CN112578538A

CN112578538A - Telecentric F-Theta scanning lens for blue laser processing

Info

Publication number: CN112578538A
Application number: CN202011627630.3A
Authority: CN
Inventors: 朱国亮; 辜长明; 李圆; 张蒙蒙; 姜乃方
Original assignee: Qingdao Novelbeam Technology Co ltd
Current assignee: Qingdao Novelbeam Technology Co ltd
Priority date: 2020-12-30
Filing date: 2020-12-30
Publication date: 2021-03-30
Anticipated expiration: 2040-12-30
Also published as: CN112578538B

Abstract

The invention discloses a telecentric F-Theta scanning lens for blue laser processing. Starting from the laser incidence direction, the lens comprises a first lens L1 with a focal length f1, a second lens L2 with a focal length f2, a third lens L3 with a focal length f3, a fourth lens L4 with a focal length f4, a fifth lens L5 with a focal length f5 and a sixth lens L6 with a focal length f6, and the total focal length of the objective lens is f. The invention provides a blue laser, in particular to a 450nm laser processing telecentric scanning lens for the first time, which has the characteristics of short wave, short focus and large light-passing aperture, and the size of the light spot of the whole processing surface reaches the diffraction limit. The invention uses 6 lens structures, is easy to process under the condition of ensuring the performance and has reasonable cost. The F-Theta lens can be used for blue laser processing application, including but not limited to copper material precision welding, plastic welding, additive manufacturing and other processing applications, can obtain focusing light spots with high roundness and uniform size, and enables processing materials to form a welding pool which is uniformly heated under the guidance of fine laser scribing.

Description

Telecentric F-Theta scanning lens for blue laser processing

Technical Field

The invention relates to a laser processing scanning lens, in particular to a blue laser processing telecentric F-Theta scanning lens.

Background

The flat field scanning lens (F-Theta lens) images monochromatic light, and in laser scanning, negative distortion is utilized to change imaging, so that the scanning speed and the imaging speed are in a linear relation, an image surface is a plane, the image quality on the whole image surface is required to be consistent, and the diffraction limit is reached. The lens can be divided into a common F-Theta lens and a telecentric scanning lens, the telecentric scanning lens places the deflection position of an incident beam at the front focus of an object space, and the image space chief ray is parallel to the optical axis, so that the on-axis and off-axis image quality consistency can be realized to a great extent, the illumination uniformity is improved, and the telecentric scanning lens is widely applied to laser cutting, laser drilling and laser marking systems.

The covering wavelength of the traditional laser scanning lens comprises optical fiber lasers with 355nm,532nm,1064nm and the like or frequency doubling wavelength thereof, especially, 1064nm laser is largely applied to the processing fields of laser marking, laser cutting, laser welding and the like, along with the development of laser technology, the application of the optical fiber laser taking 1064nm as the central wavelength in the laser welding field makes great progress, including new energy automobile manufacturing, photovoltaic cell tab welding and the like. Even so, in the laser processing of gold, copper, aluminium and other non ferrous metals, the infrared laser wavelength is not the best working wavelength, because the copper is less than 10% of the basic material absorption at 1064nm, it is a high-reflection material, difficult to be used for laser processing, and low efficiency. Meanwhile, because the absorption efficiency of the material to 1064nm light is low, the welding application is accompanied by uneven heating effect, and the welding pool is easy to generate foaming, splashing, uneven fusion depth and other adverse factors, which is not beneficial to the terminal process application.

Therefore, the application of copper foil or copper material processing is still replaced by the traditional mechanical processing method in most cases, and the processing of the copper substrate becomes a blank area of laser processing. The root of solving the problem lies in starting from a light source, solving the problem of material absorption and applying laser processing to wider fields. According to the research table of materials, the absorption coefficient of non-ferrous metal materials such as gold and copper at 450nm is about 65%, and is more than 6 times of the absorption efficiency at 1064nm, so that the rapid development of blue lasers and laser elements with 450nm as the center is of great significance. In recent years, many laser light source manufacturers at home and abroad have developed and commercialized a 450nm blue light laser, the technology is mature day by day, the laser processing application taking the blue light laser as a light source in the future shows bright prospect, and the development of related optical components is also particularly critical.

Disclosure of Invention

The invention discloses a telecentric F-Theta scanning lens for blue laser processing, which has the advantages of being applied to blue laser wavelength for the first time, being adapted to an industrial-grade blue laser, having the characteristics of large light transmission aperture, short focus and telecentricity, achieving the diffraction limit of imaging and improving the processing precision.

This object is achieved by an F-Theta objective lens with the following features: the F-Theta objective lens comprises six independent lenses, namely a first lens L1 with a focal length F1, a second lens L2 with a focal length F2, a third lens L3 with a focal length F3, a fourth lens L4 with a focal length F4, a fifth lens L5 with a focal length F5 and a sixth lens L6 with a focal length F6, wherein the total focal length of the objective lens is F, the rear intercept of the objective lens is BFL, and the entrance pupil distance of the objective lens is EPD. The first lens is a negative lens, the second lens is a positive meniscus lens with the bending direction facing the entrance pupil of the lens, the third lens is a positive lens, the fourth lens is a negative meniscus lens with the bending surface facing the image plane, the fifth lens is a positive lens, and the sixth lens is a positive meniscus lens with the bending surface facing the image plane. The scanning lens is arranged into a power distribution of- + + -, the relative aperture F # is less than 3, the focal length F of the lens is less than 80, and the telecentric angle difference is less than 2.5 degrees. To achieve this object, it is required that the ratios among the focal lengths f1 to f6, BFL, EPD and the total focal length f satisfy the following conditions:

-1.2<f1/f<-0.7

+4.5<f2/f<+6.5

+1.5<f3/f<+3.5

-10.0<f4/f<-6.0

+1.5<f5/f<+3.5

+2.5<f6/f<+4.5

1.1＜BFL/f＜1.6

0.4＜EPD/f＜0.6。

preferably, f 1/f-0.9, f2/f +5.4, f3/f +2.6, f 4/f-8.3, f5/f +2.3, f6/f + 3.5; BFL/F is 1.3, EPD/F is more than 0.45 and less than 0.55, the scanning lens has larger relative aperture, the relative aperture F # is less than 3, the telecentricity is less than 2.5 degrees, and the scanning lens is suitable for blue laser processing application, in particular to 450nm laser application.

Drawings

FIG. 1: the geometric optical structure of the scanning lens of the present invention.

FIG. 2: examples field curvature diagrams.

FIG. 3: example F-Theta curve diagram.

FIG. 4: embodiments core optical systems image modulation transfer functions.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

The embodiment illustrates the technical scheme and the working principle of the invention by using a core optical system of an F-Theta blue light 450nm telecentric scanning lens with an angle of view of 11 degrees and an entrance pupil diameter of 30 mm. The embodiments have the same structure as the summary of the invention, and only the key data are listed to avoid duplication.

The schematic structural diagram of the optical system of the blue light 450nm telecentric F-Theta scanning lens is shown in FIG. 1, and in order to meet the design target requirement, 6 optical glass lenses are adopted, and the lenses adopt a power distribution of- + + - + ". Starting from the laser incidence direction, the lens comprises a first lens L1 with a focal length f1, a second lens L2 with a focal length f2, a third lens L3 with a focal length f3, a fourth lens L4 with a focal length f4, a fifth lens L5 with a focal length f5 and a sixth lens L6 with a focal length f6, and the total focal length of the objective lens is f. The first lens is a negative lens, the second lens is a positive meniscus lens with the bending direction facing the entrance pupil of the lens, the third lens is a positive lens, the fourth lens is a negative meniscus lens with the bending surface facing the image plane, the fifth lens is a positive lens, and the sixth lens is a positive meniscus lens with the bending surface facing the image plane. In a preferred embodiment, the focal length of each mirror and the focal length f of the scanning lens satisfy:

f1/f＝-0.9，f2/f＝+5.4，f3/f＝+2.6，f4/f＝-8.3，f5/f＝+2.3，f6/f＝+3.5，f＝60mm。

in light of the above requirements, there is further provided a design example, wherein the specific parameters refer to table 1:

the lenses and power numbers are numbered in sequence along the optical axis Z of the F-Theta scanning lens in the direction of beam penetration, and the curvature of field of the embodiment is shown in FIG. 2; example F-Theta curves are schematically shown in FIG. 3; the imaging modulation transfer function is shown in figure 4.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A laser processing telecentric F-Theta scanning lens is characterized by comprising a first lens L1 with a focal length F1, a second lens L2 with a focal length F2, a third lens L3 with a focal length F3, a fourth lens L4 with a focal length F4, a fifth lens L5 with a focal length F5 and a sixth lens L6 with a focal length F6 from the incident direction of laser, wherein the first lens is a negative lens, the second lens is a positive meniscus lens with the bending direction facing to the entrance pupil of the lens, the third lens is a positive lens, the fourth lens is a negative meniscus lens with the bending surface facing to the image plane, the fifth lens is a positive lens, the sixth lens is a positive meniscus lens with the bending surface facing to the image plane, the scanning lens integrally uses a "- +" optical power distribution, the distance from the center of the entrance pupil plane to the center of the first lens L1 is defined as the entrance distance EPD of the scanning lens, the distance from the last surface of the scanning lens (namely the right side surface of the sixth lens) to the image surface is a back focal length BFL; wherein the ratio between the focal lengths f 1-f 6 and the total focal length f satisfies the following condition:

-1.2<f1/f<-0.7

+4.5<f2/f<+6.5

+1.5<f3/f<+3.5

-10.0<f4/f<-6.0

+1.5<f5/f<+3.5

+2.5<f6/f<+4.5

1.1＜BFL/f＜1.6

0.4＜EPD/f＜0.6。

2. telecentric scan lens according to claim 1, preferably characterized in that,

f1/f＝-0.9，f2/f＝+5.4，f3/f＝+2.6，f4/f＝-8.3，f5/f＝+2.3，f6/f＝+3.5；BFL/f＝1.3，0.45＜EPD/f＜0.55。

3. the laser telecentric F-Theta scanning lens according to claim 2, characterized in that it has a relatively large aperture, the relative aperture F # < 3.

4. A laser telecentric F-Theta scanning lens according to claim 2, further characterized by being suitable for blue laser processing applications, in particular 450nm laser applications.

5. A laser telecentric F-Theta scan lens according to claim 2, wherein the telecentricity of the scan lens is < 2.5 °.