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

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

Such image system projects generated images onto the eyes of a user using an optical system. In general, the optical system uses a lens, and an image system requires a distance between a spatial light modulator and the lens and a distance between the lens and the eyes of a user in order to project an image onto the eyes of the user. However, this increases the volume of the image system.

<CIT> discloses an optical display comprising: a first waveguide comprising a first surface and a second surface, an input coupler, a fold grating, and an output grating. The input coupler receives collimated first wavelength light from an Input Image Node causes the light to travel within the first waveguide via total internal reflection between the first surface and the second surface to the fold grating. The fold grating provides pupil expansion in a first direction directs the light to the output grating via total internal reflection between the first surface and the second surface. The output grating provides pupil expansion in a second direction different than the first direction and causes the light to exit the first waveguide from the first surface or the second surface. At least one of the input coupler, fold grating and output grating is a rolled k-vector grating, and the fold grating is a dual interaction grating.

<CIT> discloses a display apparatus comprising an image display element, an optical waveguide and first and second reflection-type volume hologram gratings, wherein the second reflection-type volume hologram grating has groups of interference fringes, each group including three types of interference fringes of, for example, different slant angles recorded side by side at the same pitch on a hologram surface thereof.

A display apparatus according to the claimed invention is defined in appended claim <NUM>.

In accordance with an aspect of the invention, there is provided a display apparatus, including: a beam output device comprising a light source and a direction adjustment member, the beam output device being configured to time-sequentially output a plurality of light beams corresponding to a frame image such that the plurality of light beams proceed in different traveling paths, wherein each of the plurality of light beams corresponds to a partial image of the frame image, and wherein the direction adjustment member is configured to adjust the traveling path of each of the plurality of light beams; a waveguide; an input coupler configured to time-sequentially direct the plurality of light beams into the waveguide; and a spatial converter configured to output the plurality of light beams traveling in the waveguide through spatially different regions of the spatial converter to form the frame image in an external space. The spatial converter comprises a plurality of selective transmission elements arranged in a first direction, the first direction crossing directions in which the plurality of light beams are output. Each of the plurality of selective transmission elements is configured to transmit one of the plurality of light beams to the external space and not to transmit remaining light beams of the plurality of light beams to the external space. A number of the plurality of light beams and a number of the plurality of selective transmission elements are equal.

The spatial converter may be further configured to output at least two of the plurality of light beams in different directions.

Each of the plurality of selective transmission elements may be further configured to selectively transmit the plurality of light beams according to an optical characteristic of each of the plurality of selective transmission elements.

The optical characteristic may include a diffraction characteristic.

At least one of a grating structure and a material of at least two of the plurality of selective transmission elements may be different from each other.

Each of the plurality of selective transmission elements may be further configured to selectively transmit the plurality of light beams according to an electrical signal applied to each of the plurality of selective transmission elements.

The input coupler may be further configured to direct the plurality of light beams that are incident on the input coupler at different incident angles.

The spatial converter may be further configured to output the plurality of light beams through the spatially different regions of the spatial converter based on incident angles of the plurality of light beams.

The spatial converter may be further configured to focus the plurality of light beams respectively at different positions in the external space.

A frame image may be provided to a user based on the focused plurality of light beams.

Each of the plurality of light beams may correspond to a pixel image of the frame image.

Diameters of the plurality of light beams output from the spatial converter may be different from diameters of the plurality of light beams incident on the input coupler.

The diameters of the plurality of light beams output from the spatial converter may be greater than the diameters of the plurality of light beams incident on the input coupler.

The input coupler may include: a first input coupler configured to direct first light beams of the plurality of light beams into the waveguide; and a second input coupler configured to direct second light beams of the plurality of light beams into the waveguide.

The first light beams and the second light beams may be synchronously and respectively incident on the first input coupler and the second input coupler.

The waveguide may include a first waveguide in which the first light beams travel; and a second waveguide in which the second light beams travel.

The spatial converter may include a first spatial converter arranged on the first waveguide and configured to output the first light beams through different regions of the first spatial converter; and a second spatial converter arranged on the second waveguide and configured to output the second light beams through different regions of the second spatial converter.

The first spatial converter may be further configured to form a first sub-frame image in a first region of an external space, and the second spatial converter may be further configured to form a second sub-frame image in a second region of the external space, the second region being different from the first region.

The first sub-frame image and the second sub-frame image may correspond to different portions of a frame image.

The display apparatus may further include an exit pupil expander configured to expand the plurality of light beams output from the spatial converter.

The exit pupil expander may be further configured to transmit light corresponding to a reality environment.

The display apparatus may further include a spatial light modulator configured to modulate an amplitude and/or a phase of the plurality of light beams output from the light source.

The above and other aspects, features, and advantages of certain example embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:.

The example embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. For example, the expression "at least one of a, b, and c," should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

In the following description, when an element is referred to as being "above", "on", "connected to" or "coupled to" another element, it may be directly above, on, connected to, or coupled to the other element while making contact with the other element or may be above, on, connected to, or coupled to the other element without making contact with the other element (that is, intervening element(s) may be present).

The terms of a singular form may include plural forms unless otherwise mentioned. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features or elements, but do not preclude the presence or addition of one or more other features or elements.

An element referred to with the definite article or a demonstrative pronoun may be construed as the element or the elements even though it has a singular form.

Terms such as "first" and "second" may be used to describe various elements, but these elements should not be limited by these terms.

<FIG> is a schematic view illustrating a display apparatus <NUM> including a Fourier-beam shaper <NUM> according to an example embodiment of the invention, and <FIG> is a view illustrating a structure of the Fourier-beam shaper <NUM> shown in <FIG>.

Referring to <FIG>, the display apparatus <NUM> may include: a beam output device <NUM> that outputs a plurality of light beams; the Fourier-beam shaper <NUM> that receives the plurality of light beams and outputs the plurality of light beams respectively through spatially different regions of the Fourier-beam shaper <NUM>; and a processor <NUM> that controls the beam output device <NUM> and/or the Fourier-beam shaper <NUM> to display an image based on the plurality of light beams.

The beam output device <NUM> time-sequentially outputs a plurality of light beams. Here, each light beam corresponds to a partial image of a frame image. For example, a light beam corresponds to a pixel image of a frame image or may correspond to a sum of a plurality of pixel images included in a frame image. Light beams may be of light in which different frequencies are mixed. For example, light beams may be of light in which red light, green light, and blue light are mixed.

The beam output device <NUM> includes a light source <NUM> and may include a spatial light modulator <NUM>. The light source <NUM> may provide coherent light. The light source <NUM> may include a laser diode. However, the light source <NUM> is not limited thereto, and light having a certain degree of spatial coherence may be diffracted and modulated by the spatial light modulator <NUM> such that the light may have coherence, and thus another light source may be used as long as the light source is capable of emitting light having a certain degree of spatial coherence.

The light source <NUM> may include a plurality of light sources that output light having different wavelengths. For example, the light source <NUM> may include a first light source that outputs light in a first wavelength band, a second light source that outputs light in a second wavelength band different from the first wavelength, and a third light source that outputs light in a third wavelength band different from the first and the second wavelength bands. The first, the second, and the third wavelength bands may respectively correspond to red light, green light, and blue light.

The spatial light modulator <NUM> may output light having image information by modulating light output from the light source <NUM> under the control of the processor <NUM>. The resolution of modulated light may be determined based on the spatial resolution of the spatial light modulator <NUM>. For example, when the spatial light modulator <NUM> is constituted by one pixel, modulated light corresponds to a pixel image. Alternatively, when the spatial resolution of the spatial light modulator <NUM> is <NUM>×<NUM>, the resolution of modulated light may also be <NUM>×<NUM>. The spatial light modulator <NUM> may output light corresponding to a two-dimensional (2D) image, or a three-dimensional (3D) image or a hologram image having different depth information.

The spatial light modulator <NUM> may include, for example, an amplitude-modulation spatial light modulator, a phase-modulation spatial light modulator, or a complex spatial light modulator that modulates both an amplitude and a phase. In addition, the spatial light modulator <NUM> may include, for example, a transmissive light modulator, a reflective light modulator, or a transflective light modulator. For example, the spatial light modulator <NUM> may include a liquid crystal on silicon (LCoS) panel, a liquid crystal display (LCD) panel, a digital light projection (DLP) panel, an organic light emitting diode (OLED) panel, or a micro-organic light emitting diode (M-OLED) panel. Here, the DLP panel may include a digital micromirror device (DMD).

The beam output device <NUM> further includes a direction adjustment member <NUM> that may change the traveling path of light output from the spatial light modulator <NUM> such that the light may be incident on the Fourier-beam shaper <NUM> at a given angle. The direction adjustment member <NUM> may be an actuator for adjusting the position of the spatial light modulator <NUM> to change the traveling path of light, or may be an optical device for directly changing the traveling path of light output from the spatial light modulator <NUM>. The optical device may be an active optical device capable of differently adjusting the traveling path of light under the control of the processor <NUM>.

Until a plurality of light beams corresponding to one frame image are output, the direction adjustment member <NUM> adjusts the traveling paths of light beams such that the light beams may proceed in different traveling paths. For example, when the resolution of light beams is <NUM>×<NUM> and the resolution of a frame image is <NUM>×<NUM>, the direction adjustment member <NUM> may control a hundred light beams such that the hundred light beams may proceed in a hundred different traveling paths.

The processor <NUM> may control the beam output device <NUM> to output light. An output period of light may be determined based on the resolution of a frame image to be formed, the resolution of light modulated by the spatial light modulator <NUM>, and a frame time. For example, when the frame time is <NUM>/<NUM> second and the resolution of light at the spatial light modulator <NUM> is <NUM>/<NUM> of the resolution of a frame image, the processor <NUM> may control the beam output device <NUM> such that light may be output with a period of a <NUM>/(<NUM>×<NUM>) second.

With reference to <FIG>, it is described that the spatial light modulator <NUM> outputs light having image information by modulating light, but example embodiments are not limited thereto. For example, the light source <NUM> may output light having image information under the control of the processor <NUM>. In this case, the spatial light modulator <NUM> may not be used, and the direction adjustment member <NUM> may be an actuator for controlling the position of the light source <NUM> or an optical device for adjusting the traveling path of light output from the light source <NUM>.

The Fourier-beam shaper <NUM> receives a plurality of light beams from the beam output device <NUM> and outputs the plurality of light beams through different regions thereof to form a frame image in an external space. Referring to <FIG>, the Fourier-beam shaper <NUM> includes a waveguide <NUM>, an input coupler <NUM> that guides a plurality of light beams to the inside of the waveguide <NUM>, and an spatial converter <NUM> configured such that the light beams traveling in the waveguide <NUM> may be output through spatially different regions of the spatial converter <NUM>.

The waveguide <NUM> may include a transparent member such as a glass material or a transparent plastic material and diameters of a light beam incident on the waveguide <NUM> may vary while the light beam travels in the waveguide <NUM> by total reflection. Thus, the diameter of a light beam incident on the input coupler <NUM> may be different from the diameter of a light beam output through the spatial converter <NUM>. Light output from the beam output device <NUM> may be dot-type light, but the light traveling in the waveguide <NUM> may be surface-type light because the beam diameter of the light increases while being repeatedly totally reflected in the waveguide <NUM>. In addition, light may be uniformly distributed while traveling in the waveguide <NUM>. Thus, the diameter of a light beam output through the spatial converter <NUM> may be greater than the diameter of a light beam incident on the input coupler <NUM>.

The input coupler <NUM> may be arranged in a region of the waveguide <NUM>. In <FIG>, the input coupler <NUM> is illustrated as being located on an edge portion of the upper surface of the waveguide <NUM>, but is not limited thereto. Alternatively, the input coupler <NUM> may be arranged in a lower region of the waveguide <NUM>. The input coupler <NUM> may include a diffraction member BD that diffracts and transmits light incident on the input coupler <NUM>. For example, the input coupler <NUM> may include a grating structure. The input coupler <NUM> may have diffraction characteristics to diffract and transmit incident light regardless of the incident angle of the incident light.

The spatial converter <NUM> includes a plurality of selective transmission elements ST such that a plurality of light beams traveling in the waveguide <NUM> may be output through spatially different regions of the spatial converter <NUM>. The selective transmission elements ST may be two-dimensionally arranged on the waveguide <NUM>. The selective transmission elements ST may be continuously arranged or discontinuously arranged.

Each of the selective transmission elements ST transmits one of a plurality of light beams to the outside and blocks the remaining light beams of the plurality of light beams. Each of the selective transmission elements ST may transmit or may not transmit light according to the optical characteristics thereof. For example, each of the selective transmission elements ST may transmit or may not transmit light according to the diffraction characteristics thereof. Alternatively, each of the selective transmission elements ST may transmit or may not transmit light as the optical characteristics thereof are changed by an electrical signal applied to the selective transmission elements ST.

Each of the plurality of selective transmission elements ST may direct light in a specific direction and output the light. For example, at least two of the selective transmission elements ST may direct and output light in different directions when light passing therethrough. The degree of directivity of the selective transmission elements ST may be determined by optical characteristics of the selective transmission elements ST such as diffraction characteristics, and the optical characteristics of the selective transmission elements ST may be changed by an electrical signal applied to the selective transmission elements ST.

The time required for the spatial converter <NUM> to output all of a plurality of light beams forming a frame image may be equal to the output period of the frame image, that is, a frame time. For example, n light beams corresponding to one frame image may be output at intervals of <NUM>/n of the frame time by the beam output device <NUM>. Each of the plurality of selective transmission elements ST may direct and output one of the n light beams. Based on all of the n light beams that are output, a user may recognize the frame image. Since the n light beams are formed in different regions of an external space, for example, a pupil E of a user, the user may recognize the n light beams as one image.

In the related art structure in which a frame image of the same phase is incident on a waveguide, the distance between the waveguide and a beam output device may need to be equal to or greater than a certain value. However, since the Fourier-beam shaper <NUM> independently receives light and outputs the light, the distance between the beam output device <NUM> and the Fourier-beam shaper <NUM> is not limited. This makes it possible to reduce the distance between the beam output device <NUM> and the Fourier-beam shaper <NUM>. In addition, since the Fourier-beam shaper <NUM> forms a frame image by outputting a plurality of light beams through different regions of the Fourier-beam shaper <NUM>, the display apparatus <NUM> may display the frame image simply by outputting light beams using the beam output device <NUM>. Thus, the light source <NUM> and the spatial light modulator <NUM> included in the beam output device <NUM> may have small sizes. In addition, since each of the selective transmission elements ST of the Fourier-beam shaper <NUM> directs light in a certain direction, an additional optical device such as a lens may not be required. Therefore, the display apparatus <NUM> may have a simple structure.

<FIG> is a view illustrating examples of the selective transmission elements ST of the spatial converter <NUM> according to an example embodiment of the invention.

As shown in <FIG>, the selective transmission elements ST may include diffraction members having a grating structure. Each of the selective transmission elements ST may have a grating G, and one or more of a shape, a pitch (p), a height (h), a direction (d), a material, and/or the like of the grating G may be varied among the selective transmission elements ST. Thus, the diffraction efficiency of each of the selective transmission elements ST may vary according to the incident angle of light. In <FIG>, the gratings G of the selective transmission elements ST have different directions, but example embodiments are not limited thereto.

For example, the diffraction efficiency of each of the selective transmission elements ST may be equal to or greater than a first reference value corresponding to light which is incident at a certain incident angle and may be less than a second reference value corresponding to light incident at the other incident angles. Here, the second reference value may be equal to or less than the first reference value. Thus, each of the selective transmission elements ST of the spatial converter <NUM> may diffract and transmit light incident at a certain incident angle, and may totally reflect, into the waveguide <NUM>, light incident at an incident angle different from the certain incident angle. Since the selective transmission elements ST are capable of selectively diffracting and transmitting a plurality of light beams, the spatial converter <NUM> may output light through different regions thereof.

When transmitting light, each of the selective transmission elements ST may output the light in a certain direction. The degree of directivity of each of the selective transmission elements ST may be determined depending on the incident angle of light, the diffraction characteristics of the selective transmission element ST such as the grating structure of the selective transmission element ST, or the material of the selective transmission element ST.

Although it is mentioned that the diffraction characteristics of each of the selective transmission elements ST are dependent on factors such as the shape, pitch (p), height (h), direction (d), or material of the grating (G) of the selective transmission element ST, the selective transmission elements ST are not limited thereto. For example, the diffraction characteristics of the selective transmission elements ST may be varied by an electrical signal applied to the selective transmission elements ST.

<FIG> is a view illustrating a portion of a Fourier-beam shaper including selective transmission elements according to another example embodiment of the invention.

As shown in <FIG>, a spatial converter <NUM> of the Fourier beam shaper may include: an output coupler <NUM> arranged on a waveguide <NUM> and the selective transmission elements ST arranged on the output coupler <NUM>. The output coupler <NUM> may include a grating structure that diffracts and transmits light.

The transmittance of each of the selective transmission elements ST may be varied according to an electrical signal applied thereto. Each of the selective transmission elements ST may include: a base layer <NUM>; a plurality of electro-optical particles <NUM> which are dispersed in the base layer <NUM> and have optical characteristics varying according to an electrical signal applied thereto; and electrode portions <NUM> for applying an electrical signal to the electro-optical particles <NUM>.

The base layer <NUM> may include a transparent polymer material. For example, the base layer <NUM> may include a transparent cured resin.

The electro-optical particles <NUM> may include materials having an electro-optical effect. The electro-optical effect refers to a phenomenon in which optical characteristics are varied according to an electric field, and the characteristics of the electro-optical particles <NUM>, such as refractive index, phase retardation, or polarization characteristics, may be varied depending on the existence of an electric field and/or the strength of an electric field.

The electro-optical particles <NUM> may include liquid crystal. At least one of the refractive index and polarization characteristics of the liquid crystal may be varied according to the existence of an electric field and/or the strength of the electric field. For example, the electro-optical particles <NUM> may include polymer dispersed liquid crystal (PDLC), polymer network liquid crystal (PNLC), cholesteric liquid crystal, smectic liquid crystal, or the like.

When an electric field is applied to the base layer <NUM>, the electro-optical particles <NUM> may refract incident light equally, and thus, the electro-optical particles <NUM> may be transparent. Thus, the electro-optical particles <NUM> may transmit incident light. That is, when an electrical signal is applied to the selective transmission elements ST, the selective transmission elements ST enter into a transmission mode and transmit light.

Conversely, when no electric field is applied to the base layer <NUM>, the electro-optical particles <NUM> refracts incident light with different refractive indexes in different directions according to the position (or an incident angle) of the incident light, and thus the electro-optical particles <NUM> may be opaque. Thus, the electro-optical particles <NUM> may not transmit incident light by scattering the incident light. That is, when no electrical signal is applied to the selective transmission elements ST, the selective transmission elements ST enter into a non-transmission mode and do not transmit light.

In another example, when an electric field is applied to the electro-optical particles <NUM>, the electro-optical particles <NUM> may enter into a non-transmission mode in which the electro-optical particles <NUM> refract light with different refractive indexes in different directions according to the position of the light, and when no electric field is applied to the electro-optical particles <NUM>, the electro-optical particles <NUM> may enter into a transmission mode in which the electro-optical particles <NUM> refract light equally.

In an example embodiment, according to an electrical signal applied to the selective transmission elements ST, one of the selective transmission elements ST may enter into a transmission mode to output light diffracted from the output coupler <NUM>, and another one of the selective transmission elements ST may enter into a non-transmission mode so as not to output light diffracted from the output coupler <NUM>. An electrical signal may be synchronized with light output from the beam output device <NUM>, and the selective transmission elements ST are capable of selectively transmitting light based on the electric signal. Thus, the spatial converter <NUM> may output light through spatially different regions thereof.

<FIG> is a view illustrating a method of selectively outputting a plurality of light beams through a plurality of selective transmission elements ST according to an example embodiment of the invention.

As illustrated in <FIG>, light may be incident on an input coupler <NUM> at a certain incident angle. The input coupler <NUM> diffracts and transmits the light to a waveguide <NUM>. While traveling in the waveguide <NUM>, the light passes through one of the selective transmission elements ST which satisfies certain conditions, but does not pass through another one of the selective transmission elements ST.

For example, when the selective transmission elements ST are constituted by diffraction members having different diffraction characteristics, a selective transmission element ST having low diffraction efficiency with respect to the incident angle of light may totally reflect the incident light into the waveguide <NUM>, and a selective transmission element ST having high diffraction efficiency with respect to the incident angle of the light may diffract and transmit the incident light. Thus, the light may be output to the outside only through a portion of the selective transmission elements ST. For example, when a light beam L1 is incident at a first incident angle <NUM>, a first selective transmission element ST1 having high diffraction efficiency with respect to the first incident angle θ1 may diffract and transmit the light beam L1 but the other selective transmission elements ST may totally reflect the light beam L1 into the waveguide <NUM>. For example, when a light beam L2 is incident at a second incident angle θ2, a second selective transmission element ST2 having high diffraction efficiency with respect to the second incident angle θ2 may diffract and transmit the light beam L2 but the other selective transmission elements ST may totally reflect the light beam L2 into the waveguide <NUM>.

Alternatively, when the selective transmission elements ST include electro-optical particles <NUM> of which optical characteristics are varied by an electrical signal applied thereto, a selective transmission element ST entered into a transmission mode by an electrical signal may transmit incident light, and a selective transmission element ST entered into a non-transmission mode by the electrical signal may not transmit the incident light. Thus, the light may be output to the outside only through the selective transmission element ST which is in the transmission mode.

For example, the light beam L1 which is incident at a first incident angle θ1 may pass through the first selective transmission element ST1 which is in the transmission mode, but may be scattered or totally reflected into the waveguide <NUM> by the other selective transmission elements ST which are in the non-transmission mode. In addition, a light beam L2 which is incident at a second incident angle θ1 may pass through the second selective transmission element ST2 which is in the transmission mode, but may be scattered or totally reflected into the waveguide <NUM> by the other selective transmission elements ST which are in the non-transmission mode.

<FIG> is a view illustrating a display apparatus 10a according to another example embodiment of the invention.

Referring to <FIG> and <FIG>, the display apparatus 10a shown in <FIG> may further include an exit pupil expander <NUM>. The exit pupil expander <NUM> may expand light output from a Fourier-beam shaper <NUM> in one direction, for example, an x-axis direction. Although not shown in <FIG>, the exit pupil expander <NUM> may include a waveguide, an input coupler, and an output coupler. The input coupler and the output coupler of the exit pupil expander <NUM> may also include diffraction members. However, the input coupler and the output coupler of the exit pupil expander <NUM> may have diffraction characteristics for diffracting and transmitting light regardless of the incident angle of the light.

In addition, the exit pupil expander <NUM> may include a transparent material such that light corresponding to a reality environment R, for example, light reflected or generated in the reality environment R may be transmitted to the pupil E of a user through the exit pupil expander <NUM>. Thus, the user may simultaneously recognize a frame image formed by the Fourier-beam shaper <NUM> and the reality environment R. However, this is a non-limiting example. The exit pupil expander <NUM> may direct light output from only the Fourier-beam shaper <NUM> to the pupil E of the user.

Light beams as many as the number of selective transmission elements ST are required to form one frame image by using a single beam output device <NUM> and a single Fourier-beam shaper <NUM>. In addition, as the number of light beams increases, the output period of the light beams is shortened. This may increase a signal processing load of a processor <NUM>.

In some example embodiments, a display apparatus may form a frame image by using a plurality of beam output devices and a plurality of Fourier-beam shapers.

<FIG> is a view illustrating a display apparatus 10b according to another example embodiment of the invention.

The display apparatus 10b illustrated in <FIG> may include a plurality of beam output devices <NUM> and a plurality of Fourier-beam shapers <NUM>. Each of the plurality of beam output devices <NUM> may output a plurality of light beams to a corresponding Fourier-beam shaper <NUM>, and one frame image may be formed by a plurality of light beams output from the plurality of Fourier-beam shapers <NUM>.

Each of the beam output devices <NUM> may include a light source, a spatial light modulator, and/or a direction adjustment member, but is not limited thereto. Each of the beam output devices <NUM> is substantially the same as the beam output device <NUM> described with reference to <FIG>, and thus a detailed description thereof will be omitted.

Each of the Fourier-beam shapers <NUM> may also include a waveguide <NUM>, an input coupler <NUM>, and a spatial converter <NUM>. The input coupler <NUM> may be a diffraction member arranged in a region of the waveguide <NUM> to diffract and transmit incident light. For example, the input coupler <NUM> may have a grating structure and may have diffraction characteristics to diffract and transmit incident light regardless of the incident angle of the incident light.

The spatial converter <NUM> may include a plurality of selective transmission elements ST such that a plurality of traveling light beams may be output through spatially different regions (or different selective transmission elements ST) of the spatial converter <NUM>. The selective transmission elements ST may be one-dimensionally arranged on the waveguide <NUM>. However, this is a non-limiting example. Alternatively, the selective transmission elements ST may be two-dimensionally arranged.

The selective transmission elements ST may have different optical characteristics such that light satisfying certain conditions may pass through one or more of the selective transmission elements ST, and light not satisfying the conditions may not pass through the one or more of the selective transmission elements ST. The optical characteristics of the selective transmission elements ST may be determined during a manufacturing process of the selective transmission elements ST or may be varied according to an electrical signal applied to the selective transmission elements ST.

For example, the selective transmission elements ST may have diffraction characteristics. Each of the selective transmission elements ST may diffract and transmit light incident at a certain incident angle, but may totally reflect, into the waveguide <NUM>, light incident at an incident angle different from the certain incident angle. Since the selective transmission elements ST are capable of selectively diffracting and transmitting a plurality of light beams, the spatial converter <NUM> may output light through different regions thereof.

Alternatively, the selective transmission elements ST may include electro-optical particles <NUM> of which optical characteristics are varied by an electrical signal applied thereto. Each of the selective transmission elements ST may transmit incident light in a transmission mode and may scatter or totally reflect incident light into the waveguide <NUM> in a non-transmission mode.

In addition, each of the selective transmission elements ST may direct light in a certain direction while transmitting the light. Thus, a plurality of light beams output from the spatial converters <NUM> may form a frame image in an external space. The external space may be a space inside the pupil E of a user.

Each of the beam output devices <NUM> may output a plurality of light beams to a corresponding Fourier-beam shaper <NUM>. The beam output devices <NUM> may be synchronized to output a plurality of light beams in the same time period, and the Fourier-beam shapers <NUM> may output a plurality of light beams in the same time period, thereby forming one frame image. For example, each of the Fourier-beam shapers <NUM> may form a line frame image by outputting light through different regions thereof, and one frame may be formed by line frame images respectively formed by the Fourier-beam shapers <NUM>.

Each of the beam output devices <NUM> may output light beams as many as the number of selective transmission elements ST of a corresponding Fourier-beam shaper <NUM>, and one frame may be formed by a plurality of light beams output from the Fourier-beam shapers <NUM>. Thus, the output period of light beams may be increased compared to the case in which one frame image is formed using one light source and one Fourier-beam shaper. Thus, the load of a processor <NUM> may be reduced.

<FIG> is a view illustrating a display apparatus 10c according to another example embodiment of the invention.

The display apparatus 10c of <FIG> may include: a first beam output device <NUM> and a second beam output device <NUM> each outputting a plurality of light beams; a first Fourier-beam shaper <NUM> and a second Fourier-beam shaper <NUM> each forming a half frame image using the light beams output from the first beam output device <NUM> and the second beam output device <NUM>, respectively. Since each of the first and the second Fourier-beam shapers <NUM> and <NUM> forms a half frame image to form one frame image, the output period of light beams may be increased compared to the case in which one frame image is formed using one light source and one Fourier-beam shaper.

With reference to <FIG> and <FIG>, it is described that each of the Fourier-beam shapers <NUM>, and <NUM> forms a partial image of a frame image, such as a line frame image or a half frame image. However, this is a non-limiting example. Fourier-beam shapers and the beam output devices may be variously combined to form a partial image. For example, one frame image may be formed based on quarter frame images formed by four beam output devices and four Fourier-beam shapers.

The display apparatus 10c shown in <FIG> may further include an exit pupil expander <NUM>. The exit pupil expander <NUM> may expand a light beam output from the first Fourier-beam shaper <NUM> and a light beam output from the second Fourier-beam shaper <NUM>.

<FIG> is a view illustrating a portion of a display apparatus 10d according to another example embodiment of the invention.

Referring to <FIG>, a first waveguide <NUM> of a first Fourier-beam shaper 202a, and a second waveguide <NUM> of a second Fourier-beam shaper 203a may partially overlap each other in a direction perpendicular to the length direction of the first and the second waveguides <NUM> and <NUM>, for example, in an Y-axis direction. As the lengths of the first and the second waveguides <NUM> and <NUM> increase, the uniformity of light traveling in the first and the second waveguides <NUM> and <NUM> may increase.

The display apparatus 10d shown in <FIG> may further include an exit pupil expander <NUM> that may expand light beams output from the first Fourier-beam shaper 202a and the second Fourier-beam shaper 203a.

<FIG> is a view illustrating a display apparatus 10e including a Fourier-beam shaper 200b according to another example embodiment of the invention.

As shown in <FIG>, a beam output device 100b may include a light source <NUM>, a waveguide <NUM>, and a spatial light modulator 130b. The beam output device 100b may output light corresponding to a frame image by using the waveguide <NUM> and the spatial light modulator 130b. The Fourier-beam shaper 200b may include a plurality of selective transmission elements ST. The selective transmission elements ST may have different directivities according to regions in which the selective transmission elements ST are positioned, and may thus direct incident light in different directions. When the beam output device 100b outputs light corresponding to a frame image, the selective transmission elements ST of the Fourier-beam shaper 200b may transmit light while directing the light in specific directions according to the optical characteristics of the selective transmission elements ST. Thus, the frame image may be formed in an external space.

The display apparatus 10e shown in <FIG> may further include an exit pupil expander <NUM> that may expand a light beam output from the first Fourier-beam shaper 200b.

In the above description of the invention, it is assumed that light having image information is incident on a Fourier-beam shaper. In an example not covered by the invention, image information may be added to light output from a Fourier-beam shaper, or a Fourier-beam shaper may include a spatial light modulator configured to add image information.

<FIG> is a schematic view illustrating a display apparatus 10f configured to add an image to Fourier-transformed light according to another example embodiment not covered by the invention.

As illustrated in <FIG>, a Fourier-beam shaper <NUM> may output a plurality of light beams received from a light source <NUM> as spatially separated light beams, that is, Fourier-transformed light beams. The Fourier-beam shaper <NUM> may include a waveguide, an input coupler configured to direct a plurality of light beams into the waveguide, and a spatial converter configured such that the light beams traveling in the waveguide may be output through different regions of the spatial converter. The spatial converter may include a plurality of selective transmission elements such that the light beams traveling in the waveguide may be output through spatially different regions of the spatial converter. The selective transmission elements may be continuously arranged or discontinuously arranged.

Each of the selective transmission elements may transmit one of the light beams to the outside and may block the other of the light beams according to the optical characteristics of each selective transmission element. The selective transmission elements may include a plurality of diffraction members having different diffraction characteristics, or may include a plurality of optical particles of which optical characteristics are variable according to an electrical signal applied thereto. The structure of the Fourier-beam shaper <NUM> is substantially the same as the Fourier-beam shaper <NUM> described above, and thus a detailed description thereof will be omitted.

Light emitted from the light source <NUM> may not have image information, and the Fourier-beam shaper <NUM> may output the light not having image information to different spaces. In addition, a spatial light modulator 130c may add image information to the light output from the Fourier-beam shaper <NUM>. The light output from the Fourier-beam shaper <NUM> is temporally and spatially separated light, and thus the spatial light modulator 130c may add image information to the temporally and spatially separated light which is incident thereon. Since light beams output from the spatial light modulator 130c are temporally and spatially separated sub-images, the display apparatus 10f of <FIG> may provide a frame image by focusing the sub-images.

<FIG> is a view illustrating a Fourier-beam shaper 200a including a spatial light modulator 130d according to an example embodiment not covered by the invention. As illustrated in <FIG>, the Fourier-beam shaper 200a includes: a waveguide 210a and a spatial converter 230a that are apart from each other; and the spatial light modulator 130d that are arranged between the waveguide 210a and the spatial converter 230a. An input coupler 211a on which light is incident from a light source (not shown) may be arranged on the waveguide 210a, and an output coupler 231a through which light traveling in the waveguide 210a is output to the spatial light modulator 130d may be arranged on the waveguide 210a.

Light output from the waveguide 210a may be modulated by the spatial light modulator 130d to have image information. The light having image information, that is, image light, is incident on the spatial converter 230a. Selective transmission elements included in the spatial converter 230a may transmit a specific light beam (e.g., light beam having a specific incident angle) and may block the other light beams according to the optical characteristics of the selective transmission elements. The optical characteristics of the selective transmission elements may be variable according to an electrical signal applied thereto, or may not be variable. The optical characteristics may be diffraction characteristics, scattering characteristics, reflection characteristics, refraction characteristics, or the like.

According to an example embodiment, a display apparatus may be implemented as a single hardware device or a combination of a plurality of hardware devices. For example, the display apparatus may include: a slave including a light source unit and an optical scanner; and a master including a processor.

<FIG> is a block diagram illustrating a display apparatus <NUM> according to another example embodiment of the invention.

Referring to <FIG>, the display apparatus <NUM> may include: a slave S including a beam output device <NUM>, a Fourier-beam shaper <NUM>, and a first communication unit <NUM>; and a master M including a second communication unit <NUM> and a processor <NUM>. The beam output device <NUM> and the Fourier-beam shaper <NUM> have the same structures as those described above, and thus detailed descriptions thereof will be omitted. The slave S may be implemented as a wearable device such as a head mounted display apparatus, and the master M may be an electronic device such as a cellular phone or a computer which is separate from the wearable device.

The first and the second communication units <NUM> and <NUM> may provide control commands of the processor <NUM> to the beam output device <NUM> and the Fourier-beam shaper <NUM>. The first and the second communication units <NUM> and <NUM> may include a short-range wireless communication unit, a mobile communication unit, or the like. The first and the second communication units <NUM> and <NUM> may communicate with each other by using various wired or wireless communication techniques such as Bluetooth communication, Bluetooth Low Energy (BLE) communication, Near Field Communication (NFC), WLAN communication, Zigbee communication, Infrared Data Association (IrDA) communication, Wi-Fi Direct (WFD) communication, Ultra-Wideband (UWB) communication, Ant+ communication, Wi-Fi communication, Radio Frequency Identification (RFID) communication, third generation (<NUM>), fourth generation (<NUM>), and fifth generation (<NUM>) communications, and the like. However, these are merely examples and are not intended to be limiting.

A method of controlling the beam output device <NUM> and the Fourier-beam shaper <NUM> by using the processor <NUM> may be implemented as a software program including instructions stored in a computer-readable storage medium. A computer may read the instructions from the storage medium and may perform operations based on the read instructions according to embodiments, and may include the display apparatus of any one of the above-described embodiments. Examples of the computer-readable storage medium include a read only memory (ROM), a random access memory (RAM), a compact disc (CD)-ROM, a magnetic tape, a floppy disc, and an optical data storage. The computer-readable recording medium may be distributed over a plurality of computer systems connected to a network so that a computer-readable code is written thereto and executed therefrom in a decentralized manner. Functional programs, codes, and code segments needed for implementing the disclosure may be readily deduced by a person of ordinary skill in the art.

Although not illustrated in <FIG>, an exit pupil expander may be arranged to expand light corresponding to an image in one direction.

Any one of the display apparatuses <NUM>, 10a, 10b, 10c, 10d, 10e, 10f, and <NUM>, and the Fourier-beam shapers <NUM> and 200a may be used as a component of a wearable device. For example, any one of the display apparatuses <NUM>, 10a, 10b, 10c, 10d, 10e, 10f, and <NUM> may be applied to head mounted displays (HMDs). In addition, any one of the display apparatuses <NUM>, 10a, 10b, 10c, 10d, 10e, 10f, and <NUM> may be applied to glasses-type displays or goggle-type displays. Wearable electronic devices may operate in an interacting relationship with (or in connection with) smartphones. <FIG> and <FIG> are views illustrating electronic devices to which the display apparatuses of the example embodiments of the invention may be applied.

While the Fourier-beam shapers and the display apparatuses including the Fourier-beam shapers have been described according to the example embodiments with reference to the accompanying drawings, the descriptions are provided for illustrative purposes only, and it will be understood by those of ordinary skill in the art that various changes and other equivalent embodiments may be made therefrom.

At least one of the components, elements, modules or units described herein may be embodied as various numbers of hardware, software and/or firmware structures that execute respective functions described above, according to an example embodiment. For example, at least one of these components, elements or units may use a direct circuit structure, such as a memory, a processor, a logic circuit, a look-up table, etc. that may execute the respective functions through controls of one or more microprocessors or other control apparatuses. Also, at least one of these components, elements or units may be specifically embodied by a module, a program, or a part of code, which contains one or more executable instructions for performing specified logic functions, and executed by one or more microprocessors or other control apparatuses. Also, at least one of these components, elements or units may further include or implemented by a processor such as a central processing unit (CPU) that performs the respective functions, a microprocessor, or the like. Two or more of these components, elements or units may be combined into one single component, element or unit which performs all operations or functions of the combined two or more components, elements of units. Also, at least part of functions of at least one of these components, elements or units may be performed by another of these components, element or units. Further, although a bus is not illustrated in the block diagrams, communication between the components, elements or units may be performed through the bus. Functional aspects of the above example embodiments may be implemented in algorithms that execute on one or more processors. Furthermore, the components, elements or units represented by a block or processing operations may employ any number of related art techniques for electronics configuration, signal processing and/or control, data processing and the like.

Claim 1:
A display apparatus (<NUM>) comprising:
a beam output device (<NUM>) comprising a light source (<NUM>) and a direction adjustment member (<NUM>), the beam output device (<NUM>) being configured to time-sequentially output a plurality of light beams corresponding to a frame image, wherein each of the plurality of light beams corresponds to a partial image of the frame image, and wherein the direction adjustment member (<NUM>) is configured to adjust the traveling path of each of the plurality of light beams, such that the plurality of light beams proceed in different traveling paths;
a waveguide (<NUM>);
an input coupler (<NUM>) configured to time-sequentially direct the plurality of light beams into the waveguide (<NUM>); and
a spatial converter (<NUM>) configured to output the plurality of light beams traveling in the waveguide (<NUM>) through spatially different regions of the spatial converter (<NUM>) to form the frame image in an external space,
wherein the spatial converter (<NUM>) comprises a plurality of selective transmission elements (ST) arranged in a first direction, the first direction crossing directions in which the plurality of light beams are output,
wherein each of the plurality of selective transmission elements (ST) is configured to transmit one of the plurality of light beams to the external space and not to transmit remaining light beams of the plurality of light beams to the external space, and
wherein a number of the plurality of light beams and a number of the plurality of selective transmission elements are equal.