Reflection suppression in near-eye displays

Abstract

A near-eye display includes a light-guide optical element, LOE, (10) having planar and mutually parallel first and second major external surfaces (11A, 11B). An image projector (2) introduces illumination corresponding to an image into the LOE, so that the illumination propagates within the LOE by internal reflection at the major external surfaces. A coupling-out arrangement couples the illumination out of the LOE towards an observer's eye. The coupling-out arrangement can be a set of mutually parallel partially-reflective surfaces (12A) deployed at an oblique angle within the LOE. Various arrangements for suppressing reflections of ambient light sources include obscuration baffles oriented to avoid peripheral field-of-view reduction, various non-reflective coatings, and various deployments of polarizing filters.

Description

Technical Field

[0001] The present invention relates to near-eye displays, and more particularly to near-eye displays having various features for suppressing ghosting images of bright objects. Background Technology

[0002] Many near-eye display systems include a transparent light-guide optics (LOE) or "waveguide" placed in front of the user's eye, which transmits an image within the LOE via internal reflection and then couples the image out toward the user's eye via a suitable output coupling mechanism. The output coupling mechanism can be based on an embedded partial reflector or "facet," or it can employ a diffraction mode. The following description will primarily relate to facet-based coupling devices; however, it should be understood that various features of the invention can also be applied to diffraction devices. In the case of diffraction elements, the direction of extension of the facet referred to herein can be considered to refer to the orientation of the elements of the diffraction grating.

[0003] The waveguide and facet are at least partially transparent, allowing light from the surrounding (scene) to pass through them, enabling the user to view the real world directly. Some of the scene light is reflected by the facet and reaches the eye at various angles, generating unwanted "ghosting" images (reflections) of the real world. Summary of the Invention

[0004] This invention is a near-eye display.

[0005] According to the teachings of embodiments of the present invention, a near-eye display for projecting an image onto an observer's eye is provided, the near-eye display comprising: (a) a light-guiding optical element (LOE) having a planar and mutually parallel first and second primary outer surfaces and edges; (b) a support device configured to support the LOE relative to the observer's head when the second primary outer surface is facing the observer's eye; (c) an image projector for projecting illumination corresponding to the image, the image projector being optically coupled to the LOE to introduce illumination into the LOE so as to propagate within the LOE by internal reflection at the first and second primary outer surfaces; (d) a coupling device deployed to couple the illumination out of the LOE toward the observer's eye; and (e) a light-blocking baffle extending along a large portion of one of the edges of the LOE and projecting from the plane of the second primary outer surface to block incident radiation from a range of grazing angles from reaching at least a portion of the second primary outer surface, the baffle projecting in a direction toward the observer's eye thereby forming an acute angle with the second primary outer surface.

[0006] According to another feature of an embodiment of the invention, the light-blocking baffle protrudes in a direction toward the center of the observer's eyeball.

[0007] According to another feature of an embodiment of the invention, the coupling device includes a plurality of mutually parallel partially reflective surfaces, which are arranged at an angle to the first main outer surface within the LOE.

[0008] According to another feature of an embodiment of the invention, the deployment of the baffle and the partially reflective surface prevents the light path from reaching the observer's eye after entering one of the first and second main outer surfaces and undergoing a single reflection from one of the partially reflective surfaces.

[0009] According to another feature of an embodiment of the invention, the partially reflective surface has an extension direction parallel to the second main outer surface, and wherein the baffle extends substantially parallel to the extension direction of the partially reflective surface along a large portion of one of the edges.

[0010] According to another feature of an embodiment of the invention, the light-blocking baffle is mechanically supported by being attached to the LOE.

[0011] According to another feature of an embodiment of the invention, the light-blocking baffle is mechanically supported by being attached to a support device.

[0012] According to the teachings of embodiments of the present invention, a near-eye display for projecting an image onto an observer's eye is also provided, the near-eye display comprising: (a) a light-guiding optical element (LOE) having a planar and mutually parallel first primary outer surface and a second primary outer surface; (b) a support device configured to support the LOE relative to the observer's head when the second primary outer surface is facing the observer's eye; (c) an image projector for projecting illumination corresponding to the image, the image projector being optically coupled to the LOE to introduce illumination into the LOE so as to propagate within the LOE by internal reflection at the first and second primary outer surfaces; and (d) a coupling device deployed to couple the illumination out of the LOE toward the observer's eye, wherein the first primary outer surface is coated with a multilayer coating configured to provide anti-reflective properties for visible light incident at an angle of incidence less than 40 degrees and to provide high reflectivity for at least a first polarization of visible light incident at an angle of incidence greater than 70 degrees.

[0013] According to another feature of an embodiment of the invention, the second main outer surface is coated with a multilayer coating, which is configured to provide anti-reflective properties for visible light incident at an angle of incidence of less than 40 degrees, and to provide low reflectivity for a second polarization of visible light perpendicular to a first polarization incident at an angle of incidence between 70 and 85 degrees.

[0014] According to the teachings of embodiments of the present invention, a near-eye display for projecting an image onto an observer's eye is also provided, the near-eye display comprising: (a) a light-guiding optical element (LOE) having a planar and mutually parallel first and second primary outer surfaces; (b) a support device configured to support the LOE relative to the observer's head when the second primary outer surface is facing the observer's eye; (c) an image projector for projecting illumination corresponding to the image, the image projector being optically coupled to the LOE to introduce illumination into the LOE so as to propagate within the LOE by internal reflection at the first and second primary outer surfaces; (d) a coupling device deployed to couple the illumination out of the LOE toward the observer's eye; and (e) a micro-visor layer associated with the first primary outer surface of the LOE, the micro-visor layer blocking light incident from at least one direction at an incident angle greater than 70 degrees from entering the LOE.

[0015] According to another feature of an embodiment of the invention, the micro venetian blind layer includes a one-dimensional array of micro venetian blinds having an extension direction, and wherein the micro venetian blind layer is deployed with the extension direction substantially horizontal.

[0016] According to another feature of an embodiment of the invention, the micro venetian layer comprises two micro venetian arrays having a substantially perpendicular extension direction.

[0017] According to the teachings of embodiments of the present invention, a near-eye display for projecting an image onto an observer's eye is also provided, the near-eye display comprising: (a) a light-guiding optical element (LOE) having a planar and mutually parallel first and second primary outer surfaces; (b) a support device configured to support the LOE relative to the observer's head when the second primary outer surface is facing the observer's eye; (c) an image projector for projecting illumination corresponding to the image, the image projector being optically coupled to the LOE to introduce illumination into the LOE so as to propagate within the LOE by internal reflection at the first and second primary outer surfaces; (d) a coupling device deployed to couple the illumination toward the observer's eye from the LOE, the LOE and the coupling device defining at least one high-incident-angle polarization-dependent optical path incident on one of the first and second primary outer surfaces at an incident angle greater than 60 degrees and exiting the LOE toward the observer's eye, the polarization-dependent optical path having a favorable polarization orientation; and (e) a polarization filter deployed to prevent external light with a favorable polarization orientation traveling along the polarization-dependent optical path from reaching the observer's eye.

[0018] According to another feature of an embodiment of the invention, the polarization filter is deployed to filter the light entering the first main outer surface.

[0019] According to another feature of an embodiment of the invention, the polarization filter is deployed to filter light exiting the second primary outer surface toward the observer's eye.

[0020] Another feature of an embodiment of the invention is that the illumination emanating from the LOE toward the observer's eye is substantially polarized using image polarization, and wherein a polarization filter is deployed to block light having polarization perpendicular to the image polarization.

[0021] According to another feature of an embodiment of the invention, a second polarization filter is also provided, which is deployed to filter light entering the first main outer surface, and the polarization filter and the second polarization filter are aligned to transmit the same polarization.

[0022] According to another feature of an embodiment of the invention, a lateral polarizing light-blocking element is also provided for filtering light from at least one direction along the path between the observer's eye and the LOE, wherein the polarization axis of the lateral polarizing light-blocking element is at an angle relative to the polarization axis of the polarization filter.

[0023] Another feature of the embodiments of the present invention provides a lateral polarizing light-blocking element for filtering light from at least one direction along the path between the observer's eye and the LOE.

[0024] According to another feature of an embodiment of the invention, the coupling device includes a plurality of mutually parallel partially reflective surfaces, which are arranged at an angle to the first main outer surface within the LOE. Attached Figure Description

[0025] The invention has been described herein by way of example only with reference to the accompanying drawings, in which:

[0026] Figure 1A and Figure 1B These are schematic side and top views of an observer using a near-eye display constructed and operated according to the teachings of the present invention, showing various ambient light sources that may cause reflections to be suppressed;

[0027] Figure 2A yes Figure 1A An enlarged schematic side view of a near-eye display shows the light path of image illumination and the light path of an exemplary "ghosting" light path from an ambient light source;

[0028] Figure 2B and Figure 2C It is shown Figure 2A An angle diagram showing the angular relationships between different parts of the image ray path and the ghost ray path;

[0029] Figure 3A It is based on Figure 1A An enlarged schematic side view of the light guide optics of a near-eye display shows an alternative exemplary "ghosting" light path set from an ambient light source behind the light guide optics;

[0030] Figure 3B It is shown Figure 3A An angle diagram showing the angular relationships between different parts of the ghosted ray path;

[0031] Figure 3C It is based on Figure 1A A magnified schematic side view of a modified implementation of the optical guide element in a near-eye display;

[0032] Figure 4 and Figure 5 It shows through Figure 1A A schematic top view of the observer's field of vision on a near-eye display;

[0033] Figure 6 It is similar to Figure 4 The view shows the angular range of ambient light incident from the rear of the light guide optics that can reach the observer's eye after a single reflection at a small internal plane of the light guide optics;

[0034] Figure 7 It is similar to Figure 6 The view shows a variant implementation that restricts the region containing internal facets to suppress certain ghosting light paths from reaching the observer's eye;

[0035] Figure 8A and Figure 8B It is similar to Figure 7 The view shows another aspect of the embodiment of the invention, using a baffle to block certain ghosting light paths from reaching the observer's eye, illustrated with and without an exemplary light path, respectively.

[0036] Figure 8C It is similar to Figure 8A The view shows a variation of a binocular near-eye display according to an aspect of the invention, which employs two non-coplanar light-guide optical elements deployed at an angle between them of 10 to 30 degrees to better conform to the curvature of the face, and shows the effect of this tilt on the baffle geometry.

[0037] Figure 9A This is a graph showing how the reflectivity varies according to the incident angle of the coating on an exemplary partially reflective surface (facet) according to an implementation of the present invention;

[0038] Figure 9BThis is a chart showing how the reflectivity of unmodified Fresnel reflection varies with the angle of incidence.

[0039] Figure 10A It is similar to Figure 1A A schematic side view illustrating a variant implementation using an external polarization filter;

[0040] Figure 10B It is similar to Figure 10A The view shows a variant implementation using an internal polarization filter;

[0041] Figure 10C and Figure 10D These are the cases without and with a lateral polarization filter, respectively. Figure 10B A top view of the implementation method;

[0042] Figure 10E It is similar to Figure 10A The view shows variant implementations using both internal and external polarization filters;

[0043] Figure 11 This is a schematic top view of an implementation of the present invention, showing a typical angle of incidence of light from an ambient light source compared to the field of view of a scene directly observed by an observer;

[0044] Figure 12 This is a graph showing how the reflectivity characteristics of a preferred antireflective coating, according to an embodiment of the invention, vary with the angle of incidence on the surface of the light-guiding optical element.

[0045] Figure 13 This is a schematic diagram of a micro-louvered film used in an implementation of a near-eye display according to another aspect of an embodiment of the present invention.

[0046] Figures 14A to 14C This is a schematic diagram of the eye position relative to a small plane position in various implementations of a near-eye display using a light-guide optics element, which includes two distinct sets of partially reflective surfaces with different orientations.

[0047] Figure 15A This is a schematic diagram of another example of a near-eye display using a light-guide optics element, which includes two distinct sets of partially reflective surfaces with different orientations, wherein the principal reflection polarization vectors of the two small plane sets are similarly aligned;

[0048] Figure 15B It is suitable for and Figure 15A A schematic diagram of the orientation of a polarization filter used in conjunction with optical guiding elements;

[0049] Figure 16A Based on Figure 14A A partial schematic diagram of a near-eye display using optical guide elements;

[0050] Figure 16B It is implemented as a binocular display with a non-uniform polarization filter. Figure 16A A schematic top view of a near-eye display; and

[0051] Figure 16C It is shown Figure 16A and Figure 16B The graph shows how the reflectivity varies depending on the incident angle of the partially reflective surface of the optical guide element in the implementation method. Detailed Implementation

[0052] This invention is a near-eye display.

[0053] The principles and operation of the near-eye display according to the present invention can be better understood by referring to the accompanying drawings and description.

[0054] Introduction and classification of "ghost images"

[0055] In order to fully understand the various aspects of the present invention, it is important to identify the different directions from which incident light arriving at the light guide optical element (LOE) may generate “ghosting” that could potentially trouble the observer’s eye.

[0056] As an introduction, Figure 1A An observer viewing through a near-eye display is illustrated schematically. Generally, a near-eye display includes a light-guiding optical element (LOE) or "waveguide" 10, having a planar and mutually parallel first main outer surface 11A and a second main outer surface 11B, and having edges that are generally not optically active. An image projector 2 is optically coupled to the LOE 10 to introduce illumination corresponding to an image into the LOE, such that the illumination propagates within the LOE through internal reflections at the main outer surfaces 11A and 11B. The optical coupling of the image projector 2 to the LOE 10 can be achieved via a coupling prism having an angled input surface or via a reflective coupling device, via the side edges of the LOE and / or one of the main outer surfaces of the LOE.

[0057] Examples of suitable image projectors (or “PODs”) – such as illumination sources typically all disposed on the surface of one or more PBS cubes or other prism devices, spatial light modulators such as LCOS sheets, and collimating optics – are well known in the art. Similarly, suitable coupling configurations for coupling an image to a LOE – such as by using a coupling reflector or by using a coupling prism at an appropriate angle – are well known in the art. The coupling between the image projector and the LOE can be direct or via an additional aperture expansion device for expanding the aperture size across which the image is injected into the plane of the LOE. For the sake of simplicity, projectors and coupling configurations will not be discussed further herein, and only combinations thereof are illustrated herein.

[0058] The near-eye display also includes a coupling device deployed to direct illumination toward the observer's eye from the LOE for viewing. The coupling device is shown herein as a plurality of mutually parallel partially reflective surfaces (or "facets") 12A, which are angled to the main outer surfaces 11A and 11B within the LOE 10. The facets typically have an angle-dependent coating to provide high transmittance at some angles and partial reflection at others, as discussed further below. Various implementations of LOEs including such facets are commercially available from LUMUS Corporation (Israel). Although the description herein primarily relates to facet-based coupling devices, those skilled in the art will understand that various aspects of the invention are also applicable to alternative coupling devices, such as those based on diffractive optical elements.

[0059] The near-eye display of the present invention is typically a head-mounted display, and therefore preferably includes a support device configured to support the LOE 10 relative to the observer's head when the second main outer surface 11B is facing the observer's eyes. The support device in Figure 1B The image is schematically shown as including a spectacle frame structure for supporting the display relative to the observer's ear on side 15. This is just one of many options that also includes a headband mounting structure and a display associated with the helmet. Details of the support device itself are not critical to the invention and will not be described in detail herein.

[0060] like Figure 1A Schematic illustration: Projector 2 injects light (solid arrow) corresponding to the desired image into the waveguide, and this light is coupled out of the waveguide towards the observer's eye. Light from object 4 in the scene (double-dotted line) travels through the waveguide to the observer with some intensity reduction. Various possible incident directions of the external light are marked by reference numeral 6 with two-letter codes indicating the direction: up, down, or side (U, D, or S respectively) and front or back (F or B respectively). Figure 1B The lateral direction is shown more clearly in the top view.

[0061] Figure 2A This is an enlarged schematic diagram showing the projector 2, waveguide 10, and selected internal facet 12A, which has an angle 13 relative to the parallel main outer surfaces forming the front and rear portions of the waveguide. In the exemplary configuration shown here, the projector is located at the top (e.g., Figure 1A (In this case, the facets are typically horizontally extending partial reflectors that couple light from the waveguide toward the observer's eye, although the partial reflectors are not necessarily precisely horizontal. In this example, only one beam of the image is shown for clarity, but in reality, the angular extension of the image (typically quasi-infinity) is projected along the waveguide and couples toward the eye. The spacing of the facets is presented as non-uniform to help show the reflection path, but the spacing of the facets is typically uniform.)

[0062] Here, the guiding light of the image is represented by rays 14A and 16A reflected from the outer surface of the waveguide. When ray 16A is incident on one of the small planes, a portion of ray 16A is reflected toward the observer as ray 18A. Figure 2B The corresponding ray directions in angular space are shown, where 12B corresponds to the plane angle of plane 12A, and the double arrows indicate the vector of that plane (perpendicular to the plane applicable when the diffraction element performs coupling). Vectors 14B, 16B, and 18B represent the directions of rays 14A, 16A, and 18A, respectively. Figure 2B and Figure 2C The dashed angle in the figure represents the TIR angle of the outer surface of waveguide 10, that is, light rays such as 18B falling within the shown angle range will escape from the waveguide, while light rays outside this range will be internally reflected.

[0063] Any architecture of waveguide and output coupling mechanism typically inherently contains various undesirable reflection mechanisms from the scene. Ray 20 originates from light source 6UF (a light source in front of the user and above the normal field of view of the real world as seen through the waveguide, typically in a sunlight or top-lit scene) and is refracted into the waveguide as ray 22A. This ray... Figure 2CIn angular space, this is represented as vector 22B. Most of this ray will pass through the waveguide and refract as ray 20A, which is outside the normal field of view and does not interfere with the observer. However, a portion of ray 22A can be reflected from one of the facets 12A (facet 12B) as ray 24A (vector 24B). This ray will be reflected by the outer surface of the LOE as ray 26A (vector 26B) and again by one of the facets 12A as ray 28A (vector 28B). Vector 28B is approximately the same as vector 14B, so the ray will continue to propagate toward the observer's eye in the same manner as 14A (14B). This is represented as rays 30A (equivalent to 16A) and 32A (equivalent to 18A).

[0064] Another possible mechanism for generating interfering ghosting illumination is to reflect light 22A from the rear surface 11B of the LOE and then reflect the light from the small facet 12A to generate output light 23A.

[0065] Figure 3A The optical path of a "single reflection" from source 102 in real space is described when an image is laterally injected into a light guide, where the extension direction of the facet is approximately vertical. This source is similar to... Figure 1B Source 6SB. Figure 3B The same process in angular space is described. Light from the source refracts into the waveguide as ray 106A (vector 106B), is reflected by plane 104A (plane 104B) as ray 112A (vector 112B), and refracts out of the waveguide. Compared to other types of reflection paths involving multiple plane reflections, this process involves only one reflection by the plane. Therefore, in some cases, this single, identical side reflection can be a particularly bright reflection. The reflection angle increases when the scene source is illuminated at an angle far from grazing incidence, as shown by comparing rays 110A and 112A with rays 106A and 108A.

[0066] The waveguide's geometry and its position relative to the eye determine the angular distribution of the reflections that will reach the eye. Figure 4 and Figure 5 A top view of the observer's head is shown. The relative positioning of the waveguide and the user's eye is determined by a support structure such as an eyeglass frame support structure or some other head-mounted support structure, which is omitted here for simplicity. In this example, as clearly indicated by the solid line arrows and the planeimetric angle, waveguide 10 is configured with an image illuminated from the side. The planeimetric plane in this example refers to the "vertical planeimetric plane".

[0067] The pupil can move within a certain range of positions and orientations, but as... Figure 4 and Figure 5The central ray from the central field is shown to pass through the center of the eyeball 101 towards the fovea in all viewing directions. The angular field of focus for the observer is described as angle 100. The equivalent angle exists vertically. For clarity, other considerations for expanding angle 100, such as IPD or eye-box tolerance, are not included in the specification.

[0068] Geometric obstruction of rear-side ghosting

[0069] according to Figures 8A to 8C In a first aspect of the embodiment of the invention shown, the near-eye display is provided with a light-blocking baffle (130L, 130R) that extends along a large portion of one of the edges of the LOE and protrudes from the plane of the second primary outer surface to block incident radiation from a range of grazing angles from reaching at least a portion of the second primary outer surface. The baffle protrudes in a direction toward the observer's eye, thereby forming an acute angle with the second primary outer surface, and most preferably in a direction toward the center of the observer's eyeball. This ensures that the baffle has minimal impact on the observer's peripheral field of vision, leaving the observer with the impression of an unrestricted field of vision.

[0070] The baffle preferably extends along the edge of the LOE, which is substantially parallel to the extension direction of the partial reflective surface parallel to the main surface. By geometric definition, the extension direction of the plane parallel to the main surface can be defined as the line of intersection between the plane containing one of the partial reflective surfaces and the plane of the first main outer surface. As used herein, "substantially parallel" preferably means directions that are parallel to each other or within approximately 20 degrees of each other.

[0071] According to the first option, the light-blocking baffles 130L and 130R are mechanically supported by attachment to LOE 10. Alternatively, the light-blocking baffles are mechanically supported by attachment to a support device (not shown in these figures).

[0072] The preferred geometry for implementing the baffle is considered as follows. As described above, Figures 3A to 3C The angle dependence of light rays that have undergone single reflections or single reflections from the front side 3C, which have varied according to the incident angle of illumination on the rear side of the light guides (3A, 3B), is shown. Figure 6 The meaning of this angle dependence is illustrated by a top view of a near-eye display deployed on the observer's head. Waveguide 10 reflects scene rays 120, ray 122, and grazing ray 124 from points 121R, 123R, and 125R on the waveguide toward the center of the observer's eyeball 101.

[0073] According to certain embodiments of the present invention, the final plane (i.e., the plane furthest from the image projector) is located where the reflection of the critical angle ray caused by the grazing incident rays from the scene (124R or 124L) can no longer reach the eye center 101, such as... Figure 7 As shown in Figure 125. The small plane in the waveguide of the right eye (or left eye) terminates at the point where the ray 124R (124L) is reflected onto the center 101 of the eye. According to Figure 6 It is obvious that no other light ray can be reflected onto 101, because there is no small plane for reflecting light there.

[0074] While the above methods can effectively avoid bright ghosting from single reflections of ambient lighting from the rear in some scenarios, for some applications, the geometric constraints on the position of the "last plane" may not provide a sufficient angular field of view. According to another aspect of the invention, using... Figure 6 The geometric relationships shown are, to what extent, needed to identify the required angular field of view (e.g., as...) Figure 6 Extending to position 123R, a limited angular range (e.g., the angle from ray 124 to ray 122) can be identified, which needs to be occluded to prevent single-reflection ghosting from the area of ​​the output plane from reaching the observer's central vision.

[0075] The light-blocking baffles 130L and 130R implemented based on these principles are typically relatively small and extend generally rearward from the periphery of the optical device, where they significantly reduce occlusion of the observer's peripheral vision compared to a completely side-blocking device. In some particularly preferred implementations, the baffle is implemented to extend generally towards the eye from the periphery of the optical device, and in some cases, the baffle is aligned with certain features and / or frame sides of the projector to have almost no occlusion effect on the observer's peripheral vision.

[0076] exist Figure 8A An example of such a shielding baffle is shown in the diagram. Baffles 130R and 130L are shown here as planes located at the edge of the waveguide and oriented towards 101, as indicated by the dotted lines. For a predefined virtual FOV, the length of waveguide 10 with the small plane is limited to 123R (123L). Figure 8B As shown, the optical path of the back reflection is defined and a baffle of length 130R (130L) is provided to block the optical path of the light reflected by the final facet. Figure 8C As shown, this scattering blocker can also be used with tilted waveguides. In addition to aesthetically conforming to the user's "facial curves," such tilted waveguides further relax the requirements for baffle size by projecting a longer "shadow" across the back surface of the waveguide for a given length of baffle.

[0077] Therefore, most preferably, the deployment of baffles 130L, 130R and the partially reflective surfaces prevents the light path from reaching the observer's eye after entering one of the first and second main outer surfaces and undergoing a single reflection from one of the partially reflective surfaces.

[0078] Exclude high angle of incidence rays

[0079] Another aspect of the embodiments of the invention, which is useful alone or in combination with other aspects described herein, relates to a method for managing incident light rays approaching the first (outer) principal outer surface 11A of LOE 10 at a high angle of incidence.

[0080] Refer again Figure 2A It should be noted that many of the problematic reflections in real-world light sources begin with high-angle incident rays, such as those schematically shown here as ray 20. If such rays could be excluded from the LOE entirely, this would clearly avoid the generation of troublesome incident radiation that reflects towards the observer's eye.

[0081] Therefore, an appropriate coating on the outer facet of waveguide 10 can reduce scene reflections, such as... Figure 11 and 12 As shown. Angle 100 represents the angular field from which an observer views the surrounding environment through waveguide 10.

[0082] exist Figure 12 The diagram illustrates a preferred implementation of the angular reflectivity of the first (outer) surface of a waveguide with an anti-reflective coating. Angle range 166 represents angle 100. Within this range, the waveguide's transmittance should be at its maximum. Light rays from the scene outside range 100 originate from in front 168 or behind 120 (limited by facet reflections, facets, or observer facial occlusion). The angular ranges of these rays are shown as follows. Figure 10B At 170. According to one aspect of the invention, the antireflective coating on the waveguide is modified to have high reflectivity at 170 and high transmittance at 166. (High reflectivity at high angles is a common characteristic of AR coatings designed for perpendicular light incidence.) This significantly reduces the amount of forward and backward scene illumination entering the waveguide 10 at high angles and reflected onto the eye through the internal facets.

[0083] Therefore, in one implementation of this aspect of the invention, the first (outer) main outer surface 11A is coated with a multilayer coating configured to provide antireflective properties for visible light incident at an angle of incidence of less than 40 degrees and to provide high reflectivity for at least a first polarization of visible light incident at an angle of incidence of greater than 70 degrees. Depending on the specific requirements of the field of view for which an observer can directly view the object via the LOE and the possible directions of incident ambient lighting in question, antireflective properties can preferably be provided for angles up to 50 degrees and / or high reflectivity for angles exceeding approximately 60 degrees; however, the closer these limits are, the higher the coating requirements become, to the point that achieving them may become impractical or unreasonably complex. In this context, "antireflective properties" preferably refers to a reflectivity of less than 5% and most preferably less than 3%. In this context, "high reflectivity" refers to a reflectivity exceeding 70% and preferably exceeding 80%, more preferably at least 90%, and in some particularly preferred cases at least 95%.

[0084] When considering the range of possible incident angles of external illumination, it can be difficult to achieve the desired exclusion of high incident angles (small grazing angles) across the entire field of view (FOV) and the entire visible spectrum. Therefore, in a particularly preferred embodiment of the invention, this reflectivity enhancement is optimized only for S-polarization of high-angle incident illumination. Alternative solutions are provided below for reducing the visibility of ghosting from P-polarized illumination from external light sources.

[0085] Specifically, refer to Figure 2A The refracted ray 22A, according to the above method, due to the coating on the outer surface, the residual light from the incident ray 20 refracted at the front main surface of the light guide and transmitted through the front main surface of the light guide may be substantially p-polarized. Some of the ghost reflection ray paths involve the subsequent reflection of ray 22A at the second (rear) main outer surface 11B of the substrate to generate ghost ray 23A. However, due to refraction at the interface away from the normal of the main surface, any portion of this light transmitted through the rear main surface 11B will continue on a sharply downward path 20A substantially parallel to the propagation direction of the ambient light 20 entering the front main surface of the LOE, and will not interfere with the eyes of the wearer of the near-eye display. Therefore, it is proposed to coat the rear surface of the LOE with an anti-reflective coating to increase the transmission of light with high incident angles. An effective anti-reflective coating that achieves p-polarization at all angles is more feasible. Therefore, this second aspect of the invention supplements the first aspect as follows: most of the incident external ghost illumination with S-polarization can be excluded by external reflection at the front surface 11A, while most of the P-polarized ghost illumination can be transmitted at the rear surface 11B. The result is that, compared to existing LOEs, the overall ghosting illumination following the path shown in Figure 2 is significantly reduced.

[0086] Therefore, according to this aspect of the invention, the second main outer surface 11B is advantageously coated with a multilayer coating that is configured to provide anti-reflective properties for visible light incident at an angle of incidence of less than 40 degrees and to provide low reflectivity for a second polarization of visible light that is perpendicular to a first polarization incident at an angle of incidence of between 70 degrees and at least about 85 degrees (preferably close to 90 degrees).

[0087] Referring again to Figure 2, regarding the alternative ray path that can generate ghosting 32A, ghosting can be formed by residual ambient light that penetrates into the LOE and is then reflected from the partially reflective facet of the light guide within a relatively limited angular range (e.g., from ray 22A to ray 24A or from ray 26A to ray 28A), which typically differs from the angular range (and polarization orientation) of the display signal propagation. Therefore, a design to modify the partially reflective surface coating is proposed to substantially reduce reflectivity within one or both of these specific angular ranges. Specifically, a facet coating that suppresses reflection of high-angle rays will tend to minimize the amount of light entering the guided mode (i.e., reflection from ray 22A to 24A), and thus suppress the intensity of ghosting 32A.

[0088] Micro-Venetian Blind Film Deformation

[0089] As an alternative or further implementation of the preceding aspect of the invention, a venetian blind film can be used to repel high-angle incident light. This venetian blind film is deployed in front of the outer surface of the LOE and configured to provide high light transmission from the external scene within the desired field of view while blocking light incident from high angles. Micro-venetian blind films are known and are commonly used as "privacy films" to limit the visibility of a computer display to a desired viewing angle. Examples of such films can be found in... The company commercially acquired it under the description of Advanced Light Control Film (ALCF).

[0090] exist Figure 13 The diagram schematically illustrates the structure of such a membrane, wherein the inner layer of the membrane comprises an array of opaque (or significantly reduced) micro-visors 300 supported within a transparent substrate 302, which defines a geometric constraint on the angle at which incident light can pass through the membrane. Commercially available privacy films typically comprise a one-dimensional array of micro-visors, i.e., all visors extend in the same direction. In this case, the membrane is preferably deployed relative to the LOE such that the visors extend horizontally, thereby blocking high-angle external light sources from above. Alternatively, a two-dimensional array of micro-visors can be used, having micro-visors extending in two vertical directions (typically in two separate layers of the membrane structure, one superimposed on the other) to provide exclusion of high-angle external light sources from all sides.

[0091] To avoid affecting the optical properties of the LOE for internal reflection from the main surface, it is generally preferred to avoid applying a light control film directly to the LOE surface. Alternatively, a suitable structure can be provided to ensure an air gap is maintained adjacent to the LOE, and the light control film is supported on a separate optical element (lens, etc.) slightly spaced from the LOE. Alternatively, a buffer or "isolation" layer with a sufficiently low effective refractive index can be provided to maintain the optical properties of the LOE. Examples of suitable materials for such a layer are commercially available and include aerogels and various other materials for similar purposes. According to another alternative implementation, an angle-selective reflective coating, typically implemented using multilayer dielectric coatings, can be provided to simulate the TIR of the relevant angular range of the image propagating within the LOE while allowing high transmission at small angles. This option also allows for direct optical attachment of the micro-visor film to the coated surface of the LOE without compromising its optical properties. Incidentally, in the case of polarization filters associated with one or both surfaces of the LOE mentioned herein, all the above-mentioned options for applying a supporting micro-visor film relative to the LOE without affecting its optical properties are equally applicable.

[0092] In a particularly preferred implementation, the micro-venetian blind layer 300 is associated with the first main outer surface 11A of the LOE 10 and blocks light incident from at least one direction at an angle of incidence greater than 70 degrees from entering the LOE. When using a micro-venetian blind layer 300 with a one-dimensional array of micro-venetian blinds, the micro-venetian blind layer is preferably deployed with its extension direction substantially horizontal. Alternatively, a micro-venetian blind layer having two arrays of micro-venetian blinds with substantially perpendicular extension directions can be used.

[0093] polarization filtering

[0094] The coating design on the facet has a significant impact on reflection filtering. Figure 9A The angular reflectance of typical coatings used on facets 12A and 40A is shown. In most cases, the reflectance, as shown, is polarization-dependent (or “polarization-sensitive”), which is also the basic Fresnel reflection characteristic. Figure 9B It is inherent in ).

[0095] Arrow 150 indicates angles corresponding to reflections 26A(B) to 28A(B). For this coating and at this incident angle, P-polarization reflects more than S-polarization. Arrow 154 indicates angles of reflection 22A(B) to 24A(B) with low reflectivity and no polarization selectivity. In alternative implementations of the facets for certain LOEs, 155 and 152 represent reflection angles with a pronounced dominant S-polarization. According to aspects of embodiments of the invention, as will now be described, polarization-dependent properties can be utilized to suppress real-world reflections using specific selections of the facet angle and / or coating profile.

[0096] Since reflections (e.g., 6UF or 6DF) can be controlled to have a predefined dominant polarization (e.g., through a suitable antireflective coating as described above, or through the properties of the facet itself), thus through, as Figure 10A The use of a polarization filter or "polarizer" 160U in front of the waveguide is shown to advantageously reduce ghosting reflections. Any suitable type of polarizer can be used, most preferably a structural (or "Cartesian") polarizer, and typically an absorptive polarizer. This polarizer will attenuate the unpolarized light from scene 4 by 50% (which in many cases may be necessary or desired anyway), but will attenuate the polarized upper frontal reflection 6UF or lower frontal reflection 6DF by even more. The polarizer orientation should preferably be set relative to the orientation of the plane of reflection (depending on whether the S or P block is perpendicular or horizontal to the plane).

[0097] In some cases, the LOE and the coupling device define at least one high-incident-angle polarization-dependent optical path that exits the LOE at an incident angle greater than 60 degrees onto one of the first and second main outer surfaces and toward the observer's eye, wherein the polarization-dependent optical path has a favorable polarization orientation. A polarization filter is then advantageously deployed to prevent external light with the favorable polarization orientation traveling along the polarization-dependent optical path from reaching the observer's eye. Figure 10A In the example above, the polarization filter 160U is externally deployed to filter the light entering the first (outer) main outer surface 11A.

[0098] One implementation of the invention is a waveguide with a planar coating designed to generate reflections of a real-world ghost image with polarization perpendicular to the polarization of the coupled projected image. In this case, it can be as follows: Figure 10B and Figure 10C As shown in 160I, the polarizer is placed on the inside facing the observer; that is, the polarization filter is deployed to filter light exiting the second primary outer surface toward the observer's eye. This configuration can block light also originating from the back of the waveguide (e.g., 6SB) and projected onto the eye twice through reflections by the polarizer, such as... Figure 10CObviously so. However, this configuration should only be used if the virtual image projected by the projector 2 illuminates the eye with minimal attenuation or distortion from the polarizer. In other words, the image illumination coupled from the LOE toward the observer's eye is essentially polarized using image polarization, and the polarization filter 160I is deployed to block light with polarization perpendicular to the image polarization.

[0099] In each case of using a polarizer, it will be noted that the polarizer orientation is specified by the facet structure, and the polarizer orientation is directed such that the polarization of real-world ghost illumination that may be reflected by the facet is reduced, while at least one polarization reflected at its specific angle of incidence according to the ghost ray path, concentrated by the facet, is allowed to pass. This results in a polarizer orientation with an angular offset (e.g., at least 20 degrees, or at least 30 degrees, and in some cases, between 60 and 120 degrees) deployed in sunglasses that, in many cases, transmit P-polarized light and repel S-polarized light from a horizontal surface.

[0100] Figure 10D The implementation of the side polarizer 160S on the system side is shown. In this way, the polarizer functions substantially the same as the polarizer 160U, to block polarization reflected from the waveguide (6SB) side. Preferably, the side polarizer is implemented together with the front polarizer 160U or 160I, so that the intensity visibility of the scene is the same from the front or the periphery (side).

[0101] If the 160I and 160S are used together (e.g.) Figure 10D As shown), the orientation of 160S is preferably perpendicular to 160I (i.e., cross polarization axes, for example, one vertical and one horizontal), resulting in complete blocking of all side reflections while maintaining peripheral visibility.

[0102] In some waveguide and planar array architectures, the virtually injected image is projected onto the eye under linear polarization. In such cases, a polarizer (e.g., ...) can be used closer to the eye. Figure 10B As shown), its effect is to filter some of the ghost reflections. However, in addition, some of the scene reflections are also reflected at the same polarization after polarization rotation in the waveguide. Since this polarization rotation does not occur on the direct scene ray 4, a second polarizer 232 with the same orientation as 230 is introduced. Figure 10E It will not have any additional effect on direct light 4, but will introduce additional attenuation on reflections 6UF and 6DF.

[0103] Variant implementation of LOE with two small plane sets

[0104] Some implementations of the LOE according to the invention employ two different, non-parallel sets of partially reflective surfaces to achieve two-dimensional optical aperture extension within the LOE. Many of the aforementioned features used to eliminate or reduce (collectively, “suppress”) unwanted reflections of real-world lighting (ghosting) are also applicable to 2D extended LOEs. Refer below to Figures 14A to 16C This explains some of the additional considerations in these applications.

[0105] exist Figure 14A In this design, facet 64A is positioned in front of the eye to reflect the guide image onto the eye. Facet 68A is used for optical aperture expansion via reflections from one guide image direction within the light guide to different guide image directions, without coupling to the eye. This makes it feasible in some cases to position these facets away from the eye-related field to eliminate the visibility of direct reflections from the facets. Figure 14A This illustrates the arrangement of the small plane 68A below the center of the eye. (As shown in the image) Figure 14B and 14C The non-overlapping architecture shown can further reduce overlap, where the eye views through a region with only one type of small plane.

[0106] Figure 15A Two overlapping sets of small planes are shown. Figures 10A to 10E The polarization structure presented can be applied to two small plane sets simultaneously. This can be achieved through methods such as... Figure 15A As shown in models 200A and 202A, one polarization is set to P polarization and the other to S polarization to manipulate reflections from the two polarizations to make them nearly parallel, thereby improving polarizer efficiency. Figure 15B The overlapping polarization orientations (200B and 202B) and preferred polarization orientations are shown to block combined polarization.

[0107] Alternatively, the polarizer can be set perpendicular (or parallel) to the small plane that generates the primary reflection.

[0108] Figure 16A A waveguide with two sets of facets is shown, wherein a tilted set of facets 220 is used for vertical aperture extension of the injected image, and a vertical set of facets 222 is used for horizontal extension. Facets 220 can be tilted relative to the outer facets of the waveguide. In this case, individual facet reflections will typically occur from the rear, as... Figure 6 As shown. However, if the facet 220 is perpendicular (or nearly perpendicular) to the outer surface of the light guide, a single reflection can occur from the direction in front of the light guide, such as... Figure 16B As shown by the arrow.

[0109] Figure 16C It shows a single reflection from the front ( Figure 16BThe typical reflection angles 224 and 226 represent the typical reflectivity of a facet coating (reflectivity as described in 3C for a facet with approximately or precisely perpendicular polarity). It is evident that back reflections tend to occur at an angle closer to perpendicularity, 224, where the dielectric coating will have a low difference between polarizations, while the front reflection angle 226 will have a high difference. Therefore, according to an aspect of the invention, a polarizer 228 is placed in front of the waveguide to filter out polarizations that would otherwise cause significant single front reflections.

[0110] Some coatings, such as wire grids or birefringent dielectrics (e.g., through 3M), also possess inherent polarization selectivity at the vertical angle. In this case, a side polarizer ( Figure 10D The 160S in the middle can be advantageously used to achieve effective reflection reduction.

[0111] Polarizer 228 can be designed with different orientations in front of 220 and 222, because different orientations of the plane will generate reflections with different polarizations. Alternatively, a nonlinear polarizer that gradually transitions between the two desired polarization orientations can be used to avoid sharp boundaries.

[0112] Reflection can originate from multiple reflections from more than one set of small planes. For example, in Figure 12 In case A, the reflection can have a certain degree of linear polarization after being reflected by plane 68A, and can become arbitrarily polarized after being reflected by plane 64A. In this case, the specific polarization of the reflection should be calculated, and a nonlinear polarizer should be used in conjunction with a waveguide. This can include a waveplate or other birefringent material with a linear polarizer.

[0113] The optical properties of reflections projected onto the eye can vary across the waveguide. Therefore, the methods described above can be used non-uniformly across the waveguide to achieve reflection suppression across the observer's entire field of view. This can include (but is not limited to):

[0114] Variable polarizer

[0115] · Variable wave plate

[0116] Variable coating for parallel and non-parallel facets

[0117] • Variable coating on the outer surface of the waveguide to alter transmittance and polarization

[0118] In all the above descriptions, a top-down configuration is equivalent to a side configuration, and a vertical plane is equivalent to a horizontal one. In other words, the arrangements are generally interchangeable; the system can be rotated 90 degrees. This includes baffles, coatings, and polarization.

[0119] It should be understood that the above description is intended to be illustrative only, and many other embodiments are possible within the scope of the invention as defined in the appended claims.

Claims

1. A near-eye display for projecting an image onto an observer's eye, the near-eye display comprising: a) A light-guiding optical element (LOE) having a planar and mutually parallel first main outer surface and second main outer surface, as well as an edge; b) A support device configured to support the light guide optical element (LOE) relative to the observer's head when the second main outer surface is in a facing relationship with the observer's eye. c) An image projector for projecting illumination corresponding to the image, the image projector being optically coupled to the light guide optical element (LOE) to introduce the illumination into the light guide optical element (LOE) so as to propagate within the light guide optical element (LOE) via internal reflections at the first main outer surface and the second main outer surface; d) A coupling device, which is deployed to couple the illumination toward the observer's eye from the light guide optical element (LOE); Its features also include: e) A light-blocking baffle extending along a large portion of one of the edges of the light-guiding optical element (LOE) and projecting from the plane of the second primary outer surface to block incident radiation from a range of grazing angles from reaching at least a portion of the second primary outer surface. The baffle projects toward the observer's eye, thereby forming an acute angle with the second primary outer surface without obstructing the line of sight from the center of the eyeball and the outer edge of the light guide. The coupling device includes a plurality of partially reflective surfaces that are parallel to each other and are deployed at an angle to the first main outer surface within the light guide optical element (LOE).

2. The near-eye display according to claim 1, wherein, The light-blocking baffle protrudes in a direction toward the center of the observer's eyeball.

3. The near-eye display according to claim 1, wherein, The deployment of the baffle and the partially reflective surface prevents light from reaching the observer's eye after entering one of the first and second main outer surfaces and undergoing a single reflection from one of the partially reflective surfaces.

4. The near-eye display according to claim 1, wherein, The partially reflective surface has an extension direction parallel to the second main outer surface, and wherein the baffle extends along a large portion of one of the edges within 20 degrees of each other with the extension direction of the partially reflective surface.

5. The near-eye display according to claim 1, wherein, The light-blocking baffle is mechanically supported by being attached to the light-guiding optical element (LOE).

6. The near-eye display according to claim 1, wherein, The light-blocking baffle is mechanically supported by being attached to the support device.

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