Large-aperture liquid crystal lens array based on layered combined electrodes

Abstract

The invention provides a large-aperture liquid crystal lens array based on layered combined electrodes, which structurally comprises an upper glass substrate, a first electrode, an upper orientation layer, a liquid crystal layer, a lower orientation layer, a second electrode, a dielectric layer, a third electrode and a lower glass substrate which are arranged in sequence. Central electrodes of the first electrode and the second electrode are grounded to serve as common electrodes, voltages are applied to the transparent strip-shaped electrodes at the two ends of the second electrode and the third electrode, the values of the voltages applied to the transparent strip-shaped electrodes (V1) at the two ends are different from the values of the voltages applied to the third electrode (V2), and V1 # immabs0 # V2 are used for forming a non-uniform gradient electric field. And the liquid crystal molecules are arranged parallel to the upper and lower substrates under the action of the upper and lower orientation layers. The invention has the advantages of simple structure, simple and convenient driving mode, low power consumption, large zoom range and the like, and can realize flexible switching of 2D / 3D display.

Description

Technical Field

[0001] The invention relates to the field of liquid crystal lenses, in particular to a large-aperture liquid crystal lens array based on layered combined electrodes. Background Art

[0002] In recent years, with the popularization and development of virtual reality technology and naked-eye 3D technology, free stereoscopic displays have made up for the defect of 2D displays that cannot provide depth information and truly reflect the information of the three-dimensional world. Free stereoscopic display technology has attracted widespread attention in academia and industry. Therefore, free stereoscopic displays are expected to play a leading role in the next generation of display technology.

[0003] The most commonly used methods in free-stereoscopic display technology are fixed parallax barrier method or microlens array method. However, these methods will reduce the quality of 2D images when the display shows 2D images. Therefore, in practical applications, it is very important to switch between 2D / 3D modes. The most direct way to achieve 2D / 3D switchable function is to use adaptive optical lenses. Among the many adaptive lenses, liquid crystal lenses have broad application prospects in 2D / 3D switchable display technology due to their advantages such as thin thickness, planarization and low driving voltage. Summary of the invention

[0004] In order to solve or alleviate the problems in the prior art and overcome the defects in the prior art, the present invention proposes a large-aperture liquid crystal lens array which is simple in structure, easy to manufacture, simple to drive and has a wide adjustable focal length range.

[0005] The present invention proposes a large-aperture liquid crystal lens array based on layered combination electrodes, comprising: upper glass substrate; A first electrode, disposed below the upper glass substrate, serving as a ground electrode; an upper alignment layer, disposed below the first electrode, for providing a consistent initialization state for liquid crystal molecules in the liquid crystal layer; a liquid crystal layer, disposed below the upper alignment layer; A lower alignment layer, disposed below the liquid crystal layer, for providing a consistent initialization state for liquid crystal molecules in the liquid crystal layer; A second electrode, disposed below the lower alignment layer, is composed of transparent strip electrodes at both ends and a central ground electrode, and is used to form a smooth and gradual gradient spatial distribution of the electric field between the first and second electrodes; a dielectric layer, disposed below the second electrode; A third electrode, disposed below the dielectric layer, for providing a voltage to a central area of ​​a single liquid crystal lens array; A lower glass substrate, disposed below the third electrode;

[0006] The ground electrode at the center of the first electrode and the second electrode serves as a common electrode. Voltage is applied to the transparent strip electrodes at both ends of the second electrode and the third electrode. However, the voltage values ​​applied to the transparent strip electrodes (V1) at both ends and the third electrode (V2) are different, and V1>V2.

[0007] The effective refractive index variation in the liquid crystal layer is expressed based on the refractive index ellipsoid equation: Where n o and n e are the refractive indices of ordinary light and extraordinary light in the liquid crystal layer, respectively.

[0008] The focal length of the lens is given by the Fresnel approximation: f=R 2 / 2dδn Where R is the radius of a single liquid crystal lens array, d is the thickness of the liquid crystal layer, and δn is the refractive index difference between the center and the boundary edge of a single liquid crystal lens array.

[0009] In order to obtain a shorter focal length and improve the focusing effect, a larger refractive index difference needs to be generated between the center and the edge of a single liquid crystal lens array.

[0010] The liquid crystal lens array generates a large refractive index difference from two aspects. On the one hand, transparent strip electrodes are arranged at both ends of the second electrode to increase the electric field strength in the edge area, thereby increasing the rotation angle of the edge liquid crystal molecules and reducing the edge refractive index. On the other hand, a voltage is applied to the third electrode to increase the electric field strength in the central area, increase the rotation angle of the liquid crystal molecules in the central area, and the top of the refractive index distribution curve is closer to the ideal state, solving the problem of unclear deflection of the central liquid crystal molecules when the aperture is enlarged.

[0011] The present invention provides a large-aperture single liquid crystal lens array based on a layered combination electrode, wherein the second electrode is composed of transparent strip electrodes at both ends and a central ground electrode. The third electrode is located at the center of the bottom to provide voltage to the central area of ​​the single liquid crystal lens array. The layered combination electrode composed of this structure is more likely to generate a gradient electric field. In the absence of applied voltage, the single liquid crystal lens array exhibits characteristics similar to those of flat glass. After applying voltage, the gradient electric field induces liquid crystal molecules to form a gradient refractive index profile, and the gradient refractive index causes a focusing effect. Therefore, the non-focusing mode and the focusing mode can be switched by a voltage-off state and a voltage-on state.

[0012] A central grounding electrode is placed at the center of the second electrode of the single liquid crystal lens array. This design makes the arrangement of the central liquid crystal molecules closer to the ideal state; at the same time, a transparent plane auxiliary electrode is set at the third electrode below it to increase the voltage in the central area, thereby achieving the ideal arrangement of the liquid crystal molecules. This structural design not only solves the problem that the central liquid crystal molecules are difficult to deflect when the caliber becomes larger, but also simplifies the drive of the liquid crystal lens array, greatly reduces energy consumption, and has a significant energy-saving effect. Compared with the traditional liquid crystal lens array, the present invention designs the electrode structure and optimizes the arrangement of liquid crystal molecules, so that the lens can achieve a wide range of ideal focusing effects at a lower voltage, further improving the performance and application potential of the liquid crystal lens array. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to provide a further understanding of the technical solution of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the technical solution of the present disclosure and do not constitute a limitation on the technical solution of the present disclosure. The shapes and sizes of the components in the accompanying drawings do not reflect the actual proportions and are only intended to illustrate the contents of the present disclosure. Attached Figure 1 (a) and (b) are schematic diagrams of the large-aperture liquid crystal lens array structure based on the combined electrode of the present invention before and after power is applied. Attached Figure 2 This is the potential distribution diagram of a single liquid crystal lens array under a certain voltage applied in the present invention. Attached Figure 3 This is the electric field distribution diagram of a single liquid crystal lens array under a certain voltage applied to the present invention. Attached Figure 4 This is a schematic diagram of the distribution of liquid crystal molecules under a certain voltage applied in the present invention. Attached Figure 5 It is a fitting diagram of the actual refractive index curve of the present invention when voltage is applied and the ideal nonlinear curve. Attached Figure 6 It is a phase distribution of incident linear polarized light and an ideal nonlinear curve fitting diagram when voltage is applied in the present invention. Attached Figure 7 It is the refractive index curve of the present invention when different voltages are applied. Attached Figure 8 It is the focal length variation curve of the present invention when different voltages are applied. The diagram numbers in the above drawings are: 1 upper glass substrate; 2 first electrode; 3 upper orientation layer; 4 liquid crystal layer; 5 lower orientation layer, 6 transparent strip electrodes at both ends; 7 center ground electrode; 8 dielectric layer; 9 third electrode; 10 lower glass substrate. DETAILED DESCRIPTION

[0014] In order to enable those skilled in the art to further understand the present invention, the specific implementation of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the accompanying drawings are for illustration purposes only and are not drawn according to the original size.

[0015] The incident light wavelength λ used in this example is 550nm, the liquid crystal layer thickness h is 200μm, and in a single liquid crystal lens array, the width of the first electrode is w1=800μm; the width of the transparent strip electrodes at both ends is w2=w3=30μm; the width of the center ground electrode is w4=20μm; the width of the third electrode is w5=330μm; and the lens aperture is 800μm.

[0016] The electrodes are all made of indium tin oxide (ITO) transparent conductive material; the electrodes have the same thickness; the first electrode and the second electrode center ground electrode serve as a common electrode, and voltage is applied to the transparent strip electrodes at both ends of the second electrode and the third electrode.

[0017] The rubbing directions of the upper and lower alignment layers are both perpendicular to the long side directions of the transparent strip electrodes.

[0018] The liquid crystal layer uses E7 liquid crystal as a material, the initial arrangement of the liquid crystal molecules is perpendicular to the long side direction of the transparent strip electrodes, and the thickness of the liquid crystal layer is uniform.

[0019] In this example, V1 = 4.8V, V2 = 1.7V.

[0020] Attached Figure 1 The schematic diagram of the structure of a large-caliber liquid crystal lens array based on a layered combination electrode provided by an embodiment of the present invention is shown. The structure includes an upper glass substrate, a first electrode, an upper orientation layer, a liquid crystal layer, a lower orientation layer, a second electrode, a dielectric layer, a third electrode and a lower glass substrate. The above electrodes are all made of ITO transparent conductive material with a thickness of 0.04μm, wherein the center ground electrode of the first electrode and the second electrode is used as a common electrode. The liquid crystal layer has a uniform thickness and uses E7 liquid crystal material with a thickness of 200μm. The rubbing direction of the upper and lower orientation layers is perpendicular to the long side direction of the transparent strip electrode. When there is no external electric field, the liquid crystal molecules are arranged parallel to the upper and lower substrates under the action of the upper and lower orientation layers, and there is no difference in the refraction effect of light on each part of the liquid crystal layer. The refractive index of the liquid crystal layer is uniformly distributed, and there is no focusing effect on the light. When a voltage is applied to the transparent strip electrodes at both ends and the third electrode, a non-uniform electric field will be generated in the liquid crystal layer. For a single liquid crystal lens array area, the electric field in the liquid crystal layer gradually decreases from the edge of the liquid crystal lens array to the center of the liquid crystal lens array, and the liquid crystal molecules are arranged parallel to the direction of the electric field to form a centrally symmetrical gradient distribution. Therefore, different parts of the liquid crystal layer will produce different refraction effects on the incident light, resulting in a focusing effect.

[0021] Attached Figure 2The potential distribution diagram of a single liquid crystal lens array under applied voltage in an embodiment of the present invention is shown. It can be seen that the distribution of the potential becomes more and more dense from the center to the edge, indicating that the electric field strength gradually increases. The gradually increasing electric field strength can effectively increase the rotation angle of the liquid crystal molecules from the center to the edge, thereby forming an ideal refractive index distribution.

[0022] Attached Figure 3 The electric field distribution diagram of a single liquid crystal lens array under the voltage of V1 = 4.8V and V2 = 1.7V in the embodiment of the present invention is shown. It can be clearly seen that the electric field intensity gradually increases from the center to the edge. This distribution is consistent with the attached Figure 2 The potential distribution in the liquid crystal lens array is completely consistent, so a single liquid crystal lens array under this operating voltage can achieve the best focusing effect.

[0023] Attached Figure 4 The schematic diagram of the distribution of liquid crystal molecules under a certain voltage in an embodiment of the present invention is shown. The figure clearly shows that when different voltages are applied to the transparent strip electrodes at both ends of the second electrode and the third electrode, the liquid crystal molecules begin to deflect under the action of the electric field. This deflection phenomenon originates from the electro-optical properties of the liquid crystal material, that is, under the influence of the electric field, the orientation of the liquid crystal molecules will change, thereby causing a change in the refractive index. As the voltage gradually increases, the liquid crystal molecules are gradually arranged into an ideal gradient refractive index distribution. At the same time, since a central grounding electrode is placed in the center of the second electrode, it is used to accurately control the central electric field part while facilitating the deflection of the central liquid crystal molecules, reducing the required voltage and achieving an energy-saving effect.

[0024] Attached Figure 5 The fitting results of the actual refractive index curve and the ideal nonlinear curve under applied voltage are shown. It can be clearly observed from the figure that the spatial distribution of the refractive index is symmetrical around the center line of the lens. The fitting results show that the maximum effective refractive index is 1.723 and the minimum effective refractive index is 1.547, which means that the effective refractive index difference between the edge and the center of a single liquid crystal lens array reaches 0.176, reflecting a large refractive index difference, indicating that the structure can achieve the best focusing effect when a certain voltage is applied.

[0025] Attached Figure 6 The fitting results of the phase distribution of the incident linear polarized light under applied voltage and the ideal nonlinear curve are shown. It can be seen that the phase distribution of the incident linear polarized light matches the ideal parabola very well, indicating that the proposed liquid crystal lens array can achieve a good focusing effect.

[0026] Attached Figure 7 The change of the refractive index of a single liquid crystal lens array under different voltages is demonstrated, which shows that the present invention can achieve an ideal state at a relatively low voltage.

[0027] Attached Figure 8 The relationship between the focal length and voltage is shown, where the horizontal axis is the voltage V1 applied to the transparent strip electrodes at both ends. When no voltage is applied, the focal length tends to infinity, so that the liquid crystal lens array has no light focusing effect. As the applied voltage increases, the focal length decreases sharply due to the inverse relationship between the focal length and the equivalent refractive index difference. When the applied voltage reaches V1=3V, the focal length is 15mm. However, when this voltage is exceeded, the interaction between the anchoring energy and the electric potential energy gradually reaches saturation, and the liquid crystal molecules are difficult to rotate as the voltage increases, and the degree of focal length reduction decreases. When V1=4.8V, the focal length of a single liquid crystal lens array reaches the shortest (2.2mm). This result verifies the rationality of the design and shows that by precisely controlling the voltage, the arrangement of liquid crystal molecules can be optimized, thereby improving the focusing ability of the lens.

[0028] The above is only a preferred embodiment of the present invention, but the present invention is not limited to this embodiment. It should be understood by those skilled in the art that various changes made to its form and details without departing from the spirit and scope of the present invention defined by the claims should all be within the scope of the present invention.

Claims

1. A large-aperture liquid crystal lens array based on layered combination electrodes, comprising: upper glass substrate; A first electrode, disposed below the upper glass substrate, serving as a ground electrode; an upper alignment layer, disposed below the first electrode, for providing a consistent initialization state for liquid crystal molecules in the liquid crystal layer; A liquid crystal layer, disposed below the upper alignment layer, for providing a consistent initialization state for liquid crystal molecules in the liquid crystal layer; A lower alignment layer, disposed below the liquid crystal layer, for providing a consistent initialization state for liquid crystal molecules in the liquid crystal layer; A second electrode, disposed below the lower alignment layer, is composed of transparent strip electrodes at both ends and a central ground electrode, and is used to form a smooth and gradual gradient spatial distribution of the electric field between the first and second electrodes; a dielectric layer, disposed below the second electrode; A third electrode, disposed below the dielectric layer, for providing a voltage to the center of the liquid crystal lens; A lower glass substrate, disposed below the third electrode; It is characterized by further comprising: The rubbing directions of the upper and lower alignment layers are perpendicular to the long side direction of the transparent strip electrodes. The initial arrangement of the liquid crystal molecules is perpendicular to the long side direction of the transparent strip electrodes, and the thickness of the liquid crystal layer is uniform; The electrodes are all made of indium tin oxide (ITO) transparent conductive material; the thickness of the electrodes is the same.

2. A large-aperture liquid crystal lens array based on layered combination electrodes as claimed in claim 1, characterized in that: The ground electrode at the center of the first electrode and the second electrode serves as a common electrode, and voltage is applied to the transparent strip electrodes at both ends of the second electrode and the third electrode.

3. A large-aperture liquid crystal lens array based on layered combination electrodes as claimed in claim 2, characterized in that: The voltage values ​​applied to the transparent strip electrodes (V1) at both ends and the third electrode (V2) are different, and V1 V2.

4. A large-aperture liquid crystal lens array based on layered combination electrodes as claimed in claim 1, characterized in that: The refractive index of the liquid crystal molecules is ； in n o and n e are the refractive indices of ordinary light and extraordinary light in the liquid crystal layer, respectively.

5. The large-aperture liquid crystal lens array based on layered combination electrodes as claimed in claim 1, wherein the focal length of the lens is given by Fresnel approximation: ； in R is the radius of a single liquid crystal lens array, d is the thickness of the liquid crystal layer, δ n is the refractive index difference between the center and edge of a single liquid crystal lens array.

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