2-first positive meniscus lens, L3-second positive meniscus lens, L4-positive lens, L5-third positive meniscus lens, L6-fourth positive meniscus lens, L7-negative meniscus lens. DETAILED DESCRIPTION

[0024] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0025] The large relative aperture telecentric scanning field lens system of the present application includes a scanning field lens, wherein the scanning field lens includes: a negative lens L1, a first positive meniscus lens L2, a second positive meniscus lens L3, a positive lens L4, a third positive meniscus lens L5, a fourth positive meniscus lens L6, and a negative meniscus lens L7. Figure 1 As shown, the entrance pupil position M1 and the scanning field lens group are arranged in sequence from left to right along the optical axis direction, wherein the entrance pupil position is generally also the galvanometer position.

[0026] The negative lens L1 and the negative meniscus lens L7 are close to a symmetrical relationship, and their focal length ratio f1 / f7 is between 0.5 and 1.5. The first positive meniscus lens L2 and the fourth positive meniscus lens L6 are close to a symmetrical relationship, and their focal length ratio f2 / f6 is between 0.5 and 1.5. The second positive meniscus lens L3 and the third positive meniscus lens L5 are close to a symmetrical relationship, and their focal length ratio f3 / f5 is between 0.5 and 1.5.

[0027] According to one embodiment of the present application, a typical incident laser wavelength is 1.06 to 1.1 microns, and can also be extended to 0.4 to 0.7 microns.

[0028] According to an embodiment of the present application, the scanning field lens system satisfies a scanning angle of -20° to 20°. The relative aperture F value (focal length / incident beam diameter) ranges from 1.8 to 3.2, and is approximately 2.6 in this embodiment.

[0029] According to one embodiment of the present application, the scanning field lens system, if it satisfies the scanning of changing the beam angle within the range of (-0.5f, 0.5f) near the entrance pupil position, can obtain a scanning focusing spot with a near vertical incidence at the rear end.

[0030] According to one implementation of the present application, Figure 2 The telecentric scanning field lens system shown in the figure includes a negative lens L1, a first positive meniscus lens L2, a second positive meniscus lens L3, a positive lens L4, a third positive meniscus lens L5, a fourth positive meniscus lens L6 and a negative meniscus lens L7 arranged in sequence along the optical axis from the position of the entrance pupil M1. The specific parameters of the optical system in this embodiment are shown in Table 1 below.

[0031] Table 1

[0032]

[0033]

[0034] Surface 2 in the above table is the second surface of L2; the focal plane is the processing surface, and the outer diameter of the processing surface represents the maximum processing size (radius), which is related to the angle of the incident light beam.

[0035] Figure 3 This is a distribution diagram of points in different viewing fields by ray tracing of this embodiment, showing that the root mean square distribution radius of the focused light spots in all viewing fields is less than 8.7 microns.

[0036] Figure 4 2 is the field curvature and distortion curve of this embodiment. The maximum f-θ distortion of this system is 0.57%.

[0037] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A large relative aperture telecentric scanning field lens system, characterized in that: The system comprises: a negative lens, a first positive meniscus lens, a second positive meniscus lens, a positive lens, a third positive meniscus lens, a fourth positive meniscus lens and a negative meniscus lens, which are arranged in sequence along the optical axis from the entrance pupil position; Among them, the concave surface of the negative lens, the convex surface of the third positive meniscus lens, and the convex surface of the fourth positive meniscus lens are on the side close to the entrance pupil position, and the convex surface of the first positive meniscus lens, the convex surface of the second positive meniscus lens, and the concave surface of the negative meniscus lens are on the side away from the entrance pupil position; the negative lens and the negative meniscus lens are close to a symmetrical relationship, and the focal length ratio between the two is between 0.5 and 1.5; the first positive meniscus lens and the fourth positive meniscus lens are close to a symmetrical relationship, and the focal length ratio between the two is between 0.5 and 1.5; the second positive meniscus lens and the third positive meniscus lens are close to a symmetrical relationship, and the focal length ratio between the two is between 0.5 and 1.5; The system's scanning angle is -20°~20°; The relative aperture F value of the system is 1.8~3.2; The system performs scanning with a changed beam angle in the range of (-0.5f, 0.5f) near the entrance pupil position, where f is the focal length of the field lens; When the light beam passes through the large relative aperture telecentric scanning field lens system, the main light beam is perpendicular to the processing surface.

2. The large relative aperture telecentric scanning field lens system according to claim 1, characterized in that: The negative lens is a plano-concave lens.

3. The large relative aperture telecentric scanning field lens system according to claim 1, characterized in that: The system operates in the wavelength range of 1.06~1.1 microns or 0.4~0.7 microns.

4. The large relative aperture telecentric scanning field lens system according to claim 1, characterized in that: The relative aperture F value is 2.6.

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