Light beam rounding device based on liquid crystal polarization grating group
By designing a beam rounder consisting of two sets of liquid crystal polarization gratings, the problem of complex beam shaping and difficulty in miniaturization in the existing technology is solved, and a simple, light and efficient beam rounding effect is achieved, which is suitable for compact optical systems.
Patent Information
- Application Number
- CN202422585134.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-25
- Publication Date
- 2025-09-05
- Estimated Expiration
- 2034-10-25
AI Technical Summary
Among existing laser diode beam shaping technologies, cylindrical mirror pairs and spatial filters are complex and difficult to miniaturize, while deformable prisms are bulky and complex to operate, making it difficult to achieve efficient rounding of the beam.
Two sets of oppositely arranged liquid crystal polarization gratings are used. The first polarization grating is perpendicular to the incident light, and the second polarization grating is set at an angle. By designing the grating period and angle relationship, the direction deflection of the light beam and the restoration of the polarization state are achieved, forming a thin and lightweight beam rounder.
It achieves a simple, thin and rounded effect on the light beam, is suitable for compact optical systems, can expand the beam in one dimension while keeping the other dimension unchanged, and can reversibly convert the spot shape.
Smart Images
Figure CN223308488U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a beam rounding technology, in particular to a beam rounder based on a liquid crystal polarization grating group. Background Art
[0002] In laser diode (LD) laser beam shaping technology, methods such as cylindrical mirror pairs, anamorphic prism pairs, and spatial filters are used to round the beam. Among them, both cylindrical mirror pairs and spatial filter shaping schemes require the incident laser to be aligned with the central optical axis of the system, which increases the complexity of the operation and is prone to introducing additional errors; Figure 1 As shown, two sets of deformable prisms use one-dimensional amplification to convert the elliptical beam of the laser diode into a nearly circular beam. Although this solution does not require laser center alignment, due to the design and material limitations of the deformable prism, it is usually thick and heavy, making it difficult to achieve miniaturization and integration. Utility Model Content
[0003] Purpose of the utility model: The purpose of the utility model is to provide a light beam rounder based on a liquid crystal polarization grating group with a simple structure and light volume to achieve light beam shaping.
[0004] Technical solution: To achieve the above-mentioned purpose, the utility model describes a beam rounder based on a liquid crystal polarization grating group, comprising two groups of oppositely arranged liquid crystal polarization gratings, wherein the first polarization grating is perpendicular to the incident light, and the second polarization grating is inclined relative to the first polarization grating, and the outgoing light after passing through the first polarization grating and the second polarization grating is emitted perpendicularly to the second polarization grating.
[0005] The relationship between the deflection angle θ of the incident light after passing through the first polarization grating and the period Λ1 of the first polarization grating satisfies: sinθ=λ / Λ1, where λ is the wavelength of the incident light beam.
[0006] Assume that the angle at which the second polarization grating is inclined relative to the first polarization grating is α, and the relationship between the angle α and the period Λ2 of the first and second polarization gratings satisfies: Λ2=λ / sin(α+θ).
[0007] The one-dimensional magnification of the beam rounder is: D2 / D1=cosθ / cos(θ+α), where D1 and D2 are the incident light diameter and the exit light diameter respectively.
[0008] The polarization grating includes a glass substrate, a light alignment layer film coated on one plane of the glass substrate, a liquid crystal polymer film coated on the light alignment layer film, and liquid crystal molecules on the liquid crystal polymer film are arranged to form a grating structure.
[0009] Wherein, the glass substrate is a transparent planar structure.
[0010] Wherein, the liquid crystal polymer films of the two groups of liquid crystal planar cylindrical mirrors are arranged face to face.
[0011] Beneficial effects: The utility model has the following advantages: 1. The beam rounder can expand the laser diode elliptical spot in one dimension in the short axis direction through directional deflection, while the other dimension remains unchanged, thereby achieving a rounding effect of the spot. When used in reverse, it has the function of converting a circular spot into an elliptical spot; 2. The beam rounder has a simple structure and a light and thin volume, which is conducive to integration into a compact optical system. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 Schematic diagram of the rounding of elliptical laser by deformable prism;
[0013] Figure 2 Schematic diagram of light beam deflection by liquid crystal polarization grating;
[0014] Figure 3 Schematic diagram of the beam rounder structure. DETAILED DESCRIPTION
[0015] The technical solution of the present utility model is described in detail below with reference to the embodiments and drawings.
[0016] like Figures 2-3 As shown, the beam rounder of the present invention realizes the shaping of the laser through a set of polarization grating pairs. The polarization grating is usually composed of liquid crystal molecules with different orientations arranged periodically, which can affect the phase and polarization state of the incident light, thereby having circular polarization selectivity. The left-handed and right-handed incident light will be deflected to different directions by the polarization grating, and its deflection angle is determined by the period of the polarization grating.
[0017] The beam rounder's specific structure is as follows: a first polarization grating is positioned perpendicular to the incident light, with a period of Λ1 (the period determines the deflection angle of the light beam passing through it). A second polarization grating is positioned at an angle α relative to the first, with a period of Λ2. The beam rounder adjusts the diameter of the beam's entrance plane based on the change in spot diameter on the cross section caused by the beam deflection caused by the polarization grating. The second polarization grating corrects the direction of the outgoing light while restoring the polarization state of the incident light. The outgoing light is parallel to the incident light, with only a certain lateral offset.
[0018] The laser is deflected by an angle of θ after passing through the first polarization grating, sinθ=λ / Λ1, where λ is the wavelength of the incident light beam. The incident light after passing through the first polarization grating is equivalent to being obliquely incident on the second polarization grating, and the angle of oblique incidence is θ+α. In order to restore the direction of the outgoing light, the period of the second polarization grating is:
[0019] Λ2=λ / sin(α+θ).
[0020] A beam rounder can be understood as a beam expander in the one-dimensional direction parallel to the paper, while maintaining the original beam diameter in the direction perpendicular to the paper. And because the grating has one-dimensional periodicity, it has the same function regardless of the aperture. α and θ together determine the one-dimensional magnification of the beam rounder. For an incident beam with a diameter of D1, the design formula for α is:
[0021] D2 / D1=cosθ / cos(θ+α)
[0022] Among them, D1 and D2 are the incident light diameter (the diameter in the direction that needs to be expanded) and the output light diameter respectively. If α is 0, there is no amplification effect on the light beam.
[0023] When the above-mentioned beam rounder is used to shape the elliptical incident light beam, the short axis of the elliptical incident light beam is deflected after passing through the first polarization grating, and the beam diameter in the short axis direction is projected onto the inclined grating. The diameter becomes larger on the inclined surface, thereby expanding the beam, while the diameter in the long axis direction remains unchanged.
[0024] The polarization grating structure of the present invention is composed of: glass substrate + light-oriented film + liquid crystal polymer film. By changing the arrangement of liquid crystal molecules, a grating with specific optical properties can be formed, thereby introducing a tilt phase and changing the emission direction of the light beam. In order to avoid the influence of the intermediate redundant medium on the light beam, when two sets of polarization gratings form a light beam rounder, the film surfaces are opposite and the glass surface faces outward.
Claims
1. A beam rounder based on a liquid crystal polarization grating group, characterized in that: It includes two sets of liquid crystal polarization gratings arranged opposite to each other. The first polarization grating is perpendicular to the incident light, and the second polarization grating is inclined relative to the first polarization grating. The outgoing light after passing through the first polarization grating and the second polarization grating is emitted perpendicularly to the second polarization grating.
2. The beam rounder based on the liquid crystal polarization grating group according to claim 1, characterized in that: The relationship between the deflection angle θ of the incident light after passing through the first polarization grating and the period Λ1 of the first polarization grating satisfies: , λ is the wavelength of the incident light beam.
3. The beam rounder based on the liquid crystal polarization grating group according to claim 2, characterized in that: Assume that the angle at which the second polarization grating is tilted relative to the first polarization grating is α, and the relationship between the angle α and the period Λ2 of the first and second polarization gratings satisfies: .
4. The beam rounder based on the liquid crystal polarization grating group according to claim 3, characterized in that: The one-dimensional magnification of the beam rounder is: , D1 and D2 are the incident light diameter and the exit light diameter respectively.
5. The beam rounder based on a liquid crystal polarization grating group according to claim 1, characterized in that: The polarization grating includes a glass substrate, a light alignment layer film coated on one plane of the glass substrate, and a liquid crystal polymer film coated on the light alignment layer film. Liquid crystal molecules on the liquid crystal polymer film are arranged to form a grating structure.
6. The beam rounder based on the liquid crystal polarization grating group according to claim 5, characterized in that: The glass substrate is a transparent planar structure.
7. The beam rounder based on a liquid crystal polarization grating assembly according to claim 5, characterized in that: The liquid crystal polymer films of the first polarization grating and the second polarization grating are arranged face to face.