Multi-image display apparatus providing holographic image

This applicationThe present application is a reissue application of U.S. Pat. No. 11,714,289, which was filed as U.S. patent application No. 16/683,643 on Nov. 14, 2019 and issued on Aug. 1, 2023, whichclaims priority from Korean Patent Application No. 10-2019-0019191, filed on Feb. 19, 2019, in the Korean Intellectual Property Office, thedisclosuredisclosuresof whichisareincorporated herein initstheirentirety by reference.

Example embodiments of the present disclosure relate to a multi-image display apparatus such as an augmented reality system, and more particularly, to a multi-image display apparatus providing a holographic image.

Recently, along with the development of electronic apparatuses and display apparatuses capable of implementing virtual reality (VR), interest in such apparatuses has increased. As a next step of VR, technology for implementing augmented reality (AR) and mixed reality (MR) has been researched.

Unlike VR that is based on a complete virtual world, AR is a display technique that shows the real world and overlapped (combined) virtual objects or information thereon, thereby further increasing the effect of reality. While VR is limitedly applied only to fields such as games or virtual experience, AR is advantageous in that it may be applied to various real environments. In particular, AR attracts the attention as next-generation display technology suitable for a ubiquitous environment or an Internet of things (IoT) environment. AR may be an example of MR in that it shows a mixture of the real world and additional information (virtual world).

One or more example embodiments provide a multi-image display apparatus providing a holographic image.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of example embodiments.

According to an aspect of an example embodiment, there is provided a multi-image display apparatus including a light source configured to emit a first wavelength light, a second wavelength light, and a third wavelength light, a spatial light modulator configured to modulate each of the first wavelength light, the second wavelength light, and the third wavelength light to form a first image including a first color holographic image, a second color holographic image, and a third color holographic image, a polarization selective lens configured to focus the first image having only a first polarization component and transmit a second image having only a second polarization component without refraction, the second image being provided to the polarization selective lens along a different path from the first image, wherein chromatic aberration of the polarization selective lens is offset by adjusting a depth of the first color holographic image, a depth of the second color holographic image, and a depth of the third color holographic image.

The light source may include a first light source configured to emit the first wavelength light, a second light source configured to emit the second wavelength light, and a third light source configured to emit the third wavelength light.

The multi-image display apparatus may further include a controller configured to provide first hologram data to the spatial light modulator while the first light source emits the first wavelength light, provide second hologram data to the spatial light modulator while the second light source emits the second wavelength light, and provide third hologram data to the spatial light modulator while the third light source emits the third wavelength light.

The polarization selective lens may have a first focal distance with respect to the first wavelength light, a second focal distance that is greater than the first focal distance with respect to the second wavelength light, and a third focal distance that is greater than the second focal distance with respect to the third wavelength light, and the controller may be further configured to adjust depth information of the first hologram data, the second hologram data, and the third hologram data based on the first focal distance, the second focal distance, and the third focal distance, respectively.

The controller may be further configured to adjust the depth information of the first hologram data such that the first color holographic image has a depth in which the first color holographic image is closer to the polarization selective lens than the second color holographic image by a difference between the second focal distance and the first focal distance, and adjust the depth information of the third hologram data such that the third color holographic image has a depth in which the third color holographic image is farther from the polarization selective lens than the second color holographic image by a difference between the third focal distance and the second focal distance.

The multi-image display apparatus may further include a controller configured to provide hologram data to the spatial light modulator while the first light source, the second light source, and the third light source simultaneously emit the first wavelength light, the second wavelength light, and the third wavelength light, respectively.

The polarization selective lens may have a first focal distance with respect to the first wavelength light, a second focal distance that is greater than the first focal distance with respect to the second wavelength light, and a third focal distance that is greater than the second focal distance with respect to the third wavelength light, and the controller may be further configured to adjust depth information of the hologram data based on the first focal distance, the second focal distance, and the third focal distance, respectively.

The controller may be further configured to adjust the depth information of the hologram data with respect to the first color holographic image such that the first color holographic image has a depth in which the first color holographic image is closer to the polarization selective lens than the second color holographic image by a difference between the second focal distance and the first focal distance, and adjust the depth information of hologram data with respect to the third color holographic image such that the third color holographic image has a depth in which the third color holographic image is farther from the polarization selective lens than the second color holographic image by a difference between the third focal distance and the second focal distance.

The multi-image display apparatus may further include a first polarization plate configured to transmit only the second polarization component from the second image, a beam splitter disposed on an optical path between the first polarization plate and the polarization selective lens, and a ¼ wavelength plate disposed between the beam splitter and the light source.

The beam splitter may be disposed on an optical path between the light source and the spatial light modulator, and the spatial light modulator may include a reflective-type light modulator configured to modulate reflected light.

The light source may include a laser light source configured to emit light having a first linear polarization component, and the first polarization component may include a first circular polarization component, and the second polarization component may include a second circular polarization component having a rotational direction opposite to a rotational direction of the first circular polarization component.

The light source may include a light-emitting diode configured to emit non-polarized light, the multi-image display apparatus may further include a second polarization plate disposed between the light source and the ¼ wavelength plate, and configured to transmit only the first linear polarization component, and the first polarization component may include a first circular polarization component, and the second polarization component may include a second circular polarization component having a rotational direction opposite to a rotational direction of the first circular polarization component.

The beam splitter may include a half-transparent mirror configured to reflect a portion of incident light and transmit a remaining portion of the incident light.

The beam splitter may include a polarization selective mirror configured to reflect light having the first circular polarization component and transmit light having the second circular polarization component.

The multi-image display apparatus may further include a first linear polarization plate configured to transmit only a first linear polarization component from the second image, a beam splitter on an optical path between the first linear polarization plate and the polarization selective lens, a first ¼ wavelength plate between the beam splitter and the spatial light modulator, and a second ¼ wavelength plate between the beam splitter and the polarization selective lens, wherein the first polarization component may include a first circular polarization component, and the second polarization component may include a second circular polarization component having a rotational direction opposite to a rotational direction of the first circular polarization component.

The beam splitter may be disposed on an optical path between the light source and the spatial light modulator, and the spatial light modulator may include a reflective-type light modulator configured to modulate reflected light.

The light source may include a laser light source configured to emit light having the first linear polarization component.

The light source may include a light-emitting diode configured to emit non-polarized light, and the multi-image display apparatus may further include a second linear polarization plate disposed between the light source and the beam splitter and configured to transmit only the first linear polarization component.

The beam splitter may include a polarization selective mirror configured to transmit light having the first linear polarization component and reflect light having a second linear polarization component that is orthogonal to the first linear polarization component.

The multi-image display apparatus may further include a linear polarization plate configured to transmit only a first linear polarization component from the second image, a beam splitter disposed on an optical path between the linear polarization plate and the polarization selective lens, and a ¼ wavelength plate disposed between the beam splitter and the polarization selective lens, wherein the first polarization component may include a first circular polarization component, and the second polarization component may include a second circular polarization component having a rotational direction opposite to a rotational direction of the first circular polarization component.

The spatial light modulator may be disposed on an optical path between the light source and the beam splitter, and the spatial light modulator may include a transmissive-type light modulator configured to modulate transmitted light.

The light source may include a laser light source configured to emit light having a second linear polarization component that is orthogonal to the first linear polarization component.

The multi-image display apparatus may further include a polarization plate configured to transmit only the second polarization component from the second image, a beam splitter disposed on an optical path between the polarization plate and the polarization selective lens, and a ¼ wavelength plate disposed between the spatial light modulator and the beam splitter, wherein the spatial light modulator may include a transmissive-type light modulator disposed between the light source and the beam splitter and configured to modulate transmitted light, and wherein the light source may include a laser light source configured to emit light having a second linear polarization component that is orthogonal to a first linear polarization component.

The multi-image display apparatus may further include a first beam splitter disposed between the light source and the spatial light modulator, a ¼ wavelength plate disposed between the first beam splitter and the light source, a polarization plate configured to transmit only the second polarization component from the second image, and a second beam splitter disposed on an optical path between the polarization plate and the polarization selective lens, wherein the second beam splitter is configured to reflect light having the first polarization component from the first beam splitter and transmit light having the second polarization component from the polarization plate.

The spatial light modulator may include a reflective-type light modulator configured to modulate reflected light.

The light source may include a laser light source configured to emit light having a first linear polarization component, and the first polarization component may include a first circular polarization component, and the second polarization component may include a second circular polarization component having a rotational direction opposite to a rotational direction of the first circular polarization component.

According to another aspect of an example embodiment, there is provided a multi-image display apparatus including a light source configured to emit a first wavelength light, a second wavelength light, and a third wavelength light, a spatial light modulator configured to modulate the first wavelength light, the second wavelength light, and the third wavelength light to form a first image including a first color holographic image, a second color holographic image, and a third color holographic image, a controller configured to provide to the spatial light modulator first hologram data corresponding to the first wavelength light, a second hologram data corresponding to the second wavelength light, and a third hologram data corresponding to the third wavelength light, and a polarization selective lens configured to focus the first image having a first polarization component and transmit a second image having a second polarization component without refraction, wherein the controller is further configured to offset chromatic aberration of the polarization selective lens by adjusting a depth of the first hologram data, a depth of the second hologram data, and a depth of the third hologram data such that the first color holographic image, the second color holographic image, and the third color holographic image are focused on a same image plane.

The polarization selective lens may have a first focal distance with respect to the first wavelength light, a second focal distance that is greater than the first focal distance with respect to the second wavelength light, and a third focal distance that is greater than the second focal distance with respect to the third wavelength light, and the controller may be further configured to adjust depth information of the first hologram data, the second hologram data, and the third hologram data based on the first focal distance, the second focal distance, and the third focal distance, respectively.

The polarization selective lens may include two geometric phase lenses and a polarization conversion plate disposed between the two geometric phase lenses, wherein each of the two geometric phase lenses may be configured to operate as convex lens or concave lens based on a polarization component of incident light.

Hereinafter, a multi-image display apparatus providing a holographic image will be described in detail with reference to the accompanying drawings. In the drawings hereinafter, like reference numerals refer to like elements, and a size of each of components in the drawings may be exaggerated for clarity and convenience of explanation. In addition, example embodiments described hereinafter are only examples and various modifications may be possible based on the example embodiments.

Also, in layer structures described hereinafter, an expression, such as “above” or “on,” may denote not only that an element is directly above/below/left to/right to another element by contacting the other element, but also that an element is indirectly above/below/left to/right to another element without contacting the other element. Terms such as “comprise” and/or “comprising” may be construed to denote a constituent element, but may not be construed to exclude the existence of or a possibility of addition of another constituent element. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

1 FIG. 1 FIG. 100 100 110 111 112 113 120 114 130 140 is a schematic view illustrating a configuration of a multi-image display apparatusaccording to an example embodiment. Referring to, the multi-image display apparatusaccording to an example embodiment may include a light source, a collimating lens, a ¼ wavelength plate, a beam splitter, a spatial light modulator, a circular polarization plate, a polarization selective lens, and a controller.

110 120 140 111 110 110 111 110 110 110 110 110 110 110 The light source, the spatial light modulator, and the controllermay perform a function of a holographic display apparatus for reproducing a holographic image. Also, the collimating lensmay perform a function of making light emitted from the light sourceinto parallel light. When the parallel light is directly emitted from the light source, the collimating lensmay be omitted. In order to provide a color holographic image, the light sourcemay include a red light sourceR that emits light in a red wavelength band, a green light sourceG that emits light in a green wavelength band, and a blue light sourceB that emits light in a blue wavelength band. Also, the light sourcemay be a coherent light source emitting coherent light. In order to provide light having relatively high coherence, for example, a laser diode (LD) may be used as the light source. In particular, the light sourcemay include a polarization laser emitting light linearly polarized in a specific direction.

140 110 120 140 120 120 140 120 120 120 The controllermay control operations of the light sourceand the spatial light modulator. Also, the controllermay be an image signal processing device configured to provide hologram data containing information about a holographic image to be reproduced to the spatial light modulator. The spatial light modulatormay form a hologram pattern for diffracting and modulating incident light based on the hologram data provided from the controller. The spatial light modulatormay be any one of a phase modulator configured to perform only phase modulation, an amplitude modulator configured to perform only amplitude modulation, and a complex modulator configured to perform both phase modulation and amplitude modulation. The spatial light modulatormay be a reflected light modulator configured to modulate incident light by reflecting the incident light. For example, the spatial light modulatormay include a digital micro-mirror device (DMD), liquid crystal on silicon (LCoS), or a semiconductor modulator.

112 113 114 110 120 130 100 The ¼ wavelength plate, the beam splitter, and the circular polarization platemay be included in an optical system configured to guide a first image that is a holographic image reproduced by the light sourceand the spatial light modulator, and a second image that is an external image containing an actual external scene of a real world to the polarization selective lens. Then, a user may view the holographic image containing virtual reality or virtual information together with a background subject of the real world facing the user. Thus, the multi-image display apparatusaccording to the example embodiment may be implemented to realize augmented reality (AR) or mixed reality (MR). In this case, the multi-image display apparatus may be a near-eye AR display apparatus.

130 130 The polarization selective lensmay be configured to focus incident light or transmit the incident light without refraction, based on a polarization state of the incident light. For example, the polarization selective lensmay focus light of a first circular polarization component having a first rotational direction, and may intactly transmit light of a second circular polarization component having a second rotational direction which is opposite to the first rotational direction without any change.

130 130 100 130 130 130 130 130 130 130 130 130 130 130 130 130 130 130 130 130 130 2 3 FIGS.and 1 FIG. 2 3 FIGS.and The polarization selective lensmay be realized in various manners. For example,are schematic cross-sectional views illustrating an example configuration and operation of the polarization selective lensof the multi-image display apparatusillustrated in. Referring to, the polarization selective lensmay include two identical geometric phase lensesa andc and a polarization conversion plateb between the two identical geometric phase lensesa andc. The geometric phase lensesa andc are optical devices operating as convex lenses or concave lenses, based on a polarization characteristic of incident light. For example, the geometric phase lensesa andc may operate as convex lenses having a focal distance f with respect to light having a first circular polarization component and may operate as concave lenses having the focal distance f with respect to light having a second circular polarization component. Also, the geometric phase lensesa andc may change a polarization direction of transmitted light to the opposite direction. The polarization conversion plateb may operate to intactly transmit the light having the first circular polarization component and convert the light having the second circular polarization component into the light having the first circular polarization component. The polarization conversion plateb may be formed to be very thin, and thus, the polarization conversion plateb may be bonded between the two geometric phase lensesa andc to form the polarization selective lens.

10 130 10 130 10 10 130 10 130 130 130 130 130 130 10 130 130 10 2 FIG. When a first image Lhaving the first circular polarization component is incident on the polarization selective lens, the first image Lmay pass through the geometric phase lensa acting as a convex lens, and a polarization state of the first image Lmay be changed to the second circular polarization component, as illustrated in. Then, the first image Lmay have the first circular polarization component again, by passing through the polarization conversion plateb that converts polarization of light having the second circular polarization component. Then, the first image Lpass through the geometric phase lensc acting as a convex lens. Since the polarization conversion plateb is very thin, the two geometric phase lensesa andc of the polarization selective lenssubstantially are adhered to each other. When two convex lenses adhere to each other, the focal distance reduces by half, and thus, the polarization selective lensmay operate as the convex lens having half of a focal distance with respect to the first image Lhaving the first circular polarization component than a focal distance of each of the geometric phase lensesa andc, with respect to the first image Lhaving the first circular polarization component.

20 130 20 130 20 20 130 20 130 20 20 20 130 Also, when a second image Lhaving the second circular polarization component is incident on the polarization selective lens, the second image Lmay pass through the geometric phase lensa acting as a concave lens, and a polarization state of the second image Lis changed to the first circular polarization component. The second image Lthat may have the first circular polarization component may maintain the first circular polarization component by passing through the polarization conversion plateb which intactly transmits light having the first circular polarization component. Then, the second image Lmay pass through the geometric phase lensc acting as a convex lens. Consequently, since the second image Lpasses through each of the concave lens and the convex lens once, the concave lens and the convex lens having the same focal distance, no optical effect may apply to the second image L. Accordingly, the second image Lhaving the second circular polarization component may pass through the polarization selective lenswithout distortion.

130 130 2 3 FIGS.and The polarization selective lensmay have other configurations than the configuration described in. For example, the polarization selective lensmay be configured by singularly using a geometric phase lens, a meta lens, a double refraction lens, a diffraction lens, etc., which have artificially designed minute diffractive patterns, or may be configured by combining at least two thereof.

130 110 120 130 10 160 20 130 20 160 130 10 110 120 2 3 FIGS.and 1 FIG. When the polarization selective lensdescribed inis used, and when the first image reproduced by the light sourceand the spatial light modulatorhas the first circular polarization component, the polarization selective lensmay provide the first image Lto a user's eye, as shown in, by focusing the first image. Also, when the second image L, which is an image of the real world, has the second circular polarization component, the polarization selective lensmay intactly provide the second image Lto the user's eyewithout distortion. Then, the polarization selective lensmay intactly transmit the second image that is an image of the real world and may enlarge only the first image Lreproduced by the light sourceand the spatial light modulator, thereby increasing only an angle of view for the virtual image without distorting the image of the real world.

112 113 114 10 20 10 112 110 113 110 111 112 110 111 112 110 1 FIG. To this end, the ¼ wavelength plate, the beam splitter, and the circular polarization platemay be configured to allow the first image Lto have only the first circular polarization component and allow the second image Lfrom a different path from the first image Lto have only the second circular polarization component. For example, the ¼ wavelength platemay be disposed on an optical path between the light sourceand the beam splitterand may delay a phase of light from the light sourceby a ¼ wavelength, in order to convert linearly polarized light into circularly polarized light or convert the circularly polarized light into the linearly polarized light.illustrates that the collimating lensis disposed ahead of the ¼ wavelength plateand closer to the light source. However, the location of the collimating lensand the ¼ wavelength platemay be the opposite. Also, the light sourcemay include a polarization laser emitting light linearly polarized in a first direction.

114 130 114 113 114 130 113 10 20 110 120 113 113 110 120 The circular polarization platemay be disposed in front of a user to face the polarization selective lens. The circular polarization platemay be configured to block the light having the first circular polarization component and transmit only the light having the second circular polarization component. The beam splittermay be disposed on an optical path between the circular polarization plateand the polarization selective lens. In particular, the beam splittermay be disposed at a point at which an optical path of the first image Land an optical path of the second image Lcross each other. The light sourceand the spatial light modulatormay be disposed at both sides of the beam splitterto face each other. In other words, the beam splittermay be disposed on the optical path between the light sourceand the spatial light modulator.

1 110 1 112 1 113 120 1 120 1 120 1 120 1 113 113 130 113 113 In this configuration, light Lemitted from the light sourcemay have a first linear polarization component linearly polarized in a first direction. Also, the light Lhaving the first linear polarization component may have the second circular polarization component by passing through the ¼ wavelength plate. Thereafter, the light Lmay pass through the beam splitterand may be normally incident on a surface of the spatial light modulator. Then, the light Lmay be reflected by the spatial light modulatorand may have a travel direction that is changed by 180 degrees. The light Lreflected by the spatial light modulatorto travel in the opposite direction may have a polarization direction that is changed to an opposite direction, thereby having the second circular polarization component. Also, the light Lmay be modulated by the spatial light modulatorto contain a hologram image. Thereafter, the light Lmay be incident on the beam splitterat an angle again and reflected by the beam splitterin a direction of 90 degrees and may reach the polarization selective lenswhile having the first circular polarization component. The beam splittermay include a half-transparent mirror simply reflecting a portion of incident light and transmitting the other portion of the incident light. The beam splittermay include a polarization selective mirror reflecting the light having the first circular polarization component and transmitting the light having the second circular polarization component.

2 114 2 113 130 10 110 120 130 20 130 10 130 20 130 Light Lfrom the outside may pass through the circular polarization plateand may have only the second circular polarization component. The light Lhaving the second circular polarization component may pass through the beam splitterand reach the polarization selective lens. Thus, the first image Lreproduced by the light sourceand the spatial light modulatormay reach the polarization selective lenswhile having the first circular polarization component and the second image Lthat is the image of the real world may reach the polarization selective lenswhile having the second circular polarization component. Then, the first image Lmay be focused by the polarization selective lensand the second image Lmay pass through the polarization selective lenswithout distortion.

130 160 10 100 10 100 According to the example embodiment, the polarization selective lensmay be disposed in front of the user's eyeand may enlarge only the first image L, and an angle of view of the multi-image display apparatuswith respect to the first image Lmay be increased. Also, the multi-image display apparatusmay provide the holographic image having a three-dimensional effect together with an actual external scene, and thus, a more realistic AR experience may be provided.

130 130 130 130 130 130 1 2 1 3 2 130 130 130 130 4 FIG. 4 FIG. Meanwhile, in a situation in which paraxial approximation is applied, multiplication of wavelengths and focal distances of lights passing through the geometric phase lensesa andc may be constant. In other words, red light having the longest wavelength is focused at a shortest distance and blue light having the shortest wavelength is focused at a longest distance.is an example view illustrating a change in a focal distance of the geometric phase lensesa andc based on a wavelength of incident light. As illustrated in, the geometric phase lensesa andc may have a focal distance fwith respect to red light R, a focal distance f, which is greater than the focal distance f, with respect to green light G, and a focal distance f, which is greater than the focal distance f, with respect to blue light B. For example, when the focal distance of the geometric phase lensesa andc with respect to the red light R is about 37.417 mm, the focal distance with respect to the green light G may be about 44.705 mm and the focal distance with respect to the blue light B may be about 50.618 mm. For example, when the focal distance of the geometric phase lensesa andc with respect to the red light R is about 41.607 mm, the focal distance with respect to the green light G may be about 49.705 mm and the focal distance with respect to the blue light B may be about 56.275 mm.

130 130 130 130 130 130 130 The second image from the actual external scene may pass through each of the geometric phase lensesa andc in a different circular polarization state, and thus, may obtain an effect of each of a concave lens and a convex lens. Thus, the second image from the actual external scene may be delivered to the user with corrected chromatic aberration by passing through the two geometric phase lensesa andc. However, the first image, which is the holographic image, may obtain two times the effect of the convex lens by passing through the two geometric phase lensesa andc. Thus, the first image may be delivered to the user with the chromatic aberration increased by two times. Consequently, the polarization selective lensmay have a great chromatic aberration with respect to the first image and may not have a chromatic aberration with respect to the second image.

120 130 130 120 According to the example embodiment, depths of a red holographic image, a green holographic image, and a blue holographic image, which are reproduced by the spatial light modulator, may be adjusted in advance, and thus, the chromatic aberration generated when the holographic images are delivered to the user may be compensated for. A color holographic image of one frame may have three color components having the same depth, that is, a red holographic image, a green holographic image, and a blue holographic image. However, since a focal distance of the polarization selective lenswith respect to the first image varies based on the wavelength, when the chromatic aberration is not compensated for, the red holographic image, the green holographic image, and the blue holographic image delivered to the user may have different depths. Thus, the chromatic aberration of the polarization selective lensmay be offset by adjusting in advance the depth of the red holographic image, the depth of the green holographic image, and the depth of the blue holographic image by using the spatial light modulator.

5 5 FIGS.A throughC 1 FIG. 5 5 FIGS.A throughC 100 100 140 120 110 120 110 120 110 140 130 For example,are schematic views illustrating an operation of the multi-image display apparatusillustrated in. Referring to, the multi-image display apparatusmay sequentially reproduce a red holographic image, a green holographic image, and a blue holographic image at different times from one another. The controllermay be configured to provide hologram data related to the red holographic image to the spatial light modulator, while the red light sourceR emits red light, provide hologram data related to the green holographic image to the spatial light modulator, while the green light sourceG emits green light, and provide hologram data related to the blue holographic image to the spatial light modulator, while the blue light sourceB emits blue light. In this process, the controllermay change depth information of the hologram data related to the red holographic image, depth information of the hologram data related to the green holographic image, and depth information of the hologram data related to the blue holographic image, in order to offset the chromatic aberration of the polarization selective lens.

5 FIG.A 140 110 110 110 140 120 120 140 120 140 1 130 140 1 130 130 First, referring to, for a first period of time, the controllermay turn on only the red light sourceR and turn off the remaining green light sourceG and blue light sourceB. Also, the controllermay provide the hologram data related to the red holographic image to the spatial light modulator. The spatial light modulatormay form a hologram pattern for diffracting and modulating incident light based on the hologram data provided from the controller. Then, the red light may be reflected and diffracted by the spatial light modulatorso that the red holographic image R may be reproduced. The controllermay adjust a depth in which the red holographic image R is reproduced, by taking into account a focal distance fof the polarization selective lenswith respect to the red light. For example, the controllermay change the depth information of the hologram data such that the red holographic image R is reproduced in a location farther away than the focal distance fof the polarization selective lensin a front direction of the polarization selective lens. Then, a user may view an enlarged virtual image of the red holographic image R on an image plane IP at a certain distance from the user.

5 FIG.B 140 110 110 110 140 120 120 140 2 130 140 2 130 130 Next, referring to, for a second period of time, after the first period of time, the controllermay turn on only the green light sourceG and turn off the remaining red light sourceR and blue light sourceB. Also, the controllermay provide the hologram data related to the green holographic image to the spatial light modulator. Then, the green light may be reflected and diffracted by the spatial light modulatorso that the green holographic image G may be reproduced. The controllermay adjust a depth in which the green holographic image G is reproduced, by taking into account a focal distance fof the polarization selective lenswith respect to the green light. For example, the controllermay change the depth information of the hologram data such that the green holographic image G is reproduced in a location farther away than the focal distance fof the polarization selective lensin a front direction of the polarization selective lens. Then, the user may view an enlarged virtual image of the green holographic image G on the image plane IP distanced from the user by a certain distance.

5 FIG.C 140 110 110 110 140 120 120 140 3 130 140 3 130 130 Next, referring to, for a third period of time, after the second period of time, the controllermay turn on only the blue light sourceB and turn off the remaining red light sourceR and green light sourceG. Also, the controllermay provide the hologram data related to the blue holographic image to the spatial light modulator. Then, the blue light may be reflected and diffracted by the spatial light modulatorso that the blue holographic image B may be reproduced. The controllermay adjust a depth in which the blue holographic image B is reproduced, by taking into account a focal distance fof the polarization selective lenswith respect to the blue light. For example, the controllermay change the depth information of the hologram data such that the blue holographic image B is reproduced in a location farther away than the focal distance fof the polarization selective lensin a front direction of the polarization selective lens. Then, the user may view an enlarged virtual image of the blue holographic image B on the image plane IP distanced from the user by a certain distance.

130 As a result, the user may view that the enlarged virtual image of the red holographic image R, the enlarged virtual image of the green holographic image G, and the enlarged virtual image of the blue holographic image B are located on the same image plane IP. Thus, the user may not experience the chromatic aberration of the polarization selective lens. Also, when the hologram images of one frame are rapidly reproduced by allowing the first through third period of times to be very limited, the user may view a complete color holographic image.

130 140 As shown above, hologram image of each color may be reproduced at a location farther away than the focal distance of the polarization selective lenswith respect to each corresponding color. However, example embodiments are not limited thereto, and the location at which the hologram image of each color is reproduced may vary based on a depth in which each enlarged virtual image is formed. For example, when a distance between the user and the image plane IP is changed, the location at which the hologram image of each color is reproduced may be changed. In this case, the controllermay change the depth information of the red holographic image R and the depth information of the blue holographic image B based on the green holographic image G based on the change in the distance between the user and the image plane IP.

140 130 1 130 2 130 140 130 3 130 2 130 For example, the controllermay adjust the depth information of the hologram data related to the red holographic image R, such that the red holographic image R has a depth in which the red holographic image R is closer to the polarization selective lensthan the green holographic image G by a difference between the focal distance fof the polarization selective lenswith respect to the red light and the focal distance fof the polarization selective lenswith respect to the green light. Also, the controllermay adjust the depth information of the hologram data related to the blue holographic image B, such that the blue holographic image B has a depth in which the blue holographic image B is farther from the polarization selective lensthan the green holographic image G by a difference between the focal distance fof the polarization selective lenswith respect to the blue light and the focal distance fof the polarization selective lenswith respect to the green light.

5 5 FIGS.A throughC 140 110 110 110 140 120 140 Referring to, the red holographic image R, the green holographic image G, and the blue holographic image B are time-sequentially reproduced, but example embodiments are not limited thereto. For example, the controllermay simultaneously turn on the red light sourceR, the green light sourceG, and the blue light sourceB to simultaneously emit the red light, the green light, and the blue light. Also, the controllermay provide holographic data in which the hologram data related to the red holographic image R, the hologram data related to the green holographic image G, and the hologram data related to the blue holographic image B are combined to the spatial light modulator. Also in this case, under the same principle as described above, the controllermay adjust the depth information of the hologram data related to the red holographic image R, the depth information of the hologram data related to the green holographic image G, and the depth information of the hologram data related to the blue holographic image B.

100 200 200 110 120 114 130 113 110 120 114 130 112 110 113 115 110 112 111 110 115 140 110 120 1 FIG. 6 FIG. 6 FIG. Meanwhile, multi-image display apparatuses for providing the holographic image based on various configurations may be realized, in addition to the multi-image display apparatusillustrated in.is a schematic view illustrating a configuration of a multi-image display apparatusaccording to an example embodiment. Referring to, the multi-image display apparatusaccording to an example embodiment may include the light sourceand the spatial light modulatordisposed to face each other in a first direction, the circular polarization plateand the polarization selective lensdisposed to face each other in a second direction, the beam splitterdisposed at a point in which an optical path between the light sourceand the spatial light modulatorcrosses an optical path between the circular polarization plateand the polarization selective lens, the ¼ wavelength platebetween the light sourceand the beam splitter, a linear polarization platebetween the light sourceand the ¼ wavelength plate, the collimating lensbetween the light sourceand the linear polarization plate, and the controllerconfigured to control operations of the light sourceand the spatial light modulator.

200 100 115 110 112 115 110 110 115 200 100 6 FIG. 1 FIG. 1 FIG. The multi-image display apparatusillustrated inmay have substantially the same structure as the multi-image display apparatusillustrated in, and may further include the linear polarization platedisposed between the light sourceand the ¼ wavelength plate. The linear polarization platemay transmit only light having a first linear polarization component and may block light having a second linear polarization component orthogonal to the first linear polarization component. According to an example embodiment, the light sourcemay include a non-polarization laser, rather than a polarization laser. Light emitted from the light sourcemay be non-polarized light and may have the first linear polarization component by passing through the linear polarization plate. Other configurations and operations of the multi-image display apparatusmay be the same as those of the multi-image display apparatusdescribed with reference to.

110 120 110 110 200 115 110 Also, according to an example embodiment, the light sourcemay be a light-emitting diode (LED). The LED may have less spatial coherence than a laser. However, when light has at least a certain degree of spatial coherence, the light may be sufficiently diffracted and modulated by the spatial light modulator. When the light sourceis an LED, non-polarized light is emitted from the light source, and thus, the multi-image display apparatusmay include the linear polarization plate. Any light sourcesemitting light having spatial coherence may be used, in addition to the LED.

7 FIG. 7 FIG. 300 300 110 120 115 130 113 110 120 115 130 112 113 120 112 113 130 111 110 113 140 110 120 is a schematic view illustrating a configuration of a multi-image display apparatusaccording to an example embodiment. Referring to, the multi-image display apparatusaccording to an example embodiment may include the light sourceand the spatial light modulatordisposed to face each other in a first direction, the linear polarization plateand the polarization selective lensdisposed to face each other in a second direction, the beam splitterdisposed at a point in which an optical path between the light sourceand the spatial light modulatorcrosses an optical path between the linear polarization plateand the polarization selective lens, a first ¼ wavelength platea between the beam splitterand the spatial light modulator, a second ¼ wavelength plateb between the beam splitterand the polarization selective lens, the collimating lensbetween the light sourceand the beam splitter, and the controllerconfigured to control operations of the light sourceand the spatial light modulator.

110 1 110 1 110 113 112 1 1 120 1 120 120 1 1 112 1 113 112 1 130 1 The light sourcemay include a polarization laser. For example, light Lemitted from the light sourcemay have only a first linear polarization component. The Lhaving the first linear polarization component emitted from the light sourcemay pass through the beam splitterand then through the first ¼ wavelength platea so as to be changed to the light Lhaving a second circular polarization component. Then, the light Lmay be normally incident on the spatial light modulator. The light Lnormally incident on the spatial light modulatormay be reflected by the spatial light modulatorto have a travel direction which is changed to an opposite direction by 180 degrees. Due to the change in the travel direction, the light Lmay have a first circular polarization component. The light Lhaving the first circular polarization component may pass through the first ¼ wavelength platea again to have a second linear polarization component. Thereafter, the light Lmay be reflected by the beam splitterat an angle of about 90 degrees and may pass through the second ¼ wavelength plateb to have the first circular polarization component. Finally, the light Lmay be incident on the polarization selective lensin a state in which the light Lhas the first circular polarization component.

2 115 115 2 115 2 112 113 2 112 2 130 2 Meanwhile, light Lfrom the actual external scene may pass through the linear polarization plate. The linear polarization platemay transmit only light having the first linear polarization component and may block light having the second linear polarization component orthogonal to the first linear polarization component. Thus, the light Lpassing through the linear polarization platemay have the first linear polarization component. Thereafter, the light Lmay be incident on the second ¼ wavelength plateb by passing through the beam splitter. The light Lmay have the second circular polarization component by passing through the second ¼ wavelength plateb. Finally, the light Lmay be incident on the polarization selective lensin a state in which the light Lhas the second circular polarization component.

113 113 The beam splittermay include a half-transparent mirror reflecting a portion of incident light and transmitting the other portion of the incident light. The beam splittermay include a polarization selective mirror transmitting the light having the first linear polarization component and reflecting the light having the second linear polarization component.

8 FIG. 8 FIG. 8 FIG. 400 400 110 120 115 130 113 110 120 115 130 112 113 120 112 113 130 111 110 113 115 110 113 140 110 120 111 115 110 111 115 is a schematic view illustrating a configuration of a multi-image display apparatusaccording to an example embodiment. Referring to, the multi-image display apparatusaccording to an example embodiment may include the light sourceand the spatial light modulatordisposed to face each other in a first direction, a first linear polarization platea and the polarization selective lensdisposed to face each other in a second direction, the beam splitterdisposed at a point in which an optical path between the light sourceand the spatial light modulatorcrosses an optical path between the first linear polarization platea and the polarization selective lens, the first ¼ wavelength platea between the beam splitterand the spatial light modulator, the second ¼ wavelength plateb between the beam splitterand the polarization selective lens, the collimating lensbetween the light sourceand the beam splitter, a second linear polarization plateb between the light sourceand the beam splitter, and the controllerconfigured to control operations of the light sourceand the spatial light modulator.illustrates that the collimating lensis disposed ahead of the second linear polarization plateb and closer to the light source. However, the location of the collimating lensand the second linear polarization plateb may be the opposite.

400 300 115 110 113 115 110 110 115 400 300 8 FIG. 7 FIG. 8 FIG. 7 FIG. The multi-image display apparatusillustrated inmay have substantially the same structure as the multi-image display apparatusillustrated in, and may further include the second linear polarization plateb disposed between the light sourceand the beam splitter. The second linear polarization plateb may transmit only light having a first linear polarization component and may block light having a second linear polarization component orthogonal to the first linear polarization component. In the example embodiment illustrated in, the light sourcemay include a non-polarization laser rather than a polarization laser, or an LED. Light emitted from the light sourcemay be non-polarized light and may have the first linear polarization component by passing through the second linear polarization plateb. Other configurations and operations of the multi-image display apparatusmay be the same as those of the multi-image display apparatusdescribed with reference to.

9 FIG. 9 FIG. 9 FIG. 500 500 110 120 113 110 120 111 113 110 112 113 110 114 130 113 114 130 140 110 120 111 112 110 111 112 113 113 1 113 2 114 is a schematic view illustrating a configuration of a multi-image display apparatusaccording to an example embodiment. Referring to, the multi-image display apparatusmay include the light sourceand the spatial light modulatordisposed to face each other in a first direction, a first beam splittera disposed on an optical path between the light sourceand the spatial light modulator, the collimating lensdisposed between the first beam splittera and the light source, the ¼ wavelength platedisposed between the first beam splittera and the light source, the circular polarization plateand the polarization selective lensdisposed to face each other in the first direction, a second beam splitterb on an optical path between the circular polarization plateand the polarization selective lens, and the controllerconfigured to control operations of the light sourceand the spatial light modulator.illustrates that the collimating lensis disposed ahead of the ¼ wavelength plateand closer to the light source. However, the location of the collimating lensand the ¼ wavelength platemay be the opposite. The second beam splitterb may be disposed to face the first beam splittera and may be disposed to reflect light Lfrom the first beam splittera and transmit light Lfrom the circular polarization plate.

110 1 1 112 120 1 113 113 130 1 The light sourcemay include a polarization laser emitting the light Llinearly polarized in the first direction. The light Lmay pass through the ¼ wavelength plateto have a second circular polarization component and may be reflected by the spatial light modulatorto have a travel direction changed to an opposite direction, to have a first circular polarization component. Thereafter, the light Lmay be sequentially reflected by the first beam splittera and the second beam splitterb at an angle of 90 degrees, and may be incident on the polarization selective lensin a state in which the light Lhas the first circular polarization component.

2 114 114 2 114 113 130 2 Meanwhile, light Lfrom the actual external scene may pass through the circular polarization plate. The circular polarization platemay be configured to block light having the first circular polarization component and transmit only light having the second circular polarization component. Thus, the light Lpassing through the circular polarization platemay pass through the second beam splitterb and may be incident on the polarization selective lensin a state in which the light Lhas the second circular polarization component.

120 120 600 10 FIG. So far, example embodiments in which the spatial light modulatoris a reflective-type light modulator is described. However, the spatial light modulatormay be a transmissive-type light modulator. The transmissive-type light modulator may include, for example, a semiconductor modulator based on a compound semiconductor, such as gallium arsenide (GaAs), or a liquid crystal device (LCD). For example,is a schematic view illustrating a configuration of a multi-image display apparatusaccording to an example embodiment.

10 FIG. 600 115 130 113 115 130 112 113 130 110 113 120 110 113 111 110 120 140 110 120 Referring to, the multi-image display apparatusmay include the linear polarization plateand the polarization selective lensdisposed to face each other in a first direction, the beam splitterdisposed on an optical path between the linear polarization plateand the polarization selective lens, the ¼ wavelength platebetween the beam splitterand the polarization selective lens, the light sourcedisposed to face the beam splitterin a second direction, the spatial light modulatordisposed between the light sourceand the beam splitter, the collimating lensdisposed between the light sourceand the spatial light modulator, and the controllerconfigured to control operations of the light sourceand the spatial light modulator.

2 115 115 2 115 2 113 112 2 112 130 Light Lfrom the actual external scene may pass through the linear polarization plate. The linear polarization platemay be configured to block light having a second linear polarization component and transmit only light having a first linear polarization component. Thus, the light Lpassing through the linear polarization platemay have the first linear polarization component. The light Lmay pass through the beam splitterand may be incident on the ¼ wavelength plate. Thereafter, the light Lhaving the first linear polarization component may pass through the ¼ wavelength plateto be converted into second circular polarization light and may reach the polarization selective lens.

110 1 110 120 1 113 112 1 112 130 110 110 113 The light sourcemay include a polarization laser configured to emit light linearly polarized in the second direction. Light Lemitted from the light sourcemay be diffracted and modulated by passing through the spatial light modulator. Thereafter, the light Lmay be reflected by the beam splitterat an angle of about 90 degrees and may be incident on the ¼ wavelength plate. The light Lhaving the second linear polarization component may be converted into first circular polarization light by passing through the ¼ wavelength plateand may reach the polarization selective lens. Alternatively, the light sourcemay include a non-polarization laser or an LED. In this case, a linear polarization plate may further be disposed on the optical path between the light sourceand the beam splitter, the linear polarization plate being configured to block light having the first linear polarization component and transmitting only light having the second linear polarization component.

113 113 The beam splittermay include a half-transparent mirror simply reflecting a portion of incident light and transmitting the other portion of the incident light. The beam splittermay include a polarization selective mirror transmitting light having the first linear polarization component and reflecting light having the second linear polarization component.

11 FIG. 11 FIG. 700 700 114 130 113 114 130 110 113 120 110 113 111 110 120 112 110 113 140 110 120 Also,is a schematic view illustrating a configuration of a multi-image display apparatusaccording to an example embodiment. Referring to, the multi-image display apparatusmay include the circular polarization plateand the polarization selective lensdisposed to face each other in a first direction, the beam splitterdisposed on an optical path between the circular polarization plateand the polarization selective lens, the light sourcedisposed to face the beam splitterin a second direction, the spatial light modulatordisposed between the light sourceand the beam splitter, the collimating lensbetween the light sourceand the spatial light modulator, the ¼ wavelength plateon an optical path between the light sourceand the beam splitter, and the controllerconfigured to control operations of the light sourceand the spatial light modulator.

110 1 110 120 1 112 112 120 113 112 112 110 113 1 113 130 11 FIG. The light sourcemay include a polarization laser configured to emit light linearly polarized in the second direction. Light Lemitted from the light sourcemay be diffracted and modulated by passing through the spatial light modulator. Thereafter, the light Lhaving the second linear polarization component may be converted into first circular polarization light by passing through the ¼ wavelength plate.illustrates that the ¼ wavelength plateis disposed between the spatial light modulatorand the beam splitter. However, the location of the ¼ wavelength plateis not limited thereto. The ¼ wavelength platemay be disposed at any locations of the optical path between the light sourceand the beam splitter. The light Lhaving the first circular polarization component may be reflected by the beam splitterat an angle of about 90 degrees and then may reach the polarization selective lens.

110 110 112 110 112 114 110 113 The light sourcemay include a non-polarization laser or an LED. In this case, a linear polarization plate configured to block light having a first linear polarization component and transmit only light having the second linear polarization component may further be disposed between the light sourceand the ¼ wavelength plate. According to an example embodiment, when the light sourceincludes a non-polarization laser or an LED, the ¼ wavelength platemay be eliminated, and instead, a circular polarization plateconfigured to block light having a second circular polarization component and transmit only light having a first circular polarization component may be disposed on the optical path between the light sourceand the beam splitter.

2 114 114 2 114 2 130 2 113 Light Lfrom the actual external scene may pass through the circular polarization plate. The circular polarization platemay be configured to block the light having the first circular polarization component and transmit only the light having the second circular polarization component. Thus, the light Lpassing through the circular polarization platemay have the second circular polarization component. The light Lmay reach the polarization selective lensin a state in which the light Lhas the second circular polarization component by passing through the beam splitter.

113 113 The beam splittermay include a half-transparent mirror simply reflecting a portion of incident light and transmitting the other portion of the incident light. The beam splittermay include a polarization selective mirror transmitting the light having the second circular polarization component and reflecting the light having the first circular polarization component.

12 14 FIGS.through 12 14 FIGS.through 12 14 FIGS.through 100 700 100 700 100 700 100 700 100 700 illustrate example electronic apparatuses in which the multi-image display apparatusesthroughdescribed above may be implemented. As illustrated in, at least one or more of the multi-image display apparatusesthroughaccording to example embodiments may be included in wearable devices. In other words, the multi-image display apparatusesthroughmay be implemented in the wearable devices. For example, the multi-image display apparatusesthroughmay be implemented in a head mounted display (HMD). Also, the multi-image display apparatusesthroughmay be implemented in a glasses-type display, a goggle-type display, etc. The wearable electronic devices illustrated inmay operate in interconnection with a smart phone.

100 700 100 700 100 700 100 700 Additionally, the multi-image display apparatusesthroughaccording to example embodiments may be included in a smartphone, or a smartphone may be used as the multi-image display apparatus. In other words, the multi-image display apparatusesthroughmay be implemented in a small electronic device, such as a mobile electronic device. In addition, the fields in which the multi-image display apparatusesthroughaccording to example embodiments may be implemented may vary. For example, the multi-image display apparatusesthroughaccording to example embodiments may be implemented to realize not only AR but also MR and may also be implemented in other fields. In other words, in addition to the AR or the MR, the disclosure based on example embodiments described above may be applied to a display capable of simultaneously viewing a plurality of images.

The above multi-image display apparatuses providing a holographic image are described with reference to the example embodiments illustrated in the drawings. However, it may be understood by one of ordinary skill in the art that they are only examples and various modifications and equivalent embodiments are possible based on the multi-image display apparatuses.

It should be understood that example embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.

While example embodiments have been described with reference to the figures, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.