Method and system for high-resolution digital display

Abstract

The present invention relates to methods and systems for high-resolution digital displays. Methods and systems for increasing the dynamic digital wavefront resolution (i.e., the density of output sub-beams) can include receiving a single collimated source beam and generating a plurality of output sub-beams that are spatially offset when out-coupled from a waveguide. The plurality of output sub-beams can be obtained by offsetting and replicating the collimated source beam. Alternatively, the plurality of output sub-beams can be obtained by using a collimated input source beam having a plurality of input beams with different wavelengths near the nominal wavelength of a particular color. The collimated incident source beam can be in-coupled into an eyepiece designed for the nominal wavelength. The input beams having multiple wavelengths take different paths when undergoing total internal reflection in the waveguide, which generates a plurality of output sub-beams.

Description

[0001] This application is a divisional application of the application with application number 201780073726.X, application date November 29, 2017, and invention title "Methods and Systems for High-Resolution Digital Displays".

[0002] Cross - reference to related applications

[0003] This application claims the priority of U.S. Provisional Patent Application No. 62 / 428,510, filed on November 30, 2016, the content of which is incorporated herein by reference in its entirety for all purposes. Background of the Invention

[0004] Modern computing and display technologies have facilitated the development of systems for so - called "virtual reality" or "augmented reality" experiences, in which digitally generated images or portions thereof are presented to a user in a wearable device in a manner in which they appear or feel real. A virtual reality or "VR" scenario typically involves presenting digital or virtual image information while occluding other actual real - world visual inputs; an augmented reality or "AR" scenario typically involves presenting digital or virtual image information as an augmentation of the visualization of the real world surrounding the user.

[0005] Wearable devices can include augmented and / or virtual reality glasses. Image frames or raster - scanned images can be used to display images. In a scanned - image display system, each light beam defines a pixel of the image. By scanning mirrors on two orthogonal axes, a two - dimensional field of view can be created. The image can be projected onto the glasses lenses, which can include waveguide - based eyepieces and other optical elements, such as optical fibers. The image display system can be mounted on each of the left and right sides of the glasses frame. Summary of the Invention

[0006] In a scanned - image display system employing a scanned projector and a waveguide eyepiece, the image light beam undergoes total internal reflection (TIR) inside the waveguide eyepiece. At each reflection point where the image light beam reaches the output coupling element, a beamlet is coupled out of the waveguide. If the density of these output photon beams is low, i.e., the resolution of the output wavefront is low, the image quality is poor. For example, when viewed through an observation box, the image at the depth plane suffers from "screen door" artifacts or wavefront sparsity artifacts. To the user, this looks like viewing an image through a screen door.

[0007] Some embodiments of the present invention provide a method and system for increasing the dynamic digital wavefront resolution, i.e., the density of output sub-beams, by offsetting and replicating a collimated source beam. The source can be replicated, repeated, or cloned to form multiple sub-beams, and the sub-beams are laterally offset or displaced such that there effectively exist multiple collimated beam sources. The method provides a way to increase the sub-beam density that is independent of the substrate thickness. It also highlights the focus / accommodation cues passed from the eyepiece to the eye.

[0008] Alternatively, certain embodiments of the present invention provide a method and system for increasing the density of output sub-beams through wavelength diversity. The collimated incident source beam can include multiple input beams having different wavelengths near a nominal wavelength of a particular color. The incident source beam can be internally coupled into an eyepiece designed for the nominal wavelength. The input sub-beams having multiple wavelengths are diffracted slightly differently when internally coupled into the waveguide, and thus follow different paths when they undergo total internal reflection in the waveguide and are coupled out at different positions to produce multiple offset output sub-beams.

[0009] According to some embodiments of the present invention, an image display system includes a waveguide and an optical device configured to receive an incident beam and provide multiple input sub-beams to the waveguide. Each input sub-beam is derived from a portion of the incident beam, and the input sub-beams are spatially offset from each other. The waveguide is configured to receive the multiple input sub-beams using an input coupling element, propagate the multiple input sub-beams through total internal reflection (TIR), and output multiple sets of output sub-beams using an output coupling element. Each set of output sub-beams includes a portion of each input sub-beam among the multiple input sub-beams propagated through the waveguide by total internal reflection.

[0010] In some embodiments of the above image display system, the optical device includes a first surface and a second surface that are parallel and adjacent to each other. The first surface is partially reflective, and the second surface is substantially fully reflective. In some embodiments, the partially reflective first surface is configured to receive a beam, reflect a first portion of the received beam, and allow a second portion of the received beam to pass through. The second surface is configured to reflect each beam received from the first surface back to the first surface. For each beam guided from the second surface to the first surface, the partially reflective first surface is configured to allow a portion to pass through toward the waveguide to form a new sub-beam and reflect the remaining portion back to the second surface.

[0011] In some embodiments of the above image display system, the optical device further includes a third surface and a fourth surface that are parallel and adjacent to each other. The third surface is partially reflective, and the fourth surface is substantially fully reflective. The first and second surfaces are configured to receive the incident beam and provide a first plurality of sub-beams. The third and fourth surfaces are configured to receive each of the first plurality of sub-beams and provide multiple sub-beams.

[0012] In some embodiments of the above image display system, the first and second surfaces are configured to form an internal coupling angle with the top surface of the waveguide such that an input grating in the waveguide is not required.

[0013] According to some embodiments of the present invention, a method for displaying an image includes: providing a waveguide, receiving an incident light beam and providing a plurality of input sub-beams to the waveguide, the input sub-beams being spatially offset. The method further includes receiving the plurality of input sub-beams in the waveguide and propagating the plurality of input sub-beams along different paths in the waveguide by total internal reflection (TIR). The method further includes using an output coupling element to output multiple sets of output sub-beams. Each set of output sub-beams includes a portion of each of the plurality of input light beams propagating in the waveguide by total internal reflection.

[0014] According to some embodiments of the present invention, an alternative image display system includes a waveguide and a light source for providing a collimated incident light beam, the collimated incident light beam including a plurality of input light beams having different wavelengths. The waveguide is configured to couple the plurality of input light beams into the waveguide using a wavelength-sensitive input coupling element and propagate the plurality of input light beams by total internal reflection (TIR), each input light beam propagating along a different path in a different direction. The system is further configured to use an output coupling element to output multiple sets of output photon beams. Each set of output photon beams includes a portion of each of the plurality of input light beams propagating in the waveguide by total internal reflection.

[0015] In an embodiment of the above system, the waveguide is configured for a nominal wavelength of a color, and the plurality of input light beams have wavelengths near the nominal wavelength.

[0016] According to some embodiments of the present invention, a method for displaying an image includes: providing a waveguide, and providing a collimated incident light beam. The collimated incident light beam includes a plurality of input light beams having different wavelengths. The method further includes using a wavelength-sensitive input coupling element to internally couple the plurality of input light beams into the waveguide and propagating the plurality of input sub-beams by total internal reflection (TIR). Each sub-beam is configured to propagate along a different path. The method further includes using an output coupling element to output multiple sets of output sub-beams. Each set of output sub-beams includes a portion of each of the plurality of input light beams propagating in the waveguide by total internal reflection.

[0017] Additional features, benefits, and embodiments are described below in the detailed description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a simplified schematic perspective view showing an exemplary wearable display device according to some embodiments of the present invention;

[0019] Figure 2is a simplified schematic diagram showing a scanning display system according to some embodiments of the present invention;

[0020] Figure 3 is a simplified schematic diagram showing an image display system according to some embodiments of the present invention;

[0021] Figures 4A to 4D shows an output sub-beam wavefront from an image display system according to some embodiments of the present invention;

[0022] Figures 5A to 5D is a simplified schematic diagram showing an image display system according to some embodiments of the present invention;

[0023] Figure 6A and Figure 6B is an image showing the reduction of the shutter door effect by the above optical device according to some embodiments of the present invention;

[0024] Figure 6C is a simplified diagram showing an experimental system for verifying the function of a display system according to an embodiment of the present invention;

[0025] Figure 7A is a simplified schematic diagram showing another optical device for generating multiple output sub-beams according to some embodiments of the present invention;

[0026] Figure 7B is a simplified schematic diagram showing another optical device for generating multiple output sub-beams according to some embodiments of the present invention;

[0027] Figure 8 is a simplified flowchart showing a method for displaying an image with reduced wavefront sparsity effect or shutter door effect according to an embodiment of the present invention.

[0028] Figure 9 is a simplified schematic diagram showing an image display system according to an alternative embodiment of the present invention;

[0029] Figure 10A and Figure 10B is an image showing the reduction of the shutter door effect by the above optical device according to some embodiments of the present invention;

[0030] Figure 11 is a simplified flowchart showing a method for displaying an image with reduced wavefront sparsity effect or shutter door effect according to an embodiment of the present invention. Detailed Description

[0031] Representative applications of the methods and apparatuses according to the present application are described in this section. These examples are provided solely to add background and facilitate understanding of the described embodiments. Thus, it will be clear to those skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well-known processing steps are not described in detail to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be considered limiting.

[0032] Figure 1 is a simplified schematic perspective view showing an exemplary wearable display device 100 according to some embodiments of the present invention. The wearable display device 100 includes a main display 110. In some embodiments, the wearable display device 100 further includes a projector assembly 120 that is integrated into the temple 130. The projector assembly 120 may include a projector that irradiates light through diffractive optics and then reflects it through the main display 110 into the user's eye.

[0033] Figure 2 is a simplified schematic view showing a scanning display system according to some embodiments of the present invention. In this example, the scanning display system 200 may be, for example, Figure 1 a part of the eyepiece in the wearable device of the wearable device 100, such as a waveguide-based eyepiece. As Figure 2 shown, the scanning display system 200 includes a scanning projector 210 that is configured to emit a light beam, such as light beam 240, across a surface 250 to project an image. In some embodiments, the scanning projector 210 may be Figure 1 a part of the projector assembly 120 in the wearable display device 100 in

[0034] Figure 3 is a simplified schematic view showing an image display system according to some embodiments of the present invention. Figure 3FIG. 0 shows a side view of an image display system 300 that includes an eyepiece having a waveguide 310. A single collimated beam 320 is directed toward the waveguide 310. The beam 320 may be provided by a scanning projector, such as a fiber optic scanner. Alternatively, the beam 320 may also be provided by collimated light reflected from a scanning mirror. The image display system 300 also includes an input coupling element 312 and an output coupling element 314. The input coupling element 312 is configured to allow incident light to propagate by total internal reflection (TIR), and the output coupling element 314 is configured to expand and out-couple the light that propagates along the waveguide 310 by TIR toward the user's eye 390. The beam 320 enters the waveguide 310 at the input coupling element 312 of the waveguide 310 and undergoes total internal reflection (TIR), as shown by the arrow 322 within the waveguide 310. An array 330 of sub-beams is out-coupled at the output coupling element 314 in the exit pupil of the waveguide 310. The array 330 of output sub-beams forms a wavefront. In some embodiments, the image display system may further include an optical element 380, such as an eye lens, that directs the image to the user's eye 390. From the user's perspective, the array of output sub-beams forms a two-dimensional wavefront, as Figures 4A to 4D further described. The density of the output sub-beams is determined by a bounce interval b, which in turn is determined by the substrate thickness t.

[0035] The input and output coupling elements 312 and 314 may be diffractive optical elements (“DOEs”) embedded within or imprinted on the waveguide 310, such as linear gratings. In some examples, the image display system 300 may further include an ortho-pupil expander (“OPE”) element (not shown) in addition to the output coupling element 314 to expand the light in the X and Y directions. The output coupling element 314 may be in the Z plane (i.e., tilted perpendicular to the X and Y directions) such that the sub-beams propagating through the waveguide 300 will be deflected 90° in the Z plane and toward the user's eye 390. The output coupling element 314 is also partially transparent and partially reflective along the optical path (Y-axis) such that the sub-beams partially pass through the output coupling element 314 to form a plurality of sub-beams spaced apart from each other by a distance b. More details regarding the input coupling element, output coupling element, OPE, and other DOEs are described in U.S. Utility Patent Application Serial No. 14 / 555,585 and U.S. Utility Patent Application Serial No. 14 / 726,424, the contents of which are incorporated herein by reference in their entirety.

[0036] Figures 4A to 4D FIG. 9 shows an output sub-beam wavefront from an image display system according to some embodiments of the present invention. Figure 4AA waveguide that shows a low-density output sub-beam forming a sparse wavefront, also known as a wavefront with low resolution. In this case, when viewed through an observation box, the image at the depth plane suffers from a "screen door" artifact, also known as a wavefront sparsity artifact (as if viewing an image through a screen door). Figure 4B Shows the screen door effect caused by wavefront sparsity. This problem is particularly severe for narrow internally coupled beams that are highly monochromatic (e.g., from a fiber scanner). For comparison, Figure 4C A waveguide that shows a higher-density output sub-beam, and Figure 4D A waveguide that shows an even higher-density output sub-beam. In the real world, these images can essentially have infinite resolution, which can provide strong depth cues.

[0037] As described above, a sparse wavefront results in undesirable image artifacts where the image appears as if being viewed through a screen door. A direct way to increase the beam density is to reduce the substrate thickness. When light bounces back and forth between the two surfaces of a waveguide at a given angle, as the two parallel surfaces get closer together, i.e., when the thickness of the waveguide decreases, the spacing or bounce interval gets smaller. However, below a certain thickness, further reducing the substrate thickness becomes extremely challenging and introduces other image quality and manufacturing problems. As described below, embodiments of the present invention provide techniques for improving wavefront resolution without relying on substrate thickness.

[0038] According to some embodiments of the present invention, to increase the dynamic digital wavefront resolution and mitigate the screen door / wavefront sparsity artifacts, the incident beam can be replicated, repeated, or cloned and laterally offset or displaced so that there are now effectively multiple collimated beam sources. This provides a way to increase the sub-beam density without relying on substrate thickness. It also emphasizes the focus and accommodation cues provided by the eyepiece to the user's eye.

[0039] Figure 5A Is a simplified schematic diagram showing an image display system according to some embodiments of the present invention. As Figure 5A Shown, the image display system 500 includes a waveguide 510 and an optical device 550 configured to receive an incident beam 520 and provide a plurality of input sub-beams 521 to the waveguide 510. Each image sub-beam 521 is from a portion of the incident beam 520. As Figure 5A Shown, four source sub-beams 521 are spatially offset such that they are directed to different positions on an input coupling element 512 that is optically coupled to the waveguide 510. Although Figure 5A Only four source sub-beams are shown, embodiments of the present invention are not limited to this particular number of source sub-beams. In other embodiments, a reduced number of source sub-beams are used, while in other embodiments, an increased number of source sub-beams are used. As regarding Figure 5CAs discussed in further detail, in some embodiments, the number of source sub-beams is a function of the spatial parameters associated with the optical device 550, the additional details of which will be described more fully with respect to Figures 5B to 5D more fully.

[0040] As Figure 5A shown, the waveguide 510 is configured to receive a plurality of input sub-beams 521 at an input coupling element 512, such as an input coupling grating. In the illustrated embodiment, the source sub-beams are incident on the input coupling element 512 at normal incidence. However, this is not required by the present invention, and operation at other angles of incidence is also included within the scope of the present invention. As the source sub-beams 521 pass through the input coupling element 512, they diffract at a non-normal angle of incidence to propagate inside the waveguide 510.

[0041] After passing through the input coupling element 512 and diffracting from the input coupling element 512, the input sub-beams 521 propagate along the waveguide 510 by total internal reflection (TIR), and the reflected beams shown as 522 in Figure 5A make multiple passes as they propagate from the end of the waveguide 510 adjacent to the input coupling element 512 towards the right end of the output coupling element 514 optically coupled to the lower surface of the waveguide 510. The waveguide 510 is characterized in that its longitudinal axis is aligned with the direction in which light propagates along the waveguide. As Figure 5A shown, the longitudinal axis 505 is aligned with the top and bottom surfaces of the waveguide and is parallel to the propagation direction of the incident light beam 520.

[0042] In the waveguide, a plurality of input sub-beams propagate along the waveguide by total internal reflection (TIR), where when the sub-beams reach the surface of the waveguide, the sub-beams are all reflected back inside. This phenomenon occurs if the angle of incidence of the sub-beams is greater than the critical angle of the waveguide. As Figure 5B shown, each of the plurality of sub-beams 521 is represented by a different solid or dashed line pattern, and each of the plurality of input sub-beams passes through a different path in the waveguide.

[0043] The waveguide 510 is also configured to use an output coupling element 514, such as an output coupling grating, to output multiple sets of output sub-beams 530. The output coupling element 514 is coupled to the waveguide 510 at the surface of the waveguide. The output coupling element 514 causes the sub-beams 522 in the waveguide to be partially refracted at the surface to leave the waveguide and partially reflected back into the waveguide. In Figure 5AIn [the figure], when the sub-beams first reach the output coupling element 514 inside the waveguide, a part of each sub-beam is refracted and leaves the waveguide to form a first group of output sub-beams 531. The remaining part of the sub-beams continues to propagate by total internal reflection, and subsequent groups of output sub-beams 532 to 534 are formed when they leave the waveguide at different directions along the longitudinal axis. Therefore, each group of output sub-beams includes a part of each input sub-beam of a plurality of input photon beams propagating in the waveguide by total internal reflection. For example, as Figure 5A shown, four groups of output sub-beams 531, 532, 533, and 534. Each group of output sub-beams includes a part of each input sub-beam of a plurality of input sub-beams 521 propagating in the waveguide by total internal reflection.

[0044] Figure 5B is a simplified schematic diagram showing an image display system according to some embodiments of the present invention. As Figure 5B shown, the image display system 560 is similar to Figure 5A the image display system 500 in [the figure], but uses an optical device 550 instead of the specific implementation. In this example, the optical device 550 includes a first surface 552 and a second surface 554, which are arranged in parallel, adjacent to each other, and are arranged at an inclination angle of, for example, 45° to one or more surfaces of the waveguide 510, the input coupling element 512, and / or the output coupling element 514. The first surface 552 is partially reflective, and the second surface 554 is substantially totally reflective. Referring to the enlarged view of the optical device 550 as Figure 5C shown to further explain the operation of the optical device 550.

[0045] Figure 5C is a simplified schematic diagram showing the optical device 550 in the Figure 5B image display system according to some embodiments of the present invention. In Figure 5CIn [the figure], the partially reflective first surface 552 and the reflective second surface 554 are provided by two prisms 562 and 561 respectively, which are right triangles and have comparable dimensions. Thus, in some examples, the optical device 550 can be cubic or quasi-cubic in shape. The incident beam 520 enters the optical device 550 and provides a plurality of spatially offset image sub-beams 521. Each image sub-beam 521 is derived from a portion of the incident beam 520. In this example, the incident beam 520 is reflected by the reflective second surface 554 towards the partially reflective surface 552 at point A1. The partially reflective first surface 552 reflects the first portion of the incident beam to the second surface and allows the second portion of the incident beam to transmit through the prism to form the first sub-beam B1. Similarly, the portion of the beam reflected from the second surface 554 and reaching point A2 on the first surface 552 is partially reflected towards the second surface 554 and partially passes through the prism 562 to form the second sub-beam B2. In a similar manner, a portion of the beam reaching point A3 forms the third sub-beam B3, and a portion of the beam reaching point A4 forms the fourth sub-beam B4. For illustrative purposes, in Figure 5C the example, the reflectivity of the partially reflective surface 552 is assumed to be 50%. As a result, the intensities of the photon beams B1, B2, B3, and B4 are 1 / 2, 1 / 4, 1 / 8, and 1 / 16 of the intensity of the incident beam 520 respectively, as Figure 5C shown.

[0046] Figure 5C The intensity distribution in [the figure] is derived based on a partially reflective surface 552 with a 50% reflectivity. In some embodiments, the reflectivity can be changed to result in different sub-beam intensity distributions. In some embodiments, the reflectivity along the partially reflective surface 552 can be changed to achieve a desired intensity distribution.

[0047] The partially reflective first surface 552 may include a partially reflective coating, such as a coating consisting of: metals, such as gold, aluminum, silver, nickel-chrome, chromium, etc.; dielectrics, such as oxides, fluorides, sulfides, etc.; semiconductors, such as silicon, germanium, etc.; and / or a glue or adhesive having reflective properties, which can be applied to the prism 562 by any suitable process, such as physical vapor deposition ("PVD"), ion-assisted deposition ("IAD"), ion beam sputtering ("IBS"), etc. The ratio of reflection to transmission of such a coating can be selected or determined at least partially based on the thickness of the coating, or the coating can have multiple small perforations to control the ratio of reflection to transmission. It follows that the output coupling element 514 can include a partially reflective coating composed of one or more of the above materials. The reflective second surface 554 may include a reflective coating, which can also be composed of one or more of the above materials, but is thick enough to fully or almost fully reflect the second surface 554. In some embodiments, the respective surfaces 552 and 554 of the prisms 562 and 561 can be directly or indirectly bonded together with a glue or adhesive, such as the glue or adhesive having reflective properties as described above.

[0048] In some embodiments, the number of input sub-beams can be changed by varying the spacing between the partially reflective surface 552 and the reflective surface 554. For example, reducing the spacing between the two surfaces can result in an increase in the number of reflections between the two surfaces, generating more input sub-beams. In Figures 5A to 5C , the partially reflective first surface 552 and the reflective second surface 554 are represented by flat surfaces. In other embodiments, the partially reflective first surface and the reflective second surface can have different shapes, such as parabolic, spherical, or other shapes.

[0049] In Figure 5C , the incident beam 520 reaches the second surface 554 and is reflected towards the first surface 552. Alternatively, if the incident beam 520 enters the prism 562 before reaching the total reflection surface 554, as Figure 5D shows, then the partially reflective first surface 552 is configured to reflect a first portion of the incident beam towards the waveguide to form a first sub-beam, and allow a second portion of the incident beam to transmit through to the second surface. Subsequent sub-beams are formed in the manner described in conjunction with Figure 5C above.

[0050] Figure 6A and Figure 6B are images showing the reduction of the shutter effect by the above optical device according to some embodiments of the present invention. Figure 6A Same as Figure 4B , showing the shutter effect caused by wavefront sparsity. Figure 6BIt is an image illustrating the reduction of the shutter effect by providing multiple sub - beams from a single incident beam. The sub - beam intensities are plotted below the image. In Figure 6B the sub - beam intensities are based on Figure 5C where it is assumed that the partial mirror has a reflectivity of 0.5. In embodiments of the present invention, more improvements can be achieved by changing the sub - beam intensity distribution and increasing the number of sub - beams originating from the incident beam. These improvements can be obtained by optimizing the shape and reflectivity of the reflective surface and the partial reflective surface.

[0051] Figure 6C It is a simplified diagram of an experimental system for verifying the function of the above - mentioned display system. Figure 6C It shows a single collimated light source 610 from an optical fiber scanner and an optical device 620. The collimated light source 610 provides multiple collimated beams 611. The optical device 620 includes two prisms 621 and 622 respectively, providing a partial mirror 623 and a 100% mirror 624 respectively. A certain lateral distance is maintained between two parallel planes 623 and 624 from the two mirrors. The optical device 620 receives each of the multiple collimated beams 611 and generates multiple sub - beams 630 that are projected onto an image sensor 640. Figure 6A and Figure 6B are examples of images that can be provided by the image sensor 640.

[0052] Figure 7A It is a simplified schematic diagram of an optical device for generating multiple output sub - beams according to some embodiments of the present invention. As Figure 7A shown, the optical device 700 can be used as the optical device 550 in the Figure 5A and Figure 5B image display system. The optical device 700 can include multiple "optical devices", and each "optical device" can be similar to the optical device 550 in the optical device 700. The multiple optical devices can be positioned in a cascaded arrangement to provide additional beam cloning. As Figure 7A shown, the prisms 701 and 702 form the first optical device 721, and the prisms 703 and 704 form the second optical device 722. Both the first optical device 721 and the second optical device 722 are similar to the optical device 550, but are oriented in different directions.

[0053] In Figure 7AIn this case, the optical device 721 includes a prism 701 having a partially reflective surface 711 and a prism 702 having a reflective surface 712. Similarly, the optical device 722 includes a prism 703 having a partially reflective surface 713 and a prism 704 having a reflective surface 714. In some examples, the optical devices can be oriented differently from each other such that a 2D array of cloned sub-beams can be internally coupled into the waveguide. For example, an incident beam 710 enters the optical device 721, which provides a plurality of image sub-beams (not shown), which are spatially offset and longitudinally traverse along the waveguide. Each sub-beam entering the optical device 722 from the optical device 721 can provide a plurality of sub-beams, which form part of a plurality of input sub-beams 730 that are guided into the waveguide. As a result, a 2D array of cloned sub-beams can be internally coupled into the waveguide.

[0054] As an example, the optical device 721 is characterized by a cloning factor or multiplicity factor of m, i.e., a single input beam can produce m output sub-beams, while the optical device 722 is characterized by a cloning factor or multiplicity factor of n. Then, the cascaded optical device 700 can have a cloning factor or multiplicity factor of m×n. As Figure 5A and Figure 5B shown, each input sub-beam entering the waveguide produces a plurality of output sub-beams exiting the waveguide. The wavefront density can be significantly increased. In some embodiments, more than two optical devices can be cascaded to further increase the wavefront density.

[0055] Although mainly described in the context of triangular prisms, particularly right-angled triangular or "Porro" prisms, it should be understood that one or more of the prisms described herein can have other geometries. For example, a single Porro-Abbe prism can be implemented using four triangular prisms having fully reflective surfaces, each fully reflective surface being parallel to a corresponding one of the four hypotenuse sides of the Porro-Abbe prism, thereby providing a beam cloning function for four optical devices in a cascaded configuration. Other geometries can include any of a variety of other polyhedral geometries, such as "Amici" or Amici roof prism geometries, parallelogram prism geometries, trapezoidal prism geometries, pyramidal or semi-pyramidal prism geometries, such as tetrahedral prism geometries, cubic diagonal slices or triangular prism geometries, etc.

[0056] Figure 7B is a simplified schematic diagram showing another optical device for generating a plurality of output sub-beams according to some embodiments of the present invention. In these embodiments, the bottom prism of the optical device can provide an internal coupling function. As Figure 7BAs shown, the optical system 750 includes an optical device 760 for generating a plurality of sub-beams from an input beam and a waveguide 780 for receiving the plurality of sub-beams. The optical device 760 includes a first prism 761 having a partially reflective surface 771 and a second prism 772 having a reflective surface 772. The prisms can have geometries other than 45°-45°-90° triangular prisms such that the prisms reflect the incident light 790 into the waveguide 780 at a desired tilted internal coupling angle (e.g., different from a 90° angle). As Figure 7B shown, the surfaces 771 and 772 of the prisms form an angle α less than 45° with the top surface of the waveguide 780, which can cause the sub-beams to enter the waveguide at a tilted incident angle. Thus, in some of these embodiments, an internal coupling grating may not be required. Other geometries / configurations that provide the internal coupling function through the optical device 760 and / or the waveguide 780 can also be used. For example, the surfaces 771 and 772 of the prisms form an angle α greater than 45° with the top surface of the waveguide 780. In another example, an input coupling element (e.g., a grating) can be provided on the surface of one leg or two legs (e.g., the non-hypotenuse sides) of the first prism 761, which is in the shape of an equilateral triangle. In yet another example, the first prism 761 can have a geometry other than a triangular prism, such as a parallelogram geometry. In such an example, the first prism 761 can be arranged to internally couple light to the side surface of the waveguide 780 rather than the top surface of the waveguide 780. In some examples, the first prism 761 can be effectively integrated with the waveguide 780.

[0057] Figure 8 is a simplified flowchart showing a method for displaying an image with reduced wavefront sparsity effect or shielding gate effect according to an embodiment of the present invention. The method 800 for displaying an image includes providing a waveguide and an optical device (810) and receiving an incident beam (820). Exemplary optical devices are shown in Figure 5B and Figure 5C wherein the optical device 550 includes a first surface 552 and a second surface 554 that are parallel and adjacent to each other. In this example, the first surface 552 is partially reflective and the second surface 554 is substantially fully reflective. In some embodiments, a fiber optic scanner can be used to provide the incident beam.

[0058] The method further includes guiding the incident beam to irradiate a portion of the optical device (830) and generating a plurality of input sub-beams using the optical device (840). Refer to Figure 5C, the incident light beam 520 is directed to the second surface 554 of the optical device 550 and is reflected towards the first surface 552, where the light is partially reflected back towards the second surface 554. Another portion of the light is transmitted through the prism 562 and exits the prism 562 as the first input sub-beam B1. Subsequent input sub-beams B2, B3, and B4 are generated in a similar manner. The plurality of input sub-beams are spatially offset relative to each other. As Figure 5C shown, the input sub-beams B1 to B4 exit the prism 562 at increasing distances from the left side of the prism 562 such that each input sub-beam is positioned to illuminate the input coupling element at different longitudinal positions arranged along the longitudinal axis.

[0059] The method further includes coupling the plurality of input sub-beams into a waveguide (850) and propagating the plurality of input sub-beams along the waveguide by total internal reflection (860). Referring to Figure 5B , the input sub-beam 521 is coupled into the waveguide 510 through the input coupling element 512. In the waveguide, the plurality of input sub-beams propagate along the waveguide by total internal reflection (TIR). In TIR, when the sub-beam reaches the surface of the waveguide, the sub-beam is totally reflected back inside. In Figure 5B , each of the plurality of sub-beams 521 is represented by a different solid or dashed line pattern, collectively labeled 522, and each of the plurality of input sub-beams traverses a different path in the waveguide.

[0060] Method 800 further includes providing an output coupling element (870) optically coupled to the waveguide and using the output coupling element to output multiple sets of output sub-beams (880). As Figure 5B shown, the output coupling element 514 is coupled to the waveguide 510 at the interface between the waveguide and the ambient air. The output coupling element 514 causes the sub-beams 522 in the waveguide to be partially refracted at the boundary surface to exit the waveguide and partially reflected back into the waveguide. In Figure 5B , when the sub-beam inside the waveguide first reaches the output coupling element 514, a portion of each sub-beam is refracted and exits the waveguide to form the first set of output sub-beams 531. The remaining portion of the sub-beam continues to propagate by total internal reflection and forms subsequent sets of output sub-beams 532 to 534 at different positions along the longitudinal axis. Thus, each set of output sub-beams includes a portion of each input photon beam among the plurality of input photon beams propagating in the waveguide by total internal reflection.

[0061] In combination with the above Figure 3Figures 0 through 7 depict an example of an image display system that implements method 800. In some embodiments, the method includes providing an optical device that is configured to receive an incident light beam and provide a plurality of input sub-beams that are spatially offset. The plurality of input sub-beams can be directed to a waveguide to generate an increased number of output sub-beams, which can increase the wavefront density and reduce the shutter effect. In some embodiments, the method can further include using an eye lens to focus multiple sets of output photon beams.

[0062] It should be understood that Figure 8 the specific steps shown in provide a particular method for displaying an image with a reduced wavefront sparsity effect or shutter effect in accordance with embodiments of the present invention. According to alternative embodiments, other sequences of steps can also be performed. For example, alternative embodiments of the present invention can perform the steps outlined above in a different order. Additionally, Figure 8 each of the steps shown in can include multiple sub-steps, which can be performed in various orders suitable for each step. Additionally, depending on the particular application, additional steps can be added or removed. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives.

[0063] Figure 9 is a simplified schematic diagram showing an image display system according to an alternative embodiment of the present invention. As Figure 9 shown, image display system 900 includes a waveguide 910 configured to receive an incident light beam and a light source 905 for providing a collimated incident light beam 920. The collimated incident light beam 920 includes a plurality of input light beams having different wavelengths. As an example, in Figure 9 the collimated incident light beam 920 includes a first light beam 921 having a first wavelength and a second light beam 922 having a second wavelength.

[0064] As Figure 9 shown, two input light beams 921 and 922 having slightly different wavelengths are included in the collimated incident light beam 920 such that they are diffracted slightly differently in the input coupling element 912 and enter the waveguide 910 at slightly different incident angles. Although only two input light beams are shown in Figure 9 the embodiments of the present invention are not limited to this particular number of input light beams. In other embodiments, an increased number of input light beams are used. As can be seen in Figure 9 increasing the number of input light beams can increase the number of output sub-beams and further increase the wavefront density of the output image.

[0065] In some embodiments, the different wavelengths are selected from a wavelength range centered on the nominal wavelength for which the waveguide eyepiece is designed. In one embodiment, for a red image signal, lasers having wavelengths of 630 nm, 635 nm, and 640 nm can be coupled into a waveguide eyepiece nominally designed for 635 nm. In another embodiment, a single collimated incident beam can include component beams having wavelengths of 635 nm and 642 nm. In some embodiments, the plurality of input beams can have wavelengths with a spectral width spanning approximately 5 nm, 10 nm, or 20 nm near the nominal wavelength. In some embodiments, the plurality of input beams can have wavelengths with a spectral width spanning approximately 30 nm or 50 nm near the nominal wavelength. In these embodiments, the plurality of input beams can be used to generate an increased number of output sub-beams, and these increased number of output sub-beams can increase the wavefront density for an image at the nominal wavelength. A greater number of input beams can be used to generate a greater number of output beams.

[0066] The waveguide 910 is configured to couple a collimated incident beam 920 into the waveguide 910 using a wavelength-sensitive input coupling element 912 (e.g., an input coupling grating). The wavelength-sensitive input coupling element can be a diffraction grating whose diffraction characteristics depend on the wavelength of the incident beam. The wavelength-sensitive input coupling element 912 diffracts the first beam 921 and the second beam 922 at different angles when they enter the waveguide 910. In the illustrated embodiment, the collimated incident beam is incident on the input coupling element 912 at normal incidence. However, this is not required by the present invention, and operation at other angles of incidence is also included within the scope of the present invention. The collimated incident beam diffracts at a non-normal angle of propagation inside the waveguide 910 when passing through the input coupling element 912.

[0067] The plurality of input beams in the collimated incident beam 920 are configured to propagate in the waveguide 910 along different paths in different directions in the waveguide 910 by total internal reflection (TIR). As Figure 9 shown, the first beam 921 and the second beam 922 enter the waveguide 910 at different angles. As a result, the beams 921 and 922 have different angles of incidence when reaching the surface of the waveguide 910. Therefore, each input beam passes through a different path in the waveguide, as Figure 9 shown.

[0068] After passing through the input coupling element 912 and diffracting from the input coupling element 912, the input beams 921 and 922 propagate along the waveguide 910 by total internal reflection (TIR), making multiple passes when they propagate from the end of the waveguide 510 adjacent to the input coupling element 912 towards the right end of the output coupling element 514 optically coupled to the lower surface of the waveguide 910. The waveguide 910 is characterized in that the longitudinal axis is aligned with the light propagation direction along the waveguide. In Figure 9In [the figure], the vertical axis 905 is aligned with the top and bottom surfaces of the waveguide and is perpendicular to the propagation direction of the incident light beam 920.

[0069] The waveguide 910 is also configured to output multiple sets of output light beams 930 using the output coupling element 914. As Figure 9 shown, the output coupling element 914 is coupled to the waveguide 910 on the lower surface of the waveguide, and the output coupling element 914 extends longitudinally along the waveguide 910. Since each input light beam travels through different paths in the waveguide, they reach the output coupling element 914 at different positions. At different positions, a part of each sub-beam is refracted and leaves the waveguide to form an output sub-beam, and the remaining part continues to propagate in the waveguide through TIR. Figure 9 Multiple sets of output light beams 930 are shown, including groups 950, 960, 970, and 980. Each set of output light beams includes a part of each input light beam among the multiple input light beams that propagate in the waveguide through total internal reflection. For example, the output sub-beam group 950 includes a first sub-beam 951 from a part of the incident light beam 921 and a second sub-beam 952 from a part of the incident light beam 922. Similarly, the output sub-beam group 960 includes a first sub-beam 961 from a part of the incident light beam 921 and a second sub-beam 962 from a part of the incident light beam 922. The output sub-beam group 970 includes a first sub-beam 971 from a part of the incident light beam 921 and a second sub-beam 972 from a part of the incident light beam 922. The output sub-beam group 980 includes a first sub-beam 981 from a part of the incident light beam 921 and a second sub-beam 982 from a part of the incident light beam 922.

[0070] It can be seen that the image display system 900 includes multiple input light beams with different wavelengths in the incident collimated light beam 920 and a wavelength-sensitive input coupling element 912. By using a wavelength-sensitive input coupling element, the number of output sub-beams can be increased. As a result, the wavefront sparsity or the shielding gate effect can be reduced. The wavelength-sensitive input coupling element can be a diffraction grating, and its diffraction characteristics depend on the wavelength of the incident light beam.

[0071] Figure 10A and Figure 10B are images showing the reduction of the shielding gate effect by the above optical device according to some embodiments of the present invention. To verify the function of the above image display system, an experiment was conducted, in which the incident light beam was provided by a combiner that receives light wavelengths of 635 nm and 642 nm. The image from the waveguide eyepiece was observed through a pinhole. Figure 10A Shows the shielding effect caused by wavefront sparsity. The image is shown as a sparse sampling version of the original image. Figure 10Bis an image showing the reduction of the shutter effect by providing a single collimated incident beam, the single collimated incident beam including component beams having wavelengths of 635 nm and 642 nm. In this example, for two lasers with a wavelength interval of 7 nm, there is a significant shift in the angle escaping from the pinhole, which is regarded as an additional spot in Figure 10B as shown.

[0072] As described above, since for a single-angle beam, there is a set of sub-beams that form the original wavefront, the wavefront resolution increases. However, as a second wavelength is added, there is a set of shifted sub-beams, which effectively increases the overall resolution of the wavefront corresponding to this input angle. This will improve the "shutter" or more correctly the "wavefront sparsity" problem. More improvements can be achieved by increasing the number of sub-beams with different wavelengths in the incident collimated beam. For example, lasers with wavelengths of 630 nm, 635 nm, and 640 nm can be internally coupled into a waveguide eyepiece nominally designed for 635 nm. In an embodiment of the present invention, a light source (e.g., a laser) with a spectral width of about 20 nm will significantly improve the image quality. For an eyepiece without a lens function, this provides a method of increasing the sub-beam density without relying on the substrate thickness. For an eyepiece with a lens function, the focal plane for each wavelength is slightly different, which may increase the depth of focus of the eyepiece.

[0073] Figure 11 is a simplified flowchart showing a method for displaying an image with a reduced wavefront sparsity effect or shutter effect according to an embodiment of the present invention. As Figure 11 shown, the method 1100 for displaying an image includes providing a waveguide (1110) with a wavelength-sensitive input coupling element. Referring to Figure 9 , the waveguide 910 has a wavelength-sensitive input coupling element 912. The wavelength-sensitive input coupling element can be a diffraction grating, and its diffraction characteristics depend on the wavelength of the incident beam.

[0074] The method further includes providing a collimated incident beam (1120). The collimated incident beam includes a plurality of input beams having different wavelengths. As an example, in Figure 9In this case, the collimated incident beam 920 includes a first beam 921 having a first wavelength and a second beam 922 having a second wavelength. In some embodiments, the different wavelengths are selected from a wavelength range centered on the nominal wavelength for which the waveguide eyepiece is designed. In one embodiment, for a red image signal, lasers having wavelengths of 630 nm, 635 nm, and 640 nm can be internally coupled into a waveguide eyepiece nominally designed for 635 nm. In another embodiment, a single collimated incident beam includes component beams having wavelengths of 635 nm and 642 nm. In some embodiments, the plurality of input beams can have wavelengths spanning a spectral width of approximately 20 nm. In these embodiments, the plurality of input beams can be used to generate an increased number of output sub-beams, and the increased number of output sub-beams can increase the wavefront density for an image at the nominal wavelength.

[0075] The method further includes internally coupling a plurality of input beams into the waveguide (1130) using a wavelength-sensitive input coupling element. Refer to Figure 9 , the wavelength-sensitive input coupling element 912 is configured to internally couple the collimated incident beam 920, which includes a first beam 921 having a first wavelength and a second beam 922 having a second wavelength. The wavelength-sensitive input coupling element 912 causes the first beam 921 and the second beam 922 to diffract at different angles when entering the waveguide 910.

[0076] Method 1100 further includes propagating the plurality of input beams in the waveguide by total internal reflection (1140). As Figure 9 shown, the first beam 921 and the second beam 922 enter the waveguide 910 at different angles. As a result, the beams 921 and 922 have different incident angles when reaching the surface of the waveguide 910. Therefore, each input beam travels through a different path in the waveguide, as Figure 9 shown.

[0077] The method further includes providing an output coupling element optically coupled to the waveguide (1150) and using the output coupling element to output multiple sets of output sub-beams (1160). As Figure 9 shown, the output coupling element 914 is coupled to the waveguide 910 at the surface of the waveguide and extends longitudinally along the waveguide 910. Since each input beam travels through a different path in the waveguide, they reach the output coupling element 914 at different positions, at which positions a portion of each sub-beam is refracted and exits the waveguide to form an output sub-beam, and the remaining portion continues to propagate in the waveguide by TIR. As Figure 9As shown, multiple sets of output beams 930 are emitted from the output coupling element 914. The multiple sets of output beams 930 include sets 950, 960, 970, and 980. Each set of output beams includes a portion of each of the multiple output beams that propagate in the waveguide by total internal reflection. For example, sub-beam set 950 includes a first sub-beam 951 that is a portion of incident beam 921 and a second sub-beam 952 that is a portion of incident beam 922. Similarly, sub-beam set 960 includes a first sub-beam 961 that is a portion of incident beam 921 and a second sub-beam 962 that is a portion of incident beam 922. Sub-beam set 970 includes a first sub-beam 971 that is a portion of incident beam 921 and a second sub-beam 972 that is a portion of incident beam 922. Sub-beam set 980 includes a first sub-beam 981 that is a portion of incident beam 921 and a second sub-beam 982 that is a portion of incident beam 922.

[0078] The foregoing has been described in conjunction with Figure 9 and FIG. 10 an example of an image display system implementing method 1100. By using a wavelength-sensitive input coupling element, the number of output sub-beams can be increased. The method may also include using an eye lens to focus the multiple sets of output photon beams. Additionally, the incident beam may be equipped with a fiber optic scanner. In some embodiments, the waveguide is configured for a nominal wavelength of color, and the multiple input beams have wavelengths near the nominal wavelength.

[0079] For purposes of explanation, the foregoing description uses specific terms to provide a thorough understanding of the described embodiments. However, it will be apparent to one of ordinary skill in the art that specific details are not required in order to practice the described embodiments. Thus, the foregoing description of specific embodiments is given for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise form disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in light of the above teachings.

Claims

1. A wearable display device, comprising: a pair of temple arms; a pair of main displays, wherein each of the pair of main displays includes a waveguide, and the waveguide includes a wavelength-sensitive input coupling element and an output coupling element; a pair of projector assemblies, each of the pair of projector assemblies being respectively integrated into one of the pair of temple arms, wherein each of the pair of projector assemblies includes a light source for providing a collimated incident beam, and the collimated incident beam includes a plurality of input beams having different wavelengths; and an optical device configured to receive an incident beam and provide a plurality of input sub-beams to the waveguide, wherein the optical device includes: a first prism and a second prism separated by an air gap, a first surface of the first prism and a second surface of the second prism being arranged parallel and adjacent to each other across the air gap, the first surface being partially reflective and the second surface being totally reflective; wherein the first prism and the second prism are configured to receive the incident beam and provide a first plurality of sub-beams; a third prism and a fourth prism, a third surface of the third prism and a fourth surface of the fourth prism being arranged parallel and adjacent to each other, the third surface being partially reflective and the fourth surface being totally reflective; wherein the third prism and the fourth prism are configured to receive the first plurality of sub-beams and provide the plurality of input sub-beams; and wherein the first plurality of sub-beams are spatially offset and longitudinally pass through along the waveguide, and the plurality of input sub-beams are laterally offset along the waveguide, thereby resulting in a two-dimensional array of sub-beams; wherein the waveguide is configured to: internally couple the plurality of input beams into the waveguide using the wavelength-sensitive input coupling element; propagate the plurality of input beams by total internal reflection, each input beam propagating along a different path; and output multiple sets of output photon beams using the output coupling element, wherein the multiple sets of output photon beams are continuously positioned along the waveguide along the light propagation direction, and wherein each set of output photon beams includes a part of each of the plurality of input beams propagating in the waveguide by total internal reflection.

2. The wearable display device according to claim 1, wherein, the waveguide is configured for a nominal wavelength of a color, and the plurality of input beams have wavelengths near the nominal wavelength.

3. The wearable display device according to claim 1, wherein, the collimated incident beam is provided by an optical fiber scanner.

4. The wearable display device according to claim 1, further comprising an eye lens for focusing the multiple sets of output photon beams for display.

5. The wearable display device according to claim 1, wherein, the output photon beams are spaced apart by a bounce interval of the waveguide.

6. The wearable display device according to claim 1, wherein, the wavelength-sensitive input coupling element is a diffraction grating, and its diffraction characteristics depend on the wavelength of each input beam.

7. The wearable display device according to claim 1, wherein the collimated incident beam is incident on the wavelength-sensitive input coupling element at a normal incidence.

8. The wearable display device according to claim 1, wherein the collimated incident beam is diffracted at a non-normal incidence angle of propagation within the waveguide after passing through the wavelength-sensitive input coupling element.

9. The wearable display device according to claim 1, wherein, the waveguide is characterized in that the longitudinal axis is aligned with the propagation direction of the plurality of input beams along the waveguide and is perpendicular to the propagation direction of the collimated incident beam.

10. The wearable display device according to claim 1, wherein, the waveguide includes a first surface and a second surface opposite to the first surface, the wavelength-sensitive input coupling element is disposed on the first surface, and the output coupling element is disposed on the second surface.

11. An image display system, comprising: a pair of temple arms; a pair of projector assemblies, each projector assembly of the pair of projector assemblies being respectively integrated into one of the pair of temple arms, a pair of main displays, wherein each main display of the pair of main displays includes: a waveguide; and an optical device configured to receive an incident beam and provide a plurality of input sub-beams to the waveguide, wherein the optical device includes: a first prism and a second prism separated by an air gap, a first surface of the first prism and a second surface of the second prism are disposed parallel and adjacent to each other across the air gap, the first surface is partially reflective, and the second surface is fully reflective; wherein the first prism and the second prism are configured to receive the incident beam and provide a first plurality of sub-beams; a third prism and a fourth prism, a third surface of the third prism and a fourth surface of the fourth prism are disposed parallel and adjacent to each other, the third surface is partially reflective, and the fourth surface is fully reflective; wherein the third prism and the fourth prism are configured to receive the first plurality of sub-beams and provide the plurality of input sub-beams; and wherein the first plurality of sub-beams are spatially offset and longitudinally pass through along the waveguide, and the plurality of input sub-beams are laterally offset along the waveguide, thereby resulting in a two-dimensional array of the sub-beams; wherein the waveguide is configured to: receive the plurality of input sub-beams; propagate the plurality of input sub-beams by total internal reflection; provide an output coupling element optically coupled to the waveguide; and output multiple sets of output sub-beams using the output coupling element, each set of output sub-beams including a portion of each of the plurality of input sub-beams propagating in the waveguide by total internal reflection.

12. The system according to claim 11, wherein, the plurality of input sub-beams are guided parallelly towards the waveguide.

13. The system according to claim 11, wherein, the multiple sets of output sub-beams are spaced apart by a bounce interval of the waveguide.

14. The system according to claim 11, wherein the waveguide includes a top surface, and a portion of the top surface is configured to receive the plurality of input sub-beams from the optical device.

15. A method for displaying an image, comprising: providing a wearable display device, the wearable display device including a pair of temple arms; providing a pair of projector components, each projector component of the pair of projector components being respectively integrated into one of the pair of temple arms, wherein each projector component of the pair of projector components includes a light source for providing a corresponding incident light beam; providing a pair of main displays, each main display of the pair of main displays including a waveguide and an optical device, the optical device including: a first prism and a second prism, separated by an air gap, a first surface of the first prism and a second surface of the second prism being disposed parallel and adjacent to each other across the air gap, the first surface being partially reflective and the second surface being fully reflective; and a third prism and a fourth prism, a third surface of the third prism and a fourth surface of the fourth prism being disposed parallel and adjacent to each other, the third surface being partially reflective and the fourth surface being fully reflective; for each main display of the pair of main displays, guiding the corresponding incident light beam to be incident on a part of the optical device; generating a plurality of input sub-beams using the optical device, wherein the first prism and the second prism are configured to receive the corresponding incident light beam and provide a first plurality of sub-beams; wherein the third prism and the fourth prism are configured to receive the first plurality of sub-beams and provide the plurality of input sub-beams; and wherein the first plurality of sub-beams are spatially offset and longitudinally pass through along the waveguide, and the plurality of input sub-beams are laterally offset along the waveguide, thereby resulting in a two-dimensional array of sub-beams; coupling the plurality of input sub-beams into the waveguide; propagating the plurality of input sub-beams along the waveguide by total internal reflection, wherein each of the plurality of input sub-beams passes through a different path in the waveguide; providing an output coupling element optically coupled to the waveguide; and outputting multiple sets of output sub-beams using the output coupling element, each set of output sub-beams including a part of each of the plurality of input sub-beams.

16. The method according to claim 15, wherein, the first prism includes a side surface disposed parallel to the surface of the waveguide.

17. The method according to claim 15, further comprising focusing the multiple sets of output sub-beams using an eye lens.

18. The method according to claim 15, further comprising providing the corresponding incident light beam using an optical fiber scanner.

Images