Patent ID: 12253669

DETAILED DESCRIPTION

Near-eye display systems (such as wearable heads-up displays (WHUDs)) typically include a modulatable light source such as one or more lasers, one or more MEMS mirrors, an optical relay, and a waveguide. Each of the MEMS mirrors receives light output from the light source in series, and each MEMS mirror scans the light over a range of angles to direct the light in a respective direction. The optical relay receives the scanned light from an initial MEMS mirror and introduces a convergence to the light (e.g., via collimation) to focus the light to a point or a line at an exit pupil plane of the optical relay beyond a second MEMS mirror. The second MEMS mirror receives the focused light and scans the light in a direction orthogonal to the direction of light scanned by the initial MEMS mirror to a point or line at an incoupler (IC) of the waveguide. The optical relay enables the MEMS mirrors to be physically separated from the IC to route light onto the MEMS mirrors and into the IC. The incoupler receives the light over a range of input angles, and the light propagates through the waveguide within angles acceptable to achieve total internal reflection (TIR) within the waveguide. The light exits the waveguide at an outcoupler so that the light is projected onto the eye of a user.

However, the optical relay enlarges the footprint of the display system and typically introduces errors into the light path. The optical relay generally includes one or more spherical, aspheric, parabolic, or freeform lenses that receive input light at a given set of angles (which are typically diverging from each other) and output light at a different set of angles (which are typically converging to a point or line). Any of the lenses of the optical relay may contain aberrations that distort the light path. Although aberrations can be minimized by enlarging the lenses, maintaining a compact form factor is an important design consideration for near-eye display systems.

FIGS.1-13illustrate embodiments of a near-eye display system that employs multiple MEMS mirrors in series to receive collimated light and direct the light to provide light having input angles corresponding to a desired field of view at a point or line at an incoupler (IC) of a waveguide without an optical relay. An initial one or more MEMS mirrors accepts collimated light and generates the scan angles. A last MEMS mirror in the series scans at a range of angles proportional to the scan angles generated by the initial MEMS mirror(s) and directs the scanned light back to a spot or a line at the IC. By eliminating the optical relay and replacing it with MEMS mirrors, the light reflects only off planar surfaces, improving the optical performance of the display system compared to a display system employing an optical relay.

In some embodiments, the display system includes two 2-D MEMS mirrors in series. The first 2-D MEMS mirror rotates about two axes and thus has two degrees of freedom (DOF). The first 2-D MEMS mirror receives collimated light from a light source such as one or more lasers and scans the light to the second 2-D MEMS mirror. The second 2-D MEMS mirror receives the scanned light from the first 2-D MEMS mirror and scans the light to a point at the IC. The scan angles of the first and second 2-D MEMS mirrors are a function of the desired field of view (i.e., range of angles of incident light) at the IC, the distance between the first and second 2-D MEMS mirrors, and the distance from the second MEMS mirror to the IC. In some embodiments, the first and second 2-D MEMS mirrors are arranged to be coplanar, thus simplifying their mechanical alignment and electrical connections.

In other embodiments, the display system includes one 1-D MEMS mirror and one 2-D MEMS mirror in series. The 1-D MEMS mirror rotates about a single axis and thus has one DOF. The 1-D MEMS mirror receives collimated light from the light source and scans the light to the 2-D MEMS mirror. The 2-D MEMS mirror receives the scanned light from the 1-D MEMS mirror and scans the light to a line at the IC.

In some embodiments, the display system includes three 1-D MEMS mirrors in series. The first 1-D MEMS mirror rotates about a first axis and has one DOF. The first 1-D MEMS mirror receives collimated light from the light source and scans the light to the second 1-D MEMS mirror. The second 1-D MEMS mirror rotates about a second axis orthogonal to the first axis and has one DOF. The second 1-D MEMS mirror receives scanned light from the first 1-D MEMS mirror and scans the light to the third 1-D MEMS mirror. The third 1-D MEMS mirror rotates about a third axis orthogonal to the first and second axes and has one DOF. The third 1-D MEMS mirror receives scanned light from the second 1-D MEMS mirror and scans the light to a line at the IC.

Thus, to converge the light to a line (i.e., to correct for the divergence of light along one axis), the display system employs one 1-D MEMS mirror and one 2-D MEMS mirror in some embodiments, or three 1-D MEMS mirrors, in other embodiments, with a total of three degrees of freedom. Applications for line inputs to an incoupler of a waveguide are described in U.S. patent application Ser. No. 17/204,308, entitled “Systems, Devices, and Methods for Inputting Light from a Scanning Laser Projector Into a Waveguide”, filed Mar. 17, 2021, the entire disclosure of which is expressly incorporated by reference herein. To converge the light to a point (i.e., to correct for the divergence of light along two axes), the display system employs two 2-D MEMS mirrors, with a total of four degrees of freedom.

FIG.1is a diagram illustrating two views145,150of a display system100including two 2-D MEMS mirrors110,115in series to provide input angles for light to an IC120of a waveguide (not shown) independent of an optical relay in accordance with some embodiments. The first 2-D MEMS mirror110receives collimated light105(referred to herein as light105) generated by a light engine (not shown) including one or more laser diodes (not shown). The first 2-D MEMS mirror110rotates about two axes (e.g., about a first axis in a first plane and a second axis in a second plane orthogonal to the first plane), from a first orientation125shown in the view145to a second orientation135shown in the view150, to scan the light105reflected off the first 2-D MEMS mirror110across a first range of angles to the second MEMS mirror115.

The second 2-D MEMS mirror115receives the light105reflected off the first 2-D MEMS mirror110and rotates about two axes, from a first orientation130shown in the view145to a second orientation140shown in the view150, to scan the light105reflected off the second 2-D MEMS mirror115across a second range of angles to a point at the IC120. The second range of angles through which the second 2-D MEMS mirror115rotates compensates for the first range of angles through which the first 2-D MEMS mirror110rotates such that the incident light105now interacts with the IC120over a range of angles, but only at a single spot. By rotating about their respective axes to steer the light105to intersect at a point at the IC120, the first and second 2-D MEMS mirrors110,115generate angles of the incident light105that determine a FOV at the IC120independent of an optical relay.

In some embodiments, the first 2-D MEMS mirror110and the second 2-D MEMS mirror115rotate about their respective axes at the same frequency but different phases from each other. Because light105received at the first 2-D MEMS mirror110is reflected at the angle of incidence, the second MEMS mirror115is larger than the first 2-D MEMS mirror110in some embodiments so that it is sized to receive the light105reflected off the first 2-D MEMS mirror110. For example, if the first MEMS mirror110moves across 4 degrees, the reflected rays from the first 2-D MEMS mirror110will spread across 8 degrees. Thus, the second 2-D MEMS mirror115is larger than the first 2-D MEMS mirror110to accommodate the fanning out of the rays of incident light105.

In some embodiments, both the first 2-D MEMS mirror110and the second 2-D MEMS mirror115are resonant MEMS mirrors that oscillate such that the rate of change of the angle of the mirrors has a sinusoidal shape. In other embodiments, both the first 2-D MEMS mirror110and the second 2-D MEMS mirror115are linear 2-D MEMS mirrors that have a linear rate of angular change.

FIG.2is a diagram200illustrating relative dimensions of the display system100ofFIG.1in accordance with some embodiments. The first 2-D MEMS mirror110scans light105across a range of angles235to the second 2-D MEMS mirror115. The second 2-D MEMS mirror115is separated from the first 2-D MEMS mirror110by a distance220. The second 2-D MEMS mirror115scans across a range of angles240that are proportional to the angles of the first 2-D MEMS110so that the light105illuminates a spot at the IC120. The IC120is separated from the second 2-D MEMS mirror115by a distance225. The angles250at which light105enters the IC120determine the FOV of the display system100.

To achieve a desired FOV, the components of the display system100are configured according to the following relationships:
FOV=2×(B−A)
B=A×(1+a/b)
ifa=b, thenB=2×A
wherein A=the mirror angle of the first 2-D MEMS mirror110, B=the mirror angle of the second 2-D MEMS mirror115, a=the path length220between the first 2-D MEMS mirror110and the second 2-D MEMS mirror115, and b=the path length225from the second 2-D MEMS mirror115to the IC120.

The above relationships apply to any range of mirror angles. For example, several embodiments are illustrated in Table 1 below.

TABLE 1ParameterEmbodiment 1Embodiment 2Embodiment 3a (mm)6.010.08.0b (mm)3.02.52.5FOV (degrees)10.0 (+/−5.0)10.0 (+/−5.0)10.0mirror angle A of+/−1.25+/−0.625+/−1.0first 2-D MEMS 110mirror angle B of+/−3.75+/−3.125+/−3.0second 2-D MEMS 115

FIG.3is a timing diagram300illustrating rotational angles of the two 2-D MEMS mirrors110,115of the display system100ofFIG.1and the resulting input angles to the IC120in accordance with some embodiments. In the illustrated example, the first 2-D MEMS mirror110receives light105and scans across a range of angles305from +0.625 degrees to −0.625 degrees. The second 2-D MEMS mirror115receives the scanned light105reflected off the first 2-D MEMS mirror110and scans across a range of angles310from −3.125 degrees to +3.125 degrees. The light105reflects off the second 2-D MEMS mirror115and converges at a point on the IC120with input angles315ranging from −5.0 degrees to +5.0 degrees, resulting in a FOV of 10.0 degrees.

FIG.4is a diagram illustrating a display system400having a co-planar arrangement of the two 2-D MEMS mirrors110,115ofFIG.1in accordance with some embodiments. In some embodiments, the first and second 2-D MEMS mirrors110,115are disposed on a common surface of a substrate (not shown), such that the first 2-D MEMS mirror110is substantially coplanar with respect to the second 2-D MEMS mirror115. Such an arrangement of the first and second 2-D MEMS mirrors110,115reduces the volume or form factor of the display system100compared to arrangements in which the first and second 2-D MEMS mirrors110,115are disposed on different substrates and reduces the complexity of electrical connections between the first and second 2-D MEMS mirrors110,115and associated controllers and power supplies (not shown).

In the illustrated example, a window415is disposed adjacent to the incoupler120of a waveguide405. The first 2-D MEMS mirror110receives incident light105and scans the light105to a surface410of the window415. The light105reflects off the surface410to the second 2-D MEMS mirror115. The second 2-D MEMS mirror115scans the light105to a point at the incoupler120. In some embodiments, the window415is omitted from the co-planar arrangement400of the display system100, and instead of reflecting off the surface410of the window415, the light105reflects off a surface420of the waveguide405opposite from the IC120.

FIG.5is a diagram illustrating a display system500including the two 2-D MEMS mirrors110,115in a coplanar configuration in series with a static flat mirror510in accordance with some embodiments. The static flat mirror510is disposed opposite the two 2-D MEMS mirrors110,115such that light105scanned from the first 2-D MEMS mirror110is steered to the static flat mirror510. The light105reflects off the static flat mirror510to the second 2-D MEMS mirror115. The second 2-D MEMS mirror115receives the light105and scans the light105to a point at the incoupler120.

FIG.6is a diagram illustrating an embodiment 600 of the display system500ofFIG.5, in which the two co-planar 2-D MEMS mirrors110,115are integrated into a single package in accordance with some embodiments. Integrating the 2-D MEMS mirrors110,115into a single package (by, e.g., mounting the 2-D MEMS mirrors110,115to a single substrate610) facilitates relative positioning and electrical connections between the 2-D MEMS mirrors110,115while reducing the footprint of the display system500. In some embodiments, the first 2-D MEMS mirror110and the second 2-D MEMS mirror115are included in a single MEMS device. In some embodiments, both the first 2-D MEMS mirror110and the second 2-D MEMS mirror115are resonant MEMS that direct the light105in opposite directions. For example, in an embodiment, the first 2-D MEMS mirror110directs the light105+5 degrees toward the static flat mirror510, which reflects the light105to the second 2-D MEMS mirror115. The second 2-D MEMS mirror115receives the light105from the static flat mirror510and turns the light105−5 degrees to converge at a point at the IC120.

In another embodiment, the first and second 2-D MEMS mirrors110,115are both resonant and yield a line input at the IC120. In one of the scan directions, the first and second 2-D MEMS mirrors110,115direct the light105in opposite directions to converge the light105back to a point. In an orthogonal scan direction, the first and second 2-D MEMS mirrors110,115scan the light105in the same direction such that their collective effect on the light105is additive. For example, in an embodiment, the first 2-D MEMS mirror110receives the light105and turns the light +2.5 degrees in the orthogonal scan direction toward the static flat mirror510. The light105reflects off the static flat mirror to the second 2-D MEMS mirror115. The second 2-D MEMS mirror115receives the light105from the static flat mirror510and turns the light another +2.5 degrees to result in a net angle in the orthogonal direction of +5 degrees, with the light105intersecting at a line at the IC120. Because the scan angle in the orthogonal direction of the first 2-D MEMS mirror110is added to the scan angle in the orthogonal direction of the second 2-D MEMS mirror115to result in a line input at the IC120, each of the first and second 2-D MEMS mirrors110,115rotates a reduced angular distance, resulting in power savings.

FIG.7is a diagram illustrating a display system700including a 1-D MEMS mirror710and a 2-D MEMS mirror715in series to provide a linescan input to the IC120in/out of the page independent of an optical relay in accordance with some embodiments. The 1-D MEMS mirror710receives light105and scans the light105to a reflective surface410of a window415. The reflective surface410reflects the light to the 2-D MEMS mirror715. The 2-D MEMS mirror715receives the reflected light105and scans the light105to a line at the IC120. Thus, the combination of the initial 1-D MEMS mirror710in series with the 2-D MEMS mirror715, which oscillates about a first axis to receive and converge the light105that is spread along the first axis by the initial 1-D MEMS mirror710and oscillates about a second axis orthogonal to the first axis to spread the light along the orthogonal axis, forms a line input in and out of the page at the IC120.

In some embodiments, the light path between the 1-D MEMS mirror710and the 2-D MEMS mirror715is 4.6 mm, the light path between the 2-D MEMS mirror715and the IC120is 3.0 mm, the FOV is 10 degrees, and the light105is a 1.0 mm beam. The 1-D MEMS mirror710is a resonant MEMS with a 1.0 mm aperture in some embodiments. When incorporated into an eyeglass frame, such embodiments result in a pantoscopic angle of 12.0 degrees.

In another embodiment, the 1-D MEMS mirror710is an elliptical mirror or the beam of light105is elliptical. The size of the beam of light105is 2.0 mm×0.8 mm, and the 1-D MEMS mirror710has a 2.0 mm×1.0 mm aperture, while the 2-D MEMS mirror715has a circular 2.0 mm aperture.

FIG.8is a diagram illustrating a display system800including the 1-D MEMS mirror710and the 2-D MEMS mirror715in series transmitting light through a waveplate prism805with a polarizing beam splitter (PBS)810and quarter waveplates815,820to provide input angles for light105in a linescan to the IC120of a waveguide (not shown) independent of an optical relay in accordance with some embodiments. Mounting the 1-D MEMS mirror710and the 2-D MEMS mirror715to the PBS810or waveplate prism805facilitates transmission of the light105through a vacuum for lower-power operation of the 1-D MEMS mirror710and the 2-D MEMS mirror715.

In the illustrated embodiment, various stages of the light path are labeled1-10. At stage “1” of the light path, the incident light705is S-polarized and enters the prism805. The S-polarized light705reflects off the PBS810at stage “2” of the light path toward the quarter waveplate815positioned in front of the 2-D MEMS mirror715. At stage “3” of the light path, the light105passing through the quarter waveplate815is changed to circular polarization. The circularly polarized light105reflects off the 2-D MEMS mirror715at stage “4” of the light path, which scans the light105to a desired range of angles.

As the light105passes back through the quarter waveplate815at stage “5” of the light path, the light105is changed to P-polarization. At stage “6” of the light path, the P-polarized light105passes through the PBS810toward the quarter waveplate820positioned in front of the 1-D MEMS mirror710. At stage “7” of the light path, the P-polarized light105passing through the quarter waveplate820is changed to circular polarization. At stage “8” of the light path, the circularly polarized light105is reflected off the 1-D MEMS mirror710, which scans the light105to a range of angles to direct the light105to a desired line at the IC120. At stage “9” of the light path, the circularly polarized light105passing through the quarter waveplate820is changed to S-polarization. At stage “10” of the light path, the S-polarized light105reflects at the PBS810and is directed to the desired line at the IC120.

In some embodiments, a configuration similar to that illustrated inFIG.8is used with two 2-D MEMS mirrors to steer the light105to a single spot at the IC120. For example, by replacing the 1-D MEMS mirror710with a second 2-D MEMS mirror (not shown), the display system800directs the light105to a point at the IC120rather than a line. In other embodiments, the display system800is implemented with three 1-D MEMS mirrors to direct the light105to a horizontal line at the IC120.

FIG.9is a diagram illustrating a display system900including three 1-D MEMS mirrors910,915,920in series to provide input angles for a horizontal line input at the IC120of a waveguide (not shown) independent of an optical relay in accordance with some embodiments. In the illustrated example, a first (initial) 1-D MEMS mirror910in the series receives the light105and scans in and out of the page to direct the light105to a second (intermediate) 1-D MEMS mirror915. The second 1-D MEMS mirror915receives the light105and scans in the plane of the page to direct the light105to a third (last) 1-D MEMS mirror920. The third 1-D MEMS mirror920receives the light and scans in the plane of the page to direct the light105to a horizontal line that scans in and out of the page at the IC120. Similar to the input to an IC from a linescan relay projector, the horizontal scanned line can be oriented perpendicular to the direction of light propagation in the waveguide (not shown) to minimize double bounce losses.

FIG.10is a diagram illustrating a display system1000including an alternative arrangement of the three 1-D MEMS mirrors ofFIG.9in accordance with some embodiments. The arrangement illustrated inFIG.10employs angles selected to maximize the usable mirror aperture.

FIG.11is a diagram illustrating a near-eye display system1100including three MEMS mirrors1110,1115,1120in series to provide input angles at a line to the IC120of a waveguide1125independent of an optical relay in accordance with some embodiments. The three MEMS mirrors1110,1115,1120operate similar to the three MEMS mirrors910,915,920ofFIG.9.FIG.11illustrates placement of the near-eye display system1100within an eyeglasses frame. In the illustrated example, the near-eye display system1100includes a first 1-D resonant MEMS mirror1110, a second 1-D linear MEMS mirror1115, and a third 1-D linear MEMS mirror1120. The resonant 1-D MEMS mirror1115scans horizontally, resulting in a FOV that is 20 degrees along a horizontal axis and 12 degrees along a vertical axis, with an elliptical beam size that is 1.0 mm×0.6 mm. In some embodiments, the configuration of the near-eye display system illustrated inFIG.11is rotated 90 degrees.

FIG.12is a diagram1200illustrating placement of the near-eye display system1100ofFIG.11in an eyeglasses frame in accordance with some embodiments.

FIG.13is a flow diagram of a method1300of rotating multiple MEMS mirrors in series to direct light to a spot or a line at an incoupler of a waveguide independent of an optical relay. In some embodiments, the method1300is implemented using the display systems illustrated inFIGS.1,2, and4-12. At block1302, an initial MEMS mirror in a series of MEMS mirrors rotates across a first range of angles at a first frequency and a first phase. In some embodiments, the initial MEMS mirror is a 2-D MEMS mirror, and in other embodiments, the initial MEMS mirror is a 1-D MEMS mirror. At block1304, the initial MEMS mirror receives collimated light and scans the light across a range of angles corresponding to the first range of angles to a last MEMS mirror115in the series. In embodiments in which both the initial MEMS mirror and the last MEMS mirror are 1-D MEMS mirrors, an intermediate MEMS mirror is disposed in the light path between the initial MEMS mirror and the last MEMS mirror. In such embodiments, the intermediate MEMS mirror receives the scanned light from the initial MEMS mirror and scans the light to the last MEMS mirror.

At block1306, the last MEMS mirror in the series rotates across a second range of angles at the first frequency and a second phase. At block1308, the last MEMS mirror in the series receives scanned light (either from the initial MEMS mirror or from the intermediate MEMS mirror) and directs the light to a spot or a line at the IC120of a waveguide independent of an optical relay.

In some embodiments, certain aspects of the techniques described above may be implemented by one or more processors of a processing system executing software. The software comprises one or more sets of executable instructions stored or otherwise tangibly embodied on a non-transitory computer readable storage medium. The software can include the instructions and certain data that, when executed by the one or more processors, manipulate the one or more processors to perform one or more aspects of the techniques described above. The non-transitory computer readable storage medium can include, for example, a magnetic or optical disk storage device, solid state storage devices such as Flash memory, a cache, random access memory (RAM) or other non-volatile memory device or devices, and the like. The executable instructions stored on the non-transitory computer readable storage medium may be in source code, assembly language code, object code, or other instruction format that is interpreted or otherwise executable by one or more processors.

A computer readable storage medium may include any storage medium, or combination of storage media, accessible by a computer system during use to provide instructions and/or data to the computer system. Such storage media can include, but is not limited to, optical media (e.g., compact disc (CD), digital versatile disc (DVD), Blu-Ray disc), magnetic media (e.g., floppy disc, magnetic tape, or magnetic hard drive), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (e.g., read-only memory (ROM) or Flash memory), or microelectromechanical systems (MEMS)-based storage media. The computer readable storage medium may be embedded in the computing system (e.g., system RAM or ROM), fixedly attached to the computing system (e.g., a magnetic hard drive), removably attached to the computing system (e.g., an optical disc or Universal Serial Bus (USB)-based Flash memory), or coupled to the computer system via a wired or wireless network (e.g., network accessible storage (NAS)).

Note that not all of the activities or elements described above in the general description are required, that a portion of a specific activity or device may not be required, and that one or more further activities may be performed, or elements included, in addition to those described. Still further, the order in which activities are listed are not necessarily the order in which they are performed. Also, the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. Moreover, the particular embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. No limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the claims below.