KR20160060522A - Backlight unit for holographic display apparatus and holographic display apparatus including the same - Google Patents

Abstract

Disclosed are a backlight unit for a binocular holographic display device and a binocular holographic display device having the same. The backlight unit according to an embodiment of the present invention can comprise: a light source unit which provides coherent illumination light; and a transparent light guide plate which includes an entrance face on which the illumination light provided from the light source unit is incident and an exit face from which the entered illumination light is emitted. The light source unit includes a beam deflector which adjusts an incident angle of the illumination light which is incident on the light guide plate. Since the backlight unit includes a beam deflector capable of changing a propagation direction of light, a position of a visual field in which a holographic image is formed in the binocular holographic display device can be adjusted to correspond to movement of an observer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit for a holographic display device and a holographic display device including the same,

The disclosed embodiments relate to a backlight unit and a holographic display device including the backlight unit, and more particularly to a backlight unit for a binocular holographic display device that provides a holographic image having a different viewpoint at two viewports, To a graphic display device.

As a method of implementing a three-dimensional image, a spectacle method and a non-spectacle method are widely commercialized and used. There are polarizing glasses and shutter glasses for the glasses, and lenticular and parallax barriers for the glassesless. These methods use the binocular parallax of the two eyes, which not only limits the increase in the number of viewpoints, but also causes viewers to feel fatigue because the depth perception recognized by the brain does not coincide with the focus of the eyes.

Background Art [0002] Recently, a holographic display system has been put to practical use as a three-dimensional image display system in which depth perception recognized by the brain matches the focal point of the eye and can provide full parallax. The holographic display system utilizes the principle that an image of an original object is reproduced by irradiating reference light to a hologram pattern on which interference fringes obtained by interfering with reference light from object light reflected from an original object are diffracted. Currently, the holographic display method that is being put to practical use provides a computer generated hologram (CGH) as an electrical signal to the spatial light modulator, rather than directly exposing the original object to obtain a hologram pattern. The spatial light modulator forms a hologram pattern according to the input CGH signal and diffracts the reference light so that a three-dimensional image can be generated.

However, implementing a complete holographic display scheme requires very high resolution spatial light modulators and very high data throughput. In recent years, a binocular hologram method has been proposed in which a hologram image is provided only to a view area corresponding to both eyes of an observer in order to alleviate data throughput and resolution. For example, only a hologram image having a viewpoint corresponding to the observer's left eye view area and a hologram image having a viewpoint corresponding to the observer's right eye view region are generated and provided to the observer's left eye and right eye, respectively. In this case, since it is not necessary to generate hologram images for the remaining time points, the data throughput can be greatly reduced, and the resolution condition of the spatial light modulator can be satisfied even in the currently commercialized display device.

There is provided a backlight unit for a binocular holographic display device, each of which provides a holographic image having a different viewpoint to two viewports.

Further, a binocular holographic display device including the backlight unit is provided.

A backlight unit according to an exemplary embodiment includes a light source unit for providing illumination light; A transparent light guide plate having a light incident surface on which the illumination light provided by the light source unit is incident and a light output surface for emitting the incident illumination light; An input coupler for guiding illumination light incident on the light incident surface of the light guide plate into the light guide plate; And an output coupler disposed on a light emitting surface of the light guide plate and emitting illumination light to the outside of the light guide plate. The light source unit may include a beam deflector for adjusting an incident angle of the illumination light incident on the light guide plate.

For example, the light source unit may include a first light source unit for providing a first illumination light in a first view area and a second light source unit for providing a second illumination light in a second view area different from the first view area, Wherein the input coupler includes a first input coupler for advancing the first illumination light to the inside of the light guide plate, and a second input coupler for guiding the second illumination light to the light guide plate, the first light incident surface, and the second light incident surface, And a second input coupler for driving the input coupler to the inside of the input coupler.

For example, the first light incidence surface and the second light incidence surface may be disposed on opposite sides of the light guide plate, the first light source portion may be disposed opposite to the first light incidence surface, And may be disposed opposite to the second light incidence surface.

Also, the light guide plate may be configured such that the first illumination light and the second illumination light are emitted through the same light exit surface, and the output coupler may be configured such that the first illumination light and the second illumination light are emitted at different angles.

For example, the first light source unit may include: a first light source that generates a first illumination light; A first collimator for converting the first illumination light into a parallel beam; A first beam expander for increasing a beam diameter of the first illumination light; And a first beam deflector for adjusting an incident angle of the first illumination light incident on the first light incidence surface.

The second light source unit may further include: a second light source that generates a second illumination light; A second collimator for converting the second illumination light into a parallel beam; A second beam expander for increasing the beam diameter of the second illumination light; And a second beam deflector for adjusting an incident angle of the second illumination light incident on the second light incidence surface.

For example, the first and second light sources may be configured to emit coherent white light.

In another embodiment, the light source unit includes: a light source for generating illumination light; A collimator for converting the illumination light into a parallel beam; A beam expander for increasing the beam diameter of the illumination light to provide the beam deflector to the beam deflector; And a beam splitter for dividing the illumination light from the beam deflector into first illumination light and second illumination light.

The light incidence surface may include a first light incidence surface on which the first illumination light is incident and a second light incidence surface on which the second illumination light is incident, and the input coupler may include a first light source for advancing the first illumination light into the light guide plate, And a second input coupler for advancing the input coupler and the second illumination light into the light guide plate.

The first light incidence surface and the second light incidence surface may be disposed on opposite sides of the light guide plate, respectively.

The light guide plate may be configured such that the first illumination light and the second illumination light are emitted through the same light emitting surface, and the output coupler is configured such that the first illumination light is emitted to the first view area and the second illumination light is emitted to the second And can be configured to be emitted to the field of view.

In another embodiment, the light source unit includes: a light source for generating illumination light; A collimator for converting the illumination light into a parallel beam; A beam expander for increasing the beam diameter of the illumination light; And a beam splitter that divides the illumination light from the beam expander into first illumination light and second illumination light.

The beam deflector may include a first beam deflector for adjusting the incident angle of the first illumination light and a second beam deflector for adjusting the incident angle of the second illumination light, Wherein the input coupler includes a first input coupler for advancing the first illumination light to the inside of the light guide plate and a second input coupler for advancing the second illumination light to the inside of the light guide plate, Input coupler.

The first light incidence surface and the second light incidence surface may be disposed on opposite sides of the light guide plate, respectively.

The light guide plate may be configured such that the first illumination light and the second illumination light are emitted through the same light emitting surface, and the output coupler is configured such that the first illumination light is emitted to the first view area and the second illumination light is emitted to the second And can be configured to be emitted to the field of view.

In another embodiment, the light source unit includes: a light source for generating illumination light; A collimator for converting the illumination light into a parallel beam; And a beam expander for increasing the beam diameter of the illumination light to provide the beam deflector to the beam deflector.

The beam deflector may be configured to alternately provide illumination light to different first and second view areas.

The light incidence surface and the input coupler may be disposed at one edge of the light guide plate, and the light source unit may be disposed opposite the light incidence surface of the light guide plate.

For example, the first view area and the second view area may be located at different positions in the horizontal direction, and the light source part may be disposed at the upper side edge or the lower side edge arranged in the vertical direction of the light guide plate.

Further, the light source unit may further include a switch configured to alternately provide the illumination light, which is deflected by the beam deflector, to the first and second view zones different from each other.

The backlight unit may further include an achromatization element for converting the illumination light separated by the output coupler into white light.

The input coupler and the output coupler may include a holographic grating having a diffraction pattern or a photopolymer having a periodic refractive index distribution.

Wherein the input coupler and the output coupler are disposed on the first surface and the second surface, respectively, of the light guide plate, wherein the input coupler and the output coupler are disposed in an edge area of the first surface, Region. ≪ / RTI >

Meanwhile, a holographic display device according to another embodiment includes: a backlight unit having the above-described configuration; And a spatial light modulator for modulating the illumination light provided by the backlight unit to form a holographic image.

The holographic display device may further include a line-of-sight tracing unit for tracing the pupil position of the observer, and the beam deflector may be configured to adjust an incident angle of the illumination light incident on the light guide plate corresponding to a change in the pupil position of the observer.

Since the backlight unit according to the disclosed embodiment includes the beam deflector capable of changing the light advancing angle, the position of the viewing area where the holographic image is formed in the binocular holographic display device can be adjusted in accordance with the movement of the observer. Further, the backlight unit according to the disclosed embodiment can be manufactured with a small thickness, and can effectively provide homogeneous illumination light.

1 is a block diagram schematically showing a configuration of a backlight unit according to an embodiment.
FIG. 2 is a perspective view schematically showing a configuration of a holographic display device including the backlight unit shown in FIG. 1. FIG.
3 is a perspective view schematically showing the configuration of another holographic display device.
4 is a perspective view schematically showing the configuration of another holographic display device.
5 is a cross-sectional view illustrating the configuration of the beam deflector and the light guide plate of the backlight unit shown in FIG.
6A and 6B are cross-sectional views illustrating exemplary operations of the beam deflector of the backlight unit shown in FIG.
Figs. 7 to 9 are sectional views exemplarily showing various other configurations of the light deflector and the beam deflector of the backlight unit shown in Fig. 1. Fig.
10 is a block diagram schematically showing a configuration of a backlight unit according to another embodiment.
11 is a schematic view showing the configuration of the backlight unit shown in Fig.
12 is a block diagram schematically showing a configuration of a backlight unit according to another embodiment.
13 is a schematic view showing the configuration of the backlight unit shown in Fig.
14 is a block diagram schematically showing the configuration of a backlight unit according to another embodiment.
15 is a perspective view schematically showing a configuration of a holographic display device including the backlight unit shown in FIG.
16 is a perspective view schematically showing the configuration of another holographic display device.

Hereinafter, a backlight unit for a holographic display device and a holographic display device including the same will be described in detail with reference to the accompanying drawings. In the following drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, the embodiments described below are merely illustrative, and various modifications are possible from these embodiments. Also, in the layer structures described below, the expressions "top" or "on top"

1 is a block diagram schematically showing a configuration of a backlight unit 100 according to an embodiment. 1, the backlight unit 100 according to the present embodiment includes light source units 110a and 110b for providing illumination light, a light incidence surface on which the illumination light provided from the light source units 110a and 110b is incident, Input couplers 131a and 131b for moving the illumination light incident on the light incidence surface of the light guide plate 130 to the inside of the light guide plate 130 and the light incident surface of the light guide plate 130, And an output coupler 135 disposed to emit the illumination light to the outside of the light guide plate 130. If desired, the backlight unit 100 may further include an achromatization element 136 that converts the color light separated by the output coupler 135 into white light.

According to the present embodiment, the light source units 110a and 110b of the backlight unit 100 may be configured to provide illumination light to at least two different viewports. For example, the light source units 110a and 110b may include a first light source unit 110a that provides illumination light in a first view area and a second light source unit 110b that provides illumination light in a second view area that is different from the first view area . For example, the first light source unit 110a may provide illumination light to the observer's right eye view region and the second light source unit 110b may provide illumination light to the observer's left eye view region. The input couplers 131a and 131b are connected to the first input coupler 131a and the second input coupler 131b in order to advance the illumination light emitted from the first and second light source units 110a and 110b into the light guide plate 130. [ And a coupler 131b. The light guide plate 130 may include a first light incidence surface on which the illumination light emitted from the first light source portion 110a is incident and a second light incidence surface on which the illumination light emitted from the second light source portion 110b is incident. As described later, the first input coupler 131a may be disposed on the first light incidence surface or may be disposed opposite to the first light incidence surface, and the second input coupler 131b may be disposed on the second light incidence surface, It can be arranged facing the light surface.

For example, the first light source unit 110a includes a first light source 111a that generates illumination light, a first collimator 112a that converts the illumination light into a parallel beam, a first beam expander 113a that increases the beam diameter of the illumination light, And a first beam deflector 114a for adjusting the incident angle of the illumination light incident on the first light incidence surface. Similarly to the first light source part 110a, the second light source part 110b also includes a second light source 111b for generating illumination light, a second collimator 112b for converting the illumination light into a parallel beam, a second collimator 112b for increasing the beam diameter of the illumination light, A beam expander 113b, and a second beam deflector 114b for adjusting the incident angle of the illumination light incident on the second light incidence surface.

In order to use the backlight unit 100 in a holographic display device, the first and second light sources 111a and 111b may include a laser that generates light having high coherence. However, if the illumination light has a certain level of spatial coherence, it can be sufficiently diffracted and modulated by the spatial light modulator, so that a light emitting diode (LED) is used as the first and second light sources 111a and 111b It is also possible to do. In addition to light emitting diodes, any other light source can be used if it emits light with some degree of spatial coherence. The first and second light sources 111a and 111b may be configured to include, for example, an array of a plurality of light emitting diodes emitting red, green, and blue light, respectively, to emit white light mixed with red, green, and blue light .

The first and second collimators 112a and 112b are arranged in order to convert the divergent illumination light emitted from the first and second light sources 111a and 111b into a parallel beam, for example, a refractive lens having a positive refractive power And may include a diffractive optical element. Also, the first and second beam expanders 113a and 113b may serve to homogenize the illumination light and increase the beam diameter of the illumination light. For example, the first and second beam expanders 113a and 113b may change the shape and size of the illumination light to be the same as the shapes and sizes of the first and second light incidence surfaces of the light guide plate 130. [ The first and second beam expanders 113a and 113b may include, for example, a transparent integrator rod or a light guide plate. Although the first and second collimators 112a and 112b are shown closer to the first and second light sources 111a and 111b than the first and second beam expanders 113a and 113b in FIG. 1, And the arrangement order of the first and second collimators 112a and 112b and the first and second beam expanders 113a and 113b may be reversed. When the first and second light sources 111a and 111b emit parallel illumination light or can emit illumination light having a large beam diameter, the first and second collimators 112a and 112b and the first and second collimators 112a and 112b, 2 beam expanders 113a and 113b may be omitted.

The first and second beam deflectors 114a and 114b may control the incident angle of the illumination light incident on the first and second light incidence surfaces of the light guide plate 130, respectively. For example, the first and second beam deflectors 114a and 114b may be a galvanometer mirror capable of rotating the reflecting surface, an electrowetting device capable of electrically changing the slope of the interface between the polar liquid and the non- And an acoustooptic device capable of changing the refractive index distribution using a sound wave. Instead, the first and second beam deflectors 114a and 114b may rotate the first and second light source portions 110a and 110b as a whole, without reflecting, refracting, or diffracting the light, It can also be changed. The first and second beam deflectors 114a and 114b are used to change the angle of incidence of the illumination light incident on the first and second light incidence surfaces of the light guide plate 130 so that the illumination light emitted from the light exit surface of the light guide plate 130 It is possible to adjust the traveling direction of the light. Therefore, as described later, the backlight unit 100 according to the present embodiment can actively cope with the change in the line of sight of the observer.

2 is a perspective view schematically showing a configuration of a holographic display device 1000 including the backlight unit 100 shown in FIG. Referring to FIG. 2, the holographic display device 1000 according to the present embodiment may include a backlight unit 100 and a spatial light modulator 150. The backlight unit 100 serves to provide illumination light to the spatial light modulator 150 and the spatial light modulator 150 functions to form a hologram pattern having interference fringes for modulating the illumination light. The illumination light is diffracted and modulated by the hologram pattern formed in the spatial light modulator 150, so that a hologram image can be formed at a predetermined spatial position.

The holographic display device 1000 includes a gaze tracking unit 160 for tracking a pupil position of an observer and a first and a second beam deflector 160 according to pupil positions of an observer measured by the gaze tracking unit 160 114a, and 114b of the first embodiment. For example, when the pupil position of the observer changes, the controller 170 controls the first and second beam deflectors 114a and 114b so that the position on the space where the hologram image is formed coincides with the observer's pupil position. Can be adjusted.

The holographic display device 1000 having the above-described structure can provide hologram images with different viewpoints to the observer's left eye (EL) and right eye (ER), respectively, in a binocular hologram manner. For example, the holographic display device 100 can recognize the position of the left eye (EL) and the right eye (ER) of an observer by using the eye tracking unit 160, And a right eye hologram image having a different viewpoint from the left eye hologram image can be provided in the observer's right eye (ER) field of view.

Unlike the left-eye image and the right-eye image of a stereoscopic system, the left-eye hologram image and the right-eye hologram image provided by the holographic display device 1000 can provide stereoscopic effect to the observer alone, Only the points are different. In the stereoscopic method, a binocular disparity is provided when a two-dimensional image for the left eye and a two-dimensional image for the right eye are recognized in the left eye and the right eye of the observer, respectively. Therefore, in the stereoscopic method, neither the left eye image nor the right eye image generates a stereoscopic effect, and the depth perceived by the brain does not coincide with the focus of the eye, so that the observer can feel fatigue. On the other hand, since the holographic display device 1000 forms a left-eye hologram image and a right-eye hologram image at a position on a predetermined space, that is, in an observer's left eye (EL) and right eye (ER) The focus and the focus of the eyes can be matched and can provide complete parallax. The reason why the holographic display device 1000 according to the present embodiment provides only binocular viewpoints is that since the observer can recognize only two viewpoints with the left eye and the right eye, So that the data throughput can be reduced and the hologram image can be formed with the spatial light modulator 150 having a relatively low resolution.

Referring to FIG. 2 again, the first light source unit 110a and the second light source unit 110b may be disposed on both sides of the light guide plate 130, respectively. That is, the first and second light source units 110a and 110b may be disposed on opposite sides of the light guide plate 130. For example, the first light source unit 110a may be disposed on the left side surface of the light guide plate 130, and the second light source unit 110b may be disposed on the right side surface of the light guide plate 130. [ 2, the first light source unit 110a and the second light source unit 110b are directly opposed to the left surface and the right surface of the light guide plate 130, respectively. However, the present invention is not limited thereto. For example, the first light source unit 110a may be disposed near the left edge of the light guide plate 130, and the second light source unit 110b may be disposed near the right edge of the light guide plate 130. [ The specific positions of the first light source unit 110a and the second light source unit 110b may vary according to the position and structure of the input couplers 131a and 131b in the light guide plate 130. [

The illumination light provided from the first light source unit 110a may be incident on the left side surface of the light guide plate 130 and then emitted to the front surface of the light guide plate 130 to enter the spatial light modulator 150. [ Then, the spatial light modulator 150 modulates the illumination light provided from the first light source unit 110a to form a hologram image in the observer's right eye (ER) field of view. The illumination light provided from the second light source unit 110b may be incident on the right side surface of the light guide plate 130 and then emitted to the front surface of the light guide plate 130 to enter the spatial light modulator 150. [ Then, the spatial light modulator 150 modulates the illumination light provided by the second light source unit 110b to form a hologram image in the left eye (EL) field of view of the observer.

The first light source unit 110a and the second light source unit 110b may simultaneously emit illumination light, but may alternatively turn on / off alternately. For example, the second light source unit 110b may be turned off while the first light source unit 110a is turned on to provide the illumination light. Then, a hologram image can be provided only to the observer's right eye (ER) viewing area. At this time, the spatial light modulator 150 may form a hologram pattern for forming a right eye hologram image. Then, the first light source unit 110a is turned off and the second light source unit 110b is turned on to provide illumination light. Then, a hologram image can be provided only to the observer's left eye (EL) viewing area. At this time, the spatial light modulator 150 may form a hologram pattern for forming a left eye hologram image. The first light source unit 110a and the second light source unit 110b simultaneously provide illumination light. The spatial light modulator 150 generates a holographic pattern for forming a left eye hologram image and a hologram pattern for forming a right eye hologram image. Can be superimposed and displayed. Then, a right-eye hologram image and a left-eye hologram image can be provided to the observer's right eye (ER) and left eye (EL) field of view, respectively. The operation of the first and second light source units 110a and 110b and the spatial light modulator 150 may be controlled by the controller 170. [

On the other hand, if the observer moves the seat or moves the head to change the pupil position of the observer, the gaze tracking unit 160 may track the pupil position of the observer and provide the result to the controller 170. The controller 170 controls the first and second beam deflectors 114a and 114b of the first and second light source units 110a and 110b so that the right eye hologram image and the left eye hologram image are formed in accordance with the pupil position of the observer. Can be controlled. That is, the control unit 170 may change the traveling angle of the illumination light to the first and second beam deflectors 114a and 114b in response to the pupil position change of the observer. For example, as shown by the arrows in FIG. 2, the first and second light source portions 110a and 110b may be rotated as a whole to change the angle at which the illumination light enters the light guide plate 130. FIG. Instead, a progress angle of the illumination light may be changed using a galvanometer mirror, an electrowetting element, an acoustooptic element, or the like.

As described above, since the backlight unit 100 according to the present embodiment can change the advancing angle of the illumination light, the position of the field of view in which the hologram image is formed in the holographic display device 1000 of the two- It can be adjusted in response to movement. In addition, the backlight unit 100 according to the present embodiment can be manufactured with a small thickness, and can uniformly provide illumination light using the first and second beam expanders 113a and 113b and the light guide plate 130 .

3 is a perspective view schematically showing the configuration of another holographic display device 1100. As shown in FIG. 3, the holographic display device 1100 includes a backlight unit 100 'in which first and second light source units 110a and 110b are disposed on upper and lower sides of the light guide plate 130, respectively Differs from the holographic display device 1000 shown in Fig. The first light source unit 110a and the second light source unit 110b are arranged in the vertical direction of the light guide plate 130. The first light source unit 110a and the second light source unit 110b are disposed at different positions along the horizontal direction, And may be disposed on the disposed upper side or lower side edge. For example, the first light source unit 110a may be disposed on the upper side surface of the light guide plate 130, and the second light source unit 110b may be disposed on the lower side surface of the light guide plate 130. 2 and 3, the first light source unit 110a and the second light source unit 110b are disposed on opposite sides of the light guide plate 130 in common.

FIG. 4 is a perspective view schematically showing the configuration of another holographic display device 1200. FIG. 4, the backlight unit 100 "of the holographic display device 1200 has a structure in which the first and second light source portions 110a and 110b include an array of a plurality of light source cells, The first light source unit 110a includes a plurality of light source cells arranged along the upper side of the light guide plate 130 and the second light source unit 110b includes the light guide plate 130. [ And a plurality of light source cells arranged along the lower side of the first light source unit 110. The plurality of light source cells of the first light source unit 110a may include a first light source 111a, a first collimator 112a, The second light source unit 110b may include a second light source 111b, a second collimator 112b, and a second light source 111b for each of the plurality of light source cells of the second light source unit 110b. 2 beam expander 113b, and a second beam deflector 114b, respectively. Although not shown, First and second light sources (110a, 110b) of the illustrated light unit 100 may also include a plurality of light sources respectively, the array of cells.

5 is a sectional view exemplarily showing the configurations of the beam deflectors 114a and 114b and the light guide plate 130 of the backlight unit 100 shown in FIG. 2 to 4, the light guide plate 130 serves to uniformly provide the entire area of the spatial light modulator 150 by emitting all the two illumination light incident from both sides thereof to the front face. The angle and direction at which the illumination light is emitted from the light guide plate 130 depend on the angle and direction at which the illumination light enters the light guide plate 130. The light guide plate 130 is incident from the first and second light source units 110a and 110b, One or two illumination lights can be emitted at different angles and directions. Therefore, a hologram image can be formed in the left and right eye view regions of the observer, respectively, and the position of the hologram image can be adjusted using the beam deflectors 114a and 114b. Hereinafter, the structure of such a light guide plate 130 will be described in detail.

Referring to FIG. 5, the light guide plate 130 is made of a transparent material and may be formed in the form of a flat plate. Both side surfaces 130a and 130b of the light guide plate 130 are first and second light incidence surfaces on which the illumination light is incident and a front surface 130c is a light exit surface on which the illumination light exits. First and second input couplers 131a and 131b for advancing illumination light into the light guide plate 130 may be disposed on the first and second light incident surfaces disposed on both sides of the light guide plate 130. [ An output coupler 135 for emitting illumination light to the outside of the light guide plate 130 may be disposed on a light emitting surface disposed on the front surface 130c of the light guide plate 130. [ The first and second beam deflectors 114a and 114b may be disposed so as to face the first and second input couplers 131a and 131b, respectively. Although a galvanometer mirror is illustrated as an example of the first and second beam deflectors 114a and 114b in Fig. 5, an electro-wetting element or an acousto-optic element may be used in addition to the galvanometer mirror, A mechanical rotating device that rotates the light source units 110a and 110b as a whole may be used. Although only the first and second beam deflectors 114a and 114b are shown in FIG. 5 for the sake of convenience, the first and second light sources 110a and 110b may be disposed opposite to the first and second light incidence surfaces, respectively. have.

The first and second input couplers 131a and 131b may be a diffractive optical element that diffracts and transmits illumination light so that the illumination light advances inwardly into the light guide plate 130. [ For example, the first and second input couplers 131a and 131b may be a holographic grating having a predetermined diffraction pattern or a photopolymer having a periodic refractive index distribution. The illumination light may be totally and repeatedly reflected from the front surface 130c and the back surface 130d of the light guide plate 130 while inclining the interior of the light guide plate 130. [ Therefore, the illumination light can travel inside the light guide plate 130 with almost no loss. When the illumination light is incident on the output coupler 135 disposed on the front surface 130c of the light guide plate 130, a part of the illumination light is transmitted to the outside through the front surface 130c of the light guide plate 130 by the output coupler 135 And the remaining part of the illumination light can be totally reflected. In this way, the illumination light can be uniformly emitted over the entire area of the light-exiting surface of the light guide plate 130. [ This output coupler 135 may be a diffractive optical element that diffracts and transmits a portion of the illumination light. For example, the output coupler 135 may be a holographic grating having a predetermined diffraction pattern or a photopolymer having a periodic refractive index distribution.

The first and second input couplers 131a and 131b and the output coupler 135 may have some wavelength dependency or chromatic aberration depending on their structure. In this case, the white illumination light may be color-separated. For example, red, green, and blue light may be emitted from the light exit surface of the light guide plate 130 at different angles. Then, the quality of the illumination light incident on the spatial light modulator 150 deteriorates, and thus a hologram image having a distorted color may be formed. In order to prevent this, an achromatization element 136 for converting the illumination light separated by the output coupler 135 into white light may be disposed to face the light exit surface of the light guide plate 130. [ For example, the color cast element 136 may be a diffractive optical element that diffracts and transmits red, green, and blue light that travels at different angles so that they all go through the same angle.

The first and second input couplers 131a and 131b and the output coupler 135 are arranged such that the illumination light incident perpendicularly to the first and second light incidence surfaces of the light guide plate 130 is emitted vertically from the light exit surface of the light guide plate 130. [ . For example, the first and second input couplers 131a and 131b may be configured such that the illumination light incident perpendicularly to the first and second light incidence surfaces of the light guide plate 130 travels through the interior of the light guide plate 130 at an angle of? Lt; / RTI > The output coupler 135 may be configured to diffract the illumination light incident at an angle of [theta] perpendicular to the light output surface of the vertical light guide plate 130. [ However, depending on the embodiment, the incident angles of the illumination light on the first and second light incidence surfaces and the exit angle relationship of the illumination light on the light exit surface may be selected differently. For example, the illumination light incident on the first and second light incidence surfaces at angles of &thetas; 1 may be vertically emitted from the light exit surface, or the illumination light incident perpendicularly to the first and second light incidence surfaces may be emitted from the light exit surface lt; RTI ID = 0.0 > 2. < / RTI >

The relationship between the incident angle of the illumination light on the first light incidence surface and the exit angle relationship of the illumination light on the light exiting surface may be different from the incidence angle of the illumination light on the second light incidence surface and the exit angle relationship of the illumination light on the light exiting surface. For example, the illumination light proceeding rightward through the interior of the light guide plate 130 through the first light incidence surface may be emitted from the light guide plate 130 toward the observer's right eye view range by the output coupler 135. In addition, the illumination light proceeding inside the light guide plate 130 through the second light entrance surface to the left side can be emitted from the light guide plate 130 toward the left eye (EL) viewing area of the observer by the output coupler 135.

In this structure, when the incident angle of the illumination light incident on the first and second light incidence surfaces of the light guide plate 130 is different, the output angle of the illumination light emitted to the light exiting surface of the light guide plate 130 by the output coupler 135 is different. Therefore, by controlling the incident angles of the illumination light with the first and second beam deflectors 114a and 114b, it is possible to control the outgoing angle of the illumination light emitted to the light exit surface of the light guide plate 130. [ For example, as schematically shown in FIGS. 6A and 6B, the advancing angle of the light traveling inside the light guide plate 130 through the first input coupler 131a is adjusted by the first beam deflector 114a It can change. Thus, the exit angle of the illumination light emitted from the light exit surface of the light guide plate 130 can be adjusted by the first beam deflector 114a. Therefore, by using the first and second beam deflectors 114a and 114b, it becomes possible to steer the illumination light corresponding to the pupil position change of the observer.

The first and second input couplers 131a and 131b are disposed on both side surfaces 130a and 130b of the light guide plate 130 in FIG. 5, FIG. 6A, and FIG. 6B It is to be understood that the present invention is not limited thereto. A light guide plate having a very wide variety of structures can be used, and the light entrance surface of the illumination light and the position of the input coupler can be variously selected according to the structure of the light guide plate. Also, the position of the beam deflector may be changed according to the position of the light incidence surface. For example, Figs. 7 to 9 are sectional views exemplarily showing various other configurations of the beam deflector and the light guide plate of the backlight unit 100 shown in Fig. The structure of the light guide plate 130 described in FIGS. 5, 6A, and 6B and the structure of the light guide plate 130 described in FIGS. 7 to 9 will be described with reference to the backlight units 100 ', 100 " ).

7, an output coupler 135 is disposed on a front surface 130c of the light guide plate 130 and a first input coupler 131a may be disposed on a rear surface 130d of the light guide plate 130. FIG. Although not shown in FIG. 7 for the sake of convenience, the second input coupler 131b may be disposed on the back surface 130d of the light guide plate 130. FIG. For example, the first input coupler 131a may be partially disposed on the left edge region of the back surface 130d and the second input coupler 131b may be partially disposed on the right edge region of the back surface 130d. Accordingly, the first and second input couplers 131a and 131b and the output coupler 135 are disposed on the back surface 130d and the front surface 130c, which are two opposed surfaces of the light guide plate 130, respectively. The light incidence surface 130e of the light guide plate 130 on which the illumination light is incident may be formed on both side edge regions of the front surface 130c opposed to the first and second input couplers 131a and 131b. The output coupler 135 is not disposed on both side edge regions of the front surface 130c of the light guide plate 130 so that the light incident surface 130e can be positioned. That is, the output coupler 135 may be partially disposed in the center region of the front surface 130c of the light guide plate 130. [

In this case, the first and second beam deflectors 114a and 114b may be disposed opposite to the light incidence surface 130e located at both side edge regions of the front surface 130c of the light guide plate 130. [ Although a galvano mirror is illustrated as an example of the first beam deflector 114b in Fig. 7, an electro-wetting element or an acousto-optic element may be used in addition to the galvanometer mirror, or the first and second light sources 110a and 110b May be used. 7, only the first beam deflector 114a is shown for convenience, but the first light source 110a may be disposed opposite to the opposite side edge regions of the front surface 130c of the light guide plate 130. FIG. Although not shown in FIG. 7, the second beam deflector 114b and the second input coupler 131b are disposed at the right edge of the light guide plate 130 with the first beam deflector 114a and the first input coupler 131a, Can be arranged symmetrically. The configuration and operation of the first beam deflector 114a and the first input coupler 131a described below may be applied symmetrically to the second beam deflector 114b and the second input coupler 131b.

In this structure, the illumination light emitted from the first light source unit 110a may pass through the left edge region of the front surface 130c of the light guide plate 130 and enter the first input coupler 131a. The first input coupler 131a may be a diffractive optical element that diffracts and reflects the illumination light so that the illumination light advances inwardly into the light guide plate 130. [ For example, the first input coupler 131a may be a holographic grating that separates white light into red light, green light, and blue light components and diffracts and reflects them at different angles. The red light, the green light, and the blue light separated by the first input coupler 131a may travel inside the light guide plate 130 at different angles. The output coupler 135 may be a holographic grating configured to emit the color separated red light, green light, and blue light from the light guide plate 130 at the same angle. Accordingly, red light, green light, and blue light separated by the first input coupler 131a may be mixed with each other when the light is output from the light guide plate 130 by the output coupler 135, and may become white light again.

The first beam deflector 114a can adjust the incident angle of the illumination light incident on the first input coupler 131a. When the incident angle of the illumination light incident on the first input coupler 131a is changed, the angle at which the red light, the green light, and the blue light diffracted and reflected by the first input coupler 131a travels in the light guide plate 130 is different . Accordingly, the output angle of the illumination light emitted to the light output surface of the light guide plate 130 by the output coupler 135 is different. Therefore, by controlling the incident angle of the illumination light by using the first beam deflector 114a, it is possible to control the outgoing angle of the illumination light emitted to the light exit surface of the light guide plate 130. [

The structure of the light guide plate 130 shown in FIG. 8 is the same as the structure of the light guide plate 130 shown in FIG. 7, except that the first input coupler 131a is a photopolymer having a periodic refractive index distribution . For example, the first input coupler 131a can diffract and reflect red light, green light, and blue light at the same angle. Therefore, the white illumination light can proceed inside the light guide plate 130 without being separated by the first input coupler 131a and maintaining the properties of the white light.

The structure of the light guide plate 130 shown in FIG. 9 is the same as the structure of the light guide plate 130 shown in FIG. 8, but differs in that it further includes a color casting element 136 only. The output coupler 135 may have some wavelength dependence or chromatic aberration depending on its structure, in which case the white illumination light may be color separated. In order to prevent this, a color element 136 for making the illumination light separated by the output coupler 135 into white light may be disposed to face the light exit surface of the light guide plate 130. The coloring element 136 may be a diffractive optical element that diffracts and transmits red, green, and blue light that are separated in color and proceed at different angles, all proceeding at the same angle. The color element 136 may be further disposed on the light guide plate 130 shown in Fig.

7 to 9, the first input coupler 131a is disposed on the back surface 130d of the light guide plate 130 so as to face the light incidence surface 130e and diffracts and reflects the illumination light. However, It is not. For example, the light incident surface 130e is formed on the back surface 130d of the light guide plate 130 and the first input coupler 131a is directly disposed on the light incident surface 130e, which is the back surface 130d of the light guide plate 130 It is possible. In this case, the illumination light can be incident on the back surface 130d of the light guide plate 130, and the first input coupler 131a can diffract and transmit the illumination light. Alternatively, the first input coupler 131a may be disposed directly on the light incidence surface 130e, which is the front surface 130c of the light guide plate 130, and may diffract and transmit the illumination light.

10 is a block diagram schematically showing a configuration of a backlight unit 200 according to another embodiment. 10, the backlight unit 200 includes a light source 110 for providing illumination light, a light incident surface for receiving illumination light provided from the light source 110, and a light exit surface for emitting the incident illumination light. Input couplers 131a and 131b disposed on the light incident surfaces of the light guide plate 130 to guide the illumination light incident on the light incident surface into the light guide plate 130; An output coupler 135 for emitting the light to the outside of the light guide plate 130 and a color cast element 136 for converting the illumination light color separated by the output coupler 135 into white light.

The light source 110 includes a light source 111 for generating illumination light, a collimator 112 for converting the illumination light into a parallel beam, a beam expander 113 for increasing the beam diameter of the illumination light, and a light source for adjusting the angle of incidence of the illumination light incident on the light guide plate 130 A beam deflector 114 and a beam splitter 116 for dividing the illumination light into two. The illumination light can be divided by the beam splitter 116 into a first illumination light provided in a first view area (e.g., a right eye view area of an observer) and a second illumination light provided in a second view area (e.g., a left eye view area of an observer) . For example, the beam splitter 116 may be a semi-transmissive mirror that transmits half of the illumination light and reflects the other half. Alternatively, the beam splitter 116 may be a mirror system configured to reflect half of the illumination light in a first direction and reflect the other half of the illumination light in a second direction different from the first direction.

The first and second illumination lights separated by the beam splitter 116 can be incident on different areas of the light guide plate 130, respectively. The light guide plate 130 may include a first light incidence surface on which the first illumination light is incident and a second light incidence surface on which the second illumination light is incident. The input couplers 131a and 131b may include a first input coupler 131a and a second input coupler 131b to advance the first and second illumination lights into the light guide plate 130. [ As shown in FIG. 5, the first and second input couplers 131a and 131b may be disposed on the light incident surface of the light guide plate 130, respectively. The first and second input couplers 131a and 131b may be disposed on the surface of the light guide plate 130 opposite to the light incident surface of the light guide plate 130, as shown in FIG. According to the present embodiment, a single hologram image can be formed in the observer's left eye (EL) and right eye (ER) viewing ranges, respectively.

11 is a schematic diagram showing an exemplary configuration of the backlight unit 200 shown in FIG. 11, the first illumination light split by the beam splitter 116 can be reflected by the first mirror 117a and incident on the first light incidence surface 130e of the light guide plate 130. [ The first illumination light is emitted from the light guide plate 130 through the output coupler 135 and travels toward the first viewing area while proceeding to the interior of the light guide plate 130 by the first input coupler 131a. The second illumination light split by the beam splitter 116 can be reflected by the second mirror 117b and incident on the second light incidence surface 130f of the light guide plate 130. [ The second illumination light is emitted from the light guide plate 130 through the output coupler 135 and travels toward the second viewing area while proceeding to the interior of the light guide plate 130 by the second input coupler 131b. FIG. 11 exemplarily shows the structure of the light guide plate 130 shown in FIG. 7, but the structure shown in FIG. 5 may be applied.

The beam deflector 114 can control the traveling direction of the illumination light incident on the beam splitter 116 and thus can be incident on the first light incidence surface 130e and the second light incidence surface 130f of the light guide plate 130, The incident angle of the first illumination light and the second illumination light can be adjusted. Accordingly, the beam deflector 114 can simultaneously adjust the traveling directions of the first illumination light and the second illumination light emitted to the light exit surface of the light guide plate 130. [

The first illumination light and the second illumination light may be provided to the spatial light modulator 150 at the same time, but may alternatively be provided to the spatial light modulator 150 alternately. To this end, the backlight unit 200 may further include a first optical shutter 118a for transmitting / blocking the first illumination light and a second optical shutter 118b for transmitting / blocking the second illumination light. For example, while the first optical shutter 118a transmits the first illumination light, the second optical shutter 118b can block the second illumination light. Further, while the first optical shutter 118a blocks the first illumination light, the second optical shutter 118b can transmit the second illumination light. In this way, the first illumination light and the second illumination light can be alternately provided to the spatial light modulator 150 in turn. The first optical shutter 118a may be located anywhere in the optical path of the first illumination light between the beam splitter 116 and the first light incidence surface 130e and the second optical shutter 118b may be located in the optical path between the beam splitter 116 and the first light incidence surface 130e. 2 incident surface 130f of the second illumination light.

12 is a block diagram schematically showing the configuration of a backlight unit 200 'according to another embodiment. 12, the backlight unit 200 'shown in FIG. 12 is arranged so that the traveling direction of two illumination lights divided by the beam splitter 116 is divided into two beam deflectors 114a, 114b in that they can be controlled independently of each other. For example, the light source unit 110 includes a light source 111 for generating illumination light, a collimator 112 for converting the illumination light into a parallel beam, a beam expander 113 for increasing the beam diameter of the illumination light, a beam splitter 116 for dividing the illumination light into two, And first and second beam deflectors 114a and 114b for respectively adjusting the traveling directions of the two illumination lights divided by the beam splitter 116. [ The remaining configuration of the backlight unit 200 'shown in FIG. 12 may be the same as that of the backlight unit 200 shown in FIG.

13 is a schematic view showing an exemplary configuration of the backlight unit 200 'shown in FIG. Referring to FIG. 13, the beam splitter 116 may divide the illumination light from the beam expander 113 into first illumination light and second illumination light. 13 shows that the mirror 117 is disposed between the beam expander 113 and the beam splitter 116 so that the optical path is bent. However, when the mirror 117 is removed and the beam splitter 116 is removed from the light source 111, May be formed in a straight line. The first illumination light and the second illumination light split by the beam splitter 116 can be incident on the first beam deflector 114a and the second beam deflector 114b, respectively. The first beam deflector 114a can adjust the incident angle of the first illumination light incident on the first light incidence surface 130e of the light guide plate 130. [ The second beam deflector 114b can adjust the incident angle of the second illumination light incident on the second light incidence surface 130f of the light guide plate 130. [ Therefore, the first and second beam deflectors 114a and 114b can independently adjust the traveling direction of the first illumination light and the second illumination light emitted to the light exit surface of the light guide plate 130, respectively.

FIG. 14 is a block diagram schematically showing a configuration of a backlight unit 300 according to another embodiment. Referring to FIG. 14, the backlight unit 300 includes a light source 110 for providing illumination light, a light incident surface for receiving illumination light provided from the light source 110, and a light exit surface for emitting the incident illumination light. An input coupler 131 disposed on the light incident surface of the light guide plate 130 and advancing the illumination light incident on the light incident surface into the light guide plate 130; An output coupler 135 for emitting the light to the outside of the light guide plate 130 and a color cast element 136 for converting the illumination light color separated by the output coupler 135 into white light.

The light source 110 includes a light source 111 for generating illumination light, a collimator 112 for converting the illumination light into a parallel beam, a beam expander 113 for increasing the beam diameter of the illumination light, And a switch 119 for adjusting the traveling direction of the illumination light so that the illumination light emitted from the light guide plate 130 is selectively provided in the first or second view area. For example, the switch 119 may be configured such that the illumination light is provided to the first view area while the right eye hologram image is formed, and the illumination light is provided to the second view area during the formation of the left eye hologram image, Can be alternately adjusted in two directions opposite to each other. The beam deflector 114 can finely adjust the incident angle of the illumination light corresponding to the change of the pupil position of the observer in the first view direction or the second view direction selected by the switch 119. [ Accordingly, the backlight unit 300 can provide the illumination light to two different viewports even with one light source unit 110 without the beam splitter 116.

FIG. 15 is a perspective view schematically showing a configuration of the holographic display device 1200 including the backlight unit 300 shown in FIG. Referring to FIG. 15, the holographic display device 1200 may include a backlight unit 300 and a spatial light modulator 150. The backlight unit 300 serves to provide illumination light to the spatial light modulator 150 and the spatial light modulator 150 functions to form a hologram pattern having interference fringes for modulating the illumination light. The illumination light is diffracted and modulated by the hologram pattern formed in the spatial light modulator 150, so that a hologram image can be formed at a predetermined spatial position. Although not shown in FIG. 15, the holographic display device 1200 may further include a gaze tracking unit 160 and a control unit 170 shown in FIG.

As shown in FIG. 15, the light source unit 110 may be disposed opposite to one edge of the light guide plate 130. The light incident surface of the light guide plate 130 and the input coupler 131 may be disposed on one edge of the light guide plate 130, which is opposed to the light source unit 110. For example, the light incident surface and the input coupler 131 may be disposed along the upper edge of the light guide plate 130, and the light source unit 110 may be disposed opposite the upper edge of the light guide plate 130. Here, assuming that the first viewing area (for example, the observer's right viewing area) and the second viewing area (for example, the left viewing area of the observer) are located at different positions in the horizontal direction, As shown in FIG. However, the position of the light source unit 110 is not limited thereto, and the position of the light source unit 110 may be selected differently depending on the characteristics of the output coupler 135. For example, the light source unit 110 may be disposed at a lower side edge, a left side edge, or a right side edge of the light guide plate 130.

The switch 119 can advance the illumination light to the right direction, for example, as indicated by the dotted arrow in Fig. 15, while the holographic display device 1200 forms the right eye hologram image. Then, the illumination light can be emitted to the observer's right eye view region by the output coupler 135 while proceeding in the right direction from the inside of the light guide plate 130. In addition, while the holographic display device 1200 forms the left eye hologram image, the illumination light can be advanced to the left as indicated by the solid arrow. Then, the illumination light can be emitted to the left eye (ER) field of view of the observer by the output coupler 135 while proceeding in the left direction inside the light guide plate 130. In this way, the switch 119 can be configured to serially alternately provide illumination light that is deflected by the beam deflector 114 to different view areas. The beam deflector 114 can finely adjust the incident angle of the illumination light corresponding to the change of the pupil position of the observer within the first view direction or the second view direction selected by the switch 119. [

However, if the operating angle range of the beam deflector 114 is very large, the switch 119 may be omitted and the beam deflector 114 may also adjust the traveling direction of the illumination light. For example, while the holographic display device 1200 forms a right eye hologram image, the beam deflector 114 may advance the illumination light to the right as indicated by the dotted arrow. At the same time, the beam deflector 114 can adjust the incident angle of the illumination light in accordance with the change of the pupil position of the observer in the right eye view region. Further, while the holographic display device 1200 forms the left eye hologram image, the beam deflector 114 can advance the illumination light in the left direction as indicated by the solid line arrow. At the same time, the beam deflector 114 can adjust the incident angle of the illumination light in accordance with the change of the pupil position of the observer in the left eye view region. In this manner, the beam deflector 114 can alternately provide illumination light alternately to different view areas, and finely adjust the incident angle of the illumination light corresponding to the change in the pupil position of the observer.

16 is a perspective view schematically showing the configuration of another holographic display device 1300. As shown in FIG. 16, the backlight unit 300 'of the holographic display device 1300 includes a plurality of light source cells 110a, 110b, and 110c of the holographic display device 1200 shown in FIG. 15 in that the light source unit 110 includes an array of a plurality of light source cells. And is different from the backlight unit 300. For example, the light source unit 110 may include a plurality of light source cells arranged along the upper side edge of the light guide plate 130. The light source 111, the collimator 112, the beam expander 113, the beam deflector 114, and the switch 119 may be disposed for each of the plurality of light source cells of the light source unit 110, respectively. The remaining configuration of the holographic display device 1300 shown in FIG. 16 may be the same as the holographic display device 1200 shown in FIG.

Up to now, an exemplary embodiment of a backlight unit for a holographic display device and a holographic display device including the same has been described and illustrated in the accompanying drawings to assist in understanding the present invention. It should be understood, however, that such embodiments are merely illustrative of the present invention and not limiting thereof. And it is to be understood that the invention is not limited to the details shown and described. Since various other modifications may occur to those of ordinary skill in the art.

100, 100 ', 200, 200', 300 ..... Backlight unit
110 ..... light source part 111 ..... light source
112 ..... collimator 113 ..... beam expander
114 ..... beam deflector 117 ..... mirror
118 ..... optical shutter 119 ..... switch
130 ..... Light guide plate 131 ..... Input coupler
135 ..... Output coupler 136 ..... Color cast elements
150 ..... spatial light modulator 160 ..... eye tracking unit
170 ..... controller
1000, 1100, 1200, 1300, 1400 ..... The holographic display device

Claims (25)

A light source unit for providing illumination light;
A transparent light guide plate having a light incident surface on which the illumination light provided by the light source unit is incident and a light output surface for emitting the incident illumination light;
An input coupler for guiding illumination light incident on the light incident surface of the light guide plate into the light guide plate; And
And an output coupler disposed on a light emitting surface of the light guide plate to emit the illumination light to the outside of the light guide plate,
Wherein the light source unit includes a beam deflector for adjusting an incident angle of illumination light incident on the light guide plate. The method according to claim 1,
Wherein the light source unit includes a first light source unit for providing first illumination light in a first view area and a second light source unit for providing second illumination light in a second view area different from the first view area,
Wherein the light incidence surface includes a first light incidence surface on which the first illumination light is incident and a second light incidence surface on which the second illumination light is incident,
Wherein the input coupler includes a first input coupler for advancing the first illumination light into the light guide plate and a second input coupler for advancing the second illumination light into the light guide plate. 3. The method of claim 2,
Wherein the first light incidence surface and the second light incidence surface are disposed on opposite sides of the light guide plate, the first light source portion is disposed to face the first light incidence surface, and the second light source portion is disposed on the second light incidence surface A backlight unit disposed opposite. 3. The method of claim 2,
Wherein the light guide plate is configured such that the first illumination light and the second illumination light are emitted through the same light exit surface, and the output coupler is configured such that the first illumination light and the second illumination light are emitted at different angles. 3. The method of claim 2,
The first light source unit includes:
A first light source for generating a first illumination light;
A first collimator for converting the first illumination light into a parallel beam;
A first beam expander for increasing a beam diameter of the first illumination light; And
And a first beam deflector for adjusting an incident angle of the first illumination light incident on the first light incidence surface. 6. The method of claim 5,
The second light source unit includes:
A second light source for generating a second illumination light;
A second collimator for converting the second illumination light into a parallel beam;
A second beam expander for increasing the beam diameter of the second illumination light; And
And a second beam deflector for adjusting the incident angle of the second illumination light incident on the second light incidence surface. The method according to claim 6,
Wherein the first and second light sources are configured to emit coherent white light. The method according to claim 1,
The light source unit includes:
A light source for generating illumination light;
A collimator for converting the illumination light into a parallel beam;
A beam expander for increasing the beam diameter of the illumination light to provide the beam deflector to the beam deflector; And
And a beam splitter for dividing the illumination light coming from the beam deflector into the first illumination light and the second illumination light. 9. The method of claim 8,
Wherein the light incidence surface includes a first light incidence surface on which the first illumination light is incident and a second light incidence surface on which the second illumination light is incident,
Wherein the input coupler includes a first input coupler for advancing the first illumination light into the light guide plate and a second input coupler for advancing the second illumination light into the light guide plate. 10. The method of claim 9,
Wherein the first light incidence surface and the second light incidence surface are disposed on opposite sides of the light guide plate, respectively. 10. The method of claim 9,
Wherein the light guide plate is configured such that the first illumination light and the second illumination light are emitted through the same light exit surface, and the output coupler is configured such that the first illumination light is emitted to the first view area and the second illumination light is emitted to the second view area To the backlight unit. The method according to claim 1,
The light source unit includes:
A light source for generating illumination light;
A collimator for converting the illumination light into a parallel beam;
A beam expander for increasing the beam diameter of the illumination light; And
And a beam splitter for dividing the illumination light from the beam expander into a first illumination light and a second illumination light. 13. The method of claim 12,
Wherein the beam deflector includes a first beam deflector for adjusting an incident angle of the first illumination light and a second beam deflector for adjusting an incident angle of the second illumination light,
Wherein the light incidence surface includes a first light incidence surface on which the first illumination light is incident and a second light incidence surface on which the second illumination light is incident,
Wherein the input coupler includes a first input coupler for advancing the first illumination light into the light guide plate and a second input coupler for advancing the second illumination light into the light guide plate. 14. The method of claim 13,
Wherein the first light incidence surface and the second light incidence surface are disposed on opposite sides of the light guide plate, respectively. 14. The method of claim 13,
Wherein the light guide plate is configured such that the first illumination light and the second illumination light are emitted through the same light exit surface, and the output coupler is configured such that the first illumination light is emitted to the first view area and the second illumination light is emitted to the second view area To the backlight unit. The method according to claim 1,
The light source unit includes:
A light source for generating illumination light;
A collimator for converting the illumination light into a parallel beam; And
And a beam expander for increasing the beam diameter of the illumination light to the beam deflector. 17. The method of claim 16,
Wherein the beam deflector is configured to alternately provide illumination light to the first and second viewing zones different from each other. 18. The method of claim 17,
Wherein the light incidence surface and the input coupler are disposed at one edge of the light guide plate, and the light source unit is disposed to face the light incidence surface of the light guide plate. 19. The method of claim 18,
Wherein the first and second viewing zones are located at different positions in a horizontal direction and the light source unit is disposed at an upper side edge or a lower side edge arranged in the vertical direction of the light guide plate. 17. The method of claim 16,
Wherein the light source unit further comprises a switch configured to momentarily alternately provide illumination light, which is deflected by the beam deflector, to different first and second view zones. The method according to claim 1,
Further comprising an achromatization element for converting the illumination light color separated by the output coupler into white light. The method according to claim 1,
Wherein the input coupler and the output coupler include a holographic grating having a diffraction pattern or a photopolymer having a periodic refractive index distribution. The method according to claim 1,
Wherein the input coupler and the output coupler are disposed on the first surface and the second surface, respectively, of the light guide plate, wherein the input coupler and the output coupler are disposed in an edge area of the first surface, Area of the backlight unit. A backlight unit according to any one of claims 1 to 23; And
And a spatial light modulator for modulating the illumination light provided by the backlight unit to form a holographic image. 25. The method of claim 24,
And a gaze tracking unit for tracking the pupil position of the observer,
Wherein the beam deflector adjusts the incident angle of the illumination light incident on the light guide plate in accordance with a change in the pupil position of the observer.

Images