Light guide optical assembly

Abstract

To provide an optical assembly for optical aperture expansion.SOLUTION: The optical assembly combines a facet reflective technique with a diffractive technique. At least two diffractive components having opposite optical power (matching) are used, so that chromatic dispersion introduced by the first diffractive component will then be cancelled by the second diffractive component. The two diffractive components are used in combination with a reflective optical component to achieve more efficient aperture expansion (for near eye display), thereby reducing distortions and noise, while also reducing design constraints on the system and individual components, as compared to conventional techniques. The assembly eliminates and / or reduces the need for polarization management, while enabling a wider field of view. In addition, embodiments can have reduced nonuniformity, as compared to conventional single technique implementations, since distortion patterns of the two techniques do not correlate.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention generally relates to optical assemblies and, in particular, to the expansion of optical apertures.

Background Art

[0002] Referring to A of FIG. 7, a rough schematic diagram of a conventional optical aperture expansion using a diffractive component in a waveguide is shown. In the current figure, the incident light (image) is perpendicular from outside the page to the page. The coupling-in element (1001) couples the incident light to the lateral expansion element (1002), and the lateral expansion element (1002) expands the light laterally (from left to right in the current figure). Thereafter, the laterally expanded light is coupled to the vertical expansion element (1003), and the vertical expansion element (1003) expands the light vertically (from top to bottom in the current figure) and couples that light out to the user (viewer's eye).

[0003] Conventional diffractive elements introduce chromatic dispersion in which light rays with various wavelengths diffract at various angles. A narrowband light source (such as a laser) can be used to reduce chromatic dispersion. A more practical solution is to design diffractive components to cancel each other's dispersion.

[0004] Referring to B of FIG. 7, a diagram of the diffraction direction of FIG. 7A of light propagating in an angular region (angular interval) is shown. The dashed arrows and solid arrows indicate two different typical wavelengths. The starting angle of region (1005) represents the angle of the light ray when the light ray hits the first diffractive element (coupling-in element (1001)) to which the light ray is coupled to the optical waveguide. Region (1007) represents the direction of the light ray after the coupling-in element (1001), region (1009) represents the direction of the light ray after the lateral expansion element (1002), and region (1005) further represents the angle of the light ray after coupling from the optical waveguide by the vertical expansion element (1003). The direction of the light ray entering the optical waveguide is equal to the direction of the light ray coupled from the optical waveguide in order to minimize chromatic dispersion. When light rays with various wavelengths propagate within the optical waveguide, the various wavelengths have different directions and have the same direction when output from the optical waveguide.

[0005] Basic technology Figure 1 illustrates a conventional prior art foldable optical structure, where the substrate (2) is irradiated by a display source (4). The display is collimated by a collimating optical system (6) (e.g., a lens). The light from the display source (4) is coupled to the substrate (2) by a first reflecting surface (8) such that the main ray (11) is parallel to the substrate plane. A second reflecting surface (12) couples the light from the substrate to the viewer's eye (14). Despite the compactness of this structure, it suffers from significant drawbacks. In particular, it can only achieve a very limited FOV.

[0006] Here, referring to Figure 2, a side view of a typical light guiding optical element (LOE) is shown. To alleviate the above limitations, an array of selective reflecting surfaces can be used and fabricated within the light guiding optical element (LOE). The first reflecting surface (16) is irradiated by a collimated display ray (beam) (18) emitted from a light source (not shown) positioned behind the device. For the sake of brevity of the drawing, only one ray, i.e., the incident ray (38) (also referred to as the "beam" or "incident ray") is generally depicted. Other rays of incident light such as beams (18A) and (18B) may be used to specify the edges of the entrance pupil such as the left and right edges of the entrance pupil. In general, whenever an image is represented herein by rays, the rays are sample beams of the image, which are typically formed by a plurality of beams at slightly different angles each corresponding to a point or pixel of the image. It should be noted that except in the case especially called the tip of the image, the illustrated beam is typically the centroid of the image.

[0007] The reflecting surface (16) reflects the incident light from the light source, and the incident light is trapped inside the optical waveguide (20) by total internal reflection. The optical waveguide (20) is also referred to as a "waveguide", a "planar substrate", and an "optical transmission substrate". The optical waveguide (20) includes at least two (main) surfaces that are parallel to each other and are shown in the drawing as the rear (main) surface (26) and the front (main) surface (26A). Note that the designations "front" and "rear" with respect to the main surfaces (26) and (26A) are for reference convenience because the optical waveguide (20) is usually symmetric (thus, the same result can be obtained by substituting the references to the main surfaces (26), (26A)). The optical waveguide (20) is referred to as a one-dimensional (1D) waveguide in the context of this specification and guides an image injected in only one dimension between a pair of parallel surfaces (in this case, the main surfaces (26), (26A)).

[0008] The incident light ray (38) enters the substrate at the proximal end of the substrate (the right side of the figure). The light propagates through the optical waveguide towards the distal end of the optical waveguide (the left side of the figure) through the optical waveguide and one or more facets, usually at least a plurality of facets, and typically several facets. The light propagates through the optical waveguide in both the initial propagation direction (28) of propagation and a different propagation direction (30).

[0009] After several reflections from the surface of the substrate (20), the trapped wave reaches the array of selective reflecting surfaces (22), which couples the light from the substrate to the viewer's eye (24). In an alternative structure, the selective reflecting surface (22) enters the substrate without first reflecting from the surface of the substrate (20) immediately after the light ray (18).

[0010] Internal partial reflectors, such as the selective reflector surface (22), are generally referred to as "facets" in the context of this specification. In the extreme, a facet can be fully reflective (100% reflectivity or a mirror, e.g., the last facet at the distal end of the substrate), or minimally reflective. For practical use enhancement, the facet is partially reflective, allowing light from the real world to enter through the upper surface (26A), cross the substrate containing the facet, and exit the substrate through the lower surface (26) to reach the viewer's eye (24). For virtual reality applications, the facet may have an alternative reflectivity, such as a first internally connected mirror with 100% reflectivity, since image light from the real world does not need to cross this mirror. The internal partial reflector surface (22) generally crosses at least partially the light guide (20) at an oblique angle (i.e., neither parallel nor perpendicular) to the direction of elongation of the light guide (20).

[0011] References to reflectivity generally relate to nominal reflectivity. Nominal reflectivity is the total reflectivity required at a specific location in the substrate. For example, when the reflectivity of a facet is mentioned as 50%, this generally refers to 50% of the nominal reflectivity. If the nominal reflectivity is 10%, a 50% reflectivity results in a 5% facet reflectivity. One of ordinary skill in the art will understand the use of the percentage of reflectivity from the context of use. Partial reflection can be implemented by various techniques including, but not limited to, the transmission of a certain percentage of light or the use of polarization.

[0012] A and B in FIG. 3 illustrate the desired reflectivity behavior of the selective reflector surface. In FIG. 3A, the light ray (32) is partially reflected from the facet (34) and coupled out from the substrate (20) (38B). In FIG. 3B, the light ray (36) is transmitted through the facet (34) without significant reflection.

[0013] A in FIG. 4 is a detailed cross-sectional view of an array of selective reflective surfaces that couples light to a substrate and then couples the light to the viewer's eye. As shown in the figure, a light ray (38) from a light source (4) strikes a first partial reflective surface. A portion of the light ray (41) continues in its original direction and is coupled from the substrate. Another portion of the light ray (42) is coupled to the substrate by total internal reflection. The captured light ray is gradually externally coupled from the substrate by two other partial reflective surfaces (22) at point (44). The coating characteristics of the first reflective surface (16) do not necessarily have to be similar to the coating characteristics of the other reflective surfaces (22), (46). This coating can be a simpler beam splitter that is metallic, dichroic, or a hybrid metal-dichroic. Similarly, in the case of a non-see-through system, the last reflective surface (46) can be a simple mirror.

[0014] B in FIG. 4 is a detailed cross-sectional view of an apparatus including an array of reflective surfaces, where the last reflective surface (46) is a total reflection mirror. The leftmost portion of the last reflective surface (46) cannot be optically active in such a case, and peripheral light rays (48) cannot be coupled from the substrate. Thus, the output aperture of the device is slightly smaller. However, the optical efficiency can be much higher, and the manufacturing process of the LOE can be much simpler.

[0015] Unlike the structure shown in FIG. 2, it is important to note that there are constraints on the orientations of the reflecting surfaces (16) and (22). In the previous structure, all light is coupled inside the substrate by the reflecting surface (16). Thus, the surface (16) need not be parallel to the surface (22). Further, the reflecting surface may be oriented such that light is coupled out of the substrate in a direction exactly opposite to the direction of the input wave. For the structure illustrated at A in FIG. 4, however, a portion of the input light is not reflected by the surface (16) but continues in the original direction of the input light (38) and is immediately coupled out of the substrate as output light (41). Thus, not only must all of the reflecting surfaces (22) be parallel to each other so that all rays of light starting from the same plane wave will surely have the same output direction, but the surface (16) must likewise be parallel to the surface (22).

[0016] Referring again to A in FIG. 4, a system having two reflecting surfaces for coupling light out of the substrate is shown, although any number of reflecting surfaces can be used depending on the required output aperture of the optical system and the thickness of the substrate. Naturally, there may be cases where only one coupling-out surface is required. In that case, the output aperture will be effectively twice the size of the input aperture of the system. Only the reflecting surfaces required for the final structure are simple beam splitters and mirrors.

[0017] In the apparatus described in this figure, light from the display source is coupled into the substrate at the edge of the substrate, but there are systems that preferably have a symmetric system. That is, the input light should be coupled into the substrate at the center of the substrate.

[0018] C in FIG. 4 is a diagram illustrating a detailed cross-sectional view of a one-dimensional (1D) optical guide for lateral pupil dilation having a symmetric structure. This figure illustrates a method of combining two identical substrates to produce a symmetric optical module. As can be seen, a portion of the light from the display source (4) passes directly through the partial reflector and exits the substrate. The other portion of the light is coupled to the right side (20R) and the left side (20L) of the substrate by the partial reflectors (16R) and (16L), respectively. The captured light is then gradually externally coupled by the reflectors (22R) and (22L), respectively. Clearly, the output aperture is three times the size of the input aperture of the system and is at the same magnification as described in B of FIG. 5. However, unlike the previous system, the system here is symmetric about the joint surface (29) of the right and left substrates.

[0019] Referring now to FIGS. 5A and 5B, in addition to the optical guide, typical implementations of B and C of FIG. 4 are shown. The configurations of B and C of FIG. 4 are horizontal magnifications of the incident image. The apparatus of B of FIG. 4 is used to implement the first LOE (20a) of FIG. 5A, the apparatus of C of FIG. 4 is used to implement the first LOE (20a') of FIG. 5B, and the apparatus of FIG. 2 can be used to implement the second LOE (20b).

[0020] In FIG. 5A, an alternative method for expanding a beam along two axes utilizing a dual LOE configuration is illustrated. The input wave (90) is coupled to a first LOE (20a) having an asymmetric structure similar to the structure illustrated in FIG. 4B by a first reflecting surface (16a), and then propagates along the η axis. The partial reflecting surface (22a) couples to the light emerging from the first LOE (20a), and then the light is coupled by a reflecting surface (16b) to a second asymmetric LOE (20b). Thereafter, the light propagates along the ξ axis and is then externally coupled by a selective reflecting surface (22b). As shown, the original beam (90) is expanded along both axes, where the overall expansion is determined by the ratio between the lateral dimensions of elements (16a) and (22b). The configuration given in FIG. 5A is merely an example of a dual LOE setup. Also, other configurations are possible where two or more LOEs are combined together to form a complex optical system.

[0021] Referring now to FIG. 5B, a diagram is shown that illustrates another method for expanding a beam along two axes utilizing a dual LOE configuration. Typically, the region where light is coupled by a surface (16b) to a second LOE (20b) cannot be made transmissive to external light and is not part of the see-through region. Thus, the first LOE (20a) need not be transmissive. As a result, it is usually possible to design the first LOE (20a) to have a symmetric structure as can be seen in this figure even with respect to a see-through system. The second LOE (20b) has an asymmetric structure that allows the user to view the external situation. In this configuration, a part of the input beam (90) continues to the internal coupling mirror (16b) of the second LOE (20b) along the original direction (92), while another part (94) is coupled by a reflecting surface (16a) to a first LOE (20a') and propagates along the η axis and is then coupled by a selective reflecting surface (22a) to the second LOE (20b). Thereafter, both parts are coupled by a reflecting surface (16b) to a second asymmetric LOE (20b), propagate along the ξ axis, and are then coupled by a selective reflecting surface (22b).

[0022] Figure 6 illustrates an example of the LOE(20a) / (20a’) and (20b) embedded in a standard eyeglass frame (107). The display source (4), the folding optical system and the collimating optical system (6) are assembled inside the arm portion (112) of the eyeglass frame directly beside the LOE(20a) / (20a’), which is located at the edge of the second LOE(20b). When the display source is an electronic element such as a small CRT, LCD, or OLED, the driving electronics (114) for the display source can be assembled inside the rear portion of the arm (112). The power supply and data interface (116) can be connected to the arm (112) by leads (118), or other communication means including wireless or optical transmission. Alternatively, the battery and small data link electronics can be integrated in the eyeglass frame. This figure is an example, and other possible configurations of head-mounted displays including assemblies where the display source is attached parallel to the LOE plane or above the LOE can also be constructed.

[0023] Additional details of this underlying technology can be found in U.S. Patent No. 7,643,214, and PCT / IL2018 / 050025, which is not published and does not constitute prior art for the present invention.

SUMMARY OF THE INVENTION

[0024] According to the teachings of this embodiment, an apparatus for expanding an optical aperture is provided, the apparatus including at least one optical waveguide; a set of three optical components associated with the at least one optical waveguide, the set of three optical components including a pair of first and second matching diffractive optical components; and a reflective optical component including an array of mutually parallel surfaces that partially reflect light; and cooperating optical components for expanding internally connected light to externally connected light, the internally connected light being coupled to the at least one optical waveguide, and the expansion being two-dimensional.

[0025] In an optional embodiment, the first optical component of the set is configured to direct light that is internally coupled in a first direction of expansion within a first optical waveguide, thereby generating a first expanded light; the second optical component of the set is configured to couple the first expanded light to a second optical waveguide in a second direction of expansion, thereby generating a second expanded light; and the third optical component of the set is configured to externally couple the second expanded light as externally coupled light in a third direction; wherein the first, second, and third directions are not parallel to each other.

[0026] Another optional embodiment further includes a diffractive optical component configured to direct light as internally coupled light to at least one optical waveguide; wherein the at least one optical waveguide is one optical waveguide, and the one optical waveguide is a first diffractive optical component configured to direct light that is internally coupled in a first direction of expansion within the one optical waveguide, thereby generating a first expanded light; a second diffractive optical component configured to expand the first expanded light in the one optical waveguide in a second direction of expansion, thereby generating a second expanded light; and a reflective optical component configured to externally couple the second expanded light as externally coupled light in a third direction; wherein the first, second, and third directions are not parallel to each other.

[0027] Another optional embodiment further includes a pair of third and fourth matching diffractive optical components; and a pair of fifth and sixth matching diffractive optical components.

[0028] In another optional embodiment, each of the matching pairs of optical components has a different diffraction spacing from the other matching pairs of optical components, and the diffraction spacing is such that each of the matching pairs of optical components deflects different wavelengths at a similar angle from the other matching pairs of optical components.

[0029] In another optional embodiment, the wavelengths are red, green, and blue light.

[0030] In another optional embodiment, the first optical waveguide of the at least one optical waveguide includes a pair of first and second matching diffractive optical components; the second optical waveguide of the at least one optical waveguide includes a pair of third and fourth matching diffractive optical components; and the third optical waveguide of the at least one optical waveguide includes a pair of fifth and sixth matching diffractive optical components.

[0031] In another optional embodiment, the reflective optical component is configured to expand the light internally connected in a first direction of expansion within the first optical waveguide, thereby generating first expanded light; the first, third, and fourth diffractive optical components are configured to expand the respective wavelengths of the first expanded light in the respective first, second, and third optical waveguides in a second direction of expansion, thereby generating respective second expanded light; and the second, fourth, and sixth diffractive optical components are configured to externally connect the respective second expanded light as externally connected light in a third direction; wherein the first, second, and third directions are not parallel to each other.

Brief Description of the Drawings

[0032] This embodiment is described herein by way of example only with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

[0033] Abbreviations and Definitions For convenience of reference, this section contains a concise list of abbreviations, acronyms, and short definitions used in this specification. This section should not be considered as limiting the present invention. More complete explanations may be found hereinafter and in the applicable standards. 1D - One-dimensional 2D - Two-dimensional CRT - Cathode Ray Tube EMB - Eye Motion Box FOV - Field of View HMD - Head-Mounted Display HUD - Head-Up Display LCD - Liquid Crystal Display LOE - Light Guide Optical Element OLED - Organic Light-Emitting Diode Array OPL - Optical Path Length SLM - Spatial Light Modulator TIR - Total Internal Reflection

Best Mode for Carrying Out the Invention

[0034] Detailed Description - From A of FIG. 8 to D of FIG. 15 The principles and operation of the apparatus described in this embodiment may also be fully understood with reference to the drawings and the accompanying description. The present invention is an optical assembly for optical aperture expansion. By that apparatus, a diffraction technique (diffraction component) and a facet reflection technique (reflection component) are combined. An innovative embodiment using a diffraction component uses at least two components having opposite optical powers (coincidence), so that the wavelength dispersion caused by the first diffraction component is then canceled by the second diffraction component. The two diffraction components are used in combination with a reflective optical component (for a near-eye display), thereby achieving a more effective aperture expansion, reducing distortion and noise, while reducing design constraints in the system and individual components as compared with the prior art.

[0035] Current, conventional optical aperture expansion uses a single technique for both (lateral and vertical) expansions. Current progress in this field is to optimize and improve any one of these techniques. The two main techniques used are as follows: 1) Reflection by tilted coated facets (e.g., U.S. Patent No. 7,457,040 to Lumus, Ltd.). This reflection technique has a broad spectrum and can thus project all visible spectra from a single light guide. By this facet, typically both partial reflection and transmission of the propagating light rays are performed, but for brevity in this specification, this technique is generally referred to as being implemented by a "reflective optical component". This reflection is typically polarization-dependent. 2) Diffraction pattern on the light guide surface. As is known in the art, a diffraction grating (pattern) reflects or transmits the propagating light rays depending on the structure of the diffraction grating. For brevity in this specification, this technique is generally referred to as being implemented by a "diffractive optical component". This diffraction technique is limited in both spectrum and angle. However, the polarization dependence of this technique is low.

[0036] By using arrays of reflective and diffractive components in various quantities and orders (alternately and vice versa), the need for polarization management is eliminated and / or reduced, while a wider field of view becomes possible. Additionally, since the distortion patterns of the two technologies are uncorrelated (non-correlated), embodiments were able to reduce non-uniformity compared to the implementation of conventional single technologies.

[0037] Generally, an apparatus for optical aperture expansion includes at least one optical waveguide and a set of three optical components associated with the at least one optical waveguide. The set of three optical components includes a pair of matching diffractive optical components and a reflective optical component. The reflective optical component includes an array of a plurality of at least partially reflective surfaces that are parallel to each other. Those optical components are configured to cooperate to achieve a two-dimensional expansion of the externally coupled light. In other words, those components cooperate to expand the internally coupled light to externally coupled light. The internally coupled light is the light coupled to at least one optical waveguide, and the expansion is two-dimensional.

[0038] In the context of this description, the term "matching" with respect to diffractive optical components generally refers to gratings and / or spacings of substantially exactly equivalent grating elements, and thus the optical powers of the diffractive components are equivalent and usually opposite. The overall physical dimensions of the components may be different, but similar gratings result in matching optical powers of the components.

[0039] In the context of this description, the term "component" is used for optical elements, particularly reflective and diffractive optical elements. Design and production techniques for reflective components and optical components are known in the art. Based on this description, components can be implemented as required in various shapes and sizes of reflective and diffractive optical components, and various operating parameters include wavelength, power, and angle.

[0040] In the context of this description, diffractive optical components, also referred to as "diffraction gratings" and "diffraction patterns", can be embedded in the optical waveguide, or formed or attached on the surface (face) of the optical waveguide. For example, the diffractive optical component can be implemented as a diffraction grating or a holographic element. Diffractive components are available from Horiba Scientific (Kyoto, Japan), etc., and reflective components are available such as the OE50 of Lumus (Ness Ziona, Israel).

[0041] Referring now to A and B of FIG. 8, there are shown rough schematic side and front views, respectively, of a typical diffractive-reflective-diffractive embodiment. Different combinations of optical components expand light along different axes. The optical waveguide (10) is a two-dimensional (2D) optical waveguide having an elongation direction that is arbitrarily illustrated herein as corresponding to the "X-axis". The waveguide (10) is referred to as a 2D waveguide in the sense that, as shown in FIG. 8A by the four arrows inside the waveguide (10), the waveguide (10) guides the injected image two-dimensionally by reflection between two sets of parallel planes. The arrangement of a plurality of internal partial reflective surfaces (40) at least partially traverses the waveguide (10) at an angle (i.e., neither parallel nor perpendicular) to the elongation direction.

[0042] The incident light (38) is coupled to the optical waveguide (10) by the diffraction component (5). The internally coupled light enters the optical waveguide (10) which acts as a first lateral optical waveguide expander in a first direction. The expanded light (38C) is coupled from the optical waveguide (10) to the optical waveguide (2000). The optical waveguide (2000) guides light mainly along the "Y-axis". The expanded light (38C) continues to be reflected within the optical waveguide (2000) expanding in a second expansion direction (Y-axis) as indicated by the arrow in the side view of A in FIG. 8. The light in the optical waveguide (2000) is referred to herein as the second expanded light (38D) in this context. When the second expanded light (38D) encounters the diffraction pattern (25), it is externally coupled out of the optical waveguide (2000) to the observer (47) (38B). A feature of this embodiment is that the diffraction components are not parallel to each other.

[0043] Typically, a set of three optical components is configured to direct the light (38) internally coupled in a first expansion direction (X-axis) within the first optical waveguide (optical waveguide (10)), thereby generating the first expanded light (38C), and includes a first optical component (diffraction component (5)). The second optical component of the set (array of partial reflection surfaces (40)) is configured to couple the first expanded light (38C) to the second optical waveguide (2000) in a second expansion direction (Y-axis), thereby generating the second expanded light (38D). The third optical component of the set (diffraction component (25)) is configured to externally couple the second expanded light (38D) in a third direction as the externally coupled light (38B).

[0044] In the context of this description, the term "direction" typically refers to the average direction of propagation within an optical waveguide, usually along the optical axis (usually the length) of the optical waveguide. In other words, the course or normal path along which light trapped in an optical waveguide slab by total internal reflection (TIR) travels along the optical waveguide slab, i.e., the course of expansion in the plane of the optical waveguide slab (the in-plane component of the light rays propagating in the substrate of the optical waveguide).

[0045] The first, second, and third directions are not parallel to each other.

[0046] Referring now to D of FIG. 8, there is shown a diagram of the diffraction directions of light propagating in the angular regions (angular intervals) in A and B of FIG. 8. The dotted and solid lines indicate two different exemplary wavelengths. The direction region (1005) is the angle of incidence as described with respect to B of FIG. 7. Region (1007) represents the direction of the light ray (or simply "ray") after lateral expansion and reflection by the array of partial reflecting surfaces (40). The partial reflecting surface (40) redirects the direction of the light ray into region (1011). However, the reflection from this region (1007) to region (1011) does not introduce additional dispersion and only reflects the direction of propagation around the mirror direction (shown as the dashed line (1008)). The mirror direction (1008) is determined by the inclination of the partial reflecting surface (40). The last diffraction element (25) diffracts the light ray into region (1013). When the light ray is diffracted into the diffraction component (5) in a compensatory manner, the output direction (1013) then does not disperse, but it is not necessary to duplicate (1005). In this embodiment, dispersion is eliminated, but the output angle of the externally coupled light (38B) may not coincide with the input angle of the internally coupled light (38).

[0047] Referring now to C of FIG. 8, there is shown a rough schematic diagram of a typical embodiment of reflection-diffraction. This figure is similar to A and B of FIG. 8, except that the incident light (38) is coupled to the optical guide (10) by an inclined prism (7) (instead of the diffraction component (5)). Since this embodiment includes only one diffraction element (diffraction element (25)), chromatic dispersion is significant compared to the embodiments of A and B of FIG. 8 which include two matching diffraction elements ((5) and (25)). The chromatic dispersion (aberration) can be reduced by using a narrow-band light source.

[0048] Referring now to A and B of FIG. 9, a side view and a front view of a rough schematic diagram of a typical embodiment of diffraction-diffraction-reflection are shown respectively. The optical waveguide (2010) is a 2D optical waveguide. In this embodiment, the first optical component of the set is implemented by a diffraction component (5A) configured to direct light (38) interconnected in the first expansion direction (X-axis) within the optical waveguide (2010), thereby generating a first expanded light (38C). The second optical component of the set is implemented by a diffraction component (370) configured to connect the first expanded light (38C) to the optical waveguide (20) in the second expansion direction (Y-axis), thereby generating a second expanded light (38D). The third optical component of the set is implemented by an array of a plurality of partial reflection surfaces (facets) (45) configured to externally connect the second expanded light (38D) in a third direction as externally connected light (38B), preferably at an oblique angle to the surface of the optical waveguide (20) and at least partially traversing the optical waveguide (20).

[0049] Referring now to C of FIG. 9, a diagram of the diffraction direction of light propagating in the angular region (angular interval) in A and B of FIG. 9 is shown. The angular vectors are also shown, (1005) is the incident direction, and the direction after the first element (5A) is (1007). The diffraction element (370) has opposing optical powers, and thus, light is coupled from the optical waveguide (2010) to the optical waveguide (20) having the same direction but no chromatic dispersion (overlap (1005)). The facet (45) reflects light without dispersion in a preferred direction (1013) without chromatic dispersion. Some chromatic dispersion can be introduced by the reflection component, and the remaining diffraction can compensate for this.

[0050] Referring now to A and B of FIG. 10, there are shown rough schematic views of a side view and a front view, respectively, of a typical embodiment of diffraction - reflection. The optical waveguide (2011) is a 2D optical waveguide. Lateral expansion is performed by a diffraction component, while vertical expansion is performed by a reflective facet. The method of connecting to the optical waveguide (2011) is not represented. Light propagates within the optical waveguide (2011), strikes the diffraction surface (component) (35), and is diffracted towards the optical waveguide (20). The diffraction component (35) can be on any surface of the optical waveguide (2011) (represented at the top, in this figure). When the light propagates within the optical waveguide (20), it is externally coupled (38B) towards the eye (47) by the facet (45). This configuration does not require polarization management between the optical waveguide (2011) and the optical waveguide (20). The injected polarization of the light can be oriented to match that required by the facet (45).

[0051] Referring now to A and B of FIG. 11, there are shown rough schematic views of a side view and a front view, respectively, of a typical embodiment of diffraction - diffraction - reflection. The non - diffraction optical component (501) is configured to direct light, shown as light (38), as internally - coupled light, towards the optical waveguide (2002). In this embodiment, a single optical waveguide (2002) is used, and two diffraction components are implemented as parts of the optical waveguide (2002). The first diffraction optical component (502) is configured to direct the light (38) internally - coupled in a first expansion direction (X - axis) within one optical waveguide (2002), thereby generating a first expanded light (38C). The second diffraction optical component (50) is configured to expand the first expanded light (38C) in a second optical waveguide (2002) in a second expansion direction (Y - axis), thereby generating a second expanded light (38D). The reflective optical component (an array of multiple facets (45)) is configured to externally - couple the second expanded light (38D) in a third direction as externally - coupled light (38B). As in the above - mentioned embodiment, the first, second, and third directions are not parallel to each other.

[0052] The feature of this embodiment is the use of a single one-dimensional optical waveguide. The connection to the optical waveguide is by a non-diffracting component (501), and the light is converted by a strong diffraction pattern (502). The light is guided one-dimensionally and thus propagates from left to right along the diffracting component (50) while expanding in another dimension. When the light encounters the diffraction pattern (50), the light is also converted downward. While propagating downward, the light is reflected toward the observer (47) by a reflecting facet (45) (represented in a side view of A in FIG. 11). This configuration includes a single optical waveguide and does not require polarization management (the polarization of the light injected into the optical waveguide may be appropriate for the reflecting facet (45)). The combination of the diffraction pattern (502) and the diffraction pattern (50) does not result in chromatic dispersion.

[0053] Referring now to C of FIG. 11, a rough schematic front view of a typical embodiment of overlapping diffraction-reflection-diffraction is shown. By different techniques, the diffracting and reflecting elements can be positioned overlapping each other on the same optical waveguide. In this figure, the diffraction grating component (1110) expands the light (38) internally connected in a first direction to create a first expanded light (38C). The expansion of the lateral opening is implemented by overlapping the slanted facets (1114) that connect the light laterally before and after, and expanding the light in a second direction (38D) without introducing chromatic aberration. The diffraction pattern (1112) is used to couple light from the waveguide.

[0054] Referring now to FIGS. 12A and 12B, there are shown rough schematic side and front views, respectively, of an exemplary embodiment of diffraction-reflection. The lateral magnification is based on a one-dimensional optical waveguide (2012) (see, e.g., U.S. Patent No. 7,643,214 to Lumus Ltd.). In FIG. 12B, the connection to the optical waveguide (2012) is made by a highly reflective (i.e., partially reflective and reflecting most of the energy) internal facet (65), which reflects most of the internally coupled light (38) to the left and right sides of the optical waveguide (2012), while a portion of the internally coupled light (38) passes through the internal facet (65) and reaches the optical waveguide (20). When this embodiment includes only one diffraction element, chromatic dispersion becomes important as compared to the embodiment of FIG. 12C below. Chromatic dispersion (aberration) can be reduced by using a narrow-band light source.

[0055] Referring now to FIG. 12C, there is shown a rough schematic front view of an exemplary embodiment of diffraction-diffraction-reflection. In this embodiment, the connection to the optical waveguide (2013) is made by a diffraction component (66) having high performance, which reflects most of the internally coupled light (38) to the left and right sides of the optical waveguide (2013), while a portion of the internally coupled light (38) passes through the diffraction component (66) and reaches the optical waveguide (20).

[0056] Similar to the description of FIG. 9B, the first expanded light (38C) is diffracted by a diffraction component (67) in FIG. 12B and by a diffraction component (68) in FIG. 12C to generate a second expanded light (38D) in the optical waveguide (20).

[0057] As can be seen from the exemplary embodiments, the diffraction component can generally be disposed on any side of the optical waveguide. As in the previous embodiments, with appropriate polarization injection, no further management is required for the device.

[0058] The wavelengths of different lights are deflected by diffraction patterns in different directions. This phenomenon can be used, for example, by a near-eye display by implementing individual light guides for each wavelength. Exemplary embodiments are three light guides, each for a wavelength corresponding to red (R), green (G), and blue (B) colored light. Individual diffractive lateral aperture expanders (one for each color) are coupled to a single vertical reflective aperture expander.

[0059] Referring now to FIGS. 13A and 13B, there are shown schematic diagrams generally of a side view and a front view, respectively, of an exemplary diffractive - diffractive - reflective embodiment with individual diffractive lateral expanders. This embodiment is based on the embodiment described above with respect to FIGS. 9A and 9B. The optical waveguide (2010) of FIG. 9B is replaced with a set of optical waveguides (103), (102), and (101). Each set of optical waveguides has a first diffractive component (respectively (133R), (133G), (133B)) configured for a specific wavelength in the red, green, and blue of this example. Each set of optical waveguides has a second diffractive component (respectively (134R), (134G), (134B)) that coincides with the first diffractive component. The internally coupled light (38) is injected through the first diffractive components. Each of these first diffractive components is wavelength specific, diffracting a specific associated wavelength of light and passing other wavelengths of light. The specific diffraction of each wavelength of light into each optical waveguide can be improved by adding a set of dichroic reflectors (respectively (133R1), (133G1), (133B1)) after each of the first diffractive components (133R), (133G), (133B). The dichroic reflectors can be based on coating reflectors or diffractive reflectors, and thus different wavelengths are coupled to different respective optical waveguides (103), (102), and (101). The wavelengths of the light diffracted by the first diffractive components (133R), (133G), (133B) propagate laterally and expand as respective first expanded lights (38CR), (38CG), (38CB) in respective optical waveguides (103), (102), and (101). Each optical waveguide (103), (102), (101) has a respective second diffractive component (134R), (134G), (134B) that diffracts the respective first expanded lights (38CR), (38CG), (38CB) towards the optical waveguide (20).Since the second diffraction components (134G), (134B) are wavelength selective or have low diffraction efficiency for other wavelengths, the light from the upper optical guide passes through the lower optical guide with the least distortion. In the optical guide (20), the arrangement of the plurality of partial reflection surfaces (45) reflects all wavelengths towards the eye (47).

[0060] As an alternative description of this embodiment, a pair of first (133R) and second (134R) matching diffractive optical components are increased by 1) a pair of third (133G) and fourth (134G) matching diffractive optical components, and 2) a pair of fifth (133B) and sixth (134B) matching diffractive optical components. The diffraction interval of each of the matching pairs of optical components is different from that of the other matching pairs of optical components. The diffraction interval is such that each of the matching pairs of optical components deflects different wavelengths at similar angles from the other matching pairs of optical components. The first optical guide (103) includes a pair of first (133R) and second (134R) matching diffractive optical components. The second optical guide (103) includes a pair of fourth (133G) and fourth (134G) matching diffractive optical components. The third optical guide (103) includes a pair of fifth (133B) and sixth (134B) matching diffractive optical components.

[0061] In this configuration, one optical guide may be in front of the eye (47), and the polarization between the optical guides (103), (102), (101), and (20) cannot be arbitrarily managed. In this configuration, the optical guides can be placed directly on top of each other (typically, a gap is used between the optical guides to maintain TIR).

[0062] Referring now to FIGS. 14A and 14B, there are shown rough schematic side and front views, respectively, of an exemplary embodiment of diffraction - reflection. This embodiment is similar to the operations described with respect to FIGS. 12A and 12B, where the optical guide (2012) is replaced / enlarged (replaced with three optical guides (160R), (160G), and (160B)). The internal connection of the light (38) to each of the optical guides (160R), (160G), (160B) is by respective highly - reflective internal facets / central splitting mirrors (165R), (165G), (165B). The lateral (sideways) expansion is diffractive in each of the optical guides (160R), (160G), (160B), and then the first expanded light (38C) is diffracted / converted into the optical guide (20) for external connection to the user's eye (47).

[0063] Referring now to FIG. 14C, there is shown a rough schematic front view of an exemplary embodiment of diffraction - diffraction - reflection. This embodiment is similar to the operations described with respect to FIG. 12C, where the diffraction component (66) is replaced / enlarged by a set of diffraction components (133R), (133G), (133B), and dichroic reflectors (each of (133R1), (133G1), (133B1)) are associated after each of the first diffraction components (133R), (133G), (133B) at the center of their respective optical guides (159R), (159G), (159B). The matching diffraction elements (134R), (134G), (134B) are replaced by a plurality of diffraction elements (134R1), (134R2), (134G1), (134G2), (134B1), (134B2) on either side of any one of the central diffraction components (133R), (133G), (133B).

[0064] Referring now to FIGS. 15A, 15B, and 15C, there are shown rough schematic side, front, and top views, respectively, of an exemplary embodiment of diffraction - reflection - reflection. In this embodiment, the reflective aperture expander is in front of the diffraction expander. Four optical guides are used, which are a reflective component (201) and three diffraction components (205), (206), and (207). The reflective component (201) is an optical guide that expands the reflection laterally. This reflective optical guide (201) may be a 1D optical guide (similar to the optical guide (20) in A of FIG. 4) or a 2D optical guide (similar to the optical guide (10) in C of FIG. 8). The light coupled to the reflective optical guide (201) includes all the wavelengths of the internally coupled light (38), and thus the reflective optical guide (201) may include a reflector (such as the reflective surface (16) in A of FIG. 4) or a prism (such as the inclined prism (7) in C of FIG. 8).

[0065] The facet (203) (depicted in C of FIG. 15 which is a plan view) converts the guided light forward and from the optical guide (201) to the optical guides (205), (206), and (207). Each of the optical guides (205), (206), and (207) has its respective internal coupling grating (209R), (209G), (209B). These internal coupling gratings (209R), (209G), (209B) have different periods for each optical guide, and thus different wavelengths will be coupled by their respective internal coupling gratings to the optical guides associated with them respectively.

[0066] The light propagates within the optical guides (205), (206), and (207) and is externally coupled (38B) towards the observer (47) by respective gratings (25R), (25G), (25B) designed according to the wavelengths within each optical guide and matched to their respective internal coupling gratings (209R), (209G), (209B).

[0067] Generally, the reflective optical component (facet (203)) is configured to expand the internally coupled light (38) in a first expanding direction within the first optical waveguide (201), thereby generating a first expanded light (38C). The first diffractive optical component (209R), the third diffractive optical component (209G), and the fourth diffractive optical component (209B) are each configured to couple the respective wavelengths of the first expanded light in the first optical waveguide (205), the second optical waveguide (206), and the third optical waveguide (207). The second diffractive optical component (25R), the fourth diffractive optical component (25G), and the sixth diffractive optical component (25B) are each configured to expand and externally couple their respective lights in a third direction as externally coupled light (38B).

[0068] Referring now to D of FIG. 15, diagrams of the diffraction directions of FIGS. 15A, 15B, and 15C for light propagating within an angular region (angular interval) are shown. Front views of the angular directions of a single optical waveguide shown in FIGS. 15A - 15C are shown in FIG. 15D. The light is coupled in direction (1005) and the reflective mirror (203) redirects it to direction (1007) without dispersing the light rays. A diffractive internal coupling component (one of (209R), (209G), (209B)) redirects the light rays downward while dispersing them, while a diffractive component (one of the gratings (25R), (25G), (25B)) has an opposing optical power and thus the light couples without dispersion (in the overlapping direction (1007)).

[0069] This configuration has strong anti - dispersion characteristics and thus can transmit one or more color channels (R, G, B) in a narrow field (angular spectrum) using a small number of components. For example, the three optical waveguides (205), (206), and (207) can be implemented as a single optical waveguide, or combinations of two color channels can be implemented within a single optical waveguide (such as a set of {red and green, blue} or {red, green, and blue}).

[0070] Note that the above examples, the reference signs used, and the illustrative calculations are provided to assist in the description of this embodiment. Despite any inadvertent typographical errors, mathematical errors, and / or the use of simplified calculations, the usefulness and fundamental advantages of the present invention are not impaired.

[0071] Regarding the fact that the appended claims are drafted without multiple dependencies, this is done merely to comply with the formal requirements in a legal jurisdiction that does not permit such multiple dependencies. It should be noted that any combination of features implied by making the claims depend on each other in a compound manner should be explicitly contemplated and considered as part of the present invention.

[0072] It is to be understood that the above description is intended only as an example, and that many other embodiments are possible within the scope of the present invention as defined by the appended claims.

Claims

1. 1. An apparatus for optical aperture expansion comprising: (a) at least one light guide; (b) a set of three optical components associated with the at least one light guide, (i) a pair of first and second matching diffractive optics; and (ii) a set of three optical components, including a reflective optical component that includes an array of a plurality of partially reflective, mutually parallel surfaces; and (c) optical components cooperating to expand the incoupled light into the outcoupled light; (i) the incoupled light is light coupled into the at least one light guide; and (ii) The apparatus, wherein the magnification is two-dimensional.

2. (a) a first optical component of the set is configured to direct the intercoupled light in a first direction of expansion within a first light guide, thereby generating a first expanded light; (b) a second optical component of the set is configured to couple the first expanded light into a second light guide in a second direction of expansion, thereby producing a second expanded light; and (c) a third optical component of the set configured to outcouple the second expanded light in a third direction as the outcoupled light; (d) wherein the first, second and third directions are not parallel to one another.

3. (a) a non-diffractive optic configured to direct light as the incoupled light into the at least one light guide; (b) wherein the at least one light guide is a single light guide, the single light guide comprising: (i) a first diffractive optical element configured to direct the intercoupled light in a first direction of magnification within the one light guide, thereby generating a first expanded light; (ii) a second diffractive optical element configured to magnify the first expanded light in the one light guide in a second direction of magnification, thereby generating a second expanded light; and (iii) a reflective optic configured to outcouple the second expanded light in a third direction as the outcoupled light; (iv) The apparatus of claim 1, wherein the first, second and third directions are not parallel to one another.

4. (i) a pair of third and fourth matching diffractive optics; and The apparatus of claim 1 , further comprising: (ii) a pair of fifth and sixth matching diffractive optical elements.

5. 5. The apparatus of claim 4, wherein each of the matched pairs of diffractive optical components has a different diffraction interval from the other of the matched pairs, the diffraction interval being such that each of the matched pairs of diffractive optical components deflects different wavelengths by a similar angle from the other of the matched pairs of diffractive optical components.

6. The device of claim 5 , wherein the wavelengths are red, green, and blue light.

7. (a) a first light guide of the at least one light guide includes first and second matching diffractive optical elements of the pair; (b) a second light guide of the at least one light guide includes third and fourth matching diffractive optics of the pair; and 6. The apparatus of claim 5, wherein: (c) a third light guide of said at least one light guide includes fifth and sixth matching diffractive optics of said pair.

8. (a) the reflective optic is configured to magnify the intercoupled light in a first direction of magnification within a first light guide, thereby generating a first expanded light; (b) first, third, and fourth diffractive optics are configured to magnify respective wavelengths of the first expanded light in the respective first, second, and third light guides in a second direction of magnification, thereby producing respective second expanded lights; and (c) second, fourth, and sixth diffractive optical elements configured to outcouple the respective second expanded light in a third direction as the outcoupled light; (d) wherein the first, second and third directions are not parallel to one another.

Images