Holographic head-up display device

A holographic head-up display device has a light source portion that emits coherent light; an optical modulation portion that modulates the coherent light; a relay optical system that focuses the modulated light; a filter minor that has a reflection area at a focal position of the relay optical system and reflecting light incident through the relay optical system and an absorption area at the periphery of the reflection area and absorbing light incident through the relay optical system; and a transflective mirror that partially transmits and partially reflects light reflected by the filter minor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2017-0085608 filed in the Korean Intellectual Property Office on Jul. 5, 2017, the entire contents of which are incorporated herein by reference.

BACKGROUND

Embodiments of the present inventive concept relates to a holographic display device. More particularly, the present inventive concept relates to a holographic head-up display device that can be provided in a plane or a vehicle.

(b) Description of the Related Art

A technology that records interference patterns containing information of a 3D image in a media such as a film or an electronic device or a technology that generates a 3D image through such a film or electronic device is called holography, and a 3D image realized through the holography is called a hologram.

Recently, a holographic head-up device that enable the surrounding scene and image information to be simultaneously seen in a plane or a vehicle using a holography technology has been researched and developed. Such a holographic head-up display device displays a 3D image by using diffraction and interference of light, and the diffraction of light may cause unnecessary diffraction noise. The diffraction noise is generated due to characteristics of light, and since physical characteristics of light cannot be changed, the holographic head-up display device needs a structural configuration to remove the diffraction noise.

SUMMARY

An image to be displayed may appear blurred or diffused due to the diffraction noise. Further, an unnecessary dummy image may be disposed in a portion other than portions where an image is to be displayed. The diffraction noise and the dummy image may cause deterioration of display quality of the holographic head-up display device.

The present inventive concept has been made in an effort to provide a holographic head-up display device that can remove diffraction noise and a dummy image that may occur in the holographic head-up display device.

A holographic head-up display device according to an exemplary embodiment of the present inventive concept includes: a light source portion configured to emit light, the light being coherent light; an optical modulation portion configured to modulate the light; a relay optical system configured to focus the light; a filter mirror that includes a reflection area disposed at a focal position of the relay optical system and configured to reflect light incident through the relay optical system and an absorption area disposed at a periphery of the reflection area and configured to absorb light incident through the relay optical system; and a transflective mirror configured to partially transmit and partially reflect light reflected by the filter mirror.

A size of the reflection area may be the same as a size of a focal image formed at a focus point of the relay optical system.

The size of the focal image may be inversely proportional to magnification of the relay optical system.

A shape of the reflection area may be the same as that of the focal image.

The shape of the focal image may be the same as that of a display area to which the optical modulation portion is configured to emit light.

The shape of the display area of the optical modulation portion and a shape of the reflection area may be a quadrangle.

The filter mirror may have a flat planar shape.

The filter mirror may have a curved shape that is bent with reference to a virtual central axis in one direction, and the reflection area may be configured to provide a convex reflective side with respect to light incident from the optical modulation portion.

The filter mirror may be configured to have a convex hemispherical shape with respect to light incident from the optical modulation portion, and the reflection area may be configured to provide a convex hemispherical reflective side with respect to light incident from the optical modulation portion.

A holographic head-up display device according to another exemplary embodiment of the present inventive concept includes: a light source portion configured to emit light, the light being coherent light; an optical modulation portion that configured to modulate the light; a relay optical system configured to focus the light; a reflection mirror that is disposed at a focal position of the relay optical system and configured to reflect light incident through the relay optical system; a light absorption plate that is disposed at a rear side of the reflection mirror and configured to absorb light incident through the relay optical system; and a transflective mirror configured to partially transmit and partially reflect light reflected by the reflection mirror.

A size of a reflective side of the reflection mirror may be the same as a size of a focal image formed at a focus point of the relay optical system.

A shape of the reflective side of the reflection mirror may be the same as a shape of the focal image, and the shape of the focal image may be the same as a shape of a display area to which the optical modulation portion emits light.

The shape of the display area of the optical modulation portion and the shape of the reflective side of the reflection mirror may be a quadrangle.

The reflection mirror may be configured to provide a convex reflective side that is bent with reference to a virtual central axis in one direction with respect to light incident from the optical modulation portion.

The reflection mirror may be configured to provide a convex hemispherical reflective side with respect to light incident from the optical modulation portion.

A holographic head-up display device according to still another exemplary embodiment of the present inventive concept includes: a relay optical system configured to focus incident light on a focus point; and a filter mirror that includes a reflection portion configured to reflect a focal image formed at the focus point and an absorption portion configured to absorb diffraction noise formed at a periphery of the focal image.

The reflection portion and the absorption portion may be disposed on the same plane of the filter mirror.

The filter mirror may be configured to have a convex curved shape with respect to the focused light.

The reflection portion and the absorption portion may be disposed on different planes of the filter mirror.

The reflection portion may be configured to have a convex curved shape with respect to the focused light, and the absorption portion may have a flat planar shape.

The holographic head-up display device according to the exemplary embodiment can remove diffraction noise and a dummy image that may occur in the holographic head-up display device so that display quality of an image can be improved.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present inventive concept will be described in more detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present inventive concept.

In addition, the size and thickness of each configuration shown in the drawings are arbitrarily shown for better understanding and ease of description, but the present inventive concept is not limited thereto. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity.

In this specification, the phrase “on a plane” means viewing a target portion from the top, and the phrase “on a cross-section” means viewing a cross-section formed by vertically cutting a target portion from the side.

Hereinafter, referring toFIG. 1andFIG. 2, a holographic display device according to an exemplary embodiment of the present inventive concept will be described.

FIG. 1is a schematic block diagram of a holographic head-up display device according to an exemplary embodiment of the present inventive concept.FIG. 2shows a filter mirror according to the exemplary embodiment of the present inventive concept.

Referring toFIG. 1andFIG. 2, a holographic head-up display device10includes a light source portion110, an optical modulation portion120, a relay optical system130, a filter mirror140, and a transflective mirror150.

The light source portion110emits coherent light having a constant wavelength and continuous phase to the optical modulation portion120. The light source portion110may be provided to enable light of a surface light source to be incident on the optical modulation portion120. For example, the light source portion110may include at least one light source (not shown) emitting coherent light and a collimator lens that converts light from the light source as a collimated beam or an optical condenser (not shown). In this case, at least one of a He—Ne laser, an Ar laser, a semiconductor laser, a laser diode, and the like, which have good coherence, may be used as the light source. Alternatively, as the light source, a light emitting diode (LED) may be used, and when the light emitting diode emits incoherent light, the emitted light may become coherent light by being passed through a pin hole being a minute hole. Alternatively, in an exemplary embodiment, the light source portion110may emit light of a surface light source by using a holographic optical element (HOE) that can change a path of incident light for the light to be emitted with a specific refraction angle with respect to a specific incident angle of the light. The light source portion110may have any structure in which coherent light of a surface light source can be emitted to the optical modulation portion120, and thus there is no limit in structure of the light source portion110.

The optical modulation portion120implements a 3D image by modulating light incident from the light source portion110. That is, the optical modulation portion120diffracts the coherent light, and thus beams meeting on a specific space interfere with each other such that the 3D image can be realized. The optical modulation portion120may be a holographic display that is driven in an analog or digital method. For example, the optical modulation portion120may include a liquid crystal display (LCD), a liquid crystal on silicon (LCoS) display, a digital micro-mirror device (DMD), and the like. Alternatively, in an exemplary embodiment, the optical modulation portion120may be provided as a plate or a film where 3D image information is recorded.

Hereinafter, the optical modulation portion120will be exemplarily described as a holographic display. The optical modulation portion120records interference patterns formed through mathematically calculating and processing an image to be realized as data, and may display the interference pattern based on the recorded data. Light incident on the optical modulation portion120is diffracted by the interference patterns and intensity of the light may be changed while passing through the optical modulation portion120. The optical modulation portion120emits the light diffracted by the interference patterns to the relay optical system130.

The relay optical system130transmits light modulated by the optical modulation portion120to the filter mirror140. The relay optical system130may serve to focus the light emitted from the optical modulation portion120to a desired location of the filter mirror140. The relay optical system130may be provided as a special sphere or nonspherical lens. InFIG. 1, the relay optical system130includes one lens, but the relay optical system130may include a plurality of optical elements such as a convex lens, a concave lens, a mirror, and the like depending on exemplary embodiments.

The filter mirror140includes a reflection area141and an absorption area142. The reflection area141is an area that reflects light incident through the relay optical system130to the transflective mirror150, and the absorption area142is an area that absorbs light incident through the relay optical system130. The reflection area141may be disposed substantially at a center of the filter mirror140, and the absorption area142may be disposed at the periphery of the reflection area141. The reflection area141and the absorption area142may be disposed on the same plane. The relay optical system130may focus the light emitted from the optical modulation portion120on the reflection area141of the filter mirror140, and the reflection area141may be disposed at a focal position of the relay optical system130. A size of the reflection area141may be substantially the same as that of a focal image formed at the focus point of the relay optical system130. The focal image implies an image formed by light that matches the focal point of the relay optical system130. The size of the focal image may be inversely proportional to the magnification of the relay optical system130. That is, the size of the reflection area141may be inversely proportional to the magnification of the relay optical system130. The shape of the reflection area141may be substantially the same as that of the focal image. The shape of the focal image may be the same as a shape of a display area (e.g., an area emitting light). That is, the shape of the reflection area141may be the same as the shape of the display area of the optical modulation portion120. For example, when the shape of the display area of the optical modulation portion120is a quadrangle, the shape of the focal image may be a quadrangle and the shape of the reflection area141may be a quadrangle.

Meanwhile, diffraction noise and dummy images may be iteratively formed at the periphery of the focal image due to aberration of the relay optical system130and diffraction of light. Since the size and the shape of the reflection area141are the same as those of the focal image, the diffraction image and the dummy image are formed in the absorption area142of the filter mirror140. Accordingly, the diffraction noise and the dummy image are absorbed by the absorption area142and thus they are not reflected to the transflective mirror150. That is, the filter mirror140may filter unnecessary diffraction noise and the dummy image other than the focal image. That is, the filter mirror140may serve as a spatial filter and a reflection mirror.

As a curved mirror with focus, the transflective mirror150partially transmits and partially reflects light reflected by the filter mirror140so as to collect the light to the eyes of a user20. The user20may recognize a holographic image realized by the optical modulation portion120as a virtual image located at an infinite or controllable distance. Meanwhile, the transflective mirror150may include a holographic optical element that can change a path of incident light so that the light can be emitted to the eyes of the user20with a specific angle with respect to a specific incident angle of the reflected light.

Hereinafter, various exemplary embodiments of the filter mirror140that can be used in the holographic head-up display device10ofFIG. 1will be described. A direction in which the light proceeds toward the filter mirror140from the optical modulation portion120will be referred to as a first direction X, and a direction that is parallel with a plane of the filter mirror140, on which the light is incident, and perpendicular to the first direction X, will be referred to as a second direction Y. The second direction Y may be a horizontal direction or a left and right direction of the filter mirror140as shown inFIG. 2. In addition, a direction that is perpendicular to the first direction X and the second direction Y will be referred to as a third direction Z. As shown inFIG. 2, the third direction Z may be a vertical direction or a top and bottom direction of the filter mirror140.

In the holographic head-up display device10, the filter mirror140may be inclined at a predetermined angle with respect to at least one of the first direction X, the second direction Y, and the third direction Z so as to reflect incident light to the transflective mirror150(as exemplarily shown inFIG. 1, the filter mirror140is inclined at a predetermined angle with respect to the third direction Z). However, in the following description of exemplary embodiments of the filter mirror140, the filter mirror140will be described to be disposed on a plane that is perpendicular to the first direction X regardless of inclination of the filter mirror140.

Referring toFIG. 2, when the filter mirror140is viewed from the first direction X, the filter mirror140may have a flat planar shape where the quadrangular-shaped reflection area141and the absorption area142disposed at the periphery of the reflection area141are formed. InFIG. 2, the shape of the reflection area141is a quadrangle corresponding to the shape of the display area of the optical modulation portion120. When the shape of the display area of the optical modulation portion120is a circle or a polygon, the shape of the reflection area141may be a circle or a polygon corresponding to the shape of the display area of the optical modulation portion120. Further, the absorption area142may have a size that can absorb unnecessary diffraction noise, dummy images, and the like other than the focal image.

Next, referring toFIG. 3, a filter mirror140according to another exemplary embodiment will be described.FIG. 3shows a filter mirror according to another exemplary embodiment of the present inventive concept.

Referring toFIG. 3, a filter mirror140includes a reflection area141and an absorption area142, and may have a shape that is bent with reference to a virtual central axis in the third direction Z. Accordingly, the reflection area141can provide a reflective side that is convex with reference to the virtual central axis in the third direction Z with respect to light incident from the optical modulation portion120.

Compared to the filter mirror140ofFIG. 2, the reflection area141of the exemplary ofFIG. 3can reflect light expanded in the second direction Y to the transflective mirror150. That is, light expanded further to the left and right direction of the transflective mirror150may be incident on the transflective mirror150, and accordingly, the user20can view a virtual image expanded to the left and right sides. That is, a field of view of the holographic head-up display device10can be further widened to the left and right direction.

Next, referring toFIG. 4, a filter mirror140according to another exemplary embodiment will be described.FIG. 4shows a filter mirror according to another exemplary embodiment of the present inventive concept.

Referring toFIG. 4, a filter mirror140includes a reflection area141and an absorption area142, and may have a shape that is bent with reference to a virtual central axis in the second direction Y. Accordingly, the reflection area141provides a reflective side that is convex with respect to the virtual central axis in the second direction Y with respect to light incident from the optical modulation portion120.

Compared to the filter mirror140ofFIG. 2, the reflection area141of the exemplary ofFIG. 3can reflect light expanded in the third direction Z to the transflective mirror150. That is, light expanded further to the top and bottom direction of the transflective mirror150may be incident on the transflective mirror150, and accordingly, the user20can view a virtual image expanded to the top and bottom sides. That is, a field of view of the holographic head-up display device10can be further widened vertically.

Next, referring toFIG. 5, a filter mirror140according to another exemplary embodiment will be described.FIG. 5shows a filter mirror according to another exemplary embodiment of the present inventive concept.

Referring toFIG. 5, a filter mirror140includes a reflection area141and an absorption area142, and may have a hemispherical shape that is convex with respect to light incident from the optical modulation portion120. Accordingly, the reflection area141may provide a hemispherical reflective side that is convex with respect to the light incident from the optical modulation portion120.

Compared to the filter mirror140ofFIG. 2, the reflection area141of the exemplary ofFIG. 5can reflect light expanded in the second direction Y and the third direction Z to the transflective mirror150. That is, light expanded further to the horizontal direction and the vertical direction of the transflective mirror150may be incident on the transflective mirror150, and accordingly, the user20can view a virtual image expanded to the vertical and horizontal directions. That is, a field of view of the holographic head-up display device10can be further widened vertically and horizontally.

Hereinafter, referring toFIG. 6andFIG. 7, a holographic head-up display device10according to another exemplary embodiment will be described. Only differences with the above-described holographic head-up display device ofFIG. 1andFIG. 2will be mainly described.

FIG. 6is a schematic block diagram of a holographic head-up display device according to another exemplary embodiment of the present inventive concept.FIG. 7shows a filter mirror according to the other exemplary embodiment of the present inventive concept.

Referring toFIG. 6andFIG. 7, a filter mirror140includes a reflection mirror144and a light absorption plate145.

The reflection mirror144reflects light incident through a relay optical system130to a transflective mirror150. The light absorption plate145is disposed at a rear side of the reflection mirror144while overlapping the reflection mirror144, and absorbs light incident through the relay optical system130. That is, the reflection mirror144and the light absorption plate145are disposed on different planes.

The relay optical system130may focus light emitted from an optical modulation portion120to the reflection mirror144of the filter mirror140, and the reflection mirror144may be disposed on a focal position of the relay optical system130. A size of a reflective side of the reflection mirror144may be substantially the same as a size of a focal image formed at a focal point of the relay optical system130. The size of the reflective side of the reflection mirror144may be inversely proportional to magnification of the relay optical system130. A shape of the reflective side of the reflection mirror144may be substantially the same as a shape of the focal image. That is, the shape of the reflective side of the reflection mirror144may be the same as a shape of a display area of the optical modulation portion120.

As the size and the shape of the reflective side of the reflection mirror144are the same as those of the focal image, diffraction images and dummy images formed at the periphery of the focal image are passed through the periphery of the reflection mirror144and thus formed in the light absorption plate145. Accordingly, the diffraction noise and the dummy image are absorbed by the light absorption plate145and thus they are not reflected to the transflective mirror150. That is, the filter mirror140may filter unnecessary diffraction noise and dummy images other than the focal image.

The transflective mirror150partially transmits and partially reflects light reflected by the reflection mirror144to collect the light to the eyes of a user20.

As shown inFIG. 7, when the filter mirror140is viewed in a first direction X, each of the reflection mirror144and the light absorption plate145may substantially have a flat planar shape, and the reflection mirror144and the light absorption plate145may overlap each other at about a center portion of the light absorption plate145.

InFIG. 7, the shape of the reflective side of the reflection mirror144is a quadrangle corresponding to the shape of the display area of the optical modulation portion120. Alternatively, the shape of the reflective side of the reflection mirror144may be a circle or a polygon corresponding to the shape of the display area of the optical modulation portion120. Further, the light absorption plate145may have a size that is appropriate for absorption of unnecessary diffraction noise or a dummy image other than the focal image, and there is no limit in size or shape of the light absorption plate145.

Except for such a difference, the features of the exemplary embodiment ofFIG. 1andFIG. 2can be entirely applied to the exemplary embodiment ofFIG. 6andFIG. 7, and therefore a description of the features of the above-described exemplary embodiment ofFIG. 1andFIG. 2will be omitted.

Hereinafter, other exemplary embodiments of the filter mirror140that can be used in the holographic head-up display device10ofFIG. 6will be described with reference toFIG. 8toFIG. 10.

FIG. 8shows a filter mirror according to another exemplary embodiment of the present inventive concept.

Referring toFIG. 8, a reflection mirror144may have a curved shape that is bent with reference to a virtual central axis in a third direction Z. That is, the reflection mirror144can provide a convex reflective side that is bent with reference to the virtual central axis in the third direction Z with respect to light incident from the optical modulation portion120. In this case, the light absorption plate145may have a flat planar shape. Compared with the filter mirror140illustrated inFIG. 7, the reflection mirror144of the embodiment ofFIG. 8can reflect light that extends in the second direction Y to the transflective mirror150. That is, light further expanded in the left and right direction of the transflective mirror150may be incident on the transflective mirror150, and accordingly, the user20can view a virtual image that is expanded in the left and right direction. That is, a field of view of the holographic head-up display device10can be further widened in the left and right direction.

FIG. 9shows a filter mirror according to another exemplary embodiment of the present inventive concept.

Referring toFIG. 9, a reflection mirror144may have a curved shape that is bent with reference to a virtual central axis in a second direction Y. That is, the reflection mirror144can provide a convex reflective side that is bent with reference to the virtual central axis in the second direction Y with respect to light incident from the optical modulation portion120. In this case, the light absorption plate145may have a flat planar shape.

Compared to the filter mirror140ofFIG. 7, a reflection mirror144of an exemplary embodiment ofFIG. 9may reflect light expanded in the third direction Z to the transflective mirror150. That is, light further expanded in the top and bottom direction of the transflective mirror150may be incident on the transflective mirror150, and accordingly, the user20can view a virtual image that is expanded in the top and bottom direction. That is, a field of view of the holographic head-up display device10can be further widened in the top and bottom direction.

FIG. 10shows a filter mirror according to still another exemplary embodiment of the present inventive concept.

Referring toFIG. 10, a reflection mirror144may have a convex hemispherical shape with respect to light incident from the optical modulation portion120. Accordingly, the reflection mirror144can provide a hemispherically convex reflective side with respect to light incident from the optical modulation portion120. In this case, the light absorption plate145may have a flat planar shape.

Compared to the filter mirror140ofFIG. 7, a reflection mirror144of an exemplary embodiment ofFIG. 10may reflect light expanded in the second direction Y and the third direction Z to the transflective mirror150. That is, light further expanded in the vertical and horizontal directions of the transflective mirror150may be incident on the transflective mirror150, and accordingly, the user20can view a vertically and horizontally expanded virtual image. That is, a field of view of the holographic head-up display device10can be further expanded in the horizontal and vertical directions.

As described above, the holographic head-up display device10according to the above-described exemplary embodiments of the present inventive concept can remove diffraction noises and dummy images by using the filter mirror140including the reflection area141or the reflection mirror144of which the size and the shape are the same as those of a focal image formed at a focus point of the relay optical system130, and accordingly, a more clear image can be provided.

While the present inventive concept has been described in connection with what is presently considered to be practical example embodiments, it is to be understood that the present inventive concept is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. It will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the present inventive concept. Accordingly, the true scope of the present inventive concept should be determined by the technical idea of the appended claims.