Patent Description:
Modern computing and display technologies have facilitated the development of systems for so called "virtual reality" or "augmented reality" experiences, wherein digitally reproduced images or portions thereof are presented to a user in a manner wherein they seem to be, or may be perceived as, real. A virtual reality, or "VR", scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input; an augmented reality, or "AR", scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user (i.e., transparency to other actual real-world visual input). Document <CIT> discloses an example of an AR device. Accordingly, AR scenarios involve presentation of digital or virtual image information with transparency to other actual real-world visual input. The human visual perception system is very complex, and producing a VR or AR technology that facilitates a comfortable, natural-feeling, rich presentation of virtual image elements amongst other virtual or real-world imagery elements is challenging.

The visualization center of the brain gains valuable perception information from the motion of both eyes and components thereof relative to each other. Vergence movements (i.e., rolling movements of the pupils toward or away from each other to converge the lines of sight of the eyes to fixate upon an object) of the two eyes relative to each other are closely associated with focusing (or "accommodation") of the lenses of the eyes. Under normal conditions, changing the focus of the lenses of the eyes, or accommodating the eyes, to focus upon an object at a different distance will automatically cause a matching change in vergence to the same distance, under a relationship known as the "accommodation-vergence reflex. " Likewise, a change in vergence will trigger a matching change in accommodation, under normal conditions. Working against this reflex, as do most conventional stereoscopic AR or VR configurations, is known to produce eye fatigue, headaches, or other forms of discomfort in users.

Stereoscopic wearable glasses generally feature two displays for the left and right eyes that are configured to display images with slightly different element presentation such that a three-dimensional perspective is perceived by the human visual system. Such configurations have been found to be uncomfortable for many users due to a mismatch between vergence and accommodation ("vergence-accommodation conflict") which must be overcome to perceive the images in three dimensions. Indeed, some users are not able to tolerate stereoscopic configurations. These limitations apply to both AR and VR systems. Accordingly, most conventional AR and VR systems are not optimally suited for presenting a rich, binocular, three-dimensional experience in a manner that will be comfortable and maximally useful to the user, in part because prior systems fail to address some of the fundamental aspects of the human perception system, including the vergence-accommodation conflict.

AR and/or VR systems must also be capable of displaying virtual digital content at various perceived positions and distances relative to the user. The design of AR and/or VR systems also presents numerous other challenges, including the speed of the system in delivering virtual digital content, quality of virtual digital content, eye relief of the user (addressing the vergence-accommodation conflict), size and portability of the system, and other system and optical challenges.

One possible approach to address these problems (including the vergence-accommodation conflict) is to project light at the eyes of a user using a plurality of light-guiding optical elements such that the light and images rendered by the light appear to originate from multiple depth planes. The light-guiding optical elements are designed to in-couple virtual light corresponding to digital or virtual objects and propagate it by total internal reflection ("TIR"), then to out-couple the virtual light to display the digital or virtual objects to the user's eyes. In AR systems, the light-guiding optical elements are also designed be transparent to light from (e.g., reflecting off of) actual real-world objects. Therefore, portions of the light-guiding optical elements are designed to reflect virtual light for propagation via TIR while being transparent to real-world light from real-world objects in AR systems.

To implement multiple light-guiding optical element systems, light from one or more sources must be controllably distributed to each of the light-guiding optical element systems. One approach is to use a large number of optical elements (e.g., light sources, prisms, gratings, filters, scan-optics, beam splitters, mirrors, half-mirrors, shutters, eye pieces, etc.) to project images at a sufficiently large number (e.g., six) of depth planes. The problem with this approach is that using a large number of components in this manner necessarily requires a larger form factor than is desirable, and limits the degree to which the system size can be reduced. The large number of optical elements in these systems also results in a longer optical path, over which the light and the information contained therein will be degraded. These design issues result in cumbersome systems which are also power intensive.

<CIT> discloses an imaging system according to the preamble of claim <NUM>. Improvements relating to further reducing the form factor remain desirable.

The systems and methods described herein are configured to address these challenges.

The invention is directed to an imaging system according to claim <NUM>.

Additional and other objects, features, and advantages of the invention are described in the detail description, figures and claims.

The drawings illustrate the design and utility of various embodiments of the present invention. It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. In order to better appreciate how to obtain the above-recited and other advantages and objects of various embodiments of the invention, a more detailed description of the present inventions briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:.

Various embodiments of the invention and examples are directed to systems, methods, and articles of manufacture for implementing optical systems in a single embodiment or in multiple embodiments. Other objects, features, and advantages of the invention are described in the detailed description, figures, and claims.

Various embodiments and examples will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and the examples below are not meant to limit the scope of the present invention. Where certain elements of the present invention may be partially or fully implemented using known components (or methods or processes), only those portions of such known components (or methods or processes) that are necessary for an understanding of the present invention will be described, and the detailed descriptions of other portions of such known components (or methods or processes) will be omitted so as not to obscure the invention. Further, various embodiments encompass present and future known equivalents to the components referred to herein by way of illustration.

The optical systems may be implemented independently of AR systems, but many embodiments below are described in relation to AR systems for illustrative purposes only.

One type of optical system for generating images at various depths includes numerous optical components (e.g., light sources, prisms, gratings, filters, scan-optics, beam splitters, mirrors, half-mirrors, shutters, eye pieces, etc.) that increase in number, thereby increasing the complexity, size and cost of AR and VR systems, as the quality of the 3D experience/scenario (e.g., the number of imaging planes) and the quality of images (e.g., the number of image colors) increases. The increasing size of optical systems with increasing 3D scenario/image quality imposes a limit on the size of AR and VR systems resulting in cumbersome systems with reduced efficiency.

The following disclosure describes various examples and embodiments of systems and methods for creating 3D perception using multiple-plane focus optical elements that address the problem, by providing optical systems with fewer components and increased efficiency. In particular, the systems described herein utilize various light distribution systems, including various system components and designs, to reduce the size of optical systems while selectively distributing light from one or more light sources to the plurality of light-guiding optical elements ("LOEs"; e.g., planar waveguides) required to render high quality AR and VR scenarios.

Before describing the details of examples and embodiments of the light distribution systems, this disclosure will now provide a brief description of illustrative optical systems. While the embodiments are can be used with any optical system, specific systems (e.g., AR systems) are described to illustrate the technologies underlying the embodiments.

One possible approach to implementing an AR system uses a plurality of volume phase holograms, surface-relief holograms, or light-guiding optical elements that are embedded with depth plane information to generate images that appear to originate from respective depth planes. In other words, a diffraction pattern, or diffractive optical element ("DOE") may be embedded within or imprinted upon an LOE such that as collimated light (light beams with substantially planar wavefronts) is substantially totally internally reflected along the LOE, it intersects the diffraction pattern at multiple locations and exits toward the user's eye. The DOEs are configured so that light exiting therethrough from an LOE are verged so that they appear to originate from a particular depth plane. The collimated light may be generated using an optical condensing lens (a "condenser").

For example, a first LOE may be configured to deliver collimated light to the eye that appears to originate from the optical infinity depth plane (<NUM> diopters). Another LOE may be configured to deliver collimated light that appears to originate from a distance of <NUM> meters (<NUM>/<NUM> diopter). Yet another LOE may be configured to deliver collimated light that appears to originate from a distance of <NUM> meter (<NUM> diopter). By using a stacked LOE assembly, it can be appreciated that multiple depth planes may be created, with each LOE configured to display images that appear to originate from a particular depth plane. It should be appreciated that the stack may include any number of LOEs. However, at least N stacked LOEs are required to generate N depth planes. Further, N, 2N or 3N stacked LOEs may be used to generate RGB colored images at N depth planes.

In order to present 3D virtual content to the user, the augmented reality (AR) system projects images of the virtual content into the user's eye so that they appear to originate from various depth planes in the Z direction (i.e., orthogonally away from the user's eye). In other words, the virtual content may not only change in the X and Y directions (i.e., in a 2D plane orthogonal to a central visual axis of the user's eye), but it may also appear to change in the Z direction such that the user may perceive an object to be very close or at an infinite distance or any distance in between. In other examples, the user may perceive multiple objects simultaneously at different depth planes. For example, the user may see a virtual dragon appear from infinity and run towards the user. Alternatively, the user may simultaneously see a virtual bird at a distance of <NUM> meters away from the user and a virtual coffee cup at arm's length (about <NUM> meter) from the user.

Multiple-plane focus systems create a perception of variable depth by projecting images on some or all of a plurality of depth planes located at respective fixed distances in the Z direction from the user's eye. Referring now to <FIG>, it should be appreciated that multiple-plane focus systems typically display frames at fixed depth planes <NUM> (e.g., the six depth planes <NUM> shown in <FIG>). Although AR systems can include any number of depth planes <NUM>, one exemplary multiple-plane focus system has six fixed depth planes <NUM> in the Z direction. In generating virtual content one or more of the six depth planes <NUM>, 3D perception is created such that the user perceives one or more virtual objects at varying distances from the user's eye. Given that the human eye is more sensitive to objects that are closer in distance than objects that appear to be far away, more depth planes <NUM> are generated closer to the eye, as shown in <FIG>. In other examples, the depth planes <NUM> may be placed at equal distances away from each other.

Depth plane positions <NUM> are typically measured in diopters, which is a unit of optical power equal to the inverse of the focal length measured in meters. For example, in one example, depth plane <NUM> may be <NUM>/<NUM> diopters away, depth plane <NUM> may be <NUM> diopters away, depth plane <NUM> may be <NUM> diopters away, depth plane <NUM> may be <NUM> diopters away, depth plane <NUM> may be <NUM> diopters away, and depth plane <NUM> may represent infinity (i.e., <NUM> diopters away). It should be appreciated that other examples may generate depth planes <NUM> at other distances/diopters. Thus, in generating virtual content at strategically placed depth planes <NUM>, the user is able to perceive virtual objects in three dimensions. For example, the user may perceive a first virtual object as being close to him when displayed in depth plane <NUM>, while another virtual object appears at infinity at depth plane <NUM>. Alternatively, the virtual object may first be displayed at depth plane <NUM>, then depth plane <NUM>, and so on until the virtual object appears very close to the user. It should be appreciated that the above examples are significantly simplified for illustrative purposes. In another example, all six depth planes may be concentrated on a particular focal distance away from the user. For example, if the virtual content to be displayed is a coffee cup half a meter away from the user, all six depth planes could be generated at various cross-sections of the coffee cup, giving the user a highly granulated 3D view of the coffee cup.

In one example, the AR system may work as a multiple-plane focus system. In other words, all six LOEs may be illuminated simultaneously, such that images appearing to originate from six fixed depth planes are generated in rapid succession with the light sources rapidly conveying image information to LOE <NUM>, then LOE <NUM>, then LOE <NUM> and so on. For example, a portion of the desired image, comprising an image of the sky at optical infinity may be injected at time <NUM> and the LOE <NUM> retaining collimation of light (e.g., depth plane <NUM> from <FIG>) may be utilized. Then an image of a closer tree branch may be injected at time <NUM> and an LOE <NUM> configured to create an image appearing to originate from a depth plane <NUM> meters away (e.g., depth plane <NUM> from <FIG>) may be utilized; then an image of a pen may be injected at time <NUM> and an LOE <NUM> configured to create an image appearing to originate from a depth plane <NUM> meter away may be utilized. This type of paradigm can be repeated in rapid time sequential (e.g., at <NUM>) fashion such that the user's eye and brain (e.g., visual cortex) perceives the input to be all part of the same image.

AR systems are required to project images (i.e., by diverging or converging light beams) that appear to originate from various locations along the Z axis (i.e., depth planes) to generate images for a 3D experience. As used in this application, light beams including, but are not limited to, directional projections of light energy (including visible and invisible light energy) radiating from a light source. Generating images that appear to originate from various depth planes conforms the vergence and accommodation of the user's eye for that image, and minimizes or eliminates vergence-accommodation conflict.

<FIG> depicts a basic optical system <NUM> for projecting images at a single depth plane. The system <NUM> includes a light source <NUM> and an LOE <NUM> having a diffractive optical element (not shown) and an in-coupling grating <NUM> ("ICG") associated therewith. The light source <NUM> can be any suitable imaging light source, including, but not limited to DLP, LCOS, LCD and Fiber Scanned Display. Such light sources can be used with any of the systems <NUM> described herein. The diffractive optical elements may be of any type, including volumetric or surface relief. The ICG <NUM> can be a reflection-mode aluminized portion of the LOE <NUM>. Alternatively, the ICG <NUM> can be a transmissive diffractive portion of the LOE <NUM>. When the system <NUM> is in use, a virtual light beam <NUM> from the light source <NUM>, enters the LOE <NUM> via the ICG <NUM> and propagates along the LOE <NUM> by substantially total internal reflection ("TIR") for display to an eye of a user. The light beam <NUM> is virtual because it encodes an image or a portion thereof as directed by the system <NUM>. It is understood that although only one beam is illustrated in <FIG>, a multitude of beams, which encode an image, may enter LOE <NUM> from a wide range of angles through the same ICG <NUM>. A light beam "entering" or being "admitted" into an LOE includes, but is not limited to, the light beam interacting with the LOE so as to propagate along the LOE by substantially TIR. The system <NUM> depicted in <FIG> can include various light sources <NUM> (e.g., LEDs, OLEDs, lasers, and masked broad-area/broad-band emitters). Light from the light source <NUM> may also be delivered to the LOE <NUM> via fiber optic cables (not shown).

<FIG> depicts another optical system <NUM>', which includes a light source <NUM>, and respective pluralities (e.g., three) of LOEs <NUM>, and in-coupling gratings <NUM>. The optical system <NUM>' also includes three beam splitters <NUM> (to direct light to the respective LOEs) and three shutters <NUM> (to control when the LOEs are illuminated). The shutters <NUM> can be any suitable optical shutter, including, but not limited to, liquid crystal shutters. The beam splitters <NUM> and shutters <NUM> are depicted schematically in <FIG> without specifying a configuration to illustrate the function of optical system <NUM>'. The examples described below include specific optical element configurations that address various issues with optical systems.

When the system <NUM>' is in use, the virtual light beam <NUM> from the light source <NUM> is split into three virtual light sub-beams/beam lets <NUM>' by the three-beam splitters <NUM>. The three beam splitters also redirect the beam lets toward respective in-coupling gratings <NUM>. After the beamlets enter the LOEs <NUM> through the respective in-coupling gratings <NUM>, they propagate along the LOEs <NUM> by substantially TIR (not shown) where they interact with additional optical structures resulting in display to an eye of a user. The surface of in-coupling gratings <NUM> on the far side of the optical path can be coated with an opaque material (e.g., aluminum) to prevent light from passing through the in-coupling gratings <NUM> to the next LOE <NUM>. The beam splitters <NUM> can be combined with wavelength filters to generate red, green and blue beamlets. Three single-color LOEs <NUM> are required to display a color image at a single depth plane. Alternatively, LOEs <NUM> may each present a portion of a larger, single depth-plane image area angularly displaced laterally within the user's field of view, either of like colors, or different colors ("tiled field of view"). While all three virtual light beamlets <NUM>' are depicted as passing through respective shutters <NUM>, typically only one beamlet <NUM>' is selectively allowed to pass through a corresponding shutter <NUM> at any one time. In this way, the system <NUM>' can coordinate image information encoded by the beam <NUM> and beamlet <NUM>' with the LOE <NUM> through which the beamlet <NUM> and the image information encoded therein will be delivered to the user's eye.

<FIG> depicts still another optical system <NUM>", having respective pluralities (e.g., six) of beam splitters <NUM>, shutters <NUM>, ICGs <NUM>, and LOEs <NUM>. As explained above during the discussion of <FIG>, three single-color LOEs <NUM> are required to display a color image at a single depth plane. Therefore, the six LOEs <NUM> of this system <NUM>" are able to display color images at two depth planes. The beam splitters <NUM> in optical system <NUM>" have different sizes. The shutters <NUM> in optical system <NUM>" have different sizes corresponding to the size of the respective beam splitters <NUM>.

The ICGs <NUM> in optical system <NUM>" have different sizes corresponding to the size of the respective beam splitters <NUM> and the length of the beam path between the beam splitters <NUM> and their respective ICGs <NUM>. The longer the distance beam path between the beam splitters <NUM> and their respective ICGs <NUM>, the more the beams diverge and require a larger ICGs <NUM> to in-couple the light. As shown in <FIG>, larger beam splitters <NUM> also require larger ICGs <NUM>. While larger beam splitters <NUM> allow light sources <NUM> to have larger scan angles, and thus larger fields of view ("FOVs"), they also require larger ICGs <NUM>, which are susceptible to a "second encounter problem.

The second encounter problem is depicted in <FIG>. The virtual light beamlet <NUM>' depicted in <FIG> enters an LOE <NUM> through an ICG <NUM>. The size of ICG <NUM> is such that as the beamlet <NUM>' propagates through the LOE <NUM> by TIR, the beamlet <NUM>' encounters the ICG <NUM> at a second location <NUM>. This second encounter allows unintended out-coupling of light from the LOE <NUM>, thereby decreasing the intensity of the light propagated along the LOE <NUM>. Accordingly, increasing the size of an ICG <NUM> such that a beamlet <NUM>' has a second encounter with the ICG <NUM> during TIR will decrease the efficiency of the optical system <NUM>" for select LOEs <NUM>. Examples addressing the second encounter problem are described below.

While this problem is described as a "second" encounter problem, larger ICGs <NUM> can cause a series of repeat encounters that would further decrease the optical efficiency. Further, as shown in <FIG>, as the number of depth planes, field tiles, or colors generated increases (e.g., with increased AR scenario quality), the numbers of LOEs <NUM> and ICGs <NUM> increases. For example, a single RGB color depth plane requires at least three single-color LOEs <NUM> with three ICGs <NUM>. As a result, the opportunity for inadvertent in-coupling of real-world light at these optical elements also increases. Moreover, real-world light can be in-coupled all along an LOE <NUM>, including at out-coupling gratings (not shown). Thus the increasing number of optical elements required to generate an acceptable AR scenario exacerbates the second encounter problem for the system <NUM>.

As shown in <FIG>, portions of the LOEs <NUM> described above can function as exit pupil expanders <NUM> ("EPE") to increase the numerical aperture of a light source <NUM> in the Y direction, thereby increasing the resolution of the system <NUM>. Since the light source <NUM> produces light of a small diameter/spot size, the EPE <NUM> expands the apparent size of the pupil of light exiting from the LOE <NUM> to increase the system resolution. The AR system <NUM> may further comprise an orthogonal pupil expander <NUM> ("OPE") in addition to an EPE <NUM> to expand the light in both the X (OPE) and Y (EPE) directions. More details about the EPEs <NUM> and OPEs <NUM> are described in the above-referenced <CIT> and <CIT>.

<FIG> depicts an LOE <NUM> having an ICG <NUM>, an OPE <NUM> and an EPE <NUM>. <FIG> depicts the LOE <NUM> from a top view that is similar to the view from a user's eyes. The ICG <NUM>, OPE <NUM>, and EPE <NUM> may be any type of DOE, including volumetric or surface relief.

The ICG <NUM> is a DOE (e.g., a linear grating) that is configured to admit a virtual light beam <NUM> from a light source <NUM> for propagation by TIR. In the system <NUM> depicted in <FIG>, the light source <NUM> is disposed to the side of the LOE <NUM>.

The OPE <NUM> is a DOE (e.g., a linear grating) that is slanted in the lateral plane (i.e., perpendicular to the light path) such that a virtual light beam <NUM> that is propagating through the system <NUM> will be deflected by <NUM> degrees laterally. The OPE <NUM> is also partially transparent and partially reflective along the light path, so that the light beam <NUM> partially passes through the OPE <NUM> to form multiple (e.g., eleven) beamlets <NUM>'. In the depicted system <NUM>, the light path is along an X axis, and the OPE <NUM> configured to bend the beam lets <NUM>' to the Y axis.

The EPE <NUM> is a DOE (e.g., a linear grating) that is slanted in a Z plane (i.e., normal to the X and Y directions) such that the beamlets <NUM>' that are propagating through the system <NUM> will be deflected by <NUM> degrees in the Z plane and toward a user's eye. The EPE <NUM> is also partially transparent and partially reflective along the light path (the Y axis), so that the beamlets <NUM>' partially pass through the EPE <NUM> to form multiple (e.g., seven) beamlets <NUM>'. Only select beams <NUM> and beamlets <NUM>' are labeled for clarity.

The OPE <NUM> and the EPE <NUM> are both also at least partially transparent along the Z axis to allow real-world light (e.g., reflecting off real-world objects) to pass through the OPE <NUM> and the EPE <NUM> in the Z direction to reach the user's eyes. For AR systems <NUM>, the ICG <NUM> is at least partially transparent along the Z axis also at least partially transparent along the Z axis to admit real-world light. However, when the ICG <NUM>, OPE <NUM>, or the EPE <NUM> are transmissive diffractive portions of the LOE <NUM>, they may unintentionally in-couple real-world light may into the LOE <NUM>. As described above this unintentionally in-coupled real-world light may be out-coupled into the eyes of the user forming ghost artifacts.

<FIG> depicts another optical system <NUM> including an LOE <NUM> having an ICG <NUM>, an OPE <NUM>, and an EPE <NUM>. The system <NUM> also includes a light source <NUM> configured to direct a virtual light beam <NUM> into the LOE <NUM> via the ICG <NUM>. The light beam <NUM> is divided into beamlets <NUM>' by the OPE <NUM> and the EPE <NUM> as described with respect to <FIG> above. Further, as the beamlets <NUM>' propagate through the EPE <NUM>, they also exit the LOE <NUM> via the EPE <NUM> toward the user's eye. Only select beams <NUM> and beamlets <NUM>' are labeled for clarity.

<FIG> depicts an optical system <NUM> including a plurality (e.g., four) of LOEs <NUM>, each having an ICG <NUM>, an OPE <NUM>, and an EPE <NUM>. Each of the plurality of LOEs <NUM> can be configured to deliver light to a user's eye such that the light has a particular color and/or appears to originate from a particular depth plane. The system <NUM> also includes a light source <NUM> configured to direct a virtual light beam <NUM> into a light distributor <NUM>. The light distributor <NUM> is configured to divide the light beam <NUM> into a plurality (e.g., four) of beamlets <NUM>' and to direct the beamlets <NUM>' toward respective shutters <NUM> and respective ICGs <NUM> behind the shutters <NUM>.

The light distributor <NUM> has a plurality (e.g., four) of beam splitters <NUM>. The beam splitters <NUM> can be of any type, including, but not limited to, partially reflective beam splitters, dichroic beam splitters (e.g., dichroic mirror prisms), and/or polarizing beam splitters, such as wire-grid beam splitters. In the system <NUM> depicted in <FIG>, only one shutter <NUM> is open to allow only one beamlet <NUM>' to address its respective ICG <NUM> and propagate through its respective LOE <NUM> by TIR. The beam splitters <NUM> and shutters <NUM> are depicted schematically in <FIG> without specifying a configuration to illustrate the function of optical system <NUM>. The examples described below include specific optical element configurations that address various issues with optical systems.

The beamlet <NUM>' is further divided into beamlets <NUM>' by the OPE <NUM> and the EPE <NUM> as described above with respect to <FIG>. The beamlets <NUM>' also exit the LOE <NUM> via the EPE <NUM> toward the user's eye as described above. Only select duplicate system components, beams <NUM> and beamlets <NUM>' are labeled for clarity.

Further, the ICG <NUM> is depicted on the top surface of the top LOE <NUM> and on the sides of each of the four LOEs <NUM> in the system <NUM>. This side view demonstrates that the ICG <NUM> of each of the stack of LOEs <NUM> is disposed in a different location on the face of its LOE <NUM> to allow each ICG <NUM> in the stack of LOEs <NUM> to be addressed by a separate beam splitter <NUM> in the distribution device. Because each beam splitter <NUM> is separated by its respective ICG <NUM> by a controllable shutter, the system <NUM> can select one LOE <NUM> to be illuminated by a beamlet <NUM>' at a particular time. While the locations of the schematically illustrated shutters <NUM> and ICGs <NUM> appear to vary only along the X axis, the locations can vary along any spatial axis (X, Y, or Z).

<FIG> depicts an optical system <NUM> according to one example, which includes a plurality (e.g., five) of LOEs <NUM>, each having an ICG <NUM>, an OPE <NUM>, and an EPE <NUM>. Each of the plurality of LOEs <NUM> can be configured to deliver light to a user's eye such that the light has a particular color and/or appears to originate from a particular depth plane. The system <NUM> also includes a light source <NUM> configured to direct a virtual light beam <NUM> into a light distributor <NUM>. The light distributor <NUM> is configured to divide the light beam <NUM> into a plurality (e.g., five) of beamlets <NUM>' and to direct the beamlets <NUM>' toward respective shutters <NUM> and respective ICGs <NUM> behind the shutters <NUM>.

The light distributor <NUM> depicted in <FIG> is an integral optical element having an ICG <NUM> and a plurality (e.g., five) of out-coupling gratings <NUM> ("OCG"). The ICG <NUM> is configured to in-couple a virtual light beam <NUM> from the light source <NUM> such that it propagates by substantially TIR in the light distributor <NUM>. The OCGs can be dynamic gratings (e.g., PDLC) or static gratings. The OCGs <NUM> are disposed serially along the longitudinal axis and TIR light path of the light distributor <NUM>. Each of the OCGs is configured to direct a portion (e.g., a beamlet <NUM>') of the light beam <NUM> near a tangent to the light distributor <NUM> and out of the light distributor <NUM> and toward a respective ICG <NUM> in a respective LOE <NUM>. Another portion of the beam <NUM> reflects off of the OCG <NUM> at a more oblique angle, and continues to propagate through the light distributor by substantially TIR. This other portion of the beam <NUM> interacts with the remaining plurality of OCGs <NUM>, which correspond to each of the LOEs <NUM> in the system <NUM>.

Like the system <NUM> depicted in <FIG>, the system <NUM> depicted in <FIG> also includes a plurality (e.g., five) of shutters <NUM> separating the light distributor <NUM> from respective ICGs <NUM>. While the locations of the schematically illustrated OCGs <NUM>, shutters <NUM>, and ICGs <NUM> appear to vary only along the X axis, the locations can vary along any spatial axis (X, Y, or Z).

As described above, the light distributor <NUM> is configured to divide the virtual light beam <NUM> into a plurality (e.g., five) of beamlets <NUM>'. While each OCG <NUM> depicted in <FIG> redirects a beamlet <NUM>' toward an opposite side of the light distributor <NUM> for exit, an OCG <NUM> may also allow a beamlet <NUM>' to exit therethrough in other examples. In such examples, the OCGs <NUM> can be disposed on the surface of the light distributor adjacent the shutters <NUM> and LOEs <NUM>. In the system <NUM> depicted in <FIG>, only one shutter <NUM> is open to allow only one beamlet <NUM>' to address its respective ICG <NUM> and propagate through its respective LOE <NUM> by TIR. However, the other beamlets <NUM>' are depicted as passing through their respective closed shutters <NUM> to illustrate their paths.

Further, the ICG <NUM> is depicted on the top surface of the top LOE <NUM> and on the sides of all on the LOEs <NUM>. This side view demonstrates that the ICG <NUM> of each of the stack of LOEs <NUM> is disposed in a different location on the face of its LOE <NUM> to allow each ICG <NUM> in the stack of LOEs <NUM> to be addressed by a separate beam splitter <NUM> in the distribution device. Because each beam splitter <NUM> is separated by its respective ICG <NUM> by a controllable shutter, the system <NUM> can select one LOE <NUM> to be illuminated by a beamlet <NUM>' at a particular time.

The system depicted in <FIG> also includes an optional focusing optical element <NUM>, which addresses the second encounter problem described above, by focusing the diverging beamlets <NUM>' at an LOE <NUM> between the light distributor <NUM> and the corresponding ICG <NUM> in the corresponding LOE <NUM>. Focusing the diverging beamlets <NUM>' at the focusing optical element <NUM> causes the beamlets <NUM>' to converged onto the ICG <NUM>, thereby reducing the size of the ICG <NUM> required to in-couple the full range of beamlets <NUM>' delivered by the light distributor <NUM>.

<FIG> depicts an optical system <NUM> according to another example, which includes a plurality (e.g., four) of LOEs <NUM>, each having an ICG <NUM>, an OPE <NUM>, and an EPE <NUM>. Each of the plurality of LOEs <NUM> can be configured to deliver light to a user's eye such that the light has a particular color and/or appears to originate from a particular depth plane. The system <NUM> also includes a light source <NUM> configured to direct a virtual light beam <NUM> into a light distributor <NUM>. The light distributor <NUM> is configured to divide the light beam <NUM> into a plurality (e.g., four) of beamlets <NUM>', and to direct the beamlets <NUM>' toward respective shutters <NUM> and respective ICGs <NUM> behind the shutters <NUM>.

The light distributor <NUM> has a plurality (e.g., five) of beam splitters <NUM> arranged in an "L" shape. The "L" shape is formed from an in-coupling beam splitter <NUM> and two "arms" <NUM> connected thereto. Each of the arms <NUM> includes two beam splitters <NUM>. The beam splitters <NUM> in the arms <NUM> can be of any type, including, but not limited to, partially reflective beam splitters, dichroic beam splitters (e.g., dichroic mirror prisms), or polarizing beam splitters, such as a wire-grid beam splitter. Dichroic and polarizing beam splitters separate light based on wavelength (i.e., color) and polarization, respectively. While the in-coupling beam splitter <NUM> in this example is a partially reflective beam splitter (e.g., <NUM>% reflective and <NUM>% transmissive), the in-coupling beam splitter <NUM> in other examples can be dichroic or polarizing beam splitters.

The in-coupling beam splitter <NUM> is configured to admit the virtual light beam <NUM> from the light source <NUM>, and divide it into two beamlets <NUM>' for propagation by TIR along the two arms <NUM>. The two beamlets <NUM>' propagate through the arms <NUM> and interact with the beam splitters <NUM> therein in a similar fashion to as the beam <NUM> interacts with the beam splitters <NUM> in the light distributor <NUM> depicted in <FIG>. While the shutters <NUM> in <FIG> are depicted as closed, they are configured to open one at a time to allow only one beamlet <NUM>' to address its respective ICG <NUM> and propagate through its respective LOE <NUM> by TIR. In the LOE <NUM>, the beamlet <NUM>' is further divided into beamlets <NUM>' by the OPE <NUM> and the EPE <NUM> as described above with respect to <FIG>. The beamlets <NUM>' also exit the LOE <NUM> via the EPE <NUM> toward the user's eye as described above. Only select duplicate system components, beams <NUM> and beamlets <NUM>' are labeled for clarity. Because each beam splitter <NUM> is separated by its respective ICG <NUM> by a controllable shutter, the system <NUM> can select one LOE <NUM> to be illuminated by a beamlet <NUM>' at a particular time.

The "L" shape of the light distributor <NUM> depicted in <FIG> results in the positioning of the shutters <NUM> in an approximate "L" shape in the system <NUM> depicted in <FIG>. The "L" shape of the light distributor <NUM> also results in the positioning of the ICGs <NUM> in an approximate "L" shape in the system <NUM> depicted in <FIG>. The "L" shape depicted in <FIG> is a more compact spatial distribution of ICGs <NUM> compared to the linear shape depicted in <FIG>. The "L" shape also provides fewer opportunities for inadvertent in-coupling of light from adjacent ICGs <NUM>. Both of these features are evident from <FIG>, which is a top view of the light distributor <NUM> depicted in <FIG>.

<FIG> is a top view of the light distributor <NUM> according to still another example. In the light distributor <NUM> the in-coupling beam splitter <NUM> and the beam splitters <NUM> that form the arms <NUM> are of different sizes. The larger beam splitters <NUM>, <NUM> can accommodate light having larger scan angles and concomitant larger FOVs. The size of the beam splitters <NUM> can be optimized based on the scan angle requirements of the LOE <NUM> corresponding to the beam splitter <NUM>. For instance, the system <NUM> and/or beam splitter <NUM> sizes can be optimized by balancing at least the following scan angle considerations/metrics: the number and size of LOEs <NUM> in the system <NUM>; maximizing FOV size; maximizing exit pupil size; reducing second encounter problem (e.g., by reducing ICG <NUM> size).

The shapes of the light distributors <NUM> in <FIG> require corresponding arrangements of shutters <NUM> and ICGs in the LOEs <NUM> of the systems <NUM>. Also, the shapes of the light distributors <NUM> result in particular positional relationships between the light sources <NUM> and the light distributors <NUM>, which in turn result in corresponding overall system profiles.

<FIG> depicts an optical system <NUM> according to yet another example. The system <NUM> in <FIG> is almost identical to the one depicted in <FIG>. The difference is the addition of a second in-coupling beam splitter <NUM>'. The second in-couple beam splitter <NUM>' is configured to allow the light source <NUM> to address the light distributor <NUM> from below the plane of the light distributor <NUM> instead of in the plane of the light distributor <NUM>, as in <FIG>. This design change allows the light source <NUM>, which may be sizeable in some examples, to be located in a different position in the system <NUM>.

<FIG> schematically depicts an optical system <NUM> according to another example. In this example, the light distributor <NUM> is formed of beam splitters <NUM> having different sizes, which allows optimization of the system <NUM> according to the scan angle requirements of the LOE <NUM> corresponding to the beam splitter <NUM>. In some examples, the system <NUM> and/or beam splitter <NUM> sizes can be optimized by balancing at least the following scan angle considerations/metrics: the number and size of LOEs <NUM> in the system <NUM>; maximizing FOV size; maximizing exit pupil size; reducing second encounter problem (e.g., by reducing ICG <NUM> size). For instance, a first beam splitter <NUM>-<NUM> is a cube with a side length of <NUM>. The corresponding first shutter <NUM>-<NUM> has a length of <NUM>. A second beam splitter <NUM>-<NUM> is a cube with a side length of <NUM>. The corresponding second shutter <NUM>-<NUM> has a length of <NUM>. A third beam splitter <NUM>-<NUM> is a cube with a side length of <NUM>. The corresponding third shutter <NUM>-<NUM> has a length of <NUM>. A fourth beam splitter <NUM>-<NUM> is a cube with a side length of <NUM>. The corresponding fourth shutter <NUM>-<NUM> has a length of <NUM>.

The system <NUM> also includes respective pluralities (e.g., four) of LOEs <NUM> and ICGs <NUM> corresponding thereto. As shown in <FIG>, the size (e.g., length) of the shutters <NUM> and ICGs <NUM> are a function of the distances between (<NUM>) the light source <NUM> and the corresponding beam splitter <NUM> and (<NUM>) the corresponding beam splitter and the corresponding ICG <NUM>. This is because these distances will determine whether the virtual light beams <NUM> and beamlets <NUM>' are converging or diverging when they interact with the beam splitter <NUM>, the shutter <NUM>, and ICGs <NUM>. Only select beams <NUM> and beamlets <NUM>' are labeled for clarity. While the shutters <NUM> in <FIG> are depicted as closed, they are configured to open one at a time to allow only one beamlet <NUM>' to address its respective ICG <NUM> and propagate through its respective LOE <NUM> by TIR. The beamlets <NUM>' in <FIG> are depicted as passing through their respective closed shutters <NUM> to illustrate their paths.

<FIG> schematically depicts an optical system <NUM> according to still another example. Like the light distributor depicted in <FIG>, the light distributor <NUM> depicted in <FIG> is formed of beam splitters <NUM> having different sizes, which allows optimization of the system <NUM> according to the scan angle requirements of the LOE <NUM> corresponding to the beam splitter <NUM>. For instance, the system <NUM> and/or beam splitter <NUM> sizes can be optimized by balancing at least the following scan angle considerations/metrics: the number and size of LOEs <NUM> in the system <NUM>; maximizing FOV size; maximizing exit pupil size; reducing second encounter problem (e.g., by reducing ICG <NUM> size). Unlike the system <NUM> depicted in <FIG>, the system <NUM> depicted in <FIG> includes LOEs <NUM> and shutters <NUM> disposed on opposite sides of the beam splitters <NUM>. This configuration shortens the light path for some LOEs <NUM>, thereby reducing the size of the corresponding ICGs <NUM> for diverging light beamlets <NUM>'. Reducing the size of ICGs <NUM> improves optical efficiency by avoiding the second encounter problem. Disposing LOEs <NUM> (and shutters <NUM>) on opposite sides of the beam splitters <NUM> requires some of the beam splitters <NUM>-<NUM>, <NUM>-<NUM> to direct light in a first orthogonal direction and other beam splitters <NUM>-<NUM>, <NUM>-<NUM> to direct light in a second orthogonal direction opposite.

Only select beams <NUM> and beamlets <NUM>' in <FIG> are labeled for clarity. While the shutters <NUM> in <FIG> are depicted as closed, they are configured to open one at a time to allow only one beamlet <NUM>' to address its respective ICG <NUM> and propagate through its respective LOE <NUM> by TIR. The beamlets <NUM>' in <FIG> are depicted as passing through their respective closed shutters <NUM> to illustrate their paths.

<FIG> depicts an optical system <NUM> according to an example whereas <FIG> depicts an optical system <NUM> according to an embodiment. The systems <NUM> depicted in <FIG> are similar to the systems <NUM> depicted in <FIG> and <FIG>, because the systems <NUM> depicted in <FIG>, <FIG>, <FIG> each have four LOEs <NUM>. The differences in the systems <NUM> are driven by the different configurations of the light distributors <NUM> therein. The light distributor <NUM> in <FIG> has two parallel arms <NUM> (formed of beam splitters <NUM>) that are connected by an in-coupling beam splitter <NUM> and offset from each other in the X and Y axes. The light distributor <NUM> in <FIG> has two perpendicular arms <NUM> (formed of beam splitters <NUM>) that are connected by an in-coupling beam splitter <NUM> and offset from each other in the Y axis.

The different configurations of the light distributors <NUM> in <FIG> lead to differences in the configurations of the shutters <NUM> (only shown in <FIG>) and LOEs <NUM>. The different light distributor <NUM>, shutter <NUM>, and LOE <NUM> configurations can be used to customize the three dimensional footprint of the optical system <NUM> to provide a particular device form factor. Only select system components, beams <NUM> and beamlets <NUM>' are included and labeled in <FIG> for clarity. While the shutters <NUM> in <FIG> are depicted as closed, they are configured to open one at a time to allow only one beamlet <NUM>' to address its respective ICG <NUM> and propagate through its respective LOE <NUM> by TIR.

<FIG> schematically depicts an optical system <NUM> according to another example, which has a plurality (e.g., five) LOEs <NUM>. The system <NUM> depicted in <FIG> is similar to the system <NUM> depicted in <FIG> because the system <NUM> includes LOEs <NUM> and shutters <NUM> disposed on opposite sides of the beam splitters <NUM>. As described above, this configuration shortens the light path for some LOEs <NUM>, thereby reducing the size of the corresponding ICGs <NUM> for diverging light beamlets <NUM>' and reducing the second encounter problem.

The main difference between the systems <NUM> depicted in <FIG> and <FIG> is that the light distributor <NUM> depicted in <FIG> is an integral optical element instead of a plurality of beam splitters <NUM>, as shown in <FIG>. The light distributor <NUM> in <FIG> includes an irregularly shaped DOE <NUM> that is configured to divide the virtual light beam <NUM> into a plurality (e.g., five) beamlets <NUM>' and to direct those beamlets <NUM>' toward respective shutters <NUM> and respective ICGs <NUM> behind the shutters <NUM>. Portions of the irregularly shaped DOE <NUM> are configured to direct beamlets <NUM>' having a larger size or scanning angle, thereby increasing the resolution of the system <NUM>.

Only select system components, beams <NUM> and beamlets <NUM>' are included and labeled in <FIG> for clarity. While the shutters <NUM> in <FIG> are depicted as closed, they are configured to open one at a time to allow only one beamlet <NUM>' to address its respective ICG <NUM> and propagate through its respective LOE <NUM> by TIR.

<FIG> depicts an optical system <NUM> according to another embodiment. <FIG> depict an optical system <NUM> and light distributors <NUM> located therein according to other examples. The systems <NUM> and light distributors <NUM> depicted in <FIG> are similar to the systems <NUM> and light distributors <NUM> depicted in <FIG>, <FIG>, <FIG>, however the systems <NUM> each have different light distributor <NUM> and LOE <NUM> configurations. The systems <NUM> and light distributors <NUM> depicted in <FIG> are similar to each other because they all accommodate six channels for six LOEs. Since three single-color LOEs <NUM> are required to display a color image at a single depth plane, the six LOEs <NUM> of these systems <NUM> can display color images at two depth planes.

The differences in the systems <NUM> depicted in <FIG> (and <FIG>, <FIG>, <FIG>) are driven by the different configurations of the light distributors <NUM> therein. The light distributor <NUM> in <FIG> has three arms <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (formed of beam splitters <NUM>) that are connected by two in-coupling beam splitters <NUM>. Two of the arms <NUM>-<NUM>, <NUM>-<NUM> are parallel but offset from each other in the Y and Z axes. The other arm <NUM>-<NUM> is perpendicular to the first two arms <NUM>-<NUM>, <NUM>-<NUM> and offset from the other two arms <NUM>-<NUM>, <NUM>-<NUM> in the X and Y axes. The beam splitters <NUM> in the arms <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> can be of any type, including, but not limited to, partially reflective beam splitters, dichroic beam splitters (e.g., dichroic mirror prisms), or polarizing beam splitters, such as a wire-grid beam splitter. While the in-coupling beam splitters <NUM> in this embodiment are partially reflective beam splitters, the in-coupling beam splitter <NUM> in other embodiments can be dichroic or polarizing beam splitters.

The light distributor <NUM> in <FIG> has two arms <NUM>-<NUM>, <NUM>-<NUM> (formed of beam splitters <NUM>) that are connected by an in-coupling beam splitter <NUM>. The arms <NUM>-<NUM>, <NUM>-<NUM> are disposed on one axis with the in-coupling beam splitter <NUM> therebetween. The in-coupling beam splitter <NUM> is an X-cube beam splitter configured to direct half of the light beam <NUM> into the first arm <NUM>-<NUM> and the other half into the second arm <NUM>-<NUM>. Some of the beam splitters <NUM> in the arms <NUM>-<NUM>, <NUM>-<NUM> can be polarizing beam splitters configured to redirect only one color of light based on it polarization.

For instance, the first beam splitter <NUM>-<NUM> adjacent the in-coupling beam splitter <NUM> (in each of the first and second arms <NUM>-<NUM>, <NUM>-<NUM>) can be configured to redirect green light (with <NUM> degrees polarization) out of the beam splitter <NUM>-<NUM> while allowing red and blue (each with <NUM> degrees polarization) light to proceed through the beam splitter <NUM>-<NUM>. A retardation filter <NUM> is disposed between the first beam splitter <NUM>-<NUM> and the second beam splitter <NUM>-<NUM>. The retardation filter <NUM> is configured to change the polarization of only the red light from <NUM> degrees to <NUM> degrees, leaving the blue light with <NUM> degrees polarization. The second beam splitter <NUM>-<NUM> can be configured to redirect red light (with <NUM> degrees polarization after passing through retardation filter <NUM>) out of the beam splitter <NUM>-<NUM> but allow blue (with <NUM> degrees polarization) light to proceed through the beam splitter <NUM>-<NUM>. The third "beam splitter" <NUM>-<NUM> can be replaced with a simple <NUM> degree mirror. Alternatively, the third beam splitter <NUM>-<NUM> can be dichroic beam splitter configured to redirect blue light out of the beam splitter <NUM>-<NUM>.

The light distributor <NUM> in <FIG> has three arms <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (formed of beam splitters <NUM>) that are connected by an in-coupling beam splitter <NUM>. The arms <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> form a "T" shape rotated <NUM> degrees counterclockwise with the in-coupling beam splitter <NUM> at the junction of the "T" shape. The in-coupling beam splitter <NUM> is a dichroic beam splitter or dichroic mirror prism configured to direct red light into the first arm <NUM>-<NUM> and blue light into the third arm <NUM>-<NUM>, and to allow green light to pass through into the second arm <NUM>-<NUM>. Each beam splitter <NUM> can be partially reflective to direct a portion of the colored light out of the beam splitter and into the corresponding LOE (not shown).

The dichroic beam splitters, dichroic mirror prisms, polarization beam splitters, and retardation filters can be used to design various light distributors <NUM> configured to generate beam lets <NUM>' with a particular color.

The different configurations of the light distributors <NUM> in <FIG> lead to differences in the configurations of the shutters <NUM> and LOEs <NUM> (only shown in <FIG>). The different light distributor <NUM>, shutter <NUM>, and LOE <NUM> configurations can be used to customize the three dimensional footprint of the optical system <NUM> to provide a particular device form factor. Only select system components, beams <NUM> and beamlets <NUM>' are included and labeled in <FIG> for clarity. While the shutters <NUM> in <FIG> are depicted as closed, they are configured to open one at a time to allow only one beamlet <NUM>' to address its respective ICG <NUM> and propagate through its respective LOE <NUM> by TIR.

<FIG> depict an optical system <NUM>, from perspective, top, and side views respectively, according to another example. The system <NUM> and light distributor <NUM> depicted in <FIG> are similar to the systems <NUM> and light distributors <NUM> depicted in <FIG>, <FIG>, <FIG>, and <FIG>, however the systems <NUM> each have different light distributor <NUM> and LOE <NUM> configurations. The systems <NUM> and light distributors <NUM> depicted in <FIG> are similar to those depicted in <FIG> because they all accommodate six channels for six LOEs.

The light distributor <NUM> depicted in depicted in <FIG> has two arms <NUM>-<NUM>, <NUM>-<NUM> (formed of beam splitters <NUM>) that are connected by two in-coupling beam splitters <NUM>. The arms <NUM>-<NUM>, <NUM>-<NUM> are parallel but offset from each other in the Z axis. The in-coupling beam splitters <NUM> are partially reflective beam splitters configured to direct half of the light beam <NUM> into the first arm <NUM>-<NUM> and the other half into the second arm <NUM>-<NUM>. The second in-coupling "beam splitter" <NUM> can be replaced with a simple <NUM> degree mirror. Some of the beam splitters <NUM> in the arms <NUM>-<NUM>, <NUM>-<NUM> can be polarizing beam splitters configured to redirect only one color of light based on it polarization.

For instance, a first retardation filter <NUM> is disposed between the in-coupling beam splitters <NUM> and the first beam splitter <NUM>-<NUM>. The first retardation filter <NUM> is configured to change the polarization of red and blue light from <NUM> degrees to <NUM> degrees, while leaving the polarization of green light at <NUM> degrees. The first beam splitter <NUM>-<NUM> adjacent the in-coupling beam splitter <NUM> and the first retardation filter <NUM> can be configured to redirect green light (with <NUM> degrees polarization) out of the beam splitter <NUM>-<NUM> but allow red and blue (each with <NUM> degrees polarization) light to proceed through the beam splitter <NUM>-<NUM>.

A second retardation filter <NUM> is disposed between the first beam splitter <NUM>-<NUM> and the second beam splitter <NUM>-<NUM>. The second retardation filter <NUM> is configured to change the polarization of only red light from <NUM> degrees to <NUM> degrees, leaving blue light with <NUM> degrees polarization. The second beam splitter <NUM>-<NUM> can be configured to redirect red light (with <NUM> degrees polarization after passing through second retardation filter <NUM>) out of the beam splitter <NUM>-<NUM> but allow blue light (with <NUM> degrees polarization) to proceed through the beam splitter <NUM>-<NUM>. The third "beam splitter" <NUM>-<NUM> can be a simple <NUM> degree mirror. Alternatively, the third beam splitter <NUM>-<NUM> can be dichroic beam splitter configured to redirect blue light out of the beam splitter <NUM>-<NUM>. A half-wave plate <NUM> is disposed between the third beam splitter <NUM>-<NUM> and the LOE <NUM> to restore the blue light to <NUM> degrees polarization. The beam splitters <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in both the first and second arms <NUM>-<NUM>, <NUM>-<NUM> function in a similar manner.

<FIG> depicts an optical system <NUM> according to another example. The system <NUM> depicted in <FIG> is similar to the system <NUM> depicted in <FIG>, however the light distributors <NUM> in the systems <NUM> have beam splitters <NUM> with different aspect ratios. The beam splitters <NUM> depicted in <FIG> are cubes with equal sides (e.g., <NUM>). The beam splitters <NUM> depicted in <FIG> are <NUM> by <NUM> by <NUM>. The <NUM> size in the Z direction means that the faces of the beam splitters <NUM> through which light is directed (i.e., the Y-Z plane and the X-Z plane) have a <NUM> by <NUM> aspect ratio. This aspect ratio provides a directional increase in scan angle.

<FIG> depicts a light distributor <NUM> similar to the one depicted in <FIG> in that the beam splitters <NUM> in both light distributors <NUM> have a <NUM> by <NUM> aspect ratio. However, while the two in-coupling beam splitters <NUM> in <FIG> are effectively the same size, the two in-coupling beam splitters <NUM> in <FIG> have different sizes. For instance, the first in-coupling beam splitter <NUM>-<NUM> in <FIG> is <NUM> x <NUM> x <NUM>, and the second in-coupling beam splitter <NUM>-<NUM> is <NUM> x <NUM> x <NUM>. Changing the size of the in-coupling beam splitters <NUM> changes the scan angles of the two arms <NUM>-<NUM>, <NUM>-<NUM>.

<FIG> depicts an optical system <NUM> according to another example. The system <NUM> includes a plurality of LOEs <NUM>, first and second light distributors <NUM>-<NUM>, <NUM>-<NUM>, and a dual beam light source <NUM>. The dual beam light source <NUM> is configured to divide a single virtual light beam <NUM> into two spatially separated beamlets <NUM>' that can be directed into first and second light distributors <NUM>-<NUM>, <NUM>-<NUM>, respectively. The dual beam light source <NUM> includes two beam splitters <NUM>, two shutters <NUM>, and various focusing optical elements <NUM>. The beam splitters <NUM> can be of any type, including, but not limited to, partially reflective beam splitters, dichroic beam splitters (e.g., dichroic mirror prisms), or polarizing beam splitters, such as a wire-grid beam splitter. Moving two beam splitters <NUM> and shutters <NUM> from the light distributor <NUM> into the light source <NUM>, and splitting one light distributor <NUM> into two light distributors <NUM>-<NUM>, <NUM>-<NUM> changes the overall system configuration and form factor.

<FIG> depicts a plurality of LOEs <NUM> and two light distributors <NUM>-<NUM>, <NUM>-<NUM> according to another example and configured for use with the system <NUM> depicted in <FIG>. The light distributors <NUM>-<NUM>, <NUM>-<NUM> in <FIG> include respective in-coupling beam splitters <NUM> that are larger than the size of the beam splitters forming the light distributors <NUM>-<NUM>, <NUM>-<NUM> to allow larger scan angles.

<FIG> schematically depicts an optical system <NUM> according to yet another example. This system <NUM> combines the red and blue light into one LOE <NUM> to reduce the number of LOEs <NUM> needed to render an acceptable color image at one depth plane from three to two. Accordingly, the system <NUM> depicted in <FIG> generates acceptable full color images at four depth planes using eight LOEs <NUM> instead of twelve. This reduction in the number of LOEs <NUM> and corresponding optical elements (e.g., lenses, beam splitters <NUM>, shutters <NUM>, etc.) reduces the overall size of the system <NUM>.

<FIG> depicts an optical system <NUM> according to another example. The system <NUM> depicted in <FIG> addresses the inadvertent out-coupling problem. The system <NUM> includes a light source <NUM> and three LOEs <NUM>. The light source <NUM> is configured to direct a virtual light beam <NUM> toward an ICG <NUM> of a first LOE <NUM>-<NUM>. While the ICG <NUM> is configured to direct the beam <NUM> into the first LOE <NUM>-<NUM> to propagate by TIR therethrough, only a first portion of the beam <NUM>' is directed into the first LOE <NUM>-<NUM>. Because ICG <NUM> efficiency is less than <NUM>% (e.g., <NUM>%), a second portion of the beam <NUM>" passes through the ICG <NUM> and out of the first LOE <NUM>-<NUM>. This second portion of the beam <NUM>" can escape the system <NUM>, as shown by the dotted line <NUM>"' in <FIG>, thereby reducing optical efficiency and beam density.

The system <NUM> in <FIG> addresses this problem by disposing a mirror coating <NUM> on the other side of the light source <NUM> from the ICG <NUM>. In particular, the mirror coating <NUM> is disposed on the side of a second LOE <NUM>-<NUM> that is closest to the ICG <NUM>. The mirror coating <NUM> and the ICG <NUM> are configured such that the second portion of the beam <NUM>" reflects off of the mirror coating <NUM> and re-enters the ICG <NUM> of the first LOE <NUM>-<NUM>. This light <NUM>" is in-coupled into the first LOE <NUM>-<NUM> and propagates therethrough by TIR, thereby increasing the optical efficiency and beam density of the system <NUM>.

While some embodiments are described as using retardation filters <NUM>, polarizing beam splitters <NUM>, and half-wave plates <NUM> to configure light distributors <NUM> for redirection light of different colors, the specific embodiments are only illustrative and not meant to be limiting. Accordingly, such light distributors <NUM> can be configured to output colored light in any color order.

While some embodiments are described as having four channels, those systems can still be used to render acceptable full color virtual images at two depth planes because blue and red light can be delivered using the same channel to two LOEs. Optical systems using a single blue/red channel design to reduce the number of components are described in the above-referenced <CIT>. Using this design, two channels (Green and Red/Blue) can be used to render an acceptable full color virtual image at one depth plane.

The above-described AR systems are provided as examples of various optical systems that can benefit from more selectively reflective optical elements. Accordingly, use of the optical systems described herein is not limited to the disclosed AR systems, but rather applicable to any optical system.

Various exemplary embodiments of the invention are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate more broadly applicable aspects of the invention. Various changes may be made to the invention described without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s) or scope of the present invention. Further, as will be appreciated by those with skill in the art that each of the individual variations described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope of the present inventions. All such modifications are intended to be within the scope of claims associated with this disclosure.

The invention includes methods that may be performed using the subject devices. The methods may comprise the act of providing such a suitable device. Such provision may be performed by the end user. In other words, the "providing" act merely requires the end user obtain, access, approach, position, setup, activate, power-up or otherwise act to provide the requisite device in the subject method. Methods recited herein may be carried out in any order of the recited events which is logically possible, as well as in the recited order of events.

Exemplary aspects of the invention, together with details regarding material selection and manufacture have been set forth above. As for other details of the present invention, these may be appreciated in connection with the above-referenced patents and publications as well as generally known or appreciated by those with skill in the art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference to several examples optionally incorporating various features, the invention is not to be limited to that which is described or indicated as contemplated with respect to each variation of the invention. Various changes may be made to the invention described whether recited herein or not included for the sake of some brevity without departing from the scope of the invention. In addition, where a range of values is provided, it is understood that every intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention.

Without the use of such exclusive terminology, the term "comprising" in claims associated with this disclosure shall allow for the inclusion of any additional element--irrespective of whether a given number of elements are enumerated in such claims, or the addition of a feature could be regarded as transforming the nature of an element set forth in such claims. Except as specifically defined herein, all technical and scientific terms used herein are to be given as broad a commonly understood meaning as possible while maintaining claim validity.

The breadth of the present invention is not to be limited to the examples provided and/or the subject specification, but rather only by the scope of claim language associated with this disclosure.

Claim 1:
An imaging system (<NUM>), comprising:
a light source (<NUM>) configured to generate a light beam (<NUM>);
a first light guiding optical element (<NUM>) including a first entry portion and configured to propagate at least a first portion of the light beam (<NUM>) by total internal reflection;
a second light guiding optical element (<NUM>) including a second entry portion and configured to propagate at least a second portion of the light beam (<NUM>) by total internal reflection; and
a light distributor (<NUM>) including a light distributor entry portion, a first exit portion on a first arm (<NUM>) and a second exit portion on a second arm (<NUM>), the light distributor configured to direct at least the first and second portions of the light beam (<NUM>) into the first and second light guiding optical elements (<NUM>), respectively,
wherein the light distributor entry portion is disposed between the first and second exit portions,
characterized in that
the first arm (<NUM>) is perpendicular to the second arm (<NUM>), and
the first and second arms (<NUM>) are separated from each other along an axis orthogonal to both respective first and second axes of the first and second arms (<NUM>).