Liquid crystal cell with controllable cell thickness

Abstract

A liquid crystal cell with controllable cell thickness comprises a first alignment layer, a first ITO layer, a first glass substrate, and a liquid crystal cell chamber. A hole is formed in the rear glass of the liquid crystal cell chamber to allow a piezoelectric connecting rod to extend into the cell. The extending end of the piezoelectric connecting rod is sequentially provided with a second alignment layer, a second ITO layer, and a second glass substrate. The exposed end of the piezoelectric connecting rod is provided with a piezoelectric ceramic. When energized, the piezoelectric ceramic deforms, thereby driving the second glass substrate to move, changing the spacing between the first and second alignment layers and thereby varying the thickness of the liquid crystal layer. Liquid crystal injection and evaporation are controlled by an external circulation system. This invention enables flexible light field modulation, significantly increasing the amount of phase modulation, and can be applied to wide-band optical systems, effectively improving the damage threshold of liquid crystal elements.

Description

Technical Field

[0001] The invention belongs to the field of liquid crystal light field regulation, and in particular relates to a liquid crystal cell with controllable cell thickness. Background Art

[0002] In recent years, tunable light field manipulation components have flourished in fields such as high-precision measurement, holography, and VR / AR. Research on liquid crystal-based optical components, such as liquid crystal cells, electrically controlled wave plates, and liquid crystal gratings, has deepened. This has led to new inventions based on diverse principles and designs, such as binary liquid crystal panels based on amplitude modulation and liquid crystal gratings based on phase modulation. These devices are widely used in various applications, such as 3D printing masks, liquid crystal phased array radars, and liquid crystal anti-counterfeiting QR codes. The tunable birefringence of liquid crystals allows for flexible and diverse functionalities. However, the cell thickness of these components, whether pixelated or integrated, is not adjustable. The structure of the liquid crystal cell is fixed upon encapsulation, and the cell thickness is determined by the diameter of the microparticles used to seal the cell. Consequently, component performance cannot be altered. In particular, phase modulation relies solely on voltage-controlled birefringence. Consequently, control over multiple wavelengths and energy gradients is limited, necessitating the fabrication of custom liquid crystal cells to meet varying requirements. At the same time, the growing development of high-power lasers has led to higher and higher requirements for the damage threshold of components. Ordinary liquid crystal boxes are difficult to control or compensate for changes in physical parameters under thermal effects, so using them in high-power laser systems will cause errors. Summary of the Invention

[0003] In order to solve the above-mentioned shortcomings of the traditional liquid crystal cell, the present invention proposes a liquid crystal cell with controllable cell thickness, which can control light fields of multiple wavelengths and different energies.

[0004] The principles of the present invention are as follows:

[0005] The phase retardation δ caused by liquid crystal can be expressed by the formula Indicates, where Δn is the birefringence of the liquid crystal, which is controlled by an external voltage, and its maximum value is usually around 0.2. And d is the thickness of the liquid crystal cell, which is usually controlled by fixed-size particles in traditional liquid crystal cells - for example, for visible light or near-infrared light, the diameter of the particles is generally within 10μm, but compared to the terahertz band (wavelength 30μm-3000μm), the thickness of the liquid crystal cell is obviously not enough to achieve the phase modulation effect. It can also be seen that the influence of temperature on the light field modulation of the liquid crystal cell is extremely large. The deformation caused by temperature and the change of the optical parameters of the material make the modulation effect of the liquid crystal cell inaccurate or even destroyed. In order to enable the same liquid crystal cell to achieve the regulation of a wide spectrum and high-energy light field.

[0006] 1) The transformation of vertical incident light waves by the liquid crystal cell thickness can be described by the Jones matrix. For the polarization components in the X and Y directions, they are E x ,Ey The polarization of a monochromatic wave can be expressed by the matrix After passing through the liquid crystal cell, the outgoing light matrix is expressed as Then there is

[0007]

[0008] Where θ is the azimuth angle of the liquid crystal molecules, which represents the coordinate transformation after the light beam is incident.

[0009] As can be seen from the above formula, the modulation of the phase delay δ is extremely critical. Ordinary liquid crystal cells can only adjust the birefringence to cause changes in phase delay, while the key parameter of the liquid crystal cell thickness cannot be modulated. For light of different wavelengths, changes in cell thickness can regulate its light intensity and polarization state. Therefore, piezoelectric ceramics are used in this patent to accurately control the cell thickness. Piezoelectric ceramics have inverse piezoelectricity, that is, they convert electrical energy into mechanical energy under the control of an external electric field. Figure 1 The annular piezoelectric ceramic is connected to the front glass. The deformation caused by this deformation drives the front glass to move, thus changing the distance between the front glass and the box. Generally speaking, the deformation of the piezoelectric ceramic after modulation is linearly related to the voltage, so the box thickness d can be expressed by the following formula:

[0010] d=KU

[0011] Where K is the proportional coefficient and U is the loading voltage.

[0012] The technical solutions adopted in the present invention are as follows:

[0013] A liquid crystal cell with controllable cell thickness comprises a liquid crystal cell chamber consisting of a first orientation layer, a first indium tin oxide (ITO) layer, and a first glass substrate. The liquid crystal cell chamber is characterized in that a hole is formed on the inner glass of the liquid crystal cell chamber for a piezoelectric connecting rod to extend into; the extending end of the piezoelectric connecting rod is provided with a second orientation layer, a second ITO layer, and a second glass substrate in sequence; the exposed end of the piezoelectric connecting rod is provided with a piezoelectric ceramic. When the piezoelectric ceramic is energized, it deforms, thereby driving the second glass substrate to move, thereby changing the distance between the first orientation layer and the second orientation layer, thereby changing the thickness of the liquid crystal layer.

[0014] Preferably, the liquid crystal cell further comprises a liquid crystal circulation structure arranged outside the liquid crystal cell chamber, which is responsible for the injection and extraction of liquid crystal.

[0015] Preferably, the liquid crystal circulation structure is composed of a hose and a pump. Liquid crystal is stored in the liquid crystal box chamber. One end of the hose passes into the liquid crystal box chamber, and the other end is connected to the pump to realize the injection and suction of liquid crystal, as well as exchange heat with the outside world to achieve heat dissipation.

[0016] Preferably, the connection between the extending end of the piezoelectric connecting rod and the outer wall of the liquid crystal box chamber is connected by elastic rubber and curing glue to prevent liquid crystal leakage.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The thickness of the working area of the liquid crystal cell of this invention can be flexibly controlled using piezoelectric ceramics, while the liquid crystal is injected and discharged by an external circulation system. This allows for flexible light field modulation, significantly increasing the amount of phase modulation, and is applicable to a variety of optical systems. Furthermore, the circulation of the liquid crystal reduces the impact of thermal effects on the liquid crystal cell, effectively improving the damage threshold of the liquid crystal element. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0020] Figure 1 This is a schematic diagram of the structure decomposition of the variable cell thickness liquid crystal cell of the present invention, 1 is the external circulation structure, 2 is the liquid crystal cell chamber, and 3 is the piezoelectric connecting rod structure.

[0021] Specifically, in the figure: 1-1 pump; 1-2 hose; 2-1 left side glass; 2-2 right side glass; 2-3 lower side glass; 2-4 upper side glass; 2-5 rear side glass; 2-6 first glass substrate; 2-7 first ITO layer; 2-8 first orientation layer; 2-9 sealing rubber ring; 3-1 second orientation layer; 3-2 second ITO layer; 3-3 second glass substrate; 3-4 piezoelectric connecting rod; 3-5 piezoelectric ceramic. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Example:

[0024] 1) The variable-thickness liquid crystal cell utilizes an external circulation structure, a liquid crystal cell chamber, and a piezoelectric linkage. The piezoelectric linkage moves back and forth to adjust the thickness of the working area, simultaneously changing the volume of the liquid crystal cell chamber. Therefore, a compression pump is required to pump the liquid crystal stored in the liquid crystal cell chamber out or in.

[0025] 2) The liquid crystal cell chamber is a rectangular glass empty box structure. Prepare high-quality quartz glass as the base material of the liquid crystal cell, and use laser cutting or other methods to punch two small holes on both sides of the upper glass and a large hole on the rear glass. The diameter of the large hole is slightly larger than the light-clearing diameter; cut a circular quartz glass of the same size as the light-clearing diameter;

[0026] The front glass and the cut circular quartz glass are used as the substrate, and an ITO film is coated by electron beam evaporation or magnetron sputtering. The liquid crystal alignment agent is spin-coated on the ITO film, and the alignment layer is prepared by friction alignment, photo-alignment, etc.

[0027] The liquid crystal cell chamber is prepared using a glass bonding process. A relatively hard rubber ring is inserted into the large hole on the back of the chamber as a guide rail, and flexible tubes are inserted into the two small holes on the upper side. Curing glue is used to solidify the joints to form a closed space.

[0028] 3) The inner wall of the first glass substrate on the front side is coated with an ITO film, and an orientation agent is spin-coated on the film to align it. A circular hole is dug in the center area of the rear side of the glass chamber to facilitate the entry of the piezoelectric connecting rod structure; two small holes are dug on the upper side of the glass chamber to connect to the circulation structure hose;

[0029] 4) The front end of the piezoelectric connecting rod structure, from the inside out, consists of the second alignment layer, the second ITO layer, and the second glass substrate. The glass substrate is connected to a hollow connecting rod, which is sealed with a rubber ring to prevent liquid crystal leakage. A piezoelectric ceramic is attached to the end of the hollow connecting rod. An external voltage controls the expansion and contraction of the piezoelectric ceramic, which in turn controls the forward and backward movement of the connecting rod. This causes the liquid crystal thickness between the alignment layers to change, achieving a long-stroke liquid crystal cell thickness modulation effect.

[0030] 5) Changes in the cell's thickness mean changes in the volume of the liquid crystal chamber. Therefore, a flexible hose and a compression pump are used to connect the chambers and store and discharge the liquid crystal. Furthermore, considering the thermal effects of high-power lasers, the hose exchanges heat with the outside and circulates the liquid crystal, minimizing the effects of laser radiation.

[0031] This invention achieves the function of controlling the phase of the light field over a large range by effectively controlling the thickness of the liquid crystal cell. It can effectively reduce the adverse effects of physical deformation and refractive index changes caused by high-power laser irradiation, and has wide-spectrum, high-precision and tunable functions.

[0032] While embodiments of the present invention have been described above, these embodiments do not exhaustively describe all details and do not limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the above description. These embodiments are selected and described in detail in this specification in order to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better utilize the present invention and its modifications. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A liquid crystal cell with controllable cell thickness, comprising a liquid crystal cell chamber encapsulated by a first glass substrate, left glass, right glass, upper glass, lower glass, and rear glass, wherein the left glass and the right glass are oppositely disposed, the upper glass and the lower glass are oppositely disposed, and the first glass substrate and the rear glass are oppositely disposed. A first ITO layer and a first alignment layer are sequentially disposed on the inner wall of the first glass substrate facing the rear glass, characterized in that: A hole is opened on the rear glass of the liquid crystal cell chamber for the piezoelectric connecting rod to extend into; the inserted end of the piezoelectric connecting rod is provided with a second alignment layer, a second ITO layer, and a second glass substrate in sequence from the inside out; the exposed end of the piezoelectric connecting rod is provided with a piezoelectric ceramic. When the piezoelectric ceramic is energized, it deforms, thereby driving the second glass substrate to move, thereby changing the distance between the first alignment layer and the second alignment layer, thereby changing the thickness of the liquid crystal layer; It also includes a liquid crystal circulation structure arranged outside the liquid crystal cell chamber, which is responsible for the injection and suction of liquid crystal.

2. The liquid crystal cell with controllable cell thickness according to claim 1, characterized in that: The liquid crystal circulation structure is composed of a hose and a pump. Liquid crystal is stored in the liquid crystal box chamber. One end of the hose passes into the liquid crystal box chamber, and the other end is connected to the pump to realize the injection and suction of liquid crystal, as well as exchange heat with the outside world to achieve heat dissipation.

3. The liquid crystal cell with controllable cell thickness according to any one of claims 1-2, characterized in that: The connection between the extending end of the piezoelectric connecting rod and the outer wall of the liquid crystal box chamber is connected by elastic rubber and curing glue to prevent liquid crystal leakage.

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