RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of provisional patent application serial number 62/065,328, filed on 10/17/2014, entitled "MULTIPLE- REFLECTOR ULTRA-WIDE FIELD OF VIEW DISPLAY DEVICE," the disclosure of which is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The embodiments relate to head-wearable display devices and, in particular, to head-wearable display devices with multiple reflective surfaces that have an ultra-wide field of view and utilize a narrow-beam light source, such as a Liquid Crystal on Silicon display light source. BACKGROUND

[0003] A Liquid Crystal on Silicon (LCoS) display offers a relatively bright, high-resolution display, and thus would be a desirable source of light for an ultra- wide field of view (UWFOV) reflective surface. However, narrow-beam displays, such as an LCoS display, emit light in a relatively narrow +/- 10-degree cone. The narrowness of the beam makes it difficult or impracticable to use an LCoS display in conjunction with a UWFOV reflective surface, such as a 130-degree UWFOV reflective surface. Placing a lens in front of the narrow-beam display may diverge the light, but may not make the light field wide enough to support the parameters of a UWFOV reflective surface. In particular, because the curvature of the UWFOV reflective surface reflects the pixels of the narrow-beam display from particular points on the reflector, the resulting reflector power may be too high, resulting in the light focusing inside of an eye instead of at the fovea of the eye. SUMMARY

[0004] The embodiments relate to head-wearable display devices and, in particular, to head-wearable display devices that have an ultra-wide field of view (UWFOV) and utilize a narrow-beam light source, such as a Liquid Crystal on Silicon (LCoS) display, a digital light processing (DLP) display, or a laser display. In one embodiment, the head-wearable display device includes a frame, a narrow-beam light source fixed with respect to the frame, a UWFOV reflective surface fixed with respect to the frame, and a diverging reflective surface fixed with respect to the frame that is configured to receive light emitted from the narrow-beam light source and reflect the light toward the UWFOV reflective surface to spread the light across the UWFOV reflective surface.

[0005] In one embodiment, the narrow-beam light source comprises one of an LCoS display, a DLP display, and a laser display. In one embodiment, the head- wearable display device includes a diverging lens fixed with respect to the narrow-beam light source that is configured to receive the light emitted from the narrow-beam light source and transmit the light toward the diverging reflective surface.

[0006] In one embodiment, the UWFOV reflective surface has a field of view (FOV) greater than about 100 degrees. In another embodiment, the UWFOV reflective surface has an FOV greater than about 120 degrees, and in yet another embodiment, the UWFOV reflective surface has an FOV greater than about 140 degrees. In one embodiment, the UWFOV reflective surface is configured to substantially collimate the light. In some embodiments, the

UWFOV reflective surface converges the light in order to substantially collimate the light.

[0007] In another embodiment, a method for presenting an image to an eye is provided. Light comprising imagery is emitted from a narrow-beam light source. By way of non-limiting example, the imagery may comprise video stream imagery or a static image. A diverging reflective surface reflects the light toward a

UWFOV reflective surface. The UWFOV reflective surface reflects the light toward the eye. [0008] Those skilled in the art will appreciate the scope of the disclosure and realize additional aspects thereof after reading the following detailed description of the embodiments in association with the accompanying drawing figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0010] Figure 1 is a diagram of a head-wearable ultra-wide field of view (UWFOV) display device according to one embodiment;

[0011] Figure 2 is a flowchart of a method for presenting an image to an eye according to one embodiment;

[0012] Figure 3 is a diagram illustrating the mapping of a narrow-beam light source to a diverging reflective surface and a UWFOV reflective surface according to one embodiment;

[0013] Figure 4 is a perspective view of a user utilizing the head-wearable UWFOV display device according to another embodiment;

[0014] Figure 5 is a diagram illustrating diverging light rays being reflected into an eye with zero diopters of vergence according to one embodiment; and

[0015] Figure 6 is a diagram illustrating an example calculation for

determining a radius of curvature of a surface element of the UWFOV reflective surface to reflect and collimate light from such surface element toward a predetermined location of an eye according to one embodiment. DETAILED DESCRIPTION

[0016] The embodiments set forth below represent the information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

[0017] Any flowcharts discussed herein are necessarily discussed in some sequence for purposes of illustration, but unless otherwise explicitly indicated, the embodiments are not limited to any particular sequence of steps. The term "about" used herein in conjunction with a numeric value means any value that is within a range of ten percent greater than or ten percent less than the numeric value.

[0018] The embodiments relate to head-wearable display devices and, in particular, to head-wearable display devices that have an ultra-wide field of view (UWFOV) and utilize a narrow-beam light source, such as a Liquid Crystal on Silicon (LCoS) display, a digital light processing (DLP) display, and a laser display. The embodiments are particularly applicable to UWFOV reflective surfaces, such as those disclosed in U.S. Patent Nos. 8,625,200 and 8,781 ,794, the disclosures of which are incorporated by reference herein. The UWFOV reflective surfaces discussed herein typically, but not necessarily, have a 100- degree or greater field of view (FOV) for each eye of a user and a combined 180- degree FOV for both eyes of the user.

[0019] In order to expand a beam of the LCoS or similar microdisplay to fill a wide FOV, the image needs to be expanded and the emitted light needs to be directed into a wider area for reflection from the UWFOV reflective surface. The embodiments may utilize a non-rotationally symmetric, aspherical design due to the rectangular form of a display, and a near-to-the-eye afocal light field.

[0020] Figure 1 is a diagram of a head-wearable UWFOV display device 10 (hereinafter "UWFOV display device 10" for purposes of brevity) according to one embodiment. In this embodiment, the UWFOV display device 10 includes a frame 12 that has a form factor similar to a pair of glasses, and a user 14 wears the UWFOV display device 10 similarly to how the user 14 would wear a pair of glasses. However, the embodiments are not limited to any particular form factor and may comprise any form factor capable of holding the various components with respect to one another, and with respect to eyes 16 (only one illustrated) of the user 14. For example, in one embodiment, the UWFOV display device 10 may be coupled to a head 18 of the user 14 via straps. In another embodiment, the UWFOV display device 10 may be coupled to an apparatus that is worn on the head 18, such as a hat, or a helmet.

[0021] A UWFOV reflective surface 20 is fixed with respect to the frame 12. In one embodiment, the UWFOV reflective surface 20 may be substantially similar or identical to the reflective surfaces disclosed in U.S. Patent Nos.

8,625,200 and/or 8,781 ,794. The UWFOV reflective surface 20 may, for example, have a 100-degree or greater horizontal FOV for each eye 16 of the user 14; a 120-degree or greater horizontal FOV for each eye 16 of the user 14; or a 135-degree or greater horizontal FOV for each eye 16 of the user 14.

[0022] A narrow-beam light source 22 is fixed with respect to the frame 12. The narrow-beam light source 22 may comprise any suitable narrow-beam display or microdisplay, such as, for example, an LCoS display, a DLP display, or a laser display. In one embodiment, the microdisplay has a 4096 x 2240 pixel resolution and an area of 18.43 mm by 10.08 mm. The narrow-beam light source 22 may comprise a diagonal dimension of less than one inch, such as, by way of non-limiting example, 0.7 inches, and may emit light in a relatively narrow cone, such as a +/- 10-degree cone. In one embodiment, the narrow-beam light source 22 is mapped to the UWFOV reflective surface 20. In particular, the narrow- beam light source 22 comprises a display panel that has a plurality of pixels at a particular resolution, and the pixels are mapped to corresponding locations on the UWFOV reflective surface 20. Each location on the UWFOV reflective surface 20 is configured to reflect and collimate light emitted by the

corresponding pixels toward the eye 16 of the user 14. The UWFOV reflective surface 20 is engineered such that light received from pixels of the narrow-beam light source 22 other than the particular corresponding pixels is reflected in a direction other than the eyes 16 of the user 14.

[0023] The UWFOV display device 10 includes a diverging reflective surface 24 that is fixed with respect to the frame 12. The diverging reflective surface 24 is configured to receive light emitted from the narrow-beam light source 22 and reflect the light toward the UWFOV reflective surface 20 to spread the light completely across the UWFOV reflective surface 20. The UWFOV reflective surface 20 receives the light from the diverging reflective surface 24 and reflects those light rays that are emitted by the corresponding pixels of the narrow-beam light source 22 toward the eye 16 of the user 14. In some embodiments, the UWFOV reflective surface 20 is configured to substantially collimate the light. While for purposes of illustration only the right eye 16 of the user 14 is shown in Figure 1 , the elements illustrated in Figure 1 may be duplicated with respect to the left eye 16 of the user 14. Thus, although not illustrated, the UWFOV display device 10 may contain a pair of narrow-beam light sources 22, a pair of diverging reflective surfaces 24, and a pair of UWFOV reflective surfaces 20.

[0024] Figure 2 is a flowchart of a method for presenting an image to the eye 16 according to one embodiment. Figure 2 will be discussed in conjunction with Figure 1 . In this example, assume that the narrow-beam light source 22 emits light that comprises imagery (Figure 2, block 100). For example, the video may comprise imagery depicting a virtual environment, or the imagery may comprise one or more virtual objects that may be presented to the eye 16 positioned with respect to real-world imagery that the eye 16 concurrently views, such as in an augmented reality embodiment. The diverging reflective surface 24 reflects the light toward the UWFOV reflective surface 20 (Figure 2, block 102). The

UWFOV reflective surface 20 reflects the light toward the eye 16 (Figure 2, block 104).

[0025] The UWFOV reflective surface 20 is a non-rotationally symmetric surface and, in some embodiments, is a concave surface, that is mapped to the narrow-beam light source 22. Such mapping may be implemented as disclosed herein as well as in conjunction, for example, with mechanisms disclosed in U.S. Patent No. 8,781 ,794 (hereinafter the 794 Patent). As disclosed in the 794 Patent, non-symmetrical lens surfaces, such as the UWFOV reflective surface 20, can be engineered to, among other advantages, increase an FOV of the user 14, such that imagery presented by the narrow-beam light source 22 can be reflected from a desired surface element or surface elements of the UWFOV reflective surface 20 toward a predetermined location of the eye 16. Such surface elements may overlap one another. In one embodiment, the UWFOV reflective surface 20 comprises a plurality of different surface elements oriented to reflect and collimate light from corresponding regions of the narrow-beam light source 22 toward the predetermined location of the eye 16. The UWFOV reflective surface 20 comprises multiple, such as thousands, of different surface elements that are mapped to corresponding regions of the narrow-beam light source 22.

[0026] Figure 3 is a diagram illustrating the mapping of the narrow-beam light source 22 to the diverging reflective surface 24 and the UWFOV reflective surface 20 according to one embodiment. In particular, surface elements of the narrow-beam light source 22 are mapped to surface elements of the diverging reflective surface 24 and to surface elements of the UWFOV reflective surface 20. With respect to the narrow-beam light source 22, a surface element may comprise a pixel, or a group of pixels. With respect to the diverging reflective surface 24 and the UWFOV reflective surface 20, surface elements correspond to areas of the respective surfaces. The mapping is such that light from a particular surface element of the narrow-beam light source 22 is reflected by a corresponding surface element of the diverging reflective surface 24 to a corresponding surface element of the UWFOV reflective surface 20. The corresponding surface element of the UWFOV reflective surface 20 collimates the light and reflects the light toward a predetermined location 26 of the eye 16. There may be any number of surface elements, and, in some embodiments, there may be thousands or even hundreds of thousands of surface elements mapped among the narrow-beam light source 22, the diverging reflective surface 24, and the UWFOV reflective surface 20, depending on a number of factors, including the resolution of the display of the narrow-beam light source 22. Each of the narrow-beam light source 22, the diverging reflective surface 24, and the UWFOV reflective surface 20 may have the same number of surface elements. An example of the mapping of surface elements among the narrow-beam light source 22, the diverging reflective surface 24, and the UWFOV reflective surface 20 will now be discussed. Assume that surface elements of the narrow-beam light source 22 comprise pixels. Initially, the diverging reflective surface 24 may have a spheroidal shape of a particular radius. A line 28 is positioned between a pixel 30 of the narrow-beam light source 22 and a selected surface element 32 of the diverging reflective surface 24. A tangent 34 of the slope of the selected surface element 32 exists at the selected surface element 32. A three- dimensional (3D) normal 36 of the tangent 34 is adjusted so that the 3D normal 36 bisects the angle formed by the line 28 and a line 38 between the selected surface element 32 and a selected surface element 40 on the UWFOV reflective surface 20. This adjustment identifies a final tangent 34 of the selected surface element 32 of the diverging reflective surface 24, and thus the slope of the selected surface element 32, and thus, the diverging reflective surface 24 may ultimately become non-spheroidal.

[0027] Similarly, a 3D normal 42 at the selected surface element 40 is adjusted to bisect the angle formed by the line 38 and a line 44 from the selected surface element 40 to the predetermined location 26 of the eye 16. Once so adjusted, the slope of the selected surface element 40 is determined. This process may be repeated for each surface element of the narrow-beam light source 22 across the entire FOV to define the overall surfaces of the diverging reflective surface 24 and the UWFOV reflective surface 20. The process is iterative and may be repeated hundreds of thousands of times to define the diverging reflective surface 24 and the UWFOV reflective surface 20 with as little error as possible. During the iterations, adjustments may be made to the slopes to minimize the overall error of the system. Each surface element of the UWFOV reflective surface 20 also collimates, or substantially collimates, the light received from the corresponding surface element of the diverging reflective surface 24, and thus also includes the collimation power in the objective for the multi- objective adaptation process that occurs to create the surfaces of the diverging reflective surface 24 and the UWFOV reflective surface 20.

[0028] The system produces a point cloud representing the UWFOV reflective surface 20. For example, the point cloud may comprise 500 x 300 points situated along the UWFOV reflective surface 20 in three dimensions. This point cloud may be imported into a 3D computer-aided design (CAD) system, such as, by way of non-limiting example, Creo. The 3D CAD system may then connect all the points in the point cloud with a non-uniform rational basis spline. The connected points may then be tested in an optics test program, or converted into a physical lens with 3D printing or injection molding.

[0029] Figure 4 is a perspective view of the user 14 utilizing a multiple- reflector UWFOV display device 10-1 according to another embodiment. The UWFOV display device 10-1 is substantially similar to the UWFOV display device 10 discussed above except as otherwise discussed herein. The UWFOV display device 10-1 includes a diverging lens 45 that is fixed with respect to the narrow- beam light source 22 and that is configured to receive the light emitted by the narrow-beam light source 22 and transmit the light toward the diverging reflective surface 24. The diverging lens 45 spreads the light across the diverging reflective surface 24. The diverging lens 45 may be fixed to the frame 12, the narrow-beam light source 22, or the diverging reflective surface 24. In some embodiments, the diverging lens 45 is an achromatic lens to help avoid the separation of red, green, and blue components of the light beam.

[0030] A set of light beam characteristics defines the focal length of each aspect of the UWFOV display device 10, such that the resulting light to the eye 16 is substantially collimated, thus having zero diopters of vergence, sometimes referred to as 0D. In this regard, Figure 5 is a diagram illustrating diverging light rays 46 being reflected into an eye 16 with zero diopters of vergence according to one embodiment. The light rays 46 are emitted from a location 48 of the narrow-beam light source 22 and travel in an optical path to enter a pupil 50 of the eye 16 and form a centric 52 at the retina or fovea. The cone defined by the pupil 50 and the centric 52 at the retina or fovea is based on a pencil of light 54 that is reflected from the UWFOV reflective surface 20 after being diverged by the diverging reflective surface 24. The ability to collimate the light rays 46 to the eye 16 is provided in part by the distance D1 between the narrow-beam light source 22 and the diverging reflective surface 24, the distance D2 between the diverging reflective surface 24 and the UWFOV reflective surface 20, and the distance D3 between the UWFOV reflective surface 20 and the eye 16.

[0031] Because the UWFOV display device 10 is a near-to-the-eye system and the distance from the narrow-beam light source 22 to the eye 16 is

substantially shorter than, for example, distances utilized in a telescope system, the vergence, or diopter, of light emitted from the narrow-beam light source 22 changes rapidly throughout the UWFOV display device 10. As discussed above, in some embodiments, pixels of the narrow-beam light source 22 are mapped to corresponding locations on the UWFOV reflective surface 20, and the locations on the UWFOV reflective surface 20 are configured to reflect and collimate light emitted by the corresponding pixels toward the eye 16.

[0032] In this example, assume that light rays 46 are emitted from the location 48 of the narrow-beam light source 22. Further assume that the location 48 is mapped to a location 58 of the UWFOV reflective surface 20 via a location 59 of the diverging reflective surface 24. The vergence is defined as 1 /S, where S is expressed in meters. Thus, if the initial distance D1 is 4 cm, the light rays 46 have a vergence of -1 /0.04 = -25D for the distance D1 . The vergence is negative because the light rays 46 are diverging. If, for example, the diverging reflective surface 24 provides a further divergence of -20D by virtue of having a focal length of, for example, 5 cm, and vergence = 1 /(focal length in meters), then the current vergence of the light rays 46 is -25D + (-20 D) = -45D, since vergence is linearly additive. The light rays 46 are reflected by the diverging reflective surface 24 toward the UWFOV reflective surface 20. The location 58 of the UWFOV reflective surface 20 is configured to collimate the light rays 46 that originate from the location 48 of the narrow-beam light source 22 to bring the vergence of the light rays 46 to 0D, such that collimated light rays 46 are reflected toward the eye 16. If a lens is positioned between the narrow-beam light source 22 and the diverging reflective surface 24, the vergence of the light rays 46 will be further modified.

[0033] The UWFOV display device 10 produces a wide FOV by angling the reflecting points along the UWFOV reflective surface 20 to reflect the light from the correct pixels of the narrow-beam light source 22, which introduces a further constraint on the bending of the light rays 46, which is a function of the display width and the expected FOV.

[0034] As discussed previously, the UWFOV reflective surface 20 not only reflects light emitted from the narrow-beam light source 22 toward the

predetermined location 26 of the eye 16 but also collimates, or substantially collimates, the light so that the light can be focused by the user 14. Figure 6 is a diagram illustrating an example calculation for determining a radius of curvature of a surface element of the UWFOV reflective surface 20 to reflect and collimate light from such surface element toward the predetermined location 26 of the eye 16 according to one embodiment. Assume that a light ray 60 is emitted from the narrow-beam light source 22. Initially, the vergence at the narrow-beam light source 22 is determined. Assume that a half angle of a cone of light emitted from the narrow-beam light source 22 is 1 1 .2 degrees, per specifications of the narrow-beam light source 22. Determine a distance 62 (LCIcos) behind the narrow-beam light source 22 where a virtual light source 64 would need to be located to produce a cone of light having a half angle of 1 1 .2 degrees given an aperture of the size of the narrow-beam light source 22, in accordance with the following formula:

(LCIcos) = (display_width_mm/2)/(tan(thetal_2)) ^* 0.001 ; % [m]

where display_width_mm is the width of the narrow-beam light source 22, thetal_2 is the half angle of the cone of light (in this example, 1 1 .2 degrees).

[0035] The above calculation places the distance 62 (LSIcos) in meters. The distance 62 (LSIcos) may now be converted to a vergence. The vergence is negative since the light is diverging. The vergence (Vlcos) is measured in diopters [D]. The distance 62 LSIcos is the focal length to the virtual light source 64. The vergence (Vlcos) can be determined in accordance with the following formula:

Vlcos = -1 /(LSIcos ): [D]

[0036] Generally, at a high level, a set of values for the radius of curvature for the diverging reflective surface 24 and the UWFOV reflective surface 20 is cycled through and tested to determine how well the diverging reflective surface 24 and the UWFOV reflective surface 20 reflect the field points (the outer edges of the FOV) into the eye 16, while also collimating the light to the eye 16. The vergence at each surface element of the UWFOV reflective surface 20 should be zero so that reflected light is collimated. The vergence of the light ray 60 arriving at the diverging reflective surface 24 (VatD) is determined in accordance with the following formula:

VatD = - (1 /(LSIcos + Lid))

where LSIcos = the distance 62 and Lid = a distance 66 between the narrow- beam light source 22 and the diverging reflective surface 24.

[0037] VatD is negative since the light is diverging. The transfer vergence (Vtld) in the intervening space between the narrow-beam light source 22 and the diverging reflective surface 24 is determined in accordance with the following formula:

Vtld = VatD - Vlcos;

[0038] The vergence power of the diverging reflective surface 24 (Vdcalc) is based upon the radius of curvature (in meters) of the diverging reflective surface 24, selected during the respective multiple iterations through the plurality of possible values for the radius of curvature in accordance with the following formula:

Vdcalc = -2/(Rd),

where Rd is the radius of curvature of the diverging reflective surface 24.

[0039] The vergence of the light leaving the diverging reflective surface 24 (Vcurr) can be determined by summing all the vergences previously determined above in accordance with the following formula:

Vcurr = Vlcos + Vtld + Vdcalc.

[0040] This translates into a distance to the new virtual light source 64 of:

Lcurr = -1 /Vcurr: [m]

[0041] The vergence at the UWFOV reflective surface 20 (Vatc) can be determined in accordance with the following formula:

Vatc = -1 /(Lcurr + Ldc); where Ldc is a distance from the diverging reflective surface 24 to the UWFOV reflective surface 20.

[0042] In order to collimate the light into the eye 16, the power of the UWFOV reflective surface 20 cancels the vergence (Vatc) arriving at the UWFOV reflective surface 20 mirror. Thus, the radius of curvature (Rc) at this point on the UWFOV reflective surface 20 is:

Rc = -2/Vatc.

[0043] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.