Aspheric lens based on double-twisted liquid crystal microstructure

Abstract

The utility model discloses an aspherical lens based on a double-twisted liquid crystal microstructure, which comprises a glass substrate, an orientation layer coated on one plane of the glass substrate, and a liquid crystal polymer layer coated on the orientation layer, wherein the liquid crystal polymer layer comprises two liquid crystal polymer film sub-layers which are equal in thickness, consistent in liquid crystal molecule distortion angle size and opposite in direction, and a phase structure of the aspherical lens is written in the orientation layer. According to the aspheric lens based on the double-twisted liquid crystal microstructure, light of different wavelengths can be focused at the same position when passing through the lens, so that achromatic and spherical aberration effects are achieved, meanwhile, the aspheric lens is simple in structure, light and thin in size, beneficial to being integrated into a compact optical system for use, and low in machining cost and difficulty.

Description

Technical Field

[0001] This utility model relates to the field of aspherical lens technology, and in particular to an aspherical lens based on a double-twisted liquid crystal microstructure. Background Technology

[0002] For camera lenses using spherical glass, the surfaces near the glass edges always refract light at a steeper angle. This causes some incident light (mainly light near the curved edges) to focus before the focal plane, resulting in spherical aberration. Methods to correct spherical aberration typically include using a combination of positive and negative lenses or aspherical lenses. Compared to correcting spherical aberration by increasing the number of lenses, aspherical lenses can achieve better aberration correction with fewer lenses. For example, a zoom lens that typically uses ten or more lenses can use one or two aspherical lenses to replace five or six spherical lenses, achieving the same or better optical performance, thus reducing the length and complexity of the system.

[0003] However, aspherical lenses made from optical glass are mostly large in size and mass, which is not conducive to integration in small spaces. Furthermore, aspherical lenses usually require precision glass molding and precision polishing, which are costly and difficult to process. At the same time, most aspherical lenses cannot achieve chromatic aberration reduction. Utility Model Content

[0004] Purpose of the utility model: The purpose of this utility model is to provide an aspherical lens based on a double-twisted liquid crystal microstructure that is lightweight and thin, and achieves achromatic and spherical aberration elimination.

[0005] Technical solution: To achieve the above objectives, the present invention provides an aspherical lens based on a double-twisted liquid crystal microstructure, comprising a glass substrate, an alignment layer coated on one plane of the glass substrate, and a liquid crystal polymer layer coated on the alignment layer, wherein the liquid crystal polymer layer comprises two liquid crystal polymer thin film sublayers of equal thickness, with liquid crystal molecules twisted at the same angle and in opposite directions.

[0006] The two liquid crystal polymer film sublayers are doped with chiral agents of different chirality.

[0007] The glass substrate is a transparent planar structure.

[0008] The orientation layer contains the phase structure of an aspherical lens.

[0009] In this context, each phase in the alignment layer corresponds to the pointing direction of the liquid crystal molecules.

[0010] The phase structure is expressed as follows:

[0011]

[0012] In the formula, r is the radial distance from the central axis of the aspherical lens, z is the perpendicular distance of the phase function at r, c = 1 / R is the curvature of the vertex of the aspherical lens, R is the radius of curvature at the vertex, k represents the conic coefficient, and a 2n is the nth aspherical coefficient.

[0013] Beneficial effects: The present invention has the following advantages: 1. The aspherical lens based on the double-twisted liquid crystal microstructure described in the present invention enables light of different wavelengths to be focused at the same position when passing through the lens, thereby achieving the achromatic and spherical aberration effects; 2. It has a simple structure, is lightweight and thin, which is conducive to its integration into a compact optical system, and has low processing cost and difficulty. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the cross-sectional structure of an aspherical lens based on a double-twisted liquid crystal microstructure;

[0015] Figure 2 for Figure 1 Schematic diagram of liquid crystal molecule distribution in the liquid crystal polymer layer;

[0016] Figure 3 This is a schematic diagram of the phase structure of an aspherical lens. Detailed Implementation

[0017] The technical solution of this utility model will be described in detail below with reference to the embodiments and accompanying drawings.

[0018] Liquid crystal polymers are a special type of high molecular liquid crystal material. The liquid crystal molecules are arranged with a certain degree of order (one-dimensional or two-dimensional). The liquid crystal molecules can be oriented using an orientation agent, and ultraviolet light can be used to irradiate them to make the monomer molecules combine into a network, thus solidifying the orientation structure of the liquid crystal molecules.

[0019] As for the alignment layer where the alignment agent is located, the alignment layer is aligned by means of friction, light-controlled alignment, etc., so as to write microstructures at the micrometer or even submicrometer level. Then, the alignment agent is used to align the liquid crystal molecules to prepare liquid crystal microstructure elements with various optical properties.

[0020] The alignment agent is usually an azobenzene material, which is sensitive to ultraviolet polarized light. The long molecular chains are arranged perpendicular to the linear polarization direction, and the liquid crystal molecules can be arranged along the direction of the alignment agent through intermolecular forces.

[0021] like Figure 1 , 2As shown, based on the above principle, the aspherical lens based on the double-twisted liquid crystal microstructure of this utility model includes a glass substrate, an alignment layer coated on one plane of the glass substrate, and a liquid crystal polymer layer coated on the alignment layer. The liquid crystal polymer layer is divided into two sub-layers, which are two liquid crystal polymer films with equal thickness, consistent liquid crystal molecule twist angles, and opposite directions.

[0022] Before coating, the two sublayers are doped with chiral agents of different chirality, resulting in liquid crystal molecules with the same twist angle but opposite directions. Figure 2 The diagram shows the orientation reference of the sublayer. By adjusting the concentration of the chiral agent and the coating parameters, light of different wavelengths can be focused at the same position when passing through the lens, thus achieving achromatic and spherical aberration effects. Specifically, when light passes through the liquid crystal layer, different wavelengths of light (i.e., different colors of light) will be refracted to different degrees due to the orientation of the liquid crystal molecules. Since the two sublayers are twisted in opposite directions, their refraction effects can compensate for each other to a certain extent, allowing light of different wavelengths to have relatively close focal points after passing through the entire liquid crystal layer. By precisely controlling the concentration of the chiral agent and the coating parameters of the liquid crystal layer, the refractive index distribution of the liquid crystal layer can be adjusted, so that the paths of light of different wavelengths are precisely controlled when passing through the liquid crystal layer, ultimately focusing at the same position, achieving achromatic and spherical aberration effects.

[0023] Meanwhile, unlike liquid crystal polymer optical elements without chiral agents, the aspherical lens based on the double-twisted liquid crystal microstructure described in this invention is a wide-band device. It can simultaneously meet the half-wave condition within the hundreds of nanometers band by designing the twist angle, so as to achieve the highest utilization rate of the emitted light in this band.

[0024] The aforementioned orientation layer is inscribed with a phase structure relating to specific aspherical lens parameters using methods such as digitally controlled micromirror array (DMD) exposure systems and laser direct writing. Taking a conventional aspherical lens as an example, its expression is constructed by superimposing a series of high-order polynomials onto a conical surface as a reference plane, specifically:

[0025]

[0026] In the formula, r is the radial distance from the central axis of the aspherical lens, z is the perpendicular distance of the phase function at r, c = 1 / R is the curvature of the vertex of the aspherical lens, R is the radius of curvature at the vertex, k represents the conic coefficient, and a 2n is the nth aspherical coefficient.

[0027] The phase distribution plane diagram of the aspherical lens was plotted using MATLAB as follows: Figure 3As shown, the colors from black to white correspond to phases from 0 to π, with each phase corresponding to the direction of the liquid crystal molecule's orientation vector. The figure reveals that the aspherical mirror exhibits multiple periods of varying sizes from its center to its edge. The period size of the aspherical mirror differs from that of the spherical mirror; while the period of a typical spherical mirror gradually decreases from the center to the edge, the period of the aspherical mirror exhibits a distinct characteristic of varying speed.

[0028] This embodiment provides a process for fabricating the above-mentioned aspherical lens based on a double-twisted liquid crystal microstructure, including:

[0029] 1. Calculate the phase of different regions based on the aspherical lens formula to form a phase structure;

[0030] 2. Clean the glass substrate;

[0031] 3. Apply an alignment layer to the glass substrate;

[0032] 4. Write the phase structure into the alignment layer;

[0033] 5. Two sublayers are doped with chiral agents of different chirality on the left and right sides, and then coated sequentially on the orientation layer;

[0034] 6. Use ultraviolet light to cure the two sublayers.

Claims

1. A double-twist liquid crystal microstructure-based aspherical lens, characterized by, The application relates to a glass substrate, an orientation layer coated on one plane of the glass substrate, and a liquid crystal polymer layer coated on the orientation layer, wherein the liquid crystal polymer layer comprises two sublayers of liquid crystal polymer films with equal thickness, consistent twist angle and opposite direction of liquid crystal molecules.

2. The biaxial lens based on a double-twisted liquid crystal microstructure according to claim 1, wherein The glass substrate is a transparent plane structure.

3. The biaxial lens based on a double-twisted liquid crystal microstructure according to claim 1, wherein, The orientation layer is written with the phase structure of an aspheric lens.

4. The biaxial lens based on a double-twisted liquid crystal microstructure according to claim 3, wherein The phase of the orientation layer corresponds to the direction of the director of the liquid crystal molecules.

5. The biaxial lens based on a double-twisted liquid crystal microstructure according to claim 3, wherein The expression form of the phase structure is: ， where r is the radial distance from the center axis of the aspheric surface, z is the corresponding vertical distance of the phase function at r, c = 1 / R is the curvature of the vertex of the aspheric lens, R is the radius of the vertex curvature, k represents the conic coefficient, a 2n is the nth aspheric coefficient.

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