A position-modulated liquid crystal lens based on the principle of electric field superposition
By employing multiple electrodes of identical shape and the principle of electric field superposition in the liquid crystal lens, precise adjustment of the lens position is achieved, solving the problems of insufficient positional accuracy and difficulty in electrode etching, thereby improving imaging quality and the performance of the adaptive optics system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CIVIL AVIATION FLIGHT UNIV OF CHINA
- Filing Date
- 2023-12-19
- Publication Date
- 2026-05-26
Smart Images
Figure CN117555184B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of liquid crystal lenses, specifically to a liquid crystal lens with laterally controllable lens position. Background Technology
[0002] A liquid crystal lens is a device that uses the optical properties of liquid crystal materials to adjust the refraction of light. It has advantages such as high integration, tunability, and low power consumption. Currently, it has wide applications in optical equipment, laser science and engineering, adaptive optics systems, and optical communications.
[0003] In liquid crystal lenses, the lens position has a significant impact on imaging performance. Taking the lens center position as an example, in optical devices, the lens center position affects the refraction and deflection of light. If the position is inaccurate, it will lead to light deviation and distortion to a certain extent, thus affecting image quality and sharpness. Furthermore, adjusting the lens center position is crucial for achieving adaptive optics. By controlling the lateral position of the lens through electronic control technology, the system can automatically adjust the lens position according to real-time optical conditions and environmental changes to achieve the best imaging effect. This will enhance the adaptability and flexibility of the optical system and improve its performance in different scenarios. This invention mainly uses electronic control technology to precisely adjust the lateral position of the lens, thereby achieving goals such as adjusting optical path compensation, improving image quality, eliminating aberrations, and constructing a high-precision adaptive optics system. In addition, according to the Kerr effect, liquid crystal lenses using blue phase liquid crystal materials can provide twice the refractive index difference with a lateral electric field compared to a longitudinal electric field, resulting in a wider focusing range. However, achieving a lateral electric field in a liquid crystal layer often requires "wall-like" or "pillar-like" electrodes that penetrate the liquid crystal layer. It is very difficult to etch electrodes made of materials such as metal or metal oxides to a thickness comparable to that of the liquid crystal layer, which is not conducive to commercial production. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a liquid crystal lens with laterally controllable lens position. In practical applications, to ensure image quality, the aperture of a liquid crystal lens has specific requirements. However, during the adjustment process, the adjustment amount is often much smaller than the aperture size, necessitating precise adjustment of the lens position. For example, in the field of stereoscopic displays, a lens needs to cover multiple pixel structures. To achieve good display effects, the lens position needs to be precisely aligned with the pixel structure. In this invention, the electrode layer consists of multiple electrodes of the same shape and size. The voltage of each electrode is independently controlled, and the spacing between any two adjacent electrodes is consistent. By modulating the driving voltage with a sinusoidal (or cosine) curve distribution applied to the electrodes, the lateral movement of the lens refractive index distribution can be achieved. The minimum precision of the lateral movement is the distance between two adjacent electrodes, thereby enabling precise adjustment of the liquid crystal lens position. Furthermore, to address the issues of high cost and manufacturing difficulty of "wall-like" or "columnar" electrodes with large etching depths, this invention proposes a liquid crystal lens based on the principle of electric field superposition. Through the strong coupling between pairs of electrodes, the lateral electric field is enhanced by superposition, while the longitudinal electric field is canceled out by superposition. This achieves a lateral electric field in the liquid crystal lens under a single-layer planar electrode structure, thereby reducing the etching depth of the electrode structure.
[0005] This invention is achieved through the following technical solution:
[0006] The structure of this invention, from top to bottom, consists of: an upper substrate, a liquid crystal layer, a dielectric layer, an electrode layer, and a lower substrate.
[0007] The upper and lower substrates can be made of transparent glass, resin, or flexible substrate materials.
[0008] The liquid crystal layer is made of polymer-stabilized blue phase liquid crystal material. Without applied voltage, the liquid crystal layer is isotropic, eliminating the need for molecular alignment treatment on its surface and resulting in a uniform thickness. Under an electric field, the blue phase liquid crystal molecules induce birefringence. As the electric field strength gradually increases, the induced birefringence of the blue phase liquid crystal gradually increases. When the electric field in the liquid crystal layer approaches the saturation electric field of the blue phase liquid crystal material, the induced birefringence of the blue phase liquid crystal approaches saturation.
[0009] The change in refractive index of the blue phase liquid crystal in the liquid crystal layer is based on the Kerr effect under macroscopic conditions: the induced birefringence in the blue phase liquid crystal layer is proportional to the square of the electric field (Δn). ind =λKE 2 The saturated birefringence of blue phase liquid crystal is defined as Δn. sat The induced birefringence formula for blue phase liquid crystals is as follows:
[0010]
[0011]
[0012]
[0013] When the electric field is a transverse electric field, the refractive index difference is n. e and n iso The difference; when the electric field is a longitudinal electric field, the refractive index difference is n. o and n iso The difference in refractive index. Based on this, the transverse electric field can provide a larger refractive index difference than the longitudinal electric field, thus resulting in a larger focusing range.
[0014] The dielectric layer is made of a material with a high dielectric constant of 5-1000.
[0015] The electrode layer is deposited on the inner surface of the lower substrate and consists of electrodes of the same size and shape arranged sequentially. The distance between any two adjacent electrodes is equal, and each electrode can be driven independently. The preferred material for a single electrode is indium tin oxide (ITO), with a thickness of 0.01–0.15 μm. The shape of a single electrode includes, but is not limited to, cuboids, rods, and cylinders. The driving voltage distribution within a single cycle is set to a sinusoidal (or cosine) distribution. Under the applied driving voltage, electric fields exist between electrodes with different driving voltages in the electrode layer. The electric field in the liquid crystal layer satisfies the principle of electric field superposition, meaning the magnitude of the electric field is the sum of the vector fields of the electric fields between the electrodes. The tangent direction at each point on the electric field line is consistent with the direction of the vector superposition of the electric field intensity at that point. Through classification and discussion of the interactions between different electrodes, it is concluded that the transverse electric field superposition enhances while the longitudinal electric field superposition eliminates in the electrode layer, ultimately forming a good transverse electric field in the liquid crystal layer.
[0016] The following description of the accompanying drawings and embodiments is intended to explain the invention in detail, and not to define the scope of the invention. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the structure of a liquid crystal lens with laterally controllable lens position proposed in this invention.
[0018] Figure 2 The electric field state at the central electrode when there is a one-to-one correspondence between the spatially symmetrical electrodes.
[0019] Figure 3 The electric field state at this point when all spatially symmetrical electrodes act on the central electrode.
[0020] Figure 4 The electric field state of the central electrode when the two electrodes on either side of the central electrode act on the asymmetric electrode.
[0021] Figure 5This is a scatter plot of the voltage distribution when the center position of the lens does not move, according to an embodiment of the present invention.
[0022] Figure 6 This is an equipotential line distribution diagram of the liquid crystal layer cross-section when the center position of the lens does not move, according to an embodiment of the present invention.
[0023] Figure 7 This is a comparison diagram of voltage distribution when the center position of the lens is shifted to the left by different units according to an embodiment of the present invention.
[0024] Figure 8 This is a cross-sectional view of the refractive index of the liquid crystal layer when the center position of the lens does not move according to an embodiment of the present invention.
[0025] Figure 9 This is a cross-sectional view of the refractive index of the liquid crystal layer when the center position of the lens is shifted 30 μm to the left in an embodiment of the present invention.
[0026] Figure 10 This is a cross-sectional view of the refractive index of the liquid crystal layer when the center position of the lens is shifted 60 μm to the left in an embodiment of the present invention.
[0027] Figure 11 This is a cross-sectional view of the refractive index of the liquid crystal layer when the center position of the lens is shifted 90 μm to the left in an embodiment of the present invention.
[0028] Figure 12 This is a graph showing the refractive index of the liquid crystal layer when the center position of the lens does not move according to an embodiment of the present invention.
[0029] Figure 13 This is a graph showing the refractive index of the liquid crystal layer when the center position of the lens is shifted 30 μm to the left in an embodiment of the present invention.
[0030] Figure 14 This is a graph showing the refractive index of the liquid crystal layer when the center position of the lens is shifted 60 μm to the left in an embodiment of the present invention.
[0031] Figure 15 This is a graph showing the refractive index of the liquid crystal layer when the center position of the lens is shifted 90 μm to the left in an embodiment of the present invention. Detailed Implementation
[0032] To enable those skilled in the art to further understand the present invention, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the drawings are for illustrative purposes only and are not drawn to scale.
[0033] The structural schematic diagram of the present invention is shown below. Figure 1 As shown, the specific structure is as follows:
[0034] The substrate comprises an upper substrate 1, a liquid crystal layer 2, a dielectric layer 3, an electrode layer 4, and a lower substrate 5. The upper substrate 1 and lower substrate 5 can be made of transparent glass, resin, or a flexible substrate material. The liquid crystal layer 2 is made of a polymer-stabilized blue phase liquid crystal material, which is isotropic when no voltage is applied, eliminating the need for molecular orientation treatment on the surface of the liquid crystal layer 2. The dielectric layer 3 is made of a material with a high dielectric constant of 2-1000. The electrode layer 4 is deposited on the inner surface of the lower substrate 5. The electrodes are preferably made of indium tin oxide (ITO), and each electrode has the same shape and size, with equal distance between the centers of adjacent electrodes.
[0035] Figures 2 to 4 This invention explains the principle behind generating a transverse electric field. It primarily involves applying a sinusoidally distributed voltage to electrode layer 4, and then forming an electric field through strong pairwise coupling between electrodes with different voltage values. Since the electric field is a vector field, according to the principle of electric field superposition, the superposition result of this invention is a transverse electric field. For detailed explanation, the following section uses seven electrodes (E1-E7) as examples to discuss the electric field state at the central electrode under different conditions, and then analyzes the state of the entire electric field. Figure 2 When there is a one-to-one correspondence between the spatially symmetrical electrodes, the electric field state at the central electrode is as follows: Figure 2 It can be seen that E1, E2 and E3 are strongly coupled with E5, E6 and E7 respectively, and the transverse electric field components at E4 are superimposed and enhanced. Figure 3 The electric field state at this point is when all the spatially symmetrical electrodes act on the central electrode. When E1, E2, E3, E5, E6, and E7 all act on E4, the longitudinal electric field components at this point superimpose and cancel each other out. Figure 4 The electric field state of the central electrode when the two electrodes on either side of the central electrode act on the asymmetric electrode is described from... Figure 4 As can be seen, E1 and E2 act on E5, and E3 acts on E6 and E7. At this time, the transverse electric field components at E4 are enhanced by superposition, while the longitudinal electric field components are canceled by superposition. By superimposing the cases of E2-E4, it is concluded that in the entire electric field, the transverse electric field components are enhanced by superposition, while the longitudinal electric field components are canceled by superposition, and finally a good transverse electric field is formed in the liquid crystal layer 2.
[0036] The characteristic parameters used in this embodiment are as follows: the refractive index n of liquid crystal layer 2 when no electric field is applied. iso The coefficient of performance is 1.536. At a wavelength λ of 550 nm, the saturated birefringence is 0.17, the saturated electric field is 2.2 V / μm, and the Kerr coefficient is 13.7 nm / V. 2In this embodiment, the thickness of the liquid crystal layer 2 is 10 μm; the thickness of the dielectric layer 3 is 3 μm, and the dielectric constant is 314; each electrode in the electrode layer 4 is a 1 μm wide square, and the spacing between any two adjacent electrodes is 9 μm; this embodiment uses 20 electrodes as one cycle. It should be noted that the embodiment of the present invention is accurately described by referring to the movement of the lens center position, while the lens can achieve overall translation.
[0037] Figure 5 This is a scatter plot of the voltage distribution when the lens center position remains stationary, according to an embodiment of the present invention. The horizontal axis represents the electrode center position, and the vertical axis represents the corresponding voltage. As can be seen from the figure, the driving voltage exhibits a sinusoidal distribution. In this embodiment, the highest voltage is set to 200V, but this can be proportionally increased or decreased (e.g., when the highest voltage is 100V, the voltage values at other positions are multiplied by 0.5). Setting the voltage to a sinusoidal distribution achieves a more ideal parabolic curve for the refractive index, thereby improving image quality.
[0038] Figure 6 This is an equipotential line distribution diagram of the liquid crystal layer cross-section when the lens center position is not moved, according to an embodiment of the present invention. As can be seen from the diagram, the electric field equipotential lines in region I are basically parallel lines arranged vertically, indicating that the electric field in region I is a transverse electric field. In region II, although both longitudinal and transverse electric field components exist, the equipotential lines are very sparse, indicating that the electric field intensity in this region is very low and can be ignored to a certain extent. Therefore, overall, the electric field distribution in the present invention is approximately a transverse electric field, which can increase the refractive index of the blue phase liquid crystal layer, thereby increasing the focusing range of the lens.
[0039] Figure 7 This is a comparison of the voltage distribution when the lens center position is shifted to the left by different units according to an embodiment of the present invention. The scatter plots for shifting the lens center position to the left by 0 μm, 30 μm, 60 μm, and 90 μm are square, circular, equilateral triangle, and inverted triangle, respectively. As can be seen from the figure, the lens voltages at different center positions are the result of horizontally shifting the same sinusoidal distribution, without any stretching change, indicating that the present invention can achieve lateral electronic control of the lens position. Furthermore, when the lens center position changes, the voltage of a single electrode changes accordingly, and the refractive index difference also changes, thereby achieving adjustment of the focal length range.
[0040] Figure 8 This is a cross-sectional view of the refractive index distribution when the center position of the lens in an embodiment of the present invention remains unchanged. It can be seen from the figure that the refractive index exhibits a periodic distribution. By integrating the refractive index in the cross-sectional view, the following can be obtained: Figure 10 The refractive index curve corresponding to the center position of the lens in the embodiment of the present invention is an important basis for evaluating the imaging quality of the liquid crystal lens. Figure 9 , Figure 10 , Figure 11 These are the refractive index profiles when the lens center is shifted to the left by 0μm, 30μm, 60μm, and 90μm, respectively. The principle is the same as... Figure 8 Same. Comparison Figures 7 to 11 It can be seen that in a liquid crystal lens structure of the present invention, the voltage difference between two adjacent electrodes in the electrode layer is not equal; the equivalent refractive index distribution in the liquid crystal layer is not related to the absolute magnitude of the driving voltage on the corresponding electrode below it, but is positively correlated with the magnitude of the voltage difference between the two adjacent electrodes below it.
[0041] Figure 12 This is a refractive index curve and a voltage distribution curve when the center position of the lens does not move, according to an embodiment of the present invention. Figure 5 The square scatter points are consistent. At this time, the highest value (position 52) and the lowest value (position 6) of the refractive index curve differ by 0.1, and the refractive index in the liquid crystal layer presents a relatively ideal parabolic curve.
[0042] Figure 13 This is a refractive index curve and a voltage distribution curve when the lens center position is shifted 30 μm to the left according to an embodiment of the present invention. Figure 7 With the scatter points in the middle circle consistent, the difference between the highest value (position 22) and the lowest value (position 176) of the refractive index curve is 0.0974. This shows that the overall size and period of the refractive index curve are consistent with... Figure 12 The overall size and period of the refractive index curve are almost identical, meaning that the aperture of the lens has not changed. Figure 14 and Figure 15 The figures show the refractive index curves when the lens center is shifted to the left by 60 μm and 90 μm, respectively, and their overall refractive index curves are compared with... Figure 12 , Figure 13 Almost identical, but relatively Figure 12 The curves in the figure were shifted to the left by 60 μm and 90 μm, respectively.
Claims
1. A position-modulated liquid crystal lens based on the principle of electric field superposition, characterized in that, include: The upper substrate (1), liquid crystal layer (2), dielectric layer (3), electrode layer (4), and lower substrate (5) are provided. The upper substrate (1) and lower substrate (5) are made of transparent glass, resin, or flexible substrate. The liquid crystal layer (2) is made of blue phase liquid crystal. The dielectric layer (3) is made of a material with a high dielectric constant. The electrode layer (4) is a single-layer planar electrode structure, which is composed of multiple independently driven electrodes arranged in sequence, and the distance between any two adjacent electrodes is equal. The electric field in the liquid crystal layer (2) is a transverse electric field. The strong coupling between the electrodes in the electrode layer (4) is used to superimpose and enhance the transverse electric field while eliminating the longitudinal electric field. The driving voltage distribution on the electrode layer (4) satisfies a sine or cosine curve distribution. By modulating the driving voltage with a sine or cosine curve distribution applied to the electrode, the lateral movement of the lens refractive index distribution can be achieved.
2. The position-modulated liquid crystal lens based on the principle of electric field superposition as described in claim 1, characterized in that, The liquid crystal layer (2) is made of polymer-stabilized blue phase liquid crystal material.
3. The position-modulated liquid crystal lens based on the principle of electric field superposition as described in claim 1, characterized in that, The electrode layer (4) is plated on the inner surface of the lower substrate (5) and is composed of multiple electrodes of the same shape and size arranged in sequence. Each electrode is independently driven and the distance between any two adjacent electrodes is equal. The shapes of individual electrodes include cuboids, rods, and cylinders.
4. The position-modulated liquid crystal lens based on the principle of electric field superposition as described in claim 1, characterized in that, The minimum precision of movement in the electrode layer (4) is the distance between two adjacent electrodes.
5. The position-modulated liquid crystal lens based on the principle of electric field superposition as described in claim 1, characterized in that, Within a liquid crystal lens structure, the voltage difference between two adjacent electrodes in the electrode layer (4) is not equal; the equivalent refractive index distribution in the liquid crystal layer (2) is independent of the absolute magnitude of the driving voltage on the corresponding electrode below it, but positively correlated with the magnitude of the voltage difference between the two adjacent electrodes below it.