Beam scanner with pic input and display device based on beam scanner

Abstract

Beam scanners and display devices are based on a photonic integrated circuit that couples light to a pair of opposing reflectors. One reflector is tiltable and has an opening through which light is coupled, and the other reflector is configured to focus the light, e.g., a concave reflector. A polarization folding configuration is used to propagate the focused light through the opening in the first reflector, collimated by the second reflector, scanned by the first reflector, and through the second reflector to a pupil replication light guide that provides a plurality of laterally offset parallel portions of the scanned beam.

Description

[0001] Citation of relevant applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 066,592, filed August 17, 2020, entitled “Compact Beam Scanner,” and U.S. Provisional Patent Application No. 63 / 210,969, filed June 15, 2021, entitled “MEMS Scanner with Input Beam Provided by Photonic Integrated Circuit.” This application is a continuation-in-part of and claims priority to U.S. Regular Patent Application No. 17 / 081,272, filed October 27, 2020, entitled “Display with a Compact Beam Scanner,” which claims priority to U.S. Provisional Patent Application No. 63 / 066,592, filed August 17, 2020, entitled “Compact Beam Scanner.” The entire disclosure of all these applications is incorporated herein by reference. Technical Field

[0003] This disclosure relates to image projectors, visual displays including near-eye displays, and related methods. Background Technology

[0004] Visual displays provide information, including still images, videos, and data, to (multiple) viewers. They are used in various fields, including entertainment, education, engineering, science, professional training, and advertising. Some visual displays (e.g., televisions) are designed for multiple users, while some visual display systems (e.g., near-eye displays (NEDs)) are designed for a single user.

[0005] Artificial reality systems typically include near-eye displays (NEDs) configured to present content to a user (e.g., head-mounted devices or glasses). Near-eye displays can show virtual objects or combine images of real objects with virtual objects, as in virtual reality (VR), augmented reality (AR), or mixed reality (MR) applications. For example, in an AR system, a user can view images of virtual objects (e.g., computer-generated images (CGI)) and the surrounding environment by looking at a "combiner" component. The combiner of a wearable display is typically transparent to external light but includes light-routing optics to direct the display light into the user's field of vision.

[0006] Because head-mounted displays (HMDs) or NEDs are typically worn on the user's head, large, bulky, unbalanced, and / or heavy display devices with heavy batteries are cumbersome and uncomfortable for the user. Head-mounted displays require compact and efficient projectors to present images in the angular domain through scanning optical beams. Summary of the Invention

[0007] According to a first aspect of this disclosure, a beam scanner is provided, comprising: a photonic integrated circuit (PIC) including a first waveguide for guiding a first beam; and a first reflector and a second reflector opposite to each other; wherein the first reflector is tiltable upon application of a control signal and has an opening for receiving the first beam coupled from the first waveguide; and wherein the second reflector is configured to reflect at least partially the first beam back to the first reflector after the first beam has propagated through the opening in the first reflector, thereby forming a first collimated beam reflected by the first reflector at a variable angle toward the second reflector, wherein the second reflector is further configured to cause at least a portion of the first collimated beam reflected by the first reflector to propagate through the second sensor.

[0008] In some embodiments, the first reflector includes a microelectromechanical system (MEMS) tiltable reflector. A quarter-wave plate (QWP) may be disposed in the optical path between the first reflector and the second reflector, the quarter-wave plate being used to convert the first linear polarization of the first beam into a second orthogonal linear polarization of the first collimated beam. The second reflector may be polarization-selective. A coupling lens may be disposed in the optical path between the PIC and the opening in the first reflector, for focusing the first beam through the opening.

[0009] In some embodiments, the PIC includes an output device for coupling out the first beam from the waveguide. The output device may include a steering mirror for redirecting the first beam out of the plane of the PIC. The steering mirror may be concave to focus the beam through the opening in the first reflector. The beam scanner may also include an auxiliary waveguide extending from the PIC toward the opening in the first reflector for transmitting the first beam reflected by the steering mirror to the opening in the first reflector. The PIC may also include a second waveguide for guiding a second beam, wherein the second beam coupled from the second waveguide is coupled into the opening in the first reflector. The second reflector may be configured to reflect at least partially the second beam back to the first reflector after it has propagated through the opening in the first reflector, thereby forming a second collimated beam reflected by the first reflector at a variable angle toward the second reflector. The second reflector can also be configured to allow at least a portion of the second collimated beam reflected by the first reflector to propagate through the second reflector.

[0010] In some embodiments, the PIC further includes a combiner element for coupling multiple light sources of different wavelengths to the first waveguide. The combiner element may include a multimode interference (MMI) coupler for combining multiple beams emitted by the multiple light sources. The combiner element may include: a plurality of ring resonators, each of which couples light from one of the multiple light sources to the waveguide; or a plurality of directional couplers, each of which couples light from a specific light source among the multiple light sources to the waveguide. The combiner element may include a cavity having an output waveguide coupled thereto and a plurality of input waveguides, each of which couples light from one of the multiple light sources to the cavity. The cavity may include a nanostructure providing a non-uniform spatial distribution of an effective dielectric constant and optimized to couple light emitted by each light source to the output waveguide of the combiner element.

[0011] According to a second aspect of this disclosure, a display device is provided, comprising: a first light source for emitting a first beam, a PIC as described herein, and a pupil replication light guide. The pupil replication light guide is configured to couple into the collimated beam propagating through the second reflector and to couple out a plurality of portions of the collimated beam at a coupling angle, wherein the plurality of portions are offset along the length dimension of the eyebox of the display device.

[0012] The pupil replication light guide may include an input grating and an output grating, the input grating for coupling the collimated beam and the output grating for coupling multiple portions of the collimated beam out along the length dimension of the window. The display device guide may also include a controller operatively coupled to the first light source and the first reflector, and configured to control the brightness of the first light source in coordination with the application of a control signal to the first reflector for scanning multiple portions of the collimated beam, thereby forming an image in the angular domain at the window. In embodiments where the display device includes a second light source for emitting a second beam with a wavelength different from that of the first beam, the PIC may further include a combiner element for optically coupling the first beam and the second beam into the first waveguide.

[0013] According to a third aspect of this disclosure, a method for scanning a light beam is provided, the method comprising: guiding a light beam in a waveguide of a photonic integrated circuit (PIC) through an opening in a first reflector to a second reflector opposite to the first reflector, wherein the first reflector is tiltable upon application of a control signal; reflecting at least partially the light beam propagating through the opening toward the first reflector to form a collimated beam; reflecting the collimated beam back to the second reflector at a variable angle through the first reflector; causing at least a portion of the collimated beam reflected by the first reflector to propagate through the second reflector; and applying the control signal to the first reflector to tilt the first reflector thereby scanning the collimated beam propagating through the second reflector at an angle.

[0014] In some embodiments, the method includes using a coupling lens to couple the beam guided by the waveguide of the PIC to the opening in the first reflector. In embodiments where the second reflector is polarization selective, the method may further include converting the polarization of the beam in the optical path between the first and second incident points to the second reflector from a first polarization state to a second polarization state, in which the beam is reflected by the second reflector and in which the beam propagates through the second reflector in the second polarization state. Attached Figure Description

[0015] The example will now be described in conjunction with the accompanying drawings, in which...

[0016] Figure 1 This is a schematic diagram of a near-eye display based on a scanning image projector;

[0017] Figure 2A This is a schematic cross-sectional view of a compact scanning projector of the present disclosure, with the tiltable reflector of the projector in a non-tilted position;

[0018] Figure 2B for Figure 2A A schematic cross-sectional view of a scanning projector in which the tiltable reflector is in an tilted position;

[0019] Figure 2C For based on Figure 2A and Figure 2B A schematic cross-sectional view of a near-eye display for a scanning projector;

[0020] Figure 3 A schematic cross-sectional view of a compact scanning projector with multiple optical inputs;

[0021] Figure 4A A polarization diagram of a scanning projector with a linearly polarized selective reflector;

[0022] Figure 4BA polarization diagram of a scanning projector with a circular polarization-selective reflector;

[0023] Figure 5 This is a plan view of the 2D tiltable reflector disclosed herein;

[0024] Figure 6A For use Figure 2A and Figure 2B A plan view of the photonic integrated circuit (PIC) coupler in the scanning projector;

[0025] Figure 6B for Figure 6A A magnified view of the PIC coupler;

[0026] Figure 6C for Figure 6A A side cross-sectional view of a PIC coupler with a coupling lens;

[0027] Figure 6D To demonstrate how light passes through Figure 6C A diagram showing the trajectory of light rays propagating through a coupling lens;

[0028] Figure 7A A schematic diagram of a multi-wavelength transmitter and PIC structure with wavelength division multiplexing (WDM).

[0029] Figure 7B A schematic top view of a PIC with wavelength division multiplexing from a separate transmitter to a common waveguide;

[0030] Figure 8A This is a schematic diagram of a multimode interference (MMI) coupler used to combine light sources of different wavelengths;

[0031] Figure 8B A schematic diagram of a coupler-based ring resonator used to combine light sources of different wavelengths;

[0032] Figure 8C This is a schematic diagram of a composite directional coupler used to combine light sources of different wavelengths;

[0033] Figure 8D This is a schematic diagram of a compact multimode coupler used to combine light sources of different wavelengths, where the coupler's cavity is inversely optimized.

[0034] Figure 9A A side cross-sectional view of a PIC coupler using a straight etched mirror;

[0035] Figure 9BA side cross-sectional view of a PIC coupler using an off-center concave etched mirror;

[0036] Figure 9C This is a side cross-sectional view of a PIC optical coupler based on an array of vertically placed auxiliary waveguides.

[0037] Figure 9D Includes side and front views of a PIC coupler using straight-etched mirrors and beamforming optics;

[0038] Figure 10 Here is a flowchart of a method for scanning a light beam according to this disclosure;

[0039] Figure 11 A view of the augmented reality (AR) display of this disclosure having a shape factor of a pair of glasses; and

[0040] Figure 12 This is a 3D view of the head-mounted display (HMD) disclosed herein. Detailed Implementation

[0041] While this teaching has been described in conjunction with various embodiments and examples, it is not intended to limit this teaching to such embodiments. Rather, as those skilled in the art will understand, this teaching encompasses various alternatives and equivalents. All statements regarding the principles, aspects, and embodiments of this disclosure and their specific examples recorded herein are intended to cover both their structural and functional equivalents. Furthermore, such equivalents are intended to include both currently known equivalents and those developed in the future (i.e., any element developed to perform the same function, regardless of its structure).

[0042] As used herein, unless explicitly stated otherwise, the terms “first” and “second” are not intended to imply sequence, but rather to distinguish one element from another. Similarly, unless explicitly stated otherwise, the order of method steps does not imply the order in which they are performed.

[0043] A scanning projector display can scan an intensity-modulated light beam at an angle about one or two axes using tiltable mirrors. As the beam is scanned, its brightness and / or color can vary with the scan to provide an image in the angular domain. The beam can be scanned in two directions (e.g., in the X and Y angles). When the frame rate is high enough, the eye integrates the scanned beam, allowing the user to see the displayed image with virtually no flicker. The scanner is capable of scanning the beam across the entire field of view (FOV) of the display. FOV can be defined as the solid angle within which the light can provide an image to the viewer.

[0044] A relay lightguide can be provided to relay an image in the angular domain to the display window. The relay lightguide can be configured to provide a pupil copy of the relayed light to extend the light across the display window. This type of lightguide is called a pupil copy lightguide. The pupil copy lightguide provides multiple offset portions of the beam at the same angle, as well as a scan input beam. When the eye is positioned behind the pupil copy lightguide, the eye can directly (i.e., without an eyepiece) see the raster image, resulting in a compact and lightweight overall display construction.

[0045] To minimize beam discrepancy at the input coupler of the pupil replication light guide, it is desirable to place the scanning mirror closer to the pupil replication light guide. Furthermore, to maximize the angular scanning range of the tiltable mirror, the beam needs to be incident on the tiltable mirror almost perpendicularly. To accommodate these two requirements, the beam can be guided through the pupil replication light guide before incident on the tiltable mirror. Allowing a collimated beam to propagate through the pupil replication light guide is undesirable, as this would result in bright spot artifacts in the angular domain image.

[0046] This disclosure presents a scanning projector configuration without the aforementioned limitations. A small opening is provided in a tiltable mirror, and an intensity-modulated beam is focused through the opening to be incident on a fixed concave mirror, which collimates the beam upon reflection and redirects it back to the tiltable mirror, which scans the beam at an angle. A polarization configuration can be employed to allow the scanning beam to propagate a second time through a curved mirror, thereby propagating the beam to a pupil replication light guide. A photonic integrated circuit (PIC) is used to guide the focused beam into the opening in the tiltable mirror. The PIC can transmit light from multiple light sources and can combine light from different color channels into the opening in the tiltable mirror, as described herein.

[0047] Now refer to Figure 1The display device 100 includes a light source 102 for providing a beam 104. An electronic driver 106 is operatively coupled to the light source 102 to power the light source 102. A beam scanner 108, including a tiltable reflector (e.g., a microelectromechanical system (MEMS) tiltable reflector), is optically coupled to the light source 102 to scan the beam 104 generated by the light source 102. The scanning can be performed in one or two dimensions (e.g., about the X-axis and / or the Y-axis perpendicular to the X-axis), wherein the X-axis and Y-axis lie in the plane in which the MEMS reflector is in its normal position (i.e., the unpowered position). A pupil replicator 110 provides a light field 115 comprising multiple laterally shifted parallel portions of the scanning beam 104, which repeat the beam angle (i.e., the propagation direction of the beam 104 at each moment) as the beam 104 scans about one or both axes (as appropriate).

[0048] Controller 112 is operatively coupled to beam scanner 108 and electronic driver 106. Controller 112 is configured to operate electronic driver 106 to power light source 102 in coordination with driving beam scanner 108 and reading its position. For example, controller 112 may apply control signal 113 to cause beam scanner 108 to scan beam 104 through a series of beam angles or from direction “A” to direction “G”, while applying power signal 111 to cause electronic driver 106 to change the brightness of light source 102 according to the image to be displayed, thereby forming an image in the angular domain for direct observation by the viewer’s eye 114. Feedback circuitry can provide feedback signal 117 to indicate the current position of the MEMS mirror to controller 112.

[0049] As shown, the pupil replicator 110 provides multiple parallel portions of the scanning beam 104 with lateral shifts in directions "A" to "G". As shown, the viewer's eye 114 receives the light field 115, and an image is formed at the retina 116 of the eye by the corresponding replicated beam. The linear positions of the beam portions on the retina 116 of the eye are indicated by the letters "a" to "g" and correspond to the beam angles or directions "A" to "G" of the scanning beam 104. In this way, the image in the angular domain formed by the light field 115 originating from the eye 114 forms an image in the linear domain on the retina 116 of the eye.

[0050] One challenge associated with the display device 100 is the reduction in FOV caused by the tilt angle of the beam incident on the skewed tiltable reflector of the beam scanner 108. This tilt angle is necessary for optical geometry to, for example, physically separate the incident beam from the scanned (i.e., reflected) beam. The reduction in FOV is caused by distortion of the solid angle, which represents the scan range at the tilt angle of the beam incident on the tiltable reflector.

[0051] The beam scanner disclosed herein includes a tiltable reflector with an opening and a curved reflector disposed opposite the tiltable reflector for reflecting light transmitted through the opening back to the tiltable reflector. This configuration avoids the aforementioned disadvantages because it allows the beam to be incident nearly perpendicularly on the tiltable reflector and to be positioned nearly parallel to the beam replicator (e.g., a pupil replica light guide).

[0052] Reference Figure 2A , can Figure 1 The display device 100 uses a beam scanner 200, which is a scanner in which the incident angle of the beam on the reflector of the scanner is close to vertical. Figure 2A The beam scanner 200 includes a photonic integrated circuit (PIC) 202 having a waveguide 204 for guiding a beam 201 toward a first reflector 210. The first reflector 210 is tiltable by a controlled amount when a control signal is applied. The first reflector 210 can be tilted about one axis or two non-parallel axes and may include, for example, a microelectromechanical system (MEMS) tiltable reflector. A second reflector 220 is disposed opposite to the first reflector 210.

[0053] During operation, beam 201 is coupled out from waveguide 204 of PIC 202 and refocused from the rear side 211 of first reflector 210 into opening 215 in first reflector 210 by optional coupling lens 206. After propagating through opening 215, beam 201 diverges (as shown by ray 213). Second reflector 220 is configured to at least partially reflect beam 201 back to first reflector 210 and collimate beam 201, thereby forming collimated beam 203 propagating toward first reflector 210. For example, as Figure 2A As shown, the second reflector 220 may be concave. The second reflector 220 may, for example, have a parabolic shape.

[0054] The collimated beam 203 is reflected back to the second reflector 220 by the first reflector 210 at an angle dependent on the tilt angle of the first reflector 210. At least a portion of the double-reflected beam (also referred to herein as the scanning beam 205) propagates through the second reflector 220 and illuminates the input coupler 225 of the pupil replication light guide 240. The input coupler 225 may include one or more diffraction gratings configured to couple the scanning beam 205 into the pupil replication light guide 240. Optical loss in the beam scanner 200 is minimal because the area of ​​the opening 215 is much smaller than the total reflective area of ​​the first reflector 210. For example, the area of ​​the opening may be from 20% to 0.001% of the reflective area of ​​the first reflector 210.

[0055] The light beam 201 travels along a foldable optical path using polarizing elements within a cavity 222 between the first reflector 210 and the second reflector 220. For example, the coating 221 of the second reflector 220 can be polarization-selective, and the folded optical path can include an optical element that converts the polarization state of the light beam 201 from a first state to a second state (for simplicity, this optical element is not shown in the image). Figure 2A and Figure 2B As shown in the figure, light in the first state is reflected by the polarization-selective coating 221, and light in the second state is transmitted through the polarization-selective coating 221. Figures 2A to 2C Non-limiting examples of polarization configurations for folding the beam path in the beam scanner 200 are omitted; these examples are referred to below. Figure 4A and Figure 4B Further consideration is needed.

[0056] The second reflector 220 can be positioned appropriately close to the first reflector 210, such that the distance d between the first reflector 210 and the pupil replication light guide 240 is small. This distance can depend on the size of the first reflector 210 and the range of its tilt angle. As an example, the distance between the first reflector 210 and the pupil replication light guide 240 can be 1 mm or less.

[0057] Reference Figure 2B The diagram shows a tilted first reflector 210, which reflects the scanning beam 205 at a tilted angle. The opening 215 should be large enough to accommodate the waist 251 of the focused beam 201. The opening 215 may gradually narrow from one or both sides to facilitate beam propagation. The area 227 of the input coupler 225 is large enough to couple the scanning beam 205 to the pupil replication light guide 240. Because the first reflector 210 is very close to the pupil replication light guide 240, the area 227 is relatively small.

[0058] Reference Figure 2C Display device 250 uses Figure 2A and Figure 2B 200 beam scanner. Figure 2CThe display device 250 includes: a light source 261 for emitting a light beam 201; a PIC 202 coupled to the light source 261; a first reflector 210 and a second reflector 220 opposite to each other; and a pupil replication light guide 240. The first reflector 210 is tiltable when a control signal 113 is applied and has an opening 215 through the first reflector 210 for receiving the light beam 201 coupled from the waveguide 204. The opening 215 may include a transparent material and may be tapered to better accommodate the focused light beam and the tilt of the first reflector 210. The second reflector 220 is configured to reflect the light beam 201 back to the first reflector 210 after it has propagated through the opening 215 in the first reflector 210, thereby forming a collimated beam reflected by the first reflector 210 at a variable angle toward the second reflector 220, thereby forming a scanning beam 205. At least a portion of the scanning beam 205 propagates through the second reflector 220 and illuminates the input coupler 225 of the pupil replication light guide 240. The input coupler 225 of the pupil replication light guide 240 is configured to couple the scanning beam 205 propagating through the second reflector 220 into the pupil replication light guide. The pupil replication light guide 240 may also include at least one coupling grating 230 for coupling out multiple portions of the scanning beam 205 (two coupling gratings are shown in FIG. 2). These portions are along the length dimension of the viewing window 252 of the display device 250 (i.e., Figure 2C (X-dimensional offset) in the model.

[0059] The controller 255 can be operatively coupled to the light source 261 and the first reflector 210, and is configured to control at least one of the brightness or color of the light source 261 in coordination with the application of the control signal 113 to the first reflector 210, for scanning a collimated beam portion coupled out by the plurality of coupling gratings 230 of the pupil replication light guide 240, thereby forming an image in the angular domain at the viewing window of the display device 250. The controller 255 can use the feedback signal 117 to obtain information about the current tilt angle of the tiltable reflector 210. For example, the feedback signal 117 may include time sampling of the X and Y angular positions of the first reflector 210, a synchronization signal of the first reflector 210 at a specific predetermined tilt angle, etc. The light source 261 may include one or more emitters, which may be based on solid-state single-mode or multi-mode light sources, such as light-emitting diodes (LEDs), superluminescent light-emitting diodes (SLEDs), side-emitting laser diodes, vertical-cavity surface-emitting laser diodes (VCSELs), etc.

[0060] A multi-emitter light source provides multiple beams of light, either of the same or different colors, which are focused into multiple focal points close to each other. For example, reference... Figure 3 Multiple focal points 301 are disposed within a common opening 215 in the first reflector 210. The multiple focal points 301 can support different colors in a color image and / or provide enhanced image resolution in a scan projector-based display by using different emitters for different pixels or groups of pixels in the image being displayed.

[0061] We will now consider the polarization-based beam folding configuration of the beam scanner 200. First, refer to... Figure 4A The beam scanner 400A includes a first (tiltable) reflector 210 and a second (collimated) reflector, the second (collimated) reflector including a reflective polarizer 420 facing the first reflector. In the illustrated example, the reflective polarizer 420 is a linear reflective polarizer configured to reflect onto... Figure 4A p-polarized light polarized in the plane and transmitted perpendicular to the plane. Figure 4A The plane-polarized s-polarized light. The reflective polarizer 420 can be implemented as... Figure 2A and Figure 2BThe coating on the second reflector 220 of the beam scanner 200. The light 401 of the converging / diverging beam 201 is circularly polarized. A properly oriented quarter-wave plate (QWP) 425, positioned in the optical path between the first reflector 210 and the reflecting polarizer 420, converts the polarization state of the light 401 to a p-polarized state. The p-polarized light is reflected back by the reflecting polarizer 420, forming a reflected light 403. The propagation of the reflected light 403 through the QWP 425 converts the p-polarized state back to a circularly polarized state. Reflection from the first reflector 210 converts the circularly polarized state of the scanning light 405 of the scanning beam 205 to an orthogonal circularly polarized state. A third pass through the QWP 425 converts the orthogonal circularly polarized state to a linear s-polarized state. In this polarization state, the scanning light 405 is transmitted through the linear reflecting polarizer 420. In another example, by changing the orientation of the QWP 425 and the polarization of the input light 401 accordingly, the reflective polarizer 420 can be configured to reflect s-polarized light and transmit p-polarized light. The QWP 425 can be positioned anywhere between the first reflector 210 and the reflective polarizer 420; in some examples, the QWP can be laminated onto the reflective polarizer 420 and facing the first reflector 210, or it can be laminated onto the first reflector 210 and facing the reflective polarizer 420.

[0062] Turning Figure 4B The beam scanner 400B includes a first (tiltable) reflector 210 and a second (collimated) reflector opposite to each other. The second (collimated) reflector includes a cholesteric liquid crystal (ChLC) polarizer 423. The ChLC polarizer 423 can be configured to reflect circularly polarized light with the same helicity as the ChLC material and transmit circularly polarized light with the opposite helicity. In the example shown, the ChLC polarizer 423 is configured to reflect the circularly polarized input light 401, thereby forming a reflected light 403. The reflection from the first reflector 210 converts the circular polarization into orthogonal circular polarization of the scanning light 405, which is then transmitted through the ChLC polarizer 423. Therefore, in Figure 4B In the example, a QWP is not required between the first reflector 210 and the ChLC polarizer 423. Although in Figure 4A and Figure 4B In the diagram, the right-side reflectors 420 and 423 are schematically shown as flat, but as mentioned above, these right-side reflectors may also have a concave reflective surface facing the first reflector.

[0063] In any of the examples and embodiments described herein, the first reflector 210 may include a MEMS tiltable reflector. As a non-limiting illustrative example, Figure 5 The MEMS scanner 500 includes a reflector 510 tiltable about two orthogonal axes. The tiltable reflector 510 (e.g., a mirror or diffraction grating) may be supported by a pair of first torsion hinges 501, allowing the reflector 510 to tilt about the X-axis. The first torsion hinges 501 extend from the tiltable reflector 510 to a gimbal 520, which is supported by a pair of second torsion hinges 502 extending from the gimbal 520 to a fixed base 522, or optionally a second gimbal located between the gimbal and the fixed base, such that the gimbal 520 tilts together with the reflector 510 about the Y-axis. The fixed base 522 may be supported by a substrate 555. An actuator may be disposed below the tiltable reflector 510 and / or the gimbal 520 to provide force for actuating the tilting of the reflector 510 about the X and Y axes. The actuator may be electrostatic, electromagnetic, piezoelectric, etc. For electrostatic reflector actuation, the comb-shaped drive element can be located on the torsion hinge. For example, one actuator (not shown) can be located below the edge of reflector 510 to tilt reflector 510 about the X-axis, while another actuator (not shown) can be located below gimbal 520 to tilt gimbal 520 together with reflector 510 about the Y-axis.

[0064] Reflector 510 may have an opening 515 to allow an input light beam to propagate through it. For example, opening 515 may be a through-hole or aperture in the middle portion of the tiltable reflector 510, giving the tiltable reflector 510 an annular shape. Opening 515 may be filled with a transparent material. In at least some examples, opening 515 may be located in… Figure 5 The center of the tiltable reflector 510 is marked at the intersection of the tilted axes X and Y, so the opening position remains unchanged during tilting. The opening 515 being located off-center is also within the scope of the invention. Although the opening 515 is shown as having a circular shape, different shapes of apertures can be used, including but not limited to square, rectangular, slit-shaped, or any other shape generally suitable in certain examples. As a non-limiting example, the tiltable reflector 510 can be a circular reflector with a diameter of 1.5 mm, and the opening 515 can have a diameter from 0.005 mm to 0.2 mm. Although Figure 5 A gimbaled reflector has been shown, but non-gimbaled reflectors with openings (including non-gimbaled MEMS reflectors) can also be used to implement the first reflector 210. In some examples, an annular reinforcement structure may be provided on the back side of the tiltable reflector 510.

[0065] An example construction of a PIC that transmits light to the opening of the tiltable reflector of this disclosure will now be considered. (Refer to...) Figure 6A The PIC 602 includes multiple waveguides 604, each optically coupled to a single emitter 655 of a multi-emitter light source 660. All waveguides 604 lead to a coupling region 662 of the PIC 602, which is located in... Figure 6B This is shown in more detail below. Each waveguide 604 ends with a grating coupler 664, which couples the light propagating in the waveguide 604 out of the PIC 602. The coupling region 662 is set in... Figure 6C The coupling lens 670 is shown in the focal plane. The coupling lens 670 is positioned in the optical path between the PIC 602 and the opening 215 in the first reflector 210, so that the beam 601 coupled from a single grating extractor 664 is focused through the opening 215 in the first (i.e., tiltable) reflector 210. As shown, the opening 215 may be tapered. Multiple grating extractors 664 are arranged close to each other to ensure that the focal points of the focused beam 601 are positioned close to each other and all fit into the opening 215.

[0066] Different emitters 655 can emit light of the same color channel wavelength or light of different color channels wavelengths. When the emission wavelengths of different emitters 655 belong to the same color channel or the luminance channel for a monochrome image, the spatial resolution of the PIC602-based scanning display device can be increased by simultaneously projecting several pixels of the image at any instantaneous tilt angle of the first reflector 210. When the emission wavelengths of different emitters 655 belong to different color channels, a color image can be produced. Figure 6A and Figure 6B In the example shown, all transmitters 655 belong to three different groups: three transmitters 655R provide light in the red channel, three transmitters 655G provide light in the green channel, and three transmitters 655B provide light in the blue channel. Correspondingly, three waveguides 604R transmit light in the red channel, three waveguides 604G transmit light in the green channel, and three waveguides 604B transmit light in the blue channel. Three couplers 664R couple light out of the red channel, three couplers 664G couple light out of the green channel, and three couplers 664B couple light out of the blue channel. The actual number of transmitters per channel can vary from one transmitter and one waveguide to multiple (e.g., 18 or more) transmitters and multiple waveguides.

[0067] The coupling lens 670 refocuses the light beams 601 of all color channels through the opening 215, as shown, which may be tapered on one or both sides. The light beams 601 of all color channels then proceed as described above. Figures 2A to 2C , Figure 3 , Figure 4A and Figure 4B The beam propagates as explained. The second reflector is configured to reflect at least partially all color channels of the beam 601 back to the first reflector after the beam 601 has propagated through the opening 215 in the first reflector 210, thereby forming a collimated beam that is reflected by the first reflector 210 at a variable angle toward the second reflector 220. Figures 2A to 2C The second reflector 220 is configured to allow at least a portion of each collimated beam reflected by the first reflector 210 to pass through it. (See above for reference.) Figure 3 The co-propagation of multiple beams is shown.

[0068] The exact number of co-propagating collimated beams corresponds to the number of transmitters used. There can be one, two, or more transmitters, and one, two, or more beams with the same or different color channels, luminance channels, etc. The co-scan collimated beams emitted by different transmitters will have slightly different propagation angles, but this difference can be achieved by controlling the timing of all transmitters and scanning mirrors (i.e., the first reflector 210) by a controller. Figure 6D (The rendering of the coupling lens 670 in optical design software is shown in the case where three beams are coupled out by three adjacent grating couplers 664.)

[0069] In some examples, light from different color channels can be combined to propagate within the same waveguide of the PIC, resulting in a more compact and efficient overall construction. (Reference) Figure 7A As a non-limiting example, the coupling region 762 of the PIC 702 includes six couplers 764, each coupler 764 coupling out a combined beam comprising light from the red channel emitter 755R, the green channel emitter 755G, and the blue channel emitter 755B. This combined beam is composed of... Figure 7A The thin black arrows in the diagram illustrate this. The combination function can be provided by the wavelength division multiplexer element of each of the 764 outputs. This is similar to, for example... Figure 6B (where individual color channels are not reused) This results in a more compact overall structure and / or enables more coupled color channel beams.

[0070] Go to Figure 7BThe multi-emitter light source 760 includes a red channel emitter 755R, a green channel emitter 755G, and a blue channel emitter 755B. For simplicity, only three emitters for each color channel are shown. The multi-emitter light source 760 is optically coupled to a PIC 702, which includes multiple combiner elements 774, each combining element 774 corresponding to each triplet of red emitter 755R, green emitter 755G, and blue emitter 755B. Each combiner element 774 optically couples the corresponding red emitter 755R, green emitter 755G, and blue emitter 755B to a common waveguide 704, which terminates with a corresponding coupler 764. At least one combiner element 774, waveguide 704, and coupler 764 may be provided.

[0071] Now we will consider an example construction of the combiner element 774. (Refer to...) Figure 8A A multimode interference (MMI) coupler 874A combines the beams from the red emitter 755R, the green emitter 755G, and the blue emitter 755B to propagate in a common waveguide 704, which guides the combined light to the output 764. The MMI coupler 874A is configured to excite several propagation modes within it such that for each of the red, green, and blue channels emitted by the corresponding red emitter 755R, green emitter 755G, and blue emitter 755B, the maximum intermode interference coincides with the position of the end of the waveguide 704 in the MMI coupler 874A.

[0072] Go to Figure 8B The ring combiner element 874B includes multiple ring resonators 875R, 875G, and 875B. Each ring resonator 875R, 875G, and 875B optically couples the light from a specific one of the red emitter 755R, green emitter 755G, and blue emitter 755B to a common waveguide 704, which guides the light to a coupler 764. Each ring resonator 875R, 875G, and 875B is configured to efficiently couple the light from a specific one of the red emitter 755R, green emitter 755G, and blue emitter 755B, without coupling the light from the other emitters.

[0073] Now refer to Figure 8C The directional coupler combiner element 874C includes directional couplers 881 and 882 formed together with a common waveguide 704. Figure 8C In the non-limiting example shown, the first directional coupler 881 is coupled to the red transmitter 755R, the second directional coupler 882 is coupled to the blue transmitter 755B, and the common waveguide 704 is coupled to the green transmitter 755G.

[0074] Reference Figure 8D The combiner element 874D includes a cavity 890, multiple input waveguides 891R, 891G, and 891B, and an output waveguide 892. Each input waveguide 891R, 891G, and 891B couples light from the red, green, and blue channels of the light source to the cavity 890, respectively. For simplicity, the light sources are not shown. The cavity 890 has a non-uniform spatial distribution of its effective dielectric constant ε(x,y). This effective dielectric constant ε(x,y) is determined by a nanostructure comprising, for example, a series of points. This nanostructure is optimized using an inverse optimization method to couple the light emitted by each light source to the output waveguide 892.

[0075] The inverse optimization process of the combiner element 874D is achieved by... Figure 8D Top views 894, 894R, 894G, and 894B are compared with their corresponding bottom views 895, 895R, 895G, and 895B for illustration. View 894 shows a non-optimized combiner element with a seed nanostructure 896 in cavity 890. Top views 894R, 894G, and 894B show wave calculation results for light in the red, green, and blue channels, respectively, where light propagates from one of the input waveguides 891R, 891G, and 891B to the output waveguide 892. It can be seen that most of the light in the red, green, and blue channels misses the output waveguide 892. The simulation software is then configured to perturb and optimize the seed nanostructure 896 of cavity 890 to reach the final nanostructure 898 shown in view 895, and to re-propagate the light in the red, green, and blue channels. The final nanostructure 898 in cavity 890 has an optimized non-uniform spatial distribution of the effective dielectric constant ε(x,y), which enables cavity 890 to propagate light from the red channel, green channel and blue channel from input waveguides 891R, 891G and 891B to output waveguide 892 with high efficiency, as shown in bottom view 895R, bottom view 895G and bottom view 895B respectively.

[0076] Reference Figure 9APIC 902A includes a waveguide 904 and a tilted, flat steering mirror 964A that couples out a beam 901 from the waveguide 904. The steering mirror 964A can be fabricated, for example, by directional etching of the PIC 902, wherein the steering mirror 964A is simply one of a plurality of parallel surfaces of an etched slit-like opening or cutout 984. An auxiliary waveguide 986 (e.g., a thin segment of an optical fiber or similar waveguide) can extend from the PIC 902A toward an opening 215 in the first reflector 210 for guiding (i.e., guiding within the auxiliary waveguide) the beam 901 reflected by the steering mirror 964A to the opening 215 in the first reflector 210. The auxiliary waveguide 986 may terminate with a lens element 988 supported by or extending from the auxiliary waveguide 986. The lens element 988 facilitates focusing the beam 901 through the opening 215.

[0077] Go to Figure 9B The PIC 902B is similar to Figure 9A The only difference between the PIC 902A and the PIC 902A is that the steering mirror 964B is curved, thus forming an off-axis concave reflector to focus the beam 901 onto the auxiliary waveguide 986.

[0078] Several auxiliary waveguides 986 can be combined to transmit, for example, different beams from different emitters of a multi-emitter light source. (See reference...) Figure 9C As an example, three auxiliary waveguides 986 are optically coupled to three couplers 964C, which may be gratings and / or steering mirrors, for coupling out light from the red channel 901R, the green channel 901G, and the blue channel 901B, respectively. The auxiliary waveguides 986 may be formed in a common substrate 987, which is disposed on the PIC 902C at a non-parallel angle (e.g., vertical).

[0079] Reference Figure 9D The PIC coupler 902D is shown in the side and front views. Figure 9D The PIC coupler 902D includes an array of waveguides 904 and a tilted, flat steering mirror 964A that couples the beam 901 out of the waveguides 904. Coupling in Figure 9D This occurs in the upward direction. The steering mirror 964A can be fabricated, for example, by directional etching of the PIC 902 across all waveguides 904 of the array; the steering mirror 964A is simply one of a plurality of parallel surfaces of etched slit-like openings or cutouts 984. The PIC coupler 902D is similar to... Figure 9A The PIC 902A, but the PIC coupler 902D includes a beamforming optics 970 instead of an auxiliary waveguide 986. Beamforming optics 970 ( Figure 9DIt operates as a pupil repeater. Specifically, the shaping optics 970 transmits the output beam 901, converted by the steering mirror 964A, to the opening 215, while simultaneously refocusing the output beam at the opening 215.

[0080] Now refer to Figure 10 And further refer to Figures 2A to 2C as well as Figure 4A A method for (e.g., using) Figures 2A to 2C The method 1000 for scanning a beam using a beam scanner 200 includes: guiding ( Figure 10 A beam of light (e.g., beam 201) in the waveguide of the PIC (e.g., waveguide 204 of PIC 202) passes through an opening 215 in the first reflector 210 and reaches a second reflector 220 opposite to the first reflector 210. The first reflector 210 may be tilted when a control signal is applied to the first reflector 210. The beam 201 propagating through the opening 215 is reflected at least partially toward the first reflector 210 (1004), thereby forming a collimated beam 203. The collimated beam 203 is reflected back to the second reflector 220 through the first reflector 210 at a variable angle (depending on the applied control signal) (1006). At least a portion of the collimated beam 203 reflected by the first reflector 210 then propagates through the second reflector 220 (1008). A control signal (1010) is applied to the first reflector 210 to tilt the first reflector 210, thereby scanning the collimated beam 205 propagating through the second reflector 220 at an angle.

[0081] In some examples, in step 1002, the coupling lens (e.g., Figure 2A The coupling lens 206 in the first reflector 210 is used to couple the beam 201 guided by the waveguide 204 of the PIC 202 to the opening 215 in the first reflector 210. The second reflector 220 may be polarization selective; for example, the second reflector may include a polarization selective coating 221. Figure 2A ) and / or reflective polarizer 420 ( Figure 4A Method 1000 may further include converting the polarization of the beam 201 in the optical path between the first and second incidents of the beam 201 to the second reflector 220 from a first polarization state (in which the beam 201 is reflected by the second reflector) to a second polarization state (in which the collimated scanning beam 205 propagates through the second reflector). On the first incident, the diverging beam 201 is reflected at least partially from the second reflector 220 or the reflecting polarizer 420 (1004); and on the second incident, the collimated scanning beam 205 is transmitted (1008) through the second reflector 220 or the reflecting polarizer 420.

[0082] Go to Figure 11 Augmented reality (AR) near-eye display 1100 is Figure 2C An example of a display device 250. An AR near-eye display 1100 includes a frame 1101 having the shape factors of a pair of glasses. For each eye, the frame 1101 supports: a projector 1108 including a beam scanner as described herein; a pupil replication light guide 1110 optically coupled to the projector 1108; an eye-tracking camera 1104; and a plurality of illuminators 1106. The illuminators 1106 may be supported by the pupil replication light guide 1110 for illuminating a viewing window 1112. The projector 1108 provides a fan beam carrying an image in the angular domain to be projected onto the user's eye. The pupil replication light guide 1110 receives the fan beam and provides multiple laterally offset parallel copies of each beam of the fan beam, thereby extending the projected image onto the viewing window 1112.

[0083] A multi-emitter laser source can be used in the projector 1108. Each emitter of the multi-emitter laser chip can be configured to emit image light at the same or different color channel wavelengths. The emission wavelengths of different emitters of the same multi-emitter laser chip can occupy a spectral band with the spectral width of the laser source.

[0084] In some examples, projector 1108 may include two or more multi-emitter laser chips that emit light at wavelengths of the same or different color channels. For AR applications, pupil replication light guide 1110 may be transparent or translucent to allow the user to view the external world and the image projected into each eye and superimposed on the view of the external world. The image projected into each eye may include objects set to simulate parallax so that it appears as if immersed in a real-world view.

[0085] The purpose of the eye-tracking camera 1104 is to determine the position and / or orientation of the user's two eyes. Once the position and orientation of the user's eyes are known, the gaze convergence distance and direction can be determined. The image displayed by the projector 1108 can be dynamically adjusted to take into account the user's gaze, to achieve better realism in immersing the user in the displayed augmented reality scene, and / or to provide specific functions for interacting with augmented reality. During operation, the illuminator 1106 illuminates the eye corresponding to the viewport 1112 so that the eye-tracking camera acquires an image of the eye and provides a reference reflection (i.e., a flicker). The flicker can be used as a reference point in the captured eye image, thereby facilitating the determination of the eye gaze direction by determining the position of the eye pupil image relative to the flicker image. To avoid distracting the user, the illumination light can be made invisible to the user. For example, infrared light can be used to illuminate the viewport 1112.

[0086] The function of the eye-tracking camera controller is to process the images acquired by the eye-tracking camera 1104 to determine the gaze direction of the user's two eyes in real time. In some examples, image processing and eye position / orientation determination functions may be performed by the central controller (not shown) of the AR near-eye display 1100. The central controller may also provide control signals to the projector 1108 to generate an image to be displayed to the user, depending on the determined eye position, eye orientation, gaze direction, eye convergence, etc.

[0087] Go to Figure 12 The HMD 1200 is an example of an AR / VR wearable display system. The HMD 1200 is... Figure 2C Another example of a display device 250. The HMD 1200 functions to enhance the view of a physically real-world environment using computer-generated images and / or generate fully virtual 3D images. The HMD 1200 may include a front body 1202 and a strap 1204. The front body 1202 is configured to be placed reliably and comfortably in front of the user's eyes, and the strap 1204 can be stretched to secure the front body 1202 to the user's head. A display system 1280 may be disposed within the front body 1202 to present AR / VR images to the user. The sides 1206 of the front body 1202 may be opaque or transparent.

[0088] In some examples, the front body 1202 includes a locator 1208, an inertial measurement unit (IMU) 1210 for tracking the acceleration of the HMD 1200, and a position sensor 1212 for tracking the position of the HMD 1200. The IMU 1210 is an electronic device that generates data indicating the position of the HMD 1200 based on measurement signals received from one or more of the position sensors 1212, which generate one or more measurement signals in response to motion of the HMD 1200. Examples of position sensors 1212 include one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor for detecting motion, a sensor for error correction of the IMU 1210, or some combination thereof. The position sensor 1212 may be located external to the IMU 1210, internal to the IMU 1210, or some combination thereof.

[0089] The locator 1208 is tracked by an external imaging device of the virtual reality system, enabling the virtual reality system to track the position and orientation of the entire HMD 1200. Information generated by the IMU 1210 and position sensor 1212 can be compared with the position and orientation obtained by tracking the locator 1208 to improve the tracking accuracy of the HMD 1200's position and orientation. Accurate position and orientation are crucial for presenting the appropriate virtual scene to the user as they move and rotate in 3D space.

[0090] The HMD 1200 may also include a depth camera assembly (DCA) 1211, which captures data describing depth information about some or all of a local area surrounding the HMD 1200. For this purpose, the DCA 1211 may include a laser radar (LIDAR) or similar device. The depth information can be compared with information from the IMU 1210 to more accurately determine the position and orientation of the HMD 1200 in 3D space.

[0091] The HMD 1200 may also include an eye-tracking system 1214 for determining the orientation and position of the user's eyes in real time. The obtained eye position and orientation also allow the HMD 1200 to determine the user's gaze direction and adjust the image generated by the display system 1280 accordingly. In one example, convergence is determined, i.e., the convergence angle of the user's gaze. The determined gaze direction and convergence can also be used for real-time compensation of visual artifacts based on viewing angle and eye position. Furthermore, the determined convergence and gaze angle can be used for user interaction, highlighting objects, bringing objects to the foreground, creating additional objects or pointers, etc. An audio system may also be provided, for example, including a set of small speakers built into the front body 1202.

[0092] Embodiments and examples of this disclosure may include artificial reality systems, or systems implemented in combination with artificial reality systems. Artificial reality systems adjust sensory information about the external world obtained through sensing (e.g., visual information, audio, tactile (somatosensory) information, acceleration, balance, etc.) in a certain way before presenting it to a user. As a non-limiting example, artificial reality may include virtual reality (VR), augmented reality (AR), mixed reality (MR or hybrid reality), or some combination and / or derivative thereof. Artificial reality content may include entirely generated content or generated content combined with captured (e.g., real-world) content. Artificial reality content may include video, audio, somatic or haptic feedback, or some combination thereof. Any of this content may be presented in a single channel or in multiple channels (e.g., in stereoscopic video that produces a three-dimensional effect for the viewer). Furthermore, in some embodiments and examples, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof for, for example, creating content in artificial reality and / or otherwise using it in artificial reality (e.g., performing activities in artificial reality). Artificial reality systems that deliver artificial reality content can be implemented on a variety of platforms, including wearable displays (e.g., HMDs connected to a host computer system), standalone HMDs, near-eye displays with a shape factor of glasses, mobile devices or computing systems, or any other hardware platform capable of delivering artificial reality content to one or more viewers.

[0093] This disclosure is not limited to the specific embodiments and examples described herein. In fact, various other embodiments, examples, and modifications besides those described herein will be apparent to those skilled in the art based on the foregoing description and drawings. Therefore, such other embodiments, examples, and modifications are intended to fall within the scope of this disclosure. Furthermore, while this disclosure has been described herein in the context of specific embodiments in specific environments for a specific purpose, those skilled in the art will recognize that its usefulness is not limited thereto, and that this disclosure can be advantageously implemented for any number of purposes in any number of environments. Therefore, the claims set forth below should be interpreted in light of the full scope of this disclosure as described herein.

Claims

1. A display device, the display device comprising: A first light source, the first light source being used to emit a first beam of light; Pupil replication light guide; A photonic integrated circuit (PIC), the photonic integrated circuit including a first waveguide for guiding the first light beam; as well as A first reflector and a second reflector, the first reflector and the second reflector being opposite to each other; The first reflector is tiltable when a control signal is applied, and the first reflector has an opening for receiving the first light beam coupled from the first waveguide; The second reflector is configured to reflect at least partially the first beam back to the first reflector after the first beam has propagated through the opening in the first reflector, thereby forming a first collimated beam, which is reflected by the first reflector toward the second reflector at a variable angle. The second reflector is configured to cause at least a portion of the first collimated beam reflected by the first reflector to propagate through the second reflector. The pupil-replicating light guide is configured to couple into the first collimated beam propagating through the second reflector, and to couple out multiple portions of the first collimated beam at a coupling angle. Wherein, the first reflector scans the first collimated beam at an angle; and The second reflector is concave, which collimates the light beam.

2. The display device according to claim 1, wherein, The first reflector includes a microelectromechanical system (MEMS) tiltable reflector.

3. The display device according to claim 1 or 2, further comprising a quarter-wave plate (QWP) located in the optical path between the first reflector and the second reflector, the quarter-wave plate being used to convert the first linear polarization of the first beam into a second orthogonal linear polarization of the first collimated beam, wherein... The second reflector is polarization selective.

4. The display device according to claim 1 or 2 further includes a coupling lens located in the optical path between the PIC and the opening in the first reflector, so as to focus the first light beam through the opening.

5. The display device according to claim 1 or 2, wherein, The PIC includes a coupler for coupling out the first beam from the first waveguide.

6. The display device according to claim 5, wherein, The coupler includes a steering mirror for redirecting the first beam outside the plane of the PIC.

7. The display device according to claim 6, wherein, The steering mirror is concave to focus the first beam of light through the opening in the first reflector.

8. The display device of claim 6, further comprising an auxiliary waveguide extending from the PIC toward the opening in the first reflector for transmitting the first light beam reflected by the steering mirror to the opening in the first reflector.

9. The display device according to claim 1 or 2, wherein, The PIC further includes a second waveguide for guiding the second beam, wherein the second beam coupled from the second waveguide is coupled to the opening in the first reflector; The second reflector is configured to reflect at least a portion of the second beam back to the first reflector after the second beam has propagated through the opening in the first reflector, thereby forming a second collimated beam reflected by the first reflector at a variable angle toward the second reflector, wherein the second reflector is further configured to cause at least a portion of the second collimated beam reflected by the first reflector to propagate through the second reflector.

10. The display device according to claim 1 or 2, wherein, The PIC also includes a combiner element for coupling multiple light sources of different wavelengths into the first waveguide.

11. The display device according to claim 10, wherein, The combiner element includes a multimode interference (MMI) coupler for combining multiple beams emitted by the plurality of light sources.

12. The display device according to claim 10, wherein, The combiner element includes: Multiple ring resonators, each of which couples light from one of the multiple light sources to the first waveguide; or Multiple directional couplers, each of the multiple directional couplers coupling a specific light source from the multiple light sources to the first waveguide.

13. The display device according to claim 10, wherein, The combiner element includes a cavity having an output waveguide coupled thereto and a plurality of input waveguides, each of the plurality of input waveguides coupling light from one of the plurality of light sources to the cavity; The cavity has a nanostructure that provides a non-uniform spatial distribution of effective dielectric constant and is optimized to couple light emitted by each light source to the output waveguide of the combiner element.

14. The display device according to claim 1, wherein, The pupil replication light guide includes an input grating and an output grating. The input grating is used to couple the first collimated beam into the light, and the output grating is used to couple the plurality of portions of the first collimated beam out of the light.

15. The display device of claim 14, further comprising a controller operatively coupled to the first light source and the first reflector, and configured to control the brightness of the first light source in coordination with applying the control signal to the first reflector for scanning the plurality of portions of the first collimated beam to form an image in the angular domain at the viewport of the display device.

16. The display device of claim 14, further comprising a second light source for emitting a second light beam with a wavelength different from that of the first light beam, and the PIC further comprising a combiner element for optically coupling the first light beam and the second light beam into the first waveguide.

17. A method for scanning a light beam, the method comprising: A beam of light in a waveguide of a photonic integrated circuit (PIC) passes through an opening in a first reflector to a second reflector opposite to the first reflector, wherein the first reflector is tiltable when a control signal is applied; The beam of light propagating through the opening is at least partially reflected toward the first reflector, thereby forming a collimated beam; The collimated beam is reflected back to the second reflector at a variable angle by the first reflector; At least a portion of the collimated beam reflected by the first reflector propagates through the second reflector; Applying the control signal to the first reflector causes the first reflector to tilt, thereby scanning the collimated beam propagating through the second reflector at an angle; and The collimated beam propagating through the second reflector is coupled into the pupil replication light guide, and multiple portions of the collimated beam are coupled out of the pupil replication light guide at a coupling angle. The first reflector scans the collimated beam at an angle; and The second reflector is concave, which collimates the light beam.

18. The method of claim 17, further comprising using a coupling lens to couple the beam guided by the waveguide of the PIC to the opening in the first reflector.

19. The method according to claim 18, wherein, The second reflector is polarization selective, and the method further includes converting the polarization of the light beam in the optical path between the first incident on the second reflector and the second incident on the second reflector from a first polarization state to a second polarization state, wherein in the first polarization state the light beam is reflected by the second reflector, and in the second polarization state the light beam propagates through the second reflector.

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