CN116762024A - Display device with transparent illuminator - Google Patents

Abstract

A display device having a transparent illuminator and a Liquid Crystal (LC) display panel is disclosed. The transparent luminaire comprises a light source and a transparent light guide, which may be based on a slab of transparent material with saw-tooth light propagation of illumination light in the slab and/or a transparent photonic integrated circuit with single-mode ridge waveguides for spreading the illumination light in a plane parallel to the plane of the LC display panel. The light guide comprises a plurality of grating couplers whose positions are coordinated with the positions of the LC pixels for higher throughput. Reflective offset-to-angle optics may be provided to form an image in the angular domain through the LC panel and transparent illuminator, resulting in an overall compact and efficient display configuration.

Description

Display device with transparent illuminator

Cross Reference to Related Applications

The present application claims priority from U.S. provisional patent application No. 63/121,494, entitled "Patterned Backlight for Display Panel (patterned backlight for display panel)" filed on month 12 and 4 of 2020, and the present application extends over the section of U.S. patent application No. 17/321,121, entitled "Patterned Backlight for Display Panel (patterned backlight for display panel)" filed on month 5 and 14 of 2021, which claims priority from U.S. provisional patent application No. 63/121,494, entitled "Patterned Backlight for Display Panel (patterned backlight for display panel)" filed on month 12 and 4 of 2020, the entire contents of all of which are incorporated herein by reference.

Technical Field

The present disclosure relates to visual display devices and related components and modules.

Background

Visual displays provide information to the viewer(s), including still images, video, data, and the like. Visual displays have applications in different fields including entertainment, education, engineering, science, professional training, advertising, to name a few. Some visual displays (e.g., televisions) display images to multiple users, while some visual display systems (e.g., near-eye displays (NEDs)) are intended for use by individual users.

An artificial reality system typically includes a NED (e.g., a headset) or a pair of glasses configured to present content to a user. The near-eye display may display the virtual object or combine an image of the real object with the virtual object as in a Virtual Reality (VR) application, an augmented reality (augmented reality, AR) application, or a Mixed Reality (MR) application. For example, in an AR system, a user may view an image (e.g., a computer-generated image (CGI)) of a virtual object superimposed with the surrounding environment through a perspective "combiner" component. The combiner of the wearable display is typically transparent to the external light, but includes some light routing devices to direct the display light into the user's field of view.

Because the display of an HMD or NED is typically worn on the head of a user, a large, bulky and heavy, unbalanced and/or heavy display device with heavy batteries would be cumbersome and uncomfortable for the user to wear. Thus, a head mounted display device may benefit from a compact and efficient construction that includes an efficient illuminator that provides uniform illumination of the display panel, as well as high throughput visual lenses and other optical elements.

According to the present invention there is provided a display device comprising an illuminator comprising a light source, a transparent light guide for diffusing light emitted by the light source along a plane parallel to the transparent light guide, and a Liquid Crystal (LC) layer optically coupled to the transparent light guide to couple out portions of the light propagating in the transparent light guide, the LC layer being located downstream of the illuminator, the LC layer comprising an array of polarization tuning pixels, wherein the positions of the gratings are coordinated with the positions of the polarization tuning pixels such that portions of the light coupled out of the transparent light guide by the gratings propagate through the corresponding polarization tuning pixels.

Optionally, the gratings are configured to focus portions of light at least partially through corresponding polarization tuning pixels.

Optionally, the light source is configured to emit light of a first polarization state, wherein the transparent light guide substantially retains the first polarization state of the light emitted by the light source.

Optionally, the light source is configured to emit light of a wavelength of the first color channel.

Optionally, the light source is configured to emit light of a wavelength of the second color channel, and optionally of a wavelength of the third color channel, wherein, in operation, the light of the first color channel, the light of the second color channel and the light of the third color channel are emitted in a time sequential manner.

Optionally, the display device further comprises at least one of: a grid layer adjacent to the LC layer for defining boundaries of polarization tuning pixels of the polarization tuning pixel array; or a substrate adjacent to the liquid crystal layer, the substrate comprising an array of transparent electrode segments defining the polarization-tuned pixel array.

Optionally, the display device further comprises a polarizer downstream of the LC layer for transmitting light of a first polarization state and rejecting light of a second, orthogonal polarization state.

Optionally, the display device further comprises an eyebox downstream of the LC layer. Optionally, the display device further comprises an offset-to-angle element (offset-to-angle element) in the optical path between the LC layer and the eyebox for converting an image of the LC layer in the linear domain into an image of the eyebox in the angular domain.

Optionally, the offset-to-angle element is configured to redirect portions of light propagating through the LC layer back through the transparent light guide to form an image in an angular domain, wherein the eyebox and the offset-to-angle element are disposed on opposite sides of the transparent light guide.

Alternatively, the offset-to-angle element may comprise a first component comprising a reflective polarizer and optionally a second component downstream of the first component, the second component comprising a reflector layer. Optionally, in operation, portions of the coupled-out light propagate through the reflective polarizer, are reflected by the reflector layer, propagate back to the reflective polarizer and are reflected thereby, propagate again to the reflector layer and are reflected thereby, propagate back through the transparent light guide, and form an image in the angular domain at the eyebox.

Optionally, the reflector layer comprises a total reflector.

Optionally, the reflector layer comprises a partial reflector. Optionally, the display device further comprises an eye tracking camera located behind the partial reflector for capturing an image of the user's eye at the eyebox through the offset-to-angle element.

Optionally, the transparent light guide comprises a plate of transparent material for propagating light in the plate in a zigzag pattern by a series of successive total internal reflections from opposite parallel surfaces of the plate, wherein the grating array is supported by the plate.

Optionally, the transparent light guide comprises: a substrate, a scheduling circuit, and a linear waveguide array, the scheduling circuit being supported by the substrate; the linear waveguide array is supported by the substrate and extends along polarization tuning pixels of the polarization tuning pixel array; wherein the scheduling circuit is configured to receive light from the light source and split the light between a plurality of linear waveguides; and wherein the gratings are optically coupled to the linear waveguides for coupling out portions of light from the plurality of linear waveguides to propagate through corresponding polarization tuning pixels of the polarization tuning pixel array.

According to the present invention, there is also provided a display device including: an illuminator comprising a light source, a plate of transparent material coupled to the light source for propagating light in the plate in a zigzag pattern by a series of successive total internal reflections from opposite parallel surfaces of the plate, and a Liquid Crystal (LC) layer supported by the plate to couple out portions of the light propagating in the plate; the liquid crystal layer is optically coupled to the illuminator, the LC layer comprising an array of polarization-tuned pixels, wherein the positions of the gratings are coordinated with the positions of the polarization-tuned pixels such that portions of light coupled out of the slab of transparent material by the gratings propagate through the corresponding polarization-tuned pixels.

Optionally, the display device further comprises an eyebox downstream of the LC layer. Optionally, the display device further comprises a reflective offset-to-angle element located in the optical path between the LC layer and the eyebox for converting an image of the LC layer in the linear domain into an image of the eyebox in the angular domain. Optionally, the reflective offset-to-angle element is configured to redirect portions of light propagating through the LC layer back through the flat sheet of transparent material to form an image in an angular domain, wherein the eyebox and the offset-to-angle element are disposed on opposite sides of the flat sheet of transparent material.

Alternatively, the offset-to-angle element may comprise a first component comprising a reflective polarizer and optionally a second component downstream of the first component, the second component comprising a reflector layer. Optionally, in operation, portions of the coupled-out light propagate through the reflective polarizer, are reflected by the reflector layer, propagate back to the reflective polarizer and are reflected thereby, propagate again to the reflector layer and are reflected thereby, propagate back through the flat sheet of transparent material, and form an image in the angular domain at the eyebox.

According to the present invention there is also provided a display device comprising an illuminator and a Liquid Crystal (LC) layer, the illuminator comprising a light source and a transparent light guide, the transparent light guide comprising a substrate, a scheduling circuit supported by the substrate, an array of linear waveguides supported by the substrate, and a grating array optically coupled to the array of linear waveguides, wherein the scheduling circuit is configured to receive light from the light source and split light emitted by the light source between a plurality of linear waveguides, and wherein the gratings are configured to couple out portions of light from the plurality of linear waveguides; the LC layer is optically coupled to the illuminator, the LC layer comprising an array of polarization-tuned pixels, wherein the linear waveguides extend along the polarization-tuned pixels of the LC layer; wherein the positions of the gratings are coordinated with the positions of the polarization tuning pixels such that portions of the light beam coupled out of the linear waveguide by the gratings propagate through the corresponding polarization tuning pixels.

Optionally, the display device further comprises an eyebox downstream of the LC layer. Optionally, the display device further comprises a reflective offset-to-angle element in the optical path between the LC layer and the eyebox for converting an image of the LC layer in the linear domain to an image of the eyebox in the angular domain. Optionally, the reflective offset-to-angle element is configured to redirect portions of light propagating through the LC layer back through the transparent light guide to form an image in an angular domain, wherein the eyebox and the offset-to-angle element are disposed on opposite sides of the transparent light guide.

Alternatively, the reflective offset to angle element may comprise a first component comprising a reflective polarizer and optionally a second component downstream of the first component, the second component comprising a reflector layer. Optionally, in operation, portions of the coupled-out light propagate through the reflective polarizer, are reflected by the reflector layer, propagate back to the reflective polarizer and are reflected thereby, propagate again to the reflector layer and are reflected thereby, propagate back through the transparent light guide, and form an image in the angular domain at the eyebox.

Drawings

Exemplary embodiments will now be described in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of a display device including a polarization-tuned pixel array;

FIG. 2 is an enlarged view of FIG. 1 showing a grating focusing the out-coupled light to pass through the polarization-tuned pixel;

FIG. 3 is a schematic cross-sectional view of a display device having reflective offset to angle elements;

FIG. 4A is a schematic cross-sectional view of the display device embodiment of FIG. 3, showing a detailed configuration of the reflective offset to angle element;

FIG. 4B is an optical polarization diagram illustrating continuous light propagation through the reflective offset-to-angle element of FIG. 4A;

FIG. 5A is a side cross-sectional view of a transparent illuminator based on two flat panel light guides with one-dimensional (1D) beam expansion;

FIG. 5B is a top view of the transparent illuminator of FIG. 5A;

FIG. 6 is a top view of a transparent illuminator based on a flat panel light guide with two-dimensional (2D) beam expansion;

fig. 7 is a top view of a photonic integrated circuit (photonic integrated circuit, PIC) based transparent illuminator;

FIG. 8 is a view of an Augmented Reality (AR) display of the present disclosure having a form factor of a pair of glasses; and

fig. 9 is a three-dimensional view of a head-mounted display (HMD) of the present disclosure.

Detailed Description

While the present teachings are described in connection with various embodiments and examples, the present teachings are not intended to be limited to these embodiments. On the contrary, the present teachings encompass various alternatives and equivalents, as will be appreciated by those of skill in the art. All statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Furthermore, such equivalents are intended to include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

As used herein, unless explicitly stated otherwise, the terms "first," "second," and the like are not intended to imply a sequential ordering, but rather to distinguish one element from another. Similarly, the sequential ordering of method steps does not imply an order in which they are performed unless explicitly stated. In fig. 1 to 3, 4A to 4B, and 5 to 8, like reference numerals generally denote like elements.

In a visual display comprising an array of pixels coupled to an illuminator, the efficiency of light utilization depends on the ratio of the geometric area occupied by the pixels to the total area of the display panel. For micro-displays, which are typically used for near-eye displays and/or head-mounted displays, this ratio may be below 50%. Efficient backlight utilization may be further hindered by color filters on the display panel that transmit no more than 30% of the incident light on average. In addition, for polarization-based display panels (e.g., liquid Crystal (LC) display panels), there may be a 50% loss of polarization. All of these factors greatly reduce the light utilization and overall photoelectric conversion efficiency of the display (wall plug efficiency), which is undesirable.

In accordance with the present disclosure, light utilization and photoelectric conversion efficiency of a backlight display may be improved by providing an illuminator comprising a transparent waveguide supporting an array of grating couplers aligned with pixels of a display panel. The center wavelength of the light emitted by the illuminator may be selected to match the transmission wavelength of the color sub-pixel, thereby increasing throughput. Furthermore, in displays where the illuminator emits primary colors (e.g., red, green, and blue) of light, the color filter layer may be omitted entirely. For polarization-based displays, the polarization of the emitted light may be matched to a predefined input polarization state. Matching the spatial distribution, transmission wavelength and transmission polarization characteristics of the pixels of the display panel can significantly improve the useful portion of the display light (which is not absorbed or reflected by the display panel on its way to the observer's eye) and thus significantly increase the photoelectric conversion efficiency of the display.

The transparency of the light guide-based illuminator of the present disclosure enables configurations in which the visual lens that converts an image in the linear domain displayed by the pixel array to an image in the angular domain at the eyebox can be replaced with a visual reflector that reflects illumination light back through the transparent light guide. This results in a more compact overall construction and can further increase the photoelectric conversion efficiency of the display compared to, for example, a display having a wafer-type visual lens with an optical throughput of typically no more than 25%. For VR display applications, the transparency of the light guide-based illuminator enables new display configurations, including, for example, eye tracking systems disposed behind the display panel in the direct field of view of the user's eyes.

According to the present disclosure, there is provided a display device including an illuminator and a Liquid Crystal (LC) layer downstream of the illuminator. The illuminator includes a light source, a transparent light guide for diffusing light emitted by the light source along a plane parallel to the transparent light guide, and a grating array optically coupled to the transparent light guide for coupling out portions of the light propagating in the transparent light guide. The LC layer includes an array of polarization-tuned pixels. The position of the grating is coordinated with the position of the polarization tuning pixels such that portions of the light coupled out of the transparent light guide by the grating propagate through the corresponding polarization tuning pixels. The gratings may be configured to focus portions of light at least partially through corresponding polarization tuning pixels.

The light source may be configured to emit light of a first polarization state, and the transparent light guide may substantially maintain the first polarization state of the light emitted by the light source. The light source may be configured to emit light of the wavelength of one or several color channels. For example, the light source may be configured to emit light of a wavelength of the first color channel, light of a wavelength of the second color channel, and light of a wavelength of the third color channel. The light of the first color channel, the light of the second color channel, and the light of the third color channel may be emitted in a time sequential manner. In some embodiments, the display device further comprises a grid layer adjacent to the LC layer for defining boundaries of polarization tuning pixels of the polarization tuning pixel array and/or a substrate adjacent to the LC layer, the substrate comprising an array of transparent electrode segments defining the polarization tuning pixel array.

A polarizer may be disposed downstream of the LC layer for transmitting light of a first polarization state and rejecting light of a second, orthogonal polarization state. The display device may further include an eyebox located downstream of the LC layer, and a shift-to-angle element (e.g., a visual lens) disposed in the optical path between the LC layer and the eyebox for converting an image of the LC layer in a linear domain to an image of the eyebox in an angular domain. The offset-to-angle element may be configured to redirect portions of light propagating through the LC layer back through the transparent light guide to form an image in the angular domain. In this configuration, the eyebox and offset-to-angle elements of this embodiment are disposed on opposite sides of the transparent light guide.

The offset-to-angle element may include a first component including a reflective polarizer and a second component downstream of the first component, the second component including a reflector layer. In operation, portions of the coupled-out light may propagate through the reflective polarizer, be reflected by the reflector layer, propagate back to the reflective polarizer and be reflected thereby, propagate again to the reflector layer and be reflected thereby, propagate back through the transparent light guide, and form an image in the angular domain at the eyebox. The reflector layer may comprise a total reflector, i.e. such a reflector: substantially no light is transmitted through the reflector. The reflector may also be a partial reflector that transmits some light. In such embodiments, the display device may further comprise an eye tracking camera located behind the partial reflector for capturing an image of the user's eye at the eyebox through the offset-to-angle element.

The transparent light guide may comprise a flat sheet of transparent material for propagating light in the flat sheet in a zigzag pattern by a series of successive total internal reflections from opposite parallel surfaces of the flat sheet. The grating array is supported by a flat plate. In some embodiments, a transparent light guide includes a substrate, a scheduling circuit supported by the substrate, and an array of linear waveguides supported by the substrate and extending along polarization tuning pixels of the array of polarization tuning pixels. The scheduling circuit is configured to receive light from the light source and separate the light between the linear waveguides, and the grating is optically coupled to the linear waveguides to couple out portions of the light from the linear waveguides to propagate through corresponding polarization-tuned pixels of the polarization-tuned pixel array.

According to the present disclosure, a display device is provided that includes an illuminator and an LC layer optically coupled to the illuminator. The illuminator comprises: a light source; a plate of transparent material coupled to the light source for propagating light in the plate in a zigzag pattern by a series of successive total internal reflections from opposite parallel surfaces of the plate; and a grating array supported by the plate for coupling out portions of light propagating in the plate. The LC layer includes an array of polarization-tuned pixels. The positions of the gratings are coordinated with the positions of the polarization tuning pixels such that portions of the light coupled out of the slab of transparent material by the gratings propagate through the corresponding polarization tuning pixels.

The display device may further include an eyebox located downstream of the LC layer, and a reflective offset-to-angle element located in the optical path between the LC layer and the eyebox for converting an image of the LC layer in a linear domain to an image of the LC layer in an angular domain at the eyebox. The reflective offset-to-angle element may be configured to redirect portions of light propagating through the LC layer back through the slab of transparent material to form an image in the angular domain. The eyebox and the offset-to-angle element are disposed on opposite sides of a flat sheet of transparent material.

In some embodiments, the reflective offset to angle element includes a first component including a reflective polarizer and a second component downstream of the first component, the second component including a reflector layer. In operation, portions of the coupled-out light propagate through the reflective polarizer, are reflected by the reflector layer, propagate back to the reflective polarizer and are reflected thereby, propagate again to the reflector layer and are reflected thereby, propagate back through the slab of transparent material, and form an image in the angular domain at the eyebox.

According to the present disclosure, there is also provided a display device comprising an illuminator and an LC layer optically coupled to the illuminator. The illuminator includes a light source and a transparent light guide including a substrate, a scheduling circuit supported by the substrate, a linear waveguide array supported by the substrate, and a grating array optically coupled to the linear waveguide array. The scheduling circuit is configured to receive light from the light source and separate light emitted by the light source between the linear waveguides, and wherein the grating is configured to couple out portions of the light from the linear waveguides. The LC layer includes an array of polarization-tuned pixels. The linear waveguide extends along the polarization-tuned pixels of the LC layer. The position of the grating is coordinated with the position of the polarization tuning pixels to propagate portions of the light beam coupled out of the linear waveguide through the grating through the corresponding polarization tuning pixels.

In some embodiments, the display device further comprises an eyebox located downstream of the LC layer, and a reflective offset-to-angle element located in the optical path between the LC layer and the eyebox for converting an image of the LC layer in the linear domain to an image of the eyebox in the angular domain. The reflective offset-to-angle element is configured to redirect portions of light propagating through the LC layer back through the transparent light guide to form an image in the angular domain. In this embodiment, the eyebox and the offset-to-angle element are disposed on opposite sides of the transparent light guide. The reflective offset to angle element may include a first component including a reflective polarizer and a second component downstream of the first component, the second component including a reflector layer. In operation, portions of the coupled-out light propagate through the reflective polarizer, are reflected by the reflector layer, propagate back to the reflective polarizer and are reflected thereby, propagate again to the reflector layer and are reflected thereby, propagate back through the transparent light guide, and form an image in the angular domain at the eyebox.

Referring now to fig. 1, a display device 100 includes an illuminator 102 having a light source 104, a transparent light guide 106 for diffusing light 108 emitted by the light source 104 along a plane parallel to the transparent light guide 106 (i.e., in the XY plane), and a grating array 110 optically coupled to the transparent light guide 106 to couple out portions 112 of the light 108 propagating in the transparent light guide 106. The gratings 110 may be directly supported by the transparent light guide 106, for example, the gratings may be immersed in the transparent light guide 106 as shown. The term "transparent light guide" herein refers to a light guide that propagates at least a useful portion of ambient light 114 (e.g., 10% or more of ambient light), as well as other light that may propagate directly through transparent light guide 106.

The display device 100 further comprises a Liquid Crystal (LC) layer 116 arranged downstream of the illuminator 102. LC layer 116 includes an array of polarization-tuned pixels 118 in a thin layer of LC fluid between a first substrate 121 and a second substrate 122 of LC cell 120. The polarization-tuning pixels 118 may be formed, for example, of an array of transparent electrode segments supported by a first substrate 121 and a common back-plate electrode supported by a second substrate 122. The first substrate 121 and/or the second substrate 122 may further include a grid layer 124 adjacent to the LC layer 116 for defining boundaries between the polarization-tuning pixels 118. Herein, the term "polarization tuning" includes polarization rotation, changing ellipticity and/or handedness of circularly or elliptically polarized light, etc.; in other words, any change in the polarization state of incident light may be controlled by applying an external signal to a specific pixel of LC layer 116.

In the display device 100, the position of the grating 110 is coordinated with the position of the polarization tuning pixels 118 such that portions 112 of the light 108 coupled out of the transparent light guide 106 through the grating 110 propagate through the corresponding polarization tuning pixels 118. Herein, the term "coordinated position" when applied to elements in two arrays of elements means that the positions of the elements of the two arrays in the XY plane overlap or correspond to each other, e.g., with equal X-pitch and Y-pitch, or more generally, the X-pitch of the first array is an integer multiple of the X-pitch of the second array and the Y-pitch of the first array is an integer multiple of the Y-pitch of the second array.

The display device 100 may also include a polarizer 128 downstream from the LC layer 116. Polarizer 128 may be configured to pass light of a first polarization state while rejecting light of a second, orthogonal polarization state. Portions 112 of light 108 propagating through polarization-tuning pixel 118 will be attenuated by polarizer 128 according to their respective polarization states, which may be controllably varied by polarization-tuning pixel 118. For example, the first polarization state may be linear polarization, e.g., Y polarization, and the second polarization state may be orthogonal linear polarization, i.e., X polarization, or vice versa. In other embodiments, the first polarization component may be left-hand circular polarization and the second polarization component may be right-hand circular polarization, or vice versa. To avoid polarization optical losses, the light source 104 may be configured to emit light 108 in a first polarization state. The transparent light guide may be configured to substantially maintain a polarization state of light as it spreads in the XY plane.

The display device 100 may also include a visual lens 130 positioned in the optical path between the LC layer 116 and the eyebox 126, downstream of the polarizer 128. The purpose of the vision lens 130 is to convert the image of the LC layer 116 in the linear domain into an image of the eyebox 126 over the angular domain where the user's eye can directly observe the image over the angular domain. More generally, the visual lens 130 is only one type of offset-to-angle visual element, which may be a refractive, reflective, and/or diffractive element having optical power (i.e., focusing or defocusing power). As its name implies, the offset-to-angle visual element performs the function of converting an image in the linear domain at LC layer 116 to an image on the angular domain at eyebox 126. The image in the corner domain may be directly observed by the user's eye 180 at the eyebox 126 of the display device 100.

In some embodiments, the grating 110 may be configured to focus portions 112 of light at least partially through corresponding polarization-tuning pixels 118. Referring to fig. 2 as an example, each grating 110 focuses a portion 112 of light coupled out by the grating to pass through a corresponding polarization-tuned LC pixel 118. For this, the grating 110 may be chirped in pitch. In some embodiments, microlenses 111 may be provided to aid in focusing, or to provide focusing of portions 112 of light in the XZ plane and YZ plane. Focusing may serve two purposes, firstly increasing the fraction of light propagating through the polarization-tuned LC pixel 118, and secondly increasing the divergence of the multiple fractions 112 of light at the polarization-tuned LC pixel 118, which allows increasing the size of the eyebox 126. Configuring the light source 104 to emit light 108 in a well-defined polarization state also helps to increase the throughput and photoelectric conversion efficiency of the display device 100. Furthermore, the light source 104 may be configured to emit light of a wavelength of a particular color channel to avoid or reduce optical losses due to spectral filtering of the LC cell 120. The light sources 104 may also be configured to emit light of wavelengths of other color channels in a time sequential manner to further improve the optical throughput and light utilization of the display device 100.

Turning to fig. 3, a display device 300 is similar to the display device 100 of fig. 1 and includes similar elements. The display device 300 of fig. 3 comprises an illuminator 102 having a light source 104, a transparent light guide 106 for diffusing light 108 emitted by the light source 104 in an XY plane, and a grating array 110 optically coupled to the transparent light guide 106 for coupling out portions 112 of the light 108 propagating in the transparent light guide 106. An LC layer 116 is disposed downstream of the illuminator 102. The LC layer 116 includes an array of polarization-tuned pixels 118 in a thin layer 116LC fluid between a first substrate 121 and a second substrate 122. A linear transmissive polarizer 328 is disposed downstream of LC cell 120.

The display device 300 of fig. 3 also includes a reflective offset-to-angle element 330 configured to redirect portions 112 of light propagating through the LC layer 116 back through the transparent light guide 106 (i.e., right to left in fig. 3) to form an image in the angular domain at the eyebox 326 on the side of the transparent light guide 106 opposite the reflective offset-to-angle element 330. In other words, the eyebox 326 and the offset-to-angle element 330 are disposed on opposite sides of the transparent light guide 106. The portions 112 of light again propagate on their way through the linear transmissive polarizer 328, LC cell 120, and through the transparent light guide 106. Any subsequent polarization change imparted by LC cell 120 will not matter upon the second propagation of portions 112 of light through LC cell 120 (i.e., right to left), because there is no polarizer downstream of LC cell 120 in the backward path of portions 112 of light, and therefore the image in the angular domain formed by reflection off-set to angle element 330 at eyebox 326 is not substantially distorted. It is noted that throughout the specification, the term "downstream" when referring to an optical path means that the beam(s) propagating along the optical path impinges on downstream elements after it impinges on them, irrespective of the geometrical arrangement of these elements, since the propagation direction may change with the propagation of light. According to this definition, the eyebox 326 is always disposed downstream of the reflective offset to angle element 330, even though the eyebox is disposed to the left of the transparent light guide 106 and to the left of the reflective offset to angle element 330 in fig. 3.

Referring to fig. 4, a display device 400 is an embodiment of the display device 300 of fig. 3. Similar to the display device 300 of fig. 3, the display device 400 of fig. 4 comprises an illuminator 102 having a light source 104, a transparent light guide 106 for diffusing illumination light in an XY plane, and a grating array for coupling out portions 112 of the light. An LC layer 116 is disposed downstream of the illuminator 102. A linear transmissive polarizer 328 is disposed downstream of LC cell 120.

The reflective offset to angle element 430 of the display device 400 comprises a first part 431 in the form of a meniscus lens having a reflective polarizer 436 on one surface and a Quarter Wave Plate (QWP) coating 438 on the other opposite surface, and a second part 432 in the form of a meniscus lens downstream of the first part 431 and comprising a reflector layer 440 on its outer convex surface. The function of the reflective offset-to-angle element 430 is to reflect portions 112 of light back through the LC layer 116 and the transparent illuminator 102 to form an image in the angular domain at the eyebox 426 for direct viewing by the user's eye 480.

The optical path of the portions 112 of light of the display device 400 that are offset into the angle element 430 will now be described with reference to the optical polarization diagram of fig. 4B and the schematic cross-sectional view of the display device 400 in fig. 4A. Portions 112 of the coupled-out light propagate through LC layer 116 and linear transmissive polarizer 328. The linear transmissive polarizer imparts a first linear polarization state to the plurality of portions 112 of light. Portions 112 of the light propagate through reflective polarizer 436 that is oriented to pass light of a first linear polarization state. The portions 112 of light then propagate through the QWP coating 438, are reflected by the reflector layer 440, and propagate back through the QWP coating 438, at which point the polarization state of the portions 112 of light is changed to a second, orthogonal linear polarization state, such that the portions of light reflected by the reflective polarizer 436 again propagate through the QWP coating 438 to the reflector layer 440 and are reflected by the reflector layer 440. After the fourth pass through the QWP coating 438, the portions 112 of the light are converted back to the first polarization state, so that the portions 112 of the light propagate back through the reflective polarizer 436, the linear transmissive polarizer 328, the LC layer 116 and the transparent illuminator 102 to form an image in the angular domain at the eyebox 426. As portions 112 of light propagate back through LC layer 116, they may change their polarization, but this is not important because there is no polarizer between LC layer 116 and eyebox 426.

In the illustrated embodiment, the reflector layer 440 is a partial reflector, such as a 50/50 mirror, which makes the entire assembly translucent, i.e., transparent to the external light 414. An eye tracking camera 442 (fig. 4A) may be disposed behind the reflector layer 440 for capturing an image of the user's eye 480 at the eyebox 426 through the offset to angle element 430, LC layer 116, and illuminator 102. In other embodiments, the eye tracking camera 442 is disposed elsewhere and the reflector layer 440 is a total reflector, which increases the throughput of the offset-to-angle element 430 by approximately two times.

The illuminator 102 may be configured in a variety of ways. Referring to fig. 5A and 5B as a non-limiting example, the illuminator 502 includes a light source 504 optically coupled to a first plate light guide 541 optically coupled to a second plate light guide 542. The first and second plate light guides 541 and 542 are made of a transparent material, and may be transparent to external light. The first plate light guide 541 and the second plate light guide 542 spread the light 508 emitted by the light source 504 in the XY plane by a series of consecutive reflections of the light 508 from the outer parallel surfaces of the transparent plate substrate. Specifically, the first and second plate light guides 541 and 542 spread the light 508 in the Y and X directions, respectively, by propagating the light 508 in a zigzag pattern by a series of consecutive total internal reflections from the opposing parallel surfaces of the first and second plate light guides 541 and 542. The first plate light guide 541 receives the light 508 from the light source 504 and generates a Y expanded beam 525 from portions of the light 508 coupled out by a grating coupler (not shown for simplicity). The Y expanded beam 525 is coupled into a second plate light guide 542 along an edge 527 parallel to the Y axis. The Y expanded beam 525 is then expanded along the X-axis by a second plate light guide 542, wherein portions 512 of the light propagate through the grating 510 and are partially coupled out by the grating 510, the grating 510 being optically coupled into the second plate light guide 542 and supported by the second plate light guide 542. The first plate light guide 541 and the second plate light guide 542 together spread the light 508 along an XY plane, which is parallel to the plane of the LC layer 116 (fig. 1). Portions 512 (fig. 5A) of the coupled-out light propagate through LC layer 116 (fig. 1). The second plate light guide 542 remains transparent to the external light 514.

Referring to fig. 6, illuminator 602 is another example embodiment of illuminator 102 of fig. 1. The illuminator 602 of fig. 6 includes a light source 604 coupled to a transparent flat light guide 606. The transparent slab light guide 606 supports a first grating 610, the first grating 610 being configured to couple out portions of light propagating through respective polarization-tuned pixels of the LC layer. The transparent flat light guide 606 (fig. 6) further comprises a second grating 611, the second grating 611 being configured to redirect the light 608 to propagate within the transparent flat light guide 606 so as to spread the light 608 in the XY plane by propagating the light 608 in a zigzag pattern by a series of consecutive total internal reflections from the opposite parallel surfaces of the transparent flat light guide 606. Light 608 spreads out in the XY plane, i.e., propagates in the XY plane, by a series of total internal reflections from the outer parallel surfaces of the transparent flat plate light guide 606.

Turning to fig. 7, the illuminator 702 includes a light source 704 for providing a light beam 708 to a transparent light guide 706. The transparent light guide 706 includes a Photonic Integrated Circuit (PIC) supported by a substrate 707. The PIC includes an array of linear waveguides 742 extending parallel to each other and an optical scheduling circuit 741 coupled to the light source 704. The optical scheduling circuit 741 is based on linear waveguides and is configured to receive the beam 708 and split it into a plurality of sub-beams for propagation in the respective linear waveguides 742. The term "linear waveguide" herein refers to a waveguide that limits light propagation in two dimensions, just like light rays. The linear waveguide may be straight, curved, etc.; in other words, the term "linear" does not refer to a straight waveguide segment. One example of a linear waveguide is a ridge waveguide.

To split the beam 708 into multiple sub-beams, the optical scheduling circuit 741 may include a binary tree of 1 x 2 waveguide splitters 744 coupled to each other by linear waveguides 745 supported by the substrate 707. Other configurations of optical scheduling circuits 741 are also possible, for example, these optical scheduling circuits may be based on a tree of Mach-Zehnder interferometers (Mach-Zehnder interferometer) and may include separate waveguide trees for the light source components of different wavelengths (e.g., wavelengths of different color channels).

The linear waveguides 742 extend parallel to each other along the polarization-tuned pixels 118 (fig. 1) to propagate sub-beams (fig. 7) in the linear waveguides 742. The transparent light guide 706 also includes an array of out-coupling gratings 710 optically coupled to the linear waveguide 742 for coupling out portions of the sub-beams propagating in the linear waveguide 742. The out-coupling grating 710 is shown disposed parallel to the XY plane and performs the same or similar function as the out-coupling grating 110 of the light guide 106 of the illuminator 102 of fig. 1. Specifically, the out-coupling grating 710 couples out portions of the sub-beams from the respective linear waveguides 742 such that the portions of the sub-beams propagate through the respective polarization-tuned pixels 118 of the LC layer 116.

Referring now to fig. 8, a Virtual Reality (VR) near-eye display 800 includes a frame 801 that supports for each eye: a luminaire 802, including any of the luminaires disclosed herein; an LC cell 820 comprising an array of polarization-tuned pixels, wherein the position of the out-coupling grating in the illuminator 802 is coordinated with the position of the polarization-tuned pixels of the LC cell 820; the reflective offset to angle element 830 is used to convert an image in the linear domain generated by LC cell 820 into an image in the angular domain with eyebox 826. The reflective offset to angle element 830 includes a semi-transparent mirror similar to the reflective offset to angle element 430 of fig. 4A, which enables the eye tracking camera 842 to be disposed directly behind the reflective offset to angle element 830, i.e., farther from the eyebox 826 than the reflective offset to angle element 830. A plurality of illuminators 862 (shown as black dots) may be disposed on a side of illuminator 802 facing eyebox 826.

The purpose of the eye tracking camera 842 is to determine the position and/or orientation of the user's two eyes. Illuminator 862 illuminates the eye at a respective eyebox 826, allowing eye tracking camera 842 to obtain an image of the eye, and provide reference reflection, i.e., glints. Flicker may be used as a reference point in the captured eye image to facilitate the determination of the eye gaze direction by determining the position of the eye pupil image relative to the flicker image. To avoid light from the illuminator 862 from being distracting to the user, the illuminator 862 may be caused to emit light that is not visible to the user. For example, infrared light may be used to illuminate the eyebox 826.

Turning to fig. 9, hmd 900 is an example of an AR/VR wearable display system that encloses a user's face in order to more immerse the user in an AR/VR environment. HMD 900 may generate a fully virtual 3D image. HMD 900 may include a front body 902 and a strap 904 that may be secured around the head of a user. The front body 902 is configured for placement in front of the eyes of a user in a reliable and comfortable manner. A display system 980 may be disposed in the front body 902 for presenting AR/VR images to a user. The display system 980 may include any of the display devices and illuminators disclosed herein. The side 906 of the front body 902 may be opaque or transparent.

In some embodiments, the front body 902 includes a locator 908 and an inertial measurement unit (inertial measurement unit, IMU) 910 for tracking acceleration of the HMD 900, and a position sensor 912 for tracking a position of the HMD 900. The IMU 910 is an electronic device that generates data indicative of the position of the HMD 900 based on measurement signals received from one or more position sensors 912 that generate one or more measurement signals in response to movement of the HMD 900. Examples of position sensors 912 include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, other suitable types of sensors that detect motion, a type of sensor for error correction of the IMU 910, or some combination thereof. The position sensor 912 may be located external to the IMU 910, internal to the IMU 910, or some combination thereof.

The localizer 908 is tracked by an external imaging device of the virtual reality system so that the virtual reality system can track the position and orientation of the entire HMD 900. The information generated by the IMU 910 and the position sensor 912 may be compared to the position and orientation obtained by the tracking locator 908 to improve the tracking accuracy of the position and orientation of the HMD 900. As the user moves and rotates in 3D space, the exact position and orientation is important for presenting the user with the proper virtual scene.

The HMD 900 may also include a depth camera assembly (depth camera assembly, DCA) 911 that captures data describing depth information for some or all of the local areas surrounding the HMD 900. The depth information may be compared to information from IMU 910 to more accurately determine the position and orientation of HMD 900 in 3D space.

HMD 900 may also include an eye tracking system 914 for determining the orientation and position of a user's eyes in real-time. The obtained position and orientation of the eyes also allows the HMD 900 to determine the gaze direction of the user and adjust the image generated by the display system 980 accordingly. The determined gaze direction and convergence angle may be used to adjust the display system 980 to reduce convergence adjustment conflicts. As disclosed herein, direction and convergence may also be used for exit pupil steering of a display. Further, the determined vergence angle and gaze angle may be used to interact with a user, highlight an object, bring an object to the foreground, create additional objects or pointers, and so forth. An audio system may also be provided that includes, for example, a set of small speakers built into the front body 902.

Embodiments of the present disclosure may include or be implemented in conjunction with an artificial reality system. The artificial reality system adjusts sensory information about the outside world (e.g., visual information, audio, touch (somatosensory) information, acceleration, balance, etc.) obtained through sensory in some way before presenting to the user. As non-limiting examples, the artificial reality may include Virtual Reality (VR), augmented reality (augmented reality, AR), mixed Reality (MR), mixed reality (hybrid reality), or some combination and/or derivative thereof. The artificial reality content may include entirely generated content or generated content in combination with captured (e.g., real world) content. The artificial reality content may include video, audio, physical or tactile feedback, or some combination thereof. Any of these content may be presented in a single channel or multiple channels (e.g., in stereoscopic video that produces a three-dimensional effect to the viewer). Further, in some embodiments, the artificial reality may also be associated with an application, product, accessory, service, or some combination thereof, for creating content in the artificial reality and/or otherwise for the artificial reality (e.g., performing an activity in the artificial reality), for example. The artificial reality system providing artificial reality content may be implemented on a variety of platforms including wearable systems, such as an HMD connected to a host computer system, a standalone HMD, a near-eye display with a form factor of glasses, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers.

The scope of the present disclosure is not limited by the specific embodiments described herein. Indeed, various other embodiments and modifications in addition to those described herein will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Accordingly, such other embodiments and modifications are intended to fall within the scope of this disclosure. Furthermore, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims should be interpreted in light of the full breadth of the disclosure described herein.

Claims (15)

1. A display device, the display device comprising:

a luminaire comprising a light source, a transparent light guide for diffusing light emitted by the light source along a plane parallel to the transparent light guide, and a grating array optically coupled to the transparent light guide for coupling out portions of the light propagating in the transparent light guide; and

A Liquid Crystal (LC) layer downstream of the illuminator, the LC layer comprising an array of polarization-tuned pixels, wherein the position of the grating is coordinated with the position of the polarization-tuned pixels such that portions of the light coupled out of the transparent light guide by the grating propagate through the corresponding polarization-tuned pixels.

2. The display device of claim 1, wherein the grating is configured to at least partially focus portions of the light through the corresponding polarization-tuned pixels; and/or

Wherein the light source is configured to emit light of a first polarization state, wherein the transparent light guide substantially retains the first polarization state of the light emitted by the light source.

3. The display device of claim 1, wherein the light source is configured to emit light of a wavelength of a first color channel; and is also provided with

Optionally, wherein the light source is configured to emit light of a wavelength of a second color channel and light of a wavelength of a third color channel, wherein, in operation, the light of the first color channel, the light of the second color channel, and the light of the third color channel are emitted in a time sequential manner.

4. The display device of claim 1, further comprising at least one of:

a grid layer adjacent to the LC layer for defining boundaries of polarization tuning pixels of the polarization tuning pixel array; or alternatively

A substrate adjacent to the LC layer, the substrate comprising an array of transparent electrode segments defining the polarization-tuned pixel array; and/or

The display device further comprises a polarizer downstream of the LC layer for transmitting light of a first polarization state and rejecting light of a second, orthogonal polarization state.

5. The display device of claim 1, the display device further comprising:

an eyebox located downstream of the LC layer; and

an offset-to-angle element in the optical path between the LC layer and the eyebox for converting an image of the LC layer in the linear domain to an image of the eyebox in the angular domain;

wherein the offset-to-angle elements are configured to redirect portions of the light propagating through the LC layer back through the transparent light guide to form an image in an angular domain, wherein the eyebox and the offset-to-angle elements are disposed on opposite sides of the transparent light guide.

6. The display device of claim 5, wherein the offset to angle element comprises:

a first component comprising a reflective polarizer; and

a second component downstream of the first component, the second component comprising a reflector layer;

wherein, in operation, portions of the coupled-out light propagate through the reflective polarizer, are reflected by the reflector layer, propagate back to the reflective polarizer and are reflected thereby, propagate again to the reflector layer and are reflected thereby, propagate back through the transparent light guide, and form an image in the angular domain at the eyebox.

7. The display device of claim 6, wherein the reflector layer comprises a total reflector; or alternatively

Wherein the reflector layer comprises a partial reflector, the display device further comprising an eye tracking camera located behind the partial reflector for capturing an image of the user's eye at the eyebox through the offset-to-angle element.

8. The display device of claim 1, wherein the transparent light guide comprises a flat sheet of transparent material for propagating light in the flat sheet in a zigzag pattern by a series of successive total internal reflections from opposite parallel surfaces of the flat sheet, wherein the grating array is supported by the flat sheet.

9. The display device of claim 1, wherein the transparent light guide comprises:

a substrate;

a scheduling circuit supported by the substrate; and

a linear waveguide array supported by the substrate and extending along polarization tuning pixels of the polarization tuning pixel array;

wherein the scheduling circuit is configured to receive light from the light source and split the light between a plurality of linear waveguides; and is also provided with

Wherein the grating is optically coupled to the plurality of linear waveguides for coupling out portions of the light from the plurality of linear waveguides to propagate through corresponding polarization tuning pixels of the polarization tuning pixel array.

10. A display device, the display device comprising:

an illuminator comprising a light source, a flat sheet of transparent material coupled to the light source for propagating light in the flat sheet in a zigzag pattern by a series of successive total internal reflections from opposite parallel surfaces of the flat sheet, and a grating array supported by the flat sheet for coupling out portions of the light propagating in the flat sheet; and

A Liquid Crystal (LC) layer optically coupled to the illuminator, the LC layer comprising an array of polarization-tuned pixels, wherein the position of the grating is coordinated with the position of the polarization-tuned pixels such that portions of the light coupled out of the slab of transparent material by the grating propagate through the corresponding polarization-tuned pixels.

11. The display device of claim 10, the display device further comprising:

an eyebox located downstream of the LC layer; and

a reflective offset-to-angle element in the optical path between the LC layer and the eyebox for converting an image of the LC layer in the linear domain to an image of the eyebox in the angular domain;

wherein the reflective offset-to-angle element is configured to redirect portions of the light propagating through the LC layer back through the flat sheet of transparent material to form an image in an angular domain, wherein the eyebox and the offset-to-angle element are disposed on opposite sides of the flat sheet of transparent material.

12. The display device of claim 11, wherein the reflective offset to angle element comprises:

A first component comprising a reflective polarizer; and

a second component downstream of the first component, the second component comprising a reflector layer;

wherein, in operation, portions of the coupled-out light propagate through the reflective polarizer, are reflected by the reflector layer, propagate back to the reflective polarizer and are reflected thereby, propagate again to the reflector layer and are reflected thereby, propagate back through the slab of transparent material, and form an image in the angular domain at the eyebox.

13. A display device, the display device comprising:

a luminaire comprising a light source and a transparent light guide comprising a substrate, a scheduling circuit supported by the substrate, a linear waveguide array supported by the substrate, and a grating array optically coupled to the linear waveguide array, wherein the scheduling circuit is configured to receive light from the light source and split light emitted by the light source between a plurality of linear waveguides, and wherein the grating is configured to couple out portions of light from the plurality of linear waveguides; and

A Liquid Crystal (LC) layer optically coupled to the illuminator, the LC layer comprising an array of polarization-tuned pixels, wherein the linear waveguide extends along the polarization-tuned pixels of the LC layer;

wherein the position of the grating is coordinated with the position of the polarization tuning pixel such that portions of the light beam coupled out of the linear waveguide by the grating propagate through the corresponding polarization tuning pixel.

14. The display device of claim 13, the display device further comprising:

an eyebox located downstream of the LC layer; and

a reflective offset-to-angle element in the optical path between the LC layer and the eyebox for converting an image of the LC layer in the linear domain to an image of the eyebox in the angular domain;

wherein the reflective offset-to-angle element is configured to redirect portions of light propagating through the LC layer back through the transparent light guide to form an image in an angular domain, wherein the eyebox and the offset-to-angle element are disposed on opposite sides of the transparent light guide.

15. The display device of claim 14, wherein the reflective offset to angle element comprises:

A first component comprising a reflective polarizer; and

a second component downstream of the first component, the second component comprising a reflector layer;

wherein, in operation, portions of the out-coupled light propagate through the reflective polarizer, are reflected by the reflector layer, propagate back to the reflective polarizer and are reflected thereby, propagate again to the reflector layer and are reflected thereby, propagate back through the transparent light guide, and form an image in the angular domain at the eyebox.