Image display system with beam multiplication

Abstract

To uniformly "fill" a waveguide with a projected image and its conjugate image in order to achieve uniformity of a viewed image.SOLUTION: An optical system for displaying an image includes a light-guide optical element (LOE) having a coupling-in region and a propagation region, a coupling-out configuration associated with the propagation region of the LOE, an image projector for generating image illumination corresponding to a collimated image, and a beam-multiplication configuration external to the LOE. The beam multiplier is a transparent plate bonded to the LOE adjacent to the coupling-in region. The transparent plate has a partially reflective surface between the LOE and the plate, and a reflector at the opposite surface. The partially reflective surface and the reflector multiply the beam from the projector so as to fully illuminate the propagation region of the LOE with both the collimated image and a conjugate of the collimated image.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an optical system, and more particularly to an image display system employing a waveguide in which an irradiation beam is multiplied.

[0002] As an exemplary context for an implementation aspect of the present invention, various optical displays employ a light guiding optical element (LOE) (also referred to interchangeably as a "waveguide" or "substrate") for transmitting an image from an image projector facing the user's eye, and the image is typically coupled and output towards the eye by a configuration of a partial reflector or by a diffractive optical element.

[0003] In order to achieve the uniformity of the viewed image, the waveguide should be uniformly "filled" with the projected image and its conjugate image. This imposes design limitations on the size of the image projector and various other aspects of the optical design.

Summary of the Invention

[0004] The present invention is a light guiding optical system having a beam multiplication configuration for compensating for insufficient aperture filling by an image projector.

[0005] According to the teaching of one embodiment of the present invention, an optical system for displaying an image to a user's eye, comprising: (a) a light guide optical element (LOE) having two planar main outer surfaces, the two planar main outer surfaces being parallel to each other so as to assist the propagation of image illumination within the LOE by internal reflection at the main outer surfaces, the LOE having a thickness h between the main outer surfaces, and the LOE having a coupled input region and a propagation region; (b) a coupled output configuration associated with the propagation region of the LOE and configured to coupled output at least a portion of the image illumination from the LOE toward the user's eye; and (c) an image projector for producing image illumination corresponding to a collimated image, which introduces the image illumination into the coupled input region of the LOE and, by internal reflection, propagates the LOE toward the propagation region An optical system is provided comprising: (d) an image projector optically coupled to the LOE to propagate within a region; and a beam multiplication configuration associated with the LOE and configured for beam multiplication of an image irradiation introduced into the coupled input region of the LOE, wherein the beam multiplication configuration includes a transparent plate having mutually parallel outer surfaces, the transparent plate being bonded to the main outer surface of the LOE adjacent to the coupled input region, the transparent plate providing a partial reflective surface between the LOE and the plate, and further providing a reflector, the partial reflective surface and the reflector being configured to reflect the image irradiation introduced into the coupled input region into the propagation region, and thus completely illuminating the propagation region with both a collimated image and a conjugate of the collimated image.

[0006] According to further features of one embodiment of the present invention, the transparent plate has a thickness of h / 2.

[0007] According to further features of one embodiment of the present invention, the beam multiplication configuration is configured to compensate for the 1 / 2 aperture filling of the coupled input region by the image projector.

[0008] A further feature of one embodiment of the present invention includes a coupled input configuration which is associated with the coupled input region of the LOE and configured to coupled input an image illumination from an image projector into the LOE so as to propagate within the LOE by internal reflection.

[0009] According to further features of one embodiment of the present invention, the coupled input configuration includes a wedge-shaped prism positioned between the image projector and the coupled input region of the LOE, or an oblique edge at one end of the LOE between the image projector and the coupled input region of the LOE.

[0010] According to further features of one embodiment of the present invention, the system includes a first beam multiplication configuration configured to provide beam multiplication in the induction section of the LOE, and a second beam multiplication configuration configured to provide beam multiplication in the non-induction section of the LOE.

[0011] According to further features of one embodiment of the present invention, the beam multiplication configuration includes m partially reflective, mutually parallel surfaces, where m is a positive integer, the m surfaces are provided by m transparent plates, the beam multiplication configuration is configured to compensate for aperture filling of 1 / (m+1), each plate having a pair of principal parallel outer surfaces, the m plates are bonded together at their respective principal parallel surfaces to form a stack bonded to the principal outer surfaces of the LOE, the reflector provided by the outer surface of the m-th plate is the plate furthest from the LOE, and each of the m plates has a thickness equal to 1 / (m+1) of the thickness h of the LOE. [Brief explanation of the drawing]

[0012] The present invention will be described herein by reference to the attached drawings, merely as an example.

[0013] [Figure 1A] This is a schematic side view showing an image projection waveguide system with beam multiplication according to one embodiment of the present invention, employing guiding components for a reflected beam and a diffracted beam, respectively. [Figure 1B]This is a schematic side view showing an image projection waveguide system with beam multiplication according to one embodiment of the present invention, employing guiding components for a reflected beam and a diffracted beam, respectively. [Figure 2] This is a schematic side view of a waveguide employing a coupled input wedge with a conventional coupled input geometry. [Figure 3A] Figure 2 shows the results of introducing irradiation apertures of different sizes into the waveguide, achieving complete and partial filling of the waveguide, respectively. [Figure 3B] Figure 2 shows the results of introducing irradiation apertures of different sizes into the waveguide, achieving complete and partial filling of the waveguide, respectively. [Figure 4] These are schematic side views of embodiments of an image display system for compensating for half aperture filling, one-third aperture filling, and one-quarter aperture filling, respectively. [Figure 5] These are schematic side views of embodiments of an image display system for compensating for half aperture filling, one-third aperture filling, and one-quarter aperture filling, respectively. [Figure 6] These are schematic side views of embodiments of an image display system for compensating for half aperture filling, one-third aperture filling, and one-quarter aperture filling, respectively. [Figure 7] This shows the size of the coupled input area of ​​a conventional optical system using a wedge-type coupled input configuration. [Figure 8] The dimensions of the coupled input area of ​​an embodiment of the disclosed optical system using a wedge-type coupled input configuration are shown. [Figure 9] The size of the coupled input area of ​​an embodiment of the disclosed optical system using an oblique edge coupled input configuration is shown. [Figure 10] This is a schematic side view of an embodiment of the disclosed optical system in which the aperture is extended in the non-inductive portion. [Figure 11] This is a schematic side view of an embodiment of the disclosed optical system in which the aperture is extended in the non-inductive portion. [Figure 12] Figures 10 and 11 are isometric views of the optical system. [Figure 13] It is an isometric view of an optical system in which the aperture is extended in both the guiding part and the non-guiding part. [Figure 14] It is a schematic side view of an embodiment of the disclosed optical system using an air-gap coupling input configuration.

Mode for Carrying Out the Invention

[0014] The present invention is a light guiding optical system having beam multiplication, and its principle and operation can be better understood by referring to the drawings and the accompanying description.

[0015] Referring now to the drawings, FIGS. 1A and 1B schematically show one implementation according to the teachings provided herein of an optical system for displaying an image to a user's eye 100 located within a region referred to as an eye motion box (EMB) 102. The system includes a light guiding optical element (LOE) 10 (alternatively referred to as a “waveguide” or “substrate”) having two planar major outer surfaces 12, 14, the two major outer surfaces 12, 14 being parallel so as to assist in the propagation of image illumination within the LOE by total internal reflection (TIR) at the major outer surfaces 12, 14. The LOE of the present system can be considered to be virtually divided along its width into at least functionally different regions herein referred to as a “coupling input region” and a “propagation region”, as will be described in more detail below.

[0016] The coupling output configuration is associated with at least a portion of the propagation region of the LOE and is configured to couple at least a portion of the image illumination from the LOE towards the user's eye 100. In certain embodiments, the coupling output configuration is implemented as a set of mutually parallel partial reflection surfaces 16 that are disposed within the LOE and oriented obliquely with respect to the main outer surface, as shown in FIG. 1A. In other embodiments, the coupling output configuration is implemented as at least one diffractive optical element 18 that is associated with the LOE 10 and is configured to gradually couple and output a portion of the image illumination towards the user's eye, as shown in FIG. 1B. In some embodiments, the coupling output configuration may be associated with the entire propagation region such that the image is gradually coupled and output along the entire length of the propagation region. In other embodiments, the coupling output configuration may be associated with only a portion of the propagation region such that the propagation region includes a portion where the image propagates without being coupled and output.

[0017] An image projector 20, interchangeably referred to as a "POD", generates image illumination corresponding to a collimated image. The image projector 20 is optically coupled to the LOE 10 to introduce the image illumination into the coupling input region of the LOE and propagate it within the LOE by internal reflection. The POD employed in the device of the present invention is preferably configured to generate a collimated image, i.e., an image in which the light of each image pixel is an infinitely collimated parallel beam in the angular direction corresponding to the pixel position. Accordingly, the image illumination extends over an angular range corresponding to a two-dimensional angular field of view.

[0018] The image projector 20 includes at least one light source, typically deployed to illuminate a spatial light modulator, such as an LCOS chip. The spatial light modulator modulates the projection intensity of each pixel in the image, thereby generating the image. Other embodiments of the image projector 20 may include an OLED or micro-LED illumination source. Alternatively or additionally, the image projector may include a scanning configuration, typically implemented using a high-speed scanning mirror, which scans the illumination from the laser light source across the image plane of the projector, while the beam intensity changes synchronously with motion on a pixel-by-pixel basis, thereby projecting a desired intensity for each pixel. In both cases, a collimating optical system is provided to generate an infinitely collimated output projected image. Some or all of the above components are typically configured on the surface of one or more polarizing beam splitter (PBS) cube-shaped or other prism configurations, employing a reflective optical system, as is well known in the art. Alternatively, free-space optical implementations having reflective and / or refractive optical elements may be used. Details of the image projector are not part of the present invention, and for the sake of simplicity, the image projector is schematically represented here as a dashboard without attempting to describe its individual components.

[0019] Optical coupling of the image projector 20 to the LOE 10 can be achieved by any suitable optical coupling, such as via a coupled input prism having an obliquely angled input surface, or via a reflective coupling configuration, via one of the side edges and / or main outer surfaces of the LOE. An example of coupled input via a wedge prism can be found in PCT Publication WO2015 / 162611. Examples of various coupled inputs using mirrors can be found in PCT Publication WO2001 / 095027. Unless otherwise specified below, the details of the optical coupling between the image projector and the LOE are typically not important to the present invention and are schematically shown here as a non-limiting example of a wedge prism 22 applied to the edge surface of the LOE 10. Furthermore, the implementations of the present invention illustrated herein using a coupled input prism can be similarly implemented using a reflective coupling input configuration, and vice versa. The coupled input configuration is shown in Figure 2 α POD Determine the angle between POD and LOE, as shown.

[0020] One aspect of the present invention, shown in Figures 1A, 1B and 4-14, relates to a range of configurations in which light of a collimated image is guided by a light guide optical element (LOE) having a pair of principal parallel outer surfaces, but does not completely "fill" (also referred to herein as "illuminate") it, and in particular the image propagates without being an image / image conjugate pair at all points along the LOE. In such a situation, according to one aspect of the present invention, it has been found to be particularly effective to provide a beam multiplication configuration, which is associated with the coupled input region of the LOE and configured for beam multiplication of the image illumination introduced into the coupled input region of the LOE, to completely illuminate the propagation region with the image and its conjugate, as will be described in detail below.

[0021] Accordingly, the optical system shown in Figures 1A and 1B includes at least one transparent plate 26 positioned adjacent to the lower surface 12 of the LOE 10. In the embodiments shown in Figures 1A and 1B, a single transparent plate 26 is shown. The transparent plate 26 includes a partially reflective surface 24 on or near the surface 12 that acts as a beam splitter (also referred to as a “beam multiplier” and / or “beam duplicator”), so that a portion of the light striking the beam splitter is reflected back into the LOE 10, and a portion of the light passes through the plate 26 and is reflected back into the LOE 10 by the outer surface of the plate 26. Further details of the beam multiplication configuration of the present invention are provided below.

[0022] To better illustrate the advantages provided by the beam multiplication configuration shown in Figures 1A and 1B, Figures 2 and 3A show a coupled input configuration employing a wedge-shaped prism 22, using a conventional approach without the beam multiplication configuration currently disclosed. The LOE should provide image illumination to the human eye with a uniform distribution across all light propagation angles (also referred to as the “field” or “visual field” FOV) and throughout the EMB 102. For this purpose, the aperture of each field should be evenly filled with light. In other words, for any illumination angle corresponding to a pixel in the collimated image, the entire cross-section of the LOE in a plane perpendicular to the main surface of the LOE is filled with both the image and its reflectors (conjugates), and therefore, at any point in the LOE volume, rays should be present corresponding to all pixels in both the collimated image and its conjugates. To achieve this result, as shown in Figure 3A, an image projector 20 with a relatively large aperture was used, along with an extension of the LOE to one of the main surfaces 12, so that the aperture of the LOE 10 received both full direct illumination of the image and full internal reflection illumination of the conjugate image internally reflected from the surface 12. In order to fill the LOE aperture in this way, the image projector 20 needed to have a correspondingly large aperture.

[0023] If the "filling" condition is not met, the light that strikes the eye will not be evenly distributed. An example of a narrow beam that does not meet this criterion is shown in Figure 3B, where a smaller image projector 20 with an optical configuration similar to that of Figure 3A is used. When aperture filling is insufficient, the light emanating from the LOE will not be evenly distributed. Non-uniformity of LOE filling can occur for several reasons, including but not limited to the use of a small aperture projector, the use of a small coupled input geometry, and certain configurations of internal facet reflections.

[0024] Referring here to Figures 4 to 6, an optical system according to an embodiment of the present invention for compensating partial aperture filling is disclosed. Generally speaking, each optical system comprises an LOE 10 having two planar main external surfaces 12, 14, wherein the two main external surfaces are parallel to each other so as to assist the propagation of image illumination within the LOE by internal reflection at the main external surfaces. The LOE has a thickness h between the main external surfaces. Along the length of the LOE, the LOE first includes a coupled input region 34, followed by a propagation region 36. Unlike the coupled input region, the propagation region is surrounded by an air barrier (or alternatively, a reflective mirror), and therefore, image illumination introduced into the propagation region undergoes TIR between the main external surfaces 12, 14.

[0025] The image is introduced into the coupled input region 34 by a projector 20 configured to produce an image illumination corresponding to the collimated image, and is optically coupled to the LOE so that the image illumination is introduced into the coupled input region of the LOE and propagates within the propagation region of the LOE by internal reflection.

[0026] The optical system is a beam multiplication configuration associated with the LOE and configured for beam multiplication of an image illumination introduced into the coupled input region of the LOE, the beam multiplication configuration further comprises m partially reflective, mutually parallel surfaces 28, where m is a positive integer, and the m surfaces are outside the LOE and parallel to the main outer surface of the LOE. The beam multiplication configuration further comprises a reflector 30. The m surfaces and reflector are configured to reflect the image illumination introduced into the coupled input region 34 into the propagation region 36, thereby completely illuminating the propagation region 36 with both the image and its conjugates.

[0027] The optical system further includes a coupled output configuration, typically implemented as a facet 16 or diffracting element 18 (shown in Figures 1A and 1B, but omitted for clarity in Figures 4-6), which is associated with the propagation region 36 and configured to coupled output at least a portion of the image illumination from the LOE toward the user's eye.

[0028] Throughout this description, the partially reflective surface 28 is also referred to as a “partial reflector” in this specification, and the fully reflective surface 30 is simply referred to as a “reflector.” As will be described in detail below, the reflectors and partial reflectors are provided by one or more transparent plates 26. Generally speaking, m plates are used to compensate for 1 / m of aperture filling. The m plates provide m+1 reflective surfaces, including one (single) reflectors and m partial reflectors. The reflectors are typically implemented as the outer surface of a plate that completely reflects impact rays by TIR. Alternatively, in some embodiments, the reflectors can be implemented as mirrors.

[0029] Referring here to Figure 4, a schematic cross-section of an optical system in which a beam doubling configuration compensates for half (1 / 2) aperture filling by the image projector is shown. In this case, a single transparent plate 26 provides the partial reflector 26 and reflector 30 and is bonded to the outer surface 12 of the LOE (also referred to herein as the “downward” main outer surface) adjacent to the coupled input region 34.

[0030] The transparent plate 26 partially extends along the length of the lower main outer surface 12 of the LOE adjacent to the coupled input region 34. The endpoint 32 of the plate 26 (referred to herein as the “critical point”) marks the end of the coupled input region 34 and the entry point of the LOE into the propagation region 36, although the distinction between the coupled input region and the propagation region is purely conceptual, as there is no physical barrier at the junction between these regions. In some embodiments, the plate 26 includes an edge 38 at the critical point, the edge being perpendicular to the main outer surface of the LOE. Importantly, image irradiation cannot enter the propagation region after hitting the edge 38. In some embodiments, for two or more plates, only the plate closest to the LOE (actually adjacent to the LOE) needs to fully extend along the coupled input region 34 and terminate at the edge 38 at point 32.

[0031] In this case, as shown in Figure 4, the beam multiplication configuration compensates for 1 / 2 aperture filling by beam multiplication (also referred to herein as "beam duplication") of the image illumination entering the propagation region, so that the propagation region is fully illuminated by both the image (indicated as a downward arrow) and its conjugate (indicated as an upward arrow). As shown in Figure 4, each ray is duplicated by the beam splitter, with part of the ray reflected from the partial reflector 28 and part of the ray reflected from the full reflector 30, thereby effectively extending the critical point 32 further along the length of the LOE, so that each ray and its conjugate fills the propagation region 36 of the LOE, thereby compensating for less aperture filling by the projector that would be insufficient to fully illuminate the propagation region with both the image and its conjugate. To achieve a uniform intensity distribution for the image and conjugate image, the lower surface of the transparent plate 26 acts as a perfect reflector 30 (e.g., via TIR or mirror coating), and ideally, the upper surface of the plate 26 should be coated to uniformly reflect 36% to 40%, most preferably 38.2%, of the impact light within the angular range of the image.

[0032] To clarify, projector 20 can alternatively inject the conjugate of the image, in which case the downward arrow should be understood to represent the conjugate and the upward arrow to represent the image. Therefore, throughout this explanation, the terms “image” and “conjugate” should be understood to be interchangeable such that a reference to “image” can also mean the conjugate of the image, in which case any reference to “conjugate” will be understood as a reference to the image.

[0033] In some embodiments, the optical system may include a wedge-type coupled input configuration between the projector 20 and the LOE 10.

[0034] As discussed above, compensation for smaller partial aperture filling is also considered. Figure 5 shows an optical device that compensates for an injected ray, filling only 1 / 3 of the size of the area filled by the full aperture injection ray (i.e., 1 / 3 of the size of what is filled by the ray shown in Figure 3A). Without compensation, the LOE would be only partially filled (Figure 3B). To compensate for 1 / 3 aperture filling (N=3), two (N-1=2) partial reflectors 28 are required. In the exemplary implementation shown in Figure 5, the two partial reflectors are implemented using two transparent plates 26, each having a thickness of h / 3, with a total thickness given by h*2 / 3. In this case, the two transparent plates 26 are bonded together and then form a “stack” bonded to the surface 12 of the LOE adjacent to the coupled input region 34. The two transparent plates are bonded together at their main outer surfaces, collectively providing two partial reflectors 28 and reflectors 30.

[0035] To achieve a uniform distribution of image conjugate images, the interface between the upper (first) plate and the LOE may include a partially reflective coating having a reflectivity of 21% to 24%, preferably 22.8%. The interface between the bottom (second) plate and the upper (first) plate may be coated with a partially reflective coating having a reflectivity of 37% to 40%, preferably 38.2%. The lower main outer surface of the bottom (i.e., second) transparent plate acts as a perfect reflector, similar to that described with reference to Figure 4.

[0036] Figure 6 shows an optical device that compensates for injected rays, filling only 1 / 4 of the size of the area filled by the full aperture injected ray (i.e., 1 / 4 of the size of what is filled by the ray shown in Figure 3A). To compensate for the 1 / 4 aperture filling (N=4), three (N-1=3) partial reflectors 28 are required. In the exemplary implementation shown in Figure 6, the three partial reflectors 28 are implemented using three transparent plates 26, each having a thickness of h / 4, with a total thickness of h*3 / 4.

[0037] To achieve a uniform distribution of image conjugate images, the interface between the upper (first) plate and the LOE may include a partially reflective coating having a reflectivity of 15% to 17%, preferably 16.1%. The interface between the intermediate (second) plate and the upper (first) plate may be coated with a partially reflective coating having a reflectivity of 21% to 24%, preferably 22.8%. The interface between the intermediate (second) plate and the bottom (third) plate may be coated with a partially reflective coating having a reflectivity of 37% to 40%, preferably 38.2%. The lower main outer surface of the bottom (i.e., second) transparent plate acts as a perfect reflector, as described with reference to Figures 4 and 5.

[0038] Generally speaking, a beam multiplication configuration includes m partial reflectors parallel to the main outer LOE surface, provided by m transparent plates, where m is a positive integer. The number of partial reflectors is determined by the formula m = N - 1, where 1 / N represents the fraction of aperture filling to be compensated. The partial reflectors are arranged in a spaced-out relationship, with the first partial reflector placed on or near the lower main outer surface 12 of the LOE. The spacing between the partial reflectors is proportional to the thickness h of the LOE and determined by the thickness of the plates. A full reflector 30 is arranged below the partial reflectors, in particular below the last partial reflector (which is also the first partial reflector when only one partial reflector is used). The full reflector is arranged in a spaced-out relationship with respect to and below the last partial reflector, such that the effective spacing between the full reflector and the lower main outer surface 12 of the LOE (equivalently, or nearly equivalently, the first partial reflector) is also proportional to h. In general, the effective distance between the perfect reflector and the lower main outer surface of the LOE can be expressed by the formula h*(N-1) / N. To achieve such a distance, the thickness of each of the m plates should preferably be 1 / (m+1) of h.

[0039] For more than one transparent plate, each interface between plates and the interface between the first plate (i.e., the plate adjacent to the LOE) and the LOE include a partial reflective coating. Several different coating methods are possible. For example, each plate can be coated on one surface and bonded together to the LOE, so that each interface includes a partial reflective coating. Alternatively, every other plate (i.e., every other plate in the stack) can each be coated with a partial reflective coating on both of its main outer surfaces. Alternatively, partial reflectivity can be achieved by stacking plates with different refractive indices (or using an optical adhesive) selected to produce the desired partial reflectivity at the interface between plates. Alternatively, the optical adhesive between plates can have a different refractive index than the plates, selected to produce the desired partial reflectivity.

[0040] To achieve uniform intensity of the image and conjugate image, the upper surface of plate i is subjected to TIR.

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[0041] Preferably, the reflectance of each of the m consecutive partial reflectors is R as detailed above. i This is given using the formula for . However, the percentage of reflectance is a parameter that, in all cases, cannot be precisely defined or precisely achieved, at least over the entire angular range of the image (field of view). The intention here is to refer to a value that is sufficiently close to the theoretical value at which the resulting intensity distribution, when sampled, is visually perceived as uniform across the thickness of the LOE. For a single partial reflector (m=1), an error of 5-10% in reflectance is visually acceptable even after half a cycle. More generally, a variation of ±5%, or even ±10%, in reflectance can, in particular cases, yield a result that is sufficiently close to optimal while being visually acceptable. Parallelism between the partial reflector layer and the main outer surface of the LOE should be maintained, and the thickness should be subdivided into equal parts, preferably with an accuracy of 10% or less, to avoid producing striped, non-uniform intensity during the beam doubling process.

[0042] Structurally, the partial reflectance of a beam multiplication configuration can be implemented using any suitable partial reflectance layer or coating, including but not limited to metal coatings, structural partial reflectors (e.g., polka-dot pattern reflectors), and multilayer dielectric coatings. In some embodiments, the partial reflectance coating may be implemented using an angle-dependent reflectance coating, preferably such that the coating has low reflectance at small angles (nearly perpendicular to the beam splitter) while having the desired reflectance at angles within a range corresponding to the angle of image light propagation in the LOE, according to the sequence described above, resulting in less attenuation of light from the directly viewed scene. Layers having such angle-dependent reflectance can be readily achieved using multilayer dielectric coatings, and are easy to manufacture as the required properties are essentially analogous to Fresnel reflectance properties. The design of multilayer coatings to provide such angle-dependent reflectance can be done using standard software packages, as is practiced in the art, and suitable coatings are commercially available from many sources. Therefore, for the sake of brevity of the presentation, further details will not be discussed here.

[0043] The embodiments described so far relate to beam multiplication when using a wedge as a coupling input mechanism for injecting a ray into the LOE, but other embodiments are also possible in which other coupling input geometries are intended.

[0044] To illustrate, Figure 7 repeats the full aperture filling of the LOE when using a wedge 22 as the coupling input mechanism. The wedge is optically designed so that the aperture is completely filled, i.e., upward and downward rays exist at every point in the cross-section of the LOE in a plane perpendicular to the principal outer surface of the LOE. The size of the coupling input area 34 is determined by the wedge and the field of view, and is designed so that the upward and downward rays overlap for all fields inside the LOE. In a configuration where the principal ray is coupled out of the LOE perpendicular to the LOE, the angle of the wedge relative to the LOE is selected so that it is perpendicular to the principal ray. However, if the LOE is slightly tilted (for example, for aesthetic reasons), the angle of the wedge should be adjusted to account for the tilt angle to minimize chromatic aberration. Furthermore, the length of the wedge is determined according to the shallowest ray that can be induced through the LOE. The propagation area 36 starts from the end of the coupling input area 34 and continues along the entire length of the LOE.

[0045] As discussed in detail above, the partial aperture filling technique by beam multiplication (e.g., the half-aperture filling technique shown in Figure 4 and reproduced in more detail in Figure 8) relies on replicating the incident ray using one or more transparent plates 26 to completely fill the aperture. However, as is evident from Figure 8, the transparent plates 26 increase the size of the coupled input region 34 compared to the full aperture method shown in Figure 7 (i.e., the transparent plates extend along a considerable portion of the lower main outer surface 12 of the LOE).

[0046] With the above in mind, Figure 9 shows an optical device according to an embodiment of the present invention, having a beam multiplication mechanism that simultaneously reduces the size of the coupled input area 34 compared to the coupled input area 34 of Figure 8. In such an embodiment, the entire aperture is irradiated, however, the wedge-shaped coupled input mechanism is replaced by an oblique edge 40 (i.e., an edge angled with respect to the parallel main outer surface of the LOE). Generally, a particular angle of the oblique edge 40 is selected according to the same criteria used to select the wedge angle considered above. Since there is no wedge for replicating the upward and downward rays, the rays are injected directly into the LOE via the oblique edge 40. A transparent plate 26 (similar to the one described above) replicates and overlaps the upward and downward rays. Furthermore, since there is no wedge acting as a coupled input mechanism, the overall input aperture of the optical device is smaller (compared to the optical device of Figure 8), and the size of the coupled input area 34 (i.e., as defined by the length of the transparent plate) is smaller than the size of the coupled input area 34 of Figure 8. As a side note, the reduced overall input aperture has the additional advantage of reducing the overall shape factor of the optical device, making it suitable for use in near-eye display (NED) systems.

[0047] Up to this point, we have considered input aperture extension in relation to aperture extension in the induction section of LOE10. In some cases, aperture extension in the non-induction section may also be necessary. As used herein, the "induction section" refers to the portion between the main surfaces where light is guided by TIR, and the "non-induction section" refers to the portion extending parallel to the main surfaces where the optical path expands without being restricted by internal reflection.

[0048] Figure 10 shows an optical system in which the aperture is extended in the non-inductive portion. To compensate for the partial filling of the aperture when the light ray is not guided by the TIR, a transparent plate 26 having a lower main surface 28 coated with a partial reflective coating is positioned between the wedge 22 and the edge of the LOE 10, so that a portion of the upper main outer surface of the transparent plate 26 acts as a mirror 30, and the lower main outer surface of the transparent plate acts as a partial reflector 28. The transparent plate effectively reflects the incident light ray so that the partially filled input light ray is replicated. To fill the entire aperture, the thickness h of the transparent plate 26 is m It is selected to have half of the aperture stop S of the optical system.

[0049] Figure 11 shows another depiction of the optical system in Figure 10, with the addition of a diagram showing that rays from different fields (indicated by a non-parallel set of parallel rays) fill all of stop S of the optical system (which is half the size of the original full aperture optical system).

[0050] Figure 12 is an isometric view of the optical systems of Figures 10 and 11, showing the transparent plate 26 coupled to the LOE input. For clarity, a coupled input configuration is assumed to exist, although it is not shown in Figure 12. Two rays are duplicated by the transparent plate 26, then propagate through the LOE before reaching the coupled output configuration (shown in Figure 12 as diagonals representing facets) and coupled out toward the EMB (not shown).

[0051] Figure 13 shows a cross-sectional and isometric view, respectively, of an embodiment of an optical system similar to that in Figure 12, but with an additional transparent plate 26' at the LOE input to perform beam replication in the LOE guidance section (as discussed with reference to Figures 4-9, for example).

[0052] Figure 14 shows another optical system that performs beam multiplication in a non-inductive section according to one embodiment of the present invention. It is in contrast to the embodiments described with reference to Figures 10–12. In this embodiment, no wedge is used to couple the ray into the LOE. Instead, the incident beam (ray) is injected into the LOE from a projector (not shown) through an air gap 44 (shown in exaggeration for clarity). As described with reference to Figures 10–12, a transparent plate is positioned between the air gap 44 and the LOE 10. The beam expands (as previously described) partly due to the transparent plate 26 and partly due to the refraction of the beam as it moves from the medium of the air gap 44 with a lower refractive index to the medium of the higher refractive index (e.g., the LOE, which is typically constructed from glass). The expansion due to refraction is referred to as beam diameter expansion. As shown in Figure 14, a beam with diameter d1 collides across a segment of the transparent plate with length H at an incident angle θ1 (measured with respect to the normal). A refracted beam has a beam diameter d2 and a refraction angle θ2 (measured with respect to the normal). Using simple geometry, the following mathematical relationships can be easily derived.

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[0053] In the embodiments disclosed above with reference to Figures 1A and 1B and Figures 4-14, it should be emphasized that light entering the propagation region of the LOE was previously reflected only by partial and / or complete reflectors. In no case shall light reflected from the edges of the transparent plates (i.e., the edges of the transparent plate 26 perpendicular to the LOE surfaces 12, 14) enter the propagation region of the LOE.

[0054] It will be understood that the display includes various additional components, typically including a controller for operating an image projector, which typically employs power from a small onboard battery or several other suitable power sources. The controller will be understood to include all necessary electronic components, such as at least one processor or processing circuit, for driving the image projector, as is well known in the art. These features are not part of the invention itself and will not be described in detail here. All such features will be readily implemented by those skilled in the art.

[0055] In this specification, an expanded beam is referred to as "fully illuminating" the propagation region in the sense that the beam doubling configuration overcomes the beam width limitations provided by the image projector, ensuring that both the image and its conjugates are provided across the entire area of ​​the entry aperture to the LOE. Clearly, "full" illumination is evaluated by the ability to produce a combined output image without holes or black lines significant enough to be perceived and bothersome by the observer's eye. Minor imperfections in filling the LOE that do not significantly affect the user experience are clearly acceptable and are encompassed by the expression "fully illuminating".

[0056] The above description is intended to serve only 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 displaying an image to the user's eye, (a) A light guide optical element (LOE) having two planar main outer surfaces, wherein the two planar main outer surfaces are parallel to each other so as to support the propagation of image irradiation within the LOE by internal reflection at the main outer surfaces, the LOE has a thickness h between the main outer surfaces, and the LOE has a coupling input region and a propagation region, (b) The coupling input region configured to couple with the LOE image irradiation corresponding to the collimated image, such that the image irradiation is propagated into the propagation region of the LOE by internal reflection. (c) A coupled output configuration which is associated with the propagation region of the LOE and is configured to coupled output at least a portion of the image irradiation from the LOE toward the user's eye, (d) A beam multiplication configuration which is associated with the LOE and is configured for beam multiplication of the image irradiation introduced into the coupling input region of the LOE, The beam multiplication configuration comprises m partial reflectors, where m is a positive integer, and the m partial reflectors are located outside the LOE and parallel to the main outer surface of the LOE. The beam multiplication configuration further comprises a reflector, The m partial reflectors and the reflectors are configured to reflect the image illumination introduced into the coupled input region into the propagation region, thereby completely illuminating the propagation region with both the collimated image and its conjugate. The m partial reflectors extend along the length of the LOE adjacent to the coupling input region, An optical system in which at least one of the m partial reflectors is located inside the beam multiplication configuration.

2. The optical system according to claim 1, wherein the m partial reflectors extend along the length of the LOE, adjacent only to the coupled input region.

3. The optical system according to claim 1, wherein the air barrier surrounds the propagation region such that the image irradiation introduced into the propagation region undergoes total internal reflection (TIR) ​​between the main outer surfaces.

4. The optical system according to claim 1, wherein the m partial reflectors partially extend along the length of the lower main outer surface of the LOE adjacent to the coupled input region.

5. The optical system according to claim 1, wherein the endpoints of the m partial reflectors are edges of the partial reflectors, the edges are adjacent and perpendicular between the coupled input region and the propagation region, and the edges are configured to prevent image illumination from entering the propagation region.

6. The optical system according to claim 1, wherein the m partial reflectors are provided by m transparent plates, each plate having a pair of principal parallel outer surfaces, and the m plates are bonded together on their respective principal parallel surfaces to form a stack bonded to the principal outer surface of the LOE.

7. The optical system according to claim 1, wherein the reflector is provided by the outer surface of the m-th transparent plate, which is the transparent plate furthest from the LOE, and the outer surface is configured to reflect completely through the TIR.

8. The optical system according to claim 1, wherein the reflector is provided by a mirror.

9. The optical system according to claim 6, wherein each of the m plates has a thickness equal to h / l / (m+1).

10. The optical system according to claim 1, wherein the beam multiplication configuration is configured to compensate for l / (m+1) filling of the coupled input region by the image projector.

11. The optical system according to claim 1, further comprising an image projector for generating an image illumination corresponding to a collimated image, the image projector being optically coupled to the LOE such that the image illumination is introduced into the coupled input region of the LOE and propagated into the propagation region of the LOE by internal reflection.

12. The optical system according to claim 1, further comprising a coupled input configuration associated with the coupled input region of the LOE and configured to coupled input the image illumination into the LOE so as to propagate into the LOE by internal reflection.

13. The optical system according to claim 12, wherein the coupled input configuration comprises a wedge-shaped prism positioned between the image projector and the coupled input region of the LOE.

14. The optical system according to claim 12, wherein the combined input configuration includes an oblique edge at one end of the LOE between the image projector and the combined input region of the LOE.

15. The optical system according to claim 1, wherein the coupled output configuration comprises a plurality of mutually parallel facets angled obliquely with respect to the main outer surface of the LOE.

16. The optical system according to claim 1, wherein the coupled output configuration comprises a diffracting element.

17. An optical system for displaying an image to the user's eye, (a) A light guide optical element (LOE) including an induction portion and a non-induction portion, having two planar main outer surfaces, the two planar main outer surfaces being parallel to each other so as to support the propagation of image irradiation in the induction portion within the LOE by internal reflection at the main outer surfaces, the LOE having a thickness h between the main outer surfaces, the LOE having a coupled input region and a propagation region, and the non-induction portion being a portion in which the propagation of the image irradiation is not restricted by internal reflection at the main outer surfaces, LOE, (b) The coupling input region configured to couple the image irradiation to the LOE image irradiation corresponding to the collimated image so as to propagate the image irradiation into the LOE, wherein the propagation of the LOE in the induction section within the propagation region due to internal reflection, the coupling input region, (c) A combined output configuration configured to combine and output at least a portion of the image irradiation from the LOE toward the user's eye, (d) A beam multiplication configuration, which is associated with the LOE and configured for beam multiplication of the image irradiation introduced into the coupling input region of the LOE, The beam multiplication configuration comprises m partial reflectors, where m is a positive integer, and the m partial reflectors are located outside the LOE and parallel to the main outer surface of the LOE. The beam multiplication configuration further comprises a reflector, The m partial reflectors and the reflectors are configured to reflect the image illumination introduced into the coupled input region into the propagation region, thereby completely illuminating the propagation region with both the collimated image and the conjugate of the collimated image. The m partial reflectors extend along the length of the LOE adjacent to the coupling input region, The beam multiplication configuration is configured to provide beam multiplication to the non-inductive section, An optical system in which at least one of the m partial reflectors is located inside the beam multiplication configuration.

18. The optical system according to claim 17, further comprising another beam multiplication configuration configured to provide beam multiplication to the induction unit.

19. The optical system according to claim 17, further comprising a coupled input configuration associated with the coupled input region of the LOE and configured to coupled input the image irradiation into the LOE.

20. The optical system according to claim 19, wherein the coupled input configuration includes a wedge-shaped prism positioned between the image projector and the coupled input region of the LOE, and configured to couple the image irradiation corresponding to the collimated image into the non-inductive portion.

21. The optical system according to claim 19, wherein the coupled input configuration includes an oblique edge portion at one end of the LOE between the image projector and the coupled input region of the LOE, and is configured to couple the image irradiation corresponding to the collimated image into the non-inductive portion.

22. The optical system according to claim 19, wherein the coupled input configuration includes an air gap adjacent to the first reflector of the m partial reflectors, the air gap being configured for beam diameter expansion of the image irradiation onto the LOE.

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