Patent Description:
Recently, there has been increasing interest in micro display devices applicable as a wearable display device implementing a virtual reality device, an augmented reality device, etc..

A solution for reducing the weight and thickness of a micro display device while maintaining the image quality transferred to user's eyes is continuously being sought. To this end, as an example, a light waveguide-based optical system is being used in the micro display devices.

<CIT> discloses a diffractive optical grating having a two dimensional periodic grating structure. A period of the structure in one direction allows diffraction, and in another direction is short enough to prevent diffraction.

<CIT> and <NPL>, disclose relevant prior art.

Provided is a waveguide-based micro display device.

Provided is an electronic device using a display device.

According to an aspect of the disclosure, there is provided a display device according to claim <NUM>.

The meta-waveguide may further include a magnification coupler provided between the input coupler and the output coupler, the magnification coupler comprising a plurality of third nanostructures configured to form a third phase gradient in a third direction different from the first direction and the second direction.

The third direction may be a direction opposite to a vector sum of the first direction and the second direction.

The meta-lens module may include one or more meta-lenses, the meta-lens being configured to make the image light formed by the image forming device to be incident on the input coupler.

The one or more meta-lenses may include a substrate and a plurality of fourth nanostructures arranged on a first surface of the substrate, having a first refractive index higher than a second refractive index of the substrate and having a shape dimension smaller than a central wavelength of the image light formed by the image forming device.

A height of the fourth nanostructures may be in a range from <NUM>λ0 to <NUM>λ0.

A shape or an arrangement of each of the plurality of fourth nanostructures may be set so that a phase modulation pattern in a fourth range is repeated from a center of the one or more meta-lenses in a radial direction.

The meta-lens module may further include a micro lens array comprising a micro lens corresponding to each of a plurality of pixels of the image forming device.

The micro lens array may be integrally formed on a second surface of the substrate different from the first surface of the substrate.

The plurality of first nanostructures may be two-dimensionally arranged, and wherein two or more of the plurality of first nanostructures may be arranged on a same line in a direction perpendicular to the first direction have a same shape and size.

The second phase gradient may be in a form in which a phase modulation pattern of a second range is repeated in the second direction.

The plurality of second nanostructures may be two-dimensionally arranged, and wherein two or more of the plurality of second nanostructures may be arranged on a same line in a direction perpendicular to the second direction have a same shape and size.

The third phase gradient may be in a form in which a phase modulation pattern of a third range is repeated in the third direction.

The plurality of third nanostructures may be two-dimensionally arranged, and wherein two or more of the plurality of third nanostructures arranged on a same line in a direction perpendicular to the third direction have a same shape and size.

Each of the plurality of first, second, and third nanostructures may have a shape dimension smaller than a central wavelength of the image light output from the image projector.

The plurality of first nanostructures, the plurality of second nanostructures, or the plurality of third nanostructures may be integrally formed with the waveguide element.

The plurality of first nanostructures, the plurality of second nanostructures, or the plurality of third nanostructures are arranged in a plurality of layers.

The image projector may be a first image projector configured to output image light of a first wavelength band; a second image projector configured to output image light of a second wavelength band; and a third image projector configured to output image light of a third wavelength band, and wherein the meta-waveguide may include: a first meta-waveguide configured to transfer the image light output from the first image projector, to the field of view of the user; a second meta-waveguide configured to transfer the image light output from the second image projector, to the field of view of the user; and a third meta-waveguide configured to transfer the image light output from the third image projector, to the field of view of the user.

Among the plurality of first, second, and third nanostructures, each of nanostructures provided in the first meta-waveguide may have a shape dimension smaller than a central wavelength of the first wavelength band, each of nanostructures provided in the second meta-waveguide may have a shape dimension smaller than a central wavelength of the second wavelength band, and each of nanostructures provided in the third meta-waveguide may have a shape dimension smaller than a central wavelength of the third wavelength band.

The meta-waveguide may be configured to transmit ambient light that is incident in front of the user.

The display device may be a wearable device.

According to another aspect of the disclosure, there is provide an electronic device including the display device.

The electronic device may be a vehicle, an augmented reality device, a virtual reality device, a mobile device, or a smart phone.

According to another aspect of the disclosure, there is provided an image forming device configured to generate and output an image; and a meta-lens module configured to direct light corresponding to the image output by the image forming device towards an input coupler of a waveguide, wherein the meta-lens module includes: one or more meta-lenses, each including a substrate and a plurality of nanostructures arranged on a first surface of the substrate, wherein the plurality of nanostructures are configured to have a first refractive index different than a second refractive index of the substrate.

According to another aspect of the disclosure, there is provided a display device including: a meta-waveguide; an image forming device configured to generate and output an image; and a meta-lens module configured to direct light corresponding to the image output by the image forming device towards an input coupler of the meta-waveguide, wherein the meta-lens module includes: one or more meta-lenses, each including a substrate and a plurality of nanostructures arranged on a first surface of the substrate, wherein the plurality of nanostructures are configured to have a first refractive index different than a second refractive index of the substrate, wherein the meta-waveguide includes: a waveguide element configured to totally reflect light inside the waveguide element, the input coupler comprising a plurality of first nanostructures configured to form a first phase gradient in a first direction, the input coupler configured to couple the light corresponding to the image to the inside of the waveguide element, and an output coupler comprising a plurality of second nanostructures configured to form a second phase gradient in a second direction different from the first direction, the output coupler configured to output the light corresponding to the image, which is coupled to the inside of the waveguide element by the input coupler, to an outside of the waveguide element.

Embodiments described below are merely examples and various modifications may be made therein. In the drawings, the same reference numerals represent the same elements, and a size of each element may be exaggerated for clarity and convenience of description.

It will be understood that when one element is referred to as being "on" or "above" another element, the element may be on the other element in direct contact with the other element or without contacting the other element.

The terms 'first', 'second,' etc. may be used to describe various elements but are only used herein to distinguish one element from another element. These terms are not intended to limit materials or structures of elements.

As used herein, the singular expressions are intended to include plural forms as well, unless the context clearly dictates otherwise. It will be understood that when an element is referred to as "including" another element, the element may further include other elements unless mentioned otherwise.

Terms such as "unit", "module," and the like, when used herein, represent units for processing at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software.

The term "the" and demonstratives similar thereto may be understood to include both singular and plural forms.

Unless explicitly stated that operations of a method should be performed in an order described below, the operations may be performed in an appropriate order. In addition, all terms indicating examples (e.g., etc.) are only for the purpose of describing technical ideas in detail, and thus the scope of the present disclosure is not limited by these terms unless limited by the claims.

<FIG> is a perspective view showing a schematic configuration of a display device <NUM> according to an example embodiment, <FIG> is a side view showing a schematic configuration of the display device <NUM> according to an example embodiment, and <FIG> is a conceptual diagram showing a schematic configuration of an image projector <NUM> provided in the display device <NUM> of <FIG>.

The display device <NUM> includes the image projector <NUM> that outputs image light L1 and a meta-waveguide <NUM> that transmits the image light L1 output from the image projector <NUM> to an observer's field of view. Here, the image light L1 may be light depicting the image projected by the projector <NUM>.

The meta-waveguide <NUM> includes a waveguide element <NUM> totally reflecting light therein, an input coupler <NUM> coupling the image light L1 from the image projector <NUM> to the inside of the waveguide element <NUM>, and an output coupler <NUM> outputting the light, which is coupled to the inside of the waveguide element <NUM> by the input coupler <NUM>, to the outside of the waveguide element <NUM>.

The waveguide element <NUM> includes an optically transparent material, and may include glass having a refractive index greater than <NUM> or a transparent plastic material. According to an example embodiment, the transparent material may be a material through which the image light L1 formed by an image forming device <NUM> may pass through. According to an example embodiment, transparency of the transparent material may not be <NUM>%, and the transparent material may have a certain color. That is, according to an example embodiment, the transparent material may not be <NUM>% transparent.

The input coupler <NUM> may include a plurality of first nanostructures NS1, and a shape, size, arrangement, etc. of the plurality of first nanostructures NS1 may be set to exhibit a first phase gradient. The output coupler <NUM> may include a plurality of second nanostructures NS2, and a shape, size, and arrangement, etc. of the plurality of second nanostructures NS2 may be set to exhibit a second phase gradient. According to an example embodiment, the arrangement may include an arrangement gap and/or an arrangement type.

The meta-waveguide <NUM> may further include a magnification coupler <NUM> positioned between the input coupler <NUM> and the output coupler <NUM>. The magnification coupler <NUM> may include a plurality of third nanostructures NS3, and shapes and an arrangement of the plurality of third nanostructures NS3 may be set to exhibit a third phase gradient.

A thickness T1 of the meta-waveguide <NUM>, as shown in shown in <FIG>, may range from <NUM> to <NUM>.

A path through which the image light L1 output from the image projector <NUM> reaches the observer's field of view will be briefly described as follows. The image light L1 is coupled to the inside of the waveguide element <NUM> through the input coupler <NUM>, the image light L1 is totally reflected on an upper surface 320a and a lower surface 320b of the waveguide element <NUM>, and travels inside of the waveguide element <NUM> in an X direction. In this path, the image light L1 reaching the magnification coupler <NUM> travels in a Y direction. That is, the image light L1 is totally reflected on the upper surface 320a and the lower surface 320b of the waveguide element <NUM>, and is propagated inside of the waveguide element <NUM> in the Y direction. The light reaching the output coupler <NUM> in this path is output to the outside of the meta-waveguide <NUM> in a Z direction, and reaches the observer's field of view.

The meta-waveguide <NUM> may also transmit ambient light L2 that is incident in front of the observer. The image light L1 and the ambient light L2 may reach the observer's field of view together.

The image projector <NUM> may include the image forming device <NUM> and a meta-lens module <NUM>.

The image forming device <NUM> modulates light according to image information to be displayed to the observer to form an image. The type of the image formed by the image forming device <NUM> is not particularly limited, and may be, for example, a 2D image or a 3D image. The 3D image may be, for example, a stereo image, a hologram image, a light field image, or an integral photography (IP) image, and may include a multi-view or super multi-view image.

The image forming device <NUM> may include, for example, a liquid crystal on silicon (LCoS) device, a liquid crystal display (LCD) device, an organic light emitting diode (OLED) display device, and a digital micromirror device (DMD), and may further include next-generation display devices such as micro LED and quantum dot (QD) LED. When a display device provided in the image forming device <NUM> is a non-emission type device such as an LCD device, the image forming device <NUM> may further include a light source providing light for forming an image.

The meta-lens module <NUM> is configured to make the image light L1 formed by the image forming device <NUM> incident on the input coupler <NUM> provided in the meta-waveguide <NUM>. The meta-lens module <NUM> may include one or more meta-lenses, and the meta-lenses may include a plurality of fourth nanostructures NS4. Shapes and an arrangement of the plurality of fourth nanostructures NS4 may be set to form a phase gradient capable of exhibiting a certain desired refractive power with respect to the incident light.

A thickness T2 of the meta-lens module <NUM>, as shown in <FIG>, may range from <NUM> to <NUM>.

According to an example embodiment the first to fourth nanostructures NS1, NS2, NS3, and NS4 are materials exhibiting a difference in refractive index from a surrounding material, and a phase of light that is incident on these nanostructures is delayed due to a refractive index distribution according to shapes and arrangements of the nanostructures. Hereinafter, expressions of a 'phase delay', a 'phase modulation' or a 'phase' by nanostructures may be used interchangeably, all of which mean a relative phase at a position immediately after passing through the nanostructures, with respect to a phase at position before undergoing the refractive index distribution formed by the nanostructures.

The expression 'phase gradient' or 'phase profile' means a function of a position indicating a degree of phase modulation in a space in which the nanostructures are located, along a certain direction, and may be used interchangeably. The phase profile appears differently according to detailed shapes, sizes, and arrangements of the nanostructures. In other words, the detailed shape, size, and arrangement of the nanostructure set for each position may be determined according to a desired phase profile (or phase gradient).

<FIG> illustrate configurations of the image projector <NUM> inputting image light to a meta-waveguide through the input coupler <NUM> in a display device according to an embodiment.

Referring to <FIG>, the image projector <NUM> includes the image forming device <NUM> and the meta-lens module <NUM>, and the meta-lens module <NUM> may include one meta-lens <NUM>. The image forming device <NUM> and the meta-lens <NUM> may be fixed to a housing <NUM> and attached to the waveguide element <NUM> to face the input coupler <NUM>.

A total thickness T3 of the meta-waveguide <NUM> and image projector <NUM>, as shown in <FIG>, may range from <NUM> to <NUM>, or range <NUM> to <NUM>.

Referring to <FIG>, the meta-lens module <NUM> of the image projector <NUM> may further include a micro lens array <NUM>. The micro lens array <NUM> may include micro lenses facing a plurality of pixels of the image forming device <NUM>. The meta-lens module <NUM> may also include two meta-lenses <NUM> and <NUM>.

Referring to <FIG>, the micro lens array <NUM> and the meta-lens <NUM> may be respectively formed on both sides of a substrate SU to have an integrated structure.

The meta-lens module <NUM> illustrated in <FIG> is an example, and the number or positions of the meta-lenses <NUM> and <NUM> provided therein may be changed. The meta-lenses <NUM> and <NUM> illustrated in <FIG> will be described in detail with reference to <FIG>.

<FIG> is a plan view illustrating a configuration of a meta-lens ML provided in a display device according to an example embodiment, <FIG> is a cross-sectional view taken along line A-A of <FIG>, and <FIG> shows a phase profile of the meta-lens ML of <FIG>.

The meta-lens ML modulates a phase of image light of a certain wavelength band formed by the image forming device <NUM>. According to an example embodiment, the meta-lens ML includes the plurality of fourth nanostructures NS4. The certain wavelength band may be a band including a visible light band or a part of the visible light band, or an infrared band or a part of the infrared band, or all of them. The fourth nanostructure NS4 may be provided on a support layer SP. The support layer SP may be the substrate SU having a lower surface on which the micro lens array <NUM> is formed in <FIG>. For convenience, only some of the fourth nanostructures NS4 are illustrated in <FIG>, and the number of fourth nanostructures NS4 shown in <FIG> is also an example. The fourth nanostructure NS4 has a shape dimension of a sub-wavelength smaller than a central wavelength λ0 of the certain wavelength band, and has a refractive index different from that of the support layer SP and other surrounding material. The meta-lens ML may implement various phase profiles with respect to incident light according to an arrangement shape of the fourth nanostructures NS4.

The meta-lens ML includes a plurality of phase modulation regions Rk including the plurality of fourth nanostructures NS4 whose shapes, sizes, and arrangements are determined according to a set rule. The plurality of phase modulation regions Rk may be arranged in a certain direction defining the phase profile, and this direction may be a radial direction r away from a center C of the meta-lens ML as shown. However, the disclosure is not limited thereto.

The rule set in each region of the meta-lens ML is applied to a parameter such as the shape, size (a width and a height), spacing, and arrangement of the fourth nano structure NS4, and may be set according to a phase profile that is to be implemented by the meta-lens ML as a whole, for example, the phase profile illustrated in <FIG>.

When light is incident on the meta-lens ML in the Z direction and passes through the meta-lens ML, the light meets the refractive index distribution according to the arrangement of the plurality of fourth nanostructures NS4 having different refractive indices from the surrounding material. A position of a wavefront connecting points with the same phase in a traveling path of the light is different before and after undergoing the refractive index distribution according to the arrangement of the fourth nanostructures NS4, which is expressed as a phase delay. A degree of the phase delay differs according to each position that is a variable of the refractive index distribution, that is, according to a position (x, y coordinates) on the plane perpendicular to a traveling direction (z direction) of the light at a position immediately after the light passes through the fourth nanostructures NS4 of the meta-lens ML. When the arrangement of the fourth nanostructures NS4 is polar symmetry or has rotational symmetry of a certain angle with respect to a z-axis, the phase profile may be expressed as a function of a distance r from the center C. Such a phase profile appears differently according to the detailed shape, size, arrangement, etc. of the fourth nanostructure NS4 constituting the meta-lens ML. In other words, the detailed shape, size, arrangement, etc. of the fourth nanostructure NS4 set for each position may be determined according to a desired phase profile.

Each of the plurality of phase modulation regions Rk is a region indicating a phase modulation pattern within a certain range. The plurality of phase modulation regions Rk includes a first region R<NUM>, a second region R<NUM>,. , N-th region RN sequentially arranged in a radial direction r from the center C of the meta-lens ML. According to an example embodiment, the first region R<NUM> may be a circular region, and the second region R<NUM> to the N-th region RN may be annular regions. The first region R<NUM> to the N-th region RN are regions exhibiting a monotonous phase delay in a certain range, and as shown in <FIG>, the phase modulation range of the second region R<NUM> to the N-th region RN may be the same. The phase modulation range may be 2π radians. The phase modulation range of the first region R<NUM> may be smaller than 2π radians, but all may be referred to as 2π zones. However, the disclosure is not limited to the shape, the size, the spacing, and/or the arrangement of the regions Rk as illustrated <FIG>. As such, according to another example embodiment, the regions Rk may have another shape, size, spacing, and/or arrangement.

In <FIG>, two adjacent regions Rk and Rk+<NUM> are illustrated, and are regions representing the same phase modulation range. The two regions have different widths in the radial direction r, and thus the two regions are regions having different inclinations of a phase change in the radial direction r, and diffracting incident light at different angles.

The total number N, widths W<NUM>, Wk, and WN, and the phase profiles of the phase modulation regions Rk may be main variables in the performance of the meta-lens ML.

In order for the meta-lens ML to function as a lens, the widths W<NUM>, Wk, and WN of the phase modulation regions Rk may not be constant, for example, may be set to decrease from the center C to the periphery. And, rules may be set in the phase modulation regions Rk so that the direction of diffracting the incident light in the phase modulation regions Rk is slightly different, that is, the deflection angle formed when the incident light passes through the phase modulation regions Rk is slightly different. The distribution of the number N and the widths W<NUM>, Wk, and WN of the phase modulation regions Rk is related to the magnitude (an absolute value) of maximum refractive power of the meta-lens ML, and a sign of the refractive power may be determined according to whether the rule is in each of the phase modulation regions Rk. For example, the larger the maximum refractive power, the more the phase modulation regions Rk of narrower widths may be used, and, in each the phase modulation regions Rk, positive refractive power may be implemented by the arrangement (the arrangement in which phase decreases) of rules in which the size of the fourth nanostructure NS4 decreases in the radial direction r, and negative refractive power may be implemented by the arrangement (the arrangement in which phase increases) of rules in which the size of the fourth nanostructure NS4 increases in the radial direction r. The shape distribution and phase profile of the fourth nanostructure NS4 illustrated in <FIG>, respectively, are shown in the shape of lens having the positive refractive power, which is an example. The meta-lens ML may be deformed to have the fourth nanostructures NS4 having a phase profile indicating the negative refractive power and a shape distribution suitable for the phase profile.

Referring to <FIG>, the meta-lens ML includes the support layer SP and the fourth nanostructure NS4 disposed on the support layer SP. In addition, the meta-lens ML may further include a protective layer PR covering the fourth nanostructure NS4.

The support layer SP has a transparent property with respect to light in an operating wavelength band of the meta-lens ML, and may include any one of materials such as glass (fused silica, BK7, etc.), quartz, polymer (PMMA, SU-<NUM>, etc.) and other transparent plastic.

The fourth nanostructure NS4 includes a material having a refractive index difference from that of the surrounding material. The surrounding material may include a protective layer PR and a support layer SP. For example, the fourth nanostructure NS4 may have a high refractive index of a difference equal to or greater than <NUM> from the refractive index of the surrounding material, or a low refractive index of a difference equal to or greater than <NUM> from the refractive index of the surrounding material. The refractive index difference may be equal to or greater than <NUM>, or equal to or greater than <NUM>.

When the fourth nanostructure NS4 includes a material having a higher refractive index than that of the surrounding material, the fourth nanostructure NS4 may include at least one of c-Si, p-Si, a-Si III-V compound semiconductors (GaAs, GaP, GaN, etc.), SiC, TiO<NUM>, SiN, and the surrounding material of the low refractive index may include a polymer material such as SU-<NUM> and PMMA, SiO<NUM>, or SOG.

When the fourth nanostructure NS4 includes a material having a lower refractive index than that of the surrounding material, the fourth nanostructure NS4 and the compensation structure CS may include SiO<NUM> or air, and surrounding material of the high refractive index may include at least one of c-Si, p-Si, a-Si III-V compound semiconductors (GaAs, GaP, GaN, etc.), SiC, TiO<NUM>, SiN.

The fourth nanostructure NS4 may have a shape dimension smaller than a central wavelength λ<NUM> of the image light formed by the image forming device <NUM>. The height of the fourth nanostructure NS4 may be in the range from <NUM>λ<NUM> to <NUM>λ<NUM>.

The fourth nanostructure NS4 may have a cylindrical shape and, in addition, may have various shapes such as polygonal poles, elliptical poles, etc..

In <FIG>, the features of the meta-lenses <NUM> and <NUM> that may be included in the meta-lens module <NUM> shown in <FIG> have been described, and the shapes and an arrangement of nanostructures provided in each of the meta-lenses <NUM> and <NUM> may be set to correspond to or match the refractive power to be implemented by the meta-lenses <NUM> and <NUM>.

<FIG> is a conceptual diagram illustrating a detailed shape and optical action of the input coupler <NUM> of the meta-waveguide <NUM> provided in a display device according to the example embodiment.

The input coupler <NUM> couples the image light L1 from the image projector <NUM> to the inside of the waveguide element <NUM>. That is, the input coupler <NUM> may make the incident image light L1 reach the lower surface 320b of the waveguide element <NUM> at an angle at which total reflection occurs. The shape, size, arrangement, etc. of the plurality of first nanostructures NS1 constituting the input coupler <NUM> are set to form a first phase gradient in a first direction (X direction) so as to act a momentum M in the first direction on a ray flow of the incident image light L1. The plurality of first nanostructures NS1 are illustrated to be arranged in a single layer, but the present disclosure is not limited thereto, and the plurality of first nanostructures NS1 may be arranged in a plurality of layers.

<FIG> is a graph showing a phase gradient of the input coupler <NUM>.

The phase gradient shown in the graph is a form in which a phase modulation pattern of a certain range is repeated in the first direction (X). The certain range may be 2π radians, but is not limited thereto. The repeating phase modulation pattern is illustrated as a straight line, but this is an example, and the repeating phase modulation pattern may be changed into various shapes maintaining monotony in which a direction of increase or decrease does not change. The sizes of regions A1 and A2 in which the phase modulation pattern is repeated may be the same or may change according to a certain rule in the first direction.

<FIG> is a plan view showing shapes and an arrangement of the plurality of first nanostructures NS1 constituting an input coupler.

The shape, size, arrangement, etc. of the plurality of first nanostructures NS1 are set to form a phase gradient as shown in <FIG> in the first direction (X direction). Among the plurality of first nanostructures NS1, the first nanostructures NS1 arranged on the same line and parallel to the Y direction perpendicular to the first direction may have the same shape and size.

<FIG> is a conceptual diagram illustrating a detailed shape and optical action of the magnification coupler <NUM> of the meta-waveguide <NUM> provided in a display device according to the embodiment, and <FIG> is a conceptual diagram illustrating a direction of the momentum M of the magnification coupler <NUM> acting on a ray flow of the image light L1.

The magnification coupler <NUM> may gradually make part of the image light L1 traveling in the other direction (Y direction) with respect to the image light L1 coupled to the inside of the waveguide element <NUM> by the input coupler <NUM> to totally reflect the inside of the waveguide element <NUM> and magnify an X-direction width of the light traveling in the Y direction.

The ray flow of the image light L1 traveling inside the waveguide element <NUM> and reaching the magnification coupler <NUM> is at a state where the momentum M of the input coupler <NUM> acts on in the X direction. In order to change this ray flow in the Y direction, the direction of the momentum M may be set as shown in <FIG>. This direction will be referred to as a third direction hereinafter. The third direction corresponds to a direction of a vector difference (Y-X) DYX between the Y direction and the X direction. The magnification coupler <NUM> may include a plurality of third nanostructures NS3 whose shape, size, arrangement, etc. are set to form a third phase gradient in the third direction to form such momentum. The plurality of third nanostructures NS3 are illustrated to be arranged in a single layer, but the present disclosure is not limited thereto, and the plurality of third nanostructures NS3 may be arranged in a plurality of layers.

<FIG> is a graph showing a phase gradient of the magnification coupler <NUM>.

The phase gradient shown in the graph is a form in which a phase modulation pattern of a certain range is repeated in the third direction DYX. The certain range may be 2π, but is not limited thereto. The repeating phase modulation pattern is illustrated as a straight line, but this is an example, and the repeating phase modulation pattern may be changed into various shapes maintaining monotony in which a direction of increase or decrease does not change. The sizes of the regions A1 and A2 in which the phase modulation pattern is repeated may be the same or may change according to a certain rule in the third direction.

<FIG> is a plan view showing shapes and an arrangement of the plurality of third nanostructures NS3 constituting a magnification coupler.

The shape, size, arrangement, etc. of the plurality of third nanostructures NS3 are set to form a phase gradient as shown in <FIG> in the third direction (DYX). Among the plurality of third nanostructures NS3, the third nanostructures NS3 arranged on the same line and parallel to a direction (SXY) perpendicular to the third direction (DYX) may have the same shape and size.

<FIG> is a conceptual diagram illustrating an optical action of the output coupler <NUM> of a meta-waveguide provided in a display device according to an example embodiment.

The image light L1 magnified in the X direction inside the waveguide element <NUM> by the magnification coupler <NUM> and traveling inside the waveguide element <NUM> may reach the output coupler <NUM> and then may be output to the outside of the waveguide element <NUM>. In order to form such a flow, the output coupler <NUM> may include the plurality of second nanostructures NS2 whose shape, size, arrangement, etc. are set to form a second phase gradient in a second direction (-Y direction). The plurality of second nanostructures NS2 are illustrated to be arranged in a single layer, but the present disclosure is not limited thereto, and the plurality of second nanostructures NS2 may be arranged in a plurality of layers.

<FIG> is a graph showing a phase gradient of the output coupler <NUM>.

The phase gradient shown in the graph is a form in which a phase modulation pattern in a certain range is repeated in the second direction (-Y direction). The certain range may be 2π, but is not limited thereto. The repeating phase modulation pattern is illustrated as a straight line, but this is an example, and the repeating phase modulation pattern may be changed into various shapes maintaining monotony in which a direction of increase or decrease does not change. The sizes of the regions A1 and A2 in which the phase modulation pattern is repeated may be the same or may change according to a certain rule in the second direction.

<FIG> is a plan view showing shapes and an arrangement of the second nanostructures NS2 constituting the output coupler <NUM>.

The shape, size, arrangement, etc. of the plurality of second nanostructures NS2 are set to form a phase gradient as shown in <FIG> in the second direction (-Y direction). Among the plurality of second nanostructures NS2, the second nanostructures NS2 arranged on the same line and parallel to a direction perpendicular to the second direction may have the same shape and size.

The first nanostructure NS1, the second nanostructure NS2, and the third nanostructure NS3 illustrated in the above description are in a cylindrical shape, but are not limited thereto, and the first to third nanostructures NS1 to NS3 may be changed to various shapes. For example, the first to third nanostructures NS1 to NS3 may be changed to an elliptical column, a polygonal column, a column having an arbitrary cross-sectional shape, or an asymmetrical shape.

Each of the first nanostructures NS1, the second nanostructures NS2, and the third nanostructures NS3 illustrated in the above description includes a material having a refractive index difference from that of the surrounding material. For example, each of the first nanostructures NS1, the second nanostructures NS2, and the third nanostructures NS3 may have a high refractive index of a difference equal to or greater than <NUM> from the refractive index of the surrounding material, or a low refractive index of a difference equal to or greater than <NUM> from the refractive index of the surrounding material. The refractive index difference may be equal to or greater than <NUM>, or equal to or greater than <NUM>. Some of the first nanostructure NS1, the second nanostructure NS2, and the third nanostructure NS3 may have a refractive index higher than that of the surrounding material, and others may have a lower refractive index than that of the surrounding material.

When the first nanostructure NS1, the second nanostructure NS2, or the third nanostructure NS3 includes a material having a higher refractive index than that of the surrounding material, the first nanostructure NS1, the second nanostructure NS2, and the third nanostructure NS3 may include at least one of c-Si, p-Si, a-Si III-V compound semiconductors (GaAs, GaP, GaN, etc.), SiC, TiO<NUM>, SiN, and the surrounding material of the low refractive index may include a polymer material such as SU-<NUM> and PMMA, SiO<NUM>, or SOG.

When the first nanostructure NS1, the second nanostructure NS2, or the third nanostructure NS3 includes a material having a lower refractive index than that of the surrounding material, the first nanostructure NS1, the second nanostructure NS2 or the third nanostructure NS3 may include SiO<NUM> or air, and surrounding material of the high refractive index may include at least one of c-Si, p-Si, a-Si III-V compound semiconductors (GaAs, GaP, GaN, etc.), SiC, TiO<NUM>, SiN.

Each of the first nanostructure NS1, the second nanostructure NS2, and the third nanostructure NS3 may have a shape dimension smaller than the central wavelength λ0 of image light output from an image projector. The height of each of the first nanostructure NS1 and the second nanostructure NS2 may be in the range from <NUM>λ<NUM> to <NUM>λ<NUM>. The height of the third nanostructure NS3 may be in the range from <NUM>λ<NUM> to <NUM>λ<NUM>.

The first nanostructure NS1, the second nanostructure NS2, and the third nanostructure NS3 may be integrally formed with the waveguide element <NUM> or may be combined with the waveguide element <NUM> after formed on a separate support layer.

In the above description, the input coupler <NUM> and the output coupler <NUM> have been described as operating as a transmission type. As light passes through the input coupler <NUM> and the output coupler <NUM>, a ray flow of the light is changed by receiving a certain momentum action. The magnification coupler <NUM> changes the ray flow of light traveling inside the waveguide element <NUM>, and thus the magnification coupler <NUM> operates as a reflective type. That is, the light is reflected from the magnification coupler <NUM> and the ray flow is changed by receiving the certain momentum action.

The input coupler <NUM> and the output coupler <NUM> are not limited to the transmissive type, and any one or both of them may be changed to the reflective type. When the input coupler <NUM> and the output coupler <NUM> operate as the reflective type, the shape dimensions of the first nanostructures NS1 and the second nanostructures NS2 may be different from when the input coupler <NUM> and the output coupler <NUM> operate as the transmissive type. The first nanostructure NS1 and the second nanostructure NS2 may have a shape dimension smaller than the central wavelength λ<NUM> of the image light output from the image projector. The height of each of the first nanostructure NS1 and the second nanostructure NS2 may be in the range from <NUM>. 2λ<NUM> to 4λ<NUM>.

<FIG> is a perspective view showing a schematic configuration of a display device <NUM> according to another example embodiment, and <FIG> shows a configuration of the image projector <NUM> that inputs image light to a meta-waveguide <NUM> through an input coupler <NUM> in the display device <NUM> of <FIG>.

The display device <NUM> includes the image projector <NUM> and the meta-waveguide <NUM>. The example embodiment illustrated in <FIG> is different from the display device <NUM> of <FIG> in the arrangement positions of the input coupler <NUM> and an output coupler <NUM> of the meta-waveguide <NUM>.

According to an example embodiment, the input coupler <NUM> and the output coupler <NUM> operate as reflective type couplers.

The input coupler <NUM> is provided on the lower surface 320b of the waveguide element <NUM>, that is, the opposite surface of the upper surface 320a of the waveguide element <NUM> facing the image projector <NUM>. The image light L1 in the image projector <NUM> may be incident into the waveguide element <NUM> through the upper surface 320a of the waveguide element <NUM>, reflected on the input coupler <NUM> disposed on the lower surface 320b of the waveguide element <NUM> and then totally reflected in the waveguide element <NUM> and travel toward the first direction (X direction).

An output coupler <NUM> is also provided on the lower surface 320b of the waveguide element <NUM>. The light reaching the output coupler <NUM> is reflected, a direction of a ray flow is changed, the light reaches the upper surface 320a of the waveguide element <NUM> at an angle smaller than a total reflection critical angle, and is output to the outside of the waveguide element <NUM>.

According to another example embodiment, one of the input coupler <NUM> and the output coupler <NUM> may be a reflective type coupler and the other may be a transmissive type coupler.

<FIG> is a perspective view illustrating a schematic configuration of a display device <NUM> according to another example embodiment.

The display device <NUM> of the example embodiment illustrated in <FIG> is different from the display device <NUM> of <FIG> in that a magnification coupler is not separately provided.

The display device <NUM> includes the image projector <NUM> and a meta-waveguide <NUM>. The meta-waveguide <NUM> includes the waveguide element <NUM>, an input coupler <NUM> coupling light to the inside of the waveguide element <NUM>, and an output coupler <NUM> outputting light to the outside of the waveguide element <NUM>.

The input coupler <NUM> inputs the image light L1 output from the image projector <NUM> to the waveguide element <NUM> at an angle that is totally reflected inside the waveguide element <NUM>. When the light totally reflects the inside of the waveguide element <NUM> and traveling reaches the output coupler <NUM>, the light is output to the outside of the waveguide element <NUM>.

In the display device <NUM> of the example embodiment, the input coupler <NUM> may be formed to serve as both the input coupler <NUM> and the magnification coupler <NUM> of the display device <NUM> of <FIG>. For example, the input coupler <NUM> may include a plurality of nanostructures and may have a phase gradient that acts a momentum in the X and Y directions on the image light L1. The output coupler <NUM> may include a plurality of nanostructures whose shape, arrangement, size, etc. are set to have a phase gradient acting a momentum in the -Y direction, similarly to the output coupler <NUM> of the display device <NUM> of <FIG>.

Alternatively, in the display device <NUM> of the example embodiment, the output coupler <NUM> is formed to serve as both the magnification coupler <NUM> and the output coupler <NUM> of the display device <NUM> of <FIG>, and the input coupler <NUM> may be similar to the input coupler <NUM> of the display device <NUM> of <FIG>.

Although both the input coupler <NUM> and the output coupler <NUM> are shown as a transmissive type, any one or both of them may be changed to a reflective type.

<FIG> and <FIG> are a perspective view and a side view showing a schematic configuration of a display device <NUM> according to another example embodiment.

The display device <NUM> includes an image projector and a meta-waveguide.

The image projector includes a first image projector <NUM> that outputs an image light L11 of a first wavelength band, a second image projector <NUM> that outputs an image light L12 of a second wavelength band, and a third image projector <NUM> that outputs image light of a third wavelength band, and the meta-waveguide includes a first meta-waveguide <NUM> that transmits the image light L12 output from the first image projector <NUM> to the observer's field of view, a second meta-waveguide <NUM> that transmits the image light L12 output from the second image projector <NUM> to the observer's field of view, and a third meta-waveguide <NUM> that transmits the image light L13 output from the third image projector <NUM> to the observer's field of view.

Each of the first image projector <NUM>, the second image projector <NUM>, and the third image projector <NUM> includes an image forming device and a meta-lens module, similarly to the display device <NUM> of <FIG>. However, there are differences in that image forming devices form images of different wavelength bands, and detailed shapes, sizes, and arrangements of nanostructures are set so that meta-lenses provided in each meta-lens module operate on light of different wavelength bands.

The nanostructures provided in the first image projector <NUM> may have a shape dimension smaller than a central wavelength λ<NUM> of the first wavelength band, the nanostructures provided in the second image projector <NUM> may have a shape dimension smaller than a central wavelength λ<NUM> of the second wavelength band, and the nanostructures provided in the third image projector <NUM> may have a shape dimension smaller than a central wavelength λ<NUM> of the third wavelength band.

The first meta-waveguide <NUM> includes a waveguide element <NUM>, an input coupler <NUM>, an magnification coupler <NUM> and an output coupler <NUM>, the second meta-waveguide <NUM> includes a waveguide element <NUM>, an input coupler <NUM>, an magnification coupler <NUM> and an output coupler <NUM>, and the third meta-waveguide <NUM> includes a waveguide element <NUM>, an input coupler <NUM>, an magnification coupler <NUM> and an output coupler <NUM>.

The input couplers <NUM>, <NUM>, and <NUM>, the magnification couplers <NUM>, <NUM>, and <NUM>, and the output couplers <NUM>, <NUM>, and <NUM> are respectively similar to the input coupler <NUM>, the magnification coupler <NUM>, and the output coupler <NUM> described in the display device <NUM> of <FIG>, but there is a difference in that detailed shape, size, arrangement, etc. of the nanostructures are set to operate on light of different wavelength bands.

The nanostructures provided in the first meta-waveguide <NUM> may have a shape dimension smaller than the central wavelength λ<NUM> of the first wavelength band, the nanostructures provided in the second meta-waveguide <NUM> a shape dimension smaller than the central wavelength λ<NUM> of the second wavelength band, and the nanostructures provided in the third meta-waveguide <NUM> may have a shape dimension smaller than the central wavelength λ<NUM> of the third wavelength band.

The first meta-waveguide <NUM>, the second meta-waveguide <NUM>, and the third meta-waveguide <NUM> may be arranged to overlap in the Z direction. In such an arrangement, the first wavelength band may be the shortest wavelength band, and then, the second wavelength band and the third wavelength band may be increased in the order of the wavelengths. For example, the first wavelength band may be a blue light band, the second wavelength band may be a green light band, and the third wavelength band may be a red light band.

A total thickness T4 of the display device <NUM>, as shown in <FIG>, may range from <NUM> to <NUM>, or, range <NUM> to <NUM>.

<FIG> shows an example in which the first, second, and third image projectors <NUM>, <NUM>, and <NUM> are integrally implemented in the display device <NUM> of <FIG>.

The first image forming device <NUM> and meta-lenses m1 and m2, the second image forming device <NUM> and meta-lenses m3 and m4 corresponding thereto, and the third image forming device <NUM> and meta-lenses m5 and m6 corresponding thereto may have a structure fixed to one housing <NUM>.

The above-described display device <NUM> may implement a waveguide-based image system for each color, and thus crosstalk may be suppressed for each color, and light efficiency may increase.

<FIG> is a conceptual diagram illustrating a schematic structure of an augmented reality device <NUM> according to an example embodiment.

The augmented reality device <NUM> includes a display device <NUM>, a processor <NUM> that controls the display device <NUM>, and a memory <NUM> in which codes of programs to be executed in a processor <NUM>, and other data, etc. are stored. The augmented reality device <NUM> may also include a sensor <NUM> for recognizing a user environment.

The first meta-waveguide <NUM>, the second meta-waveguide <NUM>, and the third meta-waveguide <NUM> provided in the display device <NUM> respectively transfer the image light L1 by the light L11, L12, and L13 of different wavelength bands from the first image projector <NUM>, the second image projector <NUM>, and the third image projector <NUM> to an observer's field of view, and also transmit and transfer the ambient light L2 in front of an observer to the observer's field of view.

The first image projector <NUM>, the second image projector <NUM>, and the third image projector <NUM> may be controlled by the processor <NUM> so that the image light L1 includes additional information corresponding to a user environment. For example, the user environment is recognized by the sensor <NUM>, and additional information images suitable for a result of recognition may be formed by the first, second, and third image projectors <NUM>, <NUM> and <NUM> in consideration of the result of recognition.

The display device <NUM> provided in the augmented reality device <NUM> is illustrated as the display device of <FIG>, but is not limited thereto, and the display devices <NUM>, <NUM>, and <NUM> of the other embodiments or display devices modified therefrom may be employed.

<FIG> illustrate external appearances of various electronic devices employing a display device according to an embodiment.

As illustrated in <FIG>, the display device may be applied to a wearable device. For example, the display device may be applied to a head mounted display (HMD). In addition, the display device may be applied to a glasses-type display, a goggle-type display, etc. The wearable electronic devices illustrated in <FIG> may operate in synchronization with a smart phone. Such a display device is a head-mounted, glasses-type, or goggles-type virtual reality (VR) display device, augmented reality (AR) display device, or mixed reality (MR) display device that may provide virtual reality or provide both a virtual image and an external real image.

As illustrated in <FIG>, the display device may be applied to a head-up display (HUD) <NUM> of a vehicle.

<FIG> is a block diagram showing an electronic device according to an embodiment.

Referring to <FIG>, the electronic device <NUM> may communicate with another electronic device <NUM> through a first network <NUM> (local area communication network, etc.) or may communicate with another electronic device <NUM> and/or server <NUM> through a second network <NUM> (far-field communication network, etc.) in a network environment <NUM>. The electronic device <NUM> may communicate with the electronic device <NUM> through the server <NUM>. The electronic device <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a sound output device <NUM>, a display device <NUM>, an audio module <NUM>, a sensor module <NUM>, an interface <NUM>, a haptic module <NUM>, a camera module <NUM>, a power management module <NUM>, a battery <NUM>, a communication module <NUM>, a subscriber identity module <NUM>, and/or an antenna module <NUM>. Some of these components may be excluded from or other components may be added to the electronic device <NUM>. Some of these components may be implemented as one integrated circuit. For example, a fingerprint sensor, an iris sensor, an illuminance sensor, etc. of the sensor module <NUM> may be embedded in the display device <NUM> (a display, etc.).

The processor <NUM> may execute software (a program <NUM>) to control one or a plurality of other constituent elements (hardware and software components, etc.) of the electronic device <NUM> connected to the processor <NUM> by executing software (a program <NUM>, and the like), and may perform a variety of data processing or calculations. As part of data processing or operations, the processor <NUM> may load commands and/or data received from other components (the sensor module <NUM>, the communication module <NUM>, etc.) to a volatile memory <NUM>, process the commands and/or data stored in the volatile memory <NUM>, and store resulting data in a non-volatile memory <NUM>. The processor <NUM> may include a main processor <NUM> (a central processing unit, an application processor, etc.), and an auxiliary processor <NUM> (a graphics processing device, an image signal processor, a sensor hub processor, a communication processor, etc.) that is operable independently from or together with the main processor <NUM>. The auxiliary processor <NUM> may use less power than the main processor <NUM>, and may perform a specialized function.

The auxiliary processor <NUM> may control functions and/or states related to some components (the display device <NUM>, the sensor module <NUM>, the communication module <NUM>, etc.) of the electronic device <NUM> instead of the main processor <NUM> when the main processor <NUM> is in an inactive state (a sleep state), or together with the main processor <NUM> when the main processor <NUM> is in an active state (an application execution state). The auxiliary processor <NUM> (the image signal processor, the communication processor, etc.) may be implemented as part of other functionally related components (the camera module <NUM>, the communication module <NUM>, etc.).

The memory <NUM> may store a variety of data required by the components (the processor <NUM>, the sensor module <NUM>, etc.) of the electronic device <NUM>. The data may include, for example, software (the program <NUM>, etc.), and input data and/or output data with respect to commands related to the software. The memory <NUM> may include the volatile memory <NUM> and/or the non-volatile memory <NUM>.

The program <NUM> may be stored in the memory <NUM> as software, and may include an operating system <NUM>, middleware <NUM>, and/or an application <NUM>.

The input device <NUM> may receive commands and/or data to be used in the components (the processor <NUM>, etc.) of the electronic device <NUM> from outside (a user, etc.) the electronic device <NUM>. The input device <NUM> may include a microphone, a mouse, a keyboard, and/or a digital pen (a stylus pen).

The sound output device <NUM> may output a sound signal to the outside of the electronic device <NUM>. The sound output device <NUM> may include a speaker and/or a receiver. The speaker may be used for general purposes such as multimedia playback or record playback, and the receiver may be used to receive an incoming call. The receiver may be incorporated as a part of the speaker or implemented as an independent separate device.

The display device <NUM> may visually provide information to the outside of the electronic device <NUM>. The display device <NUM> may include a display, a hologram device, or a projector, and a control circuit for controlling the corresponding device. The display device <NUM> may include touch circuitry set to sense a touch, and/or a sensor circuit (a pressure sensor, etc.) set to measure the intensity of a force generated by the touch. The display device <NUM> may include any one of the above-described display devices <NUM>, <NUM>, <NUM>, and <NUM>, or a display device of a structure modified therefrom. A plurality of display devices <NUM> may be provided.

The audio module <NUM> may convert sound to an electric signal, or convert the electric signal to sound. The audio module <NUM> may obtain sound through the input device <NUM>, or may output sound through a speaker and/or a headphone of another electronic device (the electronic device <NUM>, etc.) which is directly or wirelessly connected to the sound output device <NUM> and/or the electronic device <NUM>.

The sensor module <NUM> may sense an operating state (power, temperature, etc.) of the electronic device <NUM> or an external environment state (a user state, etc.) and may generate an electrical signal and/or a data value corresponding to the sensed state. The sensor module <NUM> may include a fingerprint sensor, an acceleration sensor, a location sensor, a 3D sensor, and may further include an iris sensor, a gyro sensor, a pressure sensor, a magnetic sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, and/or an illuminance sensor.

An interface <NUM> may support one or more designated protocols that may be used for directly or wirelessly connecting the electronic device <NUM> to another electronic device (the electronic device <NUM>, etc.). The interface <NUM> may include a High Definition Multimedia Interface (HDMI), a Universal Serial Bus (USB) interface, an SD card interface, and/or an audio interface.

A connection terminal <NUM> may include a connector used to physically connect the electronic device <NUM> with another electronic device (the electronic device <NUM>, etc.) The connection terminal <NUM> may include an HDMI connector, a USB connector, an SD card connector, and/or an audio connector (a headphone connector, etc.).

The haptic module <NUM> may convert the electric signal into a mechanical stimulus (vibration, movement, etc.) or an electrical stimulus that may be recognized by the user through tactile sense or kinesthetics. The haptic module <NUM> may include a motor, a piezoelectric effect element, and/or an electric stimulation device.

The camera module <NUM> may capture still images and moving images. The camera module <NUM> may include a lens assembly including one or more lenses, image sensors, image signal processors, and/or flashes.

The application <NUM> may include one or more applications executed in connection with the display device <NUM>. Such an application <NUM> may display additional information suitable for a user environment on the display device <NUM>. For example, the camera module <NUM> may be utilized as a sensor recognizing the user environment, and additional information necessary according to a result of recognition may be displayed on the display device <NUM>.

The power management module <NUM> may be implemented as part of a Power Management Integrated Circuit (PMIC).

The battery <NUM> may supply power to the components of the electronic device <NUM>. The battery <NUM> may include a rechargeable primary cell, a rechargeable secondary cell, and/or a fuel cell.

The communication module <NUM> may support establishing a direct (wired) communication channel and/or a wireless communication channel between the electronic device <NUM> and another electronic device (the electronic devices <NUM> and <NUM>, the server <NUM>, etc.) and performing communication through the established communication channel. The communication module <NUM> may operate independently from the processor <NUM> (the application processor, etc.) and may include one or more communication processors that support direct communication and/or wireless communication. The communication module <NUM> may include a wireless communication module <NUM> (a cellular communication module, a local area communication module, a global navigation satellite system (GNSS) communication module, etc.) and/or a wired communication module <NUM> (a local area network (LAN) communication module, a power line communication module, etc.). Among these communication modules, the corresponding communication module may communicate with another electronic device through the first network <NUM> (the local area communication network such as Bluetooth, WiFi Direct, or infrared data association (IrDA)) or the second network <NUM> (the wide area communication network such as a cellular network, the Internet, or a computer network (a local area network (LAN), a wide area network (WAN), etc.)) A variety of types of communication modules may be integrated into one component (a single chip, etc.), or may be implemented as a plurality of components separate from each other (plural chips). The wireless communication module <NUM> may check and authenticate the electronic device <NUM> in the communication network such as the first network <NUM> and/or the second network <NUM> using subscriber information stored in the subscriber identity module <NUM> (International mobile subscriber identifier (IMSI), etc.).

The antenna module <NUM> may transmit a signal and/or power to the outside (another electronic device, etc.) or receive the signal and/or power from the outside. An antenna may include a radiator including a conductive pattern formed on a substrate (a PCB, etc.). The antenna module <NUM> may include one or a plurality of antennas. When a plurality of antennas are included, the communication module <NUM> may select an antenna suitable for the communication method used in a communication network such as the first network <NUM> and/or the second network <NUM> from among the plurality of antennas. Through the selected antenna, a signal and/or power may be transmitted or received between the communication module <NUM> and another device. In addition to the antenna, another component (RFIC, etc.) may be included as part of the antenna module <NUM>.

Some of the components may be connected to each other through communication methods between surrounding devices (a bus, general purpose input and output (GPIO), serial peripheral interface (SPI), mobile industry processor interface (MIPI), etc.) and may interchange signals (commands, data, etc.).

Commands or data may be transmitted or received between the electronic device <NUM> and the external electronic device <NUM> through the server <NUM> connected to the second network <NUM>. The other electronic devices <NUM> and <NUM> may be the same as or different from the electronic device <NUM>. All or some of operations executed by the electronic device <NUM> may be executed by one or more of the other electronic devices <NUM>, <NUM>, and <NUM>. For example, when the electronic device <NUM> is required to perform a function or a service, instead of executing the function or service on its own, the electronic device <NUM> may request the one or more other electronic devices to execute the function or the service partially or wholly. One or more other electronic devices requested to execute the function or the service may execute an additional function or service, and transmit a result of execution to the electronic device <NUM>. To this end, cloud computing, distributed computing, and/or client-server computing technology may be used.

The above-described display device may have a thin optical system based on the nanostructure and the waveguide.

The above-described display device may separately implement an image system for each color, and thus crosstalk may be suppressed and light efficiency may be increased, thereby enabling low-power driving.

The above-described display device may be applied to various electronic devices, such as an augmented reality device, a wearable device, and a head-up display.

Claim 1:
A display device (<NUM>) comprising:
an image projector (<NUM>) comprising an image forming device (<NUM>) and a meta-lens module (<NUM>), the image projector configured to output image light (L1) formed by the image forming device; and
a meta-waveguide (<NUM>) configured to transfer the image light output from the image projector to a field of view of a user, the meta-waveguide comprising:
a waveguide element (<NUM>) configured to totally reflect light inside the waveguide element,
an input coupler (<NUM>) comprising a plurality of first nanostructures (NS1) configured to form a first phase gradient in a first direction (X), the input coupler configured to couple the image light from the image projector to the inside of the waveguide element, wherein the first phase gradient is in a form in which a phase modulation pattern of a monotonic increase or decrease in a first range is repeated in the first direction, and
an output coupler (<NUM>) comprising a plurality of second nanostructures (NS2) configured to form a second phase gradient in a second direction (Y) different from the first direction, the output coupler configured to output the image light coupled to the inside of the waveguide element by the input coupler, to an outside of the waveguide element.