See-through type display apparatus

A display apparatus includes: a display device configured to output a first image; an optical coupler configured to: combine the first image received through a first path from the display device with a second image received through a second path that is different from the first path, output, through an exit surface of the optical coupler, a first light corresponding to the first image in a first polarization and a second light corresponding to the second image in a second polarization; and a polarization selection optical system arranged on the exit surface of the optical coupler and configured to have different refractive power with respect to the first light of the first polarization and the second light of the second polarization.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No. 10-2018-0114147, filed on Sep. 21, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

Example embodiments of the present disclosure relate to see-through type display apparatuses.

2. Description of the Related Art

A head-mounted display that provides virtual reality (VR) is now in the stage of commercialization, and has been widely applied in the entertainment industry. In addition, the head-mounted display is being developed for applications in medical, educational, and industrial fields.

An augmented reality (AR) display that is an advanced form of a VR display is an image apparatus combining the real world and VR, and has a characteristic that facilitates interactions between reality and virtuality. Interactions between reality and virtuality is based on a function of providing information about a real situation in real-time and may improve the reality effect by showing a virtual object or information superimposed on an environment of the real world.

An optical system included in such a display includes a beam splitter, a convex lens, a concave mirror, etc., which increase a physical volume, and thus, becomes a cause for increasing the total volume of the optical system.

SUMMARY

Provided are see-through type display apparatuses.

According to an aspect of the disclosure, there is provided a display apparatus comprising: a display device configured to output a first image; an optical coupler configured to: combine the first image received through a first path from the display device with a second image received through a second path that is different from the first path, output, through an exit surface of the optical coupler, a first light corresponding to the first image in a first polarization and a second light corresponding to the second image in a second polarization; and a polarization selection optical system arranged on the exit surface of the optical coupler and configured to have different refractive power with respect to the first light of the first polarization and the second light of the second polarization.

The first polarization and the second polarization maybe linear polarizations that maybe perpendicular to each other.

The optical coupler may comprise: an optical waveguide comprising a first surface, a second surface, and the exit surface, wherein the first image is incident on the first surface and the second image is incident on the second surface; and a beam splitter arranged in the optical waveguide in an inclined manner with respect to the exit surface.

The beam splitter may comprise a polarization beam splitter that reflects the first light of the first image in the first polarization and transmits the second light of the second image in the second polarization.

The optical waveguide may further comprise a transmittance adjusting coating layer provided at least partially on the second surface and the exit surface to reduce a transmittance of light of the second image incident through the second surface and emitted from the optical coupler without passing through the polarization beam splitter.

The optical coupler may further comprise: a first polarizer arranged between the display device and the optical waveguide to transform the first image into a first polarization state; and a second polarizer arranged on the second surface of the optical waveguide to transform the second image into a second polarization state.

The beam splitter may comprise a half mirror.

The polarization selection optical system may comprise a polarization selection lens configured to have refractive power with respect to light of a certain polarization and to not have refractive power with respect to light of a polarization different from the certain polarization.

The polarization selection lens may have the refractive power with respect to the light of the certain polarization, the refractive power being adjustable according to a control signal from outside the display apparatus.

The polarization selection lens may further configured to have a positive refractive power with respect to the light of the first polarization and to not have refractive power with respect to the light of the second polarization.

The polarization selection lens may further configured to have a positive refractive power with respect to light of a first circular polarization and to not have refractive power with respect to light of a second circular polarization that is opposite to the first circular polarization.

The polarization selection optical system may further comprise a quarter-wave plate arranged between the exit surface and the polarization selection lens.

An incident surface of the polarization selection lens maybe parallel with the exit surface of the optical coupler.

The polarization selection lens may comprise an optical anisotropic material having different refractive indices with respect to the light of the certain polarization and light of another polarization that is different from the certain polarization.

The polarization selection lens may comprise a diffraction-based lens.

The polarization selection lens may comprise: a half mirror; a reflective polarizer; and a quarter-wave plate arranged between the half mirror and the reflective polarizer.

The display apparatus may further comprise an aberration correcting optical member configured to correct optical aberration corresponding to the first image.

The aberration correcting optical member may comprise a lens arranged between the display device and the first surface.

A shape of a curved surface of the lens or a location of the lens on an optical axis maybe adjusted according to a control signal from outside the display apparatus.

The optical waveguide may further comprise a third surface between the second surface and the exit surface, the third surface being away from the first surface, and the aberration correcting optical member is a mirror arranged on the third surface.

A shape of a curved surface in the mirror or a location of the mirror on an optical axis maybe adjusted according to a control signal from outside the display apparatus.

According to another aspect of the disclosure there is provided a display apparatus comprising: a display device configured to output a first image; an optical coupler configured to: combine the first image received through a first path from the display device with a second image received through a second path that is different from the first path, and output a first light corresponding to the first image in a first polarization and a second light corresponding to the second image in a second polarization through an exit surface of the optical coupler; a polarization selection optical system arranged on the exit surface of the optical coupler and configured to have different refractive power with respect to the first light of the first polarization and the second light of the second polarization; a variable optical device arranged on an optical path along which the first image travels towards the polarization selection optical system; and a processor configured to control the variable optical device to control a characteristic of the first image.

The variable optical device may comprise a lens or a mirror having a variable refractive power and is configured to adjust a location of the lens or the mirror on an optical axis or adjust the variable refractive power.

The processor may further configured to set a range for controlling the variable optical device according to depth information of the first image.

The processor may further configured to set a range for controlling the variable optical device according to eyesight information of an observer.

The processor may further configured to adjust a range for controlling the variable optical device according to depth information of the first image and eyesight information of an observer.

According to another aspect of the disclosure, there is provided a display apparatus comprising: a display device configured to output a first image; an optical coupler configured to: combine the first image received through a first path from the display device with a second image received through a second path that is different from the first path, and output a first light corresponding to the first image in a first polarization and a second light corresponding to the second image in a second polarization through an exit surface; a polarization selection optical system arranged on the exit surface of the optical coupler and configured to have a first refractive power with respect to the first light of the first polarization and a second refractive power with respect to the second light of the second polarization, the first refractive power being different from the second refractive power; and a processor configured to generate a control signal to control at least one of the first refractive power and the second refractive power of the polarization selection optical system.

The processor may further configured to adjust the first refractive power according to depth information of the first image.

The processor may further configured to adjust the second refractive power according to eyesight information of an observer.

The processor may further configured to adjust the first refractive power according to depth information of the first image and adjust the second refractive power according to eyesight information of an observer.

The display apparatus may further comprise a variable optical device arranged on an optical path along which the first image travels towards the polarization selection optical system.

The variable optical device may comprise a lens or a mirror having a third refractive power and configured to adjust a location of the lens or the mirror on an optical axis or adjust the third refractive power.

The processor may further configured to adjust the third refractive power or the location according to depth information of the first image.

The processor may further configured to adjust the third refractive power or the location according to eyesight information of an observer.

The display apparatus may be a wearable see-through type display device.

According to another aspect of the disclosure, there is provided a display apparatus comprising: an optical waveguide comprising: a first surface which receives a first image; a second surface which receives a second image; and a third surface which outputs a combined image; an optical element provided inside the optical waveguide, the optical element being configured to combine the first image and the second image to produce the combined image; and a polarization selection element provided on the third surface of the optical waveguide.

The optical element maybe one of a beam splitter or a half mirror.

The polarization selection element maybe a lens.

The polarization selection element maybe configured to have refractive power to the output combined image based on a polarization of a first light corresponding to the first image and a second light corresponding to the second image.

DETAILED DESCRIPTION

Hereinafter, example embodiments of the present disclosure will be described in detail with reference to accompanying drawings. In the drawings, like reference numerals denote like components, and sizes of components in the drawings may be exaggerated for convenience of explanation. The example embodiments of the disclosure are capable of various modifications and may be embodied in many different forms.

When a layer, a film, a region, or a panel is referred to as being “on” another element, it may be directly on the other layer or substrate, or intervening layers may also be present.

An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. Throughout the specification, when a portion “includes” an element, another element may be further included, rather than excluding the existence of the other element, unless otherwise described.

As used herein, in particular, terms such as “the” and demonstratives similar thereto used herein may be to indicate both the singular and the plural.

Also, the steps of all methods described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The disclosure is not limited to the described order of the steps. The use of any and all examples, or example language (e.g., “such as”) provided herein, is intended merely to better illuminate the disclosure and does not pose a limitation on the scope of the present disclosure unless otherwise claimed.

FIG. 1is a conceptual diagram illustrating a see-through type display apparatus according to an example embodiment that provides an observer with a combined image.FIG. 2Ais a diagram of an optical path, in which light from different paths is coupled and output in different polarizations by an optical coupler provided in a see-through type display apparatus according to an example embodiment, andFIGS. 2B and 2Care diagrams showing a polarization selection optical system provided in a see-through type display apparatus according to an example embodiment that performs optical effects which vary depending on light of different polarizations.

The see-through type display apparatus according to the example embodiment may combine a first image with a second image, wherein the first and second images come from different paths, and provide an observer with a combined image. The see-through type display apparatus includes an optical coupler CB and a polarization selection optical system PS.

As illustrated inFIG. 2, the optical coupler CB combines the first image with the second image incident to the optical coupler CB from a path different from that of the first image and outputs the combined image through an exit surface ES. Here, the optical coupler CB outputs the two images as light of different polarizations. For example, light L1of the first image may be output as light of a first polarization (⊙), and light L2of the second image may be output as light of a second polarization (). The first polarization ⊙ and the second polarizationmay be linear polarizations perpendicular to each other. However, one or more example embodiments are not limited to the above example. In accompanying drawings, even when there is no specific description, the light L1of the first image is output in the first polarization ⊙ state and the light L2of the second image is output in the second polarizationstate from the optical coupler CB.

The optical coupler CB may include an optical waveguide LG and a beam splitter BS arranged in the optical waveguide LG. The beam splitter BS may be arranged on an optical path, along which the light L1of the first image and the light L2of the second image pass, in the optical waveguide LG to be inclined with the exit surface ES. For example, an angle between the beam splitter BS and the exit surface ES may be 45°. The beam splitter BS may be a polarized beam splitter. According to an example embodiment, the beam splitter may reflect the light of the first polarization ⊙ and may transmit the light of the second polarization. The light L1of the first image may proceed along the optical waveguide LG and then change the optical path when the first polarization ⊙ component is reflected by the beam splitter BS. When the light L1of the first image and the light L2of the second image from a different path encounter the beam splitter BS, the second polarizationcomponent passes through the beam splitter BS. Accordingly, the light L1of the first image may be emitted in the first polarization ⊙ state and the light L2of the second image may be emitted in the second polarization ⇄ state from the optical coupler CB through the same exit surface ES. According to an example embodiment, the light L1of the first image may proceed along the optical waveguide LG by total internal reflection of the waveguide LG.

WhileFIG. 2Aconceptually describes the configuration in which the optical coupler CB emits the light L1of the first image in the first polarization ⊙ state and the light L2of the second image in the second polarizationstate, detailed shape of the optical coupler CB may be vary with modified forms of the optical waveguide LG and the beam splitter BS, and other additional optical elements according to different embodiments.

Referring toFIGS. 2B and 2C, the polarization selection optical system PS may have refractive power that varies depending on the light of the first polarization ⊙ and the light of the second polarizationoutput from the optical coupler CB. To do this, the polarization selection optical system PS may include a polarization selection lens PSL performing different optical functions on two different polarizations.

As shown inFIG. 2B, the polarization selection lens PSL included in the polarization selection optical system PS applies positive refractive power with respect to the light of the first polarization ⊙. That is, the polarization lens PSL may focus the light L1of the first image and perform imaging of the first image at a desired location like a focusing lens. The first image may be formed by, for example, a display device, and the polarization selection lens PSL performs a focusing function that is the last stage of an imaging optical system.

Referring toFIG. 2C, the polarization selection lens PSL included in the polarization selection optical system PS may rarely have the refractive power with respect to the light of the second polarization. This may denote that the refractive power with respect to the light of the second polarizationis very small or little as compared with the refractive power with respect to the light of the first polarization ⊙. The light L2of the second image in the second polarizationstate may include, for example, a real world scene that is not necessarily focused for recognizing the image.

FIGS. 2B and 2Cshow that the polarization selection lens PSL has different refractive effects on different linear polarizations, but one or more embodiments are not limited thereto. The polarization selection lens PSL may have different refractive actions on circular polarizations in different directions, and in this case, the polarization selection optical system PS may further include a quarter-wave plate on a path of the light incident on the polarization selection lens PSL.

An observer may simultaneously recognize the first image and the second image through the optical coupler CB and the polarization selection optical system PS. The first image may be a virtual reality (VR) image generated by a display device to include additional information about the second image that is the real world image. As described above, the optical coupler CB and the polarization selection optical system PS may be applied to an augmented reality (AR) display apparatus.

The polarization selection lens PSL provided in the polarization selection optical system PS may include an optical anisotropic material having different refractive indices with respect to light of two different polarizations, or may include a diffraction-based lens such as a geometric phase lens or a meta lens.

Exemplary configurations of the polarization selection lens PSL will be described below with reference toFIGS. 3A to 3F.

Referring toFIG. 3A, a polarization selection lens PSL1may include a refractive lens10and a liquid crystal layer20. According to an example embodiment, the liquid crystal layer20may include liquid crystal molecules. A liquid crystal molecule is a material having optical anisotropy, and applies different refractive indices with respect to light that is in parallel with a major axis direction of the liquid crystal molecule and light that is in parallel with a minor axis direction of the liquid crystal molecule. Alignment of the liquid crystal molecules may be electrically controlled and may be adjusted so as to have different refractive indices with respect to desired light of two different polarizations. The refractive lens10may include an optical isotropic material and may have a predetermined curved surface. The refractive index of the refractive lens10may be set to be identical with a refractive index of the liquid crystal layer20with respect to one polarization, so that the polarization selection lens PSL1does not have the refractive power with respect to one polarization and applies the refractive power only with respect to one another polarization.

Referring toFIG. 3B, a polarization selection lens PSL2may include a Fresnel lens12and a liquid crystal layer22. The polarization selection lens PSL2may be a modified example of the polarization selection lens PSL1shown inFIG. 3A. The Fresnel lens12has a reduced thickness by splitting and rearranging the curved surface of the refractive lens10ofFIG. 3A. The Fresnel lens12may have substantially the same functions as those of the refractive lens10. Therefore, the structure ofFIG. 3Aor the structure ofFIG. 3Bmay be selected taking into account the curved surface shape to be formed. For example, when the curved surface to be formed has a small radius of curvature and is large in thickness, the thickness may be reduced by using the Fresnel lens12.

Referring toFIG. 3C, a polarization selection lens PSL3includes a plurality of optical anisotropic material layers30_1to30_n, where n is an integer greater than 1. The plurality of optical anisotropic material layers30_1to30_nhaving different refractive indices are stacked to represent the refractive index that is different according to the polarization.

Referring toFIG. 3D, a polarization selection lens PSL4includes a birefringent crystal40and index oil50. The birefringent crystal40may be formed by processing a material having a birefringent property as a lens. The birefringent crystal40may be arranged in the index oil50. The index oil50may have a refractive index that is the same as one certain refractive index represented by the birefringent crystal40.

Referring toFIG. 3E, a polarization selection lens PSL5includes a plurality of diffraction-based lenses61and62and a plurality of optical films71and72. The diffraction-based lenses61and62may include geometric phase lenses or meta lenses. The geometric phase lens may geometrically modulate a phase by using a non-linear material element. For example, various geometric phases may be formed by adjusting the orientation state of the liquid crystal. The meta lens may include nanostructures having sub-wavelength dimensions. Shapes and arrangement of the nanostructures having the dimensions that are less than the wavelength of incident light may be appropriately set to represent a desired refractive index according to the polarization.

The diffraction-based lenses61and62may indicate conjugation optical characteristics according to the polarization, and the optical films71and72such as a polarizer, a phase retarder, etc. maybe arranged to indicate the desired refractive power according to the polarization.

Referring toFIG. 3F, a polarization selection lens PSL6includes a half mirror80, a quarter-wave plate85, and a reflective polarizer90that are sequentially arranged according to a proceeding direction of light.

The polarization selection lens PSL6may have the refracting operation that is different according to, for example, circular polarization. When light of clockwise circular polarization is incident, the light is transformed to light of second polarizationwhile passing through the quarter-wave plate85, and thus, reflected by the reflective polarizer90that reflects the light of the second polarization. Thereafter, the light reflected by the polarizer90becomes the clockwise circular polarization while passing through the quarter-wave plate85, which is then reflected by the half mirror80to be the light of counter-clockwise circular polarization. The counter-clockwise circularly polarized light is transformed into the light of the first polarization ⊙ while passing through the quarter-wave plate85, and passes through the reflective polarizer90. In the above optical path, the refraction operation of the light may be adjusted according to a shape of a reflective surface90aof the reflective polarizer90and a shape of a reflective surface80aof the half mirror80, wherein the light is reflected by the reflective polarizer90, reflected by the half mirror80, and then, passes through the reflective polarizer90. That is, the light of clockwise circular polarization incident on the polarization selection lens PSL6is refracted by the combination of the reflective surface80aof the half mirror80and the reflective surface90aof the reflective polarizer90. The above refraction may be, for example, positive refractive power.

When the light of counter-clockwise circular polarization is incident on the polarization selection lens PSL6, the light is transformed into the first polarization ⊙ by the quarter-wave plate85and passes through the reflective polarizer90. The light of the counter-clockwise circular polarization incident into the polarization selection lens PSL6is not reflected by the half mirror80or the reflective polarizer90, but passes through the polarization selection lens PSL6. Accordingly, the light is refracted differently from the light of the clockwise circular polarization. The above refraction may be, for example, performed by refractive power that is much smaller than that applied to the light of the clockwise circular polarization or by little refractive power.

The polarization selection lens PSL6may have different refraction operations with respect to the light of the clockwise circular polarization and the light of the counter-clockwise circular polarization by appropriately combining the shape of the reflective surface80aof the half mirror80and the reflective surface90aof the reflective polarizer90, for example, may have the positive refractive power to the light of the clockwise circular polarization and may operate in a mode with little refractive power with respect to the light of the counter-clockwise circular polarization.

A polarization selection lens PSL6′ ofFIG. 3Gis an example of adopting principles of the polarization selection lens PSL6shown inFIG. 3F, and includes a first lens LS1, a half mirror81, a second lens LS2, a quarter-wave plate85, and a reflective polarizer91. A bonding surface of the first lens LS1and the second lens LS2is a curved surface, to which a half-mirror coating may be applied.

When the light of the clockwise circular polarization is incident on the polarization selection lens PSL6′, the light is transformed into the light of the second polarizationwhile passing through the quarter-wave plate85, is reflected by the reflective polarizer91that reflects the light of the second polarization, and then, is transformed into the light of the clockwise circular polarization while passing through the quarter-wave plate85. The light of the clockwise circular polarization is reflected by the half mirror81to be the light of counter-clockwise circular polarization and then is transformed into the light of the first polarization ⊙ while passing through the quarter-wave plate85, and passes through the reflective polarizer91. The light of the clockwise circular polarization incident on the polarization selection lens PSL6′ is refracted by the half mirror81having a concave reflective surface.

When the light of counter-clockwise circular polarization is incident on the polarization selection lens PSL6′, the light is transformed into the first polarization ⊙ by the quarter-wave plate85and passes through the reflective polarizer91. The light of the counter-clockwise circular polarization incident on the polarization selection lens PSL6′ passes through the polarization selection lens PSL6′ without being reflected by the half mirror81or the reflective polarizer91, that is, the polarization selection lens PSL6′ rarely applies the refractive power with respect to the light of the counter-clockwise circular polarization.

InFIG. 3G, the first lens LS1and the second lens LS2are arranged to provide a coating surface for forming the half mirror81, and are not limited thereto, and the first and second lenses LS1and LS2may be omitted. For example, a concave half mirror may be provided without using the first lens LS1and the second lens LS2.

FIG. 3Gshows an example of a polarization selection lens illustrated inFIG. 3F, and includes various shape combinations adopting the principle of the polarization selection lens PSL6illustrated with reference toFIG. 3Fand additional optical elements to have different refractive powers with respect to different polarizations.

Hereinafter, the see-through type display apparatuses according to example embodiments will be described below.

FIG. 4is a diagram of a structure and an optical arrangement of a see-through type display apparatus1000according to an example embodiment.

The see-through type display apparatus1000according to the example embodiment includes a display device100, an optical coupler CB1, and a polarization selection lens400.

The display device100modulates light according to first image information to form light L1of a first image. The first image may be a two-dimensional image or a three-dimensional image, and the three-dimensional image may include a hologram image, a stereo image, a light field image, an integral photography (IP) image, a multi-view or super multi-view type image, etc.

The display device100may include, for example, a liquid crystal on silicon (LCoS) device, a liquid crystal display (LCD) device, an organic light-emitting diode (OLED) display device, a digital micromirror device (DMD), or a next generation display device such as micro LED, quantum dot (QD) LED, etc.

The optical coupler CB1couples the light L1of the first image from the display device100and light L2of a second image from a different path and emits the combined light in different polarizations. According to an example embodiment, the optical coupler CB1includes an optical waveguide200and a beam splitter300.

The optical waveguide200includes an exit surface200a, from which the light is emitted. Further, the optical coupler CB1includes a first surface200bto which the light L1of the first image is incident, a second surface200cto which the light L2of the second image is incident, and a third surface200dfacing the first surface200bbetween the exit surface200aand the second surface200c.

The beam splitter300may be arranged in the optical waveguide200to be inclined with respect to the exit surface200a. The beam splitter300is a polarized beam splitter which reflects light of a first polarization and transmits light of a second polarization. The first polarization and the second polarization may be linear polarizations perpendicular to each other. The light L1of the first image and the light L2of the second image, which are incident through different paths, proceed in a same path after passing through the beam splitter300and are emitted from the exit surface200arespectively in the first polarization state and the second polarization state.

The polarization selection optical system may include a polarization selection lens400that applies refractive power with respect to the light of the first polarization and does not have refractive power with respect to the light of the second polarization. The polarization selection lens PSL1, PSL2, PSL3, PSL4, PSL5, or PSL6illustrated with reference toFIGS. 3A to 3F, or a modified example thereof may be provided as the polarization selection lens400. According to another example embodiment, the polarization selection lens may be provided as part of a polarization selection optical system.

An incident surface400aof the polarization selection lens400may be in parallel with the exit surface200aof the optical coupler CB1. Therefore, a distance between the optical coupler CB1and the polarization selection lens400may be reduced, and desired optical performance may be achieved while reducing the total volume of the see-through type display apparatus1000.

FIG. 5is a diagram of an optical arrangement in a see-through type display apparatus1according to a comparative example.

The see-through type display apparatus1according to a comparative example includes a display device5, a beam splitter6, and a concave mirror7. Light from the display device5reaches an observer after reflecting from the concave mirror7. However, due to the characteristics of this optical path, a volume of the optical system may increase. Moreover, an additional increase in the volume may occur with implementation of desired optical performance. For example, in order to increase the refractive power of the concave mirror7, a total volume may increase further.

Unlike the see-through type display apparatus according to the comparative example, the see-through type display apparatus1000according to the example embodiment includes the optical coupler CB1, in which the beam splitter300is arranged in the optical waveguide200, and the polarization selection lens400, a distance of which from the optical coupler CB1may be reduced, to achieve reduction in the volume and improvement in performance.

FIG. 6is a diagram of a structure and an optical arrangement of a see-through type display apparatus1001according to another example embodiment.

The see-through type display apparatus1001includes a display device100, an optical coupler CB3, and the polarization selection lens400. The see-through type display apparatus1001of the example embodiment is different from the see-through type display apparatus1000ofFIG. 4in view of a shape of an optical waveguide210.

The optical waveguide210includes an exit surface210a, from which the light is emitted, a first surface210bto which the light L1of the first image is incident, a second surface210cto which the light L2of the second image is incident, a mirror surface210eadjacent to the first surface210band provided between the exit surface210aand the second surface210c, and a third surface210dfacing the mirror surface210ebetween the exit surface210aand the second surface210c. The exit surface210ais flush with the first surface210b. The light L1of the first image incident through the first surface210bis reflected by the mirror surface210ethat is inclined with respect to the first surface210b, proceeds in the optical waveguide210to reach the beam splitter300, and then, is reflected by the beam splitter300and emitted through the exit surface210a.

Due to a shape of the optical waveguide210and the arrangement of the display device100, an incident angle of the light L1from the display device100to the beam splitter300may be different from that ofFIG. 4. Accordingly, the beam splitter300may be arranged to be more inclined than that ofFIG. 4, for example, an angle between the beam splitter300and the exit surface210amay be less than 45°. Also, a thickness of the optical waveguide210may be less than that of the optical waveguide200ofFIG. 4.

FIG. 7is a diagram of a structure and an optical arrangement of a see-through type display apparatus1002according to another example embodiment.

The see-through type display apparatus1002includes the display device100, the optical coupler CB3, and the polarization selection lens400.

The see-through type display apparatus1002of the example embodiment is different from the see-through type display apparatus1000ofFIG. 4in view of a shape of an optical waveguide220.

The optical waveguide220includes an exit surface220afrom which the light is emitted, a first surface220bto which the light L1of the first image is incident, a second surface220cto which the light L2of the second image is incident, and a third surface220dfacing the first surface220bbetween the exit surface220aand the second surface220c. The first surface220bis arranged inclined unlike the first surface210bin the see-through type display apparatus1000ofFIG. 4. That is, an angle between the first surface220band the exit surface220amay be less than 90°. Therefore, an incident angle of the light L1of the first image that is incident through the first surface220bto the beam splitter300may be different from that ofFIG. 4. Accordingly, the beam splitter300may be arranged to be more inclined than that ofFIG. 4, for example, an angle between the beam splitter300and the exit surface220amay be less than 45°. Also, a thickness of the optical waveguide220may be less than that of the optical waveguide200ofFIG. 4.

FIG. 8is a diagram of a structure and an optical arrangement of a see-through type display apparatus1003according to another example embodiment.

The see-through type display apparatus1003includes the display device100, an optical coupler CB4, and the polarization selection lens400.

The see-through type display apparatus1003according to the example embodiment is different from the see-through type display apparatus1000ofFIG. 4in that transmittance adjusting coating layers251and252are further formed on the optical waveguide200.

The optical waveguide200includes the exit surface200afrom which the light is emitted, the first surface200bto which the light L1of the first image is incident, the second surface200cto which the light L2of the second image is incident, and the third surface200dfacing the first surface200bbetween the exit surface200aand the second surface200c. In addition, the transmittance adjusting coating layers251and252are respectively formed at least partially on the second surface200cand the exit surface200a.

The transmittance adjusting coating layers251and252are provided to reduce transmittance of the light that is emitted from the optical coupler CB4without passing through the beam splitter300, from the light L2of the second image incident through the second surface200c.

When the beam splitter300is a polarization beam splitter, the beam splitter300includes a plurality of dielectric layers for polarization separation, and accordingly, the transmittance of the light L2of the second image emitted from the exit surface200aof the optical coupler CB4varies depending on whether the light passes through the beam splitter300or does not pass through the beam splitter300. When the transmittance adjusting coating layers251and252are provided on some regions of the second surface200cand the exit surface200a, the transmittance of the light L2of the second image through the path, in which the light L2does not pass through the beam splitter300, and the transmittance through the path, in which the light L2passes through the beam splitter300, may be similar to each other. The transmittance adjusting coating layers251and252may include a material that is the same as that of the coating applied on the beam splitter300for polarization separation. However, the example embodiment is not limited thereto, and any type of coating material that may allow the light to have similar transmittances in two paths may be applied.

Locations of the transmittance adjusting coating layers251and252are not limited to the examples shown in the drawings. For example, the transmittance adjusting coating layer251may be formed on an opposite side of the exit surface200a. Also, the transmittance adjusting coating layer252may be formed on an opposite side of the second surface200c. That is, the transmittance adjusting coating layers251and252may be both formed on the second surface200cor the exit surface200a, or may be formed respectively on the exit surface200aand the second surface200c.

FIG. 9is a diagram of a structure and an optical arrangement of a see-through type display apparatus1004according to another example embodiment.

The see-through type display apparatus1004includes the display device100, an optical coupler CB5, and the polarization selection lens400.

The see-through type display apparatus1004of the example embodiment is different from the see-through type display apparatus1000ofFIG. 4in that a first polarizer261is arranged on the first surface200bof the optical waveguide200and a second polarizer262is further arranged on the second surface200cof the optical waveguide200.

The first polarizer261only transmits the light of first polarization component and the second polarizer262only transmits the light of second polarization component in the incident light. Accordingly, the light L1of the first image from the display device100is incident in the first polarization state and the light L2of the second image is incident in the second polarization state to the optical waveguide200, and then reach a beam splitter310. In this case, the beam splitter310does not need to have the polarization separation function, and thus a half mirror may be used as the beam splitter310.

FIG. 10is a diagram of a structure and an optical arrangement of a see-through type display apparatus1005according to another example embodiment.

The see-through type display apparatus1005includes the display device100, an optical coupler CB1, and the polarization selection optical system401.

The see-through type display apparatus1005of the example embodiment is different from the see-through type display apparatus1000ofFIG. 4in that the polarization selection optical system401provides a polarization selection lens410that applies varying refractive power depending on a circular polarization component and further includes a quarter-wave plate420.

The polarization selection lens410may be the examples shown inFIGS. 3A to 3E, a combination thereof, or a modification thereof, and a combination of optical anisotropic materials and other components may be selected so that the refractive power may vary with respect to two different circular polarization components, not two different linear polarization components that are perpendicular to each other. Otherwise, the polarization selection lens having different refractive powers with respect to two circular polarizations in different directions illustrated with reference toFIG. 3Fmay be used.

The polarization selection lens410may have the refractive power with respect to, for example, the light of clockwise circular polarization and may not have the refractive power with respect to the light of counter-clockwise circular polarization.

The quarter-wave plate420arranged between the optical coupler CB1and the polarization selection lens410transforms the light L1of the first image that is emitted from the optical coupler CB1with the first polarization into the light of clockwise circular polarization and transforms the light L2of the second image emitted from the optical coupler CB1with the second polarization into the light of the counter-clockwise circular polarization. The polarization selection lens410may image the light L1of the first image in the clockwise circular polarization with refraction operation and may transmit the light L2of the second image in the counter-clockwise circular polarization without refraction operation.

FIG. 11is a diagram of a structure and an optical arrangement of a see-through type display apparatus1006according to another example embodiment.

The see-through type display apparatus1006includes the display device100, the optical coupler CB1, the polarization selection lens400, and a convex lens500between the display device100and the optical coupler CB1.

The see-through type display apparatus1006of the example embodiment is different from those of the previous example embodiments, in view of further including an aberration correcting optical member. Imaging of the light L1of the first image formed by the display device100by using only one lens may make it difficult to control the optical aberration, and thus, an additional optical member may be further provided to improve optical performance.

The see-through type display apparatus1006according to the example embodiment may further include the convex lens500for correcting aberration between the display device100and the optical waveguide200. The convex lens500may be located between the display device100and the first surface200b. The imaging optical performance may be further improved by using the convex lens500. InFIG. 11, the see-through type display apparatus1000ofFIG. 4is shown to further include the convex lens500, but embodiments are not limited thereto, and the see-through type display apparatus according to other embodiments may further include the convex lens500.

FIG. 12is a diagram of a structure and an optical arrangement of a see-through type display apparatus1007according to another example embodiment.

The see-through type display apparatus1007includes the display device100, the optical coupler CB2, the polarization selection lens400, and the convex lens500between the display device100and the optical coupler CB2.

The see-through type display apparatus1007corresponds to the see-through type display apparatus1001ofFIG. 6, in which the convex lens500is further arranged, that is, as shown inFIG. 12, the convex lens500may be arranged between the display device100and the first surface210bof the optical waveguide210. The imaging optical performance may be further improved by using the convex lens500.

FIG. 13is a diagram of a structure and an optical arrangement of a see-through type display apparatus1008according to another example embodiment.

The see-through type display apparatus1008includes the display device100, an optical coupler CB1′, the polarization selection lens400, and a concave mirror510.

The optical waveguide200includes the exit surface200afrom which the light is emitted, the first surface200bto which the light L1of the first image is incident, the second surface200cto which the light L2of the second image is incident, and the third surface200dfacing the first surface200bbetween the exit surface200aand the second surface200c. The concave mirror510may be adjacent to the third surface200dof the optical waveguide200.

The see-through type display apparatus1008of the example embodiment is different from the see-through type display apparatus1006shown inFIG. 11in that the concave mirror510is arranged adjacent to the third surface200dof the optical waveguide200, instead of the convex lens500adopted in the see-through type display apparatus1006ofFIG. 11, and an additional optical aberration is controlled through the concave mirror510. Accordingly, the beam splitter300is arranged opposite to that ofFIG. 11. As shown inFIG. 13, the beam splitter300of the optical coupler CB1′ is arranged so that a surface where the polarization separation occurs faces the concave mirror510.

FIG. 14is a diagram of a structure and an optical arrangement of a see-through type display apparatus1009according to another example embodiment.

The see-through type display apparatus1009includes the display device100, the optical coupler CB1′, the polarization selection lens400, the convex lens500between the display device100and the first surface200bof the optical waveguide200, and the concave mirror510arranged adjacent to the third surface200dof the optical waveguide200.

The see-through type display apparatus1009of the example embodiment is different from the see-through type display apparatus1008ofFIG. 13in that the convex lens500is further arranged between the display device100and the first surface200bof the optical waveguide200. Since two aberration correcting optical members are used, the optical aberration may be easily controlled and imaging optical performance may be further improved.

FIG. 15is a diagram showing a structure and optical arrangement of a see-through type display apparatus1010according to another example embodiment, andFIGS. 16A and 16Bare diagrams showing optical paths, in which a location of focusing incident light is changed according to an operation of a variable lens adopted in the see-through type display apparatus1010ofFIG. 15.

The see-through type display apparatus1010includes the display device100, the optical coupler CB1, the polarization selection lens400, and a variable lens520between the display device100and the optical coupler CB1.

The see-through type display apparatus1010of the example embodiment is different from the see-through type display apparatus1006ofFIG. 11in that a curved surface520aof the variable lens520may be adjusted or a location of the variable lens520on an optical axis may be adjusted according to a control signal SG from outside.

Referring toFIG. 16A, a location of the variable lens520on the optical axis may be moveable in a direction A. According to the location of the variable lens520, a location of focusing the light that has passed through the beam splitter300and the polarization selection lens400may vary between P1and P2.

Referring toFIG. 16B, a shape of the curved surface520ain the variable lens520may be controlled. According to the variation in the shape of the curved surface520a, the location of focusing the light from the variable lens520after passing through the beam splitter300and the polarization selection lens400may be switched to P1or P2.

The adjusting of the focusing location may be applied to express multi-depth. The multi-depth may be expressed by varying a reference surface, on which the image from the display device100is focused, within a predetermined depth range, and may contribute to increase in the depth and/or reduction in visual fatigue as compared with displaying of the image at a constant depth location. Moreover, the adjustment in the focusing location may be used for correction taking into account the eyesight of an observer. A focusing location variation range for expressing the multi-depth and a focusing location variation range for correcting eyesight may be different from each other and may be appropriately set for respective purposes. Also, operation of the variable lens520may be controlled so that the focusing location may vary taking into account the multi-depth expression and correction of eyesight of the observer.

FIG. 17is a diagram of a structure and an optical arrangement of a see-through type display apparatus1011according to another example embodiment.

The see-through type display apparatus1011includes the display device100, the optical coupler CB1′, the polarization selection lens400, and a variable mirror530arranged adjacent to the third surface200dof the optical waveguide200.

The see-through type display apparatus1011of the example embodiment is different from the see-through type display apparatus1008ofFIG. 13in that a curved surface of the variable mirror530may be adjusted or a location of the variable mirror530on an optical axis may be adjusted according to a control signal SG from outside.

Similarly to the see-through type display apparatus1010ofFIG. 15, the see-through type display apparatus1011of the example embodiment may control the variable mirror530taking into account the expression of multi-depth and/or correction of eyesight of the observer.

FIG. 18is a diagram showing a configuration and optical arrangement of a see-through type display apparatus1012according to another example embodiment, andFIG. 19is a diagram of an optical path, on which a focusing location of light of a first polarization is changed due to operation of a polarization selection lens ofFIG. 18.

The see-through type display apparatus1012includes a display device100, the optical coupler CB1, and a polarization selection lens420.

The see-through type display apparatus1012of the example embodiment is different from the see-through type display apparatus1000ofFIG. 4in that the polarization selection lens420is controlled according to the external signal SG and refractive power with respect to a predetermined polarization is adjusted.

Referring toFIG. 19, refractive power of the polarization selection lens420with respect to the light L1of the first image in the first polarization is adjusted by an effective lens surface ELS that is variable. According to a change in the shape of the effective lens surface ELS, a focusing location of the light L1of the first image in the first polarization ⊙ state incident on the polarization selection lens420is adjusted to P1or P2.

The polarization selection lens420may be one of polarization selection lens PSL1, PSL2, PSL3, PSL4, or PSL5illustrated with reference toFIGS. 3A to 3E, or a modified example thereof, and the effective lens surface ELS is conceptually shown in order to describe the refractive power varying operation. In order to transform the effective lens surface ELS, an optical anisotropic material that may be electrically controlled, e.g., a liquid crystal, may be used or a meta lens including a material, an optical property of which is changed electrically, and sub-wavelength nanostructures may be used.

Similarly to the see-through type display apparatus1010ofFIG. 15and the see-through type display apparatus1011ofFIG. 17, the see-through type display apparatus1012of the example embodiment may control the refractive power of the polarization selection lens420taking into account the expression of multi-depth and/or correction of eyesight of the observer.

FIG. 19illustrates variation in the refractive power with respect to the light L1of the first image in the first polarization state, but the variation of the polarization selection lens420is not limited thereto. For example, in addition to an operation of transmitting the light of the second image in the second polarization without refracting operation to the light, the polarization selection lens420may be controlled to have little refractive power with respect to the light of the second image. In this case, the operation for correcting eyesight of the observer may be performed accurately, that is, the eyesight correction may be applied to a real image, as well as the image generated by the display device, and thus, a clear image may be provided to the observer.

FIG. 20is a block diagram of a see-through type display apparatus1013according to another example embodiment.

The see-through type display apparatus1013includes a display device1100, an optical coupler1300, a variable optical device1200, a polarization selection optical system1400, and a processor1700.

The display device1100may form a first image and is substantially the same as the display device100illustrated in the above-described example embodiments.

The optical coupler1300combines a first image from the display device1100with a second image and outputs the first image in a first polarization and outputs the second image in a second polarization that is different from the first polarization. The second image is provided from a path different from the path of the first image that is generated by the display device1100. For example, the second image may be a real world scene, but the second image is not limited thereto. The optical coupler1300may adopt the optical coupler CB1, CB2, CB3, CB4, or CB5described above, a combination thereof, or a modified example thereof.

The variable optical device1200may be arranged on an optical path along which the first image proceeds towards the polarization selection optical system1400. According to an example embodiment, the variable optical device1200may include the variable lens520(FIG. 15) or the variable mirror530(FIG. 17) capable of adjusting the refractive power thereof by varying a location thereof on the optical axis or varying a curved surface thereof.

The polarization selection optical system1400applies different refractive powers with respect to the light of the first polarization and the light of the second polarization, that is, may focus the first image in the first polarization and transmit the second image in the second polarization without refraction operation. The polarization selection optical system1400may adopt the polarization selection lens400having the different refraction operations with respect to two linear polarizations that are perpendicular to each other, or the polarization selection lens410having different refraction operations with respect to two circular polarizations in opposite directions and the quarter-wave plate420.

The processor1700may control the variable optical device1200. The processor1700may control the variable optical device1200for expressing multi-depth. The processor1700may set a range of controlling the variable optical device1200according to depth information of the first image, and accordingly, may control the variable optical device1200. The processor1700may execute a multi-focusing module1710for the above control.

The processor1700may adjust a range of controlling the variable optical device1200according to eyesight information of the observer by executing an eyesight correction module1720, and may control the variable optical device1200according to the range.

The processor1700may also control the variable optical device1200, taking into account both the expression of multi-depth and correction of eyesight of the observer.

The see-through type display apparatus1013may provide the observer with a high-quality combined image that is obtained taking into account the multi-depth expression and/or the eyesight information of the observer.

FIG. 21is a block diagram of a see-through type display apparatus1014according to another example embodiment.

The see-through type display apparatus1014includes the display device1100, the optical coupler1300, a variable polarization selection optical system1500, and a processor1800.

The display device1100may form a first image, and is substantially the same as the display device100illustrated in the above-described example embodiments.

The optical coupler1300combines a first image from the display device1100with a second image from a different path from that of the first image and outputs the first image in a first polarization and the second image in a second polarization that is different from the first polarization.

The variable polarization selection optical system1500applies different refractive powers with respect to light of the first polarization and light of the second polarization, and the refractive power of the variable polarization selection optical system1500may be controlled. The variable polarization selection optical system1500may have first refractive power with respect to the light of the first polarization and second refractive power with respect to the light of the second polarization, and the first and second refractive powers may be adjusted according to a control signal. The variable polarization selection optical system1500may include the polarization selection lens420having the adjustable refractive power or a modified structure thereof, as described above with reference toFIG. 18.

The processor1800may set a range of controlling the variable polarization selection optical system1500according to depth information of a first image, and may control the variable polarization selection optical system1500according to the range. The processor1800, that is, controls a range of controlling the first refractive power with respect to the light of the first polarization, and adjusts the first refractive power according to the range. To do this, the processor1800may execute a multi-focusing module1810.

The processor1800may set a range of controlling the variable polarization selection optical system1500according to eyesight information of the observer, and may control the variable polarization selection optical system1500according to the range. The processor1800, that is, controls a range of controlling the second refractive power with respect to the light of the second polarization, and adjusts the second refractive power according to the range. The processor1800may adjust both the first refractive power with respect to the light of the first polarization and the second refractive power with respect to the light of the second polarization, in consideration of the eyesight information of the observer. To do this, the processor1800may execute an eyesight correction module1820.

The processor1800may also control the variable polarization selection optical system1500, taking into account the multi-depth expression and the eyesight correction of the observer. For example, the first refractive power and/or the second refractive power may be adjusted.

The see-through type display apparatus1014may provide the observer with a high-quality combined image that is obtained taking into account the multi-depth expression and/or the eyesight information of the observer.

FIG. 22is a block diagram of a see-through type display apparatus1015according to another example embodiment.

The see-through type display apparatus1015of the example embodiment is different from the see-through type display apparatus1014ofFIG. 21in that the display device1100and the variable optical device1200are further included and a processor1900controls the variable polarization selection optical system1500and the variable optical device1200.

The variable optical device1200may be arranged on an optical path along which the first image proceeds towards the polarization selection optical system1500. The variable optical device1200may adopt the variable lens520or the variable mirror530capable of adjusting the refractive power thereof by varying the location thereof on the optical axis or by using the variable curved surface.

The processor1900may set a range of controlling the variable polarization selection optical system1500according to depth information of a first image, and may control the variable polarization selection optical system1500and/or the variable optical device1200according to the range. That is, the processor1900may set, with respect to the variable polarization selection optical system1500, the range of controlling the first refractive power with respect to the light of the first polarization, and accordingly may adjust the first refractive power according to the range. Alternatively, the processor1900may set a range of controlling the variable optical device1200and control the variable optical device1200according to the range. To do this, the processor1900may execute a multi-focusing module1910.

The processor1900may set a range of controlling the variable polarization selection optical system1500according to the eyesight information of the observer, and may control the variable polarization selection optical system1500and/or the variable optical device1200according to the range. That is, the processor1900may set, with respect to the variable polarization selection optical system1500, the range of controlling the second refractive power with respect to the light of the second polarization, and accordingly may adjust the second refractive power according to the range. Alternatively, the processor1900may set a range of controlling the variable optical device1200and control the variable optical device1200according to the range. The processor1900may adjust both the first refractive power with respect to the light of the first polarization and the second refractive power with respect to the light of the second polarization, in consideration of the eyesight information of the observer. To do this, the processor1900may execute an eyesight correction module1920.

The processor1900may also control the variable polarization selection optical system1500and the variable optical device1200, taking into account the multi-depth expression and the eyesight correction of the observer.

The see-through type display apparatus1015may provide the observer with a high-quality combined image that is obtained taking into account the multi-depth expression and/or the eyesight information of the observer.

The above-described see-through type display apparatus may display the image formed by the display device and the real world image to the observer, and thus, may be applied to implement augmented reality (AR).

AR may further improve the reality effect by combining the real world environment with a virtual object or virtual information. For example, additional information about the environment provided by the real world at the location of the observer may be generated by an imaging unit and provided to the observer. The AR display may be applied to a ubiquitous environment or internet of things (IoT) environment.

The real world image is not limited to the real environment, but for example, may be an image generated by another imaging apparatus. Therefore, the see-through type display apparatus may be applied as a multi-image display apparatus capable of displaying two images together.

The see-through type display apparatus may be configured as a wearable type. All or some components in the see-through type display apparatus may be configured as a wearable type.

For example, the see-through type display apparatus may be applied as a head mounted display (HMD). Also, embodiments are not limited thereto, and the 3D image display apparatus may be applied as a glasses-type display or a goggle-type display.

The see-through type display apparatus may operate in connection with other electronic devices such as a smartphone, etc. For example, a controller for driving the see-through type display apparatus may be provided in a smartphone. Moreover, the see-through type display apparatus may be included in the smartphone so that the smartphone itself may be used as the see-through type display apparatus.

The see-through type display apparatus may reduce a volume of an optical system, and may be applied as a wearable device with improved wearability.

The see-through type display apparatus may provide a combined image, and thus, may provide an AR display.

The see-through type display apparatus may provide a combined image of high image quality, which is obtained taking into account the multi-depth expression and/or eyesight of the observer.