CN102073174A - Liquid crystal optical wedge element - Google Patents

Abstract

The invention belongs to a liquid crystal wedge device in an optoelectronic device, comprising upper and lower transparent substrates with conductive layers and alignment layers on both inner surfaces, and two rows of spacers with different heights arranged in parallel between the two ends of the alignment layers of the two transparent substrates. sub, and two transparent substrates and conductive layers on them, alignment layers and spacers are packaged into a wedge-shaped cavity housing, and the wedge-shaped liquid crystal is arranged in the cavity. In this invention, the poured liquid crystal is directly formed into a liquid crystal prism according to the wedge-shaped cavity formed by the upper and lower substrates and two rows of spacers, which improves the flatness of the liquid crystal slope, and the orientation direction of the liquid crystal molecules in the cavity can be aligned with that of the liquid crystal. The two rows of spacers are vertical or parallel to the two rows of spacers. Therefore, the invention has the advantages of simple structure and manufacturing process, low production cost, high smoothness of wedge-shaped liquid crystal slope and uniform distribution of refractive index during operation, which effectively improves the quality of tracking and scanning beams of liquid crystal optical wedge devices and the accuracy of tracking and scanning. characteristics such as sex and efficiency.

Description

A liquid crystal wedge device

technical field

The invention belongs to the technical field of liquid crystal optoelectronic devices and manufacture, and in particular relates to a liquid crystal optical wedge device. The liquid crystal wedge device can be widely used in free-space optical communication and lidar for high-precision acquisition, tracking and targeting (ATP) of targets, etc. Two liquid crystal wedge devices are used for two-dimensional tracking and scanning of a single beam.

Background technique

In applications such as free-space optical communication and lidar, the high-precision acquisition, tracking and targeting (ATP) technology of laser beams is a very important key technology and difficulty. The level of ATP technology directly affects the overall performance indicators of the system. Traditional ATP solutions usually use mechanical methods such as universal joints. Due to the influence of factors such as large size, heavy weight, high power consumption and mechanical wear, non-mechanical ATP technology has gradually attracted attention. At present, the commonly used non-mechanical light beam adjustment and control methods mainly include microlens array technology, MEMS (micro-electro-mechanical system) technology, electro-wetting micro-prism technology and liquid crystal optical phased array technology; among them, liquid crystal optical phased array technology It is a new type of technology that is closest to practicality at present. As a programmable (adjustable) phase modulation device, liquid crystal optical phased array (LCOPA) uses nematic liquid crystal with low driving voltage and large phase modulation depth as the electro-optic material for phase modulation, making the device have a volume Unique advantages such as small size, light weight, low power consumption, and easy integration with microelectronic control circuits; not only solve the problem of high-resolution laser beam pointing and fast, flexible control of space scanning, but also make the optoelectronic system more integrated. It has stronger flexible control capability and lower manufacturing cost; it has important application value in the fields of free space optical communication, infrared countermeasures and target tracking. However, the production cycle of liquid crystal optical phased array devices is relatively long, the yield is low, the number of pixel electrodes that need to be independently programmed and controlled is large, and the driving circuit is complicated. These factors hinder the popularization and application of liquid crystal optical phased array devices. The recent emergence of liquid crystal prisms based on photosensitive polymers also enables adjustable tracking and scanning of beam angles. Compared with liquid crystal optical phased array devices, the manufacturing process and technical difficulty of liquid crystal prisms based on photosensitive polymers are greatly simplified. This device is disclosed in the following paper: "Liquid-crystal beam steering device with a photopolymer prism", (" APPLIED PHYSICSLETTERS "Volume 87, No. 9, 2005, P091110 page, author: Jae-Hong Parka and Iam Choon Khoo); the basic structure of this device is to include the upper and lower two working surfaces as a transparent cubic liquid crystal cell and its inner Cavity, and a wedge-shaped polymer is filled in the cavity of the liquid crystal cell, so that the liquid crystal filled in the rest of the cell forms a corresponding wedge shape. Due to the difference in refractive index between liquid crystal and polymer, a wedge-shaped optical path distribution will be generated for the incident light wave; after different voltages are applied to the conductive layers on the upper and lower working surfaces of the liquid crystal cell, the refractive index of the liquid crystal will change, resulting in The wedge angle of the wedge-shaped optical path distribution also changes accordingly, thereby realizing the scanning of the light beam. The polymer prism in the liquid crystal cell of the device is formed by curing the polymer through ultraviolet exposure. The formed polymer prism is related to many factors, including: the diffusion and reaction constant of the polymer, the thickness of the polymer layer, and the power of ultraviolet light. wait. These factors will reduce the smoothness of the wedge-shaped slope, and then affect the smoothness of the overlapping wedge-shaped liquid crystal slope and the uniformity of the refractive index distribution during operation, that is, have a bad influence on the quality of the tracking and scanning beams; in addition, due to The device needs to be equipped with a photosensitive polymer, and its production process is complicated, quality is difficult to guarantee, and production cost is also high; therefore, the above-mentioned technology has complex structure and production process, difficult quality assurance, high production cost, and the resulting tracking, scanning Defects such as poor quality of the aiming beam.

Contents of the invention

The purpose of the present invention is to improve and design a liquid crystal optical wedge device on the basis of the background technology, so as to simplify its structure and production process, reduce production costs, effectively improve the smoothness of the wedge-shaped liquid crystal slope and the tracking and scanning beam of the liquid crystal optical wedge device The quality, as well as the uniformity of the refractive index distribution during work, the accuracy of tracking and scanning, and high efficiency.

The solution of the present invention is to aim at the defects of the background technology, and change the upper and lower substrates of the liquid crystal wedge device with conductive layers and alignment layers from the traditional parallel arrangement to use the upper and lower substrates as inclined planes The wedge-shaped setting makes the filled liquid crystal directly form a liquid crystal prism according to the wedge-shaped cavity formed by the upper and lower substrates, thereby saving the wedge-shaped photosensitive polymer that must be filled in the liquid crystal cell in the background technology, and also Avoiding the adverse effects on tracking and scanning beam quality due to the existence of the wedge-shaped polymer; the size of the wedge angle formed by the upper and lower substrates of the present invention is determined by the Two rows of spacers with different heights (diameters) are set (that is, determined by adjusting the diameter difference between the two rows of spacers or adjusting the distance between the two rows of spacers), and then poured into liquid crystals after conventional initial fixation and sealed packaging treatment, that is The liquid crystal wedge device of the present invention is obtained. Therefore, the liquid crystal wedge device of the present invention comprises upper and lower transparent substrates with conductive layers and alignment layers on both inner surfaces and two rows of spacers parallel to each other between the two ends of the alignment layers of the two transparent substrates. The conductive layer, alignment layer and spacers on it are packaged into the casing of the cavity, and the liquid crystal arranged in the cavity. The key lies in the spacer arranged in parallel between the two ends of the alignment layer of the two transparent substrates in the liquid crystal wedge device. It is two rows of spacers with different heights (diameters), the upper and lower transparent substrates (with conductive layer and orientation layer) are respectively fixed on the upper and lower parts of the two rows of spacers through the orientation layer on it, forming the upper and lower two A wedge-shaped cavity with a transparent substrate as an inclined plane, so that the liquid crystal poured into the cavity is also in a corresponding wedge shape; the upper and lower transparent substrates with a conductive layer and an alignment layer are arranged in parallel at both ends of the alignment layer of the two transparent substrates. The two rows of spacers and the liquid crystals arranged in the wedge-shaped cavity are packaged and sealed as a whole in a conventional manner.

The orientation direction of the liquid crystal molecules (the long axis direction of the liquid crystal molecules) arranged in the wedge-shaped cavity is perpendicular to the two rows of spacers or parallel to the two rows of spacers. The wedge angle of the wedge-shaped cavity is 0.001°-2°. The spacer is a spherical spacer or a strip spacer.

In the present invention, the upper and lower substrates on the liquid crystal wedge device are used as inclined planes, so that the liquid crystal cavity formed is wedge-shaped, and the liquid crystal poured in is formed according to the wedge formed by the upper and lower substrates and two rows of spacers. The liquid crystal prism is directly formed in the cavity, which improves the flatness of the wedge-shaped liquid crystal slope, and the orientation direction of the liquid crystal molecules in the cavity can be arranged vertically or parallel to the two rows of spacers; thus it has the advantages of structure and production The technology is simple, the production cost is low, the smoothness of the wedge-shaped liquid crystal slope is high, and the refractive index distribution is uniform during operation, which effectively improves the quality of the tracking and scanning beam of the liquid crystal optical wedge device, and the accuracy and efficiency of tracking and scanning. The liquid crystal optical wedge device of the present invention can not only use a single device to perform one-dimensional tracking and scanning of a single beam, but also use two liquid crystal optical wedge devices to perform two-dimensional tracking and scanning of a single beam.

Description of drawings

Fig. 1 is structure of the present invention and embodiment 1 structural representation (sectional view);

Fig. 2 is a schematic structural view (sectional view) of Embodiment 2 of the present invention;

Fig. 3 is a coordinate graph of the angle measurement results of beam deflection under different loading voltages in Example 1.

In the figure: 1-1, 2-1: upper and lower transparent substrates, 1-2, 2-2: conductive layer, 1-3, 2-3: alignment layer, 3-1, 3-2: spacer, 4. Housing, 5. Liquid crystal.

Detailed ways

Embodiment 1: In this embodiment, a liquid crystal wedge device with a wedge angle of 0.03° and a device effective area (length×width) of 10×10mm is an example, and the upper and lower transparent substrates 1-1 and 2-1 are commercially available with conductive The liquid crystal display of layer 1-2, 2-2 uses ITO conductive glass, thick 1.1mm, wherein conductive layer 1-2, 2-2 thick 100nm; Spin-coat polyimide (PI) film respectively on it by conventional method As alignment layers 1-3, 2-3, the present embodiment performs rubbing treatment along the slope direction after the polyimide (PI) film is solidified, so that the molecular orientation (major axis) poured into the liquid crystal 5 is along the slope direction (i.e. perpendicular to two rows of spacers); the spacer 3-1 has a diameter of 6 μm, and the spacer 3-2 has a diameter of 11 μm. After placing the spacers 3-1 and 3-2 in ethanol according to the conventional method, and then using The two ends of the lower substrate 2-2 are fixed by the method of blowing, and then the upper substrate 2-1 is placed on the spacers 3-1 and 3-2, and the upper and lower substrates 1-1 and 2-1 are connected by ultraviolet curing glue. After initial fixing with the spacers 3-1 and 3-2, the liquid crystal 5 is poured into the cavity, and finally packaged with UV-curable glue to make the liquid crystal wedge device of this embodiment.

Embodiment 2: In this embodiment, a liquid crystal wedge device with a wedge angle of 0.6° and a device effective area (length×width) of 10×10 mm is taken as an example. In this embodiment, the polyimide (PI) film layer is cured and the two Rub the direction parallel to the row of spacers so that the molecular orientation (major axis) poured into the liquid crystal 5 is arranged in parallel with the two rows of spacers. The diameter of the spacer 3-1 is 3 μm, and the diameter of the spacer 3-2 is 100 μm; All the same as in Example 1.

When the liquid crystal wedge devices obtained in the above two embodiments are used alone, one-dimensional tracking and scanning of a single beam can be realized when the two conductive layers 1-2, 2-2 on the transparent substrate 1-1, 2-1 are loaded with varying voltages. When the two liquid crystal wedge devices obtained in embodiment 1 and embodiment 2 are superimposed in the same direction as the molecular orientation (major axis) of liquid crystal 5, and the voltage that changes are applied to the two liquid crystal wedge devices, then Realize single-beam two-dimensional tracking and scanning.

Claims (4)

1. A kind of liquid crystal light wedge device, comprises the upper and lower transparent substrates that are all with conductive layer and alignment layer by two inner surfaces and two rows of spacers that are arranged in parallel between two transparent substrate alignment layer two ends, two transparent substrates And the conductive layer, alignment layer and spacer on it are packaged into a casing of the cavity, and the liquid crystal arranged in the cavity is characterized in that the liquid crystal wedge device is arranged in parallel between the two ends of the alignment layer of the two transparent substrates. The spacers are two rows of spacers with different heights. The upper and lower transparent substrates are respectively fixed on the upper and lower parts of the two rows of spacers through the alignment layer on them, forming a wedge-shaped cavity with the upper and lower transparent substrates as inclined planes. , so that the liquid crystal poured into the cavity is also in a corresponding wedge shape; the upper and lower transparent substrates with a conductive layer and an orientation layer, two rows of spacers arranged in parallel between the two ends of the orientation layer of the two transparent substrates and the The liquid crystal in the wedge-shaped cavity is sealed and fixed as a whole according to conventional packaging. 2. The liquid crystal optical wedge device according to claim 1, wherein the alignment direction of the liquid crystal molecules disposed in the wedge-shaped cavity is perpendicular to or parallel to the two rows of spacers. 3. The liquid crystal wedge device according to claim 1, characterized in that the wedge angle of the wedge-shaped cavity is 0.001°-2°. 4. The liquid crystal wedge device according to claim 1, characterized in that said spacers are spherical spacers or strip spacers.

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