Method and system for a fiber scanning projector

Abstract

To provide a favorable method and system for a fiber scanning projector.SOLUTION: A fiber scanning projector includes a piezoelectric element, and a scanning fiber mechanically coupled to the piezoelectric element. The fiber scanning projector also includes an optical assembly section operable to receive light from the scanning fiber. The optical assembly section includes a prism element, a collimating element coupled to the prism element at an interface, a quarter wave plate, and a polarizing beam splitter disposed at the interface.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 474,461, filed March 21, 2017, entitled "Method and System for Fiber Scanning Projector," the disclosure of which is incorporated herein by reference in its entirety for all purposes. [Background technology]

[0002] Modern computing and display technology has facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images, or portions thereof, are presented to a viewer in a manner that appears or can be perceived as real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual image information without transparency to other actual, real-world visual input, while augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual image information as an augmentation to the viewer's visualization of the real world around them.

[0003] Despite the advances made in these display technologies, there remains a need in the art for improved methods and systems relating to augmented reality systems, and particularly display systems. Summary of the Invention [Means for solving the problem]

[0004] The present invention relates generally to methods and systems related to projection display systems, including wearable displays. More specifically, embodiments of the present invention provide methods and systems for volumetric displays, also known as light field displays, that create volumetric images of light at more than one depth plane. The present invention is applicable to a variety of applications in computer vision and image display systems.

[0005] According to an embodiment of the present invention, a projector is provided that includes a scanning light source defining a convex object surface and an optical assembly section operable to receive light from the scanning light source, the optical assembly section including a prism element, a collimating element coupled to the prism element at an interface, a quarter-wave plate, and a polarizing beam splitter disposed at the interface.

[0006] According to an embodiment of the present invention, there is provided a fiber scanning projector including a piezoelectric element, a scanning fiber mechanically coupled to the piezoelectric element, and an optical assembly section operable to receive light from the scanning fiber, the optical assembly section including a prism element, a collimating element coupled to the prism element at an interface, a quarter-wave plate, and a polarizing beam splitter disposed at the interface.

[0007] According to another embodiment of the present invention, a fiber scanning projector is provided. The fiber scanning projector includes a piezoelectric element and a scanning fiber passing through and mechanically coupled to the piezoelectric element. The scanning fiber emits light along an optical path. The fiber scanning projector also includes a mirror including an aperture. The scanning fiber passes through the aperture. The fiber scanning projector further includes a collimating mirror disposed along the optical path.

[0008] According to a specific embodiment of the present invention, a fiber scanning projector is provided. The fiber scanning projector includes a piezoelectric element and a scanning fiber passing through and mechanically coupled to the piezoelectric element. The scanning fiber emits light along an optical path. The fiber scanning projector also includes a first polarization-sensitive reflector disposed along the optical path, a quarter-wave plate disposed adjacent to the first polarization-sensitive reflector, and a second polarization-sensitive reflector disposed along the optical path.

[0009] Numerous advantages over conventional techniques are achieved by the methods of the present invention. For example, embodiments of the present invention provide methods and systems that can be used to display images to a user in a form factor comparable to standard eyeglasses. In some embodiments, an image projector integrated with a fiber scanning light source can fit within the frame of the eyeglasses. These and other embodiments of the present invention, along with many of their advantages and features, are described in more detail in conjunction with the following text and accompanying figures. The present specification also provides, for example, the following items: (Item 1) A projector, a scanning light source defining a convex object surface; an optical assembly section operable to receive light from the scanning light source, the optical assembly section comprising: A prismatic element; a collimating element coupled to the prism element at an interface; A quarter-wave plate, a polarizing beam splitter disposed at the interface; an optical assembly section comprising: A projector comprising: (Item 2) Item 1. The projector of item 1, wherein the scanning light source comprises a scanning waveguide source. (Item 3) Item 3. The projector of item 2, wherein the scanning waveguide source comprises a fiber scanning element including a piezoelectric actuator and a scanning fiber mechanically coupled to the piezoelectric actuator. (Item 4) Item 3. The projector of item 2, wherein the scanning waveguide source comprises a microelectromechanical system (MEMS) element including a cantilevered waveguide. (Item 5) 3. The projector of claim 2, wherein the scanning waveguide source comprises a waveguide tip operable to sweep across the convex object surface during oscillation. (Item 6) Item 1. The projector of item 1, wherein the convex object surface is approximately spherical and characterized by a radius of curvature. (Item 7) 7. The projector of claim 6, wherein the collimating element includes a reflective surface characterized by a second radius of curvature that is approximately twice the radius of curvature. (Item 8) 1. A fiber scanning projector, comprising: a piezoelectric element; and a scanning fiber mechanically coupled to the piezoelectric element; an optical assembly section operable to receive light from the scanning fiber, the optical assembly section comprising: A prismatic element; a collimating element coupled to the prism element at an interface; A quarter-wave plate, a polarizing beam splitter disposed at the interface; an optical assembly section comprising: A fiber scanning projector comprising: (Item 9) Item 9. The fiber scanning projector of item 8, wherein an output surface of the scanning fiber defines a convex object surface. (Item 10) 10. The fiber scanning projector of item 9, wherein the collimating element includes a collimating surface characterized by a radius of curvature that is approximately twice the radius of curvature of the convex object surface. (Item 11) Item 9. The fiber scanning projector of item 8, wherein the quarter wave plate is disposed between the polarizing beam splitter and the collimating surface. (Item 12) Item 9. The fiber scanning projector of item 8, wherein the prism element is optically bonded to the collimating element. (Item 13) 9. The fiber scanning projector of claim 8, wherein the scanning fiber passes through the piezoelectric element. (Item 14) Item 9. The fiber scanning projector of item 8, wherein the prism element has an input surface with a non-planar curvature. (Item 15) Item 9. The fiber scanning projector of item 8, wherein the collimating element comprises an output surface having a non-planar curvature. (Item 16) Item 9. The fiber scanning projector of item 8, further comprising a waveguide display positioned at the exit pupil of the optical assembly section. (Item 17) 1. A fiber scanning projector, comprising: a piezoelectric element; and a scanning fiber passing through and mechanically coupled to the piezoelectric element, the scanning fiber emitting light along an optical path; a mirror including an aperture through which the scanning fiber passes; a collimating mirror disposed along the optical path; A fiber scanning projector comprising: (Item 18) Item 18. A fiber scanning projector as described in item 17, wherein an output surface of the scanning fiber defines a convex object surface. (Item 19) Item 19. A fiber scanning projector as described in item 18, wherein the collimating mirror is characterized by a radius of curvature that is approximately twice the radius of curvature of the convex object surface. (Item 20) Item 18. The fiber scanning projector of item 17, wherein the collimating mirror is positioned at an angle of approximately 45° to the optical path. (Item 21) 1. A fiber scanning projector, comprising: a piezoelectric element; and a scanning fiber passing through and mechanically coupled to the piezoelectric element, the scanning fiber emitting light along an optical path; a first polarization-sensitive reflector disposed along the optical path; a quarter-wave plate positioned adjacent to the first polarization-sensitive reflector; a second polarization-sensitive reflector disposed along the optical path; and A fiber scanning projector comprising: (Item 22) 22. The fiber scanning projector of item 21, wherein the first polarization-sensitive reflector is planar and the second polarization-sensitive reflector is curved. (Item 23) Item 23. The fiber scanning projector of item 22, wherein the second polarization sensitive reflector includes an aperture, and the scanning fiber passes through the aperture. (Item 24) 22. The fiber scanning projector of claim 21, wherein the first polarization-sensitive reflector is curved and the second polarization-sensitive reflector is planar. (Item 25) Item 25. The fiber scanning projector of item 24, wherein the first polarization-sensitive reflector includes an aperture, and the scanning fiber passes through the aperture. [Brief explanation of the drawings]

[0010] [Figure 1A] FIG. 1A is a simplified perspective view illustrating a fiber scanning projector according to one embodiment of the present invention.

[0011] [Figure 1B]FIG. 1B is a simplified cutaway perspective view illustrating a fiber scanning projector according to one embodiment of the present invention.

[0012] [Figure 1C] FIG. 1C diagrammatically illustrates light paths within a viewing optical assembly (VOA) that may be used to present a digital or virtual image to a viewer, according to an embodiment of the present invention.

[0013] [Figure 1D] FIG. 1D shows a partial cross-sectional view of a waveguide scanning system using a silicon-based waveguide, according to one embodiment of the present invention.

[0014] [Figure 1E] FIG. 1E is a partial cross-sectional view illustrating the structure of an eyepiece according to one embodiment of the present invention.

[0015] [Figure 2A] FIG. 2A is a ray trace diagram illustrating the propagation of light through an optical assembly section according to one embodiment of the present invention.

[0016] [Figure 2B] FIG. 2B is a side view of an alternative optical assembly section in accordance with an alternative embodiment of the present invention.

[0017] [Figure 2C] FIG. 2C is a side view of a beamsplitter cube-based optical assembly section according to one embodiment of the present invention.

[0018] [Figure 2D] FIG. 2D is a side view of another alternative optical assembly section in accordance with an alternative embodiment of the present invention.

[0019] [Figure 2E] FIG. 2E is a side view of a multi-polarizing tilted reflector optical assembly section according to an alternative embodiment of the present invention.

[0020] [Figure 2F] FIG. 2F is a side view of an optical assembly including a Mangin mirror according to one embodiment of the present invention.

[0021] [Figure 2G] FIG. 2G is a side view of an optical assembly including a Mangin mirror according to an alternative embodiment of the present invention.

[0022] [Figure 2H] FIG. 2H is a side view of an optical assembly including a 3D printed lens, according to one embodiment of the present invention.

[0023] [Figure 3] FIG. 3 is a simplified perspective view of an optical assembly section of a fiber scanning projector according to one embodiment of the present invention.

[0024] [Figure 4] FIG. 4 is a simplified perspective view of elements of an optical assembly section during processing, according to one embodiment of the present invention.

[0025] [Figure 5] FIG. 5 is a simplified schematic diagram illustrating a fiber scanning projector 500 according to an alternative embodiment of the present invention.

[0026] [Figure 6A] FIG. 6A illustrates a fiber scanning projector according to an alternative embodiment of the present invention.

[0027] [Figure 6B] FIG. 6B is an alternative fiber scanning projector according to one embodiment of the present invention.

[0028] [Figure 6C] FIG. 6C is another alternative fiber scanning projector according to an embodiment of the present invention.

[0029] [Figure 6D] FIG. 6D is yet another alternative fiber scanning projector according to an embodiment of the present invention.

[0030] [Figure 7A] FIG. 7A is a schematic diagram illustrating a lenticular fiber tip, according to one embodiment of the present invention.

[0031] [Figure 7B] FIG. 7B is a schematic diagram illustrating a lenticular fiber tip according to another embodiment of the present invention.

[0032] [Figure 7C] FIG. 7C is a schematic diagram illustrating a lenticular fiber tip according to an alternative embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention relates generally to methods and systems related to projection display systems, including wearable displays. More specifically, embodiments of the present invention provide methods and systems for volumetric displays, also known as light field displays, that create volumetric images of light at more than one depth plane. The present invention is applicable to a variety of applications in computer vision and image display systems.

[0034] FIG. 1A is a simplified perspective view illustrating a fiber scanning projector according to one embodiment of the present invention. Fiber scanning projector 100, which may have dimensions of approximately 2 mm x 2 mm x 7 mm, includes a fiber input 110, a fiber oscillating region 120, and an optical assembly section 130. When driven by a piezoelectric actuator (not shown), the optical fiber oscillates, for example, in a helical configuration within fiber oscillating region 120 with increasing angular deflection during light projection over a given frame time. Input light to the fiber scanning projector is provided through fiber input 110, and output light from the fiber scanning projector is provided through one or more surfaces of optical assembly section 130. The various elements of the fiber scanning projector are described more fully throughout this specification.

[0035] FIG. 1B is a simplified cutaway perspective view illustrating a fiber scanning projector according to one embodiment of the present invention. In the view illustrated in FIG. 1B, fiber scanning projector 100 has been rotated horizontally. Fiber input 110 is illustrated on the right side of the figure and provides input to fiber oscillation section 120, which includes a piezoelectric actuator 150 supported by a retaining collar 152 (and driven by an electrical signal from a wire, not shown), with scanning fiber 154 disposed within mechanical enclosure 156. Optical assembly section 130 receives light from scanning fiber 154, as described more fully herein.

[0036] During operation, the scanning fiber 154, which is mechanically attached to the piezoelectric actuator 150, oscillates within the fiber oscillation region 120. In one embodiment, the piezoelectric actuator 150 includes four electrodes distributed at circumferential positions offset by 90° relative to each other. Thus, positive and negative voltages applied to either side of the piezoelectric actuator can deflect the actuator and the scanning fiber in the plane of the electrodes. By synchronously driving all four electrodes, fiber oscillation can be achieved. As light exits the scanning fiber 154, it is coupled into the optical assembly section 130, described more fully below.

[0037] As described more fully herein, small form factors comparable to standard eyeglasses are made possible by embodiments of the present invention. By utilizing embodiments of the present invention, displays with desired field of view, depth of resolution, integrated inertial motion units (IMUs), cameras, audio components, and the like are provided. In some embodiments, the fiber scanning projector 100 illustrated in FIGS. 1A and 1B is mounted within the temples or frames of eyeglasses and works in combination with eyepieces located within the frames to direct projected light toward the user's eyes. The size of the fiber scanning projector 100 allows for the integration of multiple fiber scanning projectors, which can direct light toward each eye and increase the field of view through tiling of the display area. As an example, if two projectors are used per eye, a diagonal field of view of 89° can be provided using the two projectors. Using four projectors per eye, a diagonal field of view of 134° can be achieved. In addition to the increased field of view, additional depth planes can be provided through the use of multiple projectors. Additional discussion related to tiling a display area and using multiple projectors to increase the field of view is provided in U.S. Patent Application No. __, filed March 21, 2018 (Attorney Docket No. 101782-1075069 (003410US)), the disclosure of which is incorporated herein by reference in its entirety for all purposes.

[0038] In one embodiment, fiber scanning projector 100 is fed by a fiber input 110, and fiber emitting region 120 and optical assembly section 130 are mounted within the outer edge of a frame, as illustrated in FIG. 2 of U.S. Patent Application No. __ (Attorney Docket No. 101782-1075223 (003510US)), filed March 21, 2018, the disclosure of which is incorporated herein by reference in its entirety for all purposes. The output of optical assembly section 430 is oriented to emit light toward the input coupling element of an eyepiece mounted within the frame. As an example, light from the output of the optical assembly section can be directed toward a user before coupling into the eyepiece, which may include a world-side cover glass and an eye-side cover glass.

[0039] 1C schematically illustrates the light paths within a viewing optical assembly (VOA) that may be used to present digital or virtual images to a viewer, according to one embodiment of the present invention. The VOA includes a projector 100 and an eyepiece 160 that may be worn around or in front of the viewer's eyes. As discussed herein, the VOA may be integrated with the frames of a pair of eyeglasses to present digital or virtual images to a viewer wearing those glasses.

[0040] Referring to FIG. 1C , a fiber scanning projector 100 is illustrated. However, it should be understood that other scanning light or scanning beam systems, which may be implemented as a scanning waveguide system, including, for example, a scanning waveguide source, can also be utilized in conjunction with embodiments of the present invention. Thus, while optical fiber as one implementation for guiding light is illustrated in some embodiments, the present invention is not limited to fiber scanning systems, and other waveguide scanning systems can also be utilized, according to other embodiments. Examples of other waveguide systems include microelectromechanical systems (MEMS) that integrate waveguide features, e.g., silicon waveguides integrated with cantilevered beams, into an optical scanning system. Additionally, scanning mirror systems, in which a focused beam of light is scanned by a projector to create a curved object surface, can also be utilized in conjunction with embodiments of the present invention as described herein. Additionally, scanning point sources, e.g., light-emitting diodes (LEDs) or organic LEDs (OLEDs), can also be utilized in conjunction with the optics described herein. As an example, one implementation of a MEMS-based waveguide scanner is illustrated in FIG. 1D .

[0041] 1C , optional projector relay optics can be used to direct light from fiber scanning projector 100 into eyepiece 160. Because these projector relay optics are optional, they are not required by the present invention, and other optical configurations can be utilized in accordance with embodiments of the present invention. In the illustrated embodiment, light exits the optical assembly section in a direction generally perpendicular to the longitudinal axis of mechanical enclosure 156 of fiber scanning projector 100 and is collimated, which provides a suitable input for internal coupling grating 167.

[0042] During operation, the optical fiber 154, which is mechanically attached to the piezoelectric actuator 150, oscillates within the fiber oscillation region 120. In one embodiment, the piezoelectric actuator 150 includes four electrodes distributed at circumferential positions offset by 90° relative to each other. Thus, positive and negative voltages applied to either side of the piezoelectric actuator can deflect the actuator and the scanning fiber in the plane of the electrodes. By synchronously driving all four electrodes, fiber oscillation can be achieved. As light exits the optical fiber 154 during scanning, it is coupled into the optical assembly section 130, which redirects the light toward the eyepiece 160.

[0043] Fiber scanning projector 100 can provide multiple colors, including three primary colors, red, green, and blue (RGB), to form a full-color display. Therefore, eyepiece 160 may include one or more eyepiece layers. In one embodiment, eyepiece 160 includes three eyepiece layers, one for each of the three primary colors, red, green, and blue. In another embodiment, eyepiece 160 may include six eyepiece layers, i.e., one set of eyepiece layers for each of the three primary colors configured to form a virtual image in one depth plane, and another set of eyepiece layers for each of the three primary colors configured to form a virtual image in another depth plane. In other embodiments, eyepiece 160 may include more than two eyepiece layers for each of the three primary colors for more than two different depth planes. Each eyepiece lens layer comprises a planar waveguide and may include an internal coupling grating 167, an orthogonal pupil expander (OPE) region 168, and an exit pupil expander (EPE) region 169.

[0044] Still referring to FIG. 1C , projector 100 projects image light onto an internal coupling grating 167 in eyepiece layer 160. Internal coupling grating 167 couples the image light from projector 100 into a planar waveguide, causing it to propagate in a direction toward OPE region 168. The waveguide propagates the image light horizontally by total internal reflection (TIR). OPE region 168 of eyepiece layer 160 also includes a diffractive element that couples and redirects a portion of the image light to propagate within the waveguide toward EPE region 169. EPE region 169 includes a diffractive element that couples and directs a portion of the image light propagating within the waveguide toward viewer's eye 162 in a direction generally perpendicular to the plane of eyepiece layer 160. In this manner, the image projected by projector 101 can be viewed by viewer's eye 162.

[0045] As described above, the image light generated by the projector may include light in three primary colors: blue (B), green (G), and red (R). Such image light can be separated into its constituent colors, e.g., temporally or spatially, so that the image light in each constituent color can be coupled into a separate waveguide within the eyepiece.

[0046] 1D shows a partial cross-sectional view of a waveguide scanning system using a silicon-based waveguide, according to one embodiment of the present invention. In this embodiment, rather than using a tapered optical fiber as the optical scanning element, a MEMS scanner 170 incorporating a cantilevered beam including a silicon-based cantilevered waveguide is utilized.

[0047] In the embodiment illustrated in FIG. 1D , light for viewing through the eyepiece is provided using an optical fiber (not shown) optically coupled to a waveguide 174 supported by a cantilevered beam 172. Cantilevered beam 172 extends from a support structure 176, which is mechanically attached to mechanical enclosure 156. Light from the optical fiber thus propagates down waveguide 174 and can be emitted and received by optical assembly section 130. As described more fully in connection with FIG. 2A , optical assembly section 130 includes a prism element 210 and a collimation element 220 coupled at an interface to define beamsplitter 214. As illustrated in FIG. 1D , light emitted from waveguide 174 can pass through beamsplitter 214, pass through a quarter-wave plate (not shown), and impinge on collimating surface 224. After reflection, the light passes through the quarter wave plate a second time and reflects off beam splitter 214 as illustrated by optical ray 180 .

[0048] 1D includes a transducer including a frame 180 and a hub 182 driven by a piezoelectric strip 184. The piezoelectric strips are coupled to both the frame 180 and the hub 182, which cooperate to induce oscillation of the cantilevered beam 172 in a predetermined pattern. A bracket 186 can be configured to position the cantilevered beam 172, the frame 180, and the hub 182 relative to the optical assembly section 130. Additionally, the bracket 186 can be mechanically coupled to the mechanical enclosure 156.

[0049] As illustrated in FIG. 1D , hub 182 can be configured to rotate cantilevered beam 172 into position to achieve its desired scan pattern. For example, sequential actuation of piezoelectric strips 184 can result in longitudinal expansion and contraction of the piezoelectric strips such that the hub is manipulated in a pattern that causes cantilevered beam 172, and in particular the waveguide tip, to oscillate in a spiral scan pattern. In other embodiments, hub 182 can be configured to deflect laterally and / or vertically to induce a desired scan pattern, e.g., a raster scan pattern. While hub 182 is depicted as having a circular shape, it should be understood that many other shapes, such as elliptical, rectangular, and other polygonal gap geometries, are also possible.

[0050] Cantilevered beam 172 can be formed from a length of silicon or silicon carbide. Waveguide 174, which can be a single-mode waveguide, can be formed using semiconductor processing steps that define a refractive index difference to support waveguiding. While cantilevered beam 172 is shown as including a single waveguide 174, other embodiments can implement multiple waveguides supported by the cantilevered beam. It should be understood that cantilevered beam 172 can also be utilized in conjunction with other actuators, such as piezoelectric actuator 150, described more fully herein. Thus, the frame and hub implementation illustrated in FIG. 1D is merely exemplary of structures that can be used to actuate a cantilevered beam.

[0051] Figure 1E is a partial cross-sectional view illustrating the structure of an eyepiece according to one embodiment of the present invention. The area shown in the cross-section includes the area of ​​an internal coupling diffractive optical element (e.g., an internal coupling grating) of eyepiece 800. As shown in Figure 1E, eyepiece 800 includes a stack of waveguide plates 820, 830, and 840 that receive input light from a fiber scanning projector and output image information to a viewer's eye 802. Eyepiece 800 illustrated in Figure 1E includes an eye-side cover layer 810 positioned on the side of the eyepiece adjacent to the viewer's eye and a world-side cover layer 850 positioned on the side of the eyepiece facing toward the world.

[0052] In some embodiments, waveguide plates 820, 830, and 840 include individual planar waveguides 822, 832, or 842 for propagating light in the plane of their respective waveguide plates 820, 830, and 840. Each planar waveguide 822, 832, or 842 has a back surface facing the viewer's eye and a front surface facing the world. In the embodiment illustrated in FIG. 1E, waveguide plates 820, 830, and 840 also include individual gratings 824, 834, or 844 disposed on the back surface of their respective waveguides 822, 832, or 842 for coupling and redirecting a portion of the light for propagation within their respective waveguides 822, 832, or 842.

[0053] In the illustrated embodiment, each waveguide 822, 832, or 842 and each grating 824, 834, or 844 may be wavelength-selective so as to selectively propagate or redirect light over a given wavelength range. In some embodiments, waveguide plates 820, 830, and 840 may each be configured for a separate primary color. For example, waveguide plate 820 is configured for red (R) light, waveguide plate 830 is configured for green (G) light, and waveguide plate 840 is configured for blue (B) light. It should be understood that eyepiece 800 may include two or more waveguide plates for red light, two or more waveguide plates for green light, and two or more waveguide plates for blue light for different depth planes, as described above. In some other embodiments, other colors, including magenta and cyan, may be used in addition to or replace one or more of red, green, or blue.

[0054] To improve optical efficiency, some embodiments utilize a reflective surface, such as a metallized surface, on one of the surfaces (e.g., the front surface) of the eye-side cover layer to provide a highly reflective surface (e.g., an approximately 100% reflective coating), which reflects the input light (which may be RGB light that passes through the input coupling element and makes a second pass through the input coupling element to improve image brightness) by forming a reflective structure behind the input coupling element (e.g., a vertically aligned internal coupling grating). As shown in FIG. 1E, a reflector 812 reflects input light 801 incident from the fiber scanning projector that is not coupled into the waveguide. After reflecting from the reflector 812, the input light can make a second pass through the input coupling element to increase the amount of light coupled into the waveguide.

[0055] In an alternative embodiment, an annular reflector 852, fabricated using, for example, a 100% reflective metal coating, can be placed on the world-side cover glass. While this annular reflector 852 is shown on the back side of the world-side cover layer 850, this is not required by the present invention and may alternatively be mounted on the front side. Those skilled in the art will recognize many variations, modifications, and alternatives. In this alternative embodiment, input light 801 from the fiber scanning projector passes through the center of the annular reflector 852 after being output from the optical assembly section of the fiber scanning projector. Because the input light is diverging, the beam diffuses as it passes through the eyepiece and reflects off the reflector 812 behind the input coupling element. This reflected light 804 propagates back through the eyepiece, and the cone of light expands during propagation. In some embodiments, reflected light 804 is also coupled into the internal coupling grating during the return path, characterized by the same orientation as the input beam for display to the viewer; however, the reflected light 804 is a mirror image of the input light 801, and entry through the other side of the internal coupling grating results in the same orientation. A substantial portion, possibly a large portion of the light, can reflect off the annular reflector 852 on the world-side cover layer, as illustrated by doubly reflected light 806, and make a third pass through the input coupling element, resulting in additional coupling of light into the waveguide plate. As will be apparent to those skilled in the art, a hall of mirrors effect can be achieved, resulting in increased brightness correlated with an increased number of light rays passing through the eyepiece, improving fill factor and image quality.

[0056] Channels can be cut in the temples and frame to accommodate the fiber and electrical wiring. Because the fiber / wire passes over the spring hinge, the design dimensions allow the fiber to not bend beyond a minimum bend radius as the temples are folded.

[0057] In addition to the reflective structure associated with the input coupling element discussed in connection with FIG. 1E, some embodiments utilize a partially reflective (e.g., 50% aluminized) surface on the inside surface of the world-side cover glass so that a portion (e.g., half) of the light propagating from the eyepiece toward the world is reflected and directed back toward the user's eye, which results in a slight lateral offset to the beam, increasing overall brightness, increasing beam density, and contributing to an improved fill factor.

[0058] FIG. 2A is a ray trace diagram illustrating the propagation of light through an optical assembly section according to one embodiment of the present invention. The optical assembly section 130 includes a prism element 210 and a collimation element 220 that are coupled at an interface. In one embodiment, the prism element and the collimation element are optically joined at the interface. As described more fully herein, one or more of the surfaces of the optical assembly section 130 may include optical power. Thus, while light collimation is discussed herein in terms of the collimating surface 224, it should be understood that surfaces other than the collimating surface 224 may also contribute to the collimation of light by the system. The scanning fiber 154 within the fiber oscillating region 120 is shown in three scanning positions: on-axis 230 (solid line), right off-axis 232 (dashed line), and left off-axis 234 (dashed line). As shown in FIG. 2A , as the tip of the scanning fiber 152 oscillates, it sweeps through a substantially spherical surface, illustrated by curve 240 in FIG. 2A , resulting in a convex surface being imaged, such that curve 240 may be referred to as a convex object surface. Conventional lenses are typically designed for flat or concave object surfaces. Embodiments of the present invention utilize a design in which the convex object surface 240 associated with the tip of the scanning fiber 152 is matched with a concave collimating surface 224, which may be a substantially spherical mirror having roughly twice the radius of curvature of the convex object surface 240. Thus, in some embodiments, the majority of the focusing is achieved using the convex collimating surface 224, which may be implemented as a curved mirror with an aspheric correction term. While refractive and reflective elements are illustrated in FIG. 2A , embodiments of the present invention are not limited to these implementations; diffractive surfaces, metasurfaces, and the like may also be utilized in accordance with embodiments of the present invention. For example, rather than being a reflective surface, collimating surface 224 can be a diffractive surface, metasurface, or the like. One or more of the other surfaces illustrated in FIG. 2A can also be implemented using diffractive structures or a combination of diffractive and / or refractive structures. Examples would be diffractive structures to compensate for chromatic aberration and refractive structures to focus / defocus the beam.One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0059] In addition to scanning fibers, other optical systems can also be utilized to create the convex object surface 240. Examples of these optical systems include MEMS-based scanning systems, scanning mirror systems with converging beams, scanning point sources, other waveguide scanning systems including flat panel displays combined with optics to create curved object surfaces, or the like.

[0060] Embodiments of the present invention allow the optical prescriptions of the various optical surfaces to be varied to optimize size, exit pupil diameter, combined optical power, linear expansion, angular expansion, distance between the exit pupil and output surface, and the like. Controlling the curvature of the input surface 212, collimating surface 224, and output surface 226 allows various properties of the output beam to be controlled, including beam diameter, angular expansion of the angle associated with the fiber deflection (i.e., the angle between scan positions 232 and 234), and the like. Note that in some implementations, the beam splitter 214 can include curvatures such that it is not a planar surface, thereby providing additional design freedom. This non-planar shape (i.e., non-planar curvature) can include curvatures (e.g., concave or convex) to introduce optical power, compensate for aberrations, or the like. Additionally, the refractive index of the material used to fabricate the optical assembly section 130 can also be adjusted to modify the optical properties discussed above. Additionally, beam splitter 214 can be a partially reflective (50 / 50 split) surface, a polarizing beam splitter, a wavelength selective beam splitter, or the like.

[0061] Referring to FIG. 2A , multiplexing functionality can be implemented when polarizing beam splitter 214 alternately passes and reflects incident light with variable polarization, e.g., as a function of time. A shutter integrated into the optical path between the partially reflective surface / polarizing beam splitter and collimating surface 224 / surface 227 can be utilized to multiplex between the two optical paths. Thus, some embodiments provide a multiplexed display with a high-resolution narrow field-of-view image surrounded by a lower-resolution wide field-of-view image. In some embodiments, surface 227 can be absorptive, providing a shutter effect when light is reflected from polarizing beam splitter 214 toward surface 227. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0062] Referring again to FIG. 2A , scanning fiber 154 acts as a point light source, emitting a cone of light. These cones of light, as shown, propagate from convex object surface 240 through optical assembly section 130. As the scanning fiber sweeps through an oscillating pattern, different pixels are illuminated, forming the desired image. In the embodiment illustrated in FIG. 2A , light from the scanning fiber enters optical assembly section 130 through input surface 212 and is polarized such that it will pass through polarizing beam splitter 214, pass through quarter-wave plate 222, and impinge on collimating surface 224 with little or no reflection. After reflection, the light passes through quarter-wave plate 222 a second time and reflects from polarizing beam splitter 214 toward output surface 226. An exit pupil 228 is formed outside optical assembly section 130 for delivery to the eyepiece. As will be apparent to those skilled in the art, for many optical systems, alignment between the exit pupil and the input plane of another optical system is preferred. Thus, the working distance between output surface 226 and exit pupil 228 allows embodiments of the present invention to be utilized in conjunction with a variety of optical systems. As an example, if the light emitted by a fiber scanning projector is utilized by a waveguide-based optical system, the input coupling element of the waveguide-based optical system may be located in line with, e.g., the same plane as, exit pupil 228. In some embodiments, exit pupil 228, which provides a location where a small diameter beam is formed, can enable efficient coupling into a small input coupling element, which is matched in size to the exit pupil, thereby efficiently utilizing the area of ​​the waveguide-based optical system. As illustrated in FIG. 2A, the three cones of light emitted at each of the three illustrated locations 230, 232, and 234 of the scanning fiber 154 are collimated as they exit the optical assembly section, as shown, for example, by collimated rays 231 and 233 that define the edges of the cone of light emitted at on-axis location 230.

[0063] In another specific embodiment, the polarizing beam splitter can be replaced with a wavelength-selective beam splitter so that one or more colors will pass through the beam splitter while other colors are reflected toward surface 227, which may be implemented as a surface with refractive power. This wavelength selectivity would enable focusing through the use of diffractive elements or metasurfaces, as diffractive optics is used instead of refractive optics. Accordingly, embodiments of the present invention integrate metasurfaces onto one or more of input surface 212, collimating surface 224, surface 227, and / or output surface 226, and multiple lens functions can be encoded into the metasurface for wavelength-selective optical processing, other diffractive optical functions, dispersion compensation, or the like. In some designs, dispersion compensation is provided by various surfaces; for example, dispersion compensation can be implemented by correcting aberrations occurring at the input surface with aberration correction provided on the output surface.

[0064] 2B, a quarter-wave plate can also be fabricated by vacuum forming onto the collimated surface 224. In this implementation, after the quarter-wave plate is formed on the curved surface, a metallized or other suitable reflective surface can be formed to complete the fabrication of the collimated surface.

[0065] In some embodiments, the input surface 212, collimating surface 224, and output surface 226 of the optical assembly section 130 can have optical power to compensate for spherical aberration and provide an increased field of view. Therefore, using a smaller deflection of the optical fiber within the fiber emission region leads to a larger field of view. As an example, the input surface 212 can be convex and provide positive optical power for the input light, the collimating surface 224 can be concave and provide negative optical power for the light from the input surface, and the output surface can be convex and provide negative optical power for the light from the beamsplitter. The collimating surface 224 is generally spherical, but in some implementations includes an aspherical curvature. The aspherical curvature can correct spherical aberration, and the overall curvature can result in collimation of light by the collimating surface. The collimating surface 224 can be processed as a reflective element through the deposition of one or more reflective coatings, metallized coatings, or the like.

[0066] Collimating surface 224, which in some embodiments may also be referred to as a curved object surface, may have a radius of curvature that is approximately twice that of convex object surface 240, although this is not required by the present invention, and it should be noted that input surface 212 and output surface 226 may incorporate refractive power in addition to that present in collimating surface 224. Thus, because additional refractive power is implemented through input surface 212 and output surface 226, the curvature of collimating surface 224 may deviate from twice the curvature of convex object surface 240. Additionally, as discussed herein, aspheric components may be integrated into optical surfaces, including input surface 212, collimating surface 224, and output surface 226.

[0067] In an exemplary fabrication process, the optical assembly section 130 is fabricated by bonding three elements together. In this process, the first element is a prism element 210, and the second element is a collimating optical section 220 that is bonded to the prism element. The prism element 220 receives light through an input surface 212. A polarizing beam splitter 214 is formed at the interface between the prism element 210 and the collimating optical section 220. In some embodiments, a polarization-selective coating is applied to the longest surface of the prism prior to bonding to form the polarizing beam splitter. A quarter-wave plate 222 is formed on the back surface of the collimating optical section 220, and a third element comprising a curved reflective optic 221 is bonded to the quarter-wave plate. As described herein, the curved reflective optic 221 includes a collimating surface 224, which can be metalized or otherwise coated to provide high reflectivity.

[0068] During operation, with polarized light at the input, a majority of the polarized input light passes through polarizing beam splitter 214 a first time, passes through quarter-wave plate 222, is reflected and collimated by collimating surface 224, passes through quarter-wave plate 222 a second time (now with an orthogonal polarization state), and is substantially reflected from the polarizing beam splitter towards output surface 226.

[0069] FIG. 2B is a side view of an alternative optical assembly section according to an alternative embodiment of the present invention. Referring to FIGS. 2A and 2B, the collimating optical section 220 and curved reflecting optic 221 illustrated in FIG. 2A are combined into a single (i.e., monolithic) collimating reflector 251 to form alternative optical section 250. Reflecting surface 252 includes a wave plate that introduces a half-wave of phase shift upon reflection. In one implementation, a quarter-wave plate is formed on the right edge of collimating reflector 251 before forming reflecting surface 252, for example, by depositing a metal film, a dielectric film, or the like. In other embodiments, microstructures can be utilized to introduce a half-wave of phase shift upon reflection. Therefore, alternative optical section 250 is not limited to a specific manner of implementing phase delay and reflection. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0070] 2C is a side view of a beamsplitter cube-based optical assembly section according to one embodiment of the present invention. Beamsplitter cube 261 is utilized as the base of beamsplitter cube-based optical assembly section 260, with additional optical elements 262, 263, and 264 molded onto the outer surfaces of beamsplitter cube 261 to form the input, collimating, and output surfaces, respectively. In this embodiment, a quarter-wave plate can be implemented as the intersection of beamsplitter cube 261 and optical element 263, which forms the collimating surface. In an alternative embodiment, surface 266 defines the collimating surface of optical element 263 and can be used to provide alignment between the edge of optical element 263 and surface 267 of optical element 264. Note that in this alternative embodiment, optical element 263 can be trimmed at the periphery to form an element with a non-circular plan view, including a rectangular plan view. Thus, optical element 263 has a trimmed surface or edge that aligns with surface 268 of beamsplitter cube 261. This alignment between the edges of the various elements can facilitate alignment during manufacturing, including bonding of the various elements. The use of glass beamsplitter cube 261 offers advantages, including the selection of polarization-selective coatings used to fabricate beamsplitter surface 265. Additionally, manufacturability is enhanced with this design due to the wide availability of glass beamsplitter cubes, including small beamsplitters. In other embodiments, beamsplitters of materials other than glass, including plastic, are utilized. In addition to forming optical elements (e.g., refractive and reflective optical elements) through casting, other techniques can also be utilized to achieve optical effects, including molded elements, conventionally machined optics, the use of diffractive surfaces and / or metasurfaces, and the like.

[0071] 2D is a side view of another alternative optical assembly section in accordance with an alternative embodiment of the present invention. In the alternative embodiment of optical assembly section 270 illustrated in FIG. 2D , the polarization-selective coating utilized for the polarizing beam splitter is eliminated, along with the quarter-wave plate. In this alternative embodiment, a partially reflective surface 271 (e.g., a 50 / 50 reflector) joins prism element 272 to collimating element 273. Half of the light incident from input surface 212 passes to collimating surface 224 and is reflected toward partially reflective surface 271, which joins prism element 272 and collimating element 273. The other half of the light is reflected toward reflective surface 274, which, in this alternative embodiment, may have the same curvature as collimating surface 224. As a result, the light reflected from the collimating surface and the light reflected from reflective surface 274 are collimated (subject to the optical power of output surface 226). The embodiment illustrated in Figure 2D can improve optical efficiency because light reflected from reflective surface 274 is available for output from the optical assembly section. In some embodiments, a single exit pupil, discussed in relation to Figure 2E as a superimposed exit pupil, is shared by light reflecting from collimating surface 224 and light reflecting from reflective surface 274.

[0072] Utilizing this design, different refractive powers can be achieved using collimating surface 224 and reflective surface 274, which have different curvatures, resulting in zoom-in / out views, wide / narrow fields of view, and the like, as light is directed in a multiplexed manner to each of these surfaces. As an example, the reflectivity of partially reflective surface 271 can be varied to provide time-based multiplexing.

[0073] Because partially reflective surface 271 has variable reflectivity and can alternately pass and reflect incident light, multiplexing functionality can be implemented. A shutter integrated into the optical path portion between partially reflective surface 271 and collimating surface 224 / reflective surface 274 can be utilized to multiplex between the two optical paths. Thus, some embodiments provide a multiplexed display with a high-resolution narrow field-of-view image surrounded by a lower-resolution wide field-of-view image. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0074] In another implementation, a tiled image can be formed by tilting partially reflective surface 271 at an angle other than 45° relative to the incident light. Light passing through partially reflective surface 271 will be directed in a first direction after reflecting from collimating surface 224 and passing through output surface 226. Light reflecting from partially reflective surface 271 will be directed in a second direction after reflecting from reflective surface 274 and passing through output surface 226. Thus, light reflected from collimating surface 224 may be tilted to the left after passing through output surface 226, and light reflected from reflective surface 274 may be tilted to the right after passing through output surface 226, thus providing inputs directed to different portions of the image field for a tiled display implementation.

[0075] Figure 2E is a side view of a multi-polarizing tilting reflector optical assembly section according to an alternative embodiment of the present invention. Polarization-sensitive material forms polarizing beam splitter 283, similar to polarizing beam splitter 214 in Figure 2A, at the interface of prism element 284 and collimating element 285. In this implementation, input light from a fiber scanning projector may have two signals encoded with different polarizations. A first input beam 286 encoded with a first polarization may pass through the polarization-sensitive material of polarizing beam splitter 283 and reflect from collimating surface 224. This beam will form exit pupil 281. A second input beam 287 encoded with a second polarization will reflect from the polarization-sensitive material of polarizing beam splitter 283 and reflect from reflective surface 289. This beam will form exit pupil 282. The interface between prism element 284 and collimating element 285 is tilted at an angle other than 45° relative to the input beam, so that exit pupils 281 and 282 can be spatially offset. As an example, if polarizing beam splitter 283 is color-selective, the exit pupil associated with a first color (e.g., green) can be positioned adjacent to the exit pupil associated with a second color (e.g., red) so that the exit pupils can provide spatially separated beams for input to the eyepieces. As shown in FIG. 2E, in addition to spatial separation in the z-direction, the exit pupils can be spatially separated in the x- or y-directions.

[0076] Thus, two overlapping images can be created, or, as illustrated in FIG. 2E , two spatially separated images can be formed within the image field using inclined surfaces at the interface of the prism element 284 and the collimating element 285. Thus, two laterally separated exit pupils can be provided, which can provide inputs for two input coupling elements on a waveguide display. As discussed herein, the curvatures of the collimating surface 224 and the reflective surface 289 can be different. For example, in a wavelength-selective implementation, a wavelength-selective beam splitter can be used that will pass a first color and reflect it off the collimating surface 224. The second color will reflect off the polarizing beam splitter and then reflect off the reflective surface 289, thereby creating a beam having the second color that either diverges or converges after reflecting off the reflective surface 289. This may allow spatial separation between two different color channels, for example, for subsequent coupling into two different internal coupling gratings, each associated with a different waveguide layer of the eyepiece. Additionally, these designs may be extended to multi-depth plane implementations, where multiple beams in each color are utilized to provide M beams of N colors, for example, for coupling into M×N waveguides. Quarter-wave plate integration may be implemented in polarization-sensitive implementations. Consequently, polarization-selective reflectors may be implemented in conjunction with pupil spatial separation, allowing routing of one color to a first depth plane and a second color to a second depth plane. Thus, both wavelength and polarization separation are within the scope of the present invention.

[0077] In other embodiments, the exit pupils may be co-located (i.e., overlapping). Thus, the illustration of spatially separated pupils in Figure 2E is merely an example and should not be understood as limiting embodiments of the present invention. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0078] One or more of the optical surfaces discussed in connection with FIGS. 2A-2E can be variable-focus, and the focus can be controlled in conjunction with the input from the fiber scanning projector. Thus, light rays injected into the optical assembly section at different angles can experience different refractive powers. In this embodiment, a multi-focal display can be implemented as a function of the angle of view. Furthermore, additional optical elements can be integrated with the structures described herein, for example, between the output surface and one or more exit pupils or optically downstream of one or more exit pupils. These additional optical elements, which may include relay optics, can have variable refractive power, for example, a variable-focus lens positioned between the output surface and one or more exit pupils. Thus, collimated beams can be focused, aberrations can be corrected, other optical effects can be implemented, or the like. In some embodiments, the shape of the convex object surface 240 can vary from spherical, and variable-focus surfaces or additional optical elements can be utilized as needed for the curvature of the convex object surface. Various materials can be utilized to fabricate the structures illustrated herein, including materials that vary their refractive index as a function of an applied bias, including liquid crystal lenses, electro-optic polymers, lithium niobate, and the like. Because fiber scanning projectors can be scanned at high frequencies, optical materials that can vary their optical properties at high frequencies are suitable for use in various embodiments. As an example, optical structures that can rapidly modulate focal length can cooperate with fiber scanning projectors to vary the focus line-by-line or pixel-by-pixel. These materials can be utilized in conjunction with the input and / or output surfaces of the optical assembly section and in conjunction with the collimating surface 224. As an example, a deformable mirror can be integrated as an element of the collimating surface 224 or as a replacement for the reflective surface 224. Such deformable mirrors, operating at multi-kilohertz rates and above, can provide variable focus operation line-by-line or pixel-by-pixel, as needed for a particular application.

[0079] The maximum distance that prism element 284 extends in the z-direction, marked by point A in FIG. 2E, can vary according to the particular implementation. As illustrated in FIG. 2E, point A is the intersection of the right side of collimating element 285 and the bottom of prism element 284. The design illustrated in FIG. 2E enables a wide field of view as the tip of the scanning fiber sweeps through the approximately spherical surface, illustrated by curve 240 in FIG. 2A. In other embodiments, the surface of prism element 284, which forms the upper right side of the prism element, is tilted so that point A is moved to a reduced value in the z-direction. Similarly, point B is moved to a greater value in the x-direction as the left side of prism element 284 is extended and the left side of collimating element 285 is reduced. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0080] 2F is a side view of an optical assembly including a Mangin mirror, according to one embodiment of the present invention. Similar to one or more of the designs discussed above, a beamsplitter cube 261 is utilized as the base of a beamsplitter cube-based optical assembly section 290. A quarter-wave plate 291 is implemented at the intersection of the beamsplitter cube 261 and the Mangin mirror 292, which provides collimation of the input beam. In the illustrated embodiment, the output lens 293 is implemented as an achromatic doublet, although other lens configurations can be utilized in accordance with embodiments of the present invention.

[0081] 2G is a side view of an optical assembly including a Mangin mirror according to an alternative embodiment of the present invention. In the embodiment illustrated in FIG. 2G, a beamsplitter cube 261 is utilized as the base of a beamsplitter cube-based optical assembly section 294. A quarter-wave plate 291 is implemented at the intersection of the beamsplitter cube 261 and the Mangin mirror 292, which provides collimation of the input beam. In the illustrated embodiment, the output lens 295 is implemented as a molded glass lens, although other lens configurations can also be utilized according to embodiments of the present invention.

[0082] FIG. 2H is a side view of an optical assembly including a 3D-printed lens, according to one embodiment of the present invention. Similar to one or more of the designs discussed above, a beamsplitter cube 261 and a quarter-wave plate 291 are utilized within the optical assembly section 296. An input lens 299 and an output lens 295, which may be molded glass lenses, are utilized in this embodiment. A collimating optic, also referred to as a printed lens, is formed using 3D printing, also referred to as additive manufacturing. The collimating optic includes a substrate 297 that supports a printed lens 298, e.g., a polymer lens formed with a curvature associated with a Mangin lens. The substrate 297 is bonded to the quarter-wave plate 297 using, for example, an optical adhesive.

[0083] It should be noted that any of the characteristics of any of the elements and surfaces discussed with or illustrated in reference to Figures 2A-2H may be applied to the implementations provided in any of the other implementations illustrated in Figures 2A-2H, as appropriate. By way of example only, surface curvature, reflective or diffractive properties of surfaces, polarization properties, and the like, may be applied to any of the implementations, as appropriate.

[0084] 3 is a simplified perspective view of the optical assembly section of a fiber scanning projector, according to one embodiment of the present invention. Optical assembly section 130 includes a prism element 210 to a collimating element 220. Light enters on an input surface (not shown, facing left rear) and propagates toward a polarizing beam splitter 214. The edges of a quarter-wave plate 222, a collimating surface 224, and an output surface 226 are also shown in this view.

[0085] In some embodiments, the fiber scanning projector can achieve a 4x3 aspect ratio with 3 arcminute resolution and a 50° diagonal field of view, although these specific parameters are not required by the present invention. In some implementations, a 60° x 30° elliptical field of view is achieved. In another embodiment, the fiber scanning projector can achieve a 4x3 aspect ratio with 2 arcminute resolution and a 50° diagonal field of view. In yet another embodiment, the fiber scanning projector can achieve 1 arcminute resolution or less. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0086] To reduce the size and weight of the fiber scanning projector, the non-light-bearing parts can be trimmed to form a wedge-shaped structure, which also increases packaging flexibility, especially for integration with eyeglasses with curved frames.

[0087] Figure 4 is a simplified perspective view of elements of an optical assembly section during processing, according to one embodiment of the present invention. As illustrated in Figure 4, a first element 410 of the optical assembly section includes a collimating optical section 412, which includes the propagation path of light after passing through a beam splitter, a collimating surface 224, and an output surface 226. A second element 420 of the optical assembly section includes a prism surface 412 on which a polarizing beam splitter may be formed. In this perspective view, the input surface is not shown, as it faces left and rear. A matching feature 430 is integrated into the material and is designed to mate with a corresponding matching feature (not shown) on the bottom left surface of the first element.

[0088] In some embodiments, the second element 420 is fabricated from a glass material, as glass materials may be more suitable for deposition of polarization-selective coatings than some plastic materials, facilitating the formation of a polarizing beam splitter at the interface between the first and second elements.

[0089] Figure 5 is a simplified schematic diagram illustrating a fiber scanning projector 500 in accordance with an alternative embodiment of the present invention. As shown in Figure 5, a scanning fiber 510 passes through an aperture 522 in a mirror 520. The scanning fiber is shown at the end of its range of motion. A collimating mirror 530 reflects light emitted by the scanning fiber, which is then reflected from mirror 520 to provide an output beam 540. In some embodiments, the radius of curvature of collimating mirror 530 is twice the radius of curvature of spherical object surface 512.

[0090] As discussed in connection with the fiber scanning projector, as the scanning fiber 510 is actuated by the piezoelectric element 514, it sweeps a substantially spherical surface 512, also referred to as the spherical object surface. Thus, after reflecting off a substantially spherical reflector having twice the radius of curvature of the surface swept by the scanning fiber, light emitted from any point along the surface swept by the scanning fiber will be well collimated after reflecting off the substantially spherical reflector.

[0091] Because the base of the fiber scanner is adjacent to the piezoelectric element 514, the deflection of the scanning fiber 510 at the aperture 522 is small, but the deflection at the tip of the scanning fiber is large (e.g., about 20 degrees). As the beam is emitted from the tip of the scanning fiber, it expands, forming a cone of light 516, as shown in Figure 5. Collimation of the cone by the approximately spherical reflector 530 provides a beam with a diameter much larger than the diameter of the scanning fiber, such that most of the reflected light is reflected from the mirror 520 with little light passing through the aperture 522 in the return path.

[0092] In some implementations, the field of view of the fiber scanning projector 500 is a function of the segment of arc traversed by the scanning fiber 510 during oscillation. As an example, if the scanning fiber sweeps through 20 degrees, the projector's field of view is approximately 20 degrees. Increasing the field of view can be accomplished by increasing the range of fiber oscillation. In other embodiments, an increase in the effective field of view can be used to increase the field of view independent of the range of fiber oscillation. Comparing the fiber scanning projectors in FIGS. 2 and 5 , the field of view associated with the fiber scanning projector 500 is maintained as a result of collimation resulting from reflection from the reflector 530, while the optical assembly section 130 provides the illustrated optical surfaces that can be used to introduce magnification that can increase the field of view created by the projector. As an example, modifying the curvature of the output surface 226 can be utilized to increase the field of view.

[0093] As illustrated herein, embodiments of the present invention utilize a design that is related through the use of a spherical object plane and a corresponding reflector that has a curvature that is approximately twice the curvature of the spherical object plane.

[0094] 6A illustrates a fiber scanning projector according to an alternative embodiment of the present invention. The fiber scanning projector 600 in FIG. 6A includes a scanning fiber 610 that passes through and is mechanically coupled to a piezoelectric element 605, a first polarization-sensitive reflector 620, and a second polarization-sensitive reflector 630. A quarter-wave plate 622 is integrated with the first polarization-sensitive reflector.

[0095] In operation, light emitted by the scanning fiber 610 has a polarization that passes through the first polarization-sensitive reflector 620 and the quarter-wave plate 622. The second polarization-sensitive reflector 630 reflects the incident light, which passes through the quarter-wave plate 622 a second time, such that the light's polarization is now oriented in an orthogonal direction and is reflected from the first polarization-sensitive reflector 620. After reflecting from the first polarization-sensitive reflector 620, the light passes through the second polarization-sensitive reflector 630 as output beam 640. As shown in FIG. 6A , the second polarization-sensitive reflector 630 is curved with a curvature that collimates the light emitted by the scanning fiber 610. As a result, the diverging input beam is converted to a collimated output beam.

[0096] 6A are separated by air gaps, e.g., first polarization-sensitive reflector 620 and second polarization-sensitive reflector 630 are shown as separated by air gap G, but this is not required by the present invention. As an example, a solid stacked component can be utilized that includes a first polarization-selective reflector, a quarter-wave plate, and a second polarization-selective reflector, receives light from a scanning fiber, transmits the light to a stacked curved reflector, performs polarization rotation, and then reflects the light from the first polarization-selective reflector. Thus, a solid element, which may also include optical power, can be utilized to provide focusing / defocusing of light and aberration correction.

[0097] Figure 6B is an alternative fiber scanning projector according to one embodiment of the present invention. The fiber scanning projector 601 illustrated in Figure 6A shares some similarities with the fiber scanning projector 600 illustrated in Figure 6A, and the description provided in connection with Figure 6A is applicable, where appropriate, to the fiber scanning projector 601 illustrated in Figure 6B.

[0098] 6B, fiber scanning projector 601 includes a scanning fiber 610, a first polarization-sensitive reflector 621 that is curved to provide collimation, and a substantially planar second polarization-sensitive reflector 631. A quarter-wave plate is integrated with the first polarization-sensitive reflector.

[0099] In operation, light emitted by scanning fiber 610 has a polarization that passes through first polarization-sensitive reflector 621 and a quarter-wave plate. Second polarization-sensitive reflector 631 reflects the incident light, which passes through the quarter-wave plate a second time, resulting in the light's polarization now being oriented in an orthogonal direction and being reflected from first polarization-sensitive reflector 621. After reflecting from first polarization-sensitive reflector 621, which collimates the light during reflection, the light passes through second polarization-sensitive reflector 631 as output beam 640. Comparing Figures 6A and 6B, the folded optical path illustrated in Figure 6A can be replaced with a potentially shorter optical path with the common feature of collimation, as illustrated in Figure 6B.

[0100] Figure 6C is another alternative fiber scanning projector according to an embodiment of the present invention. The fiber scanning projector 602 illustrated in Figure 6C shares some similarities with the fiber scanning projector 500 illustrated in Figure 5 and the fiber scanning projector 600 illustrated in Figure 6A, and the description provided in connection with Figures 5 and 6A is applicable to the fiber scanning projector 602 illustrated in Figure 6C, where appropriate.

[0101] In the embodiment illustrated in Figure 6C, scanning fiber 610 passes through an aperture 652 in curved mirror 650. A polarization-selective reflector 654 reflects the light toward curved mirror 650 during the first pass. By integrating a quarter-wave plate into the optical path, the light, after reflection and collimation from curved mirror 650, passes through polarization-selective reflector 654 during the second pass. The embodiment illustrated in Figure 6C enables a compact configuration in a hybrid design.

[0102] As illustrated by optional lens 656, embodiments of the present invention allow additional optical elements to be placed at a significant distance from the elements that make up the fiber scanning projector. In this example, the distance D between the surface of polarization-selective reflector 654 and lens 656 provides a suitable working distance for inserting, for example, a field magnifier. Additionally, a spherical aberration corrector can be inserted given the suitable extended working distance provided by this embodiment.

[0103] Figure 6D is yet another alternative fiber scanning projector according to an embodiment of the present invention. The fiber scanning projector illustrated in Figure 6D shares some similarities with the fiber scanning projector 500 illustrated in Figure 5 and the fiber scanning projector illustrated in Figure 6A, and the description provided in connection with Figures 5 and 6A is applicable, where appropriate, to the fiber scanning projector 603 illustrated in Figure 6D.

[0104] 6D , scanning fiber 610 passes through an aperture 662 in a flat mirror 660. A curved polarization-selective reflector 664 reflects the light toward the flat mirror 660 during the first pass. By integrating a quarter-wave plate into the optical path, the light reflects from the curved polarization-selective reflector 664 and the flat mirror 660, thereby collimating it before passing through the curved polarization-selective reflector 664 during the second pass. The embodiment illustrated in FIG. 6D also enables a compact configuration in a hybrid design.

[0105] FIG. 7A is a schematic diagram illustrating a lensed fiber tip according to an embodiment of the present invention. As illustrated in FIG. 7A, an optical fiber 710 includes a cladding 712 and a fiber core 714. The optical fiber can be considered a point source, emitting light rays along an emission cone 716. In the embodiment illustrated in FIG. 7A, the point source is shown as being longitudinally embedded within the core. A shallow lens surface 718 can be applied to the end of the optical fiber, as shown. The lens surface 718 can be machined in a variety of different ways. As an example, a process utilizing focused ion beam (FIB) milling can be used to create a low-stroke lens that provides aberration correction, as illustrated in FIG. 7A. In some embodiments, the lens surface 718 is formed directly on the fiber tip, while in other embodiments, a mold is machined and the lens is formed separately from the fiber tip and then bonded to the fiber tip. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0106] The curvature of lens surface 718 can be selected to eliminate spherical aberrations resulting from optical surfaces in the system, including the spherical aberrations associated with collimating surface 224 and other surfaces illustrated in FIG. 2A. Thus, through the combination of aberration corrections provided by lens surface 718 and other surfaces, high image quality is provided by embodiments of the present invention. Utilizing scanning fiber designs as discussed herein, it is possible to perform optical corrections on a per-pixel basis in addition to performing optical corrections at the display width scale.

[0107] FIG. 7B is a schematic diagram illustrating a lenticular fiber tip according to another embodiment of the present invention. In addition to aberration correction, embodiments of the present invention enable focusing of light emitted from the fiber tip, as shown, through the use of a positive lens 720 illustrated in FIG. 7B. Lens 720 can be machined directly onto the fiber tip, for example, using an FIB milling process, or can be molded separately from the fiber tip and then bonded to the fiber tip. Emission cone 722 is focused by lens 720, which, in this example, forms focused cone 724. The strength of lens 720 may be such that the light is not focused, but the divergence of the light rays associated with emission cone 722 is reduced.

[0108] FIG. 7C is a schematic diagram illustrating a lenticular fiber tip according to an alternative embodiment of the present invention. In addition to aberration correction and focusing, embodiments of the present invention allow for defocusing of light emitted from the fiber tip, as shown, through the use of a negative lens 730 illustrated in FIG. 7C. Lens 730 can be machined directly onto the fiber tip, for example, using an FIB milling process, or can be molded separately from the fiber tip and then bonded to the fiber tip. Emission cone 732 is defocused by lens 730, forming, in this example, a diverging cone 734. Thus, some embodiments allow for the numerical aperture to be increased through the use of a diverging lens on the fiber tip.

[0109] For example, in contrast to conventional optical systems that image an LCD into an image plane, which is constrained by Lagrange invariants that maintain optical invariants constant throughout the system, fiber scanning systems can modify the pixel characteristics and change the spot size emitted by the fiber. By using the lenses illustrated in Figures 7B and 7C, pixel size modification can be accomplished, e.g., by increasing the numerical aperture and decreasing the pixel size, which reduces the imaged spot size, effectively reducing the mode field diameter.

[0110] 7A-7C can be combined to provide, for example, a lens tip that corrects spherical aberration and focuses the emitted light, corrects spherical aberration and defocuses the emitted light, corrects spherical aberration while providing a lens with a convex region near the fiber core and a concave region near the periphery of the fiber, and the like. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0111] It should also be understood that the examples and embodiments described herein are for illustrative purposes only, and that various modifications or changes in light thereof will be suggested to those skilled in the art and are to be included within the spirit and scope of the present application and the appended claims.

Claims

1. 1. A fiber scanning projector, comprising: a piezoelectric element; and a scanning fiber passing through the piezoelectric element and mechanically coupled to the piezoelectric element, the scanning fiber configured to emit light that propagates along an optical path; and a curved reflector disposed along and perpendicular to the optical path, the curved reflector including an aperture through which the scanning fiber passes; a planar polarization-sensitive reflector disposed along and perpendicular to the optical path; a quarter-wave plate disposed between the curved reflector and the planar polarization-sensitive reflector; A fiber scanning projector comprising:

2. The fiber scanning projector of claim 1 , wherein the quarter wave plate is integrated with the planar polarization sensitive reflector.

3. 1. A fiber scanning projector, comprising: a piezoelectric element; and a scanning fiber passing through the piezoelectric element and mechanically coupled to the piezoelectric element, the scanning fiber configured to emit light that propagates along an optical path; and a planar reflector disposed along and perpendicular to the optical path, the planar reflector including an aperture through which the scanning fiber passes; a curved polarization-sensitive reflector disposed along and perpendicular to the optical path; a quarter-wave plate disposed between the planar reflector and the curved polarization-sensitive reflector; A fiber scanning projector comprising:

4. The fiber scanning projector of claim 3 , wherein an output surface of the scanning fiber defines a spherical object surface.

5. The fiber scanning projector of claim 1 , further comprising a lens disposed along the optical path, the lens configured to adjust a working distance of the fiber scanning projector.

6. The fiber scanning projector of claim 5 further comprising a field of view magnifier disposed between the planar polarization sensitive reflector and the lens.

7. The fiber scanning projector of claim 5 further comprising a spherical aberration corrector disposed between the planar polarization-sensitive reflector and the lens.

8. The fiber scanning projector of claim 3 , wherein the piezoelectric element comprises a piezoelectric actuator and the scanning fiber mechanically coupled to the piezoelectric actuator.

9. The fiber scanning projector of claim 3 , wherein the piezoelectric element comprises a micro-electromechanical system (MEMS) element including a cantilevered beam that supports the scanning fiber.

10. The fiber scanning projector of claim 3 , wherein the quarter wave plate is integrated with the curved polarization sensitive reflector.

11. The fiber scanning projector of claim 3 , wherein the quarter-wave plate and the curved polarization-sensitive reflector are separated by an air gap.

12. The fiber scanning projector of claim 5 , wherein the planar polarization-sensitive reflector and the lens are separated by the working distance.

13. The fiber scanning projector of claim 1 , wherein the quarter wave plate and the curved reflector are separated by an air gap.

14. The fiber scanning projector of claim 1 , wherein an output surface of the scanning fiber defines a spherical object surface.

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