KR102600440B1 - Hologram display device - Google Patents

Abstract

The present invention relates to a holographic display device with good image quality and improved viewing angle and holographic image size, comprising a light source unit that supplies light, a spatial light modulator that forms an interference pattern to diffract and transmit the light supplied from the light source, and , It is disposed in front of the spatial light modulator and consists of an optical mask that transmits only the diffracted light of a specific order among the diffracted light output from the spatial light modulator.

Description

Hologram display device {HOLOGRAM DISPLAY DEVICE}

The present invention relates to a hologram display device with improved viewing angle and improved image size.

Recently, research on 3D (Three Dimension) images and image playback technology has been actively conducted. 3D video-related media is a new concept of realistic video media that raises the level of visual information to a higher level, and is expected to lead the next generation of video devices. Existing 2D imaging systems provide flat images, but 3D imaging systems can be said to be the ultimate imaging technology from the perspective of showing the actual image information contained in an object to the observer.

Methods for reproducing 3D stereoscopic images are largely divided into binocular parallax (stereoscopic) and complex parallax (autostereoscopic) methods. The binocular parallax method uses the parallax images of the left and right eyes, which has a large stereoscopic effect, and a glasses-type stereoscopic image display device that implements binocular parallax images using glasses has recently been commercialized. The glasses method changes the polarization of the left and right parallax images on a direct-view display device or projector and displays them to create a three-dimensional image using polarized glasses. The polarized glasses method displays the left and right parallax images in a time division method and uses shutter glasses to create a three-dimensional image. It is divided into the shutter glasses method implemented. However, the glasses method has the inconvenience of requiring viewers to wear glasses to view 3D images.

To solve this problem, a glasses-free method that allows viewing 3D images without wearing glasses is being developed. In particular, the volumetric display method, one of the glasses-free methods, can provide continuous parallax and color information, providing the advantage of allowing the user to move the viewpoint relatively freely.

The holographic method, a volumetric display device method, uses the principle of recording and reproducing an interference signal obtained by overlapping light reflected from an object (object light) and a coherence reference light. Using coherent light, an interference pattern formed by the overlap of object light scattered by hitting an object and reference light incident from a different direction is recorded on photographic film. When object light and reference light meet, an interference pattern is formed due to interference, and the amplitude and phase information of the object are recorded together in this interference pattern. By irradiating reference light (the same light as the reference light) to the interference pattern recorded in this way, the interference information recorded in the hologram is restored, creating a three-dimensional feeling. The series of processes that create three-dimensional images using these recording and restoration principles is called a hologram.

However, the following problems occur in the 3D display method using such a hologram.

Generally, a spatial light modulator is deployed in a 3D display device using a hologram. Unlike two-dimensional photos, in a three-dimensional display device, the spatial light modulator stores an interference pattern caused by interference between object light and reference light, and a three-dimensional image can be restored by irradiating the reference light to the spatial light modulator.

Since this holographic display device utilizes the coherent interference characteristics caused by diffraction of light, the size of the diffraction power is determined by the pixel size of the spatial light modulator, and the viewing angle that the viewer can view and the size of the holographic image are determined by the diffraction power. It is decided. In other words, the smaller the pixel size of the spatial light modulator, the greater the diffraction power. The better the diffraction power, the better the viewing angle and the larger the size of the holographic image.

Therefore, in order to obtain a holographic image with a desired viewing angle and size, the pixel size of the spatial light modulator must be finely formed to correspond to the wavelength of visible light. However, since it is impossible to form pixels of such a fine size with current technology, there are limits to improving the viewing angle of the holographic display device and the size of the holographic image.

The purpose of the present invention is to provide a holographic display device that allows users to view holographic images without inconvenience by preventing holographic images from diffracted light of orders other than a specific order from being displayed.

The purpose of the present invention is to provide a holographic display device that can improve the viewing angle of a holographic image and increase the size of the holographic image.

In order to achieve the above object, a holographic display device according to the present invention includes a light source unit that supplies light, a spatial light modulator in which an interference pattern is formed to diffract and transmit the light supplied from the light source, and a front surface of the spatial light modulator. It consists of an optical mask that is disposed in and transmits only the diffracted light of a specific order among the diffracted light output from the spatial tube modulator.

The spatial light modulator consists of a liquid crystal panel including a plurality of pixels, and the optical mask includes a plurality of transmission areas corresponding to the plurality of pixels of the liquid crystal panel. At this time, the area of the transmission area of the optical mask is smaller than the area of the pixel of the corresponding spatial light modulator.

The plurality of transmission areas of the optical mask have different phase values, and in this case, the phase values are in the range of 1-2π. Additionally, transmission areas with different phase values are arranged irregularly on the optical mask.

In the present invention, an optical mask is placed in front of the spatial light modulator, so that diffracted light of other orders cannot form a holographic image due to the irregular phase of the spatial light modulator and is displayed as noise, and only diffracted light of a specific order is transmitted through the spatial light modulator as is. Since a holographic image is formed, it is possible to prevent defects in which multiple holographic images are displayed.

In addition, in the present invention, a holographic image is displayed by transmitting only the diffracted light of an order that is emitted at a certain angle to the vertical direction of the surface of the display device, so that the viewing angle direction can form a certain angle with the vertical direction of the surface of the display device. In particular, it becomes possible to produce a holographic display device whose main viewing direction is at a certain angle to the front.

Moreover, in the present invention, the area of the transmission area of the optical mask is made several times smaller than the area of the pixel of the spatial light modulator, and the diffraction light passes through the transmission area to create a holographic image, thereby improving the viewing angle of the holographic image and improving the image quality. It is possible to increase the size of .

1 is a diagram showing a hologram display device according to the present invention.
Figure 2 is a cross-sectional view of the spatial light modulator of the hologram display device according to the present invention.
Figure 3 is a diagram showing diffracted light when only a spatial light modulator is provided.
FIGS. 4A and 4B are diagrams showing an actual image of an actual object and a holographic image when equipped with only a spatial light modulator, respectively.
Figure 5 is a diagram showing diffracted light when the display device according to the present invention is equipped with a spatial light modulator and an optical mask.
Figure 6 is a diagram showing a hologram image displayed in a hologram display device according to the present invention.
7A and 7B are plan views showing the arrangement of pixels of a spatial light modulator and a transmission area of an optical mask, respectively.
Figure 8 is a diagram showing the implementation of a holographic image using diffraction light of orders other than the 0th order diffraction light.
9A and 9B are diagrams showing recording and reproducing a holographic image, respectively.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. These embodiments only serve to ensure that the disclosure of the present invention is complete and that common knowledge in the technical field to which the present invention pertains is not limited. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims.

The shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining embodiments of the present invention are illustrative, and the present invention is not limited to the matters shown. Like reference numerals refer to like elements throughout the specification. Additionally, in describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. When 'includes', 'has', 'consists of', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise.

When interpreting a component, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship of two parts is described as 'on top', 'on the top', 'on the bottom', 'next to', etc., 'immediately' Alternatively, there may be one or more other parts placed between the two parts, unless 'directly' is used.

In the case of a description of a temporal relationship, for example, if a temporal relationship is described as 'after', 'successfully after', 'after', 'before', etc., 'immediately' or 'directly' Unless used, non-consecutive cases may also be included.

Although first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, the first component mentioned below may also be the second component within the technical spirit of the present invention.

Each feature of the various embodiments of the present invention can be combined or combined with each other, partially or entirely, and various technological interconnections and operations are possible, and each embodiment can be implemented independently of each other or together in a related relationship. It may be possible.

Hereinafter, the present invention will be described in detail with reference to the attached drawings.

Figure 1 is a diagram showing a hologram display device 100 according to the present invention.

As shown in FIG. 1, the hologram display device 100 according to the present invention includes a spatial light modulator 110 on which an interference pattern of an image of a photographed object is displayed, and is disposed on the rear of the spatial light modulator 110. A hologram is generated from a light source unit 120 that supplies light to the spatial light modulator 110, an optical mask 130 disposed in front of the spatial light modulator 110, and a three-dimensional image captured by the imager 160. It consists of a control unit 140 that generates an image signal, and a spatial light modulator (SLM) driver 150 that drives the spatial light modulator 110 according to the holographic image signal generated by the control unit 140.

The light source unit 120 supplies light in the form of parallel light or spherical wave to the spatial light modulator 110. Although not shown in the drawing, the light source unit 120 may include a light source of a specific wavelength and an optical element that guides light toward the spatial light modulator 110 and converts it into parallel light or a spherical wave form. At this time, a plurality of light sources may be provided depending on the color to be displayed. For example, the light source unit 120 may include a plurality of light sources with different wavelengths of red, green, and blue. A laser with good coherence can be used as the light source, but it is not limited to this, and various light sources that can output light of a single wavelength with good coherence can be applied. Additionally, the light output from the light source unit 120 is not limited to parallel wave or spherical wave light, and various types of light may be applied.

The spatial light modulator 110 is driven according to a holographic image signal to emit light supplied from the light source unit 120. The holographic image signal corresponds to the interference pattern of the object, and the interference pattern is implemented through the spatial light modulator 110, and the light supplied from the light source unit 120 is diffracted while passing through the spatial light modulator 110. When projected, it is displayed as a holographic image.

As will be described later, the spatial light modulator 110 may be composed of a liquid crystal panel provided with a liquid crystal layer. Since the phase and amplitude of light transmitted through the liquid crystal panel changes depending on the arrangement of the liquid crystal molecules of the liquid crystal layer, the liquid crystal molecules of each pixel of the liquid crystal panel are arranged according to the holographic image signal so that a plurality of pixels form an interference pattern. The light input from the light source unit 120 is diffracted by the interference pattern of the pixel of the spatial light modulator 110 to display a holographic image.

Meanwhile, the spatial light modulator 110 can be configured in various forms as long as it can diffract the input light by forming an interference pattern. For example, the spatial light modulator 110 may be composed of a DMD (Digital Mirroring Device) and display a holographic image by diffracting and reflecting incident light.

The spatial light modulator driver 150 controls the arrangement of the liquid crystal molecules by switching the liquid crystal molecules of the pixel by applying a holographic image signal to the electrode formed in the liquid crystal panel, that is, the spatial light modulator 110.

The spatial light modulator driver 150 may include a gate driver and a data driver. At this time, the data driver receives holographic image information from the control unit 140 and converts the holographic image information into analog data voltage using a gamma compensation voltage supplied from a gamma voltage generation circuit (not shown). Additionally, the data driver supplies analog data voltage to the data line (not shown) of the liquid crystal panel. The gate driver sequentially supplies a gate signal (or scan signal) synchronized to the data signal to the gate lines of the liquid crystal panel under the control of the control unit 140.

Figure 2 is a diagram showing the spatial light modulator 110 according to the present invention.

As shown in FIG. 2, the spatial light modulator 110 includes a first substrate 111 and a second substrate 112, and first substrates formed on the first substrate 111 and the second substrate 112, respectively. A liquid crystal layer 116 disposed between the electrode 113 and the second electrode 114 and the first substrate 111 and the second substrate 112, and a seal line sealing the liquid crystal layer 116 ( 118).

Although not shown in the drawing, an alignment film may be formed on the first substrate 111 and the second substrate 112 to orient the liquid crystal molecules of the liquid crystal layer 116. In addition, although not shown in the drawing, a plurality of gate lines and data lines are arranged vertically and horizontally on the first substrate 111 to define a plurality of pixels (P). At this time, the gate line is connected to the gate driver of the spatial light modulator driver 150 and the data line is connected to the data driver, so that a data signal and a gate signal are input, respectively.

The first substrate 111 and the second substrate 112 may be made of a transparent glass substrate or a transparent film such as triacetylcellulose (TAC), but are not limited to these specific materials. .

A data signal and a gate signal are input to the first electrode 113 and the second electrode 114, respectively, from the spatial light modulator driver 150, and the voltage difference between the first electrode 113 and the second electrode 114 An electric field is applied to the liquid crystal layer 116.

The first electrode 113 is formed separately on the plurality of pixels P of the first substrate 111, and the second electrode 114 is formed over the entire second substrate 112. That is, the first electrode 113 is formed in a substantially square shape and is arranged in a matrix shape at a set interval d on the first substrate 111, and the second electrode 114 is formed on the second substrate 112. ) is formed integrally throughout.

A data signal is input to each of the plurality of first electrodes 113 and a common signal is applied to the second electrode 114, so that an electric field is formed between the first electrode 113 and the second electrode 114. The arrangement direction of the liquid crystal molecules of the liquid crystal layer 116 changes according to the electric field formed between the first electrode 113 and the second electrode 114, so that the phase and amplitude of light passing through the liquid crystal layer 116 change.

At this time, the data signal is generated according to the holographic image signal and applied to the first electrode 113 of the spatial light modulator 110, so the plurality of pixels P of the spatial light modulator 110 form an interference pattern. A holographic image can be created by diffracting the transmitted light according to an interference pattern.

The first electrode 113 and the second electrode 114 are transparent conductive oxides such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide), but are not limited thereto and are transparent and have good conductivity. Any material can be used.

Referring again to FIG. 1, the optical mask 130 transmits only the diffracted light of a specific order among the diffracted light output through the spatial light modulator 110 as is to create a holographic image, and changes the phase of the diffracted light of other orders. By preventing holographic images from being implemented by outputting, it is possible to prevent defects resulting from the implementation of multiple holographic images. In addition, the optical mask 130 forms a transmission area through which diffracted light is transmitted to a size smaller than the pixel of the spatial light modulator 110, thereby improving the viewing angle and size of the holographic image. This will be described in detail below. Explain.

Figure 3 is a diagram showing diffracted light transmitted through the spatial light modulator 110 in which an interference pattern pattern is formed.

As shown in FIG. 3, when coherent light L1 passes through the spatial light modulator 110, the transmitted light is diffracted by the interference pattern formed on the spatial light modulator 110 and is emitted. At this time, diffraction light L2 of a plurality of orders (0th, 1st, 2nd, 3rd...) is emitted from the spatial light modulator 110, and at this time, the intensity of the 0th order (Oth) diffraction light L2 is the highest. As the size increases and the order increases, the intensity of the diffracted light (1st, 2nd...) decreases. In this way, as multiple orders of diffracted light L2 are emitted from the spatial light modulator 110, a single hologram image corresponding to an actual object does not appear on the front of the spatial light modulator 110, but rather an order (0th, A plurality of holographic images corresponding to the diffracted light (L2) (1st, 2nd, 3rd...) are displayed.

FIGS. 4A and 4B are diagrams showing actual objects, and FIG. 4B is diagrams showing a holographic image reproduced by the spatial light modulator 110.

As shown in Figure 4a, the actual object is "A" and no image other than "A" appears on the screen.

However, as shown in FIG. 4B, when the object is displayed as a holographic image by the spatial light modulator 110, a plurality of holographic images are displayed instead of one. That is, the holographic image displayed by the 0th order (Oth) diffraction light (L2) appears brightest in the center of the screen, and the 1st order (1st) image is displayed around the holographic image corresponding to the 0th order (Oth) diffraction light (L2). The holographic image displayed by the diffracted light (L2) is displayed with a luminance lower than the first order. In addition, although not shown in the drawing, a holographic image displayed by the second (2nd) diffraction light (L2) on the outskirts of the holographic image corresponding to the first (1st) diffraction light (L2) has a luminance lower than that of the second diffraction light (L2). holographic images corresponding to these multiple orders are displayed on the outside (of course, they are not recognized due to low luminance).

When a user views such a holographic image, not only the bright holographic image in the center is recognized, but also relatively dark holographic images around it are recognized, so that the human eye perceives multiple holographic images with the same shape but different luminance, creating a three-dimensional shape. You will not be able to watch.

In addition, the size of each pixel of the spatial light modulator 110 is several times larger than the wavelength of visible light, so the viewing angle of the display device is extremely small, limiting the area in which the viewer can view the holographic image, and the size of the holographic image is also extremely small. Therefore, it becomes impossible to enjoy life-like 3D images.

Figure 5 shows an optical mask 130 provided on the front of the spatial light modulator 110 on which an interference pattern pattern according to the present invention is formed, showing the diffracted light passing through the spatial light modulator 110 and the optical mask 130. It is a drawing.

As shown in FIG. 5, when coherent light L1 passes through the spatial light modulator 110, the transmitted light is diffracted by the interference pattern formed on the spatial light modulator 110 and forms an optical mask. Entered as (130). Diffracted light (L2) of multiple orders (0th, 1st, 2nd, 3rd...) is emitted from the spatial light modulator 110, and at this time, the intensity of the 0th order (0th) diffracted light (L2) is the largest and the order ( As the 1st, 2nd...) goes up, the intensity of the diffracted light (L2) gradually decreases.

The optical mask 130 is composed of a plurality of areas D, and each area D is given a different phase value to change the phase of the transmitted diffracted light L2. At this time, the optical mask 130 changes the 0th order (Oth) diffracted light (L2) to a phase set to include the image information contained in the interference pattern pattern and transmits it, while the higher order (1st, 2nd, and 3rd) diffracted light (L2) is transmitted. ...)'s diffracted light (L2) is transmitted by changing its phase so that the image information included in the interference pattern is removed.

The 0th order (Oth) diffracted light L2 emitted from the spatial light modulator 110 is phase-changed to include image information, passes through the optical mask 130, and a holographic image is displayed on the front surface. In addition, the diffracted light L2 of different orders (1st, 2nd, 3rd...) is transmitted with its phase changed by the optical mask 130, and due to this phase change, the image information contained in the diffracted light L2 is removed, preventing the formation of a holographic image on the front of the optical mask 130.

Figure 6 is a diagram showing a hologram image displayed by the spatial light modulator 110 and the optical mask 130 in the hologram display device according to the present invention.

As shown in FIG. 6, in the present invention, when the object is displayed as a holographic image by the spatial light modulator 110, the 0th order diffracted light (L2) transmits the optical mask 130 with image information. The holographic image "A" appears brightest in the center of the screen, and the diffracted light (L2) of order 0 or higher changes phase as it passes through the optical mask 130 and image information is removed, forming a bright spot at the corresponding position. As a result, the holographic image cannot be formed and is displayed as blurry noise around the holographic image "A".

When comparing the holographic image of FIG. 6 with the actual image of the object in FIG. 4A, the holographic image has lower luminance than the actual image, but is displayed as a three-dimensional image identical to the actual image. Comparing the holographic image of FIG. 6 with the holographic image of FIG. 4b, the holographic image of FIG. 4b is confusing to the viewer because it displays multiple holographic images instead of only one image, whereas in the present invention, only one hologram is displayed. Since the video is displayed, viewers can watch the holographic video without any inconvenience.

Of course, in the holographic display device of the present invention, instead of displaying a plurality of holographic images, blurry noise is displayed around the holographic image, which deteriorates the image quality compared to the actual image, but the image quality is relatively good compared to the case where a plurality of holographic images are displayed. It is possible to provide holographic images.

In addition, in the present invention, by providing the optical mask 130 to transmit the spatial light modulator 110, it is possible to improve the viewing angle of the holographic image and increase the size of the image, which will be described in more detail below.

7A and 7B are plan views showing the spatial light modulator 110 and the optical mask 130 of the hologram display device according to the present invention, respectively.

As shown in FIG. 7A, the spatial light modulator 110 is composed of a liquid crystal panel that changes the amplitude and phase of transmitted light, and the liquid crystal panel includes a plurality of pixels (P) arranged in a matrix shape. Each pixel P is provided with a pixel electrode, a common electrode, and a liquid crystal layer. Additionally, a thin film transistor is formed within the pixel P, allowing each pixel to be driven separately. In other words, an electric field of different strength is formed in each pixel depending on the on-off driving of the thin film transistor and the size of the signal applied to the pixel electrode, and according to this electric field, the arrangement of the liquid crystal molecules in the liquid crystal layer changes to provide amplitude and phase information. An excited interference pattern is formed in the spatial light modulator 110. As light passes through the pixel forming the interference pattern, the light is diffracted and emitted.

As shown in FIG. 7B, the optical mask 130 includes a plurality of transmission areas D arranged in a matrix shape. At this time, the number of transmission areas (D) of the optical mask 130 is the same as the number of pixels (P) of the spatial light modulator 110, and the transmission area (D) of the optical mask 130 is the spatial light modulator ( It is formed at a position corresponding to the pixel (P) of 110). In other words, the transmission area (D) of the optical mask 130 and the pixel (P) of the spatial light modulator 110 have a one-to-one correspondence, so that the diffracted light transmits the pixel (P) of the spatial light modulator 110. This is incident on the transmission area (D) of the corresponding optical mask 130.

The transmission area D of the optical mask 130 changes the phase of the incident light and transmits it. Although not shown in the drawing, each of the plurality of transmission areas D has a different phase value, so the light passing through each of the plurality of transmission areas D has a different phase. At this time, the plurality of transmission areas (D) each have a phase value in the range of 0-2π. The transmission area D may have different values so as not to overlap, or some portions may overlap. However, it is preferable that the phase value of the transmission area D is formed non-periodically.

In addition, the transmission areas (D) with different phase values are arranged randomly, so that light other than a specific order, for example, 0th order (Oth) diffracted light (L2), passes through the transmission area (D). If you do so, image information is lost due to irregular phase values, so a holographic image cannot be formed and is displayed as noise.

Different phase values may be provided to the plurality of transmission areas D by a phase control layer (not shown). At this time, the phase control layer may be formed of dielectric materials such as TiO ₂ , SiO ₂ , SiNx, Al ₂ O ³ , AlN, HfO ₂ , SiC, and MgO as a single or mixed layer, but is limited to these dielectric materials. It doesn't work. Additionally, phase films with different phase values may be disposed in the plurality of transmission areas D to change the phase value of transmitted light.

The area (a1) of the pixel (P) of the spatial light modulator 110 is equal to or larger than the area (a2) of the transmission area (D) of the optical mask 130 (a1 ≥ a2), and the spatial light modulator 110 The pitch of the pixel (P) is equal to or greater than the pitch of the transmission area (D) of the optical mask 130. In addition, regardless of the area of the pixel (P) of the spatial light modulator 110 and the transmission area (D) of the optical mask 130, the pitch of the pixel (P) of the spatial light modulator 110 is the same as that of the optical mask ( It may be greater than or equal to the pitch of the transmission area (D) of 130).

Therefore, since the pixel (P) of the spatial light modulator 110 and the transmission area (D) of the optical mask 130 are formed at corresponding positions, the diffracted light emitted from the pixel (P) of the spatial light modulator 110 (L2) is incident and transmitted through the transmission area (D) of the corresponding optical mask 130.

Since the spatial light modulator 110 is composed of a display panel such as a liquid crystal panel, various metal patterns such as a pixel electrode and a common electrode are formed in each pixel P of the spatial light modulator 110. Since these metal patterns are mainly formed through a photolithography process, it is practically impossible to form the area of the pixel P below a certain size (for example, the wavelength of visible light) due to the nature of the process.

Moreover, since the pixel (P) of the spatial light modulator 110 must be equipped with a driving element such as a thin film transistor for driving the liquid crystal layer, there was a limit to reducing the area of the pixel (P) below a certain size. .

On the other hand, the optical mask 130 does not require a separate photolithography process by simply laminating an organic phase control material or attaching a phase control film to the transmission area (D), so the transmission area (D) can be formed in a small area. It becomes possible. Moreover, since the transmission area D of the optical mask 130 does not require a driving element such as a thin film transistor, the transmission area D can be formed in a smaller area.

According to the present invention, the area (a2) of the transmission area (D) of the optical mask 130 can be formed to be several times smaller than the area (a1) of the pixel (P) of the spatial light modulator 110 (a1 = na2) , where n is an integer). Since the transmission area (D) of the optical mask 130 corresponds one-to-one with the pixel (P) of the spatial light modulator 110, the light emitted from a specific pixel (P) of the spatial light modulator 110 corresponds to the corresponding optical It is transmitted through the transmission area (D) of the mask 130.

Therefore, the 0th order (0th) diffracted light L2, which is emitted from the spatial light modulator 110 and passes through the optical mask 130 to form a holographic image, has the same effect as the diffracted light emitted from the optical mask 130. do. In other words, the same effect can be obtained as when the diffracted light L2 forming the holographic image is emitted from the light transmission area of the optical mask 130. Since the area (a2) of the transmission area (D) of the optical mask 130 is several times smaller than the area (a1) of the pixel (P) of the spatial light modulator 110, a hologram equipped with the optical mask 130 The viewing angle range and size of the holographic image implemented in the display device increase several times or more compared to the viewing angle range and size of the holographic image of the holographic display device not provided with the optical mask 130.

As such, in the present invention, the optical mask 130 is placed in front of the spatial light modulator 110, so that diffracted light of different orders loses image information due to the irregular phase of the spatial light modulator 110, and thus cannot form a holographic image. Since the holographic image is formed by passing through the spatial light modulator 110 so that only the 0th order (0th) diffracted light L2, which is displayed as noise, contains image information, it is possible to prevent defects in which multiple holographic images are displayed.

Meanwhile, in the above description, the optical mask 130 transmits only the 0th order (0th) diffracted light (L2) with image information included, and transmits diffracted light of other orders with the image information removed, thereby transmitting the 0th order (0th) diffracted light (L2). Although a holographic image is implemented only by diffracted light (L2), the holographic image of the present invention is not only implemented by 0th order (0th) diffracted light (L2), but can also be implemented by diffracted light of other orders.

FIG. 8 is a diagram showing that a holographic image is implemented using diffracted light of orders other than the 0th order diffracted light (L2).

As shown in FIG. 8, when coherent coherent light L1 is input to the spatial light modulator 110 in which an interference pattern is formed, diffracted light L2 is transmitted to the spatial light modulator ( 110). The output diffracted light L2 is transmitted through the optical mask 130.

The diffraction light (L2) output from the spatial light modulator 110 is 0th order (0th) diffraction light (L2), 1st order (1st) diffraction light (L2), 2nd order (2nd) diffraction light (L2), and more. It includes diffracted light (L2), and the optical mask 130 is a first order (1st) diffracted light (L2) on one side among multiple orders of diffracted light (L2) output from the spatial light modulator (110). Only the phase is changed to include image information and is transmitted, and the diffracted light (L2) of another order is output with its phase changed so that the information is removed. Accordingly, only the first order (1st) diffracted light (L2) on one side that has passed through the optical mask 130 implements a holographic image, and diffracted light of other orders does not implement a holographic image and is displayed as noise.

As such, in the present invention, the optical mask 130 makes it possible to implement holographic images not only from the 0th order (0th) diffracted light (L2) but also from diffracted light of other orders, and even when implementing holographic images of diffracted light of other orders, the surrounding Because other holographic shapes are not displayed, viewers can enjoy the holographic image they want without any inconvenience.

In addition, while the 0th order diffraction light (L2) is emitted in a direction perpendicular to the surface of the display device, the diffraction light of other orders is emitted at a certain angle with the vertical direction of the surface of the display device. The viewing angle direction of the holographic image forms a certain angle with the vertical direction of the surface of the display device. Therefore, the method of implementing a hologram using diffracted light of different orders can be successfully applied to a display device whose main viewing direction is at a certain angle to the front.

FIGS. 9A and 9B are diagrams showing acquiring and reproducing a hologram image in a hologram display device according to the present invention, respectively.

As shown in FIG. 9A, a photographing device for photographing an object may include a recording optical mask 130a and a CCD camera 180.

Although not shown in the drawing, the recording optical mask 130a includes a plurality of transmission areas, and a phase control layer or phase film with different phase values is formed in each transmission area. At this time, a plurality of transmission areas with different phase values are irregularly arranged throughout the entire area of the recording optical mask 130a, and the phase values are in the range of 1-2π.

When the light reflected from an object (object light L3) and the reference light L4 input from an additive light source such as a laser are input to the recording optical mask 130a, the object light L3 and the reference light L4 are input to the recording optical mask 130a. An interference pattern is formed by overlapping, and the interference pattern is recorded on the CCD camera 180 after passing through the optical mask 130a for recording.

At this time, since the recording optical mask 130a is composed of a plurality of transmission areas with different phase values, the interference pattern pattern transmitted through the recording optical mask 130a is the original interference pattern pattern (i.e., recording The interference pattern formed by overlapping the object light L3 and the reference light L4 on the front surface of the optical mask 130a becomes an interference pattern pattern containing information on the transmission area of the recording optical mask 130a.

In the present invention, the recording optical mask 130a is formed so that only a specific interference order (for example, 0th order or 1st order) is recorded in the interference pattern pattern transmitted through the recording optical mask 130a. That is, the transmission area of the recording optical mask 130a is arranged so that only a specific interference order is recorded in the interference pattern pattern. The arrangement of the transmission area of the recording optical mask 130a can be adjusted by various methods. For example, an interference pattern may be recorded by switching a plurality of recording optical masks 130a with different arrangements of light transmitting areas until an interference pattern containing only a specific order is recorded.

Additionally, the interference pattern may be generated by a computer generated hologram. The computer-generated hologram is created by computer calculating an interference pattern formed by overlapping object light and reference light. In particular, in the present invention, the computer-generated hologram can calculate an interference pattern based on not only the interference information formed by simply overlapping object light and reference light, but also the arrangement information of the transmission area of the recording optical mask 130a.

That is, it is possible to calculate the interference pattern pattern based on the phase distribution of the transmission area (D) of the optical mask by considering the high-order component of the spatial light modulator 110 and the intensity of each order.

As shown in FIG. 9B, the photographed or recorded interference pattern is implemented through the spatial light modulator 110. That is, each pixel of the spatial light modulator 110 composed of a liquid crystal panel is driven so that the pixels of the spatial light modulator 110 have the same optical characteristics as the interference pattern pattern, and the reference light identical to the reference light is transmitted to the spatial light modulator 110. ), and the light is diffracted by the interference pattern, thereby making it possible to display a holographic image. At this time, only the interference pattern of a specific interference order is recorded in the photographed or recorded interference pattern.

The optical mask 130 for reproduction transmits the diffracted light output from the spatial light modulator 110, transmits only the diffracted light diffracted from a specific interference order recorded in the interference pattern, and diffracted light diffracted from the remaining interference orders. Changes the phase and transmits it so that only one holographic image is displayed.

The reproduction optical mask 130 has the same transmission area arrangement as the recording optical mask 130a provided in the imaging device. In addition, the gap (ℓ1) between the object in the photographing device and the recording optical mask 130a is the same as the gap (ℓ1') between the reproduction optical mask 130 and the holographic image in the display device (ℓ1 = ℓ1' ), the gap (ℓ2) between the recording optical mask 130a and the CCD camera 180 in the imaging device is the gap (ℓ2') between the spatial light modulator 110 and the reproduction optical mask 130 of the display device. It is the same as (ℓ2=ℓ2').

In addition, when the interference pattern pattern is calculated by the computer-generated hologram, the reproduction optical mask 130 includes transmission area arrangement information of the recording optical mask, spacing (ℓ1) information between the object and the recording optical mask 130a, An interference pattern pattern is calculated by including information on the distance (ℓ2) between the recording optical mask 130a and the CCD camera 180.

Therefore, when the light diffracted by the interference pattern pattern photographed through the recording optical mask 130a or the interference pattern pattern recorded by a computer-generated hologram passes through the reproduction optical mask 130, the photographed light with a specific interference order is The object is reproduced as a holographic image as is, and diffracted light of other orders is not implemented as a holographic image but is displayed as noise.

Although many details are described in detail in the above description, this should be interpreted as an example of a preferred embodiment rather than limiting the scope of the invention. Therefore, the invention should not be determined by the described embodiments, but by the scope of the patent claims and their equivalents.

110: spatial light modulator 120: light source
130: optical mask 140: control unit
150: Spatial light modulator driving unit

Claims (15)

A light source unit that supplies light;
a spatial light modulator that forms an interference pattern to diffract and transmit the light supplied from the light source; and
It is disposed in front of the spatial light modulator and consists of an optical mask that transmits only the diffracted light of a specific order among the diffracted light output from the spatial light modulator,
The spatial light modulator is a liquid crystal panel including a plurality of pixels,
The optical mask includes a plurality of transmission areas corresponding one-to-one to the plurality of pixels of the spatial light modulator,
A hologram display device in which a plurality of transmission areas of the optical mask have different phase values and are arranged irregularly. The holographic display device of claim 1, wherein the light source unit outputs coherent light. delete delete The holographic display device of claim 1, wherein an area of the transmission area of the optical mask is smaller than an area of a pixel of the spatial light modulator. The holographic display device of claim 1, wherein the pitch of the pixels of the spatial light modulator is greater than or equal to the pitch of the transmission area of the optical mask. The holographic display device of claim 1, wherein a phase control layer or a phase control film with a set phase value is provided in the transmission area of the optical mask. delete The hologram display device of claim 1, wherein the phase value of the plurality of transmission areas is in the range of 1-2π. delete The holographic display device of claim 1, wherein the interference pattern is obtained from a holographic image capturing device. The holographic display device according to claim 11, wherein the holographic image photographing device includes a recording optical mask that transmits only an interference pattern of a specific interference order, and the interference pattern pattern is photographed through the recording optical mask. The holographic display device of claim 12, wherein the recording optical mask has the same transmission area arrangement structure as the optical mask. The hologram display device of claim 11, wherein the interference pattern is generated by a computer generated hologram. The hologram display device of claim 14, wherein the interference pattern is calculated based on interference information of object light and reference light and arrangement information of a recording optical mask that transmits only the interference pattern of a specific interference order.

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