A light field display based on liquid crystal polarization grating

Abstract

The invention discloses a light field display screen based on a liquid crystal polarization grating, and belongs to the field of displays. The phase source, circular polarizer, liquid crystal polarization grating, quarter wave plate and linear polarizer of the light field display screen based on the liquid crystal polarization grating are arranged in sequence, the phase source emits vertically polarized linear polarized light, the polarization state of the linear polarized light is converted into circular polarization after passing through the circular polarizer, the circular polarized light is converted into a first-order light beam and a part of the unconverted zero-order light beam through the liquid crystal polarization grating, the polarization state of the zero-order light beam is converted into linear polarization after passing through the quarter wave plate, and is filtered by the linear polarizer, the polarization state of the first-order light beam after passing through the quarter wave plate is perpendicular to the zero-order light beam, and the first-order light beam passes through the linear polarizer. Through the above design, the light field display screen can filter out the zero-order light beam without affecting the energy size of the first-order light beam, so as to achieve the purpose of improving the contrast of the light field display screen.

Description

Technical Field

[0001] The invention relates to the field of displays, in particular to a light field display screen based on liquid crystal polarization gratings. Background Art

[0002] The naked-eye 3D display based on diffraction optics has the advantages of small thickness, light weight, flexible design and precise light manipulation, and thus has been widely used. The key component of the current diffraction-type light field 3D display system based on pixel grating is the pixelated beam control device, which is mainly a grating with a surface relief structure. However, the grating with a surface relief structure has strong zero-order diffraction light and low diffraction efficiency, which affects the imaging quality in naked-eye 3D display.

[0003] Although the binary grating structure can eliminate the zero-order diffraction light, the binary grating structure is complex in design and has high requirements for the preparation process, which is not conducive to production. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide a light field display screen based on a liquid crystal polarization grating which has a simple structure, low requirements for the preparation process and eliminates zero-order diffraction light.

[0005] One of the purposes of the present invention is achieved by the following technical solution:

[0006] A light field display screen based on a liquid crystal polarization grating comprises a phase source, a circular polarizer, a liquid crystal polarization grating, a quarter wave plate and a linear polarizer, wherein the phase source, the circular polarizer, the liquid crystal polarization grating, the quarter wave plate and the linear polarizer are arranged in sequence, the phase source emits vertically polarized linear polarized light, the polarization state of the linear polarized light is converted into circular polarization after passing through the circular polarizer, the circular polarized light is converted into a first-order light beam and a part of the unconverted zero-order light beam after passing through the liquid crystal polarization grating, the polarization state of the zero-order light beam is converted into linear polarization after passing through the quarter wave plate and is filtered by the linear polarizer, the polarization state of the first-order light beam is perpendicular to the zero-order light beam after passing through the quarter wave plate, and the first-order light beam passes through the linear polarizer.

[0007] Furthermore, after receiving the circularly polarized light, the liquid crystal polarization grating deflects each sub-pixel of the circularly polarized light in different directions, and the liquid crystal director rotates in a plane perpendicular to the liquid crystal director.

[0008] Furthermore, the distribution formula of the liquid crystal director direction at each position is as follows:

[0009]

[0010] In the formula, Λ x is the lateral period of the liquid crystal polarization grating, Λ zis the longitudinal period of the liquid crystal polarization grating, x and z are the coordinates of the liquid crystal director in a three-dimensional rectangular coordinate system established with a plane perpendicular to the liquid crystal director as the bottom surface, and θ and α are the deflection angles of the light beam.

[0011] Furthermore, θ = sin -1 (kλ / Λ x ), where k is the diffraction order and λ is the wavelength of the incident light.

[0012] Furthermore, the polarization state of the linearly polarized light is converted into left-handed circular polarization after passing through the circular polarizer.

[0013] Furthermore, the first-order light beam converted by the liquid crystal polarization grating is right-handed circularly polarized.

[0014] Furthermore, the polarization state of the zero-order light beam converted by the liquid crystal polarization grating is left-handed circular polarization.

[0015] Further, when the wavelength of the incident light emitted by the phase source is 500 nm and the deflection angle θ is 30°, the lateral period of the liquid crystal polarization grating is 1000 nm.

[0016] Compared with the prior art, the phase source, circular polarizer, liquid crystal polarization grating, quarter wave plate and linear polarizer of the light field display screen based on the liquid crystal polarization grating of the present invention are arranged in sequence, the phase source emits vertically polarized linear polarized light, the polarization state of the linear polarized light is converted into circular polarization after passing through the circular polarizer, the circular polarized light is converted into a first-order light beam and a part of the unconverted zero-order light beam through the liquid crystal polarization grating, the polarization state of the zero-order light beam is converted into linear polarization after passing through the quarter wave plate and is filtered by the linear polarizer, the polarization state of the first-order light beam after passing through the quarter wave plate is perpendicular to the zero-order light beam, the first-order light beam passes through the linear polarizer, through the above design, the light field display screen can filter out the zero-order light beam without affecting the energy size of the first-order light beam, thereby achieving the purpose of improving the contrast of the light field display screen. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural diagram of a light field display screen based on a liquid crystal polarization grating of the present invention;

[0018] Figure 2 for Figure 1 A schematic diagram of a pixel liquid crystal grating array of a light field display screen based on a liquid crystal polarization grating;

[0019] Figure 3 This is an optical principle diagram of a light field display screen based on a liquid crystal polarization grating of the present invention;

[0020] Figure 4 This is an optical effect diagram of a light field display screen based on a liquid crystal polarization grating according to the present invention.

[0021] In the figure: 1. Phase source; 2. Liquid crystal polarization grating; 3. Circular polarizer; 4. Quarter wave plate; 5. Linear polarizer. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be another intermediate component through which it is fixed. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0025] See also Figure 1 The present application discloses a light field display screen based on a liquid crystal polarization grating, comprising a phase source 1, a liquid crystal polarization grating 2, a circular polarizer 3, a quarter wave plate 4 and a linear polarizer 5. The phase source 1, the circular polarizer 3, the liquid crystal polarization grating 2, the quarter wave plate 4 and the linear polarizer 5 are arranged in sequence.

[0026] Phase source 1 emits linearly polarized light.

[0027] The circular polarizer 3 is used to convert linear polarized light into circular polarized light, and the circular polarized light converted by the circular polarizer 3 is left-handed circular polarization.

[0028] Please continue reading Figure 2 , the liquid crystal polarization grating 2 deflects each sub-pixel of the circularly polarized light in different directions, and the liquid crystal director rotates in a plane perpendicular to it. The distribution formula of the liquid crystal director direction at each position is as follows:

[0029]

[0030] In the formula, Λ x is the lateral period of the grating, Λ z is the longitudinal period of the grating, x and z are the coordinates of the liquid crystal director in a three-dimensional rectangular coordinate system with a plane perpendicular to the liquid crystal director as the bottom surface, and θ and α are the deflection angles of the light beam.

[0031] After the liquid crystal polarization grating 2 receives the circularly polarized light, the deflection angle of the light beam is determined by the following formula, specifically:

[0032] θ=sin -1 (kλ / Λ x );

[0033] Where k is the diffraction order and λ is the wavelength of the incident light.

[0034] In actual use, due to factors such as light alignment error and chiral molecule concentration error, part of the circularly polarized light cannot be converted and is emitted in the original direction, which is the zero-order beam. The circular polarization direction and propagation direction of the zero-order beam do not change, while the circular polarization direction of the first-order beam is opposite and the propagation direction changes. The first-order beam converted by the liquid crystal polarization grating 2 is right-handed circularly polarized.

[0035] The quarter wave plate 4 converts the zero-order beam and the first-order beam into beams with linear polarization directions perpendicular to each other. The polarization state of the zero-order beam is converted into vertical polarization.

[0036] The linear polarizer 5 filters the vertically polarized light beam and filters the zero-order light beam.

[0037] Please continue reading Figure 3 as well as Figure 4 When a light field display screen based on a liquid crystal polarization grating is used, a phase source 1 emits vertically polarized linearly polarized light, and a circular polarizer 3 converts the linearly polarized light into left-handed circularly polarized light; the left-handed circularly polarized light passes through a liquid crystal polarization grating 2 to obtain a zero-order beam and a first-order beam. Compared with the original polarized light, the circular polarization direction and propagation direction of the zero-order beam do not change, while the circular polarization direction of the first-order beam is opposite and the propagation direction changes. The polarization state of the first-order beam is right-handed circular polarization, and the polarization state of the zero-order beam is still left-handed circular polarization. The zero-order beam and the first-order beam pass through a quarter-wave plate 4, and the zero-order beam and the first-order beam are converted into beams with linear polarization directions perpendicular to each other. After the zero-order beam passes through the quarter-wave plate 4, the polarization state of the zero-order beam is vertically polarized, and the linear polarizer 5 filters out the converted zero-order beam, and the converted first-order beam passes through the linear polarizer 5 completely.

[0038] Take a sub-pixel with an incident wavelength of 500nm and a deflection angle θ of 30° as an example, using the grating formula: Where λ is the wavelength of the incident light, Λ x is the lateral period of the grating.

[0039] It can be calculated that the required grating transverse period is 1000nm. At this time, the energy of the zero-order beam is calculated to be 91% through the strict coupled wave theory, and the energy of the first-order beam (the deflected beam) accounts for 9%, and the corresponding theoretical contrast is about 11. If a liquid crystal polarization grating 2 with a refractive index difference of 0.178, a thickness of 1.97um, a transverse period of 1000nm, and a longitudinal period of 249nm is used, the energy of the first-order beam is calculated to account for 99.96% through the strict coupled wave theory, and the zero-order beam is basically completely eliminated and is no longer the main factor affecting the contrast.

[0040] The present invention discloses a light field display screen based on a liquid crystal polarization grating, wherein the traditional grating in the structure is replaced by a liquid crystal polarization grating 2, and the liquid crystal polarization grating 2 is used to deflect the light beam of each sub-pixel, thereby improving the contrast of the existing light field display diffraction element. The light field display screen can filter out the zero-order light beam without affecting the energy of the first-order light beam, thereby achieving the purpose of improving the contrast of the light field display screen.

[0041] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which are equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of them belong to the protection scope of the present invention.

Claims

1. A light field display screen based on a liquid crystal polarization grating, comprising a phase source, characterized in that: The light field display screen based on the liquid crystal polarization grating also includes a circular polarizer, a liquid crystal polarization grating, a quarter wave plate and a linear polarizer. The phase source, the circular polarizer, the liquid crystal polarization grating, the quarter wave plate and the linear polarizer are arranged in sequence. The phase source emits vertically polarized linear polarized light. After the linear polarized light passes through the circular polarizer, the polarization state is converted into circular polarization. After the circular polarized light passes through the liquid crystal polarization grating, it is converted into a first-order light beam and a part of the unconverted zero-order light beam. After the zero-order light beam passes through the quarter wave plate, the polarization state becomes linear polarization and is filtered by the linear polarizer. After the first-order light beam passes through the quarter wave plate, the polarization state of the first-order light beam is perpendicular to the zero-order light beam. The first-order light beam passes through the linear polarizer.

2. The light field display based on liquid crystal polarization grating according to claim 1, characterized in that: After receiving the circularly polarized light, the liquid crystal polarization grating deflects each sub-pixel of the circularly polarized light in different directions, and the liquid crystal director rotates in a plane perpendicular to the liquid crystal director.

3. The light field display screen based on liquid crystal polarization grating according to claim 2, characterized in that: The distribution formula of the liquid crystal director direction at each position is as follows: In the formula, Λ x is the lateral period of the liquid crystal polarization grating, Λ z is the longitudinal period of the liquid crystal polarization grating, x and z are the coordinates of the liquid crystal director in a three-dimensional rectangular coordinate system established with a plane perpendicular to the liquid crystal director as the bottom surface, and θ and α are the deflection angles of the light beam.

4. The light field display based on liquid crystal polarization grating according to claim 3, characterized in that: θ=sin -1 (kλ / Λ x ), where k is the diffraction order and λ is the wavelength of the incident light.

5. The light field display screen based on liquid crystal polarization grating according to claim 1, characterized in that: The polarization state of the linearly polarized light is converted into left-handed circular polarization after passing through the circular polarizer.

6. The light field display screen based on liquid crystal polarization grating according to claim 5, characterized in that: The first-order light beam converted by the liquid crystal polarization grating is right-handed circularly polarized.

7. The light field display screen based on liquid crystal polarization grating according to claim 5, characterized in that: The polarization state of the zero-order light beam converted by the liquid crystal polarization grating is left-handed circular polarization.

8. The light field display screen based on liquid crystal polarization grating according to claim 1, characterized in that: When the wavelength of the incident light emitted by the phase source is 500 nm and the deflection angle θ is 30°, the lateral period of the liquid crystal polarization grating is 1000 nm.

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