A liquid crystal holographic display capable of simultaneously realizing amplitude and phase modulation

Abstract

The present invention relates to a liquid crystal holographic display screen capable of realizing amplitude and phase modulation at the same time, and belongs to the field of electronic devices. The display screen comprises Cell1 and Cell2; Cell1 comprises: pixel electrode 1, common electrode 1, liquid crystal molecule 1 and control electrode 1; Cell2 comprises: pixel electrode 2, common electrode 2, liquid crystal molecule 2 and control electrode 2; Cell1 and Cell2 are adjacent; they are arranged in sequence as common electrode 1, pixel electrode 1, liquid crystal molecule 1, control electrode 1, common electrode 2, pixel electrode 2, liquid crystal molecule 2 and control electrode 2; liquid crystal molecule 1 is parallel or perpendicular to pixel electrode 1; liquid crystal molecule 1 and liquid crystal molecule 2 are perpendicular to each other. The pixel electrode controls the in-plane rotation of the liquid crystal molecule to modulate the phase of the incident light, and the control electrode controls the vertical rotation of the liquid crystal molecule to modulate the intensity of the incident light. When the two are matched, dual modulation of phase and intensity can be realized.

Description

Technical Field

[0001] The invention belongs to the field of electronic devices and relates to a liquid crystal holographic display screen capable of realizing amplitude and phase modulation simultaneously. Background Art

[0002] Liquid crystal, as an electro-optical material for phase-type spatial light modulators, has the advantages of low modulation voltage and high efficiency. It is widely used in holographic displays, and the most common working mode is Electrically Controlled Birefringence (ECB). However, in order to achieve a phase modulation capability of 2π, the thickness of the liquid crystal in the traditional structure must reach at least a complete wave plate. The thicker liquid crystal layer limits the increase in modulation speed and also makes it impossible to further reduce the size of the phase modulation pixel unit, limiting the viewing angle of the holographic image. At the same time, this structure can only perform phase modulation and cannot modulate the amplitude.

[0003] The invention discloses a double-box fringe field conversion liquid crystal holographic display with a three-layer electrode structure, belonging to the field of optical system and device design.

[0004] Holographic display uses a spatial light modulator (SLM) to generate the light wavefront required for display. According to different principles, existing SLMs can be divided into two types: one is to modulate the amplitude of light. The typical device is a digital micromirror (DMD). This type of SLM used for holographic display will lose a lot of light energy and is not efficient. The other is to modulate the phase of light, such as LCOS, which uses the electro-optical effect to change the phase of the incident light. This method has high energy utilization.

[0005] In traditional phase modulation liquid crystal devices, such as LCOS, the working mode of liquid crystal molecules is usually as follows: under the action of the electric field, the liquid crystal orientation is continuously deflected from parallel to the device surface to perpendicular to the device surface, so that the effective refractive index felt by the incident line polarization gradually decreases. When the liquid crystal is parallel to the device surface, its effective refractive index is ne, and when the liquid crystal is perpendicular to the device surface, its refractive index is no. Therefore, the phase modulation range of the device is Where k0 is the wave vector of the incident light in vacuum, and d is the thickness of the liquid crystal. Since holographic display usually requires a phase modulation capability of 2π, the thickness of the liquid crystal needs to satisfy:

[0006] k0·(ne-n0)·d≥2π

[0007] That is, the thickness of the liquid crystal is at least that of a complete wave plate.

[0008] Traditional liquid crystal phase holography requires a thicker liquid crystal layer, which is not only not conducive to improving the modulation speed, but also makes it impossible to further reduce the size of the phase modulation pixel unit, limiting the viewing angle of the displayed holographic image. At the same time, this structure can only perform phase modulation and cannot modulate the amplitude.

[0009] Geometric Phase, also known as PB phase, is a phase delay caused by the change of polarization state when light propagates in an anisotropic medium. The modulation size of GP is independent of the wavelength of the incident light and the thickness of the medium, and is determined by the optical axis of the wave plate. When a beam of incident light (left-handed circularly polarized light or right-handed circularly polarized light, represented by |L> and |R>, respectively) is incident on an internally rotating liquid crystal orientation device (the liquid crystal thickness is d, and the angle between the molecular orientation and the x-axis is α), the outgoing light will contain both |L> and |R> components. Assuming that the incident light is completely left-handed circularly polarized light, the complex amplitudes of the outgoing light |L> and |R> are β L and β R ,Right now:

[0010] |E out >=β L |L>+β R |R> (1)

[0011] Using the Jones matrix, we can calculate that after passing through the liquid crystal:

[0012]

[0013]

[0014] In formulas (2) and (3), Φ e =n e ·d and Φ o =n o ·d, it can be seen from equation (3) that when left-handed circularly polarized light is incident on the liquid crystal wave plate, the outgoing right-handed light has a phase delay term of 2α, which is the PB phase. It can be seen that the magnitude of the PB phase can be modulated by rotating the optical axis direction of the liquid crystal wave plate, and the modulation amount is independent of the wavelength of the incident light. The thickness of the liquid crystal determines the amplitude of the |L> and |R> components in the outgoing light. When Φ e -Φ o =π, the emitted light has only right-hand circular polarization component, and the liquid crystal of this thickness is equivalent to a half-wave plate, so the thickness is reduced by half compared with the traditional refractive index modulation method. e -Φ o When π=π, all of them are converted into left-handed light, and the obtained PB phase delay is -2α.

[0015] When the positive liquid crystal is driven by voltage, the liquid crystal director rotates in the direction parallel to the electric field line. As the voltage increases, the liquid crystal director is eventually parallel to the electric field line. The maximum rotation range of the liquid crystal director does not exceed 90°, so the phase modulation range of a liquid crystal box will not exceed 180° at most. In order to achieve 360° phase modulation and intensity modulation, a double-cell edge field conversion liquid crystal structure with a three-layer electrode structure is designed. Left-handed circularly polarized light passes through two liquid crystal boxes in sequence (each liquid crystal box is equivalent to a half-wave plate). After passing through the first liquid crystal box, all left-handed circularly polarized light is converted into right-handed circularly polarized light, and the generated GP is 2α1; then it passes through the second liquid crystal box and all becomes left-handed polarized light, and the generated GP is -2α2. After passing through the two liquid crystal boxes, the total GP size is: ψ = 2α1-2α2. When the first liquid crystal box only controls the in-plane rotation of the liquid crystal molecules, the second liquid crystal box controls both the horizontal rotation of the liquid crystal molecules and the vertical rotation of the liquid crystal molecules, which can realize the dual control of the amplitude and phase of the liquid crystal device. Summary of the invention

[0016] In view of this, an object of the present invention is to provide a liquid crystal holographic display screen that can simultaneously realize amplitude and phase modulation.

[0017] In order to achieve the above object, the present invention provides the following technical solutions:

[0018] A liquid crystal holographic display screen capable of simultaneously realizing amplitude and phase modulation, comprising Cell 1 and Cell 2;

[0019] Cell1 includes: a pixel electrode 1, a common electrode 1, a liquid crystal molecule 1 and a control electrode 1;

[0020] Cell2 includes: a second pixel electrode, a second common electrode, a second liquid crystal molecule and a second control electrode;

[0021] Cell1 and Cell2 are adjacent;

[0022] The electrodes are arranged in sequence as common electrode 1, pixel electrode 1, liquid crystal molecule 1, control electrode 1, common electrode 2, pixel electrode 2, liquid crystal molecule 2 and control electrode 2;

[0023] Liquid crystal molecules are parallel or perpendicular to pixel electrodes;

[0024] The first liquid crystal molecule and the second liquid crystal molecule are perpendicular to each other.

[0025] Optionally, when the pixel electrode of Cell1 is driven, Cell2 is in its original state, the liquid crystal molecules of Cell1 rotate 90° in the plane, and the liquid crystal molecules of Cell2 remain in their original state. When a beam of left-handed circularly polarized light enters the system, after passing through Cell1, the left-handed circularly polarized light becomes right-handed circularly polarized light due to the rotation of 90° of the liquid crystal molecules, and the phase changes by 180°. When passing through Cell2, the right-handed circularly polarized light becomes left-handed circularly polarized light, and the phase does not change because the liquid crystal molecules do not rotate.

[0026] When Cell1 is in the original state, and the pixel electrode of Cell2 is in the driving state, the liquid crystal molecules of Cell1 remain in the original state, and the liquid crystal molecules of Cell2 rotate 90°. When a beam of left-handed circularly polarized light enters the system, it changes to right-handed circularly polarized light after passing through Cell1, and the liquid crystal molecules do not change, and the phase does not change. When passing through Cell2, the right-handed circularly polarized light changes to left-handed circularly polarized light. Cell2 is pressurized and driven, and the liquid crystal molecules rotate 90°. The phase of the outgoing left-handed circularly polarized light changes to -180°, and the phase changes from -180° to 180°.

[0027] The same result is obtained when the incident light is right-handed circularly polarized.

[0028] Optionally, when the Cell1 pixel electrode is driven and the Cell2 control electrode is driven, the Cell1 liquid crystal molecules rotate 90° in the plane, the optical axis of the Cell2 liquid crystal molecules remains unchanged, and the effective birefringence decreases;

[0029] When a beam of left-handed circularly polarized light enters the system, it changes to right-handed circularly polarized light after passing through Cell1, and the phase changes by 180°. When passing through Cell2, the liquid crystal molecules do not rotate in the plane, and the right-handed circularly polarized light changes to left-handed circularly polarized light, and the phase does not change. The liquid crystal molecules rotate up and down, the effective birefringence of the liquid crystal molecules decreases, and the output light intensity is modulated;

[0030] When the control electrode of Cell1 is driven, the pixel electrode of Cell2 is in the driving state, the liquid crystal molecules of Cell1 rotate up and down, the optical axis does not change, and the liquid crystal molecules of Cell2 rotate 90°. When a beam of left-handed circularly polarized light enters the system, it changes to right-handed circularly polarized light after passing through Cell1, the optical axis of the liquid crystal molecules does not change, the phase does not change, the effective birefringence of the liquid crystal decreases, and the light intensity decreases. When passing through Cell2, the right-handed circularly polarized light changes to left-handed circularly polarized light. Cell2 is pressurized and driven, the liquid crystal molecules rotate 90°, and the phase of the outgoing left-handed circularly polarized light changes to -180°.

[0031] The same result is obtained when the incident light is right-handed circularly polarized.

[0032] The beneficial effects of the present invention are:

[0033] The present invention proposes a liquid crystal display device structure with adjustable phase and amplitude based on PB phase, and adopts a double-box fringe field conversion liquid crystal display mode with a three-layer electrode structure, including Cell1 and Cell2, wherein each Cell comprises: a pixel electrode, a common electrode, a liquid crystal molecule, and a control electrode; a double-box setting is adopted, and the double boxes are arranged in parallel, the pixel electrode controls the in-plane rotation of the liquid crystal molecules to modulate the phase of the incident light, and the control electrode controls the vertical rotation of the liquid crystal molecules to modulate the intensity of the incident light. When the two are matched, dual modulation of the phase and intensity can be achieved.

[0034] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0036] Figure 1 Schematic diagram of phase control; (a) is a schematic diagram of the phase not changing; (b) is a schematic diagram of the phase changing from -180° to 180°;

[0037] Figure 2 Schematic diagram of phase + amplitude control; (a) is a schematic diagram of the modulation of the outgoing light intensity; (b) is a schematic diagram of the phase change of the outgoing left-handed circularly polarized light to -180°.

[0038] Figure numerals: 1-Cell1, 2-Cell2, 11-pixel electrode one, 21-common electrode one, 31-liquid crystal molecule one, 41-control electrode one, 12-pixel electrode two, 22-common electrode two, 32-liquid crystal molecule two, 42-control electrode two. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0040] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0041] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0042] The structure of the present invention is as follows Figure 1 and Figure 2 As shown, including Cell11 and Cell22;

[0043] Cell 1 includes: a pixel electrode 11, a common electrode 21, a liquid crystal molecule 31 and a control electrode 41;

[0044] Cell2 includes: a second pixel electrode 12, a second common electrode 22, a second liquid crystal molecule 32 and a second control electrode 42;

[0045] Cell1 and Cell2 are adjacent;

[0046] The electrodes are arranged in sequence as common electrode 1, pixel electrode 1, liquid crystal molecule 1, control electrode 1, common electrode 2, pixel electrode 2, liquid crystal molecule 2 and control electrode 2;

[0047] Liquid crystal molecules are parallel or perpendicular to pixel electrodes;

[0048] The first liquid crystal molecule and the second liquid crystal molecule are perpendicular to each other.

[0049] When the pixel electrode of Cell1 is driven, Cell2 is in its original state, the liquid crystal molecules of Cell1 rotate 90° in the plane, and the liquid crystal molecules of Cell2 remain in their original state. When a beam of left-handed circularly polarized light enters the system, after passing through Cell1, the left-handed circularly polarized light becomes right-handed circularly polarized light due to the rotation of 90° of the liquid crystal molecules, and the phase changes by 180°. When passing through Cell2, the right-handed circularly polarized light becomes left-handed circularly polarized light. Since the liquid crystal molecules do not rotate, the phase does not change, as shown in FIG. Figure 1As shown in (a). When Cell1 is in its original state and the pixel electrode of Cell2 is in the driving state, the liquid crystal molecules of Cell1 remain in their original state and the liquid crystal molecules of Cell2 rotate 90°. When a beam of left-handed circularly polarized light enters the system, it changes to right-handed circularly polarized light after passing through Cell1. Since the liquid crystal molecules do not change, the phase does not change. When passing through Cell2, the right-handed circularly polarized light changes to left-handed circularly polarized light. Since Cell2 is driven by pressure, the liquid crystal molecules rotate 90°, so the phase change of the outgoing left-handed circularly polarized light is -180°, as shown in Figure 1 As shown in (b), the entire system can achieve a phase change from -180° to 180°. The same result can be obtained when the incident light is right-handed circularly polarized.

[0050] When the pixel electrode of Cell1 is driven and the control electrode of Cell2 is driven, the liquid crystal molecules of Cell1 rotate 90° in the plane, and the optical axis of the liquid crystal molecules of Cell2 remains unchanged, but the effective birefringence decreases. When a beam of left-handed circularly polarized light enters the system, it changes to right-handed circularly polarized light after passing through Cell1, and the phase changes by 180°. When passing through Cell2, since the liquid crystal molecules do not rotate in the plane, the right-handed circularly polarized light changes to left-handed circularly polarized light, and the phase does not change. However, since the liquid crystal molecules rotate up and down, the effective birefringence of the liquid crystal molecules decreases, and the outgoing light intensity is modulated, such as Figure 2 (a) As shown. When the control electrode of Cell1 is driven, the pixel electrode of Cell2 is in the driving state, the liquid crystal molecules of Cell1 rotate up and down, but the optical axis does not change. The liquid crystal molecules of Cell2 rotate 90°. When a beam of left-handed circularly polarized light enters the system, it changes to right-handed circularly polarized light after passing through Cell1. Since the optical axis of the liquid crystal molecules does not change, the phase does not change. However, due to the decrease in the effective birefringence of the liquid crystal, the light intensity decreases. When passing through Cell2, the right-handed circularly polarized light changes to left-handed circularly polarized light. Since Cell2 is driven by pressure, the liquid crystal molecules rotate 90°, so the phase change of the outgoing left-handed circularly polarized light is -180°, as shown in Figure 2 (b) shows the phase change from -180° to 180° in this scheme, while also achieving intensity control. The same result can be obtained when the incident light is right-handed circularly polarized.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A liquid crystal holographic display screen capable of simultaneously realizing amplitude and phase modulation, characterized in that: Including Cell1 and Cell2; Cell1 includes: a pixel electrode 1, a common electrode 1, a liquid crystal molecule 1 and a control electrode 1; Cell2 includes: a second pixel electrode, a second common electrode, a second liquid crystal molecule and a second control electrode; Cell1 and Cell2 are adjacent; The electrodes are arranged in sequence as common electrode 1, pixel electrode 1, liquid crystal molecule 1, control electrode 1, common electrode 2, pixel electrode 2, liquid crystal molecule 2 and control electrode 2; Cell1 and Cell2 are in the original state, with liquid crystal molecules one parallel or perpendicular to pixel electrode one; The first liquid crystal molecule and the second liquid crystal molecule are perpendicular to each other; When the pixel electrode of Cell1 is driven, Cell2 is in its original state, the liquid crystal molecules of Cell1 rotate 90° in the plane, and the liquid crystal molecules of Cell2 remain in their original state. When a beam of left-handed circularly polarized light enters the system, after passing through Cell1, the left-handed circularly polarized light becomes right-handed circularly polarized light due to the rotation of 90° of the liquid crystal molecules, and the phase changes by 180°. When passing through Cell2, the right-handed circularly polarized light becomes left-handed circularly polarized light, and the phase does not change because the liquid crystal molecules do not rotate. When the incident light is right-handed circularly polarized light, the same result is obtained. When Cell1 is in the original state, and the pixel electrode of Cell2 is in the driving state, the liquid crystal molecules of Cell1 remain in the original state, and the liquid crystal molecules of Cell2 rotate 90°. When a beam of left-handed circularly polarized light enters the system, it changes from left-handed circularly polarized light to right-handed circularly polarized light after passing through Cell1, and the liquid crystal molecules do not change, and the phase does not change. When passing through Cell2, the right-handed circularly polarized light changes to left-handed circularly polarized light. Cell2 is pressurized and driven, and the liquid crystal molecules rotate 90°. The phase of the outgoing left-handed circularly polarized light changes to -180°, and the phase changes from -180° to 180°. When the incident light is right-handed circularly polarized light, the same result is obtained. When the pixel electrode of Cell1 is driven and the control electrode of Cell2 is driven, the liquid crystal molecules of Cell1 rotate 90° in the plane, the optical axis of the liquid crystal molecules of Cell2 remains unchanged, and the effective birefringence decreases; when a beam of left-handed circularly polarized light enters the system, the left-handed circularly polarized light becomes right-handed circularly polarized light after passing through Cell1, and the phase changes by 180°. When passing through Cell2, the liquid crystal molecules do not rotate in the plane, the right-handed circularly polarized light becomes left-handed circularly polarized light, and the phase does not change. The liquid crystal molecules rotate up and down, the effective birefringence of the liquid crystal molecules decreases, and the output light intensity is modulated; when the control electrode of Cell1 is driven and the control electrode of Cell2 is driven, the liquid crystal molecules rotate up and down, the effective birefringence of the liquid crystal molecules decreases, and the output light intensity is modulated. The l2 pixel electrode is in the driving state, the liquid crystal molecules in Cell1 rotate up and down, the optical axis does not change, and the liquid crystal molecules in Cell2 rotate 90°. When a beam of left-handed circularly polarized light enters the system, it becomes right-handed circularly polarized light after passing through Cell1, the optical axis of the liquid crystal molecules does not change, the phase does not change, the effective birefringence of the liquid crystal decreases, and the light intensity decreases. When passing through Cell2, the right-handed circularly polarized light becomes left-handed circularly polarized light. Cell2 is pressurized and driven, the liquid crystal molecules rotate 90°, and the phase change of the outgoing left-handed circularly polarized light is -180°; when the incident light is right-handed circularly polarized light, the same result is obtained.

Images