OPTICAL DEVICE FOR EXIT PUPIL EXPANSION (EPE) AND DISPLAY APPARATUS INCLUDING THE OPTICAL DEVICE

An optical device for exit pupil expansion (EPE) for improving a field of view (FOV) and luminance uniformity, and a display apparatus including the same are provided. The optical device includes: an input part into which a virtual image is input; and an EPE part configured to receive the virtual image from the input part, perform one-dimensional (1D) EPE and two-dimensional (2D) EPE to combine the virtual image with an external real image, and output the combined image.

BACKGROUND

The inventive concept relates to an optical device expanding an exit pupil or an eye box and a display apparatus including the optical device.

A visual optical device such as an augmented reality (AR) device or a lens of an optical device is progressively improving. The most important characteristic parameters of the visual optical element are the size of a field of view (FOV) and the size of an eye box. However, it is not easy to implement a visual optical device having a wide FOV and a large eye box while maintaining high image quality, resolution, and luminance. Accordingly, for the expansion of the eye box, an exit pupil expansion (EPE) technique using a diffractive element or an optical beam expansion technique using a translucent mirror may be used to improve image quality, resolution and luminance.

SUMMARY

The inventive concept provides an optical device for exit pupil expansion (EPE) capable of improving a field of view (FOV) and luminance uniformity while embodying eye box expansion, and a display apparatus including the optical device.

The inventive concept is not limited to the above described concepts, and other features, aspects and advantages will be apparent to those skilled in the art from the following description.

According to an embodiment, there is provided an optical device for exit pupil expansion (EPE) including: an input part into which a virtual image is input; and an EPE part configured to receive the virtual image from the input part, perform one-dimensional (1D) EPE and two-dimensional (2D) EPE to combine the virtual image with an external real image, and output the combined image.

According to an embodiment, there is provided a display apparatus including: an image generator configured to generate a virtual image; and an optical device for exit pupil expansion (EPE) configured to receive the virtual image and perform the EPE to combine the virtual image with an external real image. The optical device includes: an input part into which the virtual image is input; and an EPE part configured to receive the virtual image from the input part, perform one-dimensional (1D) EPE and two-dimensional (2D) EPE to combine the virtual image with the external real image, and output the combined image.

According to an embodiment, there is provided a display apparatus including: an image generator configured to generate a virtual image; an optical device for exit pupil expansion (EPE) configured to receive the virtual image and perform the EPE to combine the virtual image with an external real image; and a body onto which the image generator and the optical device for EPE are mounted. The optical device for EPE includes: an input part into which the virtual image is input; and an EPE part configured to receive the virtual image from the input part, perform one-dimensional 1D EPE and two-dimensional (2D) EPE to combine the virtual image with the external real image, and output the combined image.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In the drawings, like numerals denote like elements and redundant descriptions thereof will be omitted.

FIGS.1A to1Dare plan views and enlarged plan views of an optical device for exit pupil expansion (EPE) according to an embodiment.FIGS.1B and1Care enlarged plan views of a one-dimensional (1D) EPE area and a two-dimensional (2D) EPE area of the optical device for EPE ofFIG.1A, respectively, andFIG.1Dis an enlarged plan view of a rhombus grating portion of the 2D EPE area.

Referring toFIGS.1A and1D, an optical device for EPE100may include an input part110and an EPE part150. The optical device for EPE100may be, for example, a coupler of a waveguide type. Accordingly, the input part110and the EPE part150may be embodied through a diffraction grating formed in a waveguide101(seeFIG.2A).

The waveguide101is an optical waveguide that transmits light, and may include a material transparent to visible light. For example, the waveguide101may include a material such as glass, poly methyl methacrylate (PMMA), or polydimethylsiloxane (PDMS). However, a material of the waveguide101is not limited to these materials. Also, the waveguide101may include a flat plate shape having flat surfaces. The waveguide101may include a first surface101a(seeFIG.5) and a second surface101b(seeFIG.5) that is opposite from the first surface101a. The diffraction grating may be formed on the first surface101a of the waveguide101. However, a surface on which the diffraction grating is formed is not limited to the first surface101a. Total reflection may occur at the first and second surfaces101aand101bof the waveguide101. In addition, light may be input or output to or from a diffraction grating portion. That is, light may be input or output to or from a diffraction grating portion through in-coupling and out-coupling of light. Also, light may be diffracted in the diffraction grating portion to achieve EPE.

The input part110may be a portion into which external light is input. That is, light may be input into the waveguide101through in-coupling by the diffraction grating. For example, the input part110may be embodied through a line-shaped diffraction grating, that is, a line grating115, formed on the first surface101aof the waveguide101. Specifically, the input part110may include the line grating115that allows light incident in a direction perpendicular to the first surface101aof the waveguide101to travel into the waveguide101in a direction parallel to the first surface101a.

The line grating115of the input part110will be described in more detail hereafter. For example, when the direction perpendicular to the first surface101aof the waveguide101is referred to as a third direction (z direction), the input part110may include a line-shaped diffraction grating, that is, the line grating115, extending in a second direction (y direction) and having a certain pitch in a first direction (x direction). External light may be input to the input part110in the third direction (z direction), and bent through the line grating115to travel into the waveguide101in the first direction (x direction). In addition, the line grating115of the input part110may have a shape similar to that of a line grating125of a 1D EPE area120of the EPE part150. Thus, a cross-sectional shape of the line grating115of the input part110may be understood as a cross-sectional shape of the line grating125of 1D EPE areas120-1and120-2(also referred to as a first 1D EPE area120-1and a second 1D EPE area120-2, respectively) ofFIGS.2A to2C.

The input part110may be embodied through other optical devices as well as a line grating. For example, the input part110may include a mirror, a prism, or the like.

The EPE part150may include the 1D EPE area120and a 2D EPE area130. The 1D EPE area120may be an area where 1D EPE is realized (or performed). The 1D EPE may mean one-dimensionally expanding of an exit pupil by outputting light in such a way that light travels through the waveguide101in one direction, wherein a part of the light is output due to out-coupling by the diffraction grating and another part thereof travels therethrough. Because 1D EPE is known technology, a detailed description thereof is omitted. However, an output by 1D EPE from the 1D EPE area120according to an embodiment may be output to the 2D EPE area130rather than being output to the outside of the waveguide101. In addition, 1D EPE may be realized through out-coupling by a translucent mirror, a holographic optical element (HOE), or the like as well as the diffraction grating.

The 1D EPE area120may be arranged on both sides of the input part110in the first direction (x direction). For example, the 1D EPE area120may include the first 1D EPE area120-1on a right side of the input part110in the first direction (x direction) and the second 1D EPE area120-2on a left side of the input part110. According to an embodiment, the 1D EPE area120may be arranged at one side of the input part110in the first direction (x direction).

Similar to the input part110, the 1D EPE area120may include a line-shaped diffraction grating, that is, the line grating125. The line grating125may include a line-shaped protrusion122and a line-shaped space124. The line grating125in the 1D EPE area120extends in a slope direction SD having a slope of 45° with respect to the first direction (x direction), and may have a certain pitch in a vertical slope direction SDp perpendicular to the slope direction SD. Here, the slope direction SD and the vertical slope direction SDp may be defined on a plane by the first direction (x direction) and the second direction (y direction), respectively, and the slope direction SD and the vertical slope direction SDp may be perpendicular to the third direction (z direction). According to an embodiment, the line grating125may extend with a slope greater than or less than 45° with respect to the first direction (x direction). The cross-sectional shape of the line grating125is described in more detail with reference toFIGS.2A to2C.

As indicated by an arrow ofFIG.1A, light from the outside is input to the waveguide101through the input part110, wherein the light is bent by the line grating115in the input part110and travels to both sides of the first direction (x direction) to enter the 1D EPE area120. Also, the light is output through out-coupling while 1D EPE is realized in the 1D EPE area120, and enters the 2D EPE area130.

The 2D EPE area130may be an area where 2D EPE is realized. 2D EPE may mean two-dimensionally expanding an exit pupil by outputting light in such a way that light travels through the waveguide101while spreading in a two-dimensional direction, wherein a part of the light is output due to out-coupling by the diffraction grating and another part thereof travels therethrough. Because 2D EPE is also known technology, a detailed description thereof is omitted. Also, 2D EPE may be realized through out-coupling by a translucent mirror, a holographic optical device, or the like as well as the diffraction grating.

The 2D EPE area130may be arranged adjacent to the input part110and the 1D EPE area120in the second direction (y direction). For example, the 2D EPE area130may be located adjacent to the 1D EPE area120in the second direction (y direction), which is a direction in which light is output from the 1D EPE area120, and may be located adjacent to the input part110in the second direction (y direction). Thus, light that is output while 1D EPE is realized in the 1D EPE area120may be incident on the 2D EPE area130. A gap area GA may be arranged between the 1D EPE area120and the 2D EPE area130and between the input part110and the 2D EPE area130. In the gap area GA, only the waveguide101exists and a diffraction grating may not be formed.

Referring toFIG.1C, a rhombus grating135may be arranged in the 2D EPE area130. The rhombus grating135may include rhombus-shaped protrusions132and a space134between the protrusions132. Also, the rhombus grating135may have a structure in which the rhombus-shaped protrusions132are arranged in a two-dimensional array shape in a first slope direction SD1and a second slope direction SD2and spaced apart from each other through the space134. Here, the first slope direction SD1and the second slope direction SD2may be defined on the x-y plane, and thus the first slope direction SD1and the second slope direction SD2may be perpendicular to the third direction (z direction). Also, the first slope direction SD1and the second slope direction SD2may correspond to directions in which sides of a rhombus of a protrusion132extend. For example, as shown inFIG.1D, the first slope direction SD1may have a first angle θ1 in a clockwise direction with respect to the second direction (y direction), and the second slope direction SD2may have a first angle θ1 in a counterclockwise direction with respect to the second direction (y direction). The first angle may be less than 45°. According to an embodiment, the first angle θ1 may be greater than 45°. When the first angle θ1 is greater than 45°, a rhombus may have a shape elongated in the first direction (x direction). A cross-sectional shape of the rhombus grating135is described in more detail with reference toFIGS.3A and3B.

As indicated by an arrow ofFIG.1D, light Ly may travel in the second direction (y direction) in the 2D EPE area130, and light Ls may travel while spreading with a certain angle with respect to the second direction (y direction), for example, a second angle θ2. For example, the second angle θ2 may be greater than the first angle θ1 of the rhombus grating135. The second angle θ2 may be variously changed according to a structure of the rhombus grating135. Light may be output in the third direction (z direction) through out-coupling while 2D EPE is realized in the 2D EPE area130. Here, the third direction (z direction) is a direction perpendicular to the first direction (x direction) and the second direction (y direction), that is, a direction perpendicular to a paper surface. Also, a direction of light output from the 2D EPE area130may be opposite to a direction of light input to the input part110. However, according to an embodiment, the line grating115of the input part110and the rhombus grating135of the 2D EPE area130may be formed on opposite surfaces of the waveguide101, and thus, the direction of light output from the 2D EPE area130and the direction of light input to the input part110may be identical to each other.

External light may be directly input to the 2D EPE area130. Accordingly, light directly input from the outside and light input through the input part110may be combined in an output from the 2D EPE area130. For reference, light or an image input through the input part110may correspond to virtual light or a virtual image, and light or an image directly input to the 2D EPE area130may correspond to real light or a real image. A combination of the virtual image and the real image is described in more detail with reference toFIG.5. Based on a light coupling function in the 2D EPE area130, the optical device for EPE100according to an embodiment may correspond to a coupler having an EPE structure. Also, the optical device for EPE100may be referred to as a coupler having a double EPE structure in which 1D EPE and 2D EPE are overlapped in the EPE part150.

According to an embodiment, the EPE part150may include the 1D EPE area120and the 2D EPE area130, and 1D EPE and 2D EPE may be overlapped in the EPE part150. Thus, the optical device for EPE100may expand a field of view (FOV) based on 1D EPE and 2D EPE, improve luminance uniformity of an entire output image, and improve luminance change and FOV uniformity for each position of an eye in an eye box. In the optical device for EPE100, FOV expansion, luminance uniformity improvement, and luminance change and FOV uniformity improvement for each position of the eye are described in more detail with reference toFIGS.6A to11C.

FIGS.2A to2Care cross-sectional views taken along portion I-I′ ofFIG.1B, according to various embodiments, andFIGS.3A and3Bare cross-sectional views taken along portions II-II′ and III-III′ ofFIG.1C, respectively. Descriptions that have been provided above with reference toFIGS.1A to1Dmay be briefly described or omitted.

Referring toFIG.2A, the 1D EPE area120of the EPE part150may be embodied through the line grating125formed on a surface of the waveguide101. The line grating125may include line-shaped protrusions122and the space124between the protrusions122. Similar to the protrusion122, the space124may have a line shape. As described above, the line grating125may extend in the slope direction SD having a slope of 45° with respect to the first direction (x direction), and the 1D EPE area120ofFIG.2Amay correspond to a cross-section perpendicular to the slope direction SD. The vertical slope direction SDp may refer to a direction perpendicular to the slope direction SD. The slope direction SD and the vertical slope direction SDp may be defined on the x-y plane, and may be perpendicular to the third direction (z direction).

A grating pattern of the line grating125may serve as a diffraction grating to diffract incident light. That is, the line grating125may change a traveling direction of light by diffracting light incident at a specific angle to generate destructive interference and constructive interference according to a width and height of the protrusion122, a pitch of the grating pattern, and the like. As shown inFIG.2A, a cross-section of the protrusion122may have a rectangular shape, and the protrusion122may have a first width W1 in the vertical slope direction SDp and a first height H1 in the third direction (z direction). Also, the grating pattern of the line grating125may have a first pitch P1 in the vertical slope direction SDp. In the line grating125, the first width W1 and the first height H1 of the protrusion122and the first pitch P1 of the grating pattern may be appropriately selected and formed according to a wavelength or intensity of light.

Referring toFIG.2B, a 1D EPE area120aof the EPE part150may be embodied through a line grating125aformed on a surface of the waveguide101. Similar to the line grating125ofFIG.2A, the line grating125amay include line-shaped protrusions122aand a space124abetween the protrusions122a. Also, the line grating125amay extend in the slope direction SD.

As shown inFIG.2B, unlike the line grating125ofFIG.2A, the line grating125amay include a protrusion122ahaving a cross-section in a parallelogram shape. For example, the protrusion122amay be slanted at a certain angle with respect to the waveguide101. The protrusion122amay have a second width W2 in the vertical slope direction SDp and a second height H2 in the third direction (z direction). Also, a grating pattern of the line grating125amay have a second pitch P2 in the vertical slope direction SDp. Even in the line grating125a, the second width W2 and the second height H2 of the protrusion122aand the second pitch P2 of the grating pattern may be appropriately selected and formed according to a wavelength or intensity of light.

Referring toFIG.2C, a 1D EPE area120bof the EPE part150may be embodied through a line grating125bformed on a surface of the waveguide101. Similar to the line grating125ofFIG.2A, the line grating125bmay include line-shaped protrusions122band a space124bbetween the protrusions122b. Also, the line grating125bmay extend in the slope direction SD.

As shown inFIG.2C, unlike the line grating125ofFIG.2A, the line grating125bmay include a protrusion122bhaving a cross-section in a serrated shape. For example, a cross-section of the protrusion122bmay have a triangular shape. The protrusion122bmay have a third height H3 in the third direction (z direction). Also, a grating pattern of the line grating125bmay have a third pitch P3 in the vertical slope direction SDp. As the protrusion122bhas a serrated shape, the protrusion122bmay form an angle α with another protrusion122b. In the line grating125b, the angle α and the third height H3 of the protrusion122band the third pitch P3 of the grating pattern may be appropriately selected and formed according to a wavelength or intensity of light.

Referring toFIGS.3A and3B, the 2D EPE area130of the EPE part150may be embodied through the rhombus grating135formed on a surface of the waveguide101. The rhombus grating135may include the rhombus-shaped protrusions132and the space134between the protrusions132. The protrusions132may be arranged in the first slope direction SD1and the second slope direction SD2and spaced apart from each other through the space134.

The 2D EPE area130ofFIG.3Amay correspond to a cross-section perpendicular to a first vertical slope direction SD1p. The first vertical slope direction SD1pmay be defined on the x-y plane, perpendicular to the first slope direction SD1, and perpendicular to the third direction (z direction). In the rhombus grating135, a protrusion132may have a fourth width W4 in the first slope direction SD1and a fourth height H4 in the third direction (z direction). Also, a grating pattern of the rhombus grating135may have a fourth pitch P4 in the first slope direction SD1.

The 2D EPE area130ofFIG.3Bmay correspond to a cross-section perpendicular to a second vertical slope direction SD2p. The second vertical slope direction SD2pmay also be defined on the x-y plane, perpendicular to the second slope direction SD2, and perpendicular to the third direction (z direction). In the rhombus grating135, the protrusion132may have the fourth width W4 in the second slope direction SD2and the fourth height H4 in the third direction (z direction). Also, the grating pattern of the rhombus grating135may have the fourth pitch P4 in the second slope direction SD2. Because the protrusion132has a rhombus shape, a width of the protrusion132in the first slope direction SD1and the second slope direction SD2may be equal to the fourth width W4, and a pitch of the grating pattern may be equal to the fourth pitch P4. In the rhombus grating135, the fourth width W4 and the fourth height H4 of the protrusion132and the fourth pitch P4 of the grating pattern may be appropriately selected and formed according to a wavelength or intensity of light.

InFIG.3A, a dashed line may correspond to a side surface of the protrusion132that is visible when a cross-section of the 2D EPE area130is viewed in the first vertical slope direction SD1p. Also, a dashed line ofFIG.3Bmay also correspond to a side surface of the protrusion132that is visible when a cross-section of the 2D EPE area130is viewed in the second vertical slope direction SD2p.

FIGS.4A and4Bare enlarged plan views of the 2D EPE area of the optical device for EPE ofFIG.1A, and may correspond toFIG.1C. Descriptions that have already been given with reference toFIGS.1A to3Bare briefly given or omitted.

Referring toFIG.4A, according to an embodiment, a 2D EPE area130aof the EPE part150may be embodied through a deformed rhombus grating135aformed on a surface of the waveguide101. Similar to the rhombus grating135ofFIG.1C, the deformed rhombus grating135amay include protrusions132aand a space134abetween the protrusions132a. In the deformed rhombus grating135a, a protrusion132amay have a deformed rhombus shape in which a notch N is formed at both vertices of a rhombus in the first direction (x direction). InFIG.4A, although a notch N is shown in the form of a straight line, the notch N is not limited thereto, and may have various shapes such as a semicircle, a V shape, and the like.

According to an embodiment, in the deformed rhombus grating135a, a protrusion132amay have a deformed rhombus shape in which a notch N is formed at both vertices of a rhombus in the second direction (y direction). Also, a protrusion132amay have a deformed rhombus shape in which notches N are formed at all four vertices of a rhombus.

Referring toFIG.4B, according to an embodiment, a 2D EPE area130bof the EPE part150may be embodied through a circular grating135bformed on a surface of the waveguide101. The circular grating135bmay include circular protrusions132band a space134bbetween the protrusions132b. Also, the circular grating135bmay have a structure in which the circular protrusions132bare arranged in a two-dimensional array shape in the first slope direction SD1and the second slope direction SD2and spaced apart from each other through the space134b.

More specifically, the protrusions132bmay be arranged in the first slope direction SD1and spaced apart from each other through the space134b. Also, the protrusions132bmay be arranged in the second slope direction SD2and spaced apart from each other through the space134b. Here, the first slope direction SD1and the second slope direction SD2may be directions in which the protrusions132bare arranged in a line. The first slope direction SD1and the second slope direction SD2may be substantially identical to the first slope direction SD1and the second slope direction SD2in the rhombus grating135ofFIG.1C. That is, the protrusions132of the rhombus grating135ofFIG.1Cmay also be arranged in each of the first slope direction SD1and the second slope direction SD2and spaced apart from each other through the space134.

Hereinabove, although some shapes of the diffraction grating of the 2D EPE area are provided as examples, a shape of the diffraction grating formed in the 2D EPE area is not limited to the above-described shapes. For example, in the optical device for EPE, various shapes of diffraction gratings may be formed in the 2D EPE area, and light may spread two-dimensionally in the waveguide101and may be output to the outside while 2D EPE is achieved through a diffraction grating. Also, in the optical device for EPE, a width and a height of a protrusion of the diffraction grating of the 2D EPE area and a pitch of a grating pattern may be appropriately selected and formed according to a wavelength or intensity of light.

FIG.5is a conceptual view for explaining an operation of the optical device for the EPE ofFIG.1A. Descriptions that have been provided with reference toFIGS.1A to4Bmay be briefly given or omitted.

Referring toFIG.5, in the optical device for EPE100, a virtual image IMG1 from an image generator200(seeFIG.12) may be input to the input part110in the third direction (z direction). The virtual image IMG1 may be bent in the first direction (x direction) through in-coupling by a line-shaped diffraction grating of the input part110, that is, the line grating115, to enter the 1D EPE area120. The 1D EPE area120may be arranged on both sides of the input part110in the first direction (x direction). For reference, asFIG.5is shown in a cross-sectional shape, the 1D EPE area120is not shown to be distinct from the input part110, but is indicated only with reference numerals “110/120”. Also, the line grating115/125is simplified and conceptually expressed, and a shape and extension direction of the line grating115/125may be different from a shape and extension direction of an actual line grating115/125.

The virtual image IMG1 that has entered the 1D EPE area120may be output in the second direction (y direction) through out-coupling while 1D EPE is realized by the line grating125of the 1D EPE area120to enter the 2D EPE area130, as shown by fine arrows. The 2D EPE area130may have a flat shape extending in the first direction (x direction) and the second direction (y direction). The rhombus grating135may be formed in the 2D EPE area130. AsFIG.5is shown in a cross-sectional shape, the 2D EPE area130may be shown in a shape extending only in the second direction (y direction). Also, the rhombus grating135is simplified and conceptually expressed, and a shape and extension direction of the rhombus grating135may be different from a shape and extension direction of an actual rhombus grating135.

The virtual image IMG1 that has entered the 2D EPE area130may be output in the third direction (z direction) through out-coupling while 2D EPE is realized by the rhombus grating135of the 2D EPE area130, as shown by fine arrows. As shown inFIG.5, when an eye E of an observer (or a user) is located in a lower portion in the third direction (z direction), the virtual image IMG1 may be output from the 2D EPE area130and provided to the eye E of the observer. Also, the virtual image IMG1 may be output while 2D EPE is realized in the 2D EPE area130. Accordingly, as long as the eye E of the observer is located within a width of 2D EPE, the observer may see the entire virtual image IMG1. Due to the cross-sectional shape ofFIG.5, only a width EPEy of EPE in the second direction (y direction) is indicated.

The rhombus grating135of the 2D EPE area130acts as a diffraction grating only with respect to light incident obliquely to a surface and transmits light incident vertically thereto. Thus, as shown inFIG.5, a real image IMG2 incident onto the 2D EPE area130from an upper portion in the third direction (z direction) may pass through the rhombus grating135and may be provided to the eye E of the observer. As a result, a combined image of the virtual image IMG1 and the real image IMG2 is provided to the eye E of the observer, and the observer may see the combined image. Thus, the optical device for the EPE100according to an embodiment corresponds to a coupler having a waveguide-type EPE structure, and may be used in an augmented reality (AR) or mixed reality (MR) device.

FIG.6Ais a conceptual view of a traveling direction of vertically incident light in the optical device for EPE, andFIGS.6B and6Care simulation images showing a comparison of luminance uniformity of emitted light with respect to vertically incident light in an optical device for EPE of the related art and the optical device for EPE of the one or more embodiments, whereinFIG.6Brelates to the optical device for EPE of the related art, andFIG.6Crelates to the optical device for EPE according to the one or more embodiments.

Referring toFIG.6A, in the optical device for EPE100according to an embodiment, vertically incident light Lo is incident upon the input part110, and may be output to the outside through out-coupling while EPE is realized through the 1D EPE area120and the 2D EPE area130of the EPE part150. The 1D EPE is realized in the 1D EPE area120and the 2D EPE is realized in the 2D EPE area130, such that in the optical device for EPE100of the present embodiment, a duplicate EPE may be realized in the EPE part150.

In the case of the optical device for EPE of the related art, only 2D EPE may be realized. In such optical device for EPE of the related art, a structure of a 1D EPE area + a 1D EPE area is formed in an EPE part to realize 1D EPE in the first direction (x direction) and the second direction (y direction) sequentially, or a structure of a 2D EPE area is formed in the EPE part to realize EPE in the first direction and the second direction at the same time. Even in the optical device for EPE of the related art, vertically incident light is incident upon an input part and may be output to the outside through out-coupling while 2D EPE is realized in the EPE part.

Referring toFIG.6B, in the case of the optical device for EPE of the related art, emitted light may be two-dimensionally output while 2D EPE is realized, and distances between the emitted light may be far apart and luminance of the emitted light may be low. Also, luminance of the output light of an outer area may be lower than luminance of the output light at a central line portion. Accordingly, it may be seen that luminance uniformity of the entire output light is low in the optical device for EPE of the related art.

In contrast, referring toFIG.6C, in the case of the optical device for EPE100according to the one or more embodiments of the disclosure, emitted light is output two-dimensionally, distances between the emitted light may be close together, and luminance may be high. Also, in both a central area and an outer area, luminance of the output light may be high and substantially uniform. Thus, it may be seen that luminance uniformity of the entire output light is high in the optical device for EPE100according to the one or more embodiments.

FIGS.7A and7Bare 2D input images andFIG.7Cis a conceptual view of a view angle of a 2D input image in the optical device for EPE according to an embodiment.

Referring toFIGS.7A to7C, a 2D input image 2Di1 ofFIG.7Amay have a square shape, and in terms of an angle of view, may have vertical and horizontal angles of view of about 43.1° and a diagonal angle of view of about 58.3°. Here, the angle of view may refer to a field of view of a scene captured by a camera or seen by an observer’s eye. InFIG.7C, a form in which the 2D input image 2Di1 ofFIG.7Ais incident upon the input part110of the optical device for EPE100is shown in terms of an angle of view. A 2D input image 2Di2 ofFIG.7Bmay have a rectangular shape, and in terms of an angle of view, may have a vertical angle of view of about 26.6°, a horizontal angle of view of about 48.8°, and a diagonal angle of view of about 56°.

For reference, the 2D input image 2Di1 ofFIG.7Amay be used for comparison of luminance uniformity inFIGS.8A and8B, and the 2D input image 2Di2 ofFIG.7Bmay be used for comparison of a luminance change and FOV uniformity according to a position of an eye in an eye box inFIGS.9A to11C. The 2D input image 2Di1 ofFIG.7Aand the 2D input image 2Di2 ofFIG.7Bmay each correspond to a virtual image.

FIGS.8A and8Bare simulation images showing a comparison of luminance uniformity of an output image with respect to a 2D input image in an optical device for EPE of the related art and the optical device for EPE of the one or more embodiments, respectively.FIG.8Arelates to the optical device for EPE of the related art, andFIG.8Brelates to the optical device for EPE of the one or more embodiments. However, the optical device for EPE of the related art is the same as that described with reference toFIGS.6A to6C.

Referring toFIGS.8A and8B, as shown inFIG.8A, in the optical device for EPE of the related art, a 2D output image with respect to the 2D input image 2Di1 ofFIG.7Amay have high luminance in a central area and low luminance in an outer area. Thus, it may be seen that luminance uniformity of the entire 2D output image is low in the optical device for EPE of the related art.

In contrast, as shown inFIG.8B, in the optical device for EPE100of the one or more embodiments, a 2D output image with respect to the 2D input image 2Di1 ofFIG.7Amay have high luminance in both a central area and an outer area. Also, the 2D output image may appear almost similarly in the central area and the outer area except for outermost portions. Thus, it may be seen that luminance uniformity of the entire 2D output image is high in the optical device for EPE100of the one or more embodiments.

It may be seen that the optical device for EPE100of the one or more embodiments may perform eye box expansion and FOV expansion and has higher luminance and uniformity compared to the optical device for EPE of the related art. That is, the eye box expansion and the FOV expansion according to the one or more embodiments may yield high luminance and luminance uniformity of the output light with respect to the vertically incident light inFIG.6Cand high luminance and luminance uniformity of the 2D output image with respect to the 2D input image inFIG.8B. Here, an eye box is an area where an entire image may be seen when an observer’s eye is located in the eye box, and is substantially the same concept as an exit pupil, and the eye box may be expanded through EPE.

FIGS.9A to11Care conceptual views of positions of an eye in an eye box, and are images showing a comparison of a luminance change and FOV uniformity in an optical device for EPE of the related art and the optical device for EPE of the one or more embodiments, corresponding to each of the positions of the eye. Here,FIGS.9A,10A, and11Ashow eyes at different positions in the eye box,FIGS.9B,10B, and11Bshow a luminance change and FOV uniformity in the optical device for EPE of the related art in response to each eye position, and

FIGS.9C,10C, and11Cshow a luminance change and FOV uniformity in the optical device for EPE of the one or more embodiments with respect to each eye position. The optical device for EPE of the related art is the same as that described with reference toFIGS.6A to6C.

Referring toFIG.9A, a rectangle may correspond to the eye box, and small circles may correspond to eye positions. InFIG.9A, a central small circle among the small circles is hatched, which may mean that an eye is located in the center of the eye box. As shown inFIG.9B, even when the eye is in the center of the eye box, lower corner sides of a 2D output image is partially cut and may not be visible in the optical device for EPE of the related art. In other words, it may be seen that an FOV of the optical device for EPE of the related art is small. Also, in the case of the optical device for EPE of the related art, luminance is low adjacent to a cut portion.

In contrast, as shown inFIG.9C, when the eye is in the center of the eye box, an entire 2D output image is clear in the optical device for EPE100of the one or more embodiments. Thus, it may be seen that an FOV of the optical device for EPE100of the one or more embodiments is large. Also, in the case of the optical device for EPE100, luminance of the entire 2D output image is high.

Referring toFIGS.10A to10C, inFIG.10A, as a small circle in the lower center among small circles is hatched, it may be seen that an eye is located in the lower center of the eye box. As shown inFIG.10B, when the eye is in the lower center of the eye box, because lower corner sides of a 2D output image is partially cut and are not visible in the optical device for EPE of the related art, it may be seen that an FOV of the optical device for EPE of the related art is small. Also, in the case of the optical device for EPE of the related art, luminance is low in an outer portion as well as a portion adjacent to a cut portion.

In contrast, as shown inFIG.10C, even when the eye is in the lower center of the eye box, an entire 2D output image is clear in the optical device for EPE100of the one or more embodiments. Thus, it may be seen that an FOV of the optical device for EPE100of the one or more embodiments is large. Also, in the case of the optical device for EPE100, luminance of the entire 2D output image is high.

Referring toFIG.11A, as a small circle at the right of the center among small circles is hatched, it may be seen that an eye is located at the right of the center of the eye box. As shown inFIG.11B, when the eye is at the right of the center of the eye box, because lower corner sides of a 2D output image is partially cut and are not visible in the optical device for EPE of the related art, it may be seen that an FOV of the optical device for EPE of the related art is small. Also, in the case of the optical device for EPE of the related art, luminance is also low in a right upper outer portion as well as a portion adjacent to a cut portion.

In contrast, as shown inFIG.11C, even when the eye is at the right of the center of the eye box, an entire 2D output image is clear in the optical device for EPE100of the one or more embodiments. Thus, it may be seen that an FOV of the optical device for EPE100of the one or more embodiments is large. Also, in the case of the optical device for EPE100, luminance of the entire 2D output image is high.

When comparing luminance for each position of the eye in the eye box, it may be seen that, in the case of the optical device for EPE of the related art, luminance in the outer portion of the 2D output image varies according to a position of the eye in the eye box. In contrast, in the case of the optical device for EPE100of the one or more embodiments, regardless of positions of the eye in the eye box, luminance of the entire 2D output image is high. Thus, it may be seen that, in the case of the optical device for EPE100of the one or more embodiments, there is little change in luminance according to the positions of the eye in the eye box.

Also, when comparing FOVs for each position of the eye in the eye box, in other words, when comparing sizes of the cut portions of the 2D output image, it may be seen that, in the optical device for EPE of the related art, when the eye is located at the right of the center of the eye box, a size of the cut portion is largest, and when the eye is located below the center of the eye box, a size of the cut portion is relatively small. Thus, it may be seen that, in the case of the optical device for EPE of the related art, FOV uniformity according to positions of the eye in the eye box is low. In contrast, in the optical device for EPE100of the one or more embodiments, regardless of positions of the eye in the eye box, the entire 2D output image is clear. Thus, it may be seen that, in the case of the optical device for EPE100of the one or more embodiments, FOV uniformity according to positions of the eye in the eye box is high.

FIGS.12and13are conceptual views of a display apparatus including an optical device for EPE, according to various embodiments. Descriptions that have been provided with reference toFIG.1Ato 5 may be briefly given and omitted.

Referring toFIG.12, a display apparatus1000(hereinafter, simply referred to as a “display apparatus”) may include an optical device for EPE100and an image generator200. The optical device for EPE100may be the optical device for EPE100ofFIG.1A. However, the optical device for EPE100is not limited thereto. For example, the optical device for EPE100a,100b,100c, and100dofFIGS.2B,2C,4A, and4Bmay be implemented in the display apparatus1000.

The image generator200may generate a virtual image and input the virtual image to an input part110of the optical device for EPE100. The image generator200may include a micro-display210and a collimating lens220. The virtual image of the micro-display210may be a 2D virtual image. The virtual image of the micro-display210may be output for each of pixels. Light output from the pixels of the micro-display210may be deformed into parallel light by the collimating lens220and incident onto the input part110of the optical device for EPE100.

Referring toFIG.13, a display apparatus1000amay differ from the display apparatus1000ofFIG.12in that the display apparatus1000aincludes a holographic image generator200ainstead of the general image generator200. Specifically, the display apparatus1000aof the present embodiment may include an optical device for EPE100and the holographic image generator200a. The optical device for EPE100may be the optical device for EPE100ofFIG.1A. However, the optical device for EPE100is not limited thereto.

The holographic image generator200amay include a light source210a, a collimating lens220a, a beam splitter212, a spatial optical modulator213, a lens214, a polarizing plate215, and an image processor230.

The light source210amay generate and output light. The light source210amay output coherent light that may be diffracted by the spatial optical modulator213and subjected to interference. For example, the light source210amay be a laser diode (LD) or a light-emitting diode (LED). However, a type of the light source210ais not limited to an LD or an LED. For example, any type of light sources that output light having spatial coherence may be used as the light source210aof the holographic image generator200a.

Light of the light source210amay be deformed into parallel light by the collimating lens220aand input to the beam splitter212. The beam splitter212may reflect the light from the light source210aand transmit the light to the spatial optical modulator213, and may transmit the light from the spatial optical modulator213to the lens214. The beam splitter212may be a trans-reflective mirror that reflects half of incident light and transmits the other half, or may be a polarizing beam splitter with polarization selectivity. The polarizing plate215may be arranged between the beam splitter212and the spatial optical modulator213. The polarizing plate215may be, for example, a ¼ wave plate. According to an embodiment, the polarizing plate215may be integrally coupled to a surface of the spatial optical modulator213.

The spatial optical modulator213may display a hologram pattern according to a hologram data signal provided from the image processor230, for example, a computer generated hologram (CGH) signal. Light output from the light source210aand incident onto the spatial optical modulator213is diffracted by the hologram pattern displayed on a screen of the spatial optical modulator213, and then may be reproduced as a holographic image having a three-dimensional effect by destructive interference and constructive interference. For the spatial optical modulator213, for example, one of a phase modulator capable of performing only phase modulation, an amplitude modulator capable of performing only amplitude modulation, and a complex modulator capable of performing both phase modulation and amplitude modulation may be used. In the display apparatus1000a, the spatial optical modulator213may be a reflective spatial optical modulator that diffracts and modulates incident light while reflecting the incident light. For example, the spatial optical modulator213may include a liquid crystal on silicon (LCoS), a digital micro-mirror device (DMD), or a semiconductor modulator.

The image processor230may generate a CGH signal based on source image data including information about a holographic image to be reproduced and provide the CGH signal to the spatial optical modulator213. For example, the image processor230may generate the CGH signal by performing, on the source image data, a Fourier transform, and an inverse Fourier transform (IFT), or a fast Fourier transform (FFT), and an inverse fast Fourier transform (IFFT).

The lens214may focus a holographic image and input the holographic image to the input part110of the optical device for EPE100. A distance between the lens214and the input part110may be substantially equal to a focal length of the lens214. However, the distance between the lens214and the input part110is not limited thereto. For example, when the distance between the lens214and the input part110is equal to the focal length of the lens214, a holographic image by the spatial optical modulator213may be maximally incident upon the input part110at various angles.

A distance between the lens214and the spatial optical modulator213may be substantially equal to a focal length of the lens214. However, the distance between the lens214and the spatial optical modulator213is not limited thereto. For example, when the distance between the lens214and the spatial optical modulator213is equal to the focal length of the lens214, a holographic image reproduced on the spatial optical modulator213may be transmitted as it is to an eye E of an observer without degradation of image quality.

FIGS.14A and14Bare respectively a perspective view and a side view of an AR glass onto which a display apparatus is mounted, according to an embodiment. Descriptions that have been provided with reference toFIG.1Ato 5,12, and13may be briefly given and omitted.

Referring toFIGS.14A and14B, an AR glass2000(hereinafter, referred to as an “AR glass”) onto which a display apparatus is mounted may include a display apparatus1000b, a computing system300, and a glass body400.

The display apparatus1000bmay be similar to the display apparatus1000ofFIG.12. However, the display apparatus1000bmay differ from the display apparatus1000ofFIG.12in that two optical devices for EPE are included. For example, in the AR glass2000according to an embodiment, the display apparatus1000bmay include a first optical device for EPE100-1and a second optical device for EPE100-2, respectively corresponding to both eyes. Also, the display apparatus1000bmay include the image generator200that provides a virtual image.

According to an embodiment, in the AR glass2000, the display apparatus1000aofFIG.13may be modified. For example, the AR glass2000may include a display apparatus including the first and second optical devices for EPE100-1and100-2, respectively corresponding to both eyes, and the holographic image generator200a.

The computing system300may include a mounted computing module310and a remote computing module320. The computing system300may also include an inertial sensor330and an environment sensor340. The computing system300may control a virtual image of the image generator200, based on information obtained from the inertial sensor330or the environment sensor340. For example, the inertial sensor330may sense location, orientation, sudden acceleration, and the like, and a result of the sensing by the inertial sensor330may be reflected in the virtual image of the image generator200through the mounted computing module310. Also, the environment sensor340may be various types of cameras, and images obtained by the environment sensor340may be reflected in the virtual image of the image generator200through the mounted computing module310.

In addition, the remote computing module320may supply power to the mounted computing module310by wire or wirelessly. Also, the remote computing module320may supply a resource required by the display apparatus1000bthrough the mounted computing module310. According to an embodiment, the computing system300may include a global positioning system (GPS) receiver.

The glass body400may largely include a lens portion and a leg portion. As shown inFIG.14A, the display apparatus1000bmay be mounted onto the lens portion of the glass body400, and the computing system300may be mounted onto the leg portion of the glass body400. In addition, an arrangement structure of the computing system300on the glass body400is not limited to an arrangement structure shown inFIGS.14A and14B. For example, the computing system300may be arranged with various structures in various portions of the glass body400.

FIG.15is a conceptual view of a vehicle AG apparatus, onto which a display apparatus is mounted, according to an embodiment. Descriptions that have been provided with reference toFIG.1Ato 5 and12to14may be briefly given and omitted.

Referring toFIG.15, a vehicle AR apparatus2000a(hereinafter, referred to as a “vehicle AR apparatus”) onto which a display apparatus is mounted may include a display apparatus1000and a vehicle body400a. The display apparatus1000may be the display apparatus1000ofFIG.12. However, the one or more embodiments are not limited thereto, and the vehicle AR apparatus2000amay include the display apparatus1000aofFIG.13. InFIG.15, in the display apparatus1000, the input part110, the 1D EPE area120, the image generator200, and the like are omitted, and only the 2D EPE area130is shown.

The vehicle body400amay be, for example, a vehicle windshield. Also, the display apparatus1000may be mounted onto or included in a portion of the vehicle body400athat is within a driver’s FOV. For example, as shown inFIG.15, the display apparatus1000may be arranged on a windshield of the vehicle body400aabove a steering wheel SW. However, the position of the display apparatus1000is not limited thereto. InFIG.15, RI may refer to a real image.

The AR devices, for examples AR glass2000and a vehicle AR apparatus2000aonto which one or more of the display apparatuses1000,1000a, and1000bare mounted, have been described with reference toFIG.14Ato15. However, types of AR devices onto which the display apparatus of the one or more embodiments are not limited thereto. For example, the display apparatuses1000,1000a, and1000bmay be mounted onto various AR devices in a head-down display (HDD) or head-up display (HUD) method. Thus, the inventive concept of the disclosure may extend to any display apparatus including the optical device for EPE100, and various AR devices onto which the display apparatus is mounted.

While the inventive concept has been particularly shown and described with reference to embodiments thereof, it should be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.