Augmented/Virtual Reality Near-Eye Displays with Edge Imaging Lens Comprising a Plurality of Display Devices

Abstract

A system for near-eye display applications. A lens is provided with a beam-splitting interface horizontally along the width of the lens. Two display devices per lens are provided and disposed on the perimeter surface of the lens opposing an overlapped, prismatic facet optics assembly which balances aberration introduced by the slight symmetry break in the lens.

Claims

1. A near-eye display device comprising: a lens prism assembly comprising a viewer-facing surface, a scene-facing surface, a vertical dimension, a horizontal dimension and a lens thickness, wherein the lens prism assembly comprises an upper portion and a lower portion bonded together along a horizontal interface; a beam-splitting element defined on the horizontal interface; two or more display devices disposed on a first edge of the lens prism assembly, each display device configured to couple an optical image through the lens thickness; and a reflective element disposed on a second edge of the lens prism assembly, wherein the reflective element or the beam-splitting element comprises a plurality of overlapping, prismatic facet elements that are configured to transmit separate optical images in a predetermined interlaced pattern, and wherein the beam-splitting element is configured to couple the transmitted optical images through the viewer-facing surface to an eye pupil of a user.

2. The near-eye display device of claim 1, wherein both the reflective element and the beam-splitting element comprise a plurality of overlapping, prismatic facet elements that are configured to transmit the separate optical images in the predetermined interlaced pattern.

3. The near-eye display device of claim 2, wherein the prismatic facet elements of the beam-splitting element are linear and include alternating micro-prismatic features.

4. The near-eye display device of claim 1, wherein each of the prismatic facet elements includes circular micro-prismatic features that are concentric and whose centers are approximately aligned with respective centers of each of the two or more display devices.

5. The near-eye display device of claim 4, wherein the micro-prismatic features associated with one of the display devices are provided in an alternating pattern.

6. The near-eye display device of claim 1, wherein an eye box of the near-eye display device is elongated and has a horizontal dimension that is larger than its vertical dimension.

7. The near-eye display device of claim 6, further comprising: a supporting frame that mounts the near-eye display device on the user's face; and a spectacle lens mounted on the supporting frame through which the real world is viewed.

8. A near-eye display device having an elongated eye box with a horizontal dimension that is larger than its vertical dimension, the near-eye display device comprising: a supporting frame that mounts the near-eye display device on a user's face; a spectacle lens mounted on the supporting frame through which the real world is viewed, the spectacle lens including a view-facing surface and a scene-facing surface, wherein the spectacle lens is composed of a top portion and a bottom portion bonded together at a common interface surface; an image display device disposed on an edge of the top portion of the spectacle lens or on an edge of the bottom portion the spectacle lens, the image display device projecting light from the display device into the eye of the user.

9. The near-eye display device of claim 8, wherein a main area of the common interface surface is coated with partially reflective coating.

10. The near-eye display device of claim 9, wherein the partially reflective coating has a transmittance of 80% and a reflectance of about 20%.

11. The near-eye display device of claim 8, wherein if the image display device is disposed on a top edge of the top portion, then a reflective portion is disposed on a bottom edge of the bottom portion, wherein the reflective portion has an optical power to focus light from the image display device.

12. The near-eye display device of claim 11, wherein the reflective portion comprises a weak toroidal surface.

13. The near-eye display device of claim 11, wherein the reflective portion being disposed on the bottom edge of the bottom portion has a different radius of curvature along two orthogonal directions and the viewer facing surface of the spectacle lens has a different radius of curvature along two orthogonal directions.

14. The near-eye display device of claim 11, wherein the image display device and the reflective portion are rotated as a group around a vision line in opposite directions for a left eye and a right eye.

15. The near-eye display device of claim 14, wherein if the image display device is disposed on a bottom edge of the bottom portion, then a reflective portion is disposed on a top edge of the top portion, wherein the reflective portion has an optical power to focus light from the image display device.

16. The near-eye display device of claim 15, wherein the reflective portion comprises a weak toroidal surface.

17. The near-eye display device of claim 15, wherein the reflective portion being disposed on the top edge of the top portion has a different radius of curvature along two orthogonal directions and the viewer facing surface of the spectacle lens has a different radius of curvature along two orthogonal directions.

18. The near-eye display device of claim 15, wherein the image display device and the reflective portion are rotated as a group around a vision line in opposite directions for a left eye and a right eye.

19. A near-eye display device having an elongated eye box with a horizontal dimension that is larger than its vertical dimension, the near-eye display device comprising: a supporting frame that mounts the near-eye display device on a user's face; a spectacle lens mounted on the supporting frame through which the real world is viewed, the spectacle lens including a view-facing surface and a scene-facing surface; and two or more image display devices disposed at an upper edge of the spectacle lens or at a lower edge of the spectacle lens, each image display device projecting light from the image display device into an eye of a user.

20. The near-eye display device of claim 19, wherein each image display device covers a field of view zone, and wherein the field of view zones are stacked to achieve a larger field of view.

21. The near-eye display device of claim 20, wherein an eye box of the near-eye display device is composed of interspersed micro-zones working for different field of view zones.

22. The near-eye display device of claim 21, wherein the micro-zones are interspersed at a period comparable to a size of one of the micro-zones.

23. The near-eye display device of claim 21, wherein a size of one of the micro-zones is between 20 to 150 micrometers, and wherein the eye box is composed of interspersed micro-zones for the image display devices at a pitch of 20 to 150 micrometers.

24. The near-eye display device of claim 19, wherein the spectacle lens is composed of a top portion and a bottom portion, the top portion and the bottom portion bonded together at a common interface surface.

25. The near-eye display device of claim 24, wherein the upper edge is included in the top portion of the spectacle lens and the lower edge is included in the bottom portion of the spectacle lens, wherein the two or more image display devices are disposed on the upper edge of the top portion, and wherein a reflective portion is disposed on the lower edge of the bottom portion, the reflective portion having micro-features to focus light from each of the image display devices.

26. The near-eye display device of claim 25, wherein the micro-features partially transmit and reflect light from different image display devices toward the eye box of the near-eye display.

27. The near-eye display device of claim 19, wherein the two or more image display devices each comprise a directional modulation layer including at least one pixel-level micro-optical element configured to directionally modulate a light coupled onto the pixel-level micro-optical element from a corresponding pixel to a respective direction relative to an axis perpendicular to a surface of the display element.

28. The near-eye display device of claim 27, wherein the pixel-level micro optical element comprises a refractive micro optical element.

29. The near-eye display device of claim 27, wherein the pixel-level micro optical element comprises a diffractive micro-optical element.

30. The near-eye display device of claim 29, wherein the diffractive micro-optical element comprises a blazed grating or a rail grating.

31. The near-eye display device of claim 27, wherein a directional modulation of the pixel-level micro-optical element is determined by a slant angle or a pitch.

32. The near-eye display device of claim 27, wherein a directional modulation of the pixel-level micro-optical element is determined by a slant angle and a pitch.

33. The near-eye display device of claim 27, wherein a directional modulation of the pixel-level micro-optical element is determined by a blazed grating element.

34. The near-eye display device of claim 27, wherein the pixel-level micro-optical element comprises one or more semiconductor dielectric materials.

35. The near-eye display device of claim 27, wherein the pixel-level micro-optical element comprises multiple dielectric layers of silicon oxide or silicon nitride.

36. The near-eye display device of claim 27, wherein the directional modulation layer comprises a UV curable polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The embodiments herein are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and they mean at least one.

[0019] In the drawings:

[0020] FIG. 1 is a prior art see-through near-eye display system.

[0021] FIG. 2 is a further prior art see-through near-eye display system.

[0022] FIG. 3 is a yet further prior art see-through near-eye display system.

[0023] FIG. 4 is a yet further prior art see-through near-eye display system.

[0024] FIG. 5 is a yet further prior art see-through near-eye display system.

[0025] FIG. 6 is a yet further prior art see-through near-eye display system.

[0026] FIG. 7 is a yet further prior art see-through near-eye display system.

[0027] FIG. 8 is a yet further prior art see-through near-eye display system.

[0028] FIG. 9 is a prior art FOV tiling near-eye display system.

[0029] FIG. 10 is a yet further prior art FOV tiling see-through near-eye display system.

[0030] FIG. 11A shows one path in a prior art time sequence FOV tiling see-through near-eye display system.

[0031] FIG. 11B shows a different path in the same near-eye display system as in FIG. 11A.

[0032] FIG. 12 is a yet further prior art time sequence FOV tiling see-through near-eye display system.

[0033] FIG. 13 illustrates an example for explaining a see-through near-eye display system according to an embodiment herein.

[0034] FIG. 14 illustrates an example for explaining a right eye channel of a see-through near-eye display system according to an embodiment herein.

[0035] FIG. 15 illustrates an example for explaining a horizontal view of a right eye channel of a see-through near-eye display system according to an embodiment herein.

[0036] FIG. 16A illustrates an example for explaining a right eye FOV tiling see-through near-eye display system according to an embodiment herein.

[0037] FIG. 16B illustrates a second example for explaining a right eye FOV tiling see-through near-eye display system according to an embodiment herein.

[0038] FIG. 17 illustrates an example for explaining a horizontal view of a right eye FOV tiling see-through near-eye display system according to an embodiment herein.

[0039] FIG. 18A illustrates an example for explaining two overlapped Fresnel mirrors with optical power according to an embodiment herein.

[0040] FIG. 18B illustrates an example for explaining spatially-multiplexed Fresnel mirrors with optical power according to an embodiment herein.

[0041] FIG. 18C illustrates an example for explaining spatially-multiplexed Fresnel mirrors without optical power according to an embodiment herein.

[0042] FIG. 19 illustrates an example for explaining angular prismatic facet elements in a Fresnel mirror according to an embodiment herein, to implement a free-form optical surface.

[0043] FIG. 20A illustrates an example for explaining a non-telecentric display element incorporated into a near-eye optical system having a flat lens according to an embodiment herein.

[0044] FIG. 20B illustrates an example for explaining a non-telecentric display element incorporated into a near-eye optical system having a curved lens according to an embodiment herein.

[0045] FIG. 21 illustrates an example for explaining a non-telecentric display element incorporated into a near-eye optical system, the non-telecentric display element being comprised of refractive optical elements according to an embodiment herein.

[0046] FIG. 22 illustrates an example for explaining a non-telecentric display element incorporated into a near-eye optical system, the non-telecentric display element being comprised of tilted refractive optical elements according to an embodiment herein.

DETAILED DESCRIPTION

[0047] The present disclosure and various of its embodiments are set forth in the following description of the embodiments which are presented as illustrated examples of the disclosure in the subsequent claims. It is expressly noted that the disclosure as defined by such claims may be broader than the illustrated embodiments described below. The word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs.

[0048] In one example embodiment, a near-eye display device is disclosed comprising a lens prism assembly comprising a viewer-facing surface, a scene-facing surface, a vertical dimension, a horizontal dimension and a lens thickness. The lens prism assembly may comprise an upper portion and a lower portion bonded together along a horizontal interface comprising a beam-splitting element. Two or more display devices may be disposed on a first edge surface and each configured to couple an optical image from the respective display devices through the lens thickness.

[0049] In one embodiment, a reflective element is disposed on a second edge surface that generally opposes the first surface. The reflective element, the beam-splitting element or both the reflective element and the beam-splitting element may comprise a region comprising a plurality of overlapping, prismatic facet elements that are configured to reflect or transmit the separate optical images (from the display devices) that overlap on the reflective element (i.e. areas where the two separate display device images overlap on the reflective element) in a predetermined interlaced optical pattern and back toward the beam-splitting element. The beam-splitting element may be further configured to couple the reflected optical images through the viewer-facing surface to an eye pupil of a user.

[0050] By virtue of the example embodiments herein, a compact NED is enabled that resembles the appearance of a pair of ordinary spectacle glasses (i.e., eyeglasses in the format of a typical consumer eyeglass frame), has good quality in both the displayed image and the “see-through” real-world view, is easy to fabricate in mass production and is comfortable to wear by accommodating large inter-pupil distance (IPD) variation among people.

[0051] The embodiments herein may be provided to take advantage of advances made in display device technologies, particularly self-emissive display devices with micro-pixels such as the Quantum Photonic Imager or “QPI®” imager. QPI® is a registered trademark of Ostendo Technologies, Inc. See U.S. Pat. No. 7,623,560, U.S. Pat. No. 7,767,479, U.S. Pat. No. 7,829,902, U.S. Pat. No. 8,049,231, U.S. Pat. No. 8,243,770, U.S. Pat. No. 8,567,960, and U.S. Pat. No. 8,098,265. Display devices such as the QPI imager offer high brightness and high resolution images in a very compact format and are particularly well-suited for the compact NED of present disclosure.

[0052] The embodiments herein may also take advantage of the ergonomic fact that, although humans' IPD varies greatly among the general population and users tend to scan their eyes in a large latitude to their left or to their right, a human's vertical eye scan movement is much narrower and less frequent. Humans generally tend to scan their vertical field of view by tilting their head back or forward. The embodiments herein exploit this behavior so that the disclosed NED does not require a circular eye box but rather provides an elongated eye box or exit pupil having a horizontal dimension that is larger than its vertical dimension. The eye box can be a 2-D or 3-D viewing region within which the viewer's eye can move and still see the entire image. The NED system may be vertically aligned with a user's eyes by adjusting the system up or down along the wearer's nose bridge like an ordinary pair of eyeglasses are worn and adjusted. Since much of the bulkiness of prior art NEDs comes from the requirement of having a large circular eye box, the reduction of eye box size in the vertical direction beneficially reduces system bulkiness in the corresponding horizontal (eye sight) direction which is the dominant eye-scan direction.

[0053] A conventional eyeglass or spectacle lens generally has its largest dimension along its width (horizontal) and the smallest dimension through its thickness with the height (vertical) dimension somewhere between the width and thickness dimension. The shape of the front (scene-facing) and the back (viewer-facing) of a spectacle lens is typically decided by the ophthalmic function or fashion. Thus, the lens edge surfaces may be modified to implement the function of coupling and reflecting an electronic image that is displayed from a display device to the eye pupil of a viewer. By disposing one or more display devices on the upper (“first”) or the lower(“second”) edge surface of a lens and coupling the image outputs from the display device(s) using a reflective optic assembly at the opposing edge surface, the larger lens horizontal dimension can correspond to the larger horizontal eye box dimension and the smaller lens vertical dimension can correspond to the smaller vertical eye box dimension.

[0054] By virtue of embodiments described herein, it is possible to simplify the light path from the display device to eye pupil and minimize any break of symmetry to ensure maximum optical performance. A lens suitable for an embodiment of the NED of the present disclosure may comprise a beam-splitting bonding interface embedded along the horizontal dimension of the lens, about mid-way along the lens' height dimension which divides the lens into two parts: an upper portion and a lower portion. The embedded interface can be provided with a partially-reflective coating whereby the interface functions as an optical beam-splitting element. In one embodiment, at least one, but preferably two or more, imaging source display devices such as QPI imagers are disposed on a first edge surface (“upper” in the described embodiment) facing the embedded beam-splitting interface and a novel reflective element surface, with or without optical power, is disposed on a second edge (“lower” in the described embodiment) facing the interface. It is expressly noted the above described embodiment is not limited to having the imager disposed on the first surface and the reflective element disposed on the second surface and that the terms “first” and “second” surfaces are used for convenience only and are considered interchangeable positions. For instance, disposing the imager on the second surface and the reflective element on the first surface are contemplated as being within the scope of the embodiments disclosed herein.

[0055] In one embodiment, a displayed image received from each of the display devices is coupled into the thickness of the lens body by optical transmission from the first edge. The information light transmits through the embedded partially-reflective interface and transverses the lens body along a straight path to the second edge upon which reflective element optics are disposed. Upon reflection from the reflective element disposed on the second edge, the information light travels back to the embedded partially-reflective interface. Upon reflection at the partially-reflective interface, information light transmits through the lens' viewer-facing surface and enters the eye pupil where it is perceived as a virtual image superimposed on the real-world view along the vision line.

[0056] In this optical path layout, much of the imaging work is performed by the edge reflective element optics which may be generally centered relative to the opposing display devices. The folding reflection at the embedded plane interface introduces little to no aberration. Although the spectacle lens viewer-facing surface is generally curved and tilted relative to the vision line for fashion or vision correction reasons, the aberration introduced at the viewer-facing surface is manageable due to the low divergence of information light at the surface and can be corrected at the reflective element or by clocking the display device and reflective element around the vision line as a group. Although the layout of the optical path of the information light of the present disclosure may be provided as a 3D path in nature, the break of symmetry is gentle with good optical performance attainable.

[0057] Another advantageous aspect of the present disclosure is the increase in horizontal field of view through the use of two QPI imagers or suitable display devices that are disposed on the first edge of the lens. In one embodiment, the total FOV may be divided into two tiled-up zones; a first zone and second zone with each zone supported by a single QPI imager. To ensure the complete overlap of light paths from these two zones over the eye box of NED, micro-prismatic facet features similar to those found in a Fresnel lens can be employed on the reflective element surface at the second edge of a lens and on the partially-reflective interface embedded in the thickness of the lens. These micro-prismatic facet features are categorized into two types with each type working with a respective display device. These two types of micro-prismatic facet features are interspersed at a period comparable to the micro-prismatic facet feature size. A typical size of the micro-prismatic facet feature may be about 20 to 150 um at which scale the light is reflected/refracted rather than diffracted. Thus, the wavelength dependence can be much less than that of diffracted elements. As a result, the eye box of the NED is composed of interspersed zones for different display devices at a pitch of 20 to 150 um. Since this pitch is much smaller than the typical 4mm eye pupil of a user, a user's eyes can move over the entire eye box without image gaps being observed in the FOV. An advantageous effect of this embodiment is the compactness of the near-eye device and large effective eye box for the total FOV.

[0058] In one embodiment, a Fresnel slope angle is contoured along a closed circle of a Fresnel optical prismatic facet element to implement free-form optical surfaces which are useful in optical aberration correction.

[0059] The description of the various embodiments of the NED of the disclosure is made with regard to one lens or one eye but it is expressly noted that the description is intended to include two lenses or both eyes which together provides stereoscopic or binocular vision.

[0060] FIG. 13 shows one embodiment of the present disclosure. In this embodiment, the lens prism assembly 1320L and 1320R for the left eye and right eye respectively are supported by a holding assembly 1300 which may be in the form of a conventional eyeglass frame. The holding device 1300 may be designed to resemble a conventional eyeglass frame but other styles are enabled. Display devices 1310L and 1310R can be disposed at the first upper edges 1311R and 1311L of 1320L and 1320R as shown in FIG. 13, but may be disposed at the second lower edges 1312R and 1312L of 1320L and 1320R as well, or any combination of first edge or second edge device positions may be employed.

[0061] Except for the embedded beam-splitting surfaces 1330L and 1330R, the lens prism assemblies 1320L and 1320R resemble and function in the transmission of light received from the real-world view as a pair of ophthalmic lenses and may be provided with or without vision correction. Other components like computers, sensors, antenna, control circuit boards and batteries may also be incorporated into the holding frame assembly 1300 or alternatively, the display devices 1310L and 1310R can be connected to an external computer through wireless means or cables coming out of the two ends of the temples of the glasses frame. Because of the mirror symmetry relationship between the systems for the left eye and the right eye, only the right eye system is described in the following but use in binocular applications is contemplated as within the scope of the disclosure and the claims.

[0062] FIG. 14 illustrates the lens prism assembly 1420R formed by an upper portion 1425R′ and a lower portion 1425R″ with 1430R noted as the beam-splitting element bonding interface of the two portions, according to one embodiment. The upper portion 1425R′ on whose first edge 1426R the display device 1410R is disposed has a partially-reflective coating applied on its interface 1430R with lower portion 1425R″ to define a beam-splitting element. The lower portion 1425R″ is provided with a reflective surface 1440R disposed on its second edge 1427R. The large plane feature of interface 1430R can have a transmittance of about 80% and a reflectance of about 20% but any suitable user-defined transmittance/reflectance ratio may be selected. This can be achieved for instance by use of a metal coating or dielectric thin film coating as is known in the optical art. The scene-facing and viewer-facing surfaces of upper portion 1425R′ and the lower portion 1425R″ can be aligned with each other and bonded together with an index-matching optical cement. It is desirable that any misalignment between scene-facing and viewer-facing surfaces of the lens prism assembly 1420R be smaller than 0.1 mm after bonding to minimize or avoid artifacts in the transmission of the real-world view to the user.

[0063] FIG. 14 illustrates a ray path from D, the center of display device 1410R, through the lens prism assembly 1420R, to E, the eye pupil plane 1450R, according to one embodiment. The line EG 1460R is the vision line when the right eye is looking straight ahead at infinity or at a plane located greater than two meters away. As the light ray leaves the display device center D, it travels down the lens thickness of upper portion 1425R′ of the lens prism assembly 1420R, transmits through the interface 1430R, to lower portion 1425R″ and incident at A on the reflective element 1440R. Upon reflection from 1440R, the ray travels back to intercept the interface 1430R at B. The ray is then reflected toward G on the viewer-facing surface of the lens prism assembly 1420R. After transmission through the viewer-facing surface, the ray enters the viewer's eye pupil at E along vision line direction 1460R. The information in the form of an optical image received from display device 1410R is then perceived as superimposed upon the real-world view along vision line 1460R.

[0064] FIG. 14 also shows the elliptical beam footprint F at the eye pupil plane for light transmitted from a point on the display device. The horizontal dimension of the beam foot print F is several times larger than its vertical dimension. This is the result of the horizontal dimension of the lens prism assembly 1420R being larger than its dimension along the vision line 1460R direction. However, this may not reduce the performance of the NED of the embodiments of the disclosure. Although a relatively large horizontal beam footprint can accommodate the variation of IPD among the user population and the left and right sweeping of the eye pupil of a user, the smaller vertical beam footprint is compensated by adjusting the position of the eyeglass frame on user's nose ridge and its effect further minimized by the fact the general population of humans tend to tilt their head back and forth to view in the vertical direction instead of moving their eyes in vertical dimension.

[0065] Earlier attempts have been made at making the vertical dimension of the beam footprint as large as the horizontal dimension. The resulting systems can be bulky and/or complicated. On the other hand, the optical system of the present disclosure beneficially has most of its optical power contributed by the reflective element 1440R which may be centered relative to the display device 1410R. In one embodiment, reflective element 1440R can be provided as a weak toroidal surface with small difference in curvature radius along two orthogonal directions. This departure from the rotational symmetry of reflective surface 1440R accounts for the fact that the viewer-facing surface of the lens prism assembly 1420R may be provided to have a different curvature radius along two orthogonal directions. Although the viewer-facing surface of lens prism assembly 1420R may be generally of toroidal shape and tilted with respect to the vision line 1460R, the information rays as focused by 1440R have low divergence at the viewer-facing surface and form moderate angles with respect to the vision line 1460R. In addition, the curvature radius on the scene-facing surface and viewer-facing surface of the lens prism assembly 1420R is not strong for practical reasons and all of these features combine to provide an acceptable aberration level and good optical performance.

[0066] FIG. 15 shows the horizontal view of the ray path from D center of a display device 1510R to the center E of eye pupil 1550R for the lens prism assembly 1520R, according to one embodiment. In this embodiment, the line GE and its extension defines the vision line 1560R. For fashion, compactness, or the need of vision correction, the scene-facing surface and viewer-facing surface of lens prism system 1520R is generally curved and tilted relative to vision line 1560R as shown in FIG. 15. As a result, ray path DAB GE does not lie within a single plane but lays in a 3D space. The NED imaging system of the disclosure is thus generally tilted without any symmetry plane. However, the imaging system can still be considered a quasi-axial one relative to the center ray as discussed above. In contrast to off-axis systems as disclosed in prior art patent literature, the quasi-axial system of the present disclosure has the advantage of easy fabrication and good optical performance. Also, in contrast to prior art on-axis systems as disclosed in prior art patent literature, the quasi-axial system of the present disclosure has the advantage of compactness and aesthetics.

[0067] FIGS. 16A and 16B show example optics for the right eye of an embodiment of the present disclosure in which two display devices are disposed side-by-side to extend the horizontal FOV from that of a single display device NED. In FIGS. 16A and 16B, the right eye optics assembly 1620R are formed by an upper portion 1615R′ and a lower portion 1615R″ with 1630R identified as the bonding interface of the two respective portions that defines a beam-splitting element. The upper portion 1615R′ on whose first upper edge 1616R the display devices 1610tR and 1610bR are disposed can be provided with a partially-reflective coating applied on its interface 1630R to lower portion 1615R″. The partially-reflective coating on 1630R of the upper portion 1615R′ can have a transmittance of about 80% and a reflectance of about 20% but other ratios may be implemented. This can be achieved for instance by use of a metal coating or dielectric thin film coating as is known in the optical arts. The scene-facing surface and viewer-facing-surface of upper portion 1615R′ and the lower portion 1615R″ can be aligned with each other and bonded using an index-matching optical cement applied on the bonding interface 1630R. It is desirable for the misalignment between scene-facing surface and viewer-facing-surface of the lens prism assembly to be less than about 0.1 mm after bonding to minimize or avoid artifacts in the transmission of the real-world view to the user.

[0068] FIG. 16A also shows chief ray paths from the center and four corners of display devices 1610tR and 1610bR, through the lens prism assembly 1620R, all the way to the eye pupil plane, according to one embodiment. As the rays leave the display devices, they travel through the thickness of lens prism assembly 1620R and straight down through upper portion 1615W of the lens prism assembly 1620R, partially transmit through the interface 1630R to enter the lower portion 1615R″ and are incident upon on the reflective element 1640R. Minute prismatic features are provided on 1640R similar to those of a Fresnel mirror on a flat substrate. These prismatic features may be configured to impart optical power to the otherwise flat substrate surface and perform a role in imaging the output of the display devices to the eye. Upon reflection from 1640R, the rays travel back to intercept interface 1630R. They are then partially-reflected by 1630R and exit the lens prism assembly 1620R toward the eye through the viewer-facing surface. The optical information coupled from display devices 1610tR and 1610bR is perceived as superimposed upon the real-world view. There may also be prismatic features disposed on the 1630R interface configured so that rays from either 1610tR or 1610bR are directed toward the eye pupil by an otherwise plane-like feature. As shown in FIGS. 16A and 16B, there may be an overlap 1650 of light paths from display devices 1610tR and 1610bR which overlap is accommodated by the prismatic features.

[0069] FIG. 17 shows the horizontal view of chief ray paths from the center and corner points on display devices 1710bR and 1710tR to the center of eye pupil for right eye lens prism assembly 1720R, according to one embodiment. The FOV contributed by each display device combines to form a large FOV with a minimal overlap. Due to the employment of micro-prismatic features on the embedded beam-splitter element interface 1630R and reflective element 1640R of FIG. 16A, the interlacing of light from either display device over the eye pupil plane is on a micro-scale and image gaps or other directional artifacts are not observed during eye movement. For fashion, compactness, or the need of vision correction, the scene-facing surface and viewer-facing-surface of lens prism assembly 1720R is generally curved, tilted and without a symmetry plane. However, the break of symmetry is gentle due to the major imaging path segment from each display device to its corresponding Fresnel prismatic features on reflective element 1640R having rotational symmetry around the normal axis at the center of the respective display device.

[0070] In contrast to off-axis systems as disclosed in prior art, the quasi-axial system of the present disclosure has the advantage of easy fabrication and good optical performance. Also, the optical interlacing of micro-prismatic features for different display devices permits a large overlap of light paths from different display devices, resulting in a reduction of system volume.

[0071] FIG. 18A shows an example use of overlapped Fresnel mirrors 1850bR and 1850tR on the lower second edge 1840R of the exemplar right eye NED optics, according to one embodiment. Each Fresnel mirror can be provided with concentric circular micro-prismatic features whose centers are approximately aligned with those of the respective display devices. Such alignment can ensure higher optical performance.

[0072] FIG. 18B shows the interlacing of prismatic features from 1850bR and 1850tR by eliminating alternating selected concentric prismatic features of 1850tR, according to one embodiment. Selected concentric prismatic features for 1850tR may not be provided while all concentric features for 1850bR are. In this embodiment, the display device for 1850bR is perceived as less bright than the other device but the loss of brightness is compensated by the display device like the QPI imager. The advantage in system volume reduction resulting from this overlap approach is substantial. It is noted that, similarly, the alternative features on 1850bR may be eliminated with all features on 1850tR being on.

[0073] FIG. 18C shows the micro-prismatic features on the embedded beam-splitting element interface 1830R of the example right eye NED optics, according to one embodiment. Since there is no optical power on the interface 1830R, the prismatic features may be generally linear in contour. The prismatic features are alternating for either of the display devices as designated by b or t as shown in FIG. 18C.

[0074] For a given symmetrical optical surface, its equivalent Fresnel surface has concentric circular features with a constant slope angle. Optical power is imparted by providing a predetermined variation of slope angle across the various circular features. In a tilted optical system of the disclosure, a free-form optical surface may be used for aberration correction. A simple method to implement a free-form surface in the Fresnel type lens disclosed herein is to modulate the slope angle periodically at predetermined periods along the azimuth direction on a circle. An embodiment comprising the above approach is depicted in FIG. 19. Each curve represents a concentric circle of a Fresnel prism element at a certain radius. In this example, the slope angle and the contouring magnitude increase as the circle radius increases. This type of free-form Fresnel optics assists in balancing aberrations that may be introduced by slight symmetry break in NED for compactness and aesthetics.

[0075] Turning to FIGS. 20A and 20B, embodiments involving reduction of “ghost” images are now discussed. By way of background, undesirable “ghost” images are typically generated in optical systems due to reflections off of the lens element that are visible in the eye-box of the system. Such reflections and the ghost images they cause are avoided in the flat and curved optical lens embodiments illustrated in FIGS. 20A and 20B by using “non-telecentric” emission display elements 2000A and 2000B. Examples of non-telecentric display elements suitable for use in these embodiments are disclosed in U.S. patent application Ser. No. 15/391,583, filed Dec. 27, 2017, entitled “Non-Telecentric Emissive Micro-Pixel Array Light Modulators and Methods of Fabrication Thereof”, the entirety of which is incorporated herein by reference.

[0076] In the non-telecentric embodiments disclosed herein, the respective pixels of each of display elements 2000A and 2000B are provided with an associated array of pixel-level micro optical elements (pixel-level micro lens array or “PMLA”) that is configured to collimate light emitted from each pixel to match a reflector optical aperture. Each pixel element is configured to direct the light emitted from the pixel toward the reflector optical aperture by means of the associated PMLA micro optical element. The individual light emission from each pixel is thus directionally modulated by the PMLA in a unique direction to enable a predetermined non-telecentric pixel light emission pattern from the pixel array of non-telecentric display element 2000.

[0077] In one aspect, the PMLA layer of pixel-level micro optical elements is disposed above the pixels and is used to directionally modulate light coupled onto the PMLA micro optical elements from the corresponding pixels in a predetermined respective direction relative to an axis that is perpendicular to the surface of non-telecentric display element 2000A or 2000B.

[0078] Non-telecentric display element 2000A or 2000B may be incorporated into either a flat lens element design (as shown in FIG. 20A) or a curved lens element design (as shown in FIG. 20B) of a near-eye optical system. The flat lens element design may include a flat lens prism assembly 2020A, embedded beam-splitting surface 2030A, and reflective surface 2040A. The curved lens element design may include a curved prism assembly 2020B, embedded beam-splitting surface 2030B, and reflective surface 2040B. In these embodiments, the light emitted from each pixel is substantially coupled to the reflector's optical aperture with minimal light ray scattering toward the lens viewing surface and with minimal reflection toward the viewing eye-box that can result in undesired ghost images. It is therefore possible to reduce “ghost” images by virtue of the arrangements in FIGS. 20A and 20B.

[0079] FIG. 21 illustrates an example non-telecentric display element 2000C for use with a near-eye display system, in which individual non-telecentric micro optical elements making up PMLA 2000C-1 are realized as refractive optical elements (ROE) and are used to direct selected pixel light outputs at angles generally inclined relative to the surface of non-telecentric display element 2000C.

[0080] In the embodiment of FIG. 21, directional modulation of the pixel-level refractive non-telecentric micro optical elements are realized using de-centered micro lenses formed by successive low and high refractive index layers of dielectric materials 2000C-2 and 2000C-3, each having different indexes of refraction. FIG. 21 is a schematic cross-section of non-telecentric display element 2000C comprising an array 2000C-1 of non-telecentric refractive micro optical elements. In this embodiment, array 2000C-1 of pixel-level non-telecentric micro optical elements may be fabricated monolithically at the wafer level as multiple layers of semiconductor dielectric material, such as silicon oxide for low index layer 2000C-2 and silicon nitride for high index layer 2000C-3, using known semiconductor lithography, etch and deposition techniques. As illustrated in FIG. 21, array 2000C-1 of pixel-level micro optical elements are realized using multiple layers; the dielectric materials 2000C-2 and 2000C-3 having different indexes of refraction that are successively (sequentially) deposited to form the refractive surfaces of pixel-level micro optical elements, each of which progressively vary in refractive micro-lens element center position across array 2000C-1 as required to obtain the desired non-telecentric characteristics and image projection directions.

[0081] FIG. 22 illustrates an example of a non-telecentric display element 2000D in which the array 2000D-1 of non-telecentric micro optical elements are realized as tilted refractive optical elements (ROE), again progressively varying across array 2000D-1 to obtain the desired non-telecentric characteristics and image projection directions, and may be used to direct selected pixel light outputs at angles generally inclined relative to the surface of non-telecentric display element 2000D. In this embodiment, and as best illustrated in FIG. 22, directional modulation of the pixel-level refractive non-telecentric micro optical elements is realized using “tilted” micro lenses that are formed by successive layers of dielectric materials 2000D-2 and 2000D-2, each having different indexes of refraction.

[0082] FIG. 22 is a side view of non-telecentric display element 2000D comprising a plurality of tilted refractive micro optical elements. In this embodiment, array 2000D-1 of pixel-level non-telecentric micro optical elements may be fabricated monolithically at the wafer level as multiple layers of semiconductor dielectric materials, such as silicon oxide for low index layer 2000D-2 and silicon nitride for high index layer 2000D-3, using known semiconductor lithography, etch and deposition techniques. As illustrated in FIG. 22, array 2000D-1 may be realized using multiple layers dielectric materials 2000D-2 and 2000D-3 with different indexes of refraction successively (sequentially) deposited to form the refractive surfaces of the pixel-level non-telecentric micro optical elements that comprise array 2000D-1.

[0083] Non-telecentric display elements 2000C and 2000D may each comprise refractive or diffractive micro optical elements which may be fabricated from a UV curable polymer. The diffractive micro optical elements of non-telecentric display elements 2000C and 2000D may each comprise blazed gratings or rail gratings. Blazed gratings used in the non-telecentric display element may be configured whereby the directional modulation of the pixel outputs is determined at least in part by a slant angle, a pitch or both a slant angle and a pitch, of the blazed grating elements.

[0084] Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the disclosure. Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the disclosure as defined by any claims in any subsequent application claiming priority to this application.

[0085] For example, notwithstanding the fact that the elements of such a claim may be set forth in a certain combination, it must be expressly understood that the disclosure includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations.

[0086] The words used in this specification to describe the disclosure and its various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus, if an element can be understood in the context of this specification as including more than one meaning, then its use in a subsequent claim must be understood as being generic to all possible meanings supported by the specification and by the word itself.

[0087] The definitions of the words or elements of any claims in any subsequent application claiming priority to this application should be, therefore, defined to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense, it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in such claims below or that a single element may be substituted for two or more elements in such a claim.

[0088] Although elements may be described above as acting in certain combinations and even subsequently claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that such claimed combination may be directed to a subcombination or variation of a subcombination.

[0089] Insubstantial changes from any subsequently claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of such claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements.

[0090] Any claims in any subsequent application claiming priority to this application are thus to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the disclosure.