Multiple depth plane three-dimensional display using a wave guide reflector array projector

A two-dimensional array of linear wave guides includes a plurality of 2D planar wave guide assemblies, columns, sets or layers which each produce a respective depth plane to for a simulated 4D light field. Linear wave guides may have a rectangular cylindrical shape, and may stacked in rows and columns. Each linear wave guide is at least partially internally reflective, for example via at least one opposed pair of at least partially reflective planar side walls, to propagate light along a length of the wave guide. Curved micro-reflectors may reflect some modes of light while passing others. The side walls or a face may reflect some modes of light while passing others. The curved micro-reflectors of any given wave guide each contribute to spherical wave front at a defined radial distance, the various layers producing image planes at respective radial distances.

BACKGROUND

A light field encompasses all the light rays at every point in space traveling in every direction. Light fields are considered four dimensional because every point in a three-dimensional space also has an associated direction, which is the fourth dimension.

Wearable three-dimensional displays may include a substrate guided optical device, also known as the light-guide optical element (LOE) system. Such devices are manufactured by, for example Lumus Ltd. As illustrated inFIGS. 1B-1, 1B-2 and 1B-3, the LOE system10uses a single layer wave guide12made of two parallel planar surfaces14a,14b. Light16is coupled into the LOE wave guide12using a mini-projector (not shown) and reflector strip18.FIGS. 1B-1, 1B-2 and 1B-3illustrate the wave guide12of the LOE system10, showing light16entering at three respective angles, The LOE system10uses planar micro-reflectors20a-20n(only two called out for sake of drawing clarity) that are only oriented along one angular direction and are positioned parallel to one another. However, the LOE system10only projects a single depth plane, focused at infinity, with a spherical wave front curvature of zero.

DETAILED DESCRIPTION

The ability of the humans to perceive depth of field in a scene is limited, that is, humans have limited visual resolution at different radial distances. Consequently, to recreate an object or scene so that a user experiences the full 3D effect, not every possible focal plane in the 3D volume needs to be recreated. The 3D volume can be recreated for human perception by simply reproducing a limited number of slices of a particular 3D volume. Theories as to the number of slices that need to be recreated range from less than 16 to 36 or more, where the width of the slices are thinnest for distances closer to the eye and increase with distance. The human vision system (i.e. eyes, retinal nerve, brain) focally collapses each of these planes so that additional slices of information presented are not necessary for the human to perceive the 3D volume. Independent of the actual number of slices needed, the basic assumption is that only a finite number of slices of a 3D volume need to be reproduced for a human to perceive the full 3D effect.

An optical apparatus or system may be employed to, for example, generate or project light to simulate a four dimensional (4D) light field that would be produced by light reflecting from a real three-dimensional object or scene. For example, an optical apparatus such as a wave guide reflector array projector (WRAP) apparatus or multiple depth plane three dimensional (3D) display system may generate or project multiple virtual depth planes at respective radial focal distances to simulate a 4D light field. The optical apparatus in the form of a WRAP apparatus or multiple depth plane 3D display system may, for instance, project images into each eye of a user, either directly or indirectly. When the number and radial placement of the virtual depth planes is comparable to the depth resolution of the human vision system as a function of radial distance, a discrete set of projected depth planes mimics the psycho-physical effect that is produced by a real, continuous, three dimensional object or scene.

As best illustrated inFIG. 5A, an optical apparatus in the form of a WRAP apparatus or multiple depth plane 3D display system500may include a 2D array502of a plurality of wave guides504a-504n(collectively504, only two called out for drawing clarity). As illustrated, each of the wave guides504may have a rectangular cross section taken across a length or longitudinal axis thereof (the longitudinal axis denominated herein as x axis). The wave guides504may be arranged in a plurality of columns506(e.g., xy planes, extending vertically in the view ofFIG. 5A, only one called out for drawing clarity) and rows508(e.g., xz planes, extending horizontally in the view ofFIG. 5A, only one called out for drawing clarity). The columns506may be characterized as two-dimensional (2D) wave guides or sets of wave guides (each identified with reference number506). The 2D wave guides506may be stacked as layers, for example along a first lateral axis, denominated herein as z axis. As explained herein, each 2D planar wave guide, set of wave guides, layer or column506produces or generates a respective virtual depth plane at a respective distance to produce a 4D light field.

The WRAP apparatus or multiple depth plane 3D display system500may include one or more components to provide one or more optical paths to, or from, the wave guides504. For example, a set of distribution wave guides510a-510n(collectively510, only two called out for drawing clarity). The distribution wave guides may provide an optical path to wave guides504in respective columns or layers506. Also for example, in a non-multiplexed implementation, the WRAP apparatus or multiple depth plane 3D display system500may include a plurality of optical couplers (e.g., optical fibers) illustrated by arrows512(referenced collectively) that provide an optical path to respective ones of the distribution wave guides510(i.e., each respective column508). Also for example, in a multiplexed implementation, the WRAP apparatus or multiple depth plane 3D display system500may include a single optical coupler (e.g., optical fibers) illustrated by arrow514that provides an optical path to two, more or all of the distribution wave guides510. The distribution wave guides510and/or optical couplers512,514may, for example provide input to the wave guides504of the 2D array502, for instance as a pixel pattern from a source of red/green/blue (RGB) light (not illustrated inFIG. 5A.

As best illustrated inFIGS. 5B and 5C, each column or wave guide layer506a-506c(only three shown, collectively506) produces a respective slice or virtual depth plane522a-522c(only three shown, collectively522) having a spherical wave front524a-524c(only three shown, collectively524) to cumulatively simulate a 4D light field526. A position of a respective virtual point source528a-528c(only three shown, collectively528) for each of the virtual depth planes522a-522cis also illustrated.

FIG. 3Ashows a single column, 2D planar wave guide, column, layer or set of wave guides506, along with its respective distribution coupler510and an optical coupler512,514, according to one illustrated embodiment, Each of the 2D planar wave guides or layers506are comprised of a plurality of linear wave guides504e,504f(collectively504, only two called out for drawing clarity). The 2D planar wave guides506may, for example, each include a series or linear array of rectangular cylindrical wave guides504, sometimes referred to as wave guide tubes. While sometimes denominated as “tubes” one of skill in the art will readily appreciate that such structures do not need to be hollow, and in many implementations will be solid, similar in many respects to optical fibers but having at least one pair of opposed planar surfaces, which are at least partially internally reflective to propagate electromagnetic energy (e.g., light) along a length530of the wave guide504. As explained further herein, the at least one pair of opposed planar surfaces532a,532b(collectively532) may substantially internally reflect certain defined modes of light while allowing certain other defined modes of light to substantially pass out of the wave guide504. Typically, the wave guide504will include two pairs of opposed planar surfaces532a/532b,532c/532d(collectively532), which are partially internally reflective, for example substantially internally reflective of certain defined modes. As used herein and in the claims, the term substantially means more than 50 percent, and typically more than 85 percent or 95 percent. The wave guides504of the 2D planar wave guide, layer, column or set506may be formed individually and assembled or coupled together. Alternatively, the wave guides504of the 2D planar wave guide, layer, column or set506may be formed as a single unitary structure. Planar surfaces may facilitate production of the desired depth planes and/or increase the density of packing the wave guides504into a 3D structure.

Embedded, located or formed within each linear wave guide504is a series of deconstructed curved spherical reflectors or mirrors540a-540n(only two of the curved micro-reflectors called out for clarity of drawing) that are designed to refocus infinity-focused light at specific radial distances. It is noted that in the interest of drawing clarity, the full micro-reflectors of a single linear array of only one of the linear wave guides504are fully illustrated in broken line, the micro-reflectors of other linear arrays of other linear wave guides504represented schematically by simple convex curves. A number of micro-reflectors504A-504D for a single linear or rectangular wave guide504nare represented inFIG. 5A.

FIG. 1Ashows an example of how an input plane wave100focused at infinity can be reflected from a convex spherical mirror102to produce an output spherical wave104to represent a virtual point source106which appears to be located at a defined distance behind the convex spherical mirror102. By concatenating in a (linear or rectangular) wave guide a series of micro-reflectors540whose shapes (e.g., radii of curvature about two axes) and orientation together project a 3D image that corresponds to a spherical wave front produced by a virtual point source at a particular x, y, z, coordinate. Each of the 2D wave guides or layers506provides an independent optical path relative to the other wave guides, and shapes the wave front and focuses incoming light to project a virtual depth plane522(FIG. 5C) that corresponds to a respective radial distance. With a sufficient number of 2D wave guides, a user viewing the projected virtual depth planes experiences a 3D effect.

A multiple layer 2D array502of planar wave guides506is described herein, in which each layer projects light that corresponds to a different virtual depth plane in the 3D volume. As explained above,FIGS. 5A-5Cshows a portion of an example multiple layer WRAP display apparatus or system500with 2D planar wave guides, columns or sets of wave guides506stacked as layers. Each layer506includes multiple wave guides, for instance linear or rectangular wave guides504, as shown in the example ofFIG. 3A. A set of optical distribution couplers510and/or other optical couplers512,514optically couple the linear or rectangular wave guides504of the 2D array502, to other components. For instance, the optical distribution couplers510and/or other optical couplers512,514may optically couple the linear or rectangular wave guides504of the 2D array502to a subsystem that provides pixel patterns (e.g., RGB intensity modulated pixel patterns). In some instances the set of optical couplers510are referred to herein and/or in the claims as a linear array of column distribution couplers or as second lateral (Y) axis distribution optical couplers, or coupling tubes. As previously noted, one of skill in the art will readily appreciate that such structure do not need to be hollow, and in many implementations will be solid, similar in many respects to optical fiber.

Each individual wave guide504in the WRAP apparatus500includes a series of deconstructed curved spherical reflectors or mirrors540that are designed to refocus infinity-focused light at specific radial distances. A Fresnel lens is an example of a macroscopic optical element constructed from a series of optical micro-components. The WRAP apparatus500includes an array of micro-reflectors540that operate effectively as a side-injected (e.g., injected from a side denominated as the first end) Fresnel mirror.FIG. 18illustrates an example of an array of micro-reflectors1802a-1802n(collectively1802, only two called out for drawing clarity) in the configuration of a portion of a sphere1804rather than an array of micro-reflectors1806a-1806n(collectively1806, only two called out for drawing clarity) in a linear configuration1808as would be found in the equivalent Fresnel mirror, where the orientation of the micro-reflectors1802in the sphere configuration1804matches the orientation of the micro-components or micro-reflectors1806of the linear Fresnel mirror configuration1808.

What the WRAP Does

The WRAP apparatus500includes an array of curved micro-reflectors in the linear or rectangular wave guides504that comprise each of the 2D wave guides506. The array of curved micro-reflectors are positioned and oriented to act similarly to a lens or curved mirror, to project virtual images at specified radial distances. While denominated herein and/or in the claims as “reflectors,” as explained herein the curved micro-reflectors typically partially reflect and partially pass electromagnetic energy, for instance optical wavelengths of light (i.e., Near Infrared or N-IR, visible, Near Ultraviolet or N-UV). As described herein, the reflectance may be a function of an angular mode of the electromagnetic energy or light.

Conventional lens-based imaging systems or curved mirror-based imaging systems use optical elements with large surface curvatures. Conventional lens-based imaging systems or curved mirror-based imaging systems are front- or back-injected, typically by a wide light field from a projector element. Such conventional systems tend to be relatively thick and heavy, and often use multiple optical elements and moving parts to vary their focal lengths. In contrast, the illustrated 2D array502(FIG. 5A) of linear wave guides504of the WRAP apparatus500has a planar surface. The illustrated 2D array502of linear wave guides504of the WRAP apparatus500may be side-injected (i.e., injected into side denominated herein and in the claims as a first end) by a cone542(FIG. 3A) of narrow angled beams from an optical fiber which are then internally multiplied into a wide light field. The illustrated 2D array502of linear wave guides504of the WRAP apparatus500may be can be made very thin and light. The illustrated 2D planar wave guides or layers506may be easily stacked to create a multifocal display in which each 2D planar wave guide, layer, column or set506provides optical paths independently of other 2D planar wave guides, layers, columns or sets, for example allowing each to provide a respective focal or depth plane in a 3D image.

In contrast to the LOE system10(FIGS. 1B-1, 1B-2, 1B-3) described above, in one embodiment, the WRAP apparatus500projects multiple depth planes522(FIG. 5C), each focused at a different radial distance with the corresponding spherical wave front curvatures524(FIG. 5C). The WRAP apparatus500may include a series of linear or rectangular cylindrical wave guides arranged in vertical (xy) columns to create a planar 2D wave guide506, which is some instances may be referred to as a 2D assembly of linear or rectangular wave guides503. The WRAP apparatus500may include multiple 2D planar wave guides, columns, layers or sets506, each corresponding to a different virtual depth plane522(FIG. 5C). The WRAP apparatus500may use convex spherically curved micro-reflectors540(FIGS. 3A and 5A). The micro-reflectors540may have one or more surface curvatures, and the surface curvatures may vary in each wave guide layer506. As best illustrated inFIGS. 3B and 3C, each of the micro-reflectors540may be oriented along two angular directions φ, θ. The angular directions φ, θ may vary in any given linear wave guide504or may vary between linear wave guides504in a single layer506or between different layers506.

As best illustrated inFIG. 8, light (e.g., pixel pattern) may be coupled to the 2D array503of the WRAP apparatus500from one or more RGB (red, green, blue) light sources544, for example via one or more of a light intensity modulator546, fiber optic cables548, angular mode modulator or beam deflector550, optional optical demultiplexing switch for instance implemented via optical gates552, optional z-axis coupling array554, and the previously described and illustrated separate set of y-axis optical couplers or optical coupling array510.

What the WRAP Is

A WRAP apparatus500may include a stack of thin, planar, 2D wave guides506that are themselves made up of horizontal rows of linear or rectangular cylindrical wave guides504. While denominated as 2D, the 2D wave guides506physically have depth, but are denominated as such since each represents a 2D slice or portion (i.e., column) of the 2D array502. While denominated as a 2D, the 2D array of wave guides physically have a length, but are denominated as such since the length is an inherent property of the individual linear or rectangular wave guides504which may up the 2D array502, Likewise, while sometimes referred to as a linear wave guide504, these wave guides physically have heights and widths, but are denominated as such since each provides a linear optical path.

FIG. 3Ashows an example single layer of the 2D array503of a WRAP apparatus500. An input cone542of light is directed via an optical fiber512,514,548into a distribution optical coupler or y-axis optical coupler510, sometimes referred to herein as a coupling tube (oriented vertically inFIG. 3A). Mounted in a row within the optical coupler510are a number of multiple beam splitters556a-556n(collectively556, only two called out in interest of drawing clarity). Each beam splitter556vreflects a first portion of the light incident upon it to one of multiple stacked linear or rectangular wave guides504(oriented horizontally inFIG. 3A), and transmits a second portion of light to the next beam splitter556. Thus, light incident into the distribution optical coupler or y-axis optical coupler510is emitted into multiple linear or rectangular wave guides504positioned along at least a portion of a length of the distribution optical coupler or y-axis optical coupler510.

As previously explained, embedded, positioned or formed in each linear or rectangular wave guide504is a linear array of curved micro-reflectors540that are shaped and angularly oriented such that each angled light beam that is guided through the linear or rectangular wave guide504is projected from the linear or rectangular wave guide504by the micro-reflectors540into a three dimensional curved pattern.FIG. 3Bshows example orientation angles φ, θ of micro-reflectors540in a wave guide, where the micro-reflectors are represented in planar form for ease if illustration.FIG. 3Cshows an example of orientation angles φ, θ for a curved micro-reflector540. The projected pattern corresponds to the spherical wave front that is produced by a virtual point source placed at a given x,y,z coordinate, with the x and y coordinates being determined by the 2D angular orientation of the light beam, and the z-coordinate being determined by the particular configuration of micro-reflector shapes and 2D orientation gradients in a given 2D planar wave guide, column, layer or set506. Each 2D planar wave guide, column, layer or set506is configured to have different wave front shaping and focusing properties such that each layer projects a virtual depth plane corresponding to a different z-coordinate, or radial coordinate (r-coordinate).

A point source of light that is placed at a given x,y,z coordinate produces a radiating three dimensional pattern of light that varies in a very specific way throughout three dimensional space. Specifically, the point source generates a spherical wave front whose surface curvature varies in inverse proportion to the radius of the radiating sphere. The WRAP apparatus500is designed to generate a section of this sphere with the appropriate wave front curvature and two dimensional rotation, for a particular z-coordinate, upon receiving the input ray that corresponds to a given x, y coordinate.

How the WRAP Works

As shown in the example ofFIG. 3A, light input to each WRAP 2D planar wave guide, column, layer or set506may be provided via a separate multi-mode optical fiber512into which a small cone542of light has been injected. Alternatively, light input to each 2D planar wave guide, column, layer or set506is in the form of the light cone542via a respective output channel514of a demultiplexing switch552(FIG. 8). The light cone542contains a two dimensional angular distribution of light beams that corresponds to the two dimensional x, y light intensity pattern that is present in a single depth plane of a 3D volume to be re-created. There are a number of ways to couple the angular distribution of the light cone into the input fiber, such as using a MEMS scanner, a switchable liquid crystal, or a MEMS diffraction grating.

The propagating light cone542should have a defined or known angular pattern, for example as shown in the example ofFIG. 6. In some embodiments, the light cone542that propagates inside of the linear or rectangular wave guide504should lie approximately in the angular range of −22.5 degrees to −67.5 degrees, in both angular directions, and the light cone560that is projected out of the wave guide should lie approximately in the angular range of −22.5 degrees to +22.5 degrees, in both angular directions. Notably, on a relatively narrow range of ray angles will propagate in the wave guide, thus the angular range of the input image should be limited accordingly. Light that is propagated outside of these angular ranges will produce aliasing and double images.

There are two ways to drive the 2D planar wave guide, column, set or multiple layers506of the 2D array502, in parallel or in series. In the parallel method (shown in the example ofFIG. 5A), each wave guide layer506is driven by a different multi-mode fiber512that propagates an angular pattern corresponding to that portion of the visual field which is contained in a particular depth layer volume. These angular patterns are generated by drive electronics (e.g., RGB light source, intensity modulator) that are located in a base unit and then sent to the 2D array502in parallel over multiple multi-mode fibers512. For example, 2D images can be angularly encoded using a scanning projector system (such as the scanning fiber projector) or by coupling a 2D micro-projector to a pinhole aperture.

In the series method (shown in the example ofFIG. 8), the angular pattern for the entire visual field is simultaneously created and sorted amongst the different wave guide layers506, one angular beam at a time, using optical gates552that are synchronized with a 2D beam deflector550that creates the pattern. Because this process takes place at the 2D array502, distribution or y-axis optical coupler510and/or z-axis optical coupler562(FIG. 9), and not in a base unit, it can be driven by a single single-mode fiber514. In this system, input images are angularly encoded such that each resolvable angle that propagates through a fiber or other wave guide514corresponds to an intensity of a single object point. To encode an image in this way, multi-mode fibers514and optical couplers514,562are used that are able to propagate numerous angular modes with an angular density that is comparable to the linear resolution of the display. The angular range of the light cone corresponds to the maximum field of view of the optical apparatus500, for example, 45 degrees.

FIG. 9shows an example illustration of light propagation through a portion of a WRAP apparatus which includes a z-axis optical coupler562.FIG. 9represents the relative orientations of the z-axis optical coupler562, the distribution or y-axis optical coupler510, and the linear or rectangular wave guides (interchangeably referred to as x-axis wave guides)504. In the embodiment ofFIG. 9, light initially enters via the z-axis optical coupler562. The z-axis optical coupler may be similar in many respects to the linear or rectangular wave guides, for example having at least one pair of opposed planar sides that provide at least partial internal reflection to propagate or guide light along a length of the z-axis optical coupler562. The z-axis optical coupler562contains a linear array of angled, planar micro-reflectors564a-564n(collectively564) that multiply and inject copies of the incoming angular distribution of light into each of the distribution or y-axis optical couplers510of the various columns, sets or layers506. The distribution or y-axis optical couplers510may be similar in construction to the z-axis optical coupler562, having a linear array of angled, planar micro-reflectors566a-566n(collectively566). The distribution or y-axis optical couplers510multiplies and injects copies of the incoming angular distribution of light into each of the x-axis wave guides504in the respective column, set or layer506.

As shown inFIG. 2A, narrow, angled, plane wave light beam566enters the linear or rectangular wave guide504, reflecting from a planar reflector568toward at least one of the opposed reflective surfaces532. When each narrow, angled, plane wave light beam propagates through the wave guide and strikes a curved micro-reflector540, the plane wave light beam is split into two beams. Also as shown inFIG. 2A, a first beam continues to the next micro-reflector540, and a second beam is reflected in a divergent pattern with a curvature that is twice as great as that of a surface of the micro-reflector540from which the second beam reflected. In other words, a narrow incident plane wave is converted into a small wedge-like section of a spherical wave front that has a 2D orientation that corresponds to that of the incident plane wave. If the 2D orientations of all of the curved micro-reflectors540in a 2D wave guide, column, set or layer506are varied in a very precise way, all of the spherical wave front wedges that are projected from each micro-reflector540can be aligned into a single spherical wave front569that appears to be radiating from a virtual point570located at the x and y coordinates that correspond to the 2D orientation of the plane wave566and the z-coordinate that corresponds to the curvature(s) of the micro-reflector540and 2D orientation gradient of the 2D wave guide, column, set or layer506, as shown inFIG. 2B. For reference,FIGS. 13-15show coordinate systems for virtual object points, a 4D light field on a display surface, and 2D micro-reflector orientations, respectively.

As all of the angled, plane wave light beams in an input cone propagate throughout a 2D wave guide, plane, set or layer506, the beams recreate the superposed light field that is produced by a single depth plane. When all of the input signals for each 2D wave guide, plane, set or layer506propagate throughout the 2D array502they reproduce the superposed light field that is generated by multiple depth plane volumes. If these depth planes are sufficiently numerous and have the appropriate thicknesses as a function of their radial distance (as determined by the depth of field equation), such that if the depth planes meet or exceed the limits of human z-coordinate resolution (as well as x, y coordinate resolution), then the light field that is generated from a virtual 3D volume should be indistinguishable to a human from that of a real, physical, three dimensional space.

Because of the unique optical properties of the materials that are used in the optical system500(as described herein) each 2D wave guide, plane, set or layer506is mutually unaffected by the other 2D wave guide, plane, set or layers506. This feature allows the 2D wave guide, plane, set or layers506to be stacked on top of each other to create a multifocal optical system, a feature which is not believe to be possible with conventional lenses.

Additionally, orthogonal light polarization can be used to decouple light from the real outside world from that of the virtual display to create an augmented reality multiple depth plane 3D display. Polarized reflectors540only reflect that portion of light which is aligned parallel to the axis of polarization of the reflector. Cross polarized light is not reflected by the reflector540, and in the case of a semi-transparent reflector540, would simply pass through the reflector without being reflected. In this way, a 2D wave guide, plane, set or layer506can be made transparent to light from the outside world or to other 2D wave guide, plane, set or layers506simply by cross polarizing the 2D wave guide, plane, set or layer's506light.

If a 2D light pattern1602is generated that corresponds to the radial pinhole projections of the entire virtual 3D volume1604in a time sequential manner, and each of the points in the 2D field are depth indexed, for example, as shown inFIG. 16, then as shown inFIG. 8, a z-axis optical coupler562(FIG. 9) can be equipped with optical gates522that are synchronized with the beam deflector550to sort the light beams from a multiplexed input cone542into multiple output channel cones572(only one called out inFIG. 8for clarity of drawing) that correspond to each of the depth plane in the virtual 3D volume1604.

In the series method for driving the different 2D wave guide, plane, set or layers506of the 2D array502discussed above, the 2D array502is driven by a single single-mode fiber514,548, and the light cones572that correspond to the different 2D wave guide, plane, set or layers506are generated within the device itself. The light angles should be simultaneously created and sorted, one angle at a time. If the light angles are not created in a time sequential manner, the light angles cannot easily be sorted into each of the 2D wave guide, plane, set or layers506.

Mathematical Observations

The optical apparatus500can be viewed as a mathematical operator that transforms 2D light fields into 4D light fields.FIG. 4shows example details of the transformation. The optical apparatus500performs the transformation by applying a positive curvature to each of the light beams in an input cone402and mapping406a 2D array of differentially rotated copies of the modified light cone onto a surface of a display. These operations are physically generated by the array(s) of micro-reflectors540and have the effect of transforming narrow, plane wave light beams into wide, spherical wave fronts404; converting light cones into virtual depth planes; and generating a 3D volume from a stack of two dimensional projections, as shown in the example ofFIG. 12. (For comparison,FIGS. 4 and 12also show an input cone408generated into a flat wave front410.)FIG. 13shows a coordinate system1300for virtual object points.FIG. 14shows a coordinate system1400for a 4D light field on a display surface.FIG. 15shows a coordinate system1500for two-dimensional micro-reflector orientations.

Within the context of the optical apparatus500, linear or rectangular wave guides504function as beam multipliers and wideners that mathematically and physically generate a wide 2D array of light beams based on the input of a single, narrow light beam.FIG. 19illustrates how a light cone1902a-1902d(collectively1902) is multiplied through the use of multiple beam splitters that transmit a portion of incident light and reflect a portion of the incident light.

Example System Specifications

The micro-reflectors (e.g., curved micro-reflectors504) should be partially transparent and perform the function of a beam splitter as well as a reflector. In this way, a single beam of light having a narrow range of angles can be repeatedly multiplied and redistributed through the array to create a wide 4D light field.

Further, the reflectances of the reflective surfaces (e.g.532) of the wave guides (e.g., linear or rectangular wave guides504) and the micro-reflectors (e.g., curved micro-reflectors504) should be angle specific. Specifically, the micro-reflectors (e.g., curved micro-reflectors504) should only reflect the angular modes of the input cone that are internally reflected from the surface (e.g.,532) of the wave guide (e.g., linear or rectangular wave guides504), and should be transparent to all other angular modes. Each wave guide (e.g., linear or rectangular wave guides504) should only be transparent to the angular modes which are reflected from the micro-reflectors (e.g., curved micro-reflectors504) and should confine all other angular modes to the interior of the wave guide (e.g., linear or rectangular wave guides504). This allows the light from the input cone to be distributed throughout the entire length of the wave guide (e.g., linear or rectangular wave guides504) and to be coupled to each of the micro-reflectors (e.g., curved micro-reflectors504) before being projected out of the 2D array502. This also prevents light from striking the micro-reflectors (e.g., curved micro-reflectors504) from two opposing surfaces (e.g.,532) in the wave guides (e.g., linear or rectangular wave guides504), which would result in the creation of a dual set of images instead of a single set of images.

This may restrict the field of view. For example, this may restrict the field of view to a maximum field of view (FOV)700(FIG. 7) of 45 degrees. Of the total possible 360 degrees of angles that can propagate in the wave guide, half of those angles (180 degrees) are propagating in the wrong direction (out of, instead of into the wave guide), another 45 degrees correspond to the field of view that is projected out by the micro-reflectors, and a further 45 degrees correspond to the angularly shifted light cone that is propagated by the wave guide before the light cone strikes the micro-reflectors. The remaining 90 degrees do not appear useable because these angles may create aliasing effects from the secondary reflections off the outer wave guide surface, as shown inFIG. 6. In practice, the field of view700of the optical apparatus500will be less than 45 degrees to accommodate the beam curvature that is produced by the micro-reflectors540, as shown inFIG. 7.

The light beams that are coupled into the linear or rectangular wave guides504should be wide enough so that the micro-reflectors540are evenly covered by the light beams, and gaps and irregularities in the output are minimized.FIG. 20shows an example where the width of the light beam2002is not wide enough to prevent gaps in the light beam array.

For the display to function as an augmented reality device, the light from the input cone should be polarized along a single axis, and the micro-reflectors540and reflective opposed surfaces532of the wave guides504should only reflect light that is polarized along the same axis. Furthermore, an exterior side of the display should have an orthogonally polarizing screen (not shown), such as a liquid crystal display, that allows the user to adjust the real-virtual contrast, i.e., the relative light intensities of the real and virtual visual fields. The orthogonally polarizing screen can also orthogonally polarize the light from the real world relative to the polarization axis of the virtual display, thus allowing the light to pass through the display without being affected by the micro-reflectors540or reflective opposed surfaces532of the linear or rectangular wave guides504.

Further, any phase differences and incoherence that is brought about by variations in path length, transit time and wavelength should be undetectable by the human visual system.

To be thin enough to be a wearable device, each 2D planar wave guide, column, set or layer506of the 2D array502should be as thin as possible. For example, in one embodiment with 10 layers, a thickness of approximately 1 mm per layer would work for the wearable device. With a larger number of layers, e.g., 25 to 35, near and far light fields can be fully recreated. However, fewer than 10 or greater than 35 layers can be used.

In some implementations, each 2D planar wave guide, column, set or layer506can be reconfigured in real-time, i.e., the curvature(s) of the micro-reflector(s)504and/or 2D orientation gradient can be dynamically varied in a rapid manner. Using such an implementation, the projection of each virtual depth layer can be time multiplexed, instead of being presented simultaneously. To do this, a single layer N-plane display system should be reconfigured at a rate N times that of the refresh rate of a single layer in an N-layer system. Dynamically configurable curved micro-reflectors504a(FIG. 10) may be employed. For example, two dimensional liquid crystal surfaces can be used, where the shapes and orientations of the surfaces can be controlled with electric and/or magnetic fields, as shown in the example ofFIG. 10. Alternatively, electrically and/or magnetically deformable microfluids can be used as the micro-reflectors504b, where the shapes and orientations can be dynamically changed, as shown in the example ofFIG. 17.

In some embodiments, transparent display screens whose pixels540bare able to project light in specified directions can be used to change the direction of the projected light, for instance as shown in the examples of the bottom ofFIG. 10andFIG. 11.

Operating the WRAP

FIG. 21is a flow diagram illustrating an example process2100of re-creating a three-dimensional volume on a display by driving a multiple layer wave guide in parallel. At block2105, the optical apparatus502receives multiple input light beams. Each of the multiple light beams can be delivered by a multi-mode optical fiber. Each of the multiple input light beams corresponds to an intensity pattern of a portion of a visual field in a different layer of the three-dimensional volume to be recreated.

Then at block2110, the system creates a set of intermediate light beams from each of the multiple input light beams.

Next, at block2115, the system independently rotates copies of the set of multiple intermediate light beams, and at block2120, projects a wave front that appears to radiate from a virtual point. All of the projected wave fronts together recreate the 3D volume for viewing by the user.

CONCLUSION

The above Detailed Description of examples of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific examples for the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. While processes or blocks are presented in a given order in this application, alternative implementations may perform routines having steps performed in a different order, or employ systems having blocks in a different order. Some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified to provide alternative or subcombinations. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed or implemented in parallel, or may be performed at different times. Further any specific numbers noted herein are only examples. It is understood that alternative implementations may employ differing values or ranges.

The various illustrations and teachings provided herein can also be applied to systems other than the system described above. The elements and acts of the various examples described above can be combined to provide further implementations of the invention.

Any patents and applications and other references noted above, including any that may be listed in accompanying filing papers, are incorporated herein by reference. Aspects of the invention can be modified, if necessary, to employ the systems, functions, and concepts included in such references to provide further implementations of the invention.

While certain aspects of the invention are presented below in certain claim forms, the applicant contemplates the various aspects of the invention in any number of claim forms. For example, while only one aspect of the invention is recited as a means-plus-function claim under 35 U.S.C. §112, sixth paragraph, other aspects may likewise be embodied as a means-plus-function claim, or in other forms, such as being embodied in a computer-readable medium. (Any claims intended to be treated under 35 U.S.C. §112, ¶ 6 will begin with the words “means for.”) Accordingly, the applicant reserves the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the invention.

U.S. Patent Application No. 61/658,355, filed Jun. 11, 2012 is incorporated herein by reference in its entirety.