CN217902183U

CN217902183U - Collimating flat-top Gaussian beam converter

Info

Publication number: CN217902183U
Application number: CN202222091229.3U
Authority: CN
Inventors: 邹快盛; 吴青晴
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2022-08-09
Filing date: 2022-08-09
Publication date: 2022-11-25
Anticipated expiration: 2032-08-09

Abstract

The application belongs to the optical device field, provides a collimation flat-top Gaussian beam converter, includes: the system comprises a beam expanding lens group, a polygonal gradient refractive index lens array, an aspheric focusing lens, a polygonal gradient refractive index optical fiber image transmission beam and a collimating element; the beam expanding lens group is used for expanding and collimating incident light, the expanded and collimated light is incident to the polygonal gradient index lens array, and the light output from the polygonal gradient index lens array is focused to an image focal plane of the aspheric focusing lens after passing through the aspheric focusing lens; one end face of the polygonal gradient refractive index optical fiber image transmission beam is placed at an image space focal plane of the aspheric focusing lens, and the other end face of the polygonal gradient refractive index optical fiber image transmission beam is placed at an object space focal plane of the collimating lens. The collimation flat-top beam converter can convert non-uniform Gaussian beams emitted by a light source into flat-top beams, improves the distribution uniformity of light energy in an exposure area, and overcomes the defect that the center bright edge of a working light spot of the traditional Gaussian beam is dark.

Description

Collimating flat-top Gaussian beam converter

Technical Field

The application belongs to the field of optical devices, and particularly relates to a Gaussian beam converter.

Background

With the popularization of laser application, the shaping and homogenization of light beams are required in the fields of laser display and illumination, laser medical treatment, laser cleaning, laser cutting, welding, scientific research and the like, namely, the conventional laser Gaussian beam with high middle energy and low surrounding energy is converted into a flat-topped beam with uniformly distributed light intensity. The former common modes for converting Gaussian beams into flat-topped beams include beam expanding and diaphragm adding, aspheric lens group, fly-eye micro lens array, liquid crystal spatial light modulator, diffractive optical element, polygonal homogenizing rod and the like.

First, a relatively uniform flat-top beam can be obtained by taking a part of a relatively uniform light beam in the central area of a gaussian beam through a beam expanding and diaphragm adding method, but the use of a diaphragm causes high energy loss, and is not a good solution.

Secondly, an aspheric lens group shaping method is based on the geometrical optics principle, adopts a Keplerian telescope structure form consisting of two aspheric lenses, can collimate flat-top beams through phase regulation, and can realize any wavefront transformation theoretically, but the system needs to adopt a complex aspheric structure, has high requirements on processing and detecting equipment, and has large processing difficulty; the method only has good effect on single-mode laser beams, but actually, light beams emitted by a plurality of laser systems are complex multi-mode laser beams, and the variation of the light field intensity distribution along with time has uncertainty, so that the method has great application limitation.

And thirdly, a fly-eye micro-lens array shaping method, which is characterized in that a light source is collimated by using an aspheric collimating lens, then the light source is input into a micro-lens array to segment the wave surface of an input light spot, and the segmented light spots are gathered and superposed through a subsequent focusing lens, so that homogenized light field distribution is obtained, and the shape of the light spot is related to the shape of the micro-lens. The more the number of the sub-mirrors of the fly-eye micro-lens array is, the better the homogenization effect of the light beam is. The method enables the plurality of divided sub-beams to be gathered on a specific plane, and the Gaussian beam is homogenized into a flat top, but the flat top beam cannot keep long-distance propagation of the original surface.

And fourthly, a liquid crystal spatial light modulator shaping method, which utilizes computer programming to control the light intensity distribution of each pixel point of the output surface to realize adjustable light beam spatial shaping, but the shaping effect is influenced by the limited pixel size of liquid crystal and the gaps among the pixels, so that the application scene is limited.

The existing flat-top Gaussian beam converter is difficult to realize better flat-top conversion effect and collimation characteristic for the beams with complex light field distribution.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problems pointed out in the background technology, the following technical scheme is adopted:

a collimation flat-top Gaussian beam converter is sequentially arranged along the positive direction of an optical axis as follows: the system comprises a beam expanding lens group, a polygonal gradient refractive index lens array, an aspheric focusing lens, a polygonal gradient refractive index optical fiber image transmission beam and a collimating element; the beam expanding lens group is used for expanding and collimating incident light, the expanded and collimated light is incident to the polygonal gradient index lens array, and the light output from the polygonal gradient index lens array is focused to an image focal plane of the aspheric focusing lens after passing through the aspheric focusing lens; one end face of the polygonal gradient refractive index optical fiber image transmission beam is placed at an image space focal plane of the aspheric surface focusing lens, and the other end face of the polygonal gradient refractive index optical fiber image transmission beam is placed at an object space focal plane of the collimating lens.

The working principle of the device is as follows: the light beam is expanded and collimated by a beam expanding lens group; the method comprises the steps of adopting a tightly arranged polygonal gradient refractive index lens array to segment wave surfaces of light beams with complex light field distribution, tightly arranging seamless gradient refractive index lenses in the polygonal gradient refractive index lens array, avoiding energy loss caused by Fresnel diffraction, collecting the segmented wave surfaces through an aspheric focusing lens, inputting the emergent wave surfaces of the gradient refractive index lenses into polygonal gradient refractive index optical fiber image transmission beams through the aspheric focusing lens, uniformly distributing flat-top light beams collected by the aspheric focusing lens into sub-optical fibers for transmission, and collimating and combining the flat-top light beams into the flat-top light beams through a collimating lens after being output from the sub-optical fibers, thereby realizing long-distance collimating transmission.

Furthermore, the polygonal gradient index lens array is an array structure with a polygonal cross section formed by arranging a plurality of polygonal gradient index lenses.

Furthermore, the image transmission bundle of the polygonal gradient refractive index optical fiber is an array structure with polygonal cross sections formed by gapless close packing and arrangement of a plurality of polygonal gradient refractive index optical fibers with the cross section side length of 1-5 micrometers. The polygonal gradient refractive index optical fiber is used as a sub-optical fiber and is arranged in an array to form the polygonal gradient refractive index optical fiber image transmission bundle with the light transmission function.

Preferably, the beam expanding lens group is composed of a first converging lens and a second converging lens, and an image space focal point of the first converging lens coincides with an object space focal point of the second converging lens. The first converging lens focuses the incident laser beam into spherical waves, and the spherical waves are adjusted into plane waves through the second converging lens arranged in a confocal mode, so that beam expansion and collimation of the incident laser beam are achieved.

Furthermore, an aperture filter is arranged at the image space focus of the first converging lens. The aperture filter is used for filtering stray light.

Further, the number of sides of the polygon is: 2 (n + 1) pieces, wherein n is a natural number. For example, when the refractive index of the polygonal gradient index lens array is four, six or octagonal, the refractive index of each polygonal gradient index lens in the polygonal gradient index lens array is distributed symmetrically with respect to the center.

The collimation flat-top light beam converter can convert the non-uniform complex light field light beam emitted by the light source into the flat-top light beam, so that the light energy distribution uniformity in the exposure area is improved, and the defect that the bright edge at the center of the working light spot of the traditional Gaussian beam is dark is overcome.

Drawings

FIG. 1: a schematic diagram of a collimated flat-topped Gaussian beam converter;

FIG. 2 is a schematic diagram: the schematic diagram of the light ray transmission track and the cross-section refractive index distribution of the polygonal gradient refractive index lens axis;

FIG. 3: a schematic diagram of refractive index distribution of a quadrilateral gradient refractive index fiber lens array structure and a cross section;

wherein: 1. a beam expanding lens group; 2. a polygonal gradient index lens array; 3. an aspherical focusing lens; 4. polygonal gradient refractive index optical fiber image transmission bundle; 5. a collimating lens.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings. Hereinafter, the terms "first" and "second" in the present application are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The "plurality" described herein is not particularly limited to specific ones, but should be understood as a preset number selected according to a set target.

Example one

The collimated flat-top gaussian beam converter shown in fig. 1 is sequentially arranged along the positive direction of the optical axis as follows: the device comprises a beam expanding lens group 1, a polygonal gradient refractive index lens array 2, an aspheric focusing lens 3, a polygonal gradient refractive index optical fiber image transmission beam 4 and a collimating element 5; the beam expanding lens group is used for expanding and collimating incident light, the expanded and collimated light is incident to the polygonal gradient index lens array, and the light output from the polygonal gradient index lens array is focused to an image focal plane of the aspheric focusing lens after passing through the aspheric focusing lens; the light input end surface of the polygonal gradient refractive index optical fiber image transmission beam is arranged at the image space focal plane of the aspheric focusing lens, and the light output end surface is arranged at the object space focal plane of the collimating lens.

When the light which is subjected to beam expanding and collimating enters the polygonal gradient refractive index lens array, each gradient refractive index lens in the polygonal gradient refractive index lens array divides the light which is subjected to beam expanding and collimating into wavelet surfaces corresponding to the gradient refractive index lens, and each wavelet surface is focused to a focal plane of the aspheric surface focusing lens after passing through the aspheric surface focusing lens.

After the light which is expanded and collimated passes through the polygonal gradient refractive index lens array, each wavelet surface is focused on an image focal plane through the convergence action of an aspheric focusing lens, and homogenized light beams are obtained at the image focal plane; the homogenized light beams are uniformly distributed and input into the polygonal gradient refractive index optical fiber image transmission bundle, and the light beams are output from each sub-optical fiber in the polygonal gradient refractive index optical fiber image transmission bundle, then pass through the collimating element and are collimated and combined into flat-top light beams.

As shown in fig. 2, incident light rays with different incident angles are transmitted forwards in the polygonal gradient refractive index lens according to a sine rule, the light ray transmission process is repeated according to a fixed period rule, if the period is denoted as P, when the length L of the polygonal gradient refractive index lens array is 0.25P, collimated light is incident from one end, and the light rays are automatically focused on the other end face; if the length of the polygonal gradient index lens is selected to be integral multiples of a half period, such as 0.5P, 1P, 1.5P, 2P, the light rays exit as parallel light. The polygon gradient index lens array can be used, the length of the polygon gradient index lens array is set to be n x 0.5P, and functions of light collimation or image transmission and the like are achieved, wherein n is a natural number.

As shown in fig. 3, which is a schematic diagram of a refractive index distribution of a quadrilateral gradient index lens array and a cross section thereof, it can be seen that the array is formed by arranging 10 × 10 quadrilateral gradient index lenses in a quadrilateral way in which the cross section is a quadrilateral, wherein the refractive index of each quadrilateral gradient index lens shows a gradient distribution in which the refractive index gradually decreases from the center to the edge.

The cross section of the polygonal gradient refractive index lens array is polygonal, so that gaps between the side walls can be effectively reduced, and the filling rate is improved.

Claims

1. The utility model provides a collimation flat-top gaussian beam converter which characterized in that sets gradually along the positive direction of optical axis: the system comprises a beam expanding lens group, a polygonal gradient refractive index lens array, an aspheric focusing lens, a polygonal gradient refractive index optical fiber image transmission beam and a collimating element; the beam expanding lens group is used for expanding and collimating incident light, the expanded and collimated light is incident to the polygonal gradient index lens array, and the light output from the polygonal gradient index lens array is focused to an image focal plane of the aspheric focusing lens after passing through the aspheric focusing lens; one end face of the polygonal gradient refractive index optical fiber image transmission beam is placed at an image space focal plane of the aspheric focusing lens, and the other end face of the polygonal gradient refractive index optical fiber image transmission beam is placed at an object space focal plane of the collimating lens.

2. The collimated flat-topped gaussian beam transformer of claim 1, wherein: the polygonal gradient refractive index lens array is an array structure with a polygonal cross section formed by arranging a plurality of polygonal gradient refractive index lenses.

3. The collimated flattop gaussian beam transformer of claim 1, wherein: the polygonal gradient refractive index optical fiber image transmission beam is of an array structure with a polygonal cross section formed by tightly stacking and arranging a plurality of polygonal gradient refractive index optical fibers with the side length of the cross section of 1-5 micrometers in a gapless manner.

4. The collimated flat-topped gaussian beam transformer of claim 1, wherein: the beam expanding lens group consists of a first converging lens and a second converging lens, the image space focus of the first converging lens is superposed with the object space focus of the second converging lens, the first converging lens focuses the incident laser beam into spherical waves, and the spherical waves are adjusted into plane waves through the second converging lens which is arranged in a confocal mode.

5. The collimated flattop gaussian beam transformer of claim 4, wherein: an aperture filter is arranged at the image space focus of the first convergent lens.

6. The collimated flat-topped gaussian beam transformer of claim 1, wherein: the number of the polygon sides is: 2 (n + 1) pieces, wherein n is a natural number.

7. The collimated flattop gaussian beam transformer of claim 1, wherein: the length of the polygonal gradient index lens array is n x 0.5P, wherein n is a natural number, and P is a transmission period of light rays in the polygonal gradient index lens array.