Optical systems including light guide optical elements with two-dimensional magnification

Abstract

To provide an optical system including a light-guide optical element (LOE) with first and second sets of mutually-parallel, partially-reflecting surfaces at different orientations.SOLUTION: Both sets of partially-reflecting surfaces are located between parallel major external surfaces. A third set of at least partially-reflecting surfaces, deployed at a coupling-in region, receives image illumination injected from a projector with an optical aperture having a first in-plane width and directs the image illumination via reflection of at least part of the image illumination at the third set of at least partially-reflective facets toward the first set of partially-reflective facets with an effective optical aperture having a second width larger than the first width.SELECTED DRAWING: Figure 4A

Description

Technical Field

[0001] The present invention relates to an optical system, and more particularly to an optical system including a light guiding optical element (LOE) for achieving optical aperture expansion.

Background Art

[0002] Many near-eye display systems include a transparent light guiding optical element (LOE) or a "light pipe" placed in front of the user's eyes, which transmits the image within the LOE by internal reflection and then couples out the image in the direction of the user's eyes by means of a suitable output coupling mechanism. The output coupling mechanism can be based on an embedded partial reflector or "facet", or can use a diffraction pattern. The following description mainly refers to the facet-based coupling-out arrangement, but it should be understood that various features of the present invention are also applicable to the diffraction arrangement.

[0003] Two-dimensional aperture expansion in a light pipe using internal orthogonal facets is described in FIG. 13 of Patent Document 1 and reproduced herein as FIG. 1A. The reference numbers referring to the prior art drawings are shown in parentheses herein. The light from the projector (20) propagates within the light pipe and is reflected by the facets (22a)-(22c) in the direction of the facet (23), which causes the light to be coupled out in the direction of the observer.

[0004] Patent Document 2 of the PCT publication discloses a similar concept using non-orthogonal facets. FIGS. 2 and 29 of the PCT publication are reproduced herein as FIGS. 1B and 1C, respectively. The first set of facets indicated by (32) herein is non-orthogonal, and thus only one mode of propagation is reflected. The two configurations shown are different in terms of whether the regions containing the two sets of facets overlap (FIG. 1B) or do not overlap (FIG. 1C).

Prior Art Documents

[0005] [Patent Document 1] US6829095B2 [Patent Document 2] WO2019 / 142177A1 [Overview of the project]

[0006] This invention is an optical system.

[0007] According to the teaching of embodiments of the present invention, an optical system is provided for directing image illumination injected in a coupling-in region toward a user for viewing, the optical system comprising a light guide optical element (LOE) formed of a transparent material, the LOE comprising: (a) a first region comprising a first set of planar, mutually parallel partial reflective surfaces having a first orientation; (b) a second region comprising a second set of planar, mutually parallel partial reflective surfaces having a second orientation not parallel to the first orientation; and (c) a set of mutually parallel main outer surfaces, the main outer surfaces extending across the first and second regions such that both the first set of partial reflective surfaces and the second set of partial reflective surfaces are located between the main outer surfaces, the second set of partial reflective surfaces being inclined obliquely with respect to the main outer surfaces, and as a result, a portion of the image illumination propagating within the LOE by internal reflection at the main outer surfaces from the first region to the second region is L The optical system is configured such that the image illumination is coupled out from the OE toward the user, and a first set of partially reflective surfaces deflects a portion of the image illumination propagating within the LOE by internal reflection at the main outer surface from the coupling-in region toward a second region, and the optical system further includes a third set of planar, mutually parallel, at least partially reflective surfaces arranged in the coupling-in region, the arrangement of which the image illumination injected from the projector is received by an optical aperture having a first width measured parallel to the main outer surface, and the image illumination is directed toward a first set of partially reflective facets having an effective optical aperture having a second width measured parallel to the main outer surface, via reflection of at least a portion of the image illumination in the third set of at least partially reflective facets, wherein the second width is greater than the first width.

[0008] A further feature of an embodiment of the present invention is that a third set of at least partially reflective surfaces has a first sequence of continuously increasing reflectances in the order in which the image illumination reaches its at least partially reflective surfaces, and the first set of partially reflective surfaces has a second sequence of continuously increasing reflectances in the order in which the image illumination reaches its partially reflective surfaces, the second sequence beginning with a reflectance smaller than the last reflectance of the first sequence.

[0009] According to further features of embodiments of the present invention, the final reflectance of a first sequence of continuously increasing reflectances is greater than 90%.

[0010] According to further features of embodiments of the present invention, the majority of the image illumination directed toward a first set of partially reflective surfaces receives just one reflection from at least a third set of partially reflective surfaces.

[0011] According to further features of embodiments of the present invention, the majority of the image illumination directed toward a first set of partially reflective surfaces receives two reflections from at least a third set of partially reflective surfaces.

[0012] According to further features of embodiments of the present invention, a third set of at least partially reflective surfaces is integrated as part of the LOE and located between the main outer surfaces.

[0013] According to further features of embodiments of the present invention, at least a third set of partially reflective surfaces is parallel to the first set of partially reflective surfaces.

[0014] According to further features of embodiments of the present invention, at least a third set of partially reflective surfaces is not parallel to the first set of partially reflective surfaces.

[0015] According to further features of embodiments of the present invention, the inter-surface spacing of at least a third set of partially reflective surfaces is smaller than the inter-surface spacing of a first set of partially reflective surfaces.

[0016] According to further features of embodiments of the present invention, the surface area of ​​each of the third set of at least partially reflective surfaces is smaller than the surface area of ​​each of the first set of partially reflective surfaces.

[0017] According to further features of embodiments of the present invention, the first region and the second region do not overlap.

[0018] A further feature of an embodiment of the present invention provides an image projector for projecting a collimated image having a field of view with respect to the optical axis, the image projector is optically coupled to a Loege (LOE) to introduce a collimated image into the LOE as a propagated image propagated within the LOE by internal reflection at a major outer surface via a third set of at least partially reflective surfaces in a coupling-in region, the propagated image being partially reflected by a first set of partially reflective surfaces to produce a deflected propagated image propagated within the LOE by internal reflection at a major outer surface, and the deflected propagated image being partially reflected by a second set of partially reflective surfaces to produce a couple-out image directed outward toward the user from one of the major outer surfaces. [Brief explanation of the drawing]

[0019] The present invention is described herein as merely one example with reference to the accompanying drawings. [Figure 1A] As mentioned above, this corresponds to Figure 13 in Patent Document 1. [Figure 1B] As mentioned above, this corresponds to Figure 2 in Patent Document 2 of the PCT patent application publication. [Figure 1C] As mentioned above, this corresponds to Figure 29 in Patent Document 2 of the PCT patent application publication. [Figure 2A] This is a schematic isometric view of an optical system implemented using a light guide optical element (LOE), configured and operating according to the teachings of the present invention, illustrating a top-down configuration. [Figure 2B] A schematic isometric view of an optical system implemented using a light guiding optical element (LOE) configured and operating in accordance with the teachings of the present invention, illustrating a side injection configuration. [Figure 3A] A schematic view of the effect of different spacings of a partially reflective internal surface when redirecting image illumination from a projector having a constant optical aperture width from a first direction to a second direction within a substrate. [Figure 3B] A schematic view of the effect of different spacings of a partially reflective internal surface when redirecting image illumination from a projector having a constant optical aperture width from a first direction to a second direction within a substrate. [Figure 4A] A schematic front view of a light guiding optical element (LOE) in accordance with the teachings of an embodiment of the present invention, illustrating a three - stage expansion of an optical aperture to illumination coupled out in the direction from the projector to the observer. [Figure 4B] A schematic isometric depiction of two implementations of the LOE of FIG. 4A using orthogonal partially reflective internal surfaces, for the first two stages of aperture expansion. [Figure 4C] A schematic isometric depiction of two implementations of the LOE of FIG. 4A using oblique partially reflective internal surfaces, for the first two stages of aperture expansion. [Figure 5A] A front view of a variant implementation of the LOE of FIG. 4A, wherein the partially reflective internal surfaces for performing two stages of optical aperture expansion are disposed in a region where they at least partially overlap. [Figure 5B] An isometric view of a variant implementation of the LOE of FIG. 4A, wherein the partially reflective internal surfaces for performing two stages of optical aperture expansion are disposed in a region where they at least partially overlap. [Figure 6] A schematic depiction representing in angular space (polar coordinates) the relative directions of image illumination through various stages of propagation through the LOE of FIG. 4C. [Figure 7A] A schematic front view of two further variant implementations of the LOE of FIG. 4A, illustrating options for side - injecting image illumination. [Figure 7B]Figure 4A shows schematic front views of two further variations of the LOE implementation, illustrating an option for lateral injection of image illumination. [Figure 8A] Figure 4A shows a schematic representation of the production sequence for the LOE. [Figure 8B] Figure 5A shows a schematic representation of the production sequence for the LOE. [Figure 9] Figure 4A is a schematic front view of a further modified implementation of the LOE, in which the geometric shape of the LOE region has been changed. [Figure 10A] Figure 4A is a schematic front view of a further variant implementation of the LOE, employing a rectangular waveguide section for the preliminary stage of optical aperture expansion. [Figure 10B] Figure 4A is an isometric front view of a further variant implementation of the LOE, employing a rectangular waveguide section for the preliminary stage of optical aperture expansion. [Figure 11A] Figure 4A is a schematic isometric view of a pre-assembly implementation of a further variation of the LOE, employing a slab with at least partially reflective internal facets for a preliminary stage of optical aperture expansion without light guiding by TIR. [Figure 11B] Figure 4A is a schematic isometric view of an assembled implementation of a further variation of the LOE, employing a slab with at least partially reflective facets inside for a preliminary stage of optical aperture expansion without light guiding by TIR. [Figure 12A] Figure 4A is a schematic isometric view of a pre-assembly implementation of a further variation of the LOE, using a slab with at least partially reflective internal facets for a preliminary step of optical aperture expansion by light guiding through surfaces not parallel to the main surface of the LOE. [Figure 12B] Figure 4A is a schematic isometric view of an assembled implementation of a further variation of the LOE, using a slab with at least partially reflective internal facets for a preliminary step of optical aperture expansion by light guiding through surfaces not parallel to the main surface of the LOE. [Modes for carrying out the invention]

[0020] One embodiment of the present invention provides an optical system including a light guide optical element (LOE) for achieving optical aperture expansion, for use with head-up displays such as near-eye displays, which may be virtual reality displays or, more preferably, augmented reality displays.

[0021] An exemplary implementation of a device in the form of a near-eye display, generally designated (10), using an LOE (12), according to the teachings of embodiments of the present invention, is schematically illustrated in Figures 2A and 2B. The near-eye display (10) uses an engineered-coupled compact image projector (or "POD") (14) to inject an image into an LOE (synonymously called a "waveguide," "substrate," or "slab") (12), where the image illumination is captured in one dimension by internal reflections on a set of mutually parallel, planar external surfaces. The light strikes a set of partially reflective surfaces (synonymously called "facets") that are parallel to each other and inclined obliquely with respect to the propagation direction of the image light, and each consecutive facet deflects a portion of the image light in the deflection direction, which is captured / guided by internal reflections within the substrate. This first set of facets, not individually shown in Figures 2A and 2B, is located in a first region of the LOE designated (16). This partial reflection across consecutive facets achieves one dimension of optical aperture expansion.

[0022] In a first set of preferred but not limiting examples of the present invention, the aforementioned set of facets is orthogonal to the main outer surface of the substrate. In this case, both the injected image and its conjugate, which undergoes internal reflection as it propagates within region (16), are deflected, resulting in a conjugate image that propagates in the deflected direction. In another preferred but not limiting example, the first set of partially reflective surfaces is angled obliquely to the main outer surface of the LOE. In the latter case, either the injected image or its conjugate forms a desired deflected image propagating within the LOE, while other reflections are minimized, for example, by using an angle-selective coating on the facet that makes the facet relatively transparent to a range of incident angles provided by the image for which reflection is not desired.

[0023] A first set of partially reflective surfaces deflects the image illumination from a first direction of propagation captured by total internal reflection (TIR) ​​within the substrate to a second direction of propagation similarly captured by TIR within the substrate.

[0024] Subsequently, the deflected image illumination moves to a second substrate region (18), which may be implemented as an adjacent separate substrate or as a continuum of a single substrate, where a coupling-out array (either a further set of partial reflective facets or a diffraction optical element) gradually couples out a portion of the image illumination toward the observer's eye located within a region defined as the eye motion box (EMB), thereby achieving two dimensions of optical aperture expansion. The entire device may be implemented separately for each eye, preferably supported against the user's head, with each LOE(12) facing the user's corresponding eye. In one particularly preferred option, as illustrated herein, the support configuration is implemented as a spectacle frame with sides (20) for supporting the device against the user's ears. Other forms of support configurations are also possible, including, but not limited to, devices suspended from a headband, visor, or helmet.

[0025] A particularly preferred feature of one embodiment of the present invention is that the optical system further includes a third set of planar, mutually parallel, at least partially reflective surfaces ("facets") arranged in a coupling region. The third set of facets is designated as region (15), although not shown individually in Figures 2A and 2B. The third set of facets receives image illumination injected from a projector (14) having an optical aperture having a first width measured parallel to the main outer surface of the LOE (12), and is positioned to direct the image illumination toward a first set of partially reflective facets in region (16), which has a second, wider effective optical aperture measured parallel to the main outer surface of the LOE, via reflection of at least some of the image illumination by the facets of region (15). The importance of this aperture expansion will be discussed further below.

[0026] The third set of facets (15) is placed in the optical path between the projector (14) and the first set of facets (16) in the coupling region. The phrase “in the coupling region” is used herein to include both cases where the third set of facets is incorporated into the LOE in the coupling region and where the third set of facets is outside the LOE, both of which are described in detail below.

[0027] In the drawings and claims, the X-axis extends horizontally (Figure 2A) or vertically (Figure 2B) in the direction in which the first region of the LOE extends overall, and the Y-axis extends perpendicularly thereto, i.e., vertically in Figure 2A and horizontally in Figure 2B.

[0028] Very broadly speaking, the first LOE, or the first region (16) of LOE(12), can be considered to achieve aperture expansion in the X direction, while the second LOE, or the second region (18) of LOE(12), can be considered to achieve aperture expansion in the Y direction. It should be noted that the orientation illustrated in Figure 2A is considered a “top-down” implementation, where the image illumination entering the main (second region) of the LOE enters from the top, while the orientation illustrated in Figure 2B is considered a “side-injection” implementation, where the axis referred to herein as the Y-axis is horizontally positioned. In the remaining drawings, various features of certain embodiments of the present invention will be illustrated in terms of the “top-down” orientation, similar to Figure 2A. However, it should be understood that all of these features are equally applicable to side-injection implementations, which are also within the scope of the present invention. In some cases, other intermediate orientations are also applicable and are included within the scope of the present invention unless expressly excluded.

[0029] The POD used with the device of the present invention is preferably configured to produce a collimated image, where the light from each image pixel is a parallel beam infinitely collimated in the angular direction corresponding to the pixel position. Thus, the image illumination spreads over an angular range corresponding to a two-dimensional field of view.

[0030] The image projector (14) includes at least one light source, which is generally positioned to illuminate a spatial light modulator, such as an LCOS chip. The spatial light modulator modulates the projection intensity of each pixel of the image, thereby generating the image. Alternatively, the image projector may include a scanning arrangement, commonly implemented with a fast scanning mirror, which scans the illumination from the laser light source across the image plane of the projector while the beam intensity changes in synchronization with the pixel-based motion, thereby projecting a desired intensity onto each pixel. In either case, a collimating optical system is provided for generating an infinitely collimated output projected image. Some or all of the above components are typically located on the surface of one or more polarizing beam splitter (PBS) cubes or other prism arrays, as is well known in the art.

[0031] Optical coupling of the image projector (14) to the LOE (12) can be achieved by a suitable optical coupling, for example, via a coupling prism with an obliquely angled input surface, or via a reflective coupling arrangement, via one of the side edges and / or main external surfaces of the LOE. If a third set of facets (15) is outside the LOE, the third set of facets is preferably integrated with the coupling-in arrangement, as illustrated below with reference to Figures 11A-11C. Further details of the coupling-in configuration are not important to the present invention and are shown only schematically herein.

[0032] The near-eye display (10) includes various additional components, and will generally include a controller (22) that operates an image projector (14), and will generally be understood to use power from a small onboard battery (not shown) or some other suitable power source. The controller (22) will be understood to include all the necessary electrical components, such as at least one processor or processing circuit for driving the image projector, as is all known in the art.

[0033] Referring here to Figures 3A and 3B, these schematically illustrate the shape of image illumination from a projector having an optical aperture of a certain width with a first set of partially reflective internal surfaces. To obtain uniform illumination, the aperture width (100) of the projector must be such that reflected rays from one facet are adjacent to reflected rays from the next facet, avoiding the black lines of the display. In some cases, it is desirable that each viewing direction receives reflections from two or more facets, most preferably from a certain number of facets across the aperture, and that there is sufficient overlap so that the uniformity of the observed image is improved. Figures 3A and 3B illustrate the case where a beam from a projector (2) with aperture width (100) illuminates a different number of facets (102 and 109). Reflected light (104, 106, 110 and 108) propagates in the direction of other facets (not shown in this figure). Preferably, a complete and constant number of facets are illuminated. In Figure 3A, the number varies between 2 and 3, but in Figure 3B, it remains constant, with two facets contributing to the output across the entire aperture. The wider the aperture width (100), the more facets are illuminated, and the more uniform the transmitted image becomes.

[0034] To produce a uniform image for a given facet spacing, the aperture width must be appropriately modified. Therefore, larger facet spacing requires the use of a larger aperture. Narrower facet spacing across the waveguide increases manufacturing complexity and cost. On the other hand, manufacturing a projector with a large aperture increases the size of the projector. These conflicting design considerations are reconciled, according to aspects of the present invention, by performing a preliminary stage of optical aperture expansion between the projector and what is referred to above as the first set of facets. This is achieved using an additional set of facets (referred herein to as the "third set of at least partially reflective internal surfaces").

[0035] Figure 4A schematically shows a front view of a waveguide according to this embodiment of the present invention. The aperture of projector (2) is small. Two arrows originating from this projector represent the rays at the ends of this aperture. Light from this projector is coupled to waveguide section (200) having facet (202) (which is a preliminary, additional, “third” set of facets). As the light propagates through this section (200), the lateral aperture dimension ("width") in the plane of the LOE expands as reflections from the successive facets (202) partially redirect the light again towards section (207) containing facet (204) (referred to above as the “first” set of facets). The light reflected from facet (204) is redirected again towards section (209) containing facet (206) (referred to above as the “second” set of facets) and couples out towards the observer.

[0036] Figure 4B shows an isometric view of Figure 4A. In this specification, since section (200) has the same width (waveguide thickness) as (207) and (209), it can be seen that sections (200), (207), and (209) are integrated within adjacent LOEs sandwiched between mutually parallel outer surfaces. Induction throughout these sections is due to total internal reflection (TIR) ​​from these outer surfaces. Light transmission between sections is preferably free from disturbances or breaks, and the separation lines shown between sections in various figures (e.g., front views in Figures 4A, 5A, 7A, 7B, and 9) are for ease of understanding.

[0037] Facet (206) is designed to transmit landscape light, allowing the observer to directly view the external scene beyond the LOE, and therefore has a relatively low reflectivity, generally less than 50%. In some configurations, facet (204) is also designed to transmit landscape light, and therefore has a relatively low reflectivity, generally less than 50%. In other configurations where facet (204) is not part of the “viewing area” of the LOE, a higher reflectivity may be used. Facet (202) is preferably outside the viewing area of ​​the LOE and therefore does not need to transmit landscape light. Therefore, a high reflectivity is preferably used to obtain high efficiency for light transmission. Preferably, the last facet (211) of area (200) has a high reflectivity of at least 90%, and preferably 100%. Section (200) is not designed to transmit landscape light and is therefore preferably covered (not shown), and therefore external light does not pass through it. Alternatively, this section (200) of the waveguide may be covered with a reflective coating such as silver.

[0038] To provide relatively uniform image illumination intensity across the optical aperture, it is most preferable that one or more sets of partial reflective surfaces, and preferably each set, have a sequence of continuously increasing reflectance in the order in which the image illumination reaches its partial reflective surface. For example, for the waveguide region (200), a sequence of three facets with reflectances of 33%, 50%, and 100% is effective in reflecting approximately one-third of the incident illumination from each consecutive surface. Similarly, for a sequence of four facets, values ​​of 25%, 33%, 50%, and 100% are effective in reflecting approximately one-quarter of the incident illumination from each surface. For facets within the viewing area through which the observer observes the external scene, the reflectance values ​​are lower and the proportional increase between facets is smaller, but the fundamental concept of an increasing sequence to compensate for the lower proportion of illumination intensity remaining in the propagating image illumination remains the same. (If the ideal reflectance values ​​of consecutive facets are relatively close, two or more consecutive facets within the LOE region may implement the same reflectance value as a simplification of manufacturing, but the sequence is still referred to as "continuously increasing" because the sequence increases monotonically to provide the above-mentioned effect of improving uniformity.) Thus, for example, facet (204) has a second sequence of continuously increasing reflectance in the order in which the image illumination reaches its facet, in which case the second sequence begins with a reflectance smaller than the last reflectance of the first sequence (of facet (204)).

[0039] In the configuration of Figure 4A, most of the image illumination directed towards facet (204) receives exactly one reflection from facet (202). As illustrated by the boundary arrows shown in LOE section (207), the spacing of facet (202) is close, ensuring the continuity of image illumination redirected again towards facet (204) across the enlarged effective aperture. This allows facet (204) to use a larger spacing, thereby reducing the manufacturing complexity and cost for the majority of the waveguide. For example, if facet (202) enlarges the aperture by a factor of three (using three facets with continuously increasing reflectivity), facet (204) can have approximately three times the spacing compared to when section (200) is absent. More generally, the spacing of facet (204) is generally larger than that of facet (202). Furthermore, the surface area of ​​facet (202) is generally smaller than that of facet (204). As a result, it is only necessary to manufacture relatively small-volume, closely spaced facets, while the complexity and manufacturing costs of most of the LOE structure are reduced.

[0040] Figure 4B shows the facets of sections (200) and (207) perpendicular to the main outer surface of the waveguide. Figure 4C shows an alternative implementation, referred to herein as “twisted facets,” in which the facets of both sections (200) and (207) of the waveguide are angled obliquely to the main surface of the LOE.

[0041] Figures 5A and 5B are similar to Figures 4A and 4C, but show that facets (204) and (206) can be optionally mounted in at least partially overlapping regions of the waveguide in a manner similar to the corresponding options taught in Patent Document 2. The input aperture expansion section (200) is preferably mounted to extend over most of the LOE, and preferably the entire thickness, as shown in Figure 5B.

[0042] Figure 6 shows image reflections for facets in angular space. This description concerns twisted facets, as shown in Figures 4C and 5. Light is coupled into waveguide (200) and coupled to image (6L) or (6R) as (1930A). These two images represent the forward and backward TIR reflections from the main surface of the LOE as the image illumination propagates along the aperture expansion section (200). Reflections by facet (202) are shown on (4R) and (4L) as (1938). These are images propagated by TIR along section (207). In this non-limiting but particularly preferred configuration, facet (202) is parallel to facet (204), and therefore the reflection by facet (204) in the direction of section (209) is also along (1938) from (4R) to (6L). Here, (6L) and (6R) also represent images propagating along section (209). In other words, the images propagating in sections (200) and (209) have the same angular spacing here. The reflection from facet (206) in section (209) coupling out toward the observer is represented as (1934) from the induced image (6R) to the coupled output image (8).

[0043] Circle (39) represents the TIR cutoff of the waveguide and is parallel to the waveguide plane. It is clear that images (4L) and (4R) are diagonal to the waveguide plane; that is, in angular space, the sides of the rectangular images are parallel and perpendicular to the main surface of the substrate, while images (6L) and (6R) are aligned parallel to the waveguide surface. In practice, it is generally more convenient to configure the projector (2) for parallel coupling rather than diagonal coupling. As a result, coupling in through waveguide section (200) contributes to the simplification of projector implementation and can therefore be advantageous, even if it is through a small number of high-reflectivity facets that do not necessarily significantly enlarge the effective optical aperture of the projector.

[0044] Ergonomic considerations may require image injection from the side of the waveguide, as shown in Figures 7A and 7B. In this case, the first facet (210) is favorably implemented with high reflectivity to achieve approximate uniformity between the image illumination transmitted by the first facet (210) and the image illumination reflected by subsequent facets. For example, if there are only two facets in section (200), the first facet will have 50% reflectivity and the second facet will have 100% reflectivity. However, if there are four facets, the first facet will have 75% reflectivity (25% transmittance), the second 33%, the third 50%, and the last (210) 100% reflectivity. Alternatively, facet (210) can be implemented with 100%, resulting in all transmission to section (207) coming from the subsequent facets.

[0045] The configuration shown in Figure 7A is based on coupling in from (1930B) (referring to an example of angular space in Figure 6) to facet (210) which reflects (1938) to (6L). Further propagation is as described above.

[0046] Figure 7B shows a similar configuration, where the facets in section (200) are reversed, allowing for different positions for the projector (2).

[0047] In the case of lateral injection, the first facet (210) primarily functions as a coupling in-facet and is an exception to the sequentially increasing reflectivity of facets along the order of facets, where the "order" begins with the second facet. In these cases, most of the image illumination directed toward facet (204) receives two reflections from facet (202).

[0048] Figure 8A schematically illustrates the method for integrating the waveguide into sections as shown in Figures 4A-4C. A stack (254) is formed by integrally fixing one set of covering plates (253), and slicing this (255a) generates the facet sections required for section (207). A stack (251) is formed by integrally fixing one set of covering plates (250), and slicing this diagonally generates the facet sections required for section (209), shown as (252a). A stack (257) is formed by integrally fixing a third set of covering plates (256), and slicing this generates section (258a) (the facets required for section (200)). The three sections are combined (260a) and fixed (262a). The adhesive is index-matched with the waveguide so as to minimize the perturbation introduced to the light when it passes between sections. A thin cover glass (264) is preferably fixed to both sides of the waveguide and optionally further polished to create a waveguide (266a) with a smooth and parallel TIR surface.

[0049] Figure 8B shows a similar manufacturing process suitable for the structures described in Figures 5A and 5B. Sections (252b), (255b), and (258b) are produced in the same manner as shown in Figure 8A, except that (258b) is twice as thick as the others. (252b) and (255b) are stacked, while (258b) is positioned from the side as shown in (260b). The sections are fixed integrally (262b), a clear cover glass (264) is fixed as a cover, and further polishing is optional to produce a single waveguide (266b).

[0050] If it is desirable to incorporate two overlapping sets of facets within a single layer, this integration can be carried out according to the technique described with reference to Figure 11 in the prior art document 2 mentioned above, in which case the resulting waveguide section containing the two sets of facets is attached to the side in combination with section (258b) (corresponding to the facets of section (200)), and a cover sheet is subsequently added.

[0051] While these have been shown as rectangular waveguide sections, it should be noted that the shape of the sections may change depending on the propagation of induced light. As one non-limiting example, depending on the geometric shape of image propagation, the expansion of image illumination within the waveguide may, in some cases, require spreading along the propagation path of sections (200) and (207), resulting in a waveguide configuration as illustrated in Figure 9.

[0052] While the LOE has so far been exemplified as a one-dimensionally induced integral component, the preliminary stages of aperture enlargement can optionally be carried out in various additional configurations, such as uninduced, induced on different axes, or induced in two dimensions, as illustrated here by the non-limiting examples in Figures 10A-12B.

[0053] In the non-limiting examples of Figures 10A and 10B, section (200) is implemented as a rectangular waveguide (270) that induces two-dimensional image illumination during preliminary aperture expansion, and then injects the expanded aperture image illumination into waveguide section (107). Preferably, an air gap (295), or several optical layers mimicking an air gap, is provided to maintain internal reflections within waveguide section (270) except where coupling out occurs. An example of such a 2D waveguide structure can be found in U.S. Patent No. 10,133,070, which is not described herein in detail.

[0054] Figures 11A and 11B illustrate further options, in which a coupling-in aperture expansion facet is provided without inducing image illumination by TIR. In this case, facet (202) is provided in a first section (280) that is wider than the rest of the waveguide (207). In this configuration, light in (280) is not induced and propagates through (280) while expanding in both dimensions. In this configuration, coupling to the waveguide (207) is preferably achieved via a coupling prism (285). Figure 11A shows (280) separated from (285) for clarity. The angular orientation of (280) and the coupling prism (285) facilitates uniform illumination along the thickness dimension (vertical as shown) of (207). Figure 11B shows (280) after being mounted on the coupling-in prism (285).

[0055] Figure 12A shows a further implementation variation, in which the first stage of aperture expansion is induced in a first section (290) via facet (202) in a one-dimensional manner not parallel to the waveguide (207). Figure 12B shows the placement of section (290) above the coupling prism (285), where an air gap (295) is provided to maintain TIR induction within section (290).

[0056] In all respects not expressly described herein, the arrangement of the first set of partial reflective inner surfaces (204) and the second set of partial reflective inner surfaces (206) within a common waveguide can be carried out in accordance with the options described in parallel with PCT patent application PCT / IB2019 / 157572, which was not published as of the filing date of this application and does not constitute prior art.

[0057] In all front views illustrated herein, the aperture expansion of the present invention is schematically represented by parallel arrows indicating the range of the optical aperture with respect to a predetermined ray direction corresponding to the central pixel of the optical axis of the collimated image. The optical axis is not actually in the XY plane, but rather has a Z component to a page selected such that the entire range of angles in the depth dimension of the field of view (FOV) is subject to total internal reflection at the main substrate surface. For the sake of brevity of presentation, the schematic representations and descriptions herein relate only to the in-plane (XY) components of the ray propagation direction, which are referred to herein as “in-plane components” or “components parallel to the main outer surface of the LOE.”

[0058] As described above in the context of Figure 3B, all of the above principles are also applicable to a "landscape" configuration, in which case the image is injected from a POD located laterally outside the display area and then expanded vertically by a first set of facets and then horizontally by a second set of facets for coupling to the user's eye. All of the above configurations and variations should be understood to be applicable to a side-injection configuration as well.

[0059] Throughout the above description, references to the X and Y axes are made, where the X axis is either horizontal or vertical and corresponds to the first dimension of optical aperture magnification, and the Y axis is the other principal axis corresponding to the second dimension of magnification. In this context, X and Y may be defined with respect to the orientation of the device when mounted on the user's head in an orientation typically defined by the support configuration such as the aforementioned eyeglass frames in Figures 3A and 3B.

[0060] While the present invention has been exemplified in the context of preferred but non-limiting examples of near-eye displays, it should be noted that embodiments of various aspects of the present invention may be used to benefit other applications, including but not limited to head-up displays (HUDs). One subset of HUDs of specific interest is vehicle HUDs.

[0061] The above description is intended to serve merely as an example, and it will be understood that many other embodiments are possible within the scope of the invention as defined in the appended claims.

Claims

1. An optical system for directing image illumination from an image projector towards a user so that the user can see it, wherein the optical system is (a) An image projector that projects a collimated image having a field of view angle around the optical axis, wherein the collimated image has an optical aperture of the projector, (b) A first optical conductor formed from a transparent material, the first optical conductor having a first pair of surfaces parallel to each other and a second pair of surfaces parallel to each other, the second pair of surfaces being orthogonal to the first pair of surfaces, the image projector being coupled to the first optical conductor, introducing the collimated image from the optical aperture of the projector into the first optical conductor, the first optical conductor propagating by internal reflection in two dimensions through the first pair and the second pair of surfaces, (c) Includes a light guide optical element (LOE) formed from a transparent material, the LOE is (i) A set of mutually parallel main external surfaces, the main external surfaces extending across a first region and a second region, (ii) A first set of planar, mutually parallel partial reflective surfaces located between the main outer surfaces in the first region of the LOE and having a first orientation that is not parallel to the main outer surfaces, (iii) a second set of planar, mutually parallel partial reflective surfaces located between the main outer surfaces in the second region of the LOE and having a second orientation that is oblique to the main outer surfaces, The first optical conductor includes a third set of mutually parallel internal partial reflective surfaces, which are arranged to deflect and introduce the collimated image propagating within the first optical conductor into the LOE, and propagate within the LOE toward a first set of partial reflective surfaces by internal reflection at the main external surface, The first set of partial reflective surfaces is configured to deflect the collimated image propagating within the LOE, so that it propagates within the LOE toward the second set of partial reflective surfaces by internal reflection at the main outer surface. An optical system in which a second set of the partial reflective surfaces is configured to deflect and propagate the collimated image, separating it from the LOE and making it visible to the user.

2. The optical system according to claim 1, wherein the first pair of mutually parallel surfaces of the first optical conductor are parallel to the main outer surface of the LOE.

3. The optical system according to claim 1, wherein the mutually parallel surfaces of the first pair and the second pair of the first optical conductor are both not parallel to the main outer surface of the LOE, and the collimated image deflected by the third set of partial reflective surfaces passes through a coupling prism before entering the LOE.

4. The optical system according to claim 1, wherein the collimated image, deflected by the third set of partially reflective surfaces, passes through an air gap before entering the LOE.

5. The optical system according to claim 1, wherein the collimated image, deflected by the third set of partially reflective surfaces, passes through an optical layer that mimics an air gap before entering the LOE.

6. The optical system according to claim 1, wherein a third set of partially reflective surfaces has a first sequence of reflectances that increase continuously in the order in which the image illumination reaches, and the first set of partially reflective surfaces has a second sequence of reflectances that increase continuously in the order in which the image illumination reaches, the second sequence beginning with a reflectance smaller than the last reflectance of the first sequence.

7. The optical system according to claim 6, wherein the final reflectance of the first sequence of continuously increasing reflectances is greater than 90%.

8. The optical system according to claim 1, wherein the first region and the second region do not overlap.

9. The optical system according to claim 1, wherein the image projector is coupled to the first optical conductor, and thus introduces the collimated image from the optical aperture of the projector into the first optical conductor, so that the rays of the collimated image are not parallel to the first pair or second pair of surfaces or the third set of partial reflective surfaces, the collimated image propagates within the LOE, and the rays of the collimated image are not parallel to the main outer surface or the first set of partial reflective surfaces.

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