Holographic display

Abstract

A holographic display is provided. The holographic display comprises: a light guide plate comprising a light incident part and at least one light-emitting part, and having a first surface on which the light incident part and the light-emitting part are disposed, and a second surface positioned opposite to the first surface; a light source assembly disposed adjacent to the light incident part on the first surface; a spatial light modulator disposed adjacent to the light-emitting part on the first surface and including a light modulation pixel in one-to-one correspondence with the at least one light-emitting part; and an optical layer disposed on the second surface.

Description

holographic display

[0001] The present invention relates to a holographic display.

[0002] As the information society develops, demand for display devices capable of displaying images is increasing in various forms. In particular, holographic displays utilize the principle of reproducing an image of an original object by diffracting a reference light onto a holographic pattern, which records the interference pattern created by interfering the object light reflected from the original object with a reference light.

[0003] Meanwhile, as a type of digital holographic display, research is actively being conducted on a holographic display that provides a computer-generated hologram (CGH) as an electrical signal to a spatial light modulator instead of directly exposing an original object to obtain a hologram pattern, and the spatial light modulator forms a hologram pattern according to the input CGH signal and diffracts a reference light to create a 3D image.

[0004] The problem to be solved by the present invention is to provide a thin and integrated holographic display.

[0005] Another problem that the present invention seeks to solve is to provide a holographic display with improved optical efficiency.

[0006] The tasks of the present invention are not limited to the tasks mentioned above, and other technical tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0007] According to one embodiment of the present invention for solving the above problem, a holographic display includes a light guide plate including a light-input portion and at least one light-output portion, a first surface on which the light-input portion and the light-output portion are arranged, and a second surface positioned opposite the first surface, a light source assembly disposed adjacent to the light-input portion on the first surface, a spatial light modulator disposed adjacent to the light-output portion on the first surface and including a light modulation pixel corresponding one-to-one to the at least one light-output portion, and an optical layer disposed on the second surface.

[0008] The light modulation pixel includes a first light modulation pixel and a second light modulation pixel, the light output portion includes a first light output portion overlapping the first light modulation pixel and a second light output portion overlapping the second light modulation pixel, the first light output portion and the second light output portion each include a diffraction grating pattern, and the diffraction grating pattern of the first light output portion and the diffraction grating pattern of the second light output portion may differ in at least one of a grating width, a pitch, a grating height, a shape, and a duty cycle.

[0009] The first light and the second light generated from the light source assembly are each incident on the light-incident portion, and the incident angle of the first light may be different from the incident angle of the second light.

[0010] The light output efficiency of the first light output unit for the first light may be greater than the light output efficiency of the first light output unit for the second light, and the light output efficiency of the second light output unit for the second light may be greater than the light output efficiency of the second light output unit for the first light.

[0011] The light guide plate includes a first unit pixel and a second unit pixel, each of which includes the first light-emitting portion and the second light-emitting portion, and the first light-emitting portion of the first unit pixel is arranged closer to the light-input portion than the first light-emitting portion of the second unit pixel, and the diffraction grating pattern of the first light-emitting portion of the first unit pixel and the diffraction grating pattern of the first light-emitting portion of the second unit pixel may differ in at least one of a grating width, a pitch, a grating height, a shape, and a duty cycle.

[0012] The above spatial light modulator may include a liquid crystal element layer and a polarizing layer positioned between the liquid crystal element layer and the light guide plate.

[0013] The light source assembly may include a light source that generates coherent light, a polarizing film positioned between the light source and the light guide plate, and an optical lens positioned between the polarizing film and the light guide plate.

[0014] The above polarizing film is a linear polarizing film, and the polarizing axis of the polarizing film and the polarizing axis of the polarizing layer can extend in the same direction.

[0015] The above optical lens may include a collimation lens.

[0016] The above light guide plate includes a core layer and a clad layer surrounding the core layer, and the refractive index of the core layer may be greater than the refractive index of the clad layer.

[0017] The difference between the refractive index of the core layer and the refractive index of the clad layer may be 0.4 or more and less than 1.5.

[0018] The refractive index of the above core layer may be 1.5 or more.

[0019] According to another embodiment for solving the above problem, a holographic display includes a substrate, a circuit layer disposed on the substrate, a liquid crystal element layer disposed on the circuit layer, a polarizing layer disposed on the liquid crystal element layer, and a light guide plate disposed on the polarizing layer, the light guide plate including a waveguide and at least one light-emitting portion disposed between the waveguide and the polarizing layer.

[0020] The at least one light-emitting portion includes a first light-emitting portion and a second light-emitting portion, each including a diffraction grating pattern, and the diffraction grating pattern of the first light-emitting portion and the diffraction grating pattern of the second light-emitting portion may differ in at least one of a grating width, a pitch, a grating height, a shape, and a duty cycle.

[0021] The liquid crystal element layer includes a first pixel electrode overlapping the first light-emitting portion, a second pixel electrode overlapping the second light-emitting portion, a liquid crystal layer disposed on the first pixel electrode and the second pixel electrode, and a common electrode disposed on the liquid crystal layer, and a thickness of the liquid crystal layer on the first pixel electrode may be greater than a thickness of the liquid crystal layer on the second pixel electrode.

[0022] The circuit layer includes a capping layer disposed below the liquid crystal element layer, and the capping layer includes a first portion overlapping the first pixel electrode and a second portion overlapping the second pixel electrode, and the thickness of the first portion may be smaller than the thickness of the second portion.

[0023] The liquid crystal element layer further includes a color filter layer disposed between the liquid crystal element layer and the waveguide, the color filter layer including a first color filter overlapping the first pixel electrode and a second color filter overlapping the second pixel electrode, and the wavelength of light passing through the first color filter may be different from the wavelength of light passing through the second color filter.

[0024] The light reflectivity of the first pixel electrode and the second pixel electrode may be higher than the light reflectivity of the common electrode, and the light transmittance of the common electrode may be higher than the light transmittance of the first pixel electrode and the second pixel electrode.

[0025] The angle formed by the alignment direction of the liquid crystal molecules included in the liquid crystal layer and the extension direction of the polarization axis of the polarizing layer may be 45 degrees.

[0026] The above liquid crystal layer can delay the phase of light passing through the liquid crystal layer by 1 / 4 wavelength.

[0027] According to one embodiment of the present invention, a holographic display can be made thin and integrated.

[0028] According to a holographic display according to one embodiment of the present invention, light efficiency can be improved.

[0029] The effects according to the embodiments are not limited to those exemplified above, and more diverse effects are included in this specification.

[0030] FIG. 1 is a perspective view illustrating a holographic display according to one embodiment.

[0031] FIG. 2 is an exploded perspective view showing a holographic display according to one embodiment.

[0032] FIG. 3 is a cross-sectional view showing a holographic display according to one embodiment.

[0033] FIG. 4 is a perspective view showing a light guide plate of a holographic display according to one embodiment.

[0034] Figure 5 is an enlarged view of area A of Figure 4.

[0035] Figure 6 is an enlarged view of area B of Figure 4.

[0036] FIG. 7 is a cross-sectional view showing a first unit pixel and a second unit pixel of a light guide plate of a holographic display according to one embodiment.

[0037] Fig. 8 is a cross-sectional view showing a coupler according to one embodiment.

[0038] Fig. 9 is a cross-sectional view showing a coupler according to another embodiment.

[0039] Fig. 10 is a cross-sectional view showing a coupler according to another embodiment.

[0040] Fig. 11 is a cross-sectional view showing a coupler according to another embodiment.

[0041] Fig. 12 is a cross-sectional view showing a coupler according to another embodiment.

[0042] Fig. 13 is a cross-sectional view showing a display panel according to one embodiment.

[0043] Fig. 14 is a plan view showing a spatial light modulator according to one embodiment.

[0044] FIG. 15 and FIG. 16 are cross-sectional views showing a light modulation method of a spatial light modulator according to one embodiment.

[0045] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined solely by the scope of the claims.

[0046] When elements or layers are referred to as being "on" another element or layer, this includes both cases where the other element or layer is directly above the other element or layer or where there is another layer or material intervening therebetween. Similarly, references to "below," "left," and "right" include both cases where the other element or layer is directly adjacent to the other element or where there is another layer or material intervening therebetween. Like reference numerals throughout the specification refer to like elements.

[0047] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, it should be understood that a "first" component referred to below may also be a "second" component within the technical scope of the present invention.

[0048] The features of each of the various embodiments of the present invention can be partially or wholly combined or combined with each other, and various technical connections and operations are possible, and each embodiment can be implemented independently of each other or implemented together in a related relationship.

[0049] Specific embodiments are described below with reference to the attached drawings.

[0050] FIG. 1 is a perspective view illustrating a holographic display according to one embodiment.

[0051] Referring to FIG. 1, a holographic display (10) according to one embodiment can reproduce an image of an original object by diffracting a reference light onto a holographic pattern that records an interference pattern obtained by interfering the object light reflected from the original object with the reference light. For example, the holographic display (10) can generate and reproduce a holographic image (HI) of a three-dimensional shape.

[0052] In some embodiments, the holographic display (10) can generate a holographic image (HI) using information about a digitized object via a computer instead of an actual original object. For example, a computer-generated hologram (CGH) generated by a holography generation unit (500) (see FIG. 2) is provided as an electrical signal to a spatial light modulator (300) (see FIG. 2), and the spatial light modulator (300) (see FIG. 2) can generate a holographic image (HI) by diffracting a reference light to form a holographic pattern.

[0053] The holographic image (HI) generated by the holographic display (10) according to the present embodiment is formed three-dimensionally in a three-dimensional space using interference of light, so that the user (PS) can view the holographic image (HI) with the naked eye without wearing separate glasses or a head mounted display (HMD).

[0054] FIG. 2 is an exploded perspective view showing a holographic display according to one embodiment. FIG. 3 is a cross-sectional view showing a holographic display according to one embodiment.

[0055] Referring to FIGS. 2 and 3, a holographic display (10) according to one embodiment may include a display panel (DP). The display panel (DP) may include a light source assembly (100), a light guide plate (200), a spatial light modulator (300), an optical layer (400), and a holography generation unit (500).

[0056] The light source assembly (100) may be positioned adjacent to one end of the light guide plate (200). The light source assembly (100) may be positioned adjacent to the light-incident portion (210) of the light guide plate (200), which will be described later. The light source assembly (100) may be positioned on the other surface of the light guide plate (200) (e.g., the lower surface in the drawing).

[0057] The light source assembly (100) can emit light, including a light source. The light source assembly (100) can emit light toward the light-input portion (210) of the light guide plate (200) described below. For example, the light source assembly (100) can emit light in a third direction (DR3).

[0058] In the illustrated drawing, the third direction (DR3) may refer to the thickness direction of the holographic display (10). The third direction (DR3) may be a vertical direction. The first direction (DR1) and the second direction (DR2) intersect with respect to the third direction (DR3), and may be, for example, a horizontal direction orthogonal to the third direction (DR3). The first direction (DR1) and the second direction (DR2) intersect with each other as a horizontal direction, and for example, the first direction (DR1) and the second direction (DR2) may be orthogonal to each other. Unless otherwise defined, in the present specification, the direction indicated by the arrows of the first to third directions (DR1, DR2, DR3) may be referred to as one side, and the opposite direction may be referred to as the other side.

[0059] The light source assembly (100) may include a light source (110), a polarizing film (120), and an optical lens (130).

[0060] The light source (110) can emit light. In some embodiments, the light source (110) can emit coherent light. The light source (110) can emit a coherent beam of light. For example, the light source (110) can be a laser diode or a light-emitting diode.

[0061] A polarizing film (120) may be placed on a light source (110). The polarizing film (120) may be placed between the light source (110) and a light guide plate (200). The polarizing film (120) may be a linear polarizing plate. The polarizing film (120) may linearly polarize unpolarized light. In one embodiment, the polarizing film (120) may be a transmissive polarizing plate, but is not limited thereto and may also be a reflective polarizing plate or a semi-transmissive polarizing plate.

[0062] An optical lens (130) may be placed on a polarizing film (120). The optical lens (130) may be placed between the polarizing film (120) and the light guide plate (200). The optical lens (130) may expand or reduce the range of incident light. The optical lens (130) may convert the incident light into a plane wave. For example, the optical lens (130) may be a collimation lens.

[0063] The first light (LS1) emitted from the light source (110) can be converted into linearly polarized second light (LS2) by passing through the polarizing film (120). The linearly polarized second light (LS2) can be expanded to fit the size of the light-incident portion (210) of the light guide plate (200) by passing through the optical lens (130) and converted into third light (LS3) which is a plane wave. The lights included in the third light (LS3) can be incident parallel to the light-incident portion (210) of the light guide plate (200).

[0064] The light guide plate (200) may be placed on the light source assembly (100). The light guide plate (200) may have a planar or plate-like shape extending in a direction perpendicular to the thickness direction of the holographic display (10). The light guide plate (200) may extend in a horizontal direction perpendicular to a third direction (DR3), for example, in the first direction (DR1) and the second direction (DR2). The thickness of the light guide plate (200), for example, the length in the third direction (DR3), may be smaller than the horizontal length of the light guide plate (200), for example, the length in the first direction (DR1) and the second direction (DR2).

[0065] The light guide plate (200) may include a plurality of light source pixels (SP) that are arranged to be spaced apart from each other in a horizontal direction (e.g., a first direction (DR1) and a second direction (DR2)). The light source pixels (SP) of the light guide plate (200) may be arranged to correspond one-to-one with light modulation pixels (MP) of a spatial light modulator (300) to be described later. For example, the light source pixels (SP) may overlap the light modulation pixels (MP) in a third direction (DR3). The plurality of light source pixels (SP) may each emit light in a direction opposite to the third direction (DR3) through the light exit portion (230). Light emitted from the light source pixels (SP) may be incident on the light modulation pixels (MP).

[0066] The light guide plate (200) may include a light inlet (210), a waveguide (220), and a light outlet (230).

[0067] The waveguide (220) may extend in one direction. For example, the waveguide (220) may extend in a first direction (DR1). The waveguide (220) may be connected to the light source assembly (100). The waveguide (220) may be a path through which light generated in the light source assembly (100) travels. For example, light incident from the light source assembly (100) into the waveguide (220) may travel within the waveguide (220) through repeated reflections (e.g., total internal reflection) with minimal energy loss. In one embodiment, the waveguide (220) may be, but is not limited to, an optical fiber including a core and a clad.

[0068] The light-input portion (210) may be disposed on the other surface (e.g., the bottom surface in the drawing) of the waveguide (220). The light-input portion (210) may be disposed adjacent to one end of the waveguide (220). The light-input portion (210) may be disposed adjacent to the light source assembly (100). The light-input portion (210) may be disposed between the waveguide (220) and the light source assembly (100).

[0069] The light receiving portion (210) can move at least a portion of the light generated from the light source assembly (100) to the waveguide (220). In some embodiments, the light receiving portion (210) can include a diffraction optical element (DOE), such as a diffraction grating pattern. The light receiving portion (210) can use diffraction of light to move the light generated from the light source assembly (100) to the waveguide (220).

[0070] The light-emitting portion (230) may be disposed on the other surface (e.g., the bottom surface in the drawing) of the waveguide (220). The light-emitting portion (230) may be disposed on one side of the light-input portion (210). The light-emitting portion (230) may be disposed adjacent to the spatial light modulator (300). The light-emitting portion (230) may be disposed between the waveguide (220) and the spatial light modulator (300).

[0071] The light-emitting unit (230) may be configured in multiple units. The light-emitting unit (230) may be arranged in a light source pixel (SP). For example, at least one light-emitting unit (230) may be arranged in a light source pixel (SP). In some embodiments, multiple light-emitting units (230) may be arranged in a one-to-one correspondence with multiple light source pixels (SP).

[0072] The light exit unit (230) can move at least a portion of the light located within the waveguide (220) to the spatial light modulator (300). In some embodiments, the light exit unit (230) can include a diffraction optical element (DOE) such as a diffraction grating pattern. The light exit unit (230) can use diffraction of light to move the light located within the waveguide (220) to the spatial light modulator (300).

[0073] Third light (LS3) incident on the light guide plate (200) can be diffracted by the light-input portion (210) to generate fourth light (LS4). Some of the fourth light (LS4) can be totally reflected and travel within the waveguide (220). Other parts of the fourth light (LS4) can be diffracted by the light-output portion (230) to generate fifth light (LS5). The fifth light (LS5) can be incident on the spatial light modulator (300).

[0074] The spatial light modulator (300) may be disposed on the other side (e.g., the lower side in the drawing) of the light guide plate (200). For example, the spatial light modulator (300) may be disposed on the other side of the light guide plate (200) in the third direction (DR3). The other side of the light guide plate (200) on which the spatial light modulator (300) is disposed may be the opposite side facing the user (PS). The spatial light modulator (300) may be positioned on the opposite side of the user (PS) with the light guide plate (200) interposed therebetween.

[0075] The spatial light modulator (300) may have a planar or plate-like shape extending in a direction perpendicular to the thickness direction of the holographic display (10). For example, the spatial light modulator (300) may extend in a horizontal direction perpendicular to a third direction (DR3), for example, in the first direction (DR1) and the second direction (DR2). The thickness of the spatial light modulator (300), for example, the length in the third direction (DR3), may be smaller than the horizontal length of the spatial light modulator (300), for example, the length in the first direction (DR1) and the second direction (DR2).

[0076] The holographic display (10) according to the present embodiment can be easily made thinner by attaching a spatial light modulator (300) in a planar or plate-shaped shape to a light guide plate (200) in a planar or plate-shaped shape.

[0077] The spatial light modulator (300) may include a plurality of light modulation pixels (MP) that are arranged to be spaced apart from each other in the horizontal direction. The plurality of light modulation pixels (MP) may each reflect light emitted from a plurality of light source pixels (SP). The light emitted from the plurality of light source pixels (SP) may be reflected by the plurality of light modulation pixels (MP) and provided to the user (PS). The user (PS) may recognize a holographic image (HI) through the light reflected by the spatial light modulator (300).

[0078] The plurality of light modulation pixels (MP) of the spatial light modulator (300) can individually control the phase or amplitude of light emitted from the plurality of light source pixels (SP) of the light guide plate (200). For example, the spatial light modulator (300) can individually control the phase or amplitude of light emitted from the plurality of light source pixels (SP) based on digital hologram pattern information provided from the holography generation unit (500), thereby generating a holographic image (HI).

[0079] The spatial light modulator (300) may be a reflective spatial light modulator (300). For example, the spatial light modulator (300) may include a MO-SLM (Magneto Optical Spatial Light Modulation), a GST phase transition (Ge x Sb y Te z Phase change material) SLM, DMD (Digital Micro-mirror Device) SLM, LCoS (Liquid Crystal on Silicon) SLM, EPD (Electronic Paper Display) SLM, etc. can be used. Hereinafter, the spatial light modulator (300) is described as an example of a liquid crystal-based reflective spatial light modulator (300), but is not limited thereto.

[0080] The optical layer (400) may be disposed on one surface (e.g., the upper surface in the drawing) of the light guide plate (200). For example, the optical layer (400) may be disposed on one side of the light guide plate (200) in the third direction (DR3). The surface of the light guide plate (200) on which the optical layer (400) is disposed may be a surface facing the user (PS). The optical layer (400) may be positioned on the opposite side of the spatial light modulator (300) with the light guide plate (200) interposed therebetween.

[0081] The optical layer (400) can adjust the size and shape of the image, such as enlarging or reducing the image of the holographic image (HI), by controlling the light reflected from the spatial light modulator (300). For example, the optical layer (400) can include various lenses, such as a convex lens, a concave lens, a cylindrical lens, a compound lens, a Fresnel lens, an anamorphic lens, and a meniscus lens. However, the present invention is not limited thereto, and the optical layer (400) can also include other members, such as a mirror.

[0082] The holographic generation unit (500) can generate a computer-generated hologram (CGH). For example, a computer-generated hologram is a holographic pattern and can include information about the amplitude and phase of light for generating a holographic image (HI).

[0083] The holography generation unit (500) can generate a hologram pattern by reflecting information about the amplitude and phase of the light emitted from each of the plurality of light source pixels (SP) of the light guide plate (200). The holography generation unit (500) can provide a hologram pattern in which information about the amplitude and phase of the light emitted from each of the plurality of light source pixels (SP) of the light guide plate (200) is reflected to the spatial light modulator (300). The spatial light modulator (300) can individually adjust the phase of the light according to the amplitude and phase of the light reflected in the hologram pattern.

[0084] The fifth light (LS5) can be incident on a plurality of light modulation pixels (MP) of the spatial light modulator (300). The fifth light (LS5) can be phase- and / or amplitude-modulated in the plurality of light modulation pixels (MP) and reflected toward the optical layer (400) to be converted into a sixth light (LS6). The modulated and reflected sixth light (LS6) can be incident on the optical layer (400). The sixth light (LS6) incident on the optical layer (400) can be converted into a seventh light (LS7) by adjusting the size and shape of the image. The seventh light (LS7) can be perceived as a holographic image (HI) by the user (PS).

[0085] The holographic display (10) according to the present embodiment utilizes light generated from a single light source assembly (100), so that the phase difference of light incident on each light modulation pixel (MP) of the spatial light modulator (300) is constant, thereby facilitating light modulation. This will be described later with reference to FIG. 4, etc.

[0086] In addition, the holographic display (10) according to the present embodiment can increase light efficiency even when light modulation using liquid crystals is performed by using a reflective spatial light modulator (300). This will be described later with reference to FIG. 13, etc.

[0087] Below, the light guide plate (200) and the process of light movement in the light guide plate (200) are described.

[0088] Fig. 4 is a perspective view showing a light guide plate of a holographic display according to one embodiment. Fig. 5 is an enlarged view of area A of Fig. 4. Fig. 6 is an enlarged view of area B of Fig. 4. Fig. 7 is a cross-sectional view showing a first unit pixel and a second unit pixel of a light guide plate of a holographic display according to one embodiment.

[0089] In addition to FIG. 3, referring to FIGS. 4 to 7, the light guide plate (200) may include a unit pixel (UP). The unit pixel (UP) is the minimum unit that constitutes an image and may be the minimum unit for displaying a single color. For example, the unit pixel (UP) may be the minimum unit that displays a single color by combining at least one color.

[0090] A unit pixel (UP) may include a plurality of light source pixels (SP). For example, the unit pixel (UP) may include a first light source pixel (SP1), a second light source pixel (SP2), and a third light source pixel (SP3).

[0091] In some embodiments, the first light source pixel (SP1) can emit light of a first color or red light through the light emitting portion (230), the second light source pixel (SP2) can emit light of a second color or green light through the light emitting portion (230), and the third light source pixel (SP3) can emit light of a third color or blue light through the light emitting portion (230).

[0092] Red light may have a peak wavelength in the range of about 610 nm to about 650 nm, green light may have a peak wavelength in the range of about 510 nm to about 550 nm, and blue light may have a peak wavelength in the range of about 440 nm to about 480 nm. Here, the peak wavelength means the wavelength at which the intensity of light is maximum.

[0093] However, the present invention is not limited thereto, and light other than light having peak wavelengths of red light, green light, and blue light (e.g., light having a range other than the above wavelength range) may also be emitted from the first light source pixel SP1, the second light source pixel SP2, and the third light source pixel SP3 through the light emission unit (230). In this case, the amount of light emitted from light having peak wavelengths of red light, green light, and blue light may be higher than the amount of light emitted from light outside the above range. Light having peak wavelengths of red light, green light, and blue light may be blocked and absorbed in a color filter layer (CFL) described below.

[0094] The light guide plate (200) may include a light inlet (210), a waveguide (220), and a light outlet (230).

[0095] The waveguide (220) may include a core layer (221), a first clad layer (222), and a second clad layer (223).

[0096] The core layer (221) may extend in a first direction (DR1). The core layer (221) may be a passage through which light may travel. The first clad layer (222) and the second clad layer (223) may be disposed on one side and the other side of the core layer (221). For example, the first clad layer (222) may be disposed on one side of the core layer (221) in the third direction (DR3), and the second clad layer (223) may be disposed on the other side of the core layer (221) in the third direction (DR3).

[0097] The first clad layer (222) and the second clad layer (223) can maintain an optical path so that light traveling inside the core layer (221) does not leak out. For example, light can be reflected (e.g., totally reflected) at the interface between the first clad layer (222) and the core layer (221) and at the interface between the second clad layer (223) and the core layer (221) and travel in one direction (e.g., in the opposite direction to the first direction (DR1)).

[0098] In some embodiments, although not shown in the drawings, the first clad layer (222) and the second clad layer (223) may constitute a single clad layer. The single clad layer may be arranged to surround the core layer (221). For example, when the core layer (221) is a cylindrical tube, the single clad layer may be a donut-shaped tube surrounding the core layer (221).

[0099] The refractive index of the core layer (221) may be greater than the refractive indices of the first clad layer (222) and the second clad layer (223). For example, the difference between the refractive index of the core layer (221) and the refractive indices of the first clad layer (222) and the second clad layer (223) may be approximately 0.4 or more and less than 1.5. In one embodiment, the refractive index of the core layer (221) may be approximately 1.5 or more.

[0100] In this specification, the refractive index means the absolute refractive index measured using the D line (wavelength λ is approximately 589 nm: yellow) of sodium (or sodium) at room temperature and relative humidity (temperature 20±15℃, humidity 65±20%). For example, in this specification, the refractive index may be the absolute refractive index measured based on the wavelength of 589 nm according to the Cauchy Film Model using a refractive index measuring instrument (e.g., Ellipsometer (Ellipsometer M-2000, JA Woollam)) under 25℃ and a relative humidity of 65%.

[0101] The light-input portion (210) and the light-output portion (230) may be disposed on the other surface (e.g., the lower surface) of the core layer (221). The light-input portion (210) and the light-output portion (230) may be covered by the first clad layer (222).

[0102] The light-input unit (210) and the light-output unit (230) may each include a coupler. For example, the light-input unit (210) and the light-output unit (230) may include a diffraction grating pattern as a coupler. As illustrated in FIGS. 5 and 6 , light incident on the light-input unit (210) and the light-output unit (230) may travel between two transmission media by the coupling effect of the diffraction grating pattern. Specifically, light incident on the light-input unit (210) from the light source assembly (100) may be diffracted by the diffraction grating pattern and travel to the waveguide (220), and light incident on the light-output unit (230) from the waveguide (220) may be diffracted by the diffraction grating pattern and travel to the spatial light modulator (300).

[0103] The angle at which light incident on the light incident portion (210) of the holographic display (10) according to the present embodiment is incident on the core layer (221) may differ depending on the wavelength. For example, as illustrated in FIG. 5, a first incident light (ICL1) of red light may be incident on the core layer (221) at a first angle (θ1), a second incident light (ICL2) of green light may be incident on the core layer (221) at a second angle (θ2), and a third incident light (ICL3) of blue light may be incident on the core layer (221) at a third angle (θ3). The first angle (θ1), the second angle (θ2), and the third angle (θ3) may be different from each other. The first angle (θ1), the second angle (θ2), and the third angle (θ3) represent angles between the vertical direction (the third direction (DR3)) and the propagation directions of the first incident light (ICL1), the second incident light (ICL2), and the third incident light (ICL3), respectively.

[0104] In the drawing, the first angle (θ1) is shown as being smaller than the second angle (θ2) and the second angle (θ2) is shown as being smaller than the third angle (θ3), but this is not limited thereto. For example, the third angle (θ3) may be smaller than the second angle (θ2) and the second angle (θ2) may be smaller than the first angle (θ1). Alternatively, the second angle (θ2) may be smaller than the first angle (θ1) and the first angle (θ1) may be smaller than the third angle (θ3). The sizes of the first angle (θ1), the second angle (θ2), and the third angle (θ3) may vary depending on the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern of the light-incident portion (210). The grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern will be described later with reference to FIG. 8, etc.

[0105] While moving inside the core layer (221), the angle at which light is reflected at the interface between the core layer (221) and the clad layers (222, 223) may be the same as the angle at which light is incident on the core layer (221). For example, at the interface between the core layer (221) and the clad layers (222, 223), the first incident light (ICL1) of red light may be reflected at a first angle (θ1), the second incident light (ICL2) of green light may be reflected at a second angle (θ2), and the third incident light (ICL3) of blue light may be reflected at a third angle (θ3).

[0106] Meanwhile, the light-emitting unit (230) may include a first light-emitting unit (231) arranged in a first light source pixel (SP1), a second light-emitting unit (232) arranged in a second light source pixel (SP2), and a third light-emitting unit (233) arranged in a third light source pixel (SP3).

[0107] In some embodiments, at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating patterns of the first light-emitting portion (231), the second light-emitting portion (232), and the third light-emitting portion (233) within the same unit pixel (UP) may be different from each other.

[0108] For example, as illustrated in FIG. 6, the grating height (231_H) of the diffraction grating pattern of the first light-emitting portion (231), the grating height (232_H) of the diffraction grating pattern of the second light-emitting portion (232), and the grating height (233_H) of the diffraction grating pattern of the third light-emitting portion (233) may be different from each other. In the drawing, the grating height (231_H) of the diffraction grating pattern of the first light-emitting portion (231) is illustrated as being greater than the grating height (232_H) of the diffraction grating pattern of the second light-emitting portion (232), and the grating height (232_H) of the diffraction grating pattern of the second light-emitting portion (232) is illustrated as being greater than the grating height (233_H) of the diffraction grating pattern of the third light-emitting portion (233), but is not limited thereto. The relationship between the grating height (231_H) of the diffraction grating pattern of the first light-emitting portion (231), the grating height (232_H) of the diffraction grating pattern of the second light-emitting portion (232), and the grating height (233_H) of the diffraction grating pattern of the third light-emitting portion (233) can be modified in various ways.

[0109] In the drawing, the grating width (231_W) of the diffraction grating pattern of the first light-emitting portion (231), the grating width (232_W) of the diffraction grating pattern of the second light-emitting portion (232), and the grating width (233_W) of the diffraction grating pattern of the third light-emitting portion (233) are shown to be the same, and the pitch (231_P) of the diffraction grating pattern of the first light-emitting portion (231), the pitch (232_P) of the diffraction grating pattern of the second light-emitting portion (232), and the pitch (233_P) of the diffraction grating pattern of the third light-emitting portion (233) are shown to be the same, but are not limited thereto. The relationship between the size of the grating width (231_W) of the diffraction grating pattern of the first light-emitting portion (231), the grating width (232_W) of the diffraction grating pattern of the second light-emitting portion (232), and the grating width (233_W) of the diffraction grating pattern of the third light-emitting portion (233) and the relationship between the size of the pitch (231_P) of the diffraction grating pattern of the first light-emitting portion (231), the pitch (232_P) of the diffraction grating pattern of the second light-emitting portion (232), and the pitch (233_P) of the diffraction grating pattern of the third light-emitting portion (233) can be modified in various ways.

[0110] Various embodiments of the grating width, pitch, grating height, shape and duty cycle of the diffraction grating pattern included in the light inlet (210) and light outlet (230) will be described later with reference to FIGS. 8 to 12.

[0111] In the holographic display (10) according to the present embodiment, at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating patterns of the first light-emitting portion (231), the second light-emitting portion (232), and the third light-emitting portion (233) is different from each other, so that the light-emitting efficiency of the first light-emitting portion (231), the second light-emitting portion (232), and the third light-emitting portion (233) may be different depending on the incident angle of light incident on the light-emitting portion (230).

[0112] Specifically, if the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern are different, the light emission efficiency of the diffraction grating pattern may vary depending on the incident angle of light incident on the diffraction grating pattern.

[0113] For example, as illustrated in FIG. 6, the first exit light (EXL1) incident on the exit portion (230) at a first angle (θ1) may have the highest exit efficiency at the first exit portion (231), the second exit light (EXL2) incident on the exit portion (230) at a second angle (θ2) may have the highest exit efficiency at the second exit portion (232), and the third exit light (EXL3) incident on the exit portion (230) at a third angle (θ3) may have the highest exit efficiency at the third exit portion (233).

[0114] Accordingly, the first emission light (EXL1) of mostly red light can be emitted from the first emission unit (231), the second emission light (EXL2) of mostly green light can be emitted from the second emission unit (232), and the third emission light (EXL3) of mostly blue light can be emitted from the third emission unit (233).

[0115] That is, even if the second exit light (EXL2) or the third exit light (EXL3) is incident on the first exit portion (231), since it is incident at an angle other than the first angle (θ1), the emission efficiency of the second exit light (EXL2) and the third exit light (EXL3) from the first exit portion (231) may be significantly lower than the emission efficiency of the first exit light (EXL1).

[0116] In this way, the first light-emitting portion (231) located in the first light source pixel (SP1) can have maximum light-emitting efficiency for the first light-emitting portion (EXL1) of red light, the second light-emitting portion (232) located in the second light source pixel (SP2) can have maximum light-emitting efficiency for the second light-emitting portion (EXL2) of green light, and the third light-emitting portion (233) located in the third light source pixel (SP3) can have maximum light-emitting efficiency for the third light-emitting portion (EXL3) of blue light.

[0117] Accordingly, by increasing the light emission efficiency of the light that can pass through each of the first color filter (CFR) (see FIG. 13), the second color filter (CFG) (see FIG. 13), and the third color filter (CFB) (see FIG. 13) of the spatial light modulator (300) described later, the overall light emission efficiency of the holographic display (10) can be improved.

[0118] Meanwhile, the holographic display (10) according to the present embodiment can control the energy intensity of light emitted from each unit pixel (UP) by controlling the grating width, pitch, grating height, shape, and duty cycle of the diffraction pattern. Accordingly, the energy intensity of light emitted from each unit pixel (UP) can be controlled to be the same or different from each other.

[0119] Specifically, in some embodiments, at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern of the first light-emitting portion (231) included in different unit pixels (UP) may be different from each other.

[0120] For example, the grating width of the diffraction grating pattern of the first light-emitting portion (231) included in the first unit pixel (UP1) may be different from the grating width of the diffraction grating pattern of the first light-emitting portion (231) included in the second unit pixel (UP2). Alternatively, the pitch of the diffraction grating pattern of the first light-emitting portion (231) included in the first unit pixel (UP1) may be different from the pitch of the diffraction grating pattern of the first light-emitting portion (231) included in the second unit pixel (UP2). Alternatively, the grating height of the diffraction grating pattern of the first light-emitting portion (231) included in the first unit pixel (UP1) may be different from the grating height of the diffraction grating pattern of the first light-emitting portion (231) included in the second unit pixel (UP2). Alternatively, the shape of the diffraction grating pattern of the first light-emitting portion (231) included in the first unit pixel (UP1) may be different from the shape of the diffraction grating pattern of the first light-emitting portion (231) included in the second unit pixel (UP2).

[0121] Since some of the light that enters the light inlet (210) and moves inside the waveguide (220) escapes through the light outlet (230), the energy intensity of the light may decrease as it moves away from the light inlet (210) (for example, as it moves in the opposite direction to the first direction (DR1) of FIG. 7). Therefore, in the case where it is desired to emit light with the same energy intensity to each light outlet (230), the energy intensity of the emitted light can be maintained the same by making the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern different. Alternatively, in the case where it is desired to emit light with different energy intensities to each light outlet (230), the energy intensity of the emitted light can be controlled differently by adjusting the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern.

[0122] That is, even if it is the same first light-emitting portion (231), the energy intensity of the emitted light can be controlled by making the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern different for each unit pixel (UP).

[0123] Although the first light-emitting portion (231) is described as an example in the present specification and drawings, the same technical idea may be applied to the second light-emitting portion (232) and the third light-emitting portion (233). For example, at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern of the second light-emitting portion (232) included in the first unit pixel (UP1) may be different from at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern of the second light-emitting portion (232) included in the second unit pixel (UP2). Alternatively, at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern of the third light-emitting portion (233) included in the first unit pixel (UP1) may be different from at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern of the third light-emitting portion (233) included in the second unit pixel (UP2).

[0124] Fig. 8 is a cross-sectional view illustrating a coupler according to one embodiment. Fig. 9 is a cross-sectional view illustrating a coupler according to another embodiment. Fig. 10 is a cross-sectional view illustrating a coupler according to another embodiment. Fig. 11 is a cross-sectional view illustrating a coupler according to another embodiment. Fig. 12 is a cross-sectional view illustrating a coupler according to another embodiment.

[0125] In addition to FIGS. 4 to 7, referring to FIGS. 8 to 12, the light inlet (210) and the light outlet (230) may each include any one of the first to fifth couplers (COU_1, COU_2, COU_3, COU_4, COU_5). The first to fifth couplers (COU_1, COU_2, COU_3, COU_4, COU_5) may include a diffraction grating pattern including a convex portion (CO1) and a concave portion (CO2).

[0126] In one embodiment, as illustrated in FIGS. 8 and 9, the grid width, pitch, and grid height of each coupler may be different from each other. The grid width may be defined as the width of the convex portion (CO1), the pitch may be defined as the sum of the widths of adjacent convex portions (CO1) and concave portions (CO2), and the grid height may be defined as the height of the convex portion.

[0127] For example, the grid width (W1) of the first coupler (COU_1) may be larger than the grid width (W2) of the second coupler (COU_2). The pitch (P1) of the first coupler (COU_1) may be larger than the pitch (P2) of the second coupler (COU_2). The grid height (H1) of the first coupler (COU_1) may be larger than the grid height (H2) of the second coupler (COU_2).

[0128] However, this is not limited thereto, and the grid width (W1) of the first coupler (COU_1) may be smaller than the grid width (W2) of the second coupler (COU_2), the pitch (P1) of the first coupler (COU_1) may be smaller than the pitch (P2) of the second coupler (COU_2), and the grid height (H1) of the first coupler (COU_1) may be smaller than the grid height (H2) of the second coupler (COU_2).

[0129] In this way, the light output efficiency at the light output portion (230) may vary depending on the grating width, pitch, and grating height of the diffraction grating pattern.

[0130] In another embodiment, as illustrated in FIGS. 8, 10 and 11, the grid shapes of each coupler may be different from each other.

[0131] For example, the third coupler (COU_3) of FIG. 10 and the fourth coupler (COU_4) of FIG. 11 may each have a different lattice shape from the first coupler (COU_1) of FIG. 8. The lattices of the third coupler (COU_3) may include a first side (CO1a) and a second side (CO1b) each including an inclined plane. The lattices of the fourth coupler (COU_4) may include a first side (CO1a) including an inclined plane and a second side (CO1b) including a vertical plane.

[0132] However, it is not limited to the city on the drawing, and the shape of each coupler can be modified in various ways depending on the diffraction efficiency.

[0133] In this way, the light output efficiency at the light output unit (230) may vary depending on the shape of each coupler.

[0134] In another embodiment, as illustrated in FIGS. 8 and 12, the duty cycles of the respective couplers may be different from each other. The duty cycle may be defined as the ratio of the grid width to the pitch (duty cycle = Width / Pitch).

[0135] For example, the fifth coupler (COU_5) of FIG. 12 may have a different duty cycle than the first coupler (COU_1) of FIG. 8.

[0136] The duty cycle of the first coupler (COU_1) of Fig. 8 may be a ratio of the grid width (W1) of the first coupler (COU_1) to the pitch (P1) of the first coupler (COU_1). The first coupler (COU_1) of Fig. 8 may have a constant duty cycle for each grid.

[0137] On the other hand, the duty cycle of the fifth coupler (COU_5) of FIG. 12 may have two or more different duty cycles.

[0138] For example, the convex portion (CO1) of the fifth coupler (COU_5) may include a first grating (K1), a second grating (K2), and a third grating (K3), and the concave portion (CO2) of the fifth coupler (COU_5) may include a first groove (M1), a second groove (M2), and a third groove (M3). The first grating (K1), the first groove (M1), the second grating (K2), the second groove (M2), the third grating (K3), and the third groove (M3) may be arranged in sequence.

[0139] In one embodiment, the width (W1a) of the first grating (K1) may be greater than the width (W1b) of the second grating (K2), and the width (W1b) of the second grating (K2) may be greater than the width (W1c) of the third grating (K3). The width (D1) of the first groove (M1), the width (D2) of the second groove (M2), and the width (D3) of the third groove (M3) may be equal to each other.

[0140] However, the present invention is not limited thereto, and in other embodiments, the width (D1) of the first groove (M1), the width (D2) of the second groove (M2), and the width (D3) of the third groove (M3) may be different from each other, and the width (W1a) of the first grid (K1), the width (W1b) of the second grid (K2), and the width (W1c) of the third grid (K3) may be the same. In yet other embodiments, the width (D1) of the first groove (M1), the width (D2) of the second groove (M2), and the width (D3) of the third groove (M3) may be different from each other, and the width (W1a) of the first grid (K1), the width (W1b) of the second grid (K2), and the width (W1c) of the third grid (K3) may be different from each other. For convenience of explanation, in the following, as shown in the drawing, an example is given in which the width (W1a) of the first grid (K1), the width (W1b) of the second grid (K2), and the width (W1c) of the third grid (K3) are different, and the width (D1) of the first groove (M1), the width (D2) of the second groove (M2), and the width (D3) of the third groove (M3) are the same.

[0141] The first pitch (P1a) may be the sum of the width (W1a) of the first grid (K1) and the width (D1) of the first groove (M1), the second pitch (P1b) may be the sum of the width (W1b) of the second grid (K2) and the width (D2) of the second groove (M2), and the third pitch (P1c) may be the sum of the width (W1c) of the third grid (K3) and the width (D3) of the third groove (M3).

[0142] The first duty cycle of the fifth coupler (COU_5) may be the width (W1a) of the first grating (K1) for the first pitch (P1a) (duty cycle1 = W1a / P1a), the second duty cycle of the fifth coupler (COU_5) may be the width (W1b) of the second grating (K2) for the second pitch (P1b) (duty cycle2 = W1b / P1b), and the third duty cycle of the fifth coupler (COU_5) may be the width (W1c) of the third grating (K3) for the third pitch (P1c) (duty cycle3 = W1c / P1c). The first to third duty cycles of the fifth coupler (COU_5) may be different from each other.

[0143] In this way, the light output efficiency from the light output unit (230) may vary depending on the duty cycle of each coupler.

[0144] Meanwhile, the fifth coupler (COU_5) of FIG. 12 illustrates, as an example, that multiple duty cycles are included within a single coupler, but is not limited thereto. The coupler may also include a single duty cycle, like the first coupler (COU_1) of FIG. 8.

[0145] The holographic display (10) according to the present embodiment can improve the light efficiency of the holographic display (10) by making at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern of the first light-emitting portion (231), the second light-emitting portion (232), and the third light-emitting portion (233) different from each other within the same unit pixel (UP).

[0146] In addition, the holographic display (10) according to the present embodiment can improve the light efficiency of the holographic display (10) by making at least one of the grating width, pitch, grating height, shape, and duty cycle of the diffraction grating pattern of the first light-emitting portion (231) included in different unit pixels (UP) different from each other.

[0147] Fig. 13 is a cross-sectional view showing a display panel according to one embodiment.

[0148] In addition to FIGS. 2 and 3, referring to FIG. 13, the display panel (DP) may include a light source assembly (100), a light guide plate (200), a spatial light modulator (300), an optical layer (400), and a holography generation unit (500).

[0149] A holographic display (10) according to the present embodiment may include a display panel (DP) in which a light source that provides light and a spatial light modulator that modulates the light are integrally formed. For example, a light guide plate (200) and a spatial light modulator (300) included in the display panel (DP) may be formed by being laminated on a substrate (SUB) through a continuous process. That is, the light guide plate (200) and the spatial light modulator (300) may be laminated on the display panel (DP) in an in-cell manner. Accordingly, a thin and integrated holographic display (10) may be provided.

[0150] The light guide plate (200) may include a plurality of light source pixels (SP). For example, the light guide plate (200) may include a first light source pixel (SP1), a second light source pixel (SP2), and a third light source pixel (SP3). The spatial light modulator (300) may include a plurality of light modulation pixels (MP). For example, the spatial light modulator (300) may include a first light modulation pixel (MP1), a second light modulation pixel (MP2), and a third light modulation pixel (MP3).

[0151] The spatial light modulator (300) may include a substrate (SUB), a circuit layer (TFTL), a liquid crystal element layer (LML), a color filter layer (CFL), and a polarizing layer (POL).

[0152] The substrate (SUB) may include a transparent material. For example, the substrate (SUB) may include a transparent insulating material such as glass, quartz, etc. The substrate (SUB) may be a rigid substrate. However, without limitation, the substrate (SUB) may include a plastic such as polyimide, etc., and may have flexible characteristics such as being able to be bent, folded, or rolled.

[0153] The circuit layer (TFTL) may include transistors (ST1, ST2, ST3), capacitor electrodes (CPE1, CPE2, CPE3), a gate insulating film (GI), an interlayer insulating film (ILD), a passivation film (PV), a via film (VIA), and a capping film (CPL).

[0154] The transistors (ST1, ST2, ST3) may include a first transistor (ST1), a second transistor (ST2), and a third transistor (ST3). The first transistor (ST1) may be disposed in a first light modulation pixel (MP1), the second transistor (ST2) may be disposed in a second light modulation pixel (MP2), and the third transistor (ST3) may be disposed in a third light modulation pixel (MP3).

[0155] A first transistor (ST1) may include a first active region (ACT1), a first gate electrode (GE1), a first drain electrode (DE1), and a first source electrode (SE1). The first gate electrode (GE1) may overlap the first active region (ACT1) in a third direction (DR3). The first drain electrode (DE1) and the first source electrode (SE1) may be disposed on one side and the other side of the first active region (ACT1), respectively.

[0156] The second transistor (ST2) may include a second active region (ACT2), a second gate electrode (GE2), a second drain electrode (DE2), and a second source electrode (SE2). The second gate electrode (GE2) may overlap the second active region (ACT2) in a third direction (DR3). The second drain electrode (DE2) and the second source electrode (SE2) may be disposed on one side and the other side of the second active region (ACT2), respectively.

[0157] A third transistor (ST3) may include a third active region (ACT3), a third gate electrode (GE3), a third drain electrode (DE3), and a third source electrode (SE3). The third gate electrode (GE3) may overlap the third active region (ACT3) in a third direction (DR3). The third drain electrode (DE3) and the third source electrode (SE3) may be disposed on one side and the other side of the third active region (ACT3), respectively.

[0158] A gate insulating film (GI) may be disposed on the first active region (ACT1), the second active region (ACT2), and the third active region (ACT3). The gate insulating film (GI) may include an inorganic film, for example, a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, a titanium oxide layer, or an aluminum oxide layer.

[0159] An interlayer dielectric (ILD) may be disposed on the first gate electrode (GE1), the second gate electrode (GE2), and the third gate electrode (GE3). The interlayer dielectric (ILD) may include an inorganic film, for example, a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, a titanium oxide layer, or an aluminum oxide layer.

[0160] A protective film (PV) may be disposed on the first drain electrode (DE1), the first source electrode (SE1), the second drain electrode (DE2), the second source electrode (SE2), the third drain electrode (DE3), and the third source electrode (SE3). The protective film (PV) may include an inorganic film, for example, a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, a titanium oxide layer, or an aluminum oxide layer.

[0161] The capacitor electrodes (CPE1, CPE2, CPE3) may include a first capacitor electrode (CPE1), a second capacitor electrode (CPE2), and a third capacitor electrode (CPE3).

[0162] A first capacitor electrode (CPE1) may be arranged in a first light modulation pixel (MP1) and may overlap with a first transistor (ST1) in a third direction (DR3). A second capacitor electrode (CPE2) may be arranged in a second light modulation pixel (MP2) and may overlap with a second transistor (ST2) in a third direction (DR3). A third capacitor electrode (CPE3) may be arranged in a third light modulation pixel (MP3) and may overlap with a third transistor (ST3) in a third direction (DR3).

[0163] The first capacitor electrode (CPE1) can form a first capacitor together with one electrode (e.g., the first drain electrode (DE1)) of the first transistor (ST1). The second capacitor electrode (CPE2) can form a second capacitor together with one electrode (e.g., the second drain electrode (DE2)) of the second transistor (ST2). The third capacitor electrode (CPE3) can form a third capacitor together with one electrode (e.g., the third drain electrode (DE3)) of the third transistor (ST3).

[0164] A via film (VIA) may be disposed on the first capacitor electrode (CPE1), the second capacitor electrode (CPE2), and the third capacitor electrode (CPE3). The via film (VIA) may include an organic film such as an acrylic resin, an epoxy resin, a phenolic resin, a polyamide resin, or a polyimide resin.

[0165] A capping layer (CPL) may be disposed on a via layer (VIA). In one embodiment, the capping layer (CPL) may include an inorganic layer, such as a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, a titanium oxide layer, or an aluminum oxide layer. In another embodiment, the capping layer (CPL) may include an organic layer, such as an acrylic resin, an epoxy resin, a phenolic resin, a polyamide resin, or a polyimide resin.

[0166] A liquid crystal element layer (LML) may be disposed on a capping film (CPL). The liquid crystal element layer (LML) may include a pixel electrode (PXE), a liquid crystal layer (LCL), and a common electrode (CME).

[0167] The pixel electrode (PXE) may be disposed on the capping film (CPL). The pixel electrode (PXE) may be a reflective electrode having high reflectivity for visible light. In some embodiments, the pixel electrode (PXE) may include a metal material having high reflectivity, such as a stacked structure of aluminum and titanium (Ti / Al / Ti), a stacked structure of aluminum and ITO (ITO / Al / ITO), an APC alloy, and a stacked structure of an APC alloy and ITO (ITO / APC / ITO). The APC alloy is an alloy of silver (Ag), palladium (Pd), and copper (Cu).

[0168] The pixel electrode (PXE) may include a first pixel electrode (PXR), a second pixel electrode (PXG), and a third pixel electrode (PXB).

[0169] The first pixel electrode (PXR) may be disposed in the first light modulation pixel (MP1). The second pixel electrode (PXG) may be disposed in the second light modulation pixel (MP2). The third pixel electrode (PXB) may be disposed in the third light modulation pixel (MP3).

[0170] The first pixel electrode (PXR) may be connected to the first transistor (ST1) through a contact hole. For example, the first pixel electrode (PXR) may be connected to the first source electrode (SE1). The second pixel electrode (PXG) may be connected to the second transistor (ST2) through a contact hole. For example, the second pixel electrode (PXG) may be connected to the second source electrode (SE2). The third pixel electrode (PXB) may be connected to the third transistor (ST3) through a contact hole. For example, the third pixel electrode (PXB) may be connected to the third source electrode (SE3).

[0171] A liquid crystal layer (LCL) may be disposed on a pixel electrode (PXE). The liquid crystal layer (LCL) may include liquid crystal molecules (LC). The liquid crystal molecules (LC) may have dielectric anisotropy.

[0172] A common electrode (CME) may be disposed on the liquid crystal layer (LCL). The common electrode (CME) may be a transparent electrode having high transmittance to visible light. In some embodiments, the common electrode (CME) may include a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZO), etc. The common electrode (CME) may be an integrated electrode disposed across multiple light modulation pixels (MPs) regardless of the distinction between the MPs.

[0173] In some embodiments, the optical reflectivity of the pixel electrode (PXE) may be higher than the optical reflectivity of the common electrode (CME). The optical transmittance of the common electrode (CME) may be higher than the optical transmittance of the pixel electrode (PXE).

[0174] Although not shown in the drawing, the liquid crystal element layer (LML) may further include an alignment film disposed between the pixel electrode (PXE) and the liquid crystal layer (LCL) and between the liquid crystal layer (LCL) and the common electrode (CME).

[0175] In this specification, a structure in which a liquid crystal element layer (LML) is laminated in the order of a pixel electrode (PXE), a liquid crystal layer (LCL), and a common electrode (CME) is described as an example, but is not limited thereto. For example, a structure in which a pixel electrode (PXE), a common electrode (CME), and a liquid crystal layer (LCL) are laminated in the order of a pixel electrode (PXE), a common electrode (CME), and a liquid crystal layer (LCL) may be used, or a structure in which a pixel electrode (PXE) and a common electrode (CME) are arranged on the same layer may be used.

[0176] A color filter layer (CFL) may be disposed on a liquid crystal layer (LML). The color filter layer (CFL) may include a plurality of color filters (CFR, CFG, CFB) corresponding to each of a plurality of light modulation pixels (MP) and a light blocking member (BM) disposed between the plurality of color filters (CFR, CFG, CFB). Each of the color filters (CFR, CFG, CFB) may selectively transmit light of a specific wavelength and block or absorb light of a different wavelength.

[0177] The color filters (CFR, CFG, CFB) may include a first color filter (CFR), a second color filter (CFG), and a third color filter (CFB). The first color filter (CFR) may be disposed in the first light modulation pixel (MP1), the second color filter (CFG) may be disposed in the second light modulation pixel (MP2), and the third color filter (CFB) may be disposed in the third light modulation pixel (MP3).

[0178] The first color filter (CFR) can selectively transmit red light and block or absorb green light and blue light. For example, the first color filter (CFR) can be a red color filter and can include a red colorant. The second color filter (CFG) can selectively transmit green light and block or absorb red light and blue light. For example, the second color filter (CFG) can be a green color filter and can include a green colorant. The third color filter (CFB) can selectively transmit blue light and block or absorb red light and green light. For example, the third color filter (CFB) can be a blue color filter and can include a blue colorant.

[0179] A light-shielding member (BM) may be disposed between color filters (CFR, CFG, CFB). The light-shielding member (BM) may include a light-absorbing material. For example, the light-shielding member (BM) may include an inorganic black pigment, an organic black pigment, or an organic blue pigment. The inorganic black pigment may be a metal oxide such as carbon black or titanium black, the organic black pigment may include at least one of lactam black, perylene black, and aniline black, and the organic blue pigment may be CI pigment blue, but is not limited thereto. The light-shielding member (BM) may improve the color reproducibility of the holographic display (10) by preventing visible light from penetrating between adjacent light modulation pixels (MP) and causing color mixing.

[0180] A polarizing layer (POL) may be disposed on a color filter layer (CFL). The polarizing layer (POL) may linearly polarize unpolarized light. The optical axis of the polarizing layer (POL) may extend in the same direction as the optical axis of the polarizing film (120). For example, if the polarizing film (120) has a vertical polarization axis, the polarizing layer (POL) may have a vertical polarization axis, and if the polarizing film (120) has a horizontal polarization axis, the polarizing layer (POL) may have a horizontal polarization axis. The polarizing layer (POL) may prevent unpolarized light from penetrating into the liquid crystal layer (LCL).

[0181] In the holographic display (10) according to the present embodiment, the capping film (CPL) may include a first portion disposed on a first light modulation pixel (MP1), a second portion disposed on a second light modulation pixel (MP2), and a third portion disposed on a third light modulation pixel (MP3). The first pixel electrode (PXR) may be disposed on the first portion of the capping film (CPL), the second pixel electrode (PXG) may be disposed on the second portion of the capping film (CPL), and the third pixel electrode (PXB) may be disposed on the third portion of the capping film (CPL).

[0182] In some embodiments, the thickness (TH1) of the first portion of the capping film (CPL), the thickness (TH2) of the second portion of the capping film (CPL), and the thickness (TH3) of the third portion of the capping film (CPL) may be different from each other. For example, the thickness (TH1) of the first portion of the capping film (CPL) may be less than the thickness (TH2) of the second portion of the capping film (CPL), and the thickness (TH2) of the second portion of the capping film (CPL) may be less than the thickness (TH3) of the third portion of the capping film (CPL).

[0183] The liquid crystal layer (LCL) may include a first portion disposed in a first light modulation pixel (MP1), a second portion disposed in a second light modulation pixel (MP2), and a third portion disposed in a third light modulation pixel (MP3).

[0184] In some embodiments, the thickness (H_P1) of the first portion of the liquid crystal layer (LCL), the thickness (H_P2) of the second portion of the liquid crystal layer (LCL), and the thickness (H_P3) of the third portion of the liquid crystal layer (LCL) may be different from each other. For example, the thickness (H_P1) of the first portion of the liquid crystal layer (LCL) may be greater than the thickness (H_P2) of the second portion of the liquid crystal layer (LCL), and the thickness (H_P2) of the second portion of the liquid crystal layer (LCL) may be greater than the thickness (H_P3) of the third portion of the liquid crystal layer (LCL).

[0185] In some embodiments, the thickness (H_P1) of the first portion of the liquid crystal layer (LCL) may be approximately 0.25 times the wavelength of light transmitted by the first color filter (CFR). For example, the thickness (H_P1) of the first portion of the liquid crystal layer (LCL) may be approximately 150 nm to 165 nm. The thickness (H_P2) of the second portion of the liquid crystal layer (LCL) may be approximately 0.25 times the wavelength of light transmitted by the second color filter (CFG). For example, the thickness (H_P2) of the second portion of the liquid crystal layer (LCL) may be approximately 125 nm to 140 nm. The thickness (H_P3) of the third portion of the liquid crystal layer (LCL) may be approximately 0.25 times the wavelength of light transmitted by the third color filter (CFB). For example, the thickness (H_P3) of the third portion of the liquid crystal layer (LCL) may be approximately 110 nm to 120 nm.

[0186] The holographic display (10) according to the present embodiment can cause a resonance phenomenon by designing the thickness of the liquid crystal layer (LCL) of each of the first to third optical modulation pixels (MP1, MP2, MP3) to be different. Accordingly, the optical efficiency of the holographic display (10) can be improved.

[0187] Meanwhile, in the case where the spatial light modulator (300) according to the present embodiment is a reflective spatial light modulator (300), the light emitted from the light guide plate (200) passes through the liquid crystal layer (LCL) at least twice, so the thickness of the liquid crystal layer (LCL) can be reduced by half compared to the case where the spatial light modulator (300) is a transmissive type. Accordingly, the thinning of the holographic display (10) can be facilitated.

[0188] The light guide plate (200) may be placed on the spatial light modulator (300). The light guide plate (200) may be formed by being laminated on the spatial light modulator (300) through a continuous process after the formation of the spatial light modulator (300). That is, the light guide plate (200) may be formed integrally with the spatial light modulator (300) in an in-cell manner on the display panel (DP).

[0189] The light guide plate (200) may include a waveguide (220) and a light output portion (230). The waveguide (220) may include a first clad layer (222), a core layer (221), and a second clad layer (223).

[0190] The first clad layer (222) may be disposed on a polarizing layer (POL). The core layer (221) may be disposed on the first clad layer (222). The second clad layer (223) may be disposed on the core layer (221). The light-emitting portion (230) may be disposed between the first clad layer (222) and the core layer (221).

[0191] The light-emitting portion (230) may include a first light-emitting portion (231) disposed in a first light source pixel (SP1), a second light-emitting portion (232) disposed in a second light source pixel (SP2), and a third light-emitting portion (233) disposed in a third light source pixel (SP3). The first light-emitting portion (231) may overlap with the first light modulation pixel (MP1), the second light-emitting portion (232) may overlap with the second light modulation pixel (MP2), and the third light-emitting portion (233) may overlap with the third light modulation pixel (MP3).

[0192] The optical layer (400) may be disposed on the light guide plate (200). In one embodiment, the optical layer (400) may be formed integrally with the spatial light modulator (300) and the light guide plate (200) in an in-cell manner. However, the present invention is not limited thereto, and in another embodiment, the optical layer (400) may be bonded onto the light guide plate (200) through a separate module process.

[0193] Light generated from the light source assembly (100) can be incident on the spatial light modulator (300) through the light guide plate (200). The light incident on the spatial light modulator (300) can be modulated and reflected at the light modulation pixel (MP) and emitted to the outside through the optical layer (400). For example, as illustrated in FIG. 13, the fifth light (LS5) emitted from the light emitting unit (230) can pass through the polarizing layer (POL), the color filter layer (CFL), and the liquid crystal layer (LCL) to reach the pixel electrode (PXE). The fifth light (LS5) can be reflected at the pixel electrode (PXE) and emitted to the outside through the liquid crystal layer (LCL), the color filter layer (CFL), the polarizing layer (POL), and the optical layer (400).

[0194] Fig. 14 is a plan view showing a spatial light modulator according to one embodiment.

[0195] In addition to FIG. 2, referring to FIG. 14, the spatial light modulator (300) may include a display area (DA) and a non-display area (NDA). The display area (DA) may be positioned approximately at the center of the spatial light modulator (300), and the non-display area (NDA) may be positioned to surround the display area (DA).

[0196] The display area (DA) of the spatial light modulator (300) may include a plurality of light modulation pixels (MP), a plurality of light modulation power lines (VL_LM) connected to the plurality of light modulation pixels (MP), a plurality of row-axis light modulation data lines (RL), and a plurality of column-axis light modulation data lines (CL).

[0197] A plurality of optical modulation pixels (MP) may be arranged in a first direction (DR1) and a second direction (DR2). For example, the plurality of optical modulation pixels (MP) may be arranged in a matrix direction. Each of the plurality of optical modulation pixels (MP) may be connected to a plurality of optical modulation power lines (VL_LM), a plurality of row-axis optical modulation data lines (RL), and a plurality of column-axis optical modulation data lines (CL). Each of the plurality of optical modulation pixels (MP) may include at least one transistor, an optical modulation element, and a capacitor. In some embodiments, the capacitor may be omitted.

[0198] The row-axis optical modulation data lines (RL) can extend in a first direction (DR1) and can be spaced apart from each other in a second direction (DR2) intersecting the first direction (DR1). The row-axis optical modulation data lines (RL) can sequentially supply row-axis optical modulation data signals to a plurality of optical modulation pixels (MP).

[0199] The thermal axis optical modulation data lines (CL) can extend in a second direction (DR2) and be spaced apart from each other in a first direction (DR1). The thermal axis optical modulation data lines (CL) can supply thermal axis optical modulation data signals to a plurality of optical modulation pixels (MP).

[0200] The optical modulation power line (VL_LM) can extend in the second direction (DR2) and be spaced apart from each other in the first direction (DR1). The optical modulation power line (VL_LM) can supply a power voltage to a plurality of optical modulation pixels (MP). The power voltage can be at least one of a driving voltage, a high-potential voltage, an initialization voltage, a reference voltage, a bias voltage, and a low-potential voltage.

[0201] The optical modulation timing control unit (310) can receive optical modulation digital data (DATA_LM) and timing signals from the holography generation unit (500). The optical modulation timing control unit (310) can generate a column-axis optical modulation data control signal (CCS) and a row-axis optical modulation data control signal (RCS) based on the timing signals. The optical modulation timing control unit (310) can control the operation timing of the column-axis optical modulation driving unit (320) by supplying the optical modulation digital data (DATA_LM) and the column-axis optical modulation data control signal (CCS) to the column-axis optical modulation driving unit (320). The optical modulation timing control unit (310) can control the operation timing of the row-axis optical modulation driving unit (330) by supplying the optical modulation digital data (DATA_LM) and the row-axis optical modulation data control signal (RCS) to the row-axis optical modulation driving unit (330).

[0202] The column-axis optical modulation driving unit (320) and the row-axis optical modulation driving unit (330) can convert the column-axis optical modulation data control signal (CCS) and the row-axis optical modulation data control signal (RCS) into analog optical modulation data voltages and supply them to the column-axis optical modulation data line (CL) and the row-axis optical modulation data line (RL), respectively.

[0203] The row-axis optical modulation driving unit (330) may be positioned on the left or right side of the non-display area (NDA). The column-axis optical modulation driving unit (320) may be positioned on the upper or lower side of the non-display area (NDA).

[0204] The optical modulation power supply unit (340) can supply power voltage to the spatial light modulator (300), the column-axis optical modulation driving unit (320), and the row-axis optical modulation driving unit (330). The optical modulation power supply unit (340) can generate a driving voltage of the optical modulation element and supply it to a driving voltage line, generate an initialization voltage and supply it to an initialization voltage line, generate a bias voltage and supply it to a bias voltage line, and generate a low-potential voltage and supply it to a low-potential line.

[0205] A plurality of light modulation pixels (MP) of a spatial light modulator (300) according to the present embodiment can be arranged in one-to-one correspondence to a plurality of light source pixels (SP) of a light guide plate (200). Accordingly, the plurality of light modulation pixels (MP) can individually control the phases of the lights emitted from the plurality of light source pixels (SP).

[0206] FIG. 15 and FIG. 16 are cross-sectional views showing a light modulation method of a spatial light modulator according to one embodiment.

[0207] In addition to FIG. 13, referring to FIGS. 15 and 16, the spatial light modulator (300) can control the phase and / or amplitude of light by controlling the direction of liquid crystal molecules (LC) of the liquid crystal layer (LCL). The liquid crystal element layer (LML) of the spatial light modulator (300) can be driven by various types of driving methods such as the twisted nematic (TN) method, the vertical alignment (VA) method, the in plane switching (IPS) method, the polymer dispersed liquid crystal (PDLC) method, and the fringe-field switching (FFS) method. In the present specification and drawings, the VA method is described as an example, but is not limited thereto.

[0208] Figure 15 is a drawing showing an OFF state in which no voltage is applied to the liquid crystal layer (LCL), and Figure 16 is a drawing showing an ON state in which the maximum voltage is applied to the liquid crystal layer (LCL).

[0209] As illustrated in Fig. 15, according to the VA method, in the OFF state where no voltage is applied, liquid crystal molecules (LC) can be aligned in a certain direction, for example, vertically. At this time, the liquid crystal layer (LCL) can play the same role as a vertical polarizing plate that transmits only vertically polarized light.

[0210] Light passing through the polarizing layer (POL) of the spatial light modulator (300) can be linearly polarized (e.g., vertically polarized). The vertically polarized light can pass through a liquid crystal layer (LCL) that transmits only vertically polarized light. Thereafter, the vertically polarized light can be reflected by the pixel electrode (PXE) and pass through the liquid crystal layer (LCL) and the polarizing layer (POL) again. Accordingly, an image can be displayed externally.

[0211] As illustrated in Fig. 16, according to the VA method, in the ON state when the maximum voltage is applied, the liquid crystal molecules (LC) can be arranged in a certain direction, for example, in a state deflected by 45 degrees. At this time, the liquid crystal layer (LCL) can play the same role as a quarter-wave plate (QWP) phase retardation plate that delays the phase of the passing light by 1 / 4 wavelength.

[0212] Light passing through the polarizing layer (POL) of the spatial light modulator (300) can be linearly polarized (e.g., vertically polarized). The vertically polarized light can be converted into circularly polarized light (e.g., left-circularly polarized light) by passing through a liquid crystal layer (LCL) that delays the phase by 1 / 4 wavelength. The circularly polarized light can be reflected from the pixel electrode (PXE) and pass through the liquid crystal layer (LCL) once more. At this time, the circularly polarized light can be converted into linearly polarized light (e.g., horizontally polarized light). The horizontally polarized light can be blocked by the polarizing layer (POL) whose polarization axis is vertical.

[0213] In this way, the spatial light modulator (300) can control the phase and / or amplitude of light by controlling the behavior of liquid crystal molecules (LC). Meanwhile, if the spatial light modulator (300) is a reflective spatial light modulator, the light incident from the light guide plate (200) to the spatial light modulator (300) passes through the liquid crystal layer (LCL) twice, so that the alignment angle of the liquid crystal molecules (LC) can form a 45 degree angle with respect to the polarization axis of the polarizing layer (POL).

[0214] Although embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. A light guide plate including a light-input portion and at least one light-emitting portion, a first surface on which the light-input portion and the light-emitting portion are arranged, and a second surface located on the opposite side of the first surface; A light source assembly disposed adjacent to the light-input portion on the first surface; A spatial light modulator disposed adjacent to the light-emitting portion on the first surface and including a light modulation pixel corresponding one-to-one to the at least one light-emitting portion; and A holographic display comprising an optical layer disposed on the second surface.

2. In paragraph 1, The above optical modulation pixel includes a first optical modulation pixel and a second optical modulation pixel, The light-emitting portion includes a first light-emitting portion overlapping the first light-modulating pixel and a second light-emitting portion overlapping the second light-modulating pixel, The first light-emitting portion and the second light-emitting portion each include a diffraction grating pattern, A holographic display in which the diffraction grating pattern of the first light-emitting portion and the diffraction grating pattern of the second light-emitting portion are different in at least one of a grating width, a pitch, a grating height, a shape, and a duty cycle.

3. In paragraph 2, The first light and the second light generated from the above light source assembly are respectively incident on the light-incident portion, A holographic display in which the angle of incidence of the first light is different from the angle of incidence of the second light.

4. In paragraph 3, The light emission efficiency of the first light-emitting portion for the first light is greater than the light emission efficiency of the first light-emitting portion for the second light, A holographic display in which the light emission efficiency of the second light-emitting portion for the second light is greater than the light emission efficiency of the second light-emitting portion for the first light.

5. In paragraph 2, The light guide plate includes a first unit pixel and a second unit pixel, each of which includes the first light-emitting portion and the second light-emitting portion, The first light-emitting portion of the first unit pixel is positioned closer to the light-input portion than the first light-emitting portion of the second unit pixel, A holographic display in which the diffraction grating pattern of the first light-emitting portion of the first unit pixel and the diffraction grating pattern of the first light-emitting portion of the second unit pixel differ in at least one of a grating width, a pitch, a grating height, a shape, and a duty cycle.

6. In paragraph 1, The above spatial light modulator is, Liquid crystal element layer; and A holographic display including a polarizing layer positioned between the liquid crystal element layer and the light guide plate.

7. In paragraph 6, The above light source assembly, A light source that produces coherent light; a polarizing film positioned between the light source and the light guide plate; and A holographic display comprising an optical lens positioned between the polarizing film and the light guide plate.

8. In paragraph 7, The above polarizing film is a linear polarizing film, A holographic display in which the polarization axis of the polarizing film and the polarization axis of the polarizing layer extend in the same direction.

9. In paragraph 7, The above optical lens is a holographic display including a collimation lens.

10. In paragraph 1, The above light guide plate includes a core layer and a clad layer surrounding the core layer, A holographic display in which the refractive index of the core layer is greater than the refractive index of the clad layer.

11. In paragraph 10, A holographic display in which the difference in refractive index between the core layer and the clad layer is 0.4 or more and less than 1.

5.

12. In paragraph 11, A holographic display having a refractive index of the core layer of 1.5 or more.

13. Substrate; A circuit layer disposed on the above substrate; A liquid crystal element layer disposed on the circuit layer; A polarizing layer disposed on the liquid crystal element layer; and A holographic display comprising a light guide plate disposed on the polarizing layer and including a waveguide and at least one light-emitting portion disposed between the waveguide and the polarizing layer.

14. In paragraph 13, The at least one light-emitting portion includes a first light-emitting portion and a second light-emitting portion, each of which includes a diffraction grating pattern, A holographic display in which the diffraction grating pattern of the first light-emitting portion and the diffraction grating pattern of the second light-emitting portion are different in at least one of a grating width, a pitch, a grating height, a shape, and a duty cycle.

15. In paragraph 14, The above liquid crystal element layer, A first pixel electrode overlapping the first light-emitting portion; A second pixel electrode overlapping the second light-emitting portion; A liquid crystal layer disposed on the first pixel electrode and the second pixel electrode; and including a common electrode disposed on the liquid crystal layer, A holographic display in which the thickness of the liquid crystal layer on the first pixel electrode is greater than the thickness of the liquid crystal layer on the second pixel electrode.

16. In paragraph 15, The circuit layer includes a capping layer disposed below the liquid crystal element layer, The capping layer includes a first portion overlapping the first pixel electrode and a second portion overlapping the second pixel electrode, A holographic display wherein the thickness of the first portion is smaller than the thickness of the second portion.

17. In paragraph 15, Further comprising a color filter layer disposed between the liquid crystal element layer and the waveguide, The color filter layer includes a first color filter overlapping the first pixel electrode and a second color filter overlapping the second pixel electrode, A holographic display in which the wavelength of light passing through the first color filter is different from the wavelength of light passing through the second color filter.

18. In paragraph 15, The light reflectance of the first pixel electrode and the second pixel electrode is higher than the light reflectance of the common electrode, A holographic display wherein the light transmittance of the common electrode is higher than the light transmittances of the first pixel electrode and the second pixel electrode.

19. In paragraph 15, A holographic display in which the angle formed by the alignment direction of the liquid crystal molecules included in the liquid crystal layer and the extension direction of the polarization axis of the polarizing layer is 45 degrees.

20. In paragraph 19, A holographic display in which the liquid crystal layer delays the phase of light passing through the liquid crystal layer by 1 / 4 wavelength.

Images