TW202305430A - Waveguide illuminator with optical interference mitigation - Google Patents

Abstract

A waveguide illuminator includes an input waveguide, a waveguide splitter coupled to the input waveguide, and a waveguide array coupled to the waveguide splitter. The waveguide array includes an array of out-couplers out-coupling portions of the split light beam to form an array of out-coupled beam portions for illuminating a display panel. To reduce optical interference, the waveguide illuminator may have two interlaced waveguide arrays energized by two different light sources. Output polarizations of neighboring light pixels of a display illuminated with such waveguide illuminator may be orthogonal to each other. The frames to be displayed may be broken down into sequentially displayed sub-frames with interleaved pixels.

Description

Waveguide Illuminators with Optical Interference Mitigation

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

This application claims U.S. Provisional Patent Application No. 63/222,224, filed July 15, 2021, entitled "Single Mode Backlight Illuminator," and U.S. Nonprovisional Patent Application No. 17/556,895, filed December 20, 2021 No., and these patent applications are incorporated herein by reference in their entirety.

Visual displays provide information, including still images, video, data, etc., to a viewer. Visual displays have applications in diverse fields including entertainment, education, engineering, science, professional training, advertising, just to name a few. Some visual displays, such as televisions, display images to several users, and some visual display systems, such as near-eye displays (NEDs), are intended for individual users.

An artificial reality system typically includes a NED (eg, a headset or a pair of glasses) configured to present content to a user. Near-eye displays can display virtual objects or combine images of real and virtual objects, such as in virtual reality (VR), augmented reality (AR) or mixed reality (MR) applications . For example, in an AR system, a user can observe an image of a virtual object (eg, a computer-generated image (CGI)) superimposed on the surrounding environment by observing a "compositor" component. The combiner of a wearable display is typically transparent to external light, but includes some light routing optics to direct display light into the user's field of view.

Since the display of an HMD or NED is typically worn on the user's head, a large, bulky, unbalanced and/or heavy display device with a heavier battery would be cumbersome and uncomfortable for the user to wear. Thus, head-mounted display devices can benefit from a compact and efficient configuration, including efficient light sources and illuminators that provide illumination of the display panel, high-throughput eye lenses, and other optical elements in image-forming training.

An aspect of the present invention is a waveguide illuminator, which includes: first and second waveguide beam splitters configured to respectively receive first and second light beams for splitting the first and second light beams into first and second light beams respectively one and second plurality of sub-beams; first and second waveguide arrays, respectively coupled to the first and second waveguide beam splitters, and configured to propagate sub-beams of the first and second plurality of sub-beams, respectively, wherein the The waveguides of the first and second waveguide arrays are interleaved and run parallel to each other; and an array of columns of output couplers, each column of output couplers in the array being coupled to the first or second waveguide along the length of the waveguide The waveguides in the two-waveguide array are used to form a two-dimensional array of interleaved out-coupled sub-beam portions of the first and second plurality of sub-beams.

In the waveguide illuminator according to the foregoing aspect of the present invention, the first and second waveguide arrays are coupled to the first and second waveguide splitters at opposite ends of the first and second waveguide arrays, such that the The sub-beams of the first and second plurality of sub-beams counter-propagate in respective waveguide arrays.

In the waveguide illuminator according to the foregoing aspect of the invention, output couplers of adjacent columns of said output couplers are offset relative to each other in a direction along the waveguides of the first and second waveguide arrays To form a diamond array of output couplers.

The waveguide illuminator according to the foregoing aspect of the present invention further includes a first light beam respectively coupled to the first and second waveguide beam splitters for providing the first and second light beams to the first and second waveguide beam splitters. One and the second semiconductor light source.

In the waveguide illuminator according to the foregoing aspect of the present invention, the first and second semiconductor light sources are configured to emit light of different wavelengths of the same color channel.

In the waveguide illuminator according to the aforementioned aspect of the present invention, the first and second semiconductor light sources include laser diodes with different emission wavelengths.

The waveguide illuminator according to the foregoing aspects of the present invention further includes a controller coupled to the first and second semiconductor light sources and configured to alternately operate the first and second semiconductor light sources in a time-sequential manner.

Another aspect of the present invention is a display device, which includes: a display panel including a two-dimensional pixel array; and a waveguide illuminator configured to illuminate the display panel and including: a waveguide beam splitter configured to receive a light beam and splitting the beam into a plurality of sub-beams; an array of waveguides coupled to the waveguide splitter and configured to propagate the sub-beams therein, the waveguides of the waveguide array running parallel to each other; and an array of output couplers in columns, the each column of output couplers in the array coupled to a waveguide in the waveguide array along the length of the waveguide for forming a two-dimensional array of outcoupled sub-beam portions; and a spatially variant polarizer disposed on the display panel downstream and configured to propagate the outcoupling sub-beam portion of the first polarization state and block the outcoupling adjacent sub-beam portion of the second orthogonal polarization state.

In the display device according to another aspect of the present invention, the spatially variant polarizer comprises transversely joined linear polarizer segments oriented orthogonally to the polarization transfer axes.

In the display device according to another aspect of the present invention, the linear polarizer segments with the same polarization direction are arranged in a checkerboard pattern.

In the display device according to another aspect of the present invention, the spatially variable polarizer includes a linear polarizer and a spatially variable waveplate downstream of the linear polarizer, and the spatially variable waveplate includes The waveplate sections that are joined transversely in different optical axis directions.

In the display device according to another aspect of the present invention, the wave plate segments in the same optical axis direction are arranged in a checkerboard pattern.

Still another aspect of the present invention is a display device, which includes: a display panel including a two-dimensional pixel array; and a waveguide illuminator configured to illuminate the display panel and including: a waveguide beam splitter configured to receive a light beam and splitting the beam into a plurality of sub-beams; an array of waveguides coupled to the waveguide splitter and configured to propagate the sub-beams therein, the waveguides of the waveguide array running parallel to each other; and an array of output couplers in columns, the Each column of output couplers in the array is coupled to a waveguide in the waveguide array along the length of the waveguide for forming a two-dimensional array of outcoupled sub-beam portions corresponding to the two-dimensional pixel array of the display panel.

The display device according to yet another aspect of the present invention further includes a controller operatively coupled to the display panel and configured to cause the display panel to display a plurality of sub-images in a time-sequential manner, the sub-images adding up to is the image to be displayed to the user.

In the display device according to still another aspect of the present invention, pixels of different sub-images of the plurality of sub-images are interlaced.

In the display device according to still another aspect of the present invention, pixels of different sub-images of the plurality of sub-images are arranged in a complementary checkerboard pattern.

In the display device according to another aspect of the present invention, the plurality of sub-images include a first sub-image and a second sub-image with interlaced pixels, so that each pixel in the first sub-image has the second sub-image At least two adjacent pixels of the sub-image.

In the display device according to still another aspect of the present invention, each pixel in the first sub-image has at least three adjacent pixels in the second sub-image.

In the display device according to still another aspect of the present invention, the display panel includes a transmissive light valve array.

In the display device according to still another aspect of the present invention, the display panel includes a liquid crystal layer.

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

As used herein, the terms "first," "second," and the like are not intended to imply a sequential order, but are intended to distinguish one element from another unless expressly stated otherwise. Similarly, the sequential order of method steps does not imply a sequential order for their performance unless expressly stated. In FIG. 1 , FIG. 7 and FIG. 8 , like numbers refer to like elements. Also in FIGS. 3A, 3B to 6A, 6B, like numbers refer to 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 microdisplays typically used in near-eye and/or head-mounted displays, this ratio may be less than 50%. Efficient backlight utilization is further hampered by color filters on the display panel, which transmit no more than 30% of the incident light on average. In addition, polarization-based display panels (such as liquid crystal (LC) display panels) may have 50% polarization loss. All of these factors significantly reduce the light utilization of the display and the overall wall plug efficiency, which is undesirable.

According to the present disclosure, light utilization and wall plug efficiency of backlit displays can be improved by providing a waveguide illuminator comprising an array of output couplers aligned with the pixels of the display panel. In displays where the illuminators emit light of primary colors, such as red, green and blue, the color of the illumination light can be matched to color filters, or the color filters can be omitted entirely. For polarization-based displays, the polarization of emitted light can be matched to a predefined input polarization state. Matching the spatial distribution, transmitted wavelength and/or transmitted polarization characteristics of the pixels of the display panel allows us to 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 the wall-plug efficiency of the display is significantly improved.

Single- or minority-mode waveguides (eg, ridge waveguides with up to 12 propagation modes) combined with laser illumination allow efficient control of light properties such as color and directionality. When light propagates in a single spatial mode, the output can be diffraction limited and highly directional. Single-mode propagation also allows us to have light outcoupled in specific points on the waveguide and incorporated into focusing pixels that can focus the light into the pixels of the display panel while avoiding scattering in the inter-pixel regions. The narrow spectrum of laser illumination enables large color gamut displays. Furthermore, the single-mode waveguide can maintain polarization, which results in a highly polarized output from the backlight unit without the need for polarizers.

Due to the coherent nature of propagating light, illuminators based on single-mode waveguides can be prone to speckle patterns caused by optical interference between different sub-beams of outcoupled coherent light. According to the present disclosure, the effect of speckle formation can be mitigated by ensuring that adjacent outcoupled beamlets of illumination light do not interfere with each other on the retina of the user's eye. Thus, it is possible, for example, by destroying the coherence between adjacent beamlets, by ensuring that their polarizations are mutually orthogonal, and/or by ensuring that only one of two adjacent beamlets is at any given time Down to the user's eyes to achieve.

According to the present disclosure, there is provided a waveguide illuminator comprising first and second waveguide beam splitters configured to receive first and second light beams, respectively, for splitting the first and second light beams into first and second pluralities, respectively Son of Beam. The first and second waveguide arrays are respectively coupled to the first and second waveguide beam splitters, and configured to propagate sub-beams of the first and second plurality of sub-beams respectively. The waveguides of the first and second waveguide arrays are staggered and run parallel to each other. The waveguide illuminator includes an array of columns of output couplers. Each column of output couplers of the array is coupled to a waveguide of the first or second waveguide array along the length of the waveguide for forming a two-dimensional array of interleaved outcoupled beamlet portions of the first and second plurality of beamlets.

In some embodiments, wherein the first and second waveguide arrays are coupled to the first and second waveguide beamsplitters at opposite ends of the first and second waveguide arrays, such that sub-beams of the first and second plurality of sub-beams are at counter-propagate in the respective waveguide arrays. The output couplers of adjacent columns of output couplers may be offset relative to each other in a direction along the waveguides of the first and second waveguide arrays to form a diamond-shaped array of output couplers. The waveguide illuminator may further include first and second semiconductor light sources respectively coupled to the first and second waveguide beam splitters for providing the first and second light beams to the first and second waveguide beam splitters. The first and second semiconductor light sources can be configured to emit light of different wavelengths of the same color channel. The first and second semiconductor light sources may comprise laser diodes with different emission wavelengths. The controller can be coupled to the first and second semiconductor light sources. The controller may be configured to alternately operate the first and second semiconductor light sources in a time-sequential manner.

According to the present disclosure, there is provided a display device, which includes: a display panel including a two-dimensional pixel array; the waveguide illuminator of the present disclosure; and a spatially variable polarizer. A waveguide illuminator is configured to illuminate the display panel. The waveguide illuminator may include: a waveguide beam splitter configured to receive a beam of light and split the beam into a plurality of sub-beams; a waveguide array coupled to the waveguide beam splitter and configured to propagate the sub-beams therein, the waveguides of the waveguide array being parallel to each other and an array of columns of output couplers, each column of output couplers of the array coupled to a waveguide of the waveguide array along the length of the waveguide for forming a two-dimensional array of outcoupled sub-beam portions. A spatially variant polarizer may be disposed downstream of the display panel and configured to propagate an outcoupled beamlet portion of a first polarization state and block an outcoupled adjacent beamlet portion of a second orthogonal polarization state.

A spatially variant polarizer may comprise transversely joined linear polarizer segments oriented orthogonally with polarization transfer axes. Linear polarizer segments of the same polarization direction can be arranged in a checkerboard pattern. A spatially varying polarizer may comprise a linear polarizer and a spatially varying waveplate downstream of the linear polarizer, the spatially varying waveplate comprising transversely joined waveplate segments of different optical axis orientations arranged in a checkerboard pattern. The wave plate sections with the same optical axis direction can be arranged in a checkerboard pattern.

According to the present disclosure, a display device is further provided, which includes a display panel and the waveguide illuminator of the present disclosure. The display panel may include a two-dimensional array of pixels, eg, an array of transmissive light valves, that may be formed in a liquid crystal layer. The waveguide illuminator may include: a waveguide beam splitter configured to receive a beam of light and split the beam into a plurality of sub-beams; a waveguide array coupled to the waveguide beam splitter and configured to propagate the sub-beams therein, the waveguides of the waveguide array being parallel to each other direction; and an array of columns of output couplers, each column of the output couplers of the array being coupled to a waveguide of the waveguide array along the length of the waveguide for forming an outcoupled sub-beam portion corresponding to a two-dimensional pixel array of a display panel The two-dimensional array.

The display device may further include a controller operatively coupled to the display panel and configured to cause the display panel to display in a time-sequential manner a plurality of sub-images that add up to an image to be displayed to a user. Pixels of different sub-images of the plurality of sub-images may be interleaved with each other. For example, pixels of different sub-images of the plurality of sub-images may be arranged in a complementary checkerboard pattern. The plurality of sub-images may include first and second sub-images having interlaced pixels such that each pixel in the first sub-image has at least two adjacent pixels of the second sub-image. Each pixel in the first sub-image may have at least three neighboring pixels of the second sub-image.

Referring now to FIG. 1, a waveguide illuminator 100 includes a substrate 101 supporting an input waveguide 106 for guiding an input beam 108 provided by a light source 110, such as a laser source. Herein, the term "waveguide" designates a light-guiding structure that confines light propagation in two dimensions (eg light rays) and guides light in a single transverse mode or in several transverse modes (eg up to 12 propagation modes). The waveguides may be straight, curved, etc. One example of a linear waveguide is a ridge waveguide. The waveguide illuminator 100 may be implemented in a photonic integrated circuit (PIC).

A waveguide splitter 112 is coupled to the input waveguide 106 . The function of the waveguide beam splitter 112 is to split the input beam 108 into a plurality of sub-beams 114 . The waveguide array 116 is coupled to the waveguide splitter 112 for guiding the sub-beams 114 in the waveguides 116 . The waveguides 116 are shown running parallel to each other. Each waveguide 116 is configured to direct one of the sub-beams 114 from the waveguide splitter 112 to the end 129 of the waveguide 116 .

The array of columns 119 of output couplers 120 is supported by the base 101 of the waveguide illuminator 100 . Each column 119 of output couplers 120 is coupled to one of the waveguides 116 along the length of the waveguides 116 for outcoupling a portion 122 of one of the sub-beams 114 propagating in the waveguide 116 . Portions 122 outcoupled by all columns 119 of output couplers 120 form a two-dimensional array of sub-beam portions 122 that are outcoupled from the waveguide array and emitted to substrate 101 at an angle, including acute or right. The X-pitch and Y-pitch of the two-dimensional array of sub-beam portions 122 may be selected to match the X-pitch and Y-pitch of a display panel illuminated by waveguide illuminator 100 .

Referring to FIG. 2 with further reference to FIG. 1 , a display device 200 includes the waveguide illuminator 100 of FIG. 1 , or any other waveguide illuminator disclosed herein. The waveguide illuminator 100 is coupled to a display panel 202 (FIG. 2). A light source 201 , such as a semiconductor light source at a wavelength of a color channel, may be optically coupled to the luminaire 100 for providing a light beam 108 to the luminaire 100 . Display panel 202 includes a two-dimensional array of display pixels 220 , eg, an array of transmissive light valves, disposed and configured to receive an array of outcoupled beamlet portions 122 from illuminator 100 . To ensure efficient use of sub-beam portions 122, the position and pitch of display pixels 220 and the array of output couplers 120 can be matched in both the X and Y directions. The pitch between display pixels 220 may be substantially equal to the pitch of the array of output couplers 120 .

The display device 200 may further include operably coupled to the light source 201 and the display panel 202 for powering the light source 201 while providing controls for setting individual optical transmission values or other properties (such as polarization conversion properties) of the display pixels 220 Signal controller 250 . In some embodiments, the display panel 202 may include a liquid crystal layer 204 in which the display pixels 220 are configured to individually and controllably switch or tune the polarization state of individual beamlet portions 122, eg, rotate the linear polarization state. In such specific examples, light source 201 may be a polarized light source that emits linearly polarized light. A linear polarizer 228 may be provided to convert the polarization distribution of the sub-beam portions 122 imparted by the display pixels 220 into an optical power density distribution or brightness distribution representative of the image to be displayed. A polarizer that converts a polarization distribution into an optical power density or brightness distribution is often called an analyzer. The liquid crystal pixels are combined with an analyzer to form an array of pixels with light valves with controllable optical transmission.

The image formed downstream of the linear polarizer 228 is in the linear domain, where the pixel coordinates of the displayed image correspond to the XY coordinates of the display pixels 220 . The eye lens 230 can be used to convert an image in the linear domain to an image in the angular domain at the eye window 226 for direct observation by the eye 280 . Herein, the term “image in the angle domain” refers to an image in which the pixel coordinates of the displayed image correspond to the ray angles of the sub-beam portion 122 . In an embodiment with a tunable polarization rotator, light source 201 can emit polarized light, and waveguide illuminator 100 can preserve that polarization state. In some embodiments, waveguide illuminator 100 can be made transparent to external light 214 .

One potential problem associated with using a coherent light source to illuminate a display panel, such as light source 201 illuminating display panel 202, is speckle pattern formation. Due to the coherent nature of the light source 201, the light spot can be observed by the eye 280.

Figure 3 shows the origin of such speckle patterns. 3 is a magnified view of display 200 of FIG. Light paths 320A, 320B of adjacent sub-beam portions 122 . Due to the defective nature of the overall imaging exercise (including eye lens 230 and eye lens/cornea 380 ), images 328A and 328B of adjacent display pixels 220A and 220B may overlap to some extent on retina 302 . Optical interference pattern 300 may be present in an overlapping region between image 328A and image 328B of adjacent display pixel 220A and display pixel 220B. The optical interference pattern 300 will also appear between other adjacent pixel images, not shown for clarity. The net result of the formation of the optical interference pattern 300 is that the overall visible image is highly speckle, resulting in a distracting, unnatural appearance of the observed image.

One approach to mitigate optical interference pattern 300 is to provide a waveguide illuminator with a plurality of phase-independent light sources. Such light sources may be at slightly different emission wavelengths such that beams emitted by such sources do not show visible interference patterns when overlapping. Referring to FIG. 4A for a non-limiting illustrative example, waveguide illuminator 400A is similar to waveguide illuminator 100 of FIG. 1 , includes similar elements, may be implemented as a PIC, and may be used in display device 200 of FIG. 2 . Similar to the waveguide illuminator 100, the waveguide illuminator 400A of FIG. 4A includes a substrate 401 supporting a first input light beam provided by a first light source 410 (eg, a semiconductor light source such as a laser diode) for guiding 408 of the first input waveguide 406 . The first waveguide splitter 412 is coupled to the first input waveguide 406 . The function of the first waveguide beam splitter 412 is to split the first input beam 408 into a first plurality of sub-beams 414 . The waveguides 416 of the first array are coupled to the first waveguide splitter 412 for propagating the sub-beams 414 in the waveguides 416 of the first array. The waveguides 416 are shown running parallel to each other. Each waveguide 416 is configured to guide one of the sub-beams 414 . A first array of output couplers 420 configured in columns corresponding to individual waveguides 416 is supported by substrate 401 . Each column of output couplers 420 is coupled to one waveguide 416 of the first array of waveguides along the length of the waveguides 416 for outcoupling a portion 422 of one of the sub-beams 414 propagating in the waveguides 416 . Section 422 forms a first two-dimensional array of outcoupled sub-beam sections.

The waveguide illuminator 400A further comprises a second input waveguide 407 for guiding a second input light beam 409 provided by a second light source 411 (eg, a semiconductor light source such as a laser diode) at an opposite side of the substrate 401 . The second waveguide splitter 413 is coupled to the second input waveguide 407 for splitting the second input beam 409 into a second plurality of sub-beams 415 . A second array of waveguides 417 is coupled to a second waveguide splitter 413 for propagating sub-beams 415 in waveguides 417 . The waveguides 417 of the second waveguide array are parallel to each other and run between the waveguides 416 of the first waveguide array, that is, the waveguides 416 of the first waveguide array and the waveguides 416 of the first waveguide array are interlaced. The first waveguide splitter 412 and the second waveguide splitter 413 are disposed at opposite ends of the first and second waveguide arrays, ie to the left and right of the arrays in FIG. 4A .

Each waveguide 417 of the second waveguide array is configured to guide one sub-beam 415 . A second array of output couplers 421 arranged in columns is supported by substrate 401 . Each column of output couplers 421 is coupled along the length of waveguides 417 to one of the waveguides 417 of the second waveguide array for outcoupling sections 423, thereby forming a second two-dimensional array of outcoupled sub-beam sections. The first input beam 408 and the second input beam 409 can be launched into respective interleaved waveguide arrays from two opposite sides of the waveguide illuminator 400A along the parallel waveguide 416, waveguide 417 pair.

The two arrays of outcoupled beam sections 422 and 423 are interleaved as a result of waveguides 416 and 417 of the first and second waveguide arrays, and correspondingly output couplers 420 and 421 are interleaved as shown out. The sub-beams 414 and 415 split from the first input beam 408 and the second input beam 409 propagate in opposite directions, ie counterpropagate thereof. The first light source 410 and the second light source 411 may be configured to emit light of different wavelengths, for example, wavelengths of the same color channel; for example, the first light source 410 and the second light source 411 may comprise laser diodes emitting at different wavelengths , making stable optical interference pattern formation possible. The staggered configuration shown in FIG. 4 allows one to reduce or completely eliminate unwanted optical interference effects between adjacent out-coupled beam portions 422 and 423, thereby reducing or eliminating the adverse effect of speckle pattern formation.

In some embodiments, the waveguide illuminator 400A of FIG. 4A can include a controller 450 coupled to the first light source 410 and the second light source 411 . The controller 450 may be configured to alternately operate the first semiconductor light source 410 and the second semiconductor light source 411 in a time-sequential manner to suppress interference between adjacent out-coupled beam portions 422 and 423 . When the first light source 410 and the second light source 411 are operated in a time-sequential manner, no interference occurs even when the emission spectra of the first light source 410 and the second light source 411 completely or partially overlap.

In some embodiments, the first input beam 408 and the second input beam 409 may be emitted by the same laser source coupled to the beam splitter, wherein sufficient path length between the first input beam 408 and the second input beam 409 destroys Phase coherent and rejects interference anywhere inside the output area. Referring to FIG. 4B for a non-limiting illustrative example, waveguide illuminator 400B is similar to waveguide illuminator 400A of FIG. 4A , includes similar elements, can be implemented in a PIC, and can be used in display device 200 of FIG. 2 . The waveguide illuminator 400B of FIG. 4B has a single light source, specifically the first light source 410; The light is split into a first input beam 408 and a second input beam 409, and the first input beam 408 and the second input beam 409 are coupled to a first waveguide beam splitter 412 and a second waveguide beam splitter 413, respectively. The difference in optical path length from the first light source 410 to the first waveguide beam splitter 412 and the second waveguide beam splitter 413 is greater than the coherence length of the first light source 410 . In FIG. 4B , the path length difference is approximately equal to the length of the auxiliary waveguide 478 going from the light source beam splitter 477 to the second waveguide beam splitter 413 .

In near-eye displays, optical interference and associated unwanted speckle pattern formation results from adjacent sub-beam portions corresponding to adjacent pixels of a display panel illuminated with a waveguide illuminator overlying the retina of the user's eye. As explained above with reference to FIG. 3 , such sub-beam spot overlap results from imperfections in the optical system that magnify the image of adjacent pixels on the retina. Thus, increasing the distance between the spots of adjacent sub-beam portions from the illuminator can result in a reduction of unwanted interference and suppression of speckle patterns. Such distance increases can be achieved by carefully choosing the spatial pattern of the illumination light. Referring to FIG. 5, for a non-limiting illustrative example, an embodiment 500 of the display device 200 of FIG. 2 may use the waveguide illuminator 400A of FIG. 4A or the waveguide illuminator 400B of FIG. 4B. In FIG. 5, the pixels 220 of the display panel 202 form a rectangular array of pixels depicted with thick dashed lines. The output couplers 420 and output couplers 421 of adjacent columns of output couplers are offset relative to each other in the direction of the waveguides 416, 417 (ie, horizontally in FIG. Each of the pixels 220 of the diamond-shaped, rectangular array of pixels is still illuminated with one of the output couplers 420, 421 of the diamond-shaped array of output couplers. Such a configuration enables the output couplers 420, 421 to be spaced farther apart from each other, thereby reducing the intensity of optical interference between sub-beam portions outcoupled by adjacent output couplers 420, 421, and thus suppressing speckle pattern formation.

Optical interference between adjacent out-coupling sub-beam portions can also be suppressed or mitigated by ensuring that adjacent out-coupling sub-beam portions have orthogonal polarization states. To this end, a spatially varying polarizer may be placed downstream of a display panel, eg, display panel 202 of display device 200 of FIG. 2 . For example, referring to FIG. 6 and with further reference to FIG. 2 , spatially varying polarizer 600 ( FIG. 6 ) may be placed in place of linear polarizer/analyzer 228 ( FIG. 2 ), and in the specific example shown in FIG. 6 , The spatially variant polarizer 600 comprises transversely joined linear polarizer segments 601, 602 with orthogonally oriented polarization transfer axes. Spatially variant polarizer 600 is thus configured to propagate outcoupling sub-beam portions of a first polarization state and block outcoupling adjacent sub-beam portions of a second orthogonal polarization state. Projected adjacent sub-beam portions 122 will be orthogonally polarized and thus optical interference between them will be suppressed.

The display panel 202 can be calibrated to act as different waveplates depending on the corresponding polarizer orientation of each given pixel 220 . Light transmitted through pixel 220 under different linear polarizations will not experience optical interference. The checkerboard pattern of transmission polarization orientations increases the distance between pixels 220 and beamlet portions 122 of the same polarization state, thereby reducing the likelihood of them overlapping at the retina of the user's eye, as explained above with reference to FIG. 3 .

Referring now to FIGS. 7A and 7B and with further reference to FIG. 2 , a spatially variant polarizer 700 may be placed in place of the linear polarizer/analyzer 228 . In the depicted example, the spatially varying polarizer 700 includes a uniform linear polarizer 710 and a spatially varying waveplate 720 downstream of the uniform linear polarizer 710 . The space variant waveplate 720 comprises transversely joined waveplate sections 721 , 722 of different optical axis directions. For half-wave boards, the directions can vary by 45 degrees. The wave plate segments 721, 722 in the same optical axis direction can be arranged in a complementary checkerboard pattern, as shown.

In some embodiments of the present disclosure, optical interference/speckle effects in display devices caused by coherent illumination can be mitigated by controlling individual pixels of the display to provide non-zero optical power density only for non-adjacent pixels, where All pixels are ultimately powered in a time-sequential manner. To this end, the controller 250 of the display device 200 of FIG. 2 may be configured to cause the display panel 202 to display a plurality of sub-images in a time-sequential manner, which add up to an image to be displayed to the user.

Referring to FIG. 8, for a non-limiting illustrative example, an image 800 to be displayed to a user includes a two-dimensional array of brightness values represented by numbers placed in individual pixels. The sum of the first sub-image 801 and the second sub-image 802 is an image 800 . In other words, the sum of the corresponding pixel values of the first sub-image 801 and the second sub-image 802 is the pixel value of the image 800 . For example, pixel 820 of image 800 has a value of 17. This value is represented by the sum of a pixel 821 of the first sub-image 801 having a value of zero and a pixel 822 of the second sub-image 802 having a value of 17. Similarly, pixel 830 of image 800 has a value of 64. This value is represented by the sum of a pixel 831 of the first sub-image 801 having a value of 64 and a pixel 832 of the second sub-image 802 having a value of zero.

The sub-images 801 and 802 may be displayed by the controller 250 in a time-sequential manner, ie displayed rapidly one after the other, so that the user's eyes integrate them into a single image. The pixels of different sub-images of the plurality of sub-images may be interleaved, for example, the pixels of different sub-images with non-zero intensity values may be arranged in a complementary checkerboard pattern, as shown in FIG. 8 . The interleaving of non-zero pixel values ensures that no light from adjacent pixels can interfere with the retina of the user's eye. The end result will be suppression of visible speckles/interference patterns.

More than two sub-images can be provided, where the same principle is that the pixel intensity values add up to the desired image. Depending on the total number of sub-images and the boundary or frame position of the pixels of the first sub-image, a pixel may have at least one adjacent pixel of the second image, at least two adjacent pixels of the second sub-image, or at least three or four adjacent pixels. For definition, adjacent pixels are defined herein as sharing at least one side border.

It should be further noted that the optical interference/speckle mitigation arrangements and methods disclosed herein are not mutually exclusive and may be used in a complementary manner. For example, the counter-propagation of the sub-beams in the interleaved waveguides shown in Figures 4A and 4B can be supplemented by the time-sequential energization of the corresponding light sources, providing the output by means of the analyzer presented in Figures 7A and 7B Interleave polarization, and/or provide sub-images in a time-sequential manner. The time-sequential light source energization can be supplemented by the time-sequential sub-image display shown in FIG. 8 or by other methods disclosed herein. Time-sequential sub-image displays can be complemented by checkerboard output polarization, etc.

Referring to FIG. 9, a virtual reality (VR) near-eye display 900 includes a frame 901 that supports, for each eye: a light source 902; a waveguide illuminator 906 operatively coupled to the light source 902, the waveguide illuminator 906 including Any of the waveguide illuminators disclosed herein; a display panel 918 comprising an array of display pixels in which the positions of the outcoupling gratings in the waveguide illuminator 906 are coordinated with the positions of the polarization tuning pixels of the display panel 918; and the eye The external lens 932 is used to convert the image in the linear domain generated by the display panel 918 into an image in the angular domain for direct observation at the human eye window 926 . A plurality of eye window illuminators 962 , shown as black dots, may be placed on the side of waveguide illuminator 906 facing eye window 926 . Eye tracking cameras 942 may be provided for each eye window 926 .

The purpose of the eye tracking camera 942 is to determine the position and/or orientation of the user's two eyes. The eye window illuminator 962 illuminates the eye at the corresponding eye window 926 to allow the eye tracking camera 942 to obtain an image of the eye and to provide a reference reflection, ie, a flash. The flash of light can serve as a reference point in capturing an image of the eye, thereby facilitating eye gaze direction determination by determining the position of the eye pupil image relative to the flash image. In order to avoid distracting the user's attention by the light of the eye window illuminator 962, the eye window illuminator 962 can be made to emit light that is invisible to the user. For example, infrared light can be used to illuminate the window 926 of the human eye.

Referring to FIG. 10 , HMD 1000 is an example of an AR/VR wearable display system, and the AR/VR wearable display system encloses the user's front for greater immersion in the AR/VR environment. HMD 1000 can produce completely virtual 3D images. The HMD 1000 can include a front body 1002 and a strap 1004 that can be secured around a user's head. The front body 1002 is configured for placement in front of the user's eyes in a secure and comfortable manner. The display system 1080 can be disposed in the front body 1002 to present AR/VR images to the user. Display system 1080 may include any of the display devices and illuminators disclosed herein. The side 1006 of the front body 1002 may be transmissive or transparent.

In some embodiments, the front body 1002 includes a positioner 1008 and an inertial measurement unit (IMU) 1010 for tracking the acceleration of the HMD 1000 , and a position sensor 1012 for tracking the position of the HMD 1000 . IMU 1010 is an electronic device that generates data indicative of the position of HMD 1000 based on measurement signals received from one or more of position sensors 1012, the electronic device generating one or more measurement signal. Examples of position sensors 1012 include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor to detect motion, error correction for IMU 1010 A type of sensor or a combination thereof. Position sensor 1012 may be located external to IMU 1010, internal to IMU 1010, or some combination thereof.

The locator 1008 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 1000 . Information generated by IMU 1010 and position sensor 1012 may be compared with the position and orientation obtained by tracking locator 1008 and used to improve the tracking accuracy of HMD 1000's position and orientation. As the user moves and turns in 3D space, accurate position and orientation are critical to presenting the proper virtual scene to the user.

HMD 1000 may further include a depth camera assembly (DCA) 1011 that captures data describing depth information surrounding some or all of the local area of HMD 1000 . The depth information can be compared with information from IMU 1010 for better accuracy in determining the position and orientation of HMD 1000 in 3D space.

The HMD 1000 may further include an eye tracking system 1014 for determining the orientation and position of the user's eyes in real time. The obtained position and orientation of the eyes also allows the HMD 1000 to determine the direction of the user's gaze and adjust the image generated by the display system 1080 accordingly. The determined gaze direction and vergence angle can be used to adjust the display system 1080 to reduce vergence accommodation conflicts. Direction and vergence may also be used for exit pupil steering of displays as disclosed herein. In addition, the determined vergence and gaze angle can be used to interact with the user, highlight objects, bring objects to the foreground, generate additional objects or indicators, and the like. The audio system may also provide a smaller set of speakers including, for example, built into the front body 1002 .

Embodiments of the present disclosure may include an artificial reality system, or may be implemented in combination with an artificial reality system. The artificial reality system adjusts sensory information about the external world obtained through sensing in a certain way before displaying it to the user, such as visual information, audio, contact (somatosensory) information, acceleration, balance, etc. By way of non-limiting example, artificial reality may include virtual reality (VR), augmented reality (AR), mixed reality (MR), composite reality, or some combination and/or derivative thereof. Artificial reality content may include fully generated content or generated content combined with captured (eg, real world) content. Artificial reality content may include video, audio, physical or tactile feedback, or some combination thereof. Any of this content may be presented to the viewer in a single channel or in multiple channels, such as in stereoscopic video producing a three-dimensional effect. Additionally, in some embodiments, AR may also be used in conjunction with applications, such as those used to create content in AR and/or otherwise used in AR (e.g., to perform activities in AR), products, accessories, services or a combination thereof. Artificial reality systems that provide artificial reality content can be implemented on a variety of platforms, including wearable displays such as HMDs connected to a host computer system, standalone HMDs, tablet-style near-eye displays with glasses, mobile devices or computing systems, or Any other hardware platform capable of providing artificial reality content to one or more observers.

The scope of the present disclosure is not limited by the particular embodiments described herein. Indeed, various other embodiments and modifications, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description and drawings. Accordingly, such other embodiments and modifications are intended to be within the scope of this disclosure. Additionally, although the disclosure has been described herein for a specific purpose in the context of a particular implementation in a particular environment, those of ordinary skill in the art will recognize that its validity is not limited thereto and that the disclosure may be derived from Any number of objects are beneficially implemented in any number of environments. Accordingly, the claims set forth below should be construed in view of the full scope and spirit of the disclosure as described herein.

100: waveguide illuminator 101: Base 106: Input waveguide 108: Input beam 110: light source 112: waveguide splitter 114: sub-beam 116: waveguide array 119: column 120: output coupler 122: sub-beam part 129: end 200: display device 201: light source 202: display panel 204: liquid crystal layer 214: light 220: display pixels 220A: display pixels 220B: display pixels 226: Human eye window 228: Linear polarizer 230: eye lens 250: controller 280: eyes 300: Optical Interference Pattern 302: retina 320A: Optical path 320B: light path 328A: Image 328B: Image 380: Cornea 400A: Waveguide illuminator 400B: Waveguide illuminator 401: base 406: first input waveguide 407: second input waveguide 408: The first input beam 409: Second input beam 410: The first light source 411: Second light source 412: The first waveguide splitter 413: Second waveguide splitter 414: the first plurality of sub-beams 415: the second plurality of sub-beams 416: The first waveguide 417: Waveguide 420: output coupler 421: output coupler 422: part 423: part 450: controller 477: light source beam splitter 478: Auxiliary waveguide 500: specific examples 600: Space variant polarizer 601: section 602: segment 700: Spatial variant polarizer 710: Uniform Linear Polarizer 720:Space variant wave plate 721: section 722: section 800: Image 801: the first sub-image 802: Second sub-image 820: pixels 821: pixels 822: pixels 830: pixels 831: pixel 832: pixels 900:Virtual reality near-eye display 901: frame 902: light source 906: Waveguide illuminator 918: display panel 926: Human eye window 932: eye lens 942:eye tracking camera 962: Human eye window illuminator 1000:HMD 1002: front body 1004: strip 1006: side 1008: Locator 1010: Inertial measurement unit 1011:Depth camera assembly 1012: Position sensor 1014:Eye Tracking System 1080: display system

Illustrative specific examples will be described in conjunction with the drawings, in which: [Fig. 1] is a schematic plan view of the waveguide illuminator disclosed in the present disclosure; [Fig. 2] is a schematic diagram of a display device using the waveguide illuminator of Fig. 1; [ FIG. 3 ] is an enlarged view of the display device of FIG. 2 , illustrating optical interference between adjacent pixels on the retina of the eye; [FIG. 4A] is a schematic plan view of an embodiment of a waveguide illuminator using two light sources and interleaved waveguides; [FIG. 4B] is a schematic plan view of a specific example of a waveguide illuminator using a light source, a beam splitter, and an interleaved waveguide; [ FIG. 5 ] is an enlarged front view of a specific example of the display device of FIG. 2 , showing the relative arrangement of grating output couplers and display panel pixels; [ FIG. 6 ] is a plan view of a spatially varying polarizer comprising a checkerboard pattern of orthogonally oriented linear polarizer segments for use in a waveguide illuminator of the present disclosure; [FIGS. 7A and 7B] Plan and side views, respectively, of embodiments of spatially variable polarizers for use in waveguide illuminators of the present disclosure, including linear polarizers followed by a checkerboard pattern of waveplates; [ FIG. 8 ] is a three-dimensional diagram illustrating the principle of interlaced sub-images for interference reduction; [ FIG. 9 ] is a view of an augmented reality (AR) display of the present disclosure in the form of a pair of glasses; and [ FIG. 10 ] is a three-dimensional view of the head-mounted display (HMD) of the present disclosure.

400A: Waveguide illuminator

401: base

406: first input waveguide

407: second input waveguide

408: The first input beam

409: Second input beam

410: The first light source

411: Second light source

412: The first waveguide splitter

413: Second waveguide splitter

414: the first plurality of sub-beams

415: the second plurality of sub-beams

416: The first waveguide

417: Waveguide

420: output coupler

421: output coupler

422: part

423: part

450: controller

Claims (20)

A waveguide illuminator comprising: first and second waveguide beam splitters configured to receive first and second light beams, respectively, for splitting the first and second light beams into first and second pluralities of sub-beams, respectively; first and second waveguide arrays, which are respectively coupled to the first and second waveguide beam splitters, and configured to propagate sub-beams of the first and second plurality of sub-beams, respectively, wherein the first and second waveguide arrays the waveguides are interleaved and run parallel to each other; and an array of output couplers in columns, each column of output couplers in the array coupled to a waveguide in the first or second waveguide array along the length of the waveguide for forming the first and second plurality of The interleaving of the beams outputs a two-dimensional array of coupled sub-beam portions. The waveguide illuminator of claim 1, wherein the first and second waveguide arrays are coupled to the first and second waveguide splitters at opposite ends of the first and second waveguide arrays, such that the first and second These sub-beams of the two plurality of sub-beams counter-propagate in respective waveguide arrays. The waveguide illuminator of claim 1, wherein output couplers of adjacent columns of said output couplers are offset relative to each other in a direction along the waveguides of said first and second waveguide arrays to form a diamond-shaped array the output coupler. The waveguide illuminator as claimed in claim 1, further comprising a first light source respectively coupled to the first and second waveguide splitters for providing the first and second light beams to the first and second waveguide splitters. and a second semiconductor light source. The waveguide illuminator according to claim 4, wherein the first and second semiconductor light sources are configured to emit light of different wavelengths in the same color channel. The waveguide illuminator according to claim 4, wherein the first and second semiconductor light sources include laser diodes with different emission wavelengths. The waveguide illuminator according to claim 4, further comprising a controller coupled to the first and second semiconductor light sources and configured to alternately operate the first and second semiconductor light sources in a time-sequential manner. A display device comprising: a display panel comprising a two-dimensional pixel array; and A waveguide illuminator configured to illuminate the display panel and comprising: a waveguide beam splitter configured to receive a light beam and split the light beam into a plurality of sub-beams; a waveguide array coupled to the waveguide splitter and configured to propagate the sub-beams therein, the waveguides of the waveguide array running parallel to each other; and an array of output couplers in columns, each column of output couplers in the array coupled to a waveguide in the waveguide array along the length of the waveguide for forming a two-dimensional array of outcoupled sub-beam portions; and A spatially variant polarizer disposed downstream of the display panel and configured to propagate outcoupled beamlet portions of a first polarization state and block outcoupled adjacent beamlet portions of a second orthogonal polarization state. The display device of claim 8, wherein the spatially variant polarizer comprises transversely joined linear polarizer segments oriented orthogonally to polarization transfer axes. The display device according to claim 9, wherein the linear polarizer segments with the same polarization direction are arranged in a checkerboard pattern. The display device according to claim 8, wherein the spatially variable polarizer includes a linear polarizer and a spatially variable wave plate downstream of the linear polarizer, and the spatially variable wave plate includes transverse directions of different optical axis directions arranged in a checkerboard pattern Bonded corrugated plate sections. The display device according to claim 11, wherein the wave plate segments in the same optical axis direction are arranged in a checkerboard pattern. A display device comprising: a display panel comprising a two-dimensional pixel array; and A waveguide illuminator configured to illuminate the display panel and comprising: a waveguide beam splitter configured to receive a light beam and split the light beam into a plurality of sub-beams; a waveguide array coupled to the waveguide splitter and configured to propagate the sub-beams therein, the waveguides of the waveguide array running parallel to each other; and an array of output couplers in columns, each column of output couplers in the array coupled to a waveguide in the waveguide array along the length of the waveguide for forming an output corresponding to the two-dimensional pixel array of the display panel Two-dimensional array of coupled sub-beam sections. The display device of claim 13, further comprising a controller operatively coupled to the display panel and configured to cause the display panel to display a plurality of sub-images in a time-sequential manner, the sub-images summed up for future use The displayed image. The display device according to claim 14, wherein pixels of different sub-images of the plurality of sub-images are interlaced. The display device according to claim 15, wherein pixels of different sub-images of the plurality of sub-images are arranged in a complementary checkerboard pattern. The display device according to claim 15, wherein the plurality of sub-images includes a first sub-image and a second sub-image with interlaced pixels such that each pixel in the first sub-image has at least two phases of the second sub-image neighboring pixels. The display device according to claim 17, wherein each pixel in the first sub-image has at least three adjacent pixels of the second sub-image. The display device according to claim 14, wherein the display panel comprises a transmissive light valve array. The display device according to claim 19, wherein the display panel includes a liquid crystal layer.

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