Patent Description:
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 in <FIG>, the LOE system <NUM> uses a single layer wave guide <NUM> made of two parallel planar surfaces 14a, 14b. Light <NUM> is coupled into the LOE wave guide <NUM> using a mini-projector (not shown) and reflector strip <NUM>. <FIG> illustrate the wave guide <NUM> of the LOE system <NUM>, showing light <NUM> entering at three respective angles, The LOE system <NUM> uses planar micro-reflectors 20a-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 system <NUM> only projects a single depth plane, focused at infinity, with a spherical wave front curvature of zero.

The invention is directed to an optical apparatus according to claim <NUM>.

In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.

Examples of a wave guide reflector array projector (WRAP) system are illustrated in the figures. The examples and figures are illustrative rather than limiting.

Various aspects and examples of the invention will now be described. The following description provides specific details for a thorough understanding and enabling description of these examples. One skilled in the art will understand, however, that the invention may be practiced without many of these details. Additionally, some well-known structures or functions may not be shown or described in detail, so as to avoid unnecessarily obscuring the relevant description.

The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific examples of the technology. Certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section.

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 <NUM> to <NUM> 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 in <FIG>, an optical apparatus in the form of a WRAP apparatus or multiple depth plane 3D display system <NUM> may include a 2D array <NUM> of a plurality of wave guides 504a-504n (collectively <NUM>, only two called out for drawing clarity). As illustrated, each of the wave guides <NUM> may have a rectangular cross section taken across a length or longitudinal axis thereof (the longitudinal axis denominated herein as x axis). The wave guides <NUM> may be arranged in a plurality of columns <NUM> {e.g., xy planes, extending vertically in the view of <FIG>, only one called out for drawing clarity) and rows <NUM> {e.g., xz planes, extending horizontally in the view of <FIG>, only one called out for drawing clarity). The columns <NUM> may be characterized as two-dimensional (2D) wave guides or sets of wave guides (each identified with reference number <NUM>). The 2D wave guides <NUM> may 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 column <NUM> produces 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 system <NUM> may include one or more components to provide one or more optical paths to, or from, the wave guides <NUM>. For example, a set of distribution wave guides 510a-510n (collectively <NUM>, only two called out for drawing clarity). The distribution wave guides may provide an optical path to wave guides <NUM> in respective columns or layers <NUM>. Also for example, in a non-multiplexed implementation, the WRAP apparatus or multiple depth plane 3D display system <NUM> may include a plurality of optical couplers (e.g. , optical fibers) illustrated by arrows <NUM> (referenced collectively) that provide an optical path to respective ones of the distribution wave guides <NUM> (i.e., each respective column <NUM>). Also for example, in a multiplexed implementation, the WRAP apparatus or multiple depth plane 3D display system <NUM> may include a single optical coupler (e.g. , optical fibers) illustrated by arrow <NUM> that provides an optical path to two, more or all of the distribution wave guides <NUM>. The distribution wave guides <NUM> and/or optical couplers <NUM>, <NUM> may, for example provide input to the wave guides <NUM> of the 2D array <NUM>, for instance as a pixel pattern from a source of red/green/blue (RGB) light (not illustrated in <FIG>).

As best illustrated in <FIG>, each column or wave guide layer 506a-506c (only three shown, collectively <NUM>) produces a respective slice or virtual depth plane 522a-522c (only three shown, collectively <NUM>) having a spherical wave front 524a-524c (only three shown, collectively <NUM>) to cumulatively simulate a 4D light field <NUM>. A position of a respective virtual point source 528a-528c (only three shown, collectively <NUM>) for each of the virtual depth planes 522a-522c is also illustrated.

<FIG> shows a single column, 2D planar wave guide, column, layer or set of wave guides <NUM>, along with its respective distribution coupler <NUM> and an optical coupler <NUM>, <NUM>, according to one illustrated embodiment, Each of the 2D planar wave guides or layers <NUM> are comprised of a plurality of linear wave guides 504e, 504f (collectively <NUM>, only two called out for drawing clarity). The 2D planar wave guides <NUM> may, for example, each include a series or linear array of rectangular cylindrical wave guides <NUM>, 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 length <NUM> of the wave guide <NUM>. As explained further herein, the at least one pair of opposed planar surfaces 532a, 532b (collectively <NUM>) may substantially internally reflect certain defined modes of light while allowing certain other defined modes of light to substantially pass out of the wave guide <NUM>. Typically, the wave guide <NUM> will include two pairs of opposed planar surfaces 532a/532b, 532c/532d (collectively <NUM>), 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 <NUM> percent, and typically more than <NUM> percent or <NUM> percent. The wave guides <NUM> of the 2D planar wave guide, layer, column or set <NUM> may be formed individually and assembled or coupled together. Alternatively, the wave guides <NUM> of the 2D planar wave guide, layer, column or set <NUM> may 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 guides <NUM> into a 3D structure.

Embedded, located or formed within each linear wave guide <NUM> is a series of deconstructed curved spherical reflectors or mirrors 540a-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 guides <NUM> are fully illustrated in broken line, the micro-reflectors of other linear arrays of other linear wave guides <NUM> represented schematically by simple convex curves. A number of micro-reflectors 540A-540D for a single linear or rectangular wave guide 504n are represented in <FIG>.

<FIG> shows an example of how an input plane wave <NUM> focused at infinity can be reflected from a convex spherical mirror <NUM> to produce an output spherical wave <NUM> to represent a virtual point source <NUM> which appears to be located at a defined distance behind the convex spherical mirror <NUM>. By concatenating in a (linear or rectangular) wave guide a series of micro-reflectors <NUM> whose 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 layers <NUM> provides an independent optical path relative to the other wave guides, and shapes the wave front and focuses incoming light to project a virtual depth plane <NUM> (<FIG>) 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 array <NUM> of planar wave guides <NUM> is described herein, in which each layer projects light that corresponds to a different virtual depth plane in the 3D volume. As explained above, <FIG> shows a portion of an example multiple layer WRAP display apparatus or system <NUM> with 2D planar wave guides, columns or sets of wave guides <NUM> stacked as layers. Each layer <NUM> includes multiple wave guides, for instance linear or rectangular wave guides <NUM>, as shown in the example of <FIG>. A set of optical distribution couplers <NUM> and/or other optical couplers <NUM>, <NUM> optically couple the linear or rectangular wave guides <NUM> of the 2D array <NUM>, to other components. For instance, the optical distribution couplers <NUM> and/or other optical couplers <NUM>, <NUM> may optically couple the linear or rectangular wave guides <NUM> of the 2D array <NUM> to a subsystem that provides pixel patterns {e.g., RGB intensity modulated pixel patterns). In some instances the set of optical couplers <NUM> are 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 guide <NUM> in the WRAP apparatus <NUM> includes a series of deconstructed curved spherical reflectors or mirrors <NUM> that 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 apparatus <NUM> includes an array of micro-reflectors <NUM> that operate effectively as a side- injected {e.g., injected from a side denominated as the first end) Fresnel mirror. <FIG> illustrates an example of an array of micro-reflectors 1802a- 1802n (collectively <NUM>, only two called out for drawing clarity) in the configuration of a portion of a sphere <NUM> rather than an array of micro- reflectors 1806a-1806n (collectively <NUM>, only two called out for drawing clarity) in a linear configuration <NUM> as would be found in the equivalent Fresnel mirror, where the orientation of the micro-reflectors <NUM> in the sphere configuration <NUM> matches the orientation of the micro-components or micro-reflectors <NUM> of the linear Fresnel mirror configuration <NUM>.

The WRAP apparatus <NUM> includes an array of curved micro- reflectors in the linear or rectangular wave guides <NUM> that comprise each of the 2D wave guides <NUM>. 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 array <NUM> (<FIG>) of linear wave guides <NUM> of the WRAP apparatus <NUM> has a planar surface. The illustrated 2D array <NUM> of linear wave guides <NUM> of the WRAP apparatus <NUM> may be side-injected (i.e., injected into side denominated herein and in the claims as a first end) by a cone <NUM> (<FIG>) of narrow angled beams from an optical fiber which are then internally multiplied into a wide light field. The illustrated 2D array <NUM> of linear wave guides <NUM> of the WRAP apparatus <NUM> may be can be made very thin and light. The illustrated 2D planar wave guides or layers <NUM> may be easily stacked to create a multifocal display in which each 2D planar wave guide, layer, column or set <NUM> provides 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 system <NUM> (<FIG>) described above, in one embodiment, the WRAP apparatus <NUM> projects multiple depth planes <NUM> (<FIG>), each focused at a different radial distance with the corresponding spherical wave front curvatures <NUM> (<FIG>). The WRAP apparatus <NUM> may include a series of linear or rectangular cylindrical wave guides arranged in vertical (xy) columns to create a planar 2D wave guide <NUM>, which is some instances may be referred to as a 2D assembly of linear or rectangular wave guides <NUM>. The WRAP apparatus <NUM> may include multiple 2D planar wave guides, columns, layers or sets <NUM>, each corresponding to a different virtual depth plane <NUM> (<FIG>). The WRAP apparatus <NUM> may use convex spherically curved micro- reflectors <NUM> (<FIG> and <FIG>). The micro-reflectors <NUM> may have one or more surface curvatures, and the surface curvatures may vary in each wave guide layer <NUM>. As best illustrated in <FIG> and <FIG>, each of the micro- reflectors <NUM> may be oriented along two angular directions ϕ, Θ. The angular directions ϕ, Θ may vary in any given linear wave guide <NUM> or may vary between linear wave guides <NUM> in a single layer <NUM> or between different layers <NUM>.

As best illustrated in <FIG>,, light (e.g. , pixel pattern) may be coupled to the 2D array <NUM> of the WRAP apparatus <NUM> from one or more RGB (red, green, blue) light sources <NUM>, for example via one or more of a light intensity modulator <NUM>, fiber optic cables <NUM>, angular mode modulator or beam deflector <NUM>, optional optical demultiplexing switch for instance implemented via optical gates <NUM>, optional z-axis coupling array <NUM>, and the previously described and illustrated separate set of y-axis optical couplers or optical coupling array <NUM>.

A WRAP apparatus <NUM> may include a stack of thin, planar, 2D wave guides <NUM> that are themselves made up of horizontal rows of linear or rectangular cylindrical wave guides <NUM>. While denominated as 2D, the 2D wave guides <NUM> physically have depth, but are denominated as such since each represents a 2D slice or portion (i.e., column) of the 2D array <NUM>. 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 guides <NUM> which may up the 2D array <NUM>, Likewise, while sometimes referred to as a linear wave guide <NUM>, these wave guides physically have heights and widths, but are denominated as such since each provides a linear optical path.

<FIG> shows an example single layer of the 2D array <NUM> of a WRAP apparatus <NUM>. An input cone <NUM> of light is directed via an optical fiber <NUM>, <NUM>, <NUM> into a distribution optical coupler or y-axis optical coupler <NUM>, sometimes referred to herein as a coupling tube (oriented vertically in <FIG>). Mounted in a row within the optical coupler <NUM> are a number of multiple beam splitters 556a-556n (collectively <NUM>, only two called out in interest of drawing clarity). Each beam splitter 556vreflects a first portion of the light incident upon it to one of multiple stacked linear or rectangular wave guides <NUM> (oriented horizontally in <FIG>), and transmits a second portion of light to the next beam splitter <NUM>. Thus, light incident into the distribution optical coupler or y-axis optical coupler <NUM> is emitted into multiple linear or rectangular wave guides <NUM> positioned along at least a portion of a length of the distribution optical coupler or y-axis optical coupler <NUM>.

As previously explained, embedded, positioned or formed in each linear or rectangular wave guide <NUM> is a linear array of curved micro- reflectors <NUM> that are shaped and angularly oriented such that each angled light beam that is guided through the linear or rectangular wave guide <NUM> is projected from the linear or rectangular wave guide <NUM> by the micro- reflectors <NUM> into a three dimensional curved pattern. <FIG> shows example orientation angles ϕ, Θ of micro-reflectors <NUM> in a wave guide, where the micro-reflectors are represented in planar form for ease if illustration. <FIG> shows an example of orientation angles ϕ, Θ for a curved micro-reflector <NUM>. 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 set <NUM>. Each 2D planar wave guide, column, layer or set <NUM> is 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 apparatus <NUM> is 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.

As shown in the example of <FIG>, light input to each WRAP 2D planar wave guide, column, layer or set <NUM> may be provided via a separate multi-mode optical fiber <NUM> into which a small cone <NUM> of light has been injected. Alternatively, light input to each 2D planar wave guide, column, layer or set <NUM> is in the form of the light cone <NUM> via a respective output channel <NUM> of a demultiplexing switch <NUM> (<FIG>). The light cone <NUM> contains 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 cone <NUM> should have a defined or known angular pattern, for example as shown in the example of <FIG>. In some embodiments, the light cone <NUM> that propagates inside of the linear or rectangular wave guide <NUM> should lie approximately in the angular range of -<NUM> degrees to -<NUM> degrees, in both angular directions, and the light cone <NUM> that is projected out of the wave guide should lie approximately in the angular range of -<NUM> degrees to +<NUM> 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 layers <NUM> of the 2D array <NUM>, in parallel or in series. In the parallel method (shown in the example of <FIG>), each wave guide layer <NUM> is driven by a different multi-mode fiber <NUM> that 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 array <NUM> in parallel over multiple multi-mode fibers <NUM>. 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 of <FIG>), the angular pattern for the entire visual field is simultaneously created and sorted amongst the different wave guide layers <NUM>, one angular beam at a time, using optical gates <NUM> that are synchronized with a 2D beam deflector <NUM> that creates the pattern. Because this process takes place at the 2D array <NUM>, distribution or y-axis optical coupler <NUM> and/or z-axis optical coupler <NUM> (<FIG>), and not in a base unit, it can be driven by a single single-mode fiber <NUM>. In this system, input images are angularly encoded such that each resolvable angle that propagates through a fiber or other wave guide <NUM> corresponds to an intensity of a single object point. To encode an image in this way, multi-mode fibers <NUM> and optical couplers <NUM>, <NUM> are 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 apparatus <NUM>, for example, <NUM> degrees.

<FIG> shows an example illustration of light propagation through a portion of a WRAP apparatus which includes a z-axis optical coupler <NUM>. <FIG> represents the relative orientations of the z-axis optical coupler <NUM>, the distribution or y-axis optical coupler <NUM>, and the linear or rectangular wave guides (interchangeably referred to as x-axis wave guides) <NUM>. In the embodiment of <FIG>, light initially enters via the z-axis optical coupler <NUM>. 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 coupler <NUM>. The z-axis optical coupler <NUM> contains a linear array of angled, planar micro-reflectors 564a- 564n (collectively <NUM>) that multiply and inject copies of the incoming angular distribution of light into each of the distribution or y-axis optical couplers <NUM> of the various columns, sets or layers <NUM>. The distribution or y-axis optical couplers <NUM> may be similar in construction to the z-axis optical coupler <NUM>, having a linear array of angled, planar micro-reflectors 566a-566n (collectively <NUM>). The distribution or y-axis optical couplers <NUM> multiplies and injects copies of the incoming angular distribution of light into each of the x-axis wave guides <NUM> in the respective column, set or layer <NUM>.

As shown in <FIG>, narrow, angled, plane wave light beam <NUM> enters the linear or rectangular wave guide <NUM>, reflecting from a planar reflector <NUM> toward at least one of the opposed reflective surfaces <NUM>. When each narrow, angled, plane wave light beam propagates through the wave guide and strikes a curved micro-reflector <NUM>, the plane wave light beam is split into two beams. Also as shown in <FIG>, a first beam continues to the next micro-reflector <NUM>, 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-reflector <NUM> from 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-reflectors <NUM> in a 2D wave guide, column, set or layer <NUM> are varied in a very precise way, all of the spherical wave front wedges that are projected from each micro-reflector <NUM> can be aligned into a single spherical wave front <NUM> that appears to be radiating from a virtual point <NUM> located at the x and y coordinates that correspond to the 2D orientation of the plane wave <NUM> and the z-coordinate that corresponds to the curvature(s) of the micro-reflector <NUM> and 2D orientation gradient of the 2D wave guide, column, set or layer <NUM>, as shown in <FIG>. For reference, <FIG> show 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 layer <NUM>, 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 layer <NUM> propagate throughout the 2D array <NUM> they 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 system <NUM> (as described herein) each 2D wave guide, plane, set or layer <NUM> is mutually unaffected by the other 2D wave guide, plane, set or layers <NUM>. This feature allows the 2D wave guide, plane, set or layers <NUM> to be stacked on top of each other to create a multifocal optical system, a feature which is not believed 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 reflectors <NUM> only 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 reflector <NUM>, and in the case of a semi-transparent reflector <NUM>, would simply pass through the reflector without being reflected. In this way, a 2D wave guide, plane, set or layer <NUM> can be made transparent to light from the outside world or to other 2D wave guide, plane, set or layers <NUM> simply by cross polarizing the 2D wave guide, plane, set or layer's <NUM> light.

If a 2D light pattern <NUM> is generated that corresponds to the radial pinhole projections of the entire virtual 3D volume <NUM> in a time sequential manner, and each of the points in the 2D field are depth indexed, for example, as shown in <FIG>, then as shown in <FIG>, a z-axis optical coupler <NUM> (<FIG>) can be equipped with optical gates <NUM> that are synchronized with the beam deflector <NUM> to sort the light beams from a multiplexed input cone <NUM> into multiple output channel cones <NUM> (only one called out in <FIG> for clarity of drawing) that correspond to each of the depth plane in the virtual 3D volume <NUM>.

In the series method for driving the different 2D wave guide, plane, set or layers <NUM> of the 2D array <NUM> discussed above, the 2D array <NUM> is driven by a single single-mode fiber <NUM>, <NUM>, and the light cones <NUM> that correspond to the different 2D wave guide, plane, set or layers <NUM> are 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 layers <NUM>.

The optical apparatus <NUM> can be viewed as a mathematical operator that transforms 2D light fields into 4D light fields. <FIG> shows example details of the transformation. The optical apparatus <NUM> performs the transformation by applying a positive curvature to each of the light beams in an input cone <NUM> and mapping <NUM> a 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-reflectors <NUM> and have the effect of transforming narrow, plane wave light beams into wide, spherical wave fronts <NUM>; converting light cones into virtual depth planes; and generating a 3D volume from a stack of tw-dimensional projections, as shown in the example of <FIG>. (For comparison, <FIG> and <FIG> also show an input cone <NUM> generated into a flat wave front <NUM>. ) <FIG> shows a coordinate system <NUM> for virtual object points. <FIG> shows a coordinate system <NUM> for a 4D light field on a display surface. <FIG> shows a coordinate system <NUM> for two-dimensional micro-reflector orientations.

Within the context of the optical apparatus <NUM>, linear or rectangular wave guides <NUM> function 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> illustrates how a light cone 1902a1902d (collectively <NUM>) is multiplied through the use of multiple beam splitters that transmit a portion of incident light and reflect a portion of the incident light.

The micro-reflectors {e.g., curved micro-reflectors <NUM>) 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. <NUM>) of the wave guides {e.g., linear or rectangular wave guides <NUM>) and the micro- reflectors (e.g., curved micro-reflectors <NUM>) should be angle specific. Specifically, the micro-reflectors (e.g., curved micro-reflectors <NUM>) should only reflect the angular modes of the input cone that are internally reflected from the surface {e.g., <NUM>) of the wave guide (e.g., linear or rectangular wave guides <NUM>), and should be transparent to all other angular modes. Each wave guide {e.g., linear or rectangular wave guides <NUM>) should only be transparent to the angular modes which are reflected from the micro- reflectors (e.g., curved micro-reflectors <NUM>) and should confine all other angular modes to the interior of the wave guide (e.g., linear or rectangular wave guides <NUM>). 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 guides <NUM>) and to be coupled to each of the micro-reflectors (e.g., curved micro-reflectors <NUM>) before being projected out of the 2D array <NUM>. This also prevents light from striking the micro-reflectors (e.g., curved micro- reflectors <NUM>) from two opposing surfaces (e.g., <NUM>) in the wave guides (e.g., linear or rectangular wave guides <NUM>), 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) <NUM> (<FIG>) of <NUM> degrees. Of the total possible <NUM> degrees of angles that can propagate in the wave guide, half of those angles (<NUM> degrees) are propagating in the wrong direction (out of, instead of into the wave guide), another <NUM> degrees correspond to the field of view that is projected out by the micro-reflectors, and a further <NUM> 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 <NUM> degrees do not appear useable because these angles may create aliasing effects from the secondary reflections off the outer wave guide surface, as shown in <FIG>. In practice, the field of view <NUM> of the optical apparatus <NUM> will be less than <NUM> degrees to accommodate the beam curvature that is produced by the micro-reflectors <NUM>, as shown in <FIG>.

The light beams that are coupled into the linear or rectangular wave guides <NUM> should be wide enough so that the micro-reflectors <NUM> are evenly covered by the light beams, and gaps and irregularities in the output are minimized. <FIG> shows an example where the width of the light beam <NUM> is 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-reflectors <NUM> and reflective opposed surfaces <NUM> of the wave guides <NUM> should 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-reflectors <NUM> or reflective opposed surfaces <NUM> of the linear or rectangular wave guides <NUM>.

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 layer <NUM> of the 2D array <NUM> should be as thin as possible. For example, in one embodiment with <NUM> layers, a thickness of approximately <NUM> per layer would work for the wearable device. With a larger number of layers, e.g., <NUM> to <NUM>, near and far light fields can be fully recreated. However, fewer than <NUM> or greater than <NUM> layers can be used.

In some implementations, each 2D planar wave guide, column, set or layer <NUM> can be reconfigured in real-time, i.e., the curvature(s) of the micro-reflector(s) <NUM> and/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-reflectors 504a (<FIG>) 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 of <FIG>. Alternatively, electrically and/or magnetically deformable microfluids can be used as the micro-reflectors 504b, where the shapes and orientations can be dynamically changed, as shown in the example of <FIG>.

In some embodiments, transparent display screens whose pixels 540b are 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 of <FIG> and <FIG>.

<FIG> is a flow diagram illustrating an example process <NUM> of re-creating a three-dimensional volume on a display by driving a multiple layer wave guide in parallel. At block <NUM>, the optical apparatus <NUM> receives 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 block <NUM><NUM>, the system creates a set of intermediate light beams from each of the multiple input light beams.

Next, at block <NUM><NUM>, the system independently rotates copies of the set of multiple intermediate light beams, and at block <NUM>, 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.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense (i.e., to say, in the sense of "including, but not limited to"), as opposed to an exclusive or exhaustive sense. As used herein, the terms "connected," "coupled," or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements. Such a coupling or connection between the elements can be physical, logical, or a combination thereof. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word "or," in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

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.

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.

Claim 1:
An optical apparatus (<NUM>), comprising:
a two dimensional array (<NUM>) of a plurality of wave guides (504a-504n) arranged in a plurality of rows (<NUM>) and columns (<NUM>), each of the wave guides (504a-504n) having a first end, a second end spaced from the first end along a length of the wave guide, at least a first pair of opposed sides which are at least partially reflective toward an interior of the wave guide to reflect light along the length of the wave guide, the length which defines a major axis of the respective wave guide, each of the wave guides (504a-504n) having a plurality of curved micro-reflectors (540a-540n) disposed at respective positions along the length of the respective wave guide and which are at least partially reflective of at least defined wavelengths, the curved micro-reflectors (540a-540n) oriented at respective angles with respect to the face of the respective wave guide to provide in conjunction with at least the first pair of opposed sides an optical path that extends between the face and the first end of the wave guide, wherein the curved micro-reflectors (540a-540n) are each oriented at a respective angle about a lateral axis of the respective wave guide, the lateral axis perpendicular to the major axis, to reflect a portion of electromagnetic energy from a face of the wave guide in a spherical wave front; and
a linear array of column distribution couplers (510a-510n), a respective column distribution coupler for each column (<NUM>) of the two dimensional array (<NUM>) of the plurality of wave guides (504a-504n), each of the column distribution couplers (510a-510n) having a first end, a second end spaced from the first end along a length of the column distribution coupler, each of the column distribution couplers (510a-510n) having a plurality of elements (556a-556n) that provide an optical path between the first end of the column distribution coupler and a respective one of the wave guides (504a-504n) in the respective column (<NUM>) of the two dimensional array (<NUM>) of the plurality of wave guides (504a-504n).