CN118043589A - Geometric waveguide illuminator and display based on same - Google Patents

Abstract

A luminaire for illuminating a display panel, the luminaire comprising a light guide having an array of embedded tilted-body reflectors that couple out a portion of a light beam propagating in the light guide through one of the light guide surfaces. A polarizing beam-splitting inclined surface may be used to provide a polarized output. Such an illuminator may be used with reflective display panels operated by polarization. These beam-splitting inclined surfaces operate as polarizers to provide polarized illumination light. Light reflected by the reflective panel may propagate back through the illuminator and the polarizing beam-splitting inclined surfaces may also operate as analyzers.

Description

Geometric waveguide illuminator and display based on same

Technical Field

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

Background

Visual displays provide information to one or more viewers, including still images, video, data, and the like. Visual displays find application in a variety of 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 (NED-EYE DISPLAY, NED)) are intended for use by a single user.

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 or combine images of real objects with images of virtual objects, 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., 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 external light, but includes some light routing optics to direct the display light into the field of view of the user.

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. Head mounted display devices may benefit from compact and efficient components. In particular, head mounted display devices that use reflective or transmissive display panels to generate images to be displayed to a wearer may benefit from compact and efficient light sources and illuminators for illuminating the display panels.

Disclosure of Invention

According to a first aspect of the present disclosure, there is provided a luminaire for a display panel, the luminaire comprising: a light guide for propagating a light beam along a length dimension of the light guide by a series of internal reflections from opposing first and second outer surfaces of the light guide, wherein the first and second surfaces are separated by a light guide thickness dimension perpendicular to the length dimension; and a first plurality of angled portion bulk reflectors inside the light guide for coupling out portions of the light beam through the first surface along the length dimension of the light guide, the coupled out light beam portions forming an output light beam for illuminating the display panel.

In some embodiments, the tilted-section reflectors of the first plurality of tilted-section bulk reflectors may comprise polarization-selective reflectors for reflecting light of a first polarization and transmitting light of a second orthogonal polarization.

In some embodiments, the illuminator may further comprise a linear transmissive polarizer disposed near the second surface of the light guide and configured to transmit light of the second polarization.

In some embodiments, the angled partial volume reflectors may extend from the first surface to the second surface of the light guide.

In some embodiments, the illuminator may further comprise a diffuser located upstream of the light guide, the diffuser for scattering the light beam within a predefined light cone.

In some embodiments, the apex angle of the cone of light may be less than 4 degrees.

In some embodiments, the luminaire further comprises a partial reflector embedded in the light guide and disposed in the light path upstream of the first plurality of tilted partial-body reflectors, at a distance from and parallel to the first and second opposing outer surfaces, for separating the light beam, thereby increasing the spatial density of the portion of the light beam coupled out of the light guide by the first plurality of tilted partial-body reflectors.

In some embodiments, the illuminator may further comprise a second plurality of tilted partial-body reflectors disposed inside the light guide upstream of the first plurality of tilted partial-body reflectors for expanding the light beam along a width dimension of the light guide to obtain an expanded light beam and for directing the expanded light beam toward the first plurality of tilted partial-body reflectors.

In some embodiments, the illuminator may further comprise a tiltable reflector located in the optical path upstream of the light guide, the tiltable reflector for changing an angle of incidence of the light beam onto the light guide.

In some embodiments, there is at least one of the following: the lightguide thickness may be less than 0.5mm; the width of the tilted partial volume reflector of the first plurality of tilted partial volume reflectors located between the opposing first outer surface and the second outer surface of the light guide may be less than 0.7mm; or at least some of the first plurality of tilted partial-body reflectors may have a reflectivity greater than 50%.

In some embodiments, the tilted partial-body reflectors of the first plurality of tilted partial-body reflectors may be parallel to each other within 0.5 degrees, and wherein at least some of the tilted partial-body reflectors of the first plurality of tilted partial-body reflectors are at an angle of at least 0.2 degrees relative to each other.

According to another aspect of the present disclosure, there is provided a display device including: a display panel including a substrate and a pixel array supported by the substrate; and a light guide for illuminating the pixel array of the display panel, the light guide comprising opposed first and second outer surfaces for guiding a light beam in the light guide, and a plurality of tilted partial volume reflectors extending between the first and second surfaces at an acute angle to the first and second surfaces for reflecting portions of the light beam out of the light guide for illumination onto the pixel array of the display panel.

In some embodiments, the display device may further include an ophthalmic lens (oculars) downstream of the array of pixels, wherein the ophthalmic lens is configured to convert an image in a spatial domain displayed by the display panel into an image in an angular domain downstream of the ophthalmic lens for viewing by a user's eye downstream of the ophthalmic lens.

In some embodiments, the pixel array may be a reflective pixel array; and the light guide is disposed between the display panel and the ophthalmic lens; wherein, in operation, portions of the light beam reflected by the plurality of tilted partial-body reflectors impinge on the reflective pixel array, thereby being reflected, propagate back through the light guide, and impinge on the ophthalmic lens.

In some embodiments, the reflective pixel array may be configured to controllably tune the polarization of the illuminating beam portion from a first polarization state to an orthogonal second polarization state; and the tilted reflectors are polarization selective and configured to reflect light of the first polarization state and transmit light of the second polarization state.

In some embodiments, the display device may further include a linear transmissive polarizer positioned between the light guide and the ophthalmic lens.

In some embodiments, the pixel array may include a transmissive pixel array; and the display panel is disposed between the light guide and the ophthalmic lens; wherein, in operation, the portion of the light beam reflected by the polarization selective plurality of tilted reflectors propagates through the substrate, through the transmissive pixel array, and impinges on the ophthalmic lens.

In some embodiments, the display device may further comprise a focusing element for forming an array of light spots from the out-coupled light portion downstream of the focusing element, such that in operation an array of light power density peaks is formed at the transmissive pixel array due to the tabot effect.

According to another aspect of the present disclosure, there is provided a method for illuminating a display panel, the method comprising: propagating a light beam in the light guide along a length dimension by a series of internal reflections from opposing first and second outer surfaces of the light guide; coupling out a portion of the light beam through the first surface along the length dimension of the light guide using a plurality of tilted partial volume reflectors inside the light guide; and forming an output beam from the coupled-out beam portion for illuminating the display panel.

In some embodiments, the display panel may be a reflective display panel, and the method further comprises: reflecting the output light beam through the reflective display panel; and propagating the output light beam reflected by the reflective display panel through the light guide.

It should be understood that any feature described herein as being suitable for incorporation into one or more aspects or one or more embodiments of the present disclosure is intended to be generalized to any and all aspects, and any and all embodiments of the present disclosure. Other aspects of the present disclosure will be appreciated by those skilled in the art from the specification, claims and drawings of the present disclosure. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims.

Drawings

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

FIG. 1 is a three-dimensional view of a luminaire of the present disclosure;

FIG. 2 is a schematic diagram of a display device of the present disclosure that uses the illuminator of FIG. 1 to provide light to a reflective display panel;

FIG. 3 is a partial cross-sectional view of an embodiment of the display device of FIG. 2, showing the light propagation paths of light of different polarization states;

Fig. 4A to 4D are schematic side views showing virtual optical paths in the display device of fig. 2 and 3;

FIGS. 5A and 5B are side cross-sectional views of the luminaire of the present disclosure without an upstream diffuser (FIG. 5A) and with an upstream diffuser (FIG. 5B);

FIG. 6A is a side cross-sectional view of an illuminator of the present disclosure having an embedded reflector for increasing pupil replication density;

FIG. 6B is a side cross-sectional view of an illuminator with an increased density of tilted mirrors of the present disclosure for increasing pupil replication density;

FIG. 6C is an enlarged plan view of the illuminator of FIG. 6B, showing the overlapping of tilted body reflectors in the light guide of the illuminator;

fig. 7A and 7B are side and plan views, respectively, of a luminaire of the present disclosure having two sets of tilted reflectors and a tiltable reflector at the input end;

FIG. 8 is an exploded side view of a display device using the illuminator of the present disclosure that provides illumination light to a transmissive display panel;

FIG. 9 is an enlarged cross-sectional view of an embodiment of the display device of FIG. 8 using the Talbot effect to illuminate a pixel array of a transmissive display panel with an array of illumination spots at a depth within the transmissive display panel;

FIG. 10 is a flow chart of a method of the present disclosure for illuminating a display panel;

FIG. 11 is a view of an Augmented Reality (AR) display of the present disclosure having a pair of eyeglass form factors; and

Fig. 12 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, it is intended that such equivalents 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" and "second," etc. are not intended to imply a sequential ordering, but rather to distinguish one element from another. Similarly, the sequential order of the method steps does not imply a sequential order of their execution unless explicitly stated. In fig. 1, 4A to 4D and 7A to 7B, like reference numerals denote like elements. Also in fig. 2, 3, 5A to 5B, 6A to 6C, and 8, like reference numerals denote like elements.

In accordance with the present disclosure, the geometric waveguide may be used to illuminate a display panel that includes an array of reflective pixels or transmissive pixels (e.g., an array of Liquid Crystals (LCs) of reflective pixels or transmissive pixels). The geometric waveguide may be made in the form of a thin plate or sheet of transparent material having opposite outer surfaces for guiding light in the slab by a series of zigzagged internal reflections from the outer surfaces of the slab. The flat panel includes a set of approximately parallel angled partial reflectors (i.e., semi-transparent body reflectors) that form an acute angle with the opposing outer surface. When light propagating in the plate impinges on the tilted partial reflector, a portion of the light is coupled out of the plate, forming a broad illumination beam. The requirements for parallelism of the illumination beam are relatively relaxed, resulting in a low production cost of the geometric waveguide illuminator. Such a luminaire is not color selective and is very compact. The term "geometric waveguide" is distinguished from pupil replicating waveguides that are equipped with diffraction grating-based couplers. The out-coupling mechanism in a geometric waveguide is reflective rather than diffractive and therefore not color selective, i.e. all wavelengths are out-coupled at the same angle.

According to the present disclosure, there is provided a luminaire for a display panel. The illuminator includes a light guide for propagating a light beam along a length dimension of the light guide by a series of internal reflections from opposing first and second outer surfaces of the light guide. The first surface and the second surface are separated by a light guide thickness dimension perpendicular to the length dimension. A first plurality of tilted partial-body reflectors is disposed inside the light guide, the first plurality of tilted partial-body reflectors being configured to couple portions of the light beam out through the first surface along the length dimension of the light guide. The coupled-out beam portions form an output beam for illuminating the display panel. The tilted-section reflectors of the first plurality of tilted-section bulk reflectors may comprise polarization-selective reflectors for reflecting light of a first polarization and transmitting light of a second orthogonal polarization. A linear transmissive polarizer may be disposed near the second surface of the light guide and configured to transmit light of the second polarization. The angled partial volume reflectors may extend from the first surface to the second surface of the light guide.

In some embodiments, a diffuser is disposed upstream of the light guide, the diffuser being for scattering the light beam within a predefined light cone. The apex angle of the light cone may be, for example, less than 4 degrees. A partial reflector may be embedded in the light guide and disposed in the light path upstream of the first plurality of tilted partial-body reflectors at a distance from and parallel to the first and second opposing outer surfaces, the partial reflector being configured to separate the light beam to increase the spatial density of the portion of the light beam coupled out of the light guide by the first plurality of tilted partial-body reflectors.

The luminaire may further comprise a second plurality of tilted partial-body reflectors arranged inside the light guide upstream of the first plurality of tilted partial-body reflectors for expanding the light beam along the width dimension of the light guide to obtain an expanded light beam and for directing the expanded light beam towards the first plurality of tilted partial-body reflectors. The illuminator may comprise a tiltable reflector in the optical path upstream of the light guide, the tiltable reflector for changing the angle of incidence of the light beam onto the light guide. The light guide may be very thin, for example less than 0.5mm. The width of the tilted partial body reflector of the first plurality of tilted partial body reflectors located between the opposing first outer surface and the second outer surface of the light guide may be less than 0.7mm. At least some of the first plurality of tilted partial-body reflectors may have a reflectivity greater than 50%. The tilted partial-body reflectors of the first plurality of tilted partial-body reflectors may be parallel to each other within 0.5 degrees. At least some of the first plurality of tilted partial-body reflectors may be at an angle of at least 0.2 degrees relative to each other.

According to the present disclosure, there is provided a display device including a display panel including a substrate and a pixel array supported by the substrate, and an illuminator as described above. The display device may comprise an ophthalmic lens downstream of the pixel array. The ophthalmic lens may be configured to convert an image in a spatial domain displayed by the display panel into an image in an angular domain downstream of the ophthalmic lens for viewing by a user's eye downstream of the ophthalmic lens.

In embodiments where the array of pixels is reflective, the light guide may be disposed between the display panel and the ophthalmic lens. In operation, portions of the light beam reflected by the plurality of tilted partial-body reflectors may impinge on the reflective pixel array, thereby being reflected, propagated back through the light guide, and impinge on the ophthalmic lens. The reflective pixel array may be configured to controllably tune the polarization of the illuminating beam portion from a first polarization state to an orthogonal second polarization state. In such embodiments, the tilted reflectors may be polarization selective, i.e., they may reflect light of a first polarization state and transmit light of a second polarization state. A linear transmissive polarizer may be disposed between the light guide and the ophthalmic lens.

In embodiments where the array of pixels is transmissive, the display panel may be disposed between the light guide and the ophthalmic lens. In operation, portions of the light beam reflected by the polarization selective plurality of tilted reflectors may propagate through the substrate, through the transmissive pixel array, and impinge on the ophthalmic lens. In some embodiments, the display device further comprises a focusing element for forming an array of light spots from the coupled-out light portion downstream of the focusing element, such that in operation an array of light power density peaks is formed at the transmissive pixel array due to the taber effect.

In accordance with the present disclosure, a method for illuminating a display panel is provided. The method includes propagating a light beam in the light guide along a length dimension by a series of internal reflections from opposing first and second outer surfaces of the light guide. Using a plurality of tilted partial volume reflectors inside the light guide, a portion of the light beam is coupled out through the first surface along a length dimension of the light guide, and an output light beam for illuminating the display panel is formed from the coupled-out light beam portion.

In embodiments where the display panel is reflective, the method may further comprise reflecting the output light beam through the reflective display panel and propagating the output light beam reflected by the reflective display panel through the light guide.

Referring now to fig. 1, illuminator 100 includes a light guide 102, light guide 102 having a plurality of internal reflectors 104, internal reflectors 104 being partial volume reflectors, or in other words, internal reflectors 104 being semi-transparent volume reflectors. The light guide 102 may be a flat plate or plate of, for example, a transparent material (e.g., glass, plastic, oxide, crystal, etc.). The light guide 102 has opposed first and second outer surfaces 111, 112 that are spaced from each other a distance equal to the light guide thickness 198. The light beam 115 may be directed within the light guide 102 by a series of internal reflections (e.g., total internal reflection) from the opposing first and second surfaces 111, 112. Reflection occurs from inside the light guide 102. As shown, the tilted partial volume reflector 104 may extend continuously from the first surface 111 to the second surface 112.

The luminaire 100 may also have a coupler 106, the coupler 106 comprising an inclined side surface 108 for receiving a light beam 115. The angle of reflection of beam portion 120 is equal to the angle of incidence of beam 115 onto internal reflector 104, according to the law of geometrical reflection. In many cases, the internal reflector 104 is a partial reflector of progressively increasing reflectivity to offset the progressively decreasing optical power and provide a uniform illumination beam. The reflectivity of some of the internal reflectors 104 may be in excess of 50%; the last (most downstream) reflector 104 may even be a total reflector with a reflectivity close to 100%. The internal reflectors 104 may be polarization-selective reflectors, i.e., they may be polarization-splitting (PBS) surfaces or interfaces. The PBS internal reflector can be used to illuminate a display panel that is operated by spatially variable polarization tuning of the illumination light. Such a display may include an array of individually controllable polarization tuning pixels.

Due to the angle-preserving properties of the light guide 102, the light guide 102 may be used to transfer images in the angular domain from the coupler 106 to an eyebox located below the first surface 111 in fig. 1. For imaging applications, output beam parallelism is critical to maintaining sharpness of the transmitted image, i.e., improving the modulation transfer function (modulation transfer function, MTF). In contrast, there is no need to maintain parallelism of the light beam 115 in lighting applications. The light guide 102 does not have to maintain the beam parallelism at a high level and can output an expanded beam at the parallel beam input. An expanded or divergent illumination beam may even be desirable in certain display configurations. Thus, the tolerance of the parallelism of the first surface 111 and the second surface 112 may be greatly relaxed to, for example, 0.1 degrees, 0.2 degrees, and even 0.5 degrees. Even when at least some of the first plurality of oblique-section body reflectors are at an angle of 0.2 degrees or more with respect to each other, no performance degradation is observed.

For the same reason, the light guide 102 can be made very thin without having to worry about the small diameter light beam 115 fitted in the light guide 102 becoming divergent due to diffraction. For example, the light guide 102 may be made thinner than 2mm, 1mm, or in some cases even thinner than 0.5mm. Thus, the width of the angled portion of the body reflector 104 between the opposing first and second outer surfaces 111, 112 of the light guide may be less than about 2.8mm, 1.4mm, or even 0.7mm. The width dimension is shown at 199 in fig. 1.

Thin light guides with loose geometric tolerances of the tilted reflectors and the outer surfaces may be much less expensive to manufacture. Such a light guide may be used as a front light or backlight for a micro display panel or, in some applications, for a relatively large display panel. More generally, illuminator 100 can be used in illumination applications that require a broad illumination beam emitted by a low-profile, high-efficiency illumination source.

The use of the luminaire 100 in a display system will now be described by way of a non-limiting illustrative example. Referring to fig. 2, the illuminator 100 is used in a display device 200. The display device 200 uses a reflective display panel 224 and an ophthalmic lens 216, the reflective display panel 224 having a reflective pixel array 214 supported by a substrate 215. The reflective display panel 224 and the ophthalmic lens 216 are disposed on opposite sides of the illuminator 100. Ophthalmic lens 216 may include wafer lenses, multi-element refractive lenses, combinations of refractive and reflective elements, and the like.

In operation, light source 210 emits light beam 115. The light beam 115 may be coupled into the luminaire 100 via the slanted coupling-in surface 108. Other coupling-in configurations are also possible, for example coupling-in configurations using diffraction gratings. The coupled-in light beam 115 propagates down the light guide 102 (along the Y-axis in fig. 2) by a series of total internal reflections from the opposite outer surfaces 111 and 112 of the light guide. The partially tilted body reflector 104 initially couples out a portion 120 of the light beam 115 toward the reflective pixel array 214. Portion 120 is reflected by reflective pixel array 214 to propagate through light guide 102 toward ophthalmic lens 216. The ophthalmic lens 216 forms a generally converging light beam 217 at an eye-ward region 236 of the display device 200.

The ophthalmic lens 216 is configured to convert an image in the linear domain displayed by the display panel into an image in the angular domain at the eyebox 236 downstream of the ophthalmic lens 216 for viewing by the user's eye 234. The term "image in the spatial domain" refers to an image as follows: the pixel coordinates of the image being displayed correspond to the XY coordinates of the display pixels. The term "image in the angular domain" refers to an image as follows: the pixel coordinates of the image being displayed correspond to the ray angles of the converging image light at the eyebox. A transmissive configuration of a display device having the illuminator of the present disclosure is also possible and will be considered further below.

In some embodiments, reflective pixel array 214 includes a reflective liquid crystal pixel array, such as a liquid crystal on silicon (LC) (liquid crystal on silicon, LCoS) array, having a polarization tuning pixel array, such as a polarization rotator capable of controllably tuning the polarization of the illuminating light or a retarder-tunable waveplate. The optical retardation changes when LC molecules are redirected in an electric field applied to the LC layer through a set of electrodes. In the embodiment shown in fig. 2, the partial reflector 104 is a polarization-selective reflector that reflects light of a first polarization state and transmits light of a second orthogonal polarization state.

Fig. 3 shows the polarization performance of the display device 200. The light beam 115 propagates along the light guide 102. The beam portion 120 is linearly polarized along the X-axis, i.e., perpendicular to the plane of fig. 3. The polarization-selective reflector 104 operates as a polarizer to polarize the illumination light. The pixels of the reflective pixel array 214 tune the polarization of the illuminated beam portion 120 to form a spatial distribution of the polarization of the reflected light according to the image to be displayed by the display device 200. Reflected light polarized linearly along the Y-axis propagates through the polarization-selective reflector 104 and impinges on the ophthalmic lens 216. Polarization-selective reflector 104 now operates as a compound analyzer of reflected beam portion 120, forming an image in the linear domain (i.e., linear space) that is converted by ophthalmic lens 216 into an image in the angular domain (i.e., angular space) for viewing by a user's eye 234 at an eyebox 236 (fig. 2). An auxiliary polarizer 250, such as a linear transmissive polarizer, may be disposed downstream of the light guide 102.

The function of the auxiliary polarizer 250 will now be explained. Fig. 4A-4D illustrate several possible optical paths for the reflected beam portion 120. Fig. 4A shows the correct imaging optical path in which beam portion 120 is reflected by partial reflector 104 to impinge on reflective pixel array 214 to be reflected as a function of the polarization state of the image brightness value assigned to the reflective pixel and propagate toward the ophthalmic lens (not shown). Fig. 4B shows that for a first imaginary path of the reflected beam portion 120, the reflected beam portion 120 experiences a secondary reflection from the partial reflector 104 when reflected from the reflective pixel array 214. Fig. 4C and 4D show two further virtual paths. Of the three virtual paths of fig. 4B, 4C, and 4D, only the virtual path of fig. 4B has the same beam angle as that in the main path shown in fig. 4A. Thus, the beam path may create a ghost image at the eyebox 236 (fig. 2). The other two beam paths are reflected off and typically do not contribute to the formation of ghost images.

It should be noted that the light on the virtual beam path of fig. 4B has a polarization that is orthogonal to the polarization of the path of fig. 4A. Therefore, the auxiliary polarizer 250 will block the virtual path, thereby effectively suppressing the formation of ghost images. For this purpose, an auxiliary polarizer 250 needs to be placed downstream of the illuminator 100, i.e., the illuminator 100 needs to be disposed between the reflective pixel array 214 and the auxiliary polarizer 250. In some embodiments, auxiliary polarizer 250 may be placed downstream of ophthalmic lens 216. The second function of auxiliary polarizer 250 is to operate as an analyzer for converting the polarization distribution imparted to beam portion 120 by reflective pixel array 214 into a luminance/optical power density distribution. In other words, auxiliary polarizer 250 shares analyzer functionality with partial reflector 104.

Referring back again to fig. 2, when beam portion 120 forms a parallel output beam, the parallel output beam is focused by ophthalmic lens 216 into a reduced spot centered on the pupil of user's eye 234. However, shrinking the spot or small-sized exit pupil of the display device 200 may present viewers with problems including: resolution reduction, pupil wander, unnatural appearance of smooth white portions of the image to be displayed, mosquito conditions (eye floater), and the like. Thus, it is desirable to avoid collimated illumination beams; instead, the display panel 224 may be illuminated with a light beam having a particular non-zero divergence. This may be achieved, for example, by placing a negative lens between the light source 210 and the coupler 106. The negative lens will produce a diverging beam at the input end, which will also diverge at the output end. However, such a solution may create problems related to non-uniform fields of view and speckle, for example, when the light source 210 is a coherent light source. These and other problems may be associated with low etendue (etendue) of an illumination beam. The etendue is not increased by inserting a lens into the optical path.

Fig. 5A shows the formation of a parallel output beam from a parallel input beam by illuminator 100. The display device 500A of fig. 5A is similar to the display device 200 of fig. 2 and 3 and includes similar elements. The light source 510 provides a collimated light beam 515, the collimated light beam 515 being coupled into the light guide 102 of the luminaire 100. The collimated light beam 515 propagates in the light guide 102 by a series of internal reflections. The tilted-section bulk reflector 104 couples out portions 525 and 526 of the collimated light beam 515 toward the reflective display panel 224, and the reflective display panel 224 reflects portions 525 and 526 of the collimated light beam to propagate through the light guide 102 and the auxiliary polarizer 250 as explained above. For clarity of illustration, only two beam portions 525 and 526 are shown.

Referring now to fig. 5B and with further reference to fig. 5A, a display device 500B is similar to display device 500A of fig. 5A and includes similar elements. The display device 500B of fig. 5B also includes a diffuser 550 located upstream of the light guide 102. The diffuser 550 may be mounted to the coupler 106. The diffuser 550 may be an engineered diffuser that scatters the light beam 515 within a predefined cone of light, such as a cone of light having an apex of no more than 4 degrees. Since beam 515 is expanding, the out-coupled portions 525 and 526 will also expand as shown. Diffuser 550 increases the etendue of coupled-out beam portions 525 and 526, resulting in larger exit pupil size, reduced field-of-view non-uniformity, and reduced speckle pattern formation.

To improve the spatial uniformity of the illumination beam, the light guide of the display panel illuminator may comprise additional beam splitters and/or partial reflectors. Turning to the non-limiting illustrative example of fig. 6A, display device 600A is similar to display device 500A of fig. 5A and includes similar elements. The display device 600A of fig. 6A further comprises a partial reflector 650, e.g. a half mirror, a dielectric coating, etc., embedded in the light guide 102, or in other words arranged within the light guide 102. A partial reflector 650 (shown as a thick dashed line) is disposed in the optical path upstream of the plurality of tilted partial body reflectors 104 at a distance from and parallel to the opposing first and second outer surfaces 111, 112. In some embodiments, the partial reflector 650 is equidistant from the first outer surface 111 and the second outer surface 112. The partial reflector 650 may also be disposed at a smaller distance from one of the first and second outer surfaces 111 and 112 than the other of the first and second outer surfaces 111 and 112.

In operation, partial reflector 650 splits light beam 515 into a plurality of sub-beams. The net result is an increase in the number of beam portions that are coupled out, which results in an increase in the spatial density of the beam portions that are coupled out. In fig. 6A, three beam portions 625, 626, 627 are coupled out of the light guide 102 by a plurality of angled portion bulk reflectors 104. Although only three portions are shown, more overlapping beam portions may be coupled out to form a continuous wide and uniform illumination beam.

Referring now to fig. 6B, a display device 600B is similar to display device 500A of fig. 5A and includes similar elements. The display device 600B of fig. 6B has a light guide 602 similar to the light guide 102 of fig. 1-3, 5A, 5B and the light guide 102 of fig. 6A in that the light guide 602 includes a plurality of angled partial volume reflectors 104 inside the light guide 602. The light guide 602 of fig. 6B differs in that in the light guide 602 the density of the inclined partial volume reflectors 104 is sufficiently high that the projections on the first outer surface 611 and the second outer surface 612 of the light guide 602 overlap each other. This is shown in more detail in fig. 6C, where orthogonal projections of adjacent tilted partial-body reflectors 604-1 and 604-2 onto the first surface 611 (parallel to the XY plane and the plane of fig. 6C) overlap each other, thereby forming an overlap region 662.

In some embodiments of an illuminator based on a geometric waveguide of the present disclosure, the waveguide may include two sets of angled partial volume reflectors for expanding the light beam in two perpendicular directions. Referring to the non-limiting illustrative example of fig. 7A and 7B, illuminator 700 includes a light guide 702, and light guide 702 may propagate light beam 715 emitted by light source 710 through a series of internal reflections from first and second outer surfaces 711 and 712 of light guide 702 along a length dimension of light guide 702 (i.e., along the Y-axis in fig. 7A and 7B) and along a width dimension (i.e., along the X-axis in fig. 7A and 7B), first and second outer surfaces 711 and 712 being separated by a light guide thickness measured along the Z-axis in fig. 7A and 7B.

The illuminator 700 includes two sets of multiple tilted partial volume reflectors inside the light guide 702: the first plurality of tilted partial-body reflectors comprises a partial-body reflector 704 tilted about the X-axis, and the second plurality of tilted partial-body reflectors comprises a partial-body reflector 705 tilted about the Z-axis. The tilted partial-body reflector 704 of the first plurality of tilted partial-body reflectors expands the light beam 715 along the Y-axis and the tilted partial-body reflector 705 of the second plurality of tilted partial-body reflectors expands the light beam 715 along the X-axis. In the illustrated embodiment, the illuminator 700 further includes a tiltable reflector 760, the tiltable reflector 760 being located in the optical path upstream of the light guide 702 for changing the angle of incidence of the light beam 715 onto the coupler 706 of the light guide 702. Tiltable reflector 760 can be, for example, a microelectromechanical system (MEMS) tiltable reflector. The embedded semi-transparent or partially reflective 750 may also be configured to split the light beam 715 prior to impinging on any tilted reflectors. The function of the partial reflector has been explained with reference to fig. 6A above.

Referring still to fig. 7A and 7B, the light beam 715 emitted by the light source 710 is redirected by the tiltable reflector 760 to impinge on the coupler 706, the coupler 706 coupling the light beam 715 into the light guide 702. The light beam 715 (which may be split by an optional partial reflector 750) impinges on the tilted partial-body reflector 705 of the second plurality of reflectors, which tilted partial-body reflector 705 of the second plurality expands the light beam 715 along the width dimension of the light guide (i.e., along the X-axis) to obtain an expanded light beam 740, which expanded light beam 740 is directed towards the tilted partial-body reflector 704 of the first plurality of reflectors. The tilted partial-body reflector 704 couples out a portion 720 of the light beam 715 through the first surface 711 along a length dimension of the light guide (i.e., along the Y-axis). The coupled-out beam portion 720 forms a wide output beam for illuminating the display panel 724.

The illuminator based on the geometric waveguide of the present disclosure can be used not only to illuminate reflective display panels, but also to illuminate transmissive display panels, i.e. as a backlight operation for transmissive panels. Referring to the non-limiting illustrative example of fig. 8, a display device 800 includes a transmissive display panel 824 shown in an exploded view and a light guide 802 that operates as a backlight for the transmissive display panel 824. The light guide 802 includes opposing first and second outer surfaces 811, 812, the first and second outer surfaces 811, 812 for guiding a light beam 815 coupled into the light guide 802 by the coupler 806, and a plurality of tilted body reflectors 804 extending between the first and second surfaces 811, 812 at an acute angle to the first and second surfaces 811, 812, the plurality of tilted body reflectors 804 for reflecting portions 820 of the light beam 815 out of the light guide 802 for illumination onto a display panel 824. The display panel 824 spatially modulates the beam portion 820 to provide an image in the linear domain. The coupler 806 may be, for example, a prism coupler, a diffraction grating coupler, or the like. The tilted-body reflector 804 may be a polarization-selective reflector that reflects light of a first linear polarization and transmits light of a second orthogonal polarization.

The display device 800 also includes imaging optics, such as an ophthalmic lens 816. As non-limiting examples, ophthalmic lenses 816 may include refractive lenses, reflectors, catadioptric lenses, wafer lenses, and the like. The function of the ophthalmic lens 816 is to convert an image in the linear domain formed by the display panel 824 into an image in the angular domain and to transfer the image in the angular domain to an eyebox of the display device 800 disposed downstream of the ophthalmic lens 816 for direct viewing of the image by the user's eye at the eyebox.

In the illustrated embodiment, the display panel 824 includes a clear linear transmissive polarizer 832, a bottom substrate 834 (e.g., thin film transistor (thin film transistor, TFT) substrate), a Liquid Crystal (LC) layer 836, a top substrate 808 (including, for example, a black grid defining an array of pixels and an optional color filter array), and an analyzer 840 (which may be a linear transmissive polarizer). Clean-up polarizer 832 and analyzer 840 polarizers may be laminated to respective bottom and top substrates 834, 838. In operation, the beam portions 820 reflected by the plurality of tilted polarization-selective reflectors 804 propagate through the transmissive display panel 824, thereby being spatially modulated by the spatially variable polarization transformation of the LC layer 836, and impinge on the ophthalmic lens 816 to form an image to be viewed.

In some embodiments, the illumination light may be patterned, i.e., focused, into an array of optical power density peaks to match the pattern of the pixel array of transmissive display panel 824, thereby increasing the optical throughput and overall electro-optic conversion efficiency of display device 800. Referring now to fig. 9 and with further reference to fig. 8, a focusing element 950 (e.g., a microlens array) may be added to the display device 800 of fig. 8 for forming a spot array 902 from the coupled-out light portion 820 downstream of the focusing element 950. The array of spots 902 is shown as a concentrated white spot above the focusing element 950. In operation, an array of optical power density peaks 904 is formed at the transmissive pixel array due to an optical effect known as the taber effect. A taber pattern 906 of illumination light is formed in the optical path between the focusing element 950 and a black grid 938 defining a transmissive pixel array including a clear polarizer 832, a bottom substrate 834, and an LC layer 836. The optical power density peak array 904 is shown as a concentrated white dot at the top of the taber pattern 906 below the black grid 938.

Examples of focusing elements 950 may include, for example, refractive microlens arrays, diffractive microlens arrays, liquid crystal microlens arrays, pancharatnam-Berry phase (PBP) microlens arrays, and the like. More generally, the focusing element 950 may include a phase/amplitude mask that performs the function of a microlens array (i.e., focuses the output beam formed by the coupled-out beam portion 820 into an array of light spots coordinated with the pixel array). The phase/amplitude mask may comprise, for example, an LC layer with spatially variable LC orientation, a patterned LC polymer, or nanostructures with spatially variable heights.

Referring to fig. 10, a method 1000 for illuminating a display panel includes propagating a light beam in a light guide of the present disclosure (1002), such as a geometric waveguide including a plurality of angled partial volume reflectors inside the light guide. The light beam propagates along the length dimension of the light guide by a series of internal reflections from opposing first and second outer surfaces of the light guide. Part of the light beam is coupled out through the first surface along a length dimension of the light guide by reflection from a plurality of angled partial volume reflectors inside the light guide (1004). An output beam for illuminating the display panel is formed (1006) from the coupled-out beam portion.

The method 1000 may be used to illuminate both reflective and transmissive display panels. For a reflective display panel, the method may further include reflecting (1008) the output light beam through the reflective display panel. Upon reflection, the output beam is spatially modulated in at least one of amplitude, phase, or polarization, depending on the display panel type, to form an image in the linear domain. The spatially modulated reflected light beam may then propagate (1010) through a light guide to impinge on an imaging optical component (e.g., an ophthalmic lens). The ophthalmic lens may form an image in the linear domain provided by the reflective display panel into an image in the angular domain.

Turning to fig. 11, a Virtual Reality (VR) near-eye display 1100 includes a frame 1101 that supports for each eye: a light source 1102; a luminaire 1106 operably coupled to the light source 1102 and comprising any of the luminaires disclosed herein; a display panel 1118 comprising an array of display pixels; and an ophthalmic lens 1132 for converting an image in the linear domain produced by the display panel 1118 into an image in the angular domain for direct viewing at the eyebox 1126. A plurality of eyebox illuminators 1162 (shown as black dots) may be disposed on the side of waveguide illuminator 1106 facing eyebox 1126. An eye tracking camera 1142 may be provided for each eye-ward region 1126.

The purpose of eye tracking camera 1142 is to determine the position and/or orientation of the user's two eyes. Eye position and orientation information may be used, for example, using tiltable reflectors 760 as described in fig. 7A and 7B, to steer the exit pupil of VR near eye display 1100 to the eye pupil position. The eyebox illuminator 1162 illuminates the eye at the corresponding eyebox 1126, allowing the eye tracking camera 1142 to obtain an image of the eye and provide a reference reflection, i.e., glint. Flicker may be used as a reference point in the acquired 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 distracting the user's light from the eyebox illuminator 1162, the eyebox illuminator may be caused to emit light that is invisible to the user. For example, infrared light may be used to illuminate the eyebox 1126.

Turning to fig. 12, hmd 1200 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 1200 may generate a fully virtual 3D image. HMD 1200 may include a front body 1202 and a belt 1204 that may be secured around the user's head. The front body 1202 is configured for placement in front of the user's eyes in a reliable and comfortable manner. A display system 1280 may be disposed in the front body 1202 for presenting AR/VR images to a user. Display system 1280 may include any of these display devices and illuminators disclosed herein. The side 1206 of the front body 1202 may be opaque or transparent.

In some embodiments, the front body 1202 includes a locator 1208 and an inertial measurement unit (inertial measurement unit, IMU) 1210 for tracking acceleration of the HMD 1200, and a position sensor 1212 for tracking a position of the HMD 1200. IMU 1210 is such an electronic device: the electronic device generates data indicative of a position of the HMD 1200 based on received measurement signals from one or more position sensors 1212 that generate one or more measurement signals in response to motion of the HMD 1200. Examples of the position sensor 1212 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 IMU 1210, or some combination thereof. The position sensor 1212 may be located external to the IMU 1210, internal to the IMU 1210, or some combination thereof.

The localizer 1208 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 1200. The information generated by the IMU 1210 and the position sensor 1212 may be compared to the position and orientation obtained by the tracking locator 1208 to improve the tracking accuracy of the position and orientation of the HMD 1200. As a 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 1200 may also include a Depth Camera Assembly (DCA) 1211 that collects data describing depth information of some or all surrounding local areas of the HMD 1200. The depth information may be compared to information from IMU 1210 in order to more accurately determine the position and orientation of HMD 1200 in 3D space.

The HMD 1200 may also include an eye tracking system 1214 for determining the orientation and position of a user's eyes in real-time. The acquired position and orientation of the eyes also allows the HMD 1200 to determine the gaze direction of the user and adjust the image generated by the display system 1280 accordingly. The determined gaze direction and vergence angle may be used to adjust the display system 1280 to reduce vergence adjustment conflicts. As disclosed herein, the direction and vergence may also be used for exit pupil steering of the 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, including, for example, a set of small speakers built into the front body 1202.

Embodiments of the present disclosure may include or be implemented in conjunction with an artificial reality system. The artificial reality system adjusts sensory information (e.g., visual information, audio, touch (somatosensory) information, acceleration, balance, etc.) about the outside world obtained through the sense of sense in some way, and then presents to the user. As non-limiting examples, artificial reality may include Virtual Reality (VR), 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 combined with collected (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 in 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 applications, products, accessories, services, or some combination thereof, for creating content in the artificial reality and/or otherwise for use in 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 a wearable display (e.g., an HMD connected to a host computer system), a stand-alone 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 the usefulness of the present disclosure 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 set forth below should be construed in view of the full breadth of the present disclosure as described herein.

Claims (15)

1. A luminaire for a display panel, the luminaire comprising:

A light guide for propagating a light beam along a length dimension of the light guide by a series of internal reflections from opposing first and second outer surfaces of the light guide, wherein the first and second surfaces are separated by a light guide thickness dimension perpendicular to the length dimension; and

A first plurality of angled portion bulk reflectors inside the light guide for coupling out portions of the light beam through the first surface along the length dimension of the light guide, the coupled out light beam portions forming an output light beam for illuminating the display panel.

2. The luminaire of claim 1 wherein a tilted-section reflector of the first plurality of tilted-section body reflectors comprises a polarization-selective reflector for reflecting light of a first polarization and transmitting light of a second orthogonal polarization; and preferably

The illuminator further includes a linear transmissive polarizer disposed proximate the second surface of the light guide and configured to transmit light of the second polarization.

3. The luminaire of claim 1 or 2, wherein the angled partial volume reflector extends from the first surface to the second surface of the light guide.

4. A luminaire according to claim 1,2 or 3, further comprising a diffuser upstream of the light guide for scattering the light beam within a predefined light cone; and preferably

Wherein the apex angle of the light cone is less than 4 degrees.

5. The luminaire of any one of the preceding claims, further comprising a partial reflector embedded in the light guide and disposed in the light path upstream of the first plurality of tilted partial-body reflectors, at a distance from and parallel to the first and second opposing outer surfaces, for separating the light beams, thereby increasing the spatial density of portions of the light beams coupled out of the light guide by the first plurality of tilted partial-body reflectors.

6. The luminaire of any one of the preceding claims, further comprising a second plurality of tilted partial-body reflectors disposed inside the light guide upstream of the first plurality of tilted partial-body reflectors for expanding the light beam along a width dimension of the light guide to obtain an expanded light beam and for directing the expanded light beam toward the first plurality of tilted partial-body reflectors.

7. A luminaire as claimed in any one of the preceding claims, further comprising a tiltable reflector located in the optical path upstream of the light guide, the tiltable reflector being for varying the angle of incidence of the light beam onto the light guide.

8. A luminaire according to any one of the preceding claims, wherein there is one of the following:

The lightguide thickness is less than 0.5mm;

a width of a tilted partial-body reflector of the first plurality of tilted partial-body reflectors located between the opposing first and second outer surfaces of the light guide is less than 0.7mm; or alternatively

At least some of the first plurality of tilted partial-body reflectors have a reflectivity greater than 50%.

9. The luminaire of any one of the preceding claims, wherein the tilted partial-body reflectors of the first plurality of tilted partial-body reflectors are parallel to each other within 0.5 degrees, and wherein at least some of the tilted partial-body reflectors of the first plurality of tilted partial-body reflectors are at an angle of at least 0.2 degrees relative to each other.

10. A display device, the display device comprising:

A display panel including a substrate and a pixel array supported by the substrate; and

A light guide for illuminating the pixel array of the display panel, the light guide comprising opposed first and second outer surfaces for guiding a light beam in the light guide, and a plurality of angled partial volume reflectors extending between the first and second surfaces at an acute angle thereto for reflecting portions of the light beam out of the light guide for illumination onto the pixel array of the display panel.

11. The display device of claim 10, further comprising an ophthalmic lens downstream of the array of pixels, wherein the ophthalmic lens is configured to convert an image in a spatial domain displayed by the display panel into an image in an angular domain downstream of the ophthalmic lens for viewing by a user's eye downstream of the ophthalmic lens.

12. The display device of claim 11, wherein,

The pixel array is a reflective pixel array; and

The light guide is disposed between the display panel and the ophthalmic lens;

Wherein, in operation, the portions of the light beam reflected by the plurality of tilted partial-body reflectors impinge upon the reflective pixel array, thereby being reflected, propagate back through the light guide, and impinge upon the ophthalmic lens; and preferably

I. wherein the reflective pixel array is configured to controllably tune the polarization of the illuminated beam portion from a first polarization state to an orthogonal second polarization state; and

The tilted reflector is polarization-selective and configured to reflect light of the first polarization state and to transmit light of the second polarization state; and/or preferably

The display device further comprises a linear transmissive polarizer located between the light guide and the ophthalmic lens.

13. The display device of claim 11, wherein,

The pixel array comprises a transmissive pixel array; and

The display panel is disposed between the light guide and the ophthalmic lens;

Wherein, in operation, the portions of the light beam reflected by the polarization selective plurality of tilted reflectors propagate through the substrate, through the transmissive pixel array, and impinge on the ophthalmic lens; and preferably

The display device further comprises a focusing element for forming an array of light spots from the coupled-out light portion downstream of the focusing element, such that in operation an array of light power density peaks is formed at the transmissive pixel array due to the taber effect.

14. A method for illuminating a display panel, the method comprising:

propagating a light beam in the light guide along a length dimension by a series of internal reflections from opposing first and second outer surfaces of the light guide;

coupling out a portion of the light beam through the first surface along the length dimension of the light guide using a plurality of angled partial volume reflectors inside the light guide; and

An output beam for illuminating the display panel is formed from the coupled-out beam portions.

15. The method of claim 14, wherein the display panel is a reflective display panel, the method further comprising:

Reflecting the output light beam through the reflective display panel; and

The output light beam reflected by the reflective display panel is propagated through the light guide.