Optical System
An optical system employs a waveguide including a first set of partially-reflecting surfaces (“facets”) for progressively redirecting image illumination propagating from a coupling-in region towards a second region, and a second set of facets in the second region for progressively coupling-out the redirected image illumination towards the eye of a viewer. The first set of facets includes at least a first facet close to the coupling-in region, a third facet fare from the coupling-in region, and a second facet located on a medial plane between the first and the third facets. The second facet is located in a subregion of the medial plane such that image illumination propagating from the coupling-in region to the third facet passes through the medial plane without passing through the second facet.
The present invention relates to optical systems and, in particular, it concerns an optical system for two-dimensional expansion of an image from an image projector for display to a user.
A near eye display optical engine is shown in
The present invention is an optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by a user.
According to the teachings of an embodiment of the present invention there is provided, an optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system comprising a light-guide optical element (LOE) formed from transparent material, the LOE comprising: (a) a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation; (b) a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to the first orientation; (c) a set of mutually-parallel major external surfaces, the major external surfaces extending across the first and second regions such that both the first set of partially-reflecting surfaces and the second set of partially-reflecting surfaces are located between the major external surfaces, wherein the second set of partially-reflecting surfaces are at an oblique angle to the major external surfaces so that a part of image illumination propagating within the LOE by internal reflection at the major external surfaces from the first region into the second region is coupled out of the LOE towards the eye-motion box, and wherein the first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within the LOE by internal reflection at the major external surfaces from the coupling-in region is deflected towards the second region, wherein the first set of partially-reflecting surfaces comprises a first partially-reflecting surface proximal to the coupling-in region so as to contribute to a first part of a field of view of the user as viewed at the eye-motion box, a third partially-reflecting surface distal to the coupling-in region so as to contribute to a third part of a field of view of the user as viewed at the eye-motion box, and a second partially-reflecting surface lying in a medial plane between the first and the third partially-reflecting surfaces so as to contribute to a second part of a field of view of the user as viewed at the eye-motion box, wherein the second partially-reflecting surface is deployed in a subregion of the medial plane such that image illumination propagating from the coupling-in region to the third partially-reflecting surface and contributing to the third part of the field of view of the user as viewed at the eye-motion box passes through the medial plane without passing through the second partially-reflecting surface.
According to a further feature of an embodiment of the present invention, the coupling-in region comprises a coupling-in prism having a first planar surface that is a continuation of one of the major external surfaces in the first region, the coupling-in prism having a thickness dimension measured perpendicular to the major external surfaces that is greater than a thickness of the LOE.
According to a further feature of an embodiment of the present invention, the coupling-in prism presents a coupling-in surface and a transition line between the coupling-in prism as the LOE, the coupling-in surface defining an optical aperture of the coupling-in prism in a dimension parallel to the major external surfaces and the transition line defining an optical aperture of the coupling-in prism in a dimension perpendicular to the major external surfaces.
According to a further feature of an embodiment of the present invention, the first set of partially-reflecting surfaces further comprises at least one partially-reflecting surface located within a volume of the coupling-in prism.
There is also provided according to the teachings of an embodiment of the present invention, an optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system comprising a light-guide optical element (LOE) formed from transparent material, the LOE comprising: (a) a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation; (b) a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to the first orientation; (c) a set of mutually-parallel major external surfaces, the major external surfaces extending across the first and second regions such that both the first set of partially-reflecting surfaces and the second set of partially-reflecting surfaces are located between the major external surfaces, wherein the second set of partially-reflecting surfaces are at an oblique angle to the major external surfaces so that a part of image illumination propagating within the LOE by internal reflection at the major external surfaces from the first region into the second region is coupled out of the LOE towards the eye-motion box, and wherein the first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within the LOE by internal reflection at the major external surfaces from the coupling-in region is deflected towards the second region, wherein the coupling-in region comprises a coupling-in prism having a first planar surface that is a continuation of one of the major external surfaces in the first region, the coupling-in prism having a thickness dimension measured perpendicular to the major external surfaces that is greater than a thickness of the LOE, and wherein the coupling-in prism presents a coupling-in surface and a transition line between the coupling-in prism as the LOE, the coupling-in surface defining an optical aperture of the coupling-in prism in a dimension parallel to the major external surfaces and the transition line defining an optical aperture of the coupling-in prism in a dimension perpendicular to the major external surfaces.
According to a further feature of an embodiment of the present invention, the first set of partially-reflecting surfaces further comprises at least one partially-reflecting surface located within a volume of the coupling-in prism.
There is also provided according to the teachings of an embodiment of the present invention, an optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system comprising a light-guide optical element (LOE) formed from transparent material, the LOE comprising: (a) a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation; (b) a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to the first orientation; (c) a set of mutually-parallel major external surfaces, the major external surfaces extending across the first and second regions such that both the first set of partially-reflecting surfaces and the second set of partially-reflecting surfaces are located between the major external surfaces, wherein the second set of partially-reflecting surfaces are at an oblique angle to the major external surfaces so that a part of image illumination propagating within the LOE by internal reflection at the major external surfaces from the first region into the second region is coupled out of the LOE towards the eye-motion box, and wherein the first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within the LOE by internal reflection at the major external surfaces from the coupling-in region is deflected towards the second region, wherein the coupling-in region comprises a coupling-in prism having a first planar surface that is a continuation of one of the major external surfaces in the first region, the coupling-in prism having a thickness dimension measured perpendicular to the major external surfaces that is greater than a thickness of the LOE, and wherein the first set of partially-reflecting surfaces further comprises at least one partially-reflecting surface located within a volume of the coupling-in prism.
According to a further feature of an embodiment of the present invention, the coupling-in prism presents a coupling-in surface and a transition line between the coupling-in prism as the LOE, the coupling-in surface defining an optical aperture of the coupling-in prism in a dimension parallel to the major external surfaces and the transition line defining an optical aperture of the coupling-in prism in a dimension perpendicular to the major external surfaces.
According to a further feature of an embodiment of the present invention, the coupling-in prism is bonded to the LOE at an edge surface of the LOE. Alternatively, the coupling-in prism may be bonded to one of the major external surfaces of the LOE.
The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:
The present invention is an optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by a user.
By way of introduction, in the context of near-eye displays of the sort illustrated in
The waveguide has total-internal-reflection (TIR) boundary circles 228, indicating that images within these circles are not subject to TIR, and will be coupled-out so as to escape the waveguide.
Image 220A1 is coupled into the waveguide and propagates by TIR back and forth to 220A2. These images propagate along a very shallow trajectory along the waveguide where the shallowest part of the image is only 7 degrees from the waveguide plane (shown as angle 221 in
By way of one non-limiting example, the illustrations shown herein relate primarily to an image having aspect of 4:3 and diagonal field of 70 degrees injected into a waveguide having refractive index on 1.6. The design illustrated here generates a full image at an eyeball center 35 mm away from the waveguide (including eye-relief, eyeball-radius and margins). Adaptations of these implementations for different fields of view and aspect ratios can readily be implemented by a person ordinarily skilled in the art on the basis of the description herein.
One aspect of the present invention relates to optimization of deployment of partially-reflecting surfaces (or “facets”) in the first part of the waveguide responsible for the first dimension of optical aperture expansion. In an earlier patent application published as WO 2020/049542 A1 (“the '542 publication”), it has been suggested to deploy facets selectively within an envelope encompassing the facets which are needed for delivering image illumination to the eye-motion box from which the image is to be viewed.
An example of the resulting deployment of facets is illustrated in
According to the teachings of the '542 publication, certain parts of the first region 16 of the LOE outside the envelope of useful facets are implemented as an optical continuum (i.e., without partially reflecting internal surfaces), thereby reducing unwanted “ghost” reflections. Within the convex polygonal envelope, however, the facets are implemented as filling the entire width of the convex polygon, as illustrated in the drawing. As a result, the part of the field of view reflected from the facets located on the side distal from the coupling-in region pass through a long series of partially-reflecting facets before reaching the facets which deliver that part of the field of view to the eye-motion box.
According to one aspect of the present invention, the regions of facets required to deliver a given field of view to the eye-motion box is further refined to generate a concave polygon defining the required facet locations, thereby removing parts of the intermediate facets which would otherwise unnecessarily attenuate the image illumination directed to provide the part of the field reflected by facets furthest from the coupling-in region.
Thus, as illustrated in
In this context, it should be noted that the terms “proximal”, “distal” and “medial” are used herein to denote relative position with respect to a point or region of interest, in this case the coupling-in region 240, and refer to facets which are relatively closer (proximal) to, or relatively further (distal) from, the coupling-in region, or which are “towards the middle” (medial), without necessarily denoting the closest, furthest or central facet according to any specific geometrical definition.
A conceptual explanation will now be provided in order to facilitate a better understanding of the geometrical optics considerations which lead to the preferred design parameters for a given implementation of this aspect of the present invention. It should be noted that this explanation is given for informational purposes only, but that the utility of the invention as claimed is not dependent on the accuracy of any aspect of this explanation, and that effective and advantageous implementations of the claimed invention may alternatively be implemented by empirical methods.
All beams are transmitted from entrance pupil of the coupling-in region 240. The beams propagate within the waveguide until being reflected by set of parallel embedded reflectors 206L (facets). The facets in this diagram are assumed to be perpendicular to the external faces of the waveguide. Therefore, every line (solid followed by dashed) represents a different lateral section of the projected image field onto the observer's eye. The vertical field of every section is illuminated by plurality of overlapping beams (as viewed from front) propagating at different angles inclination (into the page) that are reflected by TIR (such internal reflection being illustrated in the side view of
For the purpose of simplifying the geometrical analysis, assume first that only the eyeball center 208 needs to be illuminated with the entire lateral field. This can theoretically be achieved by having infinitely small lateral facts 206L placed infinitely close to each other along the trajectory represented as 244A in
Other requirements include:
There is a finite minimum distance between the facets (i.e., they cannot be infinitely close); The aperture size cannot be too small; The facets must project continuous reflections towards the vertical expansion facets 206V.
In the case where the lateral expanding facets 206L are at an oblique angle to the major external surfaces of the LOE, the image is injected into the waveguide rotated relative to the axes of the waveguide, and the reflection from facets 206L rotates the image to the required orientation. Consequently, the curve for projecting onto the center of eyeball 208 will look like
Certain advantages of this aspect of the present invention can be better appreciated with reference to
One possible method for producing the lateral expansion section SL with ‘depression’ SD is shown in
Optionally, the combined prism and plates can be sliced, or can first be attached to another stack to be sliced together to generate the waveguide with all its sections.
The size of the waveguide as described above is shown in
Injecting a shallow image into a waveguide requires a relatively large coupling prism 202.
The prism 202M (and others described herein) preferably has a lower face that is parallel to the waveguide faces for consistent reflection, while the upper and side faces do not need specific optical properties, so their shapes can be other than the ones shown in these figures.
One option for reducing the overall dimensions of the coupling arrangement and image projector is illustrated in
Parenthetically, wherever a PBS arrangement is illustrated herein as sequentially reflecting and then transmitting light, or the reverse, it will be understood that a half-wave plate (for single transmission) or a quarter-wave plate (for double transmission) is appropriately placed to achieve rotation of the polarization as required for the functionality described. The polarization-rotating elements will not be mentioned in each case.
Alternative architectures for combining the image projector with the coupling prism are shown in
The structure of
This prism can also be provided with a coupling configuration including a lower refractive index part at its lower face equivalent to elements 286 or 228 described below with reference to
Turning now to
It is apparent from
In certain cases, it is possible to combine the earlier-mentioned integrated image projector (
Parenthetically, the deployment of facets 202T2 as illustrated in
Turning now to
It should be noted that the order of the slicing may be changed. It will also be appreciated that the illustrations of
Reducing the refractive index of the coupling prism 202M can also be used for reducing prism size and thereby making the system more compact.
A conceptually-similar approach of employing low refractive index material can be implemented using a low refractive index glass prism. When using a low refractive index glass prism, it is possible to compensate some of the dispersion generated by the angle in incidence of the light entering face 306.
In the embodiments detailed thus far, the facets employed 206L employed for the first set of facets have been orthogonal to the major external surfaces of the LOE, as detailed in
In this architecture the initial laterally propagating image 334A1 is coupled with 334A2 by TIR reflections. Only 334A2 is redirected towards the second region of the LOE 334B1 by tilted facets 336, which are at an oblique angle relative to waveguide faces. Facets 336 are preferably coated with multilayer dielectric coatings, as is known in the art, to provide the desired degree of partial reflectivity for the range of incident angles corresponding to image 334A2 (as in all of the above embodiments), while being primarily transparent to the range of incident angles corresponding to image 334A1, so as to minimize energy losses and formation of undesired reflections. The image 334B1 is coupled to 334B1 by TIR as it propagates at shallow angle along the second region of the waveguide. Image 334B2 is then coupled out to 334C by facets 338 (shown only in
The various coupling-in prism arrangements described above are configured to couple-in to the LOE both an image and its conjugate to “fill” the waveguide with the image. An alternative approach particularly attractive for shallow-angle image injection into the waveguide is direct injection of image into the waveguide, as illustrated in
In
If the partial reflector 374 has 50% reflectivity and 50% transmittance then for length equivalent to that of
Turning now to
Turning now to
For thin coating thickness, this configuration of gradual thinning of the coating may be sufficient. For thicker coatings, it may be advantageous to use a second mask over the region 302F (
It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.
Claims
1. An optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system comprising a light-guide optical element (LOE) formed from transparent material, said LOE comprising:
- (a) a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation;
- (b) a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to said first orientation;
- (c) a set of mutually-parallel major external surfaces, said major external surfaces extending across said first and second regions such that both said first set of partially-reflecting surfaces and said second set of partially-reflecting surfaces are located between said major external surfaces,
- wherein said second set of partially-reflecting surfaces are at an oblique angle to said major external surfaces so that a part of image illumination propagating within said LOE by internal reflection at said major external surfaces from said first region into said second region is coupled out of said LOE towards the eye-motion box, and wherein said first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within said LOE by internal reflection at said major external surfaces from said coupling-in region is deflected towards said second region,
- wherein said first set of partially-reflecting surfaces comprises a first partially-reflecting surface proximal to the coupling-in region so as to contribute to a first part of a field of view of the user as viewed at the eye-motion box, a third partially-reflecting surface distal to the coupling-in region so as to contribute to a third part of a field of view of the user as viewed at the eye-motion box, and a second partially-reflecting surface lying in a medial plane between said first and said third partially-reflecting surfaces so as to contribute to a second part of a field of view of the user as viewed at the eye-motion box, wherein said second partially-reflecting surface is deployed in a subregion of said medial plane such that image illumination propagating from said coupling-in region to said third partially-reflecting surface and contributing to the third part of the field of view of the user as viewed at the eye-motion box passes through said medial plane without passing through said second partially-reflecting surface.
2. The optical system of claim 1, wherein said coupling-in region comprises a coupling-in prism having a first planar surface that is a continuation of one of said major external surfaces in said first region, said coupling-in prism having a thickness dimension measured perpendicular to said major external surfaces that is greater than a thickness of said LOE.
3. The optical system of claim 2, wherein said coupling-in prism presents a coupling-in surface and a transition line between said coupling-in prism as said LOE, said coupling-in surface defining an optical aperture of said coupling-in prism in a dimension parallel to said major external surfaces and said transition line defining an optical aperture of said coupling-in prism in a dimension perpendicular to said major external surfaces.
4. The optical system of claim 2, wherein said first set of partially-reflecting surfaces further comprises at least one partially-reflecting surface located within a volume of said coupling-in prism.
5. An optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system comprising a light-guide optical element (LOE) formed from transparent material, said LOE comprising:
- (a) a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation;
- (b) a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to said first orientation;
- (c) a set of mutually-parallel major external surfaces, said major external surfaces extending across said first and second regions such that both said first set of partially-reflecting surfaces and said second set of partially-reflecting surfaces are located between said major external surfaces,
- wherein said second set of partially-reflecting surfaces are at an oblique angle to said major external surfaces so that a part of image illumination propagating within said LOE by internal reflection at said major external surfaces from said first region into said second region is coupled out of said LOE towards the eye-motion box, and wherein said first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within said LOE by internal reflection at said major external surfaces from said coupling-in region is deflected towards said second region,
- wherein said coupling-in region comprises a coupling-in prism having a first planar surface that is a continuation of one of said major external surfaces in said first region, said coupling-in prism having a thickness dimension measured perpendicular to said major external surfaces that is greater than a thickness of said LOE,
- and wherein said coupling-in prism presents a coupling-in surface and a transition line between said coupling-in prism as said LOE, said coupling-in surface defining an optical aperture of said coupling-in prism in a dimension parallel to said major external surfaces and said transition line defining an optical aperture of said coupling-in prism in a dimension perpendicular to said major external surfaces.
6. The optical system of claim 5, wherein said first set of partially-reflecting surfaces further comprises at least one partially-reflecting surface located within a volume of said coupling-in prism.
7. An optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system comprising a light-guide optical element (LOE) formed from transparent material, said LOE comprising:
- (a) a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation;
- (b) a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to said first orientation;
- (c) a set of mutually-parallel major external surfaces, said major external surfaces extending across said first and second regions such that both said first set of partially-reflecting surfaces and said second set of partially-reflecting surfaces are located between said major external surfaces,
- wherein said second set of partially-reflecting surfaces are at an oblique angle to said major external surfaces so that a part of image illumination propagating within said LOE by internal reflection at said major external surfaces from said first region into said second region is coupled out of said LOE towards the eye-motion box, and wherein said first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within said LOE by internal reflection at said major external surfaces from said coupling-in region is deflected towards said second region,
- wherein said coupling-in region comprises a coupling-in prism having a first planar surface that is a continuation of one of said major external surfaces in said first region, said coupling-in prism having a thickness dimension measured perpendicular to said major external surfaces that is greater than a thickness of said LOE,
- and wherein said first set of partially-reflecting surfaces further comprises at least one partially-reflecting surface located within a volume of said coupling-in prism.
8. The optical system of claim 7, wherein said coupling-in prism presents a coupling-in surface and a transition line between said coupling-in prism as said LOE, said coupling-in surface defining an optical aperture of said coupling-in prism in a dimension parallel to said major external surfaces and said transition line defining an optical aperture of said coupling-in prism in a dimension perpendicular to said major external surfaces.
9. The optical system of claim 2, wherein said coupling-in prism is bonded to said LOE at an edge surface of said LOE.
10. The optical system of claim 2, wherein said coupling-in prism is bonded to one of said major external surfaces of said LOE.
11. The optical system of claim 3, wherein said coupling-in prism is bonded to said LOE at an edge surface of said LOE.
12. The optical system of claim 3, wherein said coupling-in prism is bonded to one of said major external surfaces of said LOE.
13. The optical system of claim 4, wherein said coupling-in prism is bonded to said LOE at an edge surface of said LOE.
14. The optical system of claim 4, wherein said coupling-in prism is bonded to one of said major external surfaces of said LOE
15. The optical system of claim 5, wherein said coupling-in prism is bonded to said LOE at an edge surface of said LOE.
16. The optical system of claim 5, wherein said coupling-in prism is bonded to one of said major external surfaces of said LOE.
17. The optical system of claim 6, wherein said coupling-in prism is bonded to said LOE at an edge surface of said LOE.
18. The optical system of claim 6, wherein said coupling-in prism is bonded to one of said major external surfaces of said LOE.
19. The optical system of claim 7, wherein said coupling-in prism is bonded to said LOE at an edge surface of said LOE.
20. The optical system of claim 7, wherein said coupling-in prism is bonded to one of said major external surfaces of said LOE.
Type: Application
Filed: Aug 23, 2021
Publication Date: Aug 25, 2022
Inventors: Yochay DANZIGER (Kfar Vradim), Shimon GRABARNIK (Rehovot), Ronen CHRIKI (Lod), Eitan RONEN (Rehovot), Elad SHARLIN (Mishmar David)
Application Number: 17/640,004