CN115151855A

CN115151855A - Pupil expander with improved color uniformity

Info

Publication number: CN115151855A
Application number: CN202180016500.2A
Authority: CN
Inventors: J·K·T·特沃; A·J·特沃南; H·J·赫瓦里南
Original assignee: Microsoft Technology Licensing LLC
Current assignee: Microsoft Technology Licensing LLC
Priority date: 2020-02-24
Filing date: 2021-01-20
Publication date: 2022-10-04
Also published as: EP4111252A1; WO2021173253A1

Abstract

The optical waveguide includes one or more upstream diffraction gratings in addition to the overlapping first and second downstream diffraction gratings. The one or more upstream diffraction gratings include a first upstream diffraction grating configured to receive display light and release display light that expands along a first axis. The first downstream diffraction grating and the second downstream diffraction grating are configured to receive display light expanding along the first axis and to cooperatively release display light further expanding along the second axis. The first downstream diffraction grating is disposed on a plane of the optical waveguide and is further configured to further expand the display light expanded along the first axis.

Description

Pupil expander with improved color uniformity

Background

In recent years, near-eye display technology has evolved from a small audience to an emerging consumer technology. For example, in head mounted display devices, near-eye display systems provide 3D stereoscopic vision for virtual reality presentations. Typically, the objective optics of a near-eye display system are configured to transmit a display image through an area that is too small to be reliably aligned with the user's pupil. Accordingly, the associated eyepiece optics of the near-eye display system may include some form of pupil expander. The pupil expander expands the displayed image over a larger area, for example, over the entire area where the user's pupil may be found. Some pupil expanders include an optical waveguide that supports one or more diffraction gratings. The diffraction grating couples the display image into and out of the waveguide and provides the desired pupil expansion function.

Disclosure of Invention

The present disclosure relates to an optical waveguide that includes one or more upstream diffraction gratings in addition to overlapping first and second downstream diffraction gratings. The one or more upstream diffraction gratings include a first upstream diffraction grating configured to receive display light and release display light that expands along a first axis. The first downstream diffraction grating and the second downstream diffraction grating are configured to receive display light expanding along the first axis and to cooperatively release display light further expanding along the second axis. The first downstream diffraction grating is disposed on a plane of the optical waveguide and is further configured to further expand the display light expanded along the first axis.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

Drawings

FIG. 1 illustrates various aspects of an example near-eye display system.

Fig. 2A-2D illustrate various aspects of an example pupil expander that includes an optical waveguide.

Fig. 3 is an example overlay of outcoupling intensity versus distance across the optical waveguide of the pupil expander of fig. 2 for three different colors of visible light.

Fig. 4A-8D illustrate various aspects of an example pupil expander that includes an optical waveguide configured to reduce color non-uniformity in an exit pupil.

FIG. 9 illustrates aspects of an example implementation environment for a near-eye display system.

Fig. 10 illustrates further aspects of an example near-eye display system.

Fig. 11A and 11B illustrate the effect of stereoscopic parallax on virtual image display in an example near-eye display system.

Detailed Description

As described above, an optical waveguide supporting an in-coupling diffraction grating and an out-coupling diffraction grating may provide pupil expansion in a near-eye display system. However, some pupil expansion waveguides may cause unwanted variations in the intensity ratio of the component wavelengths passing through the exit pupil, resulting in color non-uniformity in the expanded display image. Accordingly, the image color may vary depending on the exit pupil area where the display image is observed. The non-uniformity of color can be particularly pronounced for light guides that sequentially expand the displayed image along orthogonal or near orthogonal axes. As disclosed in more detail herein, color non-uniformity is significantly reduced in the waveguide, with the display image expansion of the second stage being in a direction diagonally opposite to the image expansion of the first stage. This display image expansion method may be implemented in an optical waveguide supporting crossed diffraction gratings, for example, diffraction gratings that overlap in the area of the expanded display image released from the optical waveguide.

The present disclosure illustrates by way of example and with reference to the accompanying drawings a series of pupil dilation waveguides. Components, process steps, and other elements that may be substantially the same in one or more figures are identified coordinately and are described with minimal repetition. However, it should be noted that the elements identified by reconciliation may also differ to some extent. It is further noted that the figures are schematic and are generally not drawn to scale. Rather, the various drawing scales, aspect ratios, and numbers of components shown in the figures may be purposely distorted to make certain features or relationships easier to see.

Fig. 1 illustrates various aspects of an example near-eye display system 110. The near-eye display system is configured to present still or moving images for viewing by a human observer, i.e. performed by a user of the near-eye display system. Some aspects of the near-eye display system 110 may vary from example to example. In the illustrated example, the near-eye display system is part of a virtual reality or mixed reality system that displays a computer-generated image in the field of view of an observer. In other examples, the near-eye display system may be part of a microscope, telescope, binoculars, or other optical system. In general, near-eye display system 110 includes objective optics 112 that form and/or collect a display image and eyepiece optics 114 that present the display image to a viewer. The following description focuses immediately on eyepiece optics, and example objective optics will be described after this description.

In near-eye display system 110, display light from objective optics 112 passes through a physical aperture 116 of limited size. As shown in fig. 1, the size of the physical aperture may correspond to the diameter of a collection lens 118 disposed on a pixel array 120 of the display projector. For example, the pixel array may comprise a Spatial Light Modulator (SLM) or an organic light emitting diode array. Various other target optical configurations are also contemplated. The focusing optics 122 may be configured to focus the display light to an anatomical pupil location of the viewer. In doing so, the focusing optics direct the display light through an entrance pupil 124, which is defined as the image of the physical aperture 116 at the anatomical pupil location.

Due to the small size of the physical aperture 116 and/or due to other features of the near-eye display system 110, the entrance pupil 124 may be very small. In examples where objective optics 112 includes an SLM or OLED projection assembly, entrance pupil 124 may be 3 millimeters in diameter or less. It is very difficult to maintain alignment between entrance pupils of this size and anatomical pupils. When entrance pupil 124 does not fill the viewer's anatomical pupil, the viewer may perceive a dark or vignetted displayed image, or no image at all. Accordingly, near-eye display system 110 includes pupil expander 126. The pupil expander has an entrance face 134 and an exit face 136 that intersect the entrance pupil 124. The pupil expander is configured to receive display light through the entrance pupil and optically discharge the display light downstream on the expanded exit pupil 128.

In a conventional display viewing scenario, the exit pupil of the pupil expander may be large enough to cover the entire area where the observer's pupil may be present. Such regions are referred to herein as "eye movement ranges," such as eye movement range 130 in fig. 1.

Fig. 2A-2D illustrate other aspects of pupil expander 126 in one non-limiting example. The pupil expander includes an optical waveguide 232 in the form of a transparent (e.g., glass or polymer) plate. The optical waveguide has opposing planar faces, an entrance face 234 and an exit face 236. Fig. 2A provides a plan view of the entrance face 234, while the view of the exit face 236 in fig. 2B is seen through the entrance face. This rendering is repeatedly chosen in subsequent figures so that the reader can more easily visualize the overlap between the diffraction gratings (see below) arranged on the entrance and exit faces. Fig. 2C and 2D show a diffraction grating providing perspective views of two different rotations of the optical waveguide about a horizontal axis aligned with the front edge.

The light guide includes an entrance area 238 through which the display light is received and an exit area 240 through which the display light is optically discharged downstream through the exit area 236. In a normal operating scenario, display light is received from the objective optic zone 112 and released into the eye movement range 230. The light guide 232 also includes an initial expansion region 242 that receives display light from the entrance region 238 and expands the display light en route to the exit region 240.

The optical waveguide 232 includes a plurality of differently configured diffraction gratings distributed between the entrance zone 238, the exit zone 240, and the initial expansion zone 242. The diffraction grating is arranged on the entrance face 234 and/or the exit face 236. The type of diffraction grating used in the optical waveguide 232 is not particularly limited. In some examples, a surface relief type diffraction grating may be used. Such a grating may comprise a series of closely spaced channels formed in a support surface. In other examples, a volume grating or an index modulated diffraction grating may be used.

Each optical waveguide disclosed herein includes one or more "upstream" diffraction gratings configured to direct display light onto at least one "downstream" diffraction grating. In an example where the display light from the incident region 238 initially expands in opposite directions, the upstream diffraction grating includes a right-side expansion grating 244R and a left-side expansion grating 244L. In each drawing, directions "right" and "left" are assigned from the perspective of a user of the near-eye display device, i.e., viewing the exit face of the optical waveguide. In the particular example of fig. 2A-D, the right expansion grating is disposed on the entrance face 234 and the left expansion grating is disposed on the exit face 236, both expansion gratings passing through the initial expansion region 242 and overlapping at the entrance region 238. Here, a downstream outcoupling grating 246 is arranged on the entrance face 234 of the exit area 240. In other examples, any, some, or all of the diffraction gratings listed above may be arranged on opposite sides of the optical waveguide relative to the configuration shown.

In the incident region 238 of the optical waveguide 232, the low-angle display light from the objective optical 112 is received through the incident surface 234. In this example, the right and left

expansion gratings

244R and 244L are each configured to couple display light into an optical waveguide. The left-side expansion grating 244L diffracts some of the display light at supercritical angles downward and rightward so that it now propagates by Total Internal Reflection (TIR) from the entrance and exit faces 234, 236 through the optical waveguide rightward and downward. On each reflection from the entrance face, the propagating light encounters the right expansion grating 244R, which directly diffracts a portion of the light downward. For clarity of illustration, only a few of the downwardly diffracted rays are shown in the drawings.

The interaction with the right-side expansion grating 244R expands the display light to the right and guides the display light expanded to the right to the exit area 240. In addition, the right-side expansion grating diffracts some of the incident display light at supercritical angles down and left, such that it now propagates through the optical waveguide by TIR, but in the down and left directions. The interaction with the left-side expansion grating 244L expands the display light to the left and guides the display light expanded to the left to the exit region. In effect, the right and left expansion gratings receive display light and release display light that expands in opposite directions along the X axis. Thus, the display light is released with substantially uniform intensity on the right and left expansion gratings, the intensity of each grating being configured to gradually change with the distance of the grating, i.e., the intensity of the right expansion grating 244R increases to the right and the intensity of the left expansion grating 244L increases to the left.

In the exit area 240, the display light propagating on each reflection from the entrance face 234 encounters the outcoupling grating 246. The outcoupling grating diffracts the rightward and leftward expanding portions of the display light out of the optical waveguide 232 towards the eye-movement range 230. For clarity of illustration, only a few outcoupled rays are shown in the figure. In this way the display light is expanded in the downward direction, i.e. perpendicular to the right and left expansion effected by the right and left expansion gratings. In effect, the outcoupling grating receives display light that extends along the X-axis and releases display light that extends further along the Y-axis. Thus, the display light is released with a substantially uniform intensity along the outcoupling grating, the intensity of which is configured to gradually increase in the negative Y-direction. This strategy is generally applicable to diffraction gratings that provide pupil dilation.

Primarily to aid in understanding the drawings, the description herein refers to the directions "right", "left", "upper", "lower", etc. These directions should be understood in a relative sense as the display system disclosed herein may be used in any absolute direction. Furthermore, for optical components with rotational and/or mirror symmetry, the directions "right" and "left" or "up" and "down" may be interchanged throughout the description. However, since the field of view of the human eye system is naturally larger in the horizontal direction than in the vertical direction, some optical components may be optimized to provide a larger pupil expansion in the horizontal direction than in the vertical direction. Thus, in some implementations, the "right" and "left" directions are intended to be relative to the user and parallel to a cross-section of the user, which corresponds to the optical horizontal X-axis in the figures. Also, in some implementations, the "up" and "down" directions are intended to be relative to the user and parallel to the sagittal plane of the user, which corresponds to the optical vertical Y axis in the drawing figures.

In some cases, the configuration of the diffraction grating in the optical waveguide may result in undesirable color non-uniformities in the expanded display image, for example, in the horizontal expansion direction. Fig. 3 illustrates the effect observed in a simplified example, where white light of uniform intensity is imaged onto the entrance pupil of the optical waveguide, as shown in fig. 2A-D. These figures show the outcoupling intensity of three different colors of light with respect to the distance across the exit pupil. Here, the downward-propagating pupil-replicating beam observes peaks at different positions, depending on the color. The variation between the red, green and blue intensities indicates the non-uniformity of the color. Since the peak distribution is located at the exit face of the optical waveguide, the observed pattern varies depending on the position of the observer's eye. Therefore, the effect cannot be compensated for by color correction of the display image content.

Without tying all aspects of the disclosure to any particular theory, the ribbon may be explained as follows. The output image of the pupil expander is located almost at an "infinite" distance, so each pixel of the display image corresponds to a particular ray angle; the different wavelengths have the same exit angle because the sum of the diffraction from all the gratings in the optical path is zero (see below). However, due to chromatic dispersion, the sawtooth angle within the optical waveguide is wavelength dependent. Thus, when the beam (corresponding to a single image angle/pixel propagation pupil) is split upon reaching the expansion grating, expansion occurs. This occurs at different wavelength dependent positions and so the out-coupled copies of the exit pupil occur at different wavelength dependent positions. This results in the intensity ratio of the outcoupled copies varying with output position. Accordingly, the observer perceives color unevenness depending on his or her eye position.

Fig. 4A-4D illustrate various aspects of pupil expander 126 in another non-limiting example. In the optical waveguide 432, two different downstream diffraction gratings are arranged in the exit region 440: the right outcoupling grating 446R is arranged on the incident surface 434, and the left outcoupling grating 446L is arranged on the exit surface 436. The right and left outcoupling gratings overlap in the exit area 440 as do the right and left

expansion gratings

444R and 444L in the entrance area 438. Naturally, the "overlap" of two or more diffraction gratings may be identified from an angle orthogonal to the one or more optical waveguide faces on which the diffraction gratings are located. In the example of fig. 4A-4D, display light propagating through the exit region 440 encounters the right outcoupling grating 446R each time it is reflected from the entrance face 434 and the left outcoupling grating 446L each time it is reflected from the exit face 436. The right and left outcoupling gratings diffract the right and left expanding portions of the display light out of the light guide 432 and towards the eye-movement range 430, thereby expanding the display light downwards, as shown in the previous example. However, the outcoupling function in the optical waveguide 432 differs from the previous example in several important respects.

One difference is that the right and left outcoupling gratings of the optical waveguide 432 also provide additional right and left directional (i.e., horizontal) expansion. Accordingly, the right and left outcoupling gratings are further expanded in opposite directions along the X-axis, showing that the light is expanded along the X-axis. The additional horizontal spreading means that the light rays do not propagate in a single direction in the outcoupling region, but change their direction, thereby eliminating the above-described wavelength-dependent viewing position of the light guide 232. Upon each reflection from the exit surface 436, such light encounters the left outcoupling grating 446L, which is configured to release display light oriented rightward from the light guide. Conversely, diffraction of the downward propagating display light by the left-side outcoupling grating 446L redirects the propagating display light obliquely to the left; upon each reflection from the entrance face 434, the light encounters the right out-coupling grating 446R, which is configured to release display light to the left from the light guide. In effect, the right and left outcoupling gratings receive display light expanding along the X-axis and cooperatively release display light further expanding along the Y-axis from the light guide by successive diffractions from the first and second downstream diffraction gratings. It should be noted that the pupil expansion directions affected by the upstream diffraction grating and the downstream diffraction grating may be mutually inclined. Accordingly, successive expansion phases "in opposite directions along an axis" merely indicate that, once an axis is selected, the direction of the second expansion projected onto that axis is opposite to the direction of the first expansion projected onto the same axis.

Although the above-described pupil expander includes separate right and left expansion gratings in the initial expansion zone, this aspect is not strictly necessary. In implementations that allow for a narrower horizontal field of view, the entrance pupil may be extended in only one horizontal direction and one vertical direction. Fig. 5A-5B illustrate various aspects of a pupil expander based on an optical waveguide 532 configured in this manner.

The optical waveguide 532 includes a dedicated incoupling grating 548 arranged in the entrance region 538. The incoupling grating diffracts display light to the right at a supercritical angle such that it propagates through the optical waveguide 532 towards the initial expansion region 542. In the initial expansion region, the propagating light encounters the right expansion grating 544R upon each reflection from the entrance face 534. The right expansion grating diffracts a portion of this light down towards the exit area 540. This operation expands the display light to the right and guides the display light expanded to the right to the exit area. Display light propagating through the exit region 540 encounters the right outcoupling grating 546R each time it is reflected from the entrance face 534 and the left outcoupling grating 546L each time it is reflected from the exit face 536. Cooperatively, via successive diffractions from the right and left outcoupling gratings, the rightward and leftward expanded portions of the display light are diffracted out of the light guide 532 and toward the eye movement range, thereby expanding the display light downward. In this example, the right and left outcoupling gratings provide additional right and left expansion, which, as described above, prevent color banding in the exit pupil. In this and other configurations, at least one downstream outcoupling grating expands the display light in opposite directions along the X-axis relative to the expansion direction affected by the upstream expansion grating. As shown in fig. 5, a downstream outcoupling grating that expands the display light in the opposite direction may be arranged on the opposite side of the waveguide with respect to the upstream expansion grating. In other examples, the upstream extension grating and the downstream outcoupling grating may be arranged on the same face.

The optical waveguide shown in fig. 4A to 4D and 5A to 5B includes a right-side extension grating and a right-side outcoupling grating, which may be arranged on the same face of the optical waveguide; the optical waveguide shown in fig. 4A-D also comprises a left side expansion grating and a left side outcoupling grating, which may likewise be arranged on the same plane. In these examples, the orientation and/or spacing of the respective horizontal spreading and outcoupling gratings may be equal for ease of manufacturing. However, this feature is not necessary. In other examples, the orientation and/or pitch of the respective horizontal extension and outcoupling gratings may be different even for gratings arranged on the same face of the optical waveguide. Fig. 6 and 7 illustrate these variations. As shown in the figure, each of the outcoupling gratings 646R, 646L, and 746R has a narrower pitch than the

corresponding expansion gratings

644R, 644L, and 744R, respectively, which are arranged on the same plane. Furthermore, each outcoupling grating in fig. 6 and 7 differs in orientation from its corresponding extension grating. More generally, any combination of gratings that obey the proper grating vector summation rules will provide the proper function in the outcoupling region. In short, each diffraction grating i through which display light passes may be represented by a wave vector D _i And (5) characterizing. In this form, the required outcoupling condition is that the sum of the wave vectors of all such gratings is zero. The raster vector summation rule is further described in U.S. patent No. 10241346 to Tervo.

Based on the above principles, the orientation and pitch of the individual outcoupling gratings can be optimized independently of the orientation or pitch of the corresponding horizontally extending gratings, even in configurations in which the corresponding gratings occupy the same face of the optical waveguide. This provides the advantage of flexibility in the overall configuration of the optical system, as any diffraction grating on a given face relative to the optical waveguide is constrained to a configuration having the same orientation and/or spacing. The ability to form and precisely position multiple diffraction gratings on the same face of a waveguide that differ in orientation and/or spacing is a result of improved manufacturing. Accordingly, a plurality of discontinuous gratings that differ in orientation and/or spacing may be disposed on the entrance and/or exit faces of the optical waveguides disclosed herein.

Figures 8A-8D illustrate various aspects of pupil expander 126 in another non-limiting example. Optical waveguide 832 includes a dedicated incoupling grating 848 disposed in the entry region 838. As shown, the incoupling grating is disposed on the entrance face 834 of the optical waveguide 832 together with the right extension grating 844R and the right outcoupling grating 846R. Also, any, some or all of the diffraction gratings listed above may be disposed on opposite sides of the optical waveguide relative to the configuration shown. As in the examples shown in fig. 5 and 7. The incoupling grating is an upstream diffraction grating that couples the display light into the optical waveguide and guides the display light to a suitable upstream expansion grating. In particular, the incoupling grating 848 diffracts the display light to a supercritical angle at which the display light may interact with the right expansion grating 844R each time it is reflected from the entrance face 834 or with the left expansion grating 844L each time it is reflected from the exit face 836. The left expansion grating 844L diffracts light from the incoupling grating obliquely right and downward. Each time it is reflected from the entrance face, the right expansion grating 844R directly diffracts a portion of that light down toward the exit region 840. This operation expands the display light to the right and guides the display light expanded to the right downward toward the exit area. Conversely, the right expansion grating 844R diffracts light from the incoupling grating obliquely to the left and downward. On each reflection from the exit surface, the left-hand expansion grating diffracts a portion of this light directly down toward the exit region 840. As described above, in the exit area, the display light is expanded downward and released into the eye movement range 830.

It has been noted in the above description that diffraction gratings configured for incoupling, outcoupling and/or initial expansion may generally be arranged on the entrance or exit face of the optical waveguide. Accordingly, almost any diffraction grating described above can be relocated to a corresponding region of the opposite face of the optical waveguide without loss of functionality. Repositioning can be envisaged even if there are already differently configured diffraction gratings in respective regions of the opposing faces, as a plurality of diffraction gratings differing in orientation may occupy the same region of a given face. Furthermore, overlapping gratings of the same or different configurations may be arranged on the entrance and exit faces to cooperatively achieve any desired diffractive function on the display light propagating through the waveguide. Such diffractive functions may include, for example, incoupling, spreading in one or more directions, and outcoupling.

Fig. 9 illustrates aspects of an example implementation environment for a near-eye display system 910. As shown herein, the near-eye display system may be a component of the wearable electronic device 950 worn and operated by the user 952. The near-eye display system of fig. 9 is configured to present a virtual image in a field of view of a user. In some implementations, a user input component of the wearable electronic device may cause a user to interact with the virtual image. In the example of fig. 9, wearable electronic device 950 takes the form of eyeglasses. In other examples, the wearable electronic device may take the form of a visor, helmet, or face mask. In other examples, the near-eye display system may be a component of a non-wearable electronic device.

The near-eye display system 910 may be configured to cover one or both eyes of the user 952, and may be adapted for monocular or binocular image display. In examples where the near-eye display system covers only one eye but requires binocular image display, a complementary near-eye display system may be disposed on the other eye. In examples where the near-eye display system covers the eyes simultaneously and requires binocular image display, the virtual image presented by the near-eye display system 910 may be divided into right and left portions directed to the right and left eyes, respectively. In scenes where stereoscopic image display is desired, virtual images from the right and left portions or a complementary near-eye display system may be configured with appropriate stereoscopic parallax (see below) to render a three-dimensional object or scene.

Fig. 10 illustrates additional aspects of an example near-eye display system. Near-eye display system 1010 includes upstream optics in the form of a display projector 1054, display projector 1054 configured to emit display light. The display projector of fig. 10 includes a high-resolution Spatial Light Modulator (SLM) 1056 illuminated by one or more light emitters 1058. The light emitter may comprise a Light Emitting Diode (LED) or a laser diode, and the SLM may comprise, for example, a Liquid Crystal On Silicon (LCOS) or a digital micromirror array. The light emitters of the SLM and the display projector are operatively coupled to a display controller 1060. The display controller controls the matrix of individual, light-oriented pixel elements of the SLM to cause the SLM to modulate light received from the light emitters to form the desired display image. By controlling the light modulation in time and space, the display controller can cause the display projector to project a synchronized sequence of display images (i.e., video). In the example shown in fig. 10, the display image is formed from reflections from the SLM. In other examples, the display image may be formed by transmission through a suitably configured transmissive SLM. Display projectors based on other technologies are also envisaged, such as organic LED arrays, raster scanned laser beams, etc.

Near-to-eye display system 1010 includes at least one pupil expander 1026 configured to receive display light from display projector 1054. Display light is received via in-coupling grating 1048 and released into eye range 1030 via out-coupling grating 1044. Each display image formed by the near-eye display system is a predetermined distance Z presented in front of the observer O ₀ A virtual image of (c). The distance Z ₀ Also referred to as the "focal plane depth" of the displayed image. In some near-eye display configurations, Z ₀ Is a fixed function of the design parameters of the display projector 1054, which includes a fixed eyepiece lens 1068. Based on the permanent configuration of these structures, the focal plane may be positioned at a desired depth at infinity, 300 centimeters (cm), or 200 cm.

Stereoscopic near-eye display systems employing fixed focal planes may present a perceived virtual display image at a controlled variable distance in front of or behind the fixed focal planes. This effect can be achieved by controlling the horizontal disparity of corresponding pixels of each pair of left and right stereoscopic images. May also be used to impart three-dimensionality to the virtual display image, as will be understood with reference to fig. 11A and 11B.

For illustrative purposes, fig. 11A shows a right image frame 1162R and a left image frame 1162L superimposed on each other. The right image frame surrounds the right display image 1164R, and the left image frame surrounds the left display image 1164L. The right-side display image and the left-side display image may be presented to the viewer as virtual images by simultaneous viewing by the stereoscopic near-eye display device. In the example of FIG. 11A, the virtual image presents a visual surface of an individual rendered trace.

Referring to fig. 11B, each locus i of the visible surface has each pixel (X) of the left and right display images _i ，Y _i ) Associated depth coordinate Z _i . The desired depth coordinate may be modeled as follows. First, a distance Z from a focal plane F of a stereoscopic near-eye display system is selected ₀ . As described above, the optical components of the stereoscopic near-eye display system may be configured to present each display image with a vergence appropriate for the selected distance. In one example, Z ₀ May be set to "infinity" such that each optical system presents a display image in the form of collimated light. In another example, Z ₀ May be set at 200cm and the optical system may present each display image in the form of divergent light. In some examples, Z may be selected at design time ₀ And remain unchanged for all virtual images presented by the display system. Alternatively, the optical system may be configured with electronically tunable optical power through the variable eyepiece lens 1070 of FIG. 10 to allow Z ₀ Dynamically varying according to the range of distances over which the virtual image is to be rendered.

Once the distance Z to the focal plane is established ₀ The depth coordinate Z of each trajectory i on the viewing surface can be set. This is achieved by adjusting the positional disparity of two pixels corresponding to the trajectory i in the left and right display images with respect to their respective image frames. In FIG. 11B, the pixel corresponding to the trajectory i in the right image frame is represented as R _i And the pixel corresponding to the left frame is denoted as L _i . In FIG. 11B, the positional disparity is positive, R _i At L in the superimposed image frame _i To the right of (a). A positive positional disparity results in the trajectory i appearing behind the focal plane F. If the positional disparity is negative, the trajectory will appear in front of the focal plane. Finally, if the right and left display images overlap (no disparity, R) _i And L _i Coincident), then the trajectory appears to lie directly on the focal plane. Without tying this disclosure to any particular theory, the positional disparity D may be related to Z, Z in the following manner ₀ In relation to the interpupillary distance (IPD) of the observer:

in the above-described method, the positional disparity that is attempted to be introduced between corresponding pixels of the left and right display images is "horizontal" disparity, i.e., disparity that is parallel to the interpupillary axis of the observer. The horizontal parallax component simulates the effect of real object depth on the human visual system where the images of real objects received by the right and left eyes are naturally offset parallel to the interpupillary axis.

In one implementation, logic in display controller 1060 maintains a cartesian space model in front of the observer in a reference frame fixed to near-eye display system 1010. The pupil position of the observer is mapped to this space, as are

image boxes

1162R and 1162L, each at a predetermined depth Z ₀ To (3). Then, a virtual image is constructed 1166, each trajectory i of the visible surface of the image having coordinates X in a common reference system _i 、Y _i And Z _i . For each trajectory of the viewing surface, two line segments are constructed-a first line segment to the pupil location of the viewer's right eye and a second line segment to the pupil location of the viewer's left eye. Pixel R of the right display image corresponding to the trajectory i _i Is considered to be the intersection of the first line segment in the right image frame 1164R. Likewise, the pixel L of the left display image _i Is considered to be the intersection of the second line segment in the left image frame 1164L. The process automatically provides the appropriate amount of shift and zoom to properly render the visible surface, placing each trajectory i at the appropriate distance and at the appropriate perspective angle. In some examples, the above method may be facilitated by estimating the observer's pupil position in real time. In examples where no pupil estimation is attempted, suitable alternatives for the pupil location may be used, such as the center of rotation of the pupil location or the eyeball location.

The three-dimensional display rendering may be bound to a computer of one or more computing devices, such as the display controller 1060 of FIG. 10. The method may be implemented as an application or service, an Application Programming Interface (API), a library, and/or other computer program product

Display controller 1060 includes a logic system and a computer storage system. Display controller 1060 may optionally include an input system, a communication system, and/or other systems not shown in the figures.

The logic system includes one or more physical devices configured to execute instructions. For example, the logic system may be configured to execute instructions that are part of at least one Operating System (OS), application program, service, and/or other program construct. The logic system may include at least one hardware processor (e.g., a microprocessor, central Processing Unit (CPU), and/or Graphics Processing Unit (GPU)) configured to execute software instructions. Additionally or alternatively, the logic system may include at least one hardware or firmware device configured to execute hardware or firmware instructions. The processors of the logic system may be single-core or multi-core, and the instructions executed thereon may be configured for serial, parallel, and/or distributed processing. Individual components of the logic system may optionally be distributed between two or more separate devices, which may be remotely located and/or configured to coordinate the processes. Various aspects of the logic system may be virtualized and executed by remotely accessible network computing devices configured in a cloud computing configuration.

The computer memory system includes at least one physical device configured to temporarily and/or permanently retain computer information, such as data and instructions executable by the logic system. When a computer storage system includes two or more devices, the devices may be collocated or remotely located. The computer storage system may include at least one volatile, non-volatile, dynamic, static, read/write, read-only, random-access, sequential-access, location-addressable, file-addressable, and/or content-addressable computer storage device. The computer storage system may include at least one removable and/or built-in computer storage device. When the logic system executes instructions, the state of the computer storage system may be transformed, for example, to hold different data.

Various aspects of the logic system and computer storage system may be integrated into one or more hardware logic components. For example, any such hardware logic components may include at least one program or application specific integrated circuit (PASIC/ASIC), program or application specific standard product (PSSP/ASSP), system on a chip (SOC), or Complex Programmable Logic Device (CPLD).

The logic system and the computer storage system may cooperate to instantiate one or more logic machines or engines. As used herein, the terms "machine" and "engine" are each collectively referred to as a combination of coordinated hardware, firmware, software, instructions, and/or any other component that provides computer functionality. In other words, neither the machine nor the engine is ever an abstract concept, always in a tangible form. A machine or engine may be instantiated by a single computing device, or a machine or engine may include two or more subcomponents instantiated by two or more different computing devices. In some implementations, the machine or engine includes a local component (e.g., a software application executed by a computer processor) that cooperates with a remote component (e.g., a cloud computing service provided by a network of one or more server computers). Software and/or other instructions that impart functionality to a particular machine or engine may optionally be stored as one or more non-executed modules on one or more computer storage devices.

When included, the input system may include or be connected to one or more input devices. The input device may comprise a sensor device or a user input device. Examples of user input devices include a keyboard, mouse, touch screen, and/or machine vision system configured for gesture recognition. When included, the communication system may be configured to communicatively couple the display controller 1060 with one or more other computers. The communication system may include wired and/or wireless communication devices compatible with one or more different communication protocols. The communication system may be configured for communication via a personal, local area network and/or a wide area network.

One aspect of the present disclosure relates to an optical waveguide including one or more upstream diffraction gratings and overlapping first and second downstream diffraction gratings. The one or more upstream diffraction gratings include a first upstream diffraction grating configured to receive display light and release the display light that expands along a first axis. The overlapping first and second downstream diffraction gratings are configured to receive display light expanding along a first axis and to cooperatively release display light further expanding along a second axis. The first downstream diffraction grating is disposed on a plane of the optical waveguide and is configured to further expand the display light expanded along the first axis.

In some implementations, at least one of the one or more upstream diffraction gratings is arranged on a plane. In some implementations, the first downstream diffraction grating is directionally different from at least one of the one or more upstream diffraction gratings arranged on the plane. In some implementations, the first downstream diffraction grating is different in pitch than at least one of the one or more upstream diffraction gratings arranged on the plane. In some implementations, the first downstream diffraction grating is discontinuous with at least one of the one or more upstream diffraction gratings disposed on the plane. In some implementations, at least one of the one or more upstream diffraction gratings disposed on the plane includes a first upstream diffraction grating. In some implementations, the one or more upstream diffraction gratings include a second upstream diffraction grating configured to receive the display light and release the display light expanded along the first axis, and the first and second upstream diffraction gratings are configured to expand the display light in opposite directions along the first axis. In some implementations, the second downstream diffraction grating is configured to further expand the display light expanded along the first axis, and the first and second downstream diffraction gratings are configured to further expand the display light expanded along the first axis in opposite directions along the first axis. In some implementations, the first downstream diffraction grating and the second downstream diffraction grating are disposed on opposite sides of the optical waveguide. In some implementations, the first axis is an optical horizontal axis and the second axis is an optical vertical axis. In some implementations, the one or more upstream diffraction gratings include an incoupling diffraction grating configured to couple the display light into the optical waveguide, and the first upstream diffraction grating is configured to receive the display light from the incoupling diffraction grating. In some implementations, the first upstream diffraction grating is configured to couple display light into the optical waveguide. In some implementations, the first downstream diffraction grating and the second downstream diffraction grating are configured to cooperatively release display light from the optical waveguide that further expands along the first axis and the second axis via successive diffractions from the first downstream diffraction grating and the second downstream diffraction grating.

Another aspect of the invention relates to a near-eye display system that includes a display projector configured to direct display light through an entrance pupil, and an optical waveguide having a plane that intersects the entrance pupil. The optical waveguide includes one or more upstream diffraction gratings and first and second downstream diffraction gratings that overlap from an angle normal to the plane. The one or more upstream diffraction gratings include a first upstream diffraction grating configured to receive display light and release the display light that expands along a first axis. The first downstream diffraction grating and the second downstream diffraction grating are configured to receive display light expanding along a first axis and to cooperatively release display light further expanding along a second axis. The first downstream diffraction grating is disposed on a plane of the optical waveguide and is further configured to further expand the display light expanded along the first axis.

In some implementations, at least one of the one or more upstream diffraction gratings is arranged on a plane. In some implementations, the first downstream diffraction grating is different in orientation and/or spacing from at least one of the one or more upstream diffraction gratings disposed on the plane. In some implementations, the first downstream diffraction grating is discontinuous with at least one of the one or more upstream diffraction gratings disposed on the plane.

Another aspect of the present disclosure relates to an optical waveguide that includes an upstream diffraction grating and an overlapping downstream diffraction grating. The upstream diffraction grating is configured to receive display light and release the display light extending along a first axis. The overlapping downstream diffraction grating is configured to receive display light expanding along a first axis and to release display light further expanding along the first axis and a second axis via successive diffraction from the overlapping downstream diffraction grating. The overlapping downstream diffraction gratings are configured to spread the display light in opposite directions along a first axis.

In some implementations, the overlapping downstream diffraction gratings are disposed on opposite sides of the optical waveguide. In some implementations, the upstream diffraction grating and the at least one overlapping downstream diffraction grating are disposed on the same face of the optical waveguide, and the upstream diffraction grating is discontinuous with the at least one overlapping downstream diffraction grating.

It is to be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and/or described may be performed in the sequence illustrated and/or described, in other sequences, in parallel, or omitted. Also, the order of the above-described processes may be changed.

The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.

Claims

1. An optical waveguide, comprising:

one or more upstream diffraction gratings comprising a first upstream diffraction grating configured to receive display light and release the display light expanded along a first axis; and

overlapping first and second downstream diffraction gratings configured to receive the display light expanding along the first axis and to cooperatively release display light further expanding along a second axis,

wherein the first downstream diffraction grating is arranged on a plane of the optical waveguide and is further configured to further expand the display light expanded along the first axis.

2. The optical waveguide of claim 1, wherein at least one of the one or more upstream diffraction gratings is disposed on the plane.

3. The optical waveguide of claim 2, wherein the first downstream diffraction grating differs in orientation from the at least one of the one or more upstream diffraction gratings disposed on the plane.

4. The optical waveguide of claim 2, wherein the first downstream diffraction grating differs in pitch from the at least one of the one or more upstream diffraction gratings disposed on the plane.

5. The optical waveguide of claim 2, wherein the first downstream diffraction grating is discontinuous with the at least one of the one or more upstream diffraction gratings disposed on the plane.

6. The optical waveguide of claim 2, wherein the at least one of the one or more upstream diffraction gratings disposed on the plane comprises the first upstream diffraction grating.

7. The optical waveguide of claim 1, wherein the one or more upstream diffraction gratings comprise a second upstream diffraction grating configured to receive the display light and release the display light expanded along the first axis, wherein the first and second upstream diffraction gratings are configured to expand the display light in opposite directions along the first axis.

8. The optical waveguide of claim 1, wherein the second downstream diffraction grating is configured to further expand the display light expanded along the first axis, and wherein the first downstream diffraction grating and the second downstream diffraction grating are configured to further expand the display light expanded along the first axis in opposite directions along the first axis.

9. The optical waveguide of claim 1, wherein the first downstream diffraction grating and the second downstream diffraction grating are disposed on opposite sides of the optical waveguide.

10. The optical waveguide of claim 1, wherein the first axis is an optical horizontal axis and the second axis is an optical vertical axis.

11. The optical waveguide of claim 1, wherein the one or more upstream diffraction gratings comprise an incoupling diffraction grating configured to couple the display light into the optical waveguide, and wherein the first upstream diffraction grating is configured to receive the display light from the incoupling diffraction grating.

12. The optical waveguide of claim 1, wherein the first upstream diffraction grating is configured to couple the display light into the optical waveguide.

13. The optical waveguide of claim 1, wherein the first and second downstream diffraction gratings are configured to cooperatively release the display light from the optical waveguide via successive diffractions from the first and second downstream diffraction gratings that further expand along the first and second axes.

14. The optical waveguide of claim 1, wherein the optical waveguide is disposed in a near-eye display system.

15. The optical waveguide of claim 1, wherein the at least one of the one or more upstream diffraction gratings and at least one of the first and second downstream diffraction gratings are arranged on the same face of the optical waveguide, and wherein the at least one of the one or more upstream diffraction gratings is discontinuous with the at least one of the first and second downstream diffraction gratings.