Scanning mirror system and method of manufacture

Abstract

A scanning micromirror device, a method for fabricating a scanning micromirror device, a two-dimensional optical scanning system incorporating a scanning micromirror device, and a method for projecting light and images using a two-dimensional optical scanning system are described. The disclosed two-dimensional optical scanning system can incorporate a first scanning micromirror device oscillating at a relatively higher frequency that directs reflected light onto a second scanning micromirror device oscillating at a relatively lower frequency that directs reflected light for projection.

Description

[Technical field]

[0001] This application claims the benefit of and priority to U.S. Provisional Application No. 62 / 962,168, filed January 16, 2020, and U.S. Provisional Application No. 63 / 058,384, filed July 29, 2020, both of which are incorporated by reference in their entireties herein. [Background technology]

[0002] Digital micromirror devices have been used in image projection systems. For example, U.S. Patent No. 6,856,446 describes a micromirror array in which many individually hinged and controllable micromirror elements can be used to control the direction of reflected light to project an array of digital pixels. These devices often require the use of a color wheel or three individual pixel arrays for different colors to project a full-color image, and generally use large and high-intensity light sources, limiting the compactness of the projection system. Summary of the Invention [Means for solving the problem]

[0003] The present disclosure relates to a two-dimensional scanning micromirror system and its use in image projection systems and methods. The disclosed two-dimensional scanning micromirror system is advantageously useful for driving reflected light in two directions and can be significantly more robust and compact than other reflective scanning systems. The disclosed two-dimensional scanning micromirror system can utilize two separate uniaxial micromirror devices to scan a beam of light in orthogonal directions.

[0004] In a first aspect, an optical scanning system is disclosed. The optical scanning system may comprise one or more scanning micromirror devices, which are useful for projecting and scanning a beam of light. In some cases, two scanning micromirror devices may be used in sequence, i.e., a first scanning micromirror device for scanning along a first direction and a second scanning micromirror device in optical communication with the first scanning micromirror device for scanning along a second direction. Optionally, a hermetic package may enclose the scanning micromirror device to maintain a lower pressure on the scanning micromirror device inside the hermetic package than outside the hermetic package. In some embodiments, an optical relay may be used to provide optical communication between the first scanning micromirror device and the second scanning micromirror device. Exemplary optical relays include, but are not limited to, those described by U.S. Provisional Application No. 62 / 964,508, filed January 22, 2020, which is incorporated herein by reference. The optical scanning system may include a light source arranged to direct emitted light onto a first reflector of the first scanning micro-mirror device. The light source may be modulatable to allow control over the color and / or intensity as a function of time and / or projected position of the light reflected from the scanning micro-mirror device, enabling image display.

[0005] An exemplary scanning micro-mirror device comprises a first platform coupled to a first base by a plurality of first support flexures such that the first platform is capable of oscillating about a first axis, a stress relief layer positioned on a first side of the first platform, a first reflector positioned on the first side of the first platform with the stress relief layer positioned between the first reflector and the first platform, a first conductive coil positioned on a second side of the first platform opposite the first side of the first platform, the first conductive coil arranged to apply a magnetic force to the first platform about the first axis, and a first magnetic field source arranged to apply a first magnetic field to the first platform. Useful scanning micro-mirror devices include, but are not limited to, those having a natural resonant frequency between 1 kHz and 10 MHz.

[0006] The scanning micromirror device of this aspect may use a thick platform in some cases. A thick platform may allow the reflector of the micromirror device to be robust and have good flatness despite the inclusion of other components in the platform. In some embodiments, the first platform may have a thickness of 100 μm to 500 μm. The use of a stress relief layer may also improve the flatness of the reflector by allowing the stresses on different sides of the platform to offset each other, resulting in good flatness of the reflector. In some embodiments, the stress relief layer provides a first stress distribution on a first side of the first platform, while the first conductive coil provides a second stress distribution on a second side of the first platform. Thus, the first stress distribution and the second stress distribution may be opposite each other and at least partially offset from each other. In some cases, the first conductive coil may be embedded within the second side of the first platform (e.g., positioned within a trench or multiple trenches on the first platform) or may be positioned across and supported by the second side of the first platform (e.g., as a partial covering layer).

[0007] The scanning micro-mirror device may be actuated using electromagnetic actuation such that a current passing through the conductive coil interacts with a magnetic field, and the current is oscillatory in nature to drive the oscillatory force and / or oscillation of the platform. For example, a first magnetic field source may be arranged to provide a first magnetic field oriented orthogonal to a first axis. The scanning micro-mirror device may further comprise a plurality of conductive traces on the plurality of support flexures, such as to provide electrical communication with the conductive coil. In some cases, the conductive traces may apply strain on the support flexures, and thus it may be desirable for the conductive traces to be arranged on the plurality of support flexures in a configuration to apply opposing stresses on different sides of the plurality of first support flexures, which may be useful to avoid, reduce, or limit nonlinear effects.

[0008] In some cases, additional components may be included in the scanning micro-mirror device, such as actuation components or sensor components. In one example, the scanning micro-mirror device may further comprise one or more piezoelectric actuators arranged to apply a force to oscillate the first platform about a first axis or to sense the oscillation or position of the first platform about the first axis.

[0009] Another exemplary scanning micro-mirror device includes a first frame coupled to a second base by a plurality of second support flexures such that the first frame can oscillate about a second axis, a second platform coupled to the first frame such that the second platform can oscillate with the first frame about the second axis, a second reflector positioned on the second platform, a second conductive coil positioned on the first frame, the second conductive coil arranged to apply a magnetic force to the first frame about the second axis, and a second magnetic field source arranged to apply a second magnetic field to the first frame. Useful scanning micro-mirror devices include, but are not limited to, those having a natural resonant frequency of 15 Hz to about 2 kHz.

[0010] In some examples, the scanning micro-mirror device may further comprise a second frame coupled between the first frame and the second platform such that the second frame is coupled to the first frame by a plurality of third support flexures and such that the second frame can oscillate with the first frame and the second platform about a second axis. In some examples, such an intermediate frame may include other components such as sensors or actuators. For example, in some embodiments, the scanning micro-mirror device may further comprise a temperature sensor integrated into the second frame. Optionally, the second scanning micro-mirror device may further comprise a strain sensor integrated into the second frame. Optionally, the scanning micro-mirror device may further comprise a plurality of piezoelectric actuators integrated into the second frame, such as piezoelectric actuators arranged to modify or sense the position of the second platform about a third axis orthogonal to the second axis, or to modify or sense the curvature of the second platform.

[0011] Methods of projecting an image are also described herein. An exemplary method includes providing a two-dimensional optical scanning system, such as a two-dimensional optical scanning system, comprising a first scanning micro-mirror device and a second scanning micro-mirror device in optical communication with the first scanning micro-mirror device, inducing a first oscillation of the first scanning micro-mirror device at a first frequency, inducing a second oscillation of the second scanning micro-mirror device at a second frequency, the second frequency being optionally less than the first frequency, and illuminating a first reflector of the first scanning micro-mirror device with a light source to generate reflected light that is directed and reflected by a second reflector of the second scanning micro-mirror device to the second scanning micro-mirror device to generate output reflected light. The first and second scanning micro-mirror devices may independently correspond to different scanning micro-mirror devices described herein. Optionally, the method of this aspect may further include directing the output reflected light from the second scanning micro-mirror device to an eyepiece. The method of this aspect may further include synchronously controlling the oscillation of the first scanning micromirror device, the oscillation of the second scanning micromirror device, and the output color and / or intensity of the light from the light source. Such a configuration may be useful for rendering images or image fields and sequences of images or image fields.

[0012] The disclosed scanning micro-mirror device and projection method may be advantageously employed in a head-mounted display system. An exemplary head-mounted display system may comprise a two-dimensional optical scanning system and an eyepiece comprising one or more optical components configured to receive and redirect light reflected or output from the two-dimensional optical scanning system to one or two eyes of a user. The head-mounted display system may include a control circuit operatively coupled to the light source and the scanning micro-mirror device of the two-dimensional optical scanning system to enable display of an image. For example, the control circuit may be configured to display one or more images by controlling the light source to emit light corresponding to pixels of one or more images in synchronization, controlling a current in a first conductive coil of the first scanning micro-mirror device to induce oscillation of the first scanning micro-mirror device or its platform, and controlling a current in a second conductive coil of the second scanning micro-mirror device to induce oscillation of the second scanning micro-mirror device or its platform.

[0013] In another aspect, a method of fabricating a scanning micromirror device using microfabrication techniques is disclosed. Specific exemplary methods are described below in the detailed description and figures. Furthermore, additional features, advantages, and embodiments are described below in the detailed description, figures, and claims. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 provides a schematic diagram of an exemplary image projection system.

[0015] [Figure 2A] Figure 2A shows a bottom side schematic view of an exemplary scanning micro-mirror device, Figure 2B shows a cross-sectional schematic view of an exemplary scanning micro-mirror device, and Figure 2C shows a cross-sectional schematic view of an exemplary scanning micro-mirror device in a sealed or vacuum package. [Figure 2B] Figure 2A shows a bottom side schematic view of an exemplary scanning micro-mirror device, Figure 2B shows a cross-sectional schematic view of an exemplary scanning micro-mirror device, and Figure 2C shows a cross-sectional schematic view of an exemplary scanning micro-mirror device in a sealed or vacuum package. [Figure 2C] Figure 2A shows a bottom side schematic view of an exemplary scanning micro-mirror device, Figure 2B shows a cross-sectional schematic view of an exemplary scanning micro-mirror device, and Figure 2C shows a cross-sectional schematic view of an exemplary scanning micro-mirror device in a sealed or vacuum package.

[0016] [Figure 3A] Figure 3A shows a top-side schematic view of an exemplary scanning micromirror device. Figure 3B shows a cross-sectional schematic view of an exemplary scanning micromirror device in cross section. Figures 3C and 3D provide schematic views of an exemplary scanning micromirror device to illustrate additional features. [Figure 3B] Figure 3A shows a top-side schematic view of an exemplary scanning micromirror device. Figure 3B shows a cross-sectional schematic view of an exemplary scanning micromirror device in cross section. Figures 3C and 3D provide schematic views of an exemplary scanning micromirror device to illustrate additional features. [Figure 3C] Figure 3A shows a top-side schematic view of an exemplary scanning micromirror device. Figure 3B shows a cross-sectional schematic view of an exemplary scanning micromirror device in cross section. Figures 3C and 3D provide schematic views of an exemplary scanning micromirror device to illustrate additional features. [Figure 3D] Figure 3A shows a top-side schematic view of an exemplary scanning micromirror device. Figure 3B shows a cross-sectional schematic view of an exemplary scanning micromirror device in cross section. Figures 3C and 3D provide schematic views of an exemplary scanning micromirror device to illustrate additional features.

[0017] [Figure 4] FIG. 4 provides an overview of an exemplary method for projecting an image using a two-dimensional scanning micromirror device.

[0018] [Figure 5A] 5A, 5B, 5C, 5D, 5E, 5F, and 5G provide schematic illustrations of various points in the fabrication process for making an exemplary scanning micromirror device. [Figure 5B] 5A, 5B, 5C, 5D, 5E, 5F, and 5G provide schematic illustrations of various points in the fabrication process for making an exemplary scanning micromirror device. [Figure 5C] 5A, 5B, 5C, 5D, 5E, 5F, and 5G provide schematic illustrations of various points in the fabrication process for making an exemplary scanning micromirror device. [Figure 5D] 5A, 5B, 5C, 5D, 5E, 5F, and 5G provide schematic illustrations of various points in the fabrication process for making an exemplary scanning micromirror device. [Figure 5E] 5A, 5B, 5C, 5D, 5E, 5F, and 5G provide schematic illustrations of various points in the fabrication process for making an exemplary scanning micromirror device. [Figure 5F] 5A, 5B, 5C, 5D, 5E, 5F, and 5G provide schematic illustrations of various points in the fabrication process for making an exemplary scanning micromirror device. [Figure 5G] 5A, 5B, 5C, 5D, 5E, 5F, and 5G provide schematic illustrations of various points in the fabrication process for making an exemplary scanning micromirror device.

[0019] [Figure 6A] 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H provide schematic illustrations of various points in a fabrication process for making another embodiment of a scanning micromirror device. [Figure 6B]6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H provide schematic illustrations of various points in a fabrication process for making another embodiment of a scanning micromirror device. [Figure 6C] 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H provide schematic illustrations of various points in a fabrication process for making another embodiment of a scanning micromirror device. [Figure 6D] 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H provide schematic illustrations of various points in a fabrication process for making another embodiment of a scanning micromirror device. [Figure 6E] 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H provide schematic illustrations of various points in a fabrication process for making another embodiment of a scanning micromirror device. [Figure 6F] 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H provide schematic illustrations of various points in a fabrication process for making another embodiment of a scanning micromirror device. [Figure 6G] 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H provide schematic illustrations of various points in a fabrication process for making another embodiment of a scanning micromirror device. [Figure 6H] 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H provide schematic illustrations of various points in a fabrication process for making another embodiment of a scanning micromirror device.

[0020] [Figure 7A] 7A, 7B, 7C, 7D, 7E, 7F, and 7G provide schematic illustrations of various points in an exemplary fabrication / assembly process for vacuum packaging of a scanning micromirror device. [Figure 7B]7A, 7B, 7C, 7D, 7E, 7F, and 7G provide schematic illustrations of various points in an exemplary fabrication / assembly process for vacuum packaging of a scanning micromirror device. [Figure 7C] 7A, 7B, 7C, 7D, 7E, 7F, and 7G provide schematic illustrations of various points in an exemplary fabrication / assembly process for vacuum packaging of a scanning micromirror device. [Figure 7D] 7A, 7B, 7C, 7D, 7E, 7F, and 7G provide schematic illustrations of various points in an exemplary fabrication / assembly process for vacuum packaging of a scanning micromirror device. [Figure 7E] 7A, 7B, 7C, 7D, 7E, 7F, and 7G provide schematic illustrations of various points in an exemplary fabrication / assembly process for vacuum packaging of a scanning micromirror device. [Figure 7F] 7A, 7B, 7C, 7D, 7E, 7F, and 7G provide schematic illustrations of various points in an exemplary fabrication / assembly process for vacuum packaging of a scanning micromirror device. [Figure 7G] 7A, 7B, 7C, 7D, 7E, 7F, and 7G provide schematic illustrations of various points in an exemplary fabrication / assembly process for vacuum packaging of a scanning micromirror device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Detailed Description Described herein are scanning micromirror devices, methods of making scanning micromirror devices, two-dimensional optical scanning systems incorporating scanning micromirror devices, and methods of projecting light and images using two-dimensional optical scanning systems. The disclosed two-dimensional optical scanning systems can incorporate a first scanning micromirror device oscillating at a relatively higher frequency that directs reflected light onto a second scanning micromirror device oscillating at a relatively lower frequency that directs reflected light for projection.

[0022] The disclosed scanning micromirror devices exhibit features that provide advantages for two-dimensional optical scanning and image projection. For example, some of the scanning micromirror devices are constructed to achieve a high degree of flatness of the reflective elements of the scanning mirror while allowing good or precise control over the oscillation of the scanning micromirror. Some of the scanning micromirror devices can incorporate sensor and control elements to allow monitoring of conditions such as temperature, distortion, or position. Some of the scanning micromirror devices can incorporate actuators to alter the relative position of the reflective elements, change or achieve a high or higher degree of flatness, etc. The disclosed scanning micromirror devices can employ electromagnetic actuation, where a conductive coil is located on the platform of the scanning micromirror device to apply a magnetic force to induce oscillation of the scanning micromirror device.

[0023] In some cases, the disclosed scanning micro-mirror devices can be much thicker than conventional scanning micro-mirror devices, which may allow for improved flatness of the reflector on the platform of the scanning micro-mirror device. In some embodiments, the thickness of the platform of the scanning micro-mirror device may be in the range of 100 μm to 500 μm, such as 100 μm to 150 μm, 150 μm to 200 μm, 200 μm to 250 μm, 250 μm to 300 μm, 300 μm to 350 μm, 350 μm to 400 μm, 400 μm to 450 μm, 450 μm to 500 μm, etc., or any value between the ranges shown. In some cases, a thicker platform may increase the power requirements to drive oscillation, but operation at natural resonance may limit the power requirements. However, the increased power requirements are offset by the ability to maintain the flatness of the reflector, which may otherwise result in undesirable image or projection artifacts.

[0024] The disclosed scanning micro-mirror devices can be used for image projection, such as for projecting light for viewing by a user. In some cases, the disclosed scanning micro-mirror devices and image projection systems are useful for head-mounted display devices, such as due to their compact size and ability to project high quality images using low power operation.

[0025] 1 provides a schematic diagram of an exemplary image projection system 100. The image projection system 100 comprises a first scanning micro-mirror device 105 including a first reflector 110 and a second scanning micro-mirror device 115 including a second reflector 120. The image projection system 100 also includes a light source 125 arranged in optical communication with the first reflector 110 to direct light 130 from the light source 125 to the first reflector 110, where it is reflected towards the second reflector 120 and output therefrom for projection. The motion of the first scanning micro-mirror device 105 and the second scanning micro-mirror device 115 can be driven in such a manner to direct the output reflected light 130 to a projection plane 135. By using the oscillating motion of first scanning micromirror device 105 and second scanning micromirror device 115 to control the color, intensity, and timing of light 130 output by light source 125, output reflected light 140 can generate an image at projection plane 135. Using repeated scanning, a sequence of images and / or videos may be projected.

[0026] In some embodiments, the first scanning micro-mirror device 105 may oscillate about a first axis such that the output reflected light 140 may form a series of horizontal (left to right and right to left) passes, while the second scanning micro-mirror device 115 may oscillate about a second axis such that the output reflected light 140 may also oscillate vertically from top to bottom and / or bottom to top across the projection plane 135. The oscillation frequency along the horizontal direction may be very fast, for example, in the range of 1 kHz to 10 MHz. Some projection systems may use an oscillation pattern along the vertical direction that is sawtooth or triangular shaped, which may be useful for creating regularly spaced horizontal passes in one vertical direction (e.g., from top to bottom), but a sinusoidal oscillation pattern may also be used. The oscillation frequency along the vertical direction may be slower, for example, in the range of 15 Hz to 2 kHz. If only top-to-bottom repeated projections are desired, a blanking period can be used in which no light is generated by the light source 125 while the second scanning micromirror device 115 oscillates in the upward direction. However, in some cases, both top-to-bottom and bottom-to-top projections can be used. Blanking periods can also be used on the extremes of the horizontal dimension to avoid projections at the side edges of the projection plane 135.

[0027] It should be understood that the references to horizontal (or left-to-right and right-to-left) and vertical (or bottom-to-top and top-to-bottom) directions are merely examples of markings with reference to the orientation of the projection plane 135 shown in Figure 1. Other configurations in which horizontal and vertical markings are switched or other markings are used are also contemplated within the scope of this disclosure.

[0028] The image projection system 100 may be a component of an optical projector that may be used, for example, to project still or video images at a projection plane. In some cases, the image projection system 100 may be a component of a head mounted display device and / or may be used to couple projected light into an eyepiece, such as an eyepiece of a head mounted display device. The projection plane 135 may correspond to the eyepiece or the retina of a user in some examples. The image projection system 100 may optionally include projection optics, such as mirrors, lenses, collimators, filters, gratings, or the like, not shown in FIG. 1, positioned, for example, in the optical path between the light source 125 and the projection plane 135. In some cases, an optical relay 145 comprising multiple reflective and / or focusing elements, or the like, may be used between the first scanning micro-mirror device 105 and the second scanning micro-mirror device 115 to direct light reflected from the first mirror 110 onto the second mirror 120. Light source 125 may be a monochromatic or polychromatic light source and may include, for example, a light emitting diode or laser source that may have a switchable or modulatable output at a high rate, such as up to 100 MHz. Optionally, light source 125 may comprise or support multiple individually modulatable light sources, such as different color (e.g., red, green, blue) outputs.

[0029] FIG. 2A provides a schematic diagram of an exemplary scanning micro-mirror device 200. The scanning micro-mirror device 200 may comprise silicon or other materials that allow for patterning and processing according to known micro-fabrication techniques. The scanning micro-mirror device 200 includes a base 205 and a platform 210 that is coupled to the base 205 by a number of support flexures 215. The support flexures 215 are constructed and arranged to allow oscillation of the platform 210 about an axis 220 as shown diagrammatically by arrow 245. The particular configuration of the support flexures 215 shown in FIG. 2A may also be referred to as a torsion beam in some cases due to the way in which they support oscillation of the platform 210 about an axis 220 by partial rotation relative to the base 205. 2A as a frame that surrounds the other components, the base 205 may extend in other directions or be positioned differently relative to the platform 210, such as, for example, beneath the first platform 210. A reflector 225 may be positioned on the opposing surface of the platform 210 as shown in FIG.

[0030] The scanning micro-mirror device 200 also includes conductive traces 230 that form conductive coils 235 in the platform 210. The conductive coils 235 can be used to apply forces (e.g., magnetic / electromagnetic forces) to the platform 210 to induce oscillation of the platform 210 about the axis 220. The conductive coils 235 can have any suitable number of turns. In some cases, the conductive traces 230, which provide a way to pass current from a current source through the contacts 240 to the conductive coils 235, can add stiffness to the support flexures 215. Because the support flexures 215 can flex and / or move during oscillation with rotation of the support flexures 215, the additional stiffness imparted by the conductive traces 230 can be time dependent as the excess stiffness can depend on the scan angle, which can result in some nonlinearity for the oscillation of the platform 210 about the axis 220. A thinner and / or narrower conductive trace 230 may offset or minimize nonlinearities, but a smaller or thinner conductive trace 230 may increase the resistance and power consumption of the device, and therefore in some embodiments it may be advantageous for the conductive trace 230 to be wider so as to occupy as much of the surface of the support flexure 215 as practical (i.e., the maximum full width). Additionally, conductive traces 230 can be positioned on both the side and the opposite side of the scanning micromirror device 200 shown in FIG. 2A to balance perturbations. In addition to electromagnetic actuation achieved using conductive coils 235, other actuators such as piezoelectric actuators, electrostatic actuators, or the like may be used. In some cases, piezoelectric or electrostatic actuators can be used for position sensing, angular scanning, or oscillation of the platform 210.

[0031] FIG. 2B shows a schematic cross-sectional view of an exemplary scanning micro-mirror device 200. It should be understood that the configurations shown in FIGS. 2A and 2B are merely examples and may not be to scale. In FIG. 2B, axis 220 extends in and out of the plane with oscillation of platform 210 shown diagrammatically by arrow 245. A magnetic source 250 is shown positioned to provide a magnetic field at platform 210. The magnetic field can interact with a current flowing through conductive coil 235 to impart a force on platform 210 to induce oscillation, such as by passing an alternating current through conductive coil 235. In addition to or as an alternative to electromagnetic actuation, other forms of actuators, such as piezoelectric or electrostatic actuators, can also be used. A reflector 225 is shown on the opposite side of platform 210. Reflector 225 may comprise, for example, a metallic or dielectric reflector, or a combination.

[0032] The presence of the conductive coil 235 may apply stress to the platform 210, which may result in perturbations to the flatness of the reflector 225. To balance the impact of the stress imparted by the conductive coil 235, a stress relief layer 255 may be positioned between the reflector 225 and the platform 210. The stress relief layer 255 may apply a stress to the platform 210 opposite that of the conductive coil 235. The stress relief layer 255 and the conductive coil 235 may be of the same material and / or have the same volume on the platform 210 to minimize or reduce the total applied stress and limit perturbations to the flatness of the reflector 225.

[0033] The configuration of scanning micro-mirror device 200 may be useful for relatively high frequency oscillations, such as, for example, in the range of 1 kHz to 10 MHz. To reduce the power consumed to drive the actuation and oscillation of platform 210, the device may be operated at its resonant frequency, which may result in a quality factor (Q) that may amplify the displacement achieved through actuation. Thus, the natural resonant frequency for oscillation of platform 210 about axis 220 may be in the range of 1 kHz to 10 MHz.

[0034] Further improvement in quality factor can be achieved in some cases by using vacuum or hermetic packaging. FIG. 2C shows a cross-sectional schematic of the scanning micromirror device 200 including vacuum packaging. The vacuum packaging may include a transparent top component 260 and a bottom component 265. The top component 260 may be transparent to allow light transmission therethrough and may optionally include an anti-reflective coating on one or more surfaces to minimize surface reflections. Exemplary materials for the top component 260 may include glass or crystalline materials. The bottom component 265 is positioned adjacent to the magnetic source 250 and may comprise a transparent or non-transparent material. In some embodiments, the bottom component 265 may comprise silicon. The top component 260 and the bottom component 265 may be sealed to the base 205 using glass frit paste or the like.

[0035] 3A and 3B provide top and cross-sectional schematic views, respectively, of another exemplary scanning micro-mirror device 300. The scanning micro-mirror device 300 can comprise silicon or other materials that allow for patterning and processing according to known microfabrication techniques. The scanning micro-mirror device 300 includes a base 305 and a first frame 310 coupled to the base 305 by a number of support flexures 315. The support flexures 315 are constructed and arranged to allow oscillation of the first frame 310, or components therein or associated therewith, about an axis 320, as shown diagrammatically by arrow 345. The scanning micro-mirror device 300 also includes a platform 325 and a second frame 330 positioned between the platform 325 and the first frame 310. A conductive coil 335 is shown positioned on the first frame 310, and a reflector 340 is shown positioned on the platform 325. Conductive traces (not shown) may pass across the support flexures 315 to provide electrical current to and / or from the conductive coil 335. The conductive coil 335 may have any suitable number of turns.

[0036] A magnetic source 350 is shown positioned to provide a magnetic field at the first frame 310. The magnetic field can interact with a current flowing through the conductive coil 335 to impart a force on the first frame 310 to induce oscillation of the first frame 310, the second frame 330, and the platform 325 about the axis 320, such as by passing an alternating current through the conductive coil 335. In addition to or as an alternative to electromagnetic actuation, other forms of actuators, such as piezoelectric or electrostatic actuators, can also be used.

[0037] The reflector 340 is shown positioned on the platform 325. The reflector 225 may comprise, for example, a metallic reflector, or a dielectric reflector, or a combination. In the configuration shown in FIG. 3A, the reflector 340 has a length along a direction parallel to the axis 320 that is longer than along a direction perpendicular to the axis 320. Such a configuration may be useful to allow light received at the reflector 340 to oscillate along the direction of the axis 320, which may occur as a result of light received at the reflector 340 coming from another scanning micromirror device, causing the light to oscillate.

[0038] The configuration of the scanning micro-mirror device 300 may be useful for relatively low frequency oscillation, such as, for example, in the range of 15 Hz to 2 kHz. To reduce the power consumed to drive the actuation and oscillation of the platform 325, the device may be operated at its resonant frequency, which may result in a quality factor (Q) that may amplify the displacement achieved through actuation. Thus, the natural resonant frequency for the first frame 310, the second frame 330, and the platform 325 about the axis 320 may be in the range of 15 Hz to 2 kHz. The support flexures 315 may be constructed to support such an oscillatory motion.

[0039] The use of a second frame 330 between the first frame 310 and the platform 325 allows for the inclusion of additional components within the scanning micro-mirror device 300. For example, as shown in FIG. 3C, a resistor 355 can be positioned on the second frame 330. Such a resistor 355 can be used for evaluation of the temperature of the scanning micro-mirror device 300, such as by using a resistor 355 having a resistance that is a function of temperature (i.e., a thermistor). The conductive access line used for electrical communication with the resistor 355 is not shown in FIG. 3C.

[0040] In another embodiment, a piezoelectric actuator 360 can be positioned on the second frame 330 as shown in FIG. 3D. Again, conductive access lines used for electrical communication with the piezoelectric actuator 360 are not shown in FIG. 3D. The piezoelectric actuator 360 can be used to sense and / or control the flatness and / or position of the platform 325 about the second axis 365. The piezoelectric actuator 360 can be used as a strain sensor to sense the position of the second frame 330. For example, the piezoelectric actuator 360 generates a voltage when the second frame 330 and the platform 325 deform relative to the axis 365, providing a method for detecting the position or flatness. Voltages can be applied to the piezoelectric actuators 360 to modify the tilt of the second frame and platform 325 relative to the axis 365 such that all of the piezoelectric actuators 360 produce deformations that result in deflections in corresponding directions about the axis 365 (e.g., causing one end of the frame 330 to be tip-up and the other end of the frame 330 to be tip-down). Alternatively, voltages can be applied to the piezoelectric actuators 360 to modify the curvature of the second frame and platform 325 relative to the axis 365 such that the piezoelectric actuators 360 produce deformations on opposite sides of the axis 365 that result in coordinated deflections about the axis 365 (e.g., causing one end of the frame 330 to be tip-up and the other end of the frame 330 to be tip-up as well).

[0041] In some cases, scanning micro-mirror device 300 can be packaged in vacuum or hermetic packaging similar to that described above for scanning micro-mirror device 200. Because scanning micro-mirror device 300 can be configured for relatively lower frequency operation, such packaging is optional and may not be preferred for all embodiments.

[0042] 4, an overview of an exemplary method 400 is depicted. Method 400 may correspond to, for example, a method of projecting an image using multiple scanning micro-mirror devices, etc. In block 402, a two-dimensional optical scanning system (such as, for example, image projection system 100) is provided, such as a two-dimensional optical scanning system including a first scanning micro-mirror device and a second scanning micro-mirror device. The scanning micro-mirror device may comprise, for example, one or more of scanning micro-mirror devices 200 or scanning micro-mirror devices 300 or each of scanning micro-mirror devices 200 and 300.

[0043] Method 400 includes steps 404, 406 in which different resonant oscillations of the scanning micromirror devices are induced. Although steps 404 and 406 are shown as inducing oscillation of a first scanning micromirror device and then inducing oscillation of a second scanning micromirror device, the oscillations of the scanning micromirror devices may be induced in any order or simultaneously. Inducing oscillation of the scanning micromirror device may include passing a current, such as an alternating current, through a conductive coil of the scanning micromirror device.

[0044] In block 408, a reflector of the first scanning micro-mirror device is illuminated using a controllable light source, which may be a polychromatic light source, or the like. The reflector of the first scanning micro-mirror device may reflect light from the light source to generate a reflected light that is directed to a reflector of the second scanning micro-mirror device. An optical relay may optionally be positioned between the first scanning micro-mirror device and the second scanning micro-mirror device to provide optical communication, such as in a folded beam configuration, which may be useful for reducing or minimizing the size of the optical scanning system. The reflector of the second scanning micro-mirror device may reflect light from the first scanning micro-mirror device to generate an output reflected light.

[0045] The output reflected light may be directed to an eyepiece, such as an eyepiece of a head mounted image display device, at block 410. The output optics may be incorporated between the eyepiece and the second scanning micromirror device. Exemplary optics include lenses, reflectors, filters, gratings, prisms, or the like.

[0046] Aspects of the present invention can be further understood by the following non-limiting examples. EXAMPLES

[0047] Example 1 Example 1: Fabrication of a scanning micromirror device with an intermediate frame This example provides an overview of a processing scheme for fabricating a scanning micromirror device. Various details are described in this example to enable one skilled in the art to understand an exemplary process used to fabricate a scanning micromirror device useful with the image projection system, head mounted display system, and two-dimensional scanning system described herein. It should be understood that conventional processes may be used for some processing steps. Not all processing steps may be described in detail in this example so as not to obscure other disclosed aspects. It should be understood that the figures described in this example are for illustrative purposes and may not be to scale.

[0048] 5A-5G provide schematic diagrams of various points in a fabrication process for making a scanning micromirror device. In this example, the fabrication process begins with a silicon-on-insulator (SOI) wafer 500, as shown in FIG. 5A. As a first step, the location of the conductive coil is established using a photolithography process, which can indicate the location on the SOI wafer 500 where the conductive coil can be integrated into the platform of the resulting scanning micromirror device. The silicon can be etched after the photolithography step to create recessed locations for the conductive coil, followed by stripping of any photoresist. The wafer can undergo a dry oxidation process followed by deposition of a silicon nitride layer (SiN), such as using a low pressure chemical vapor deposition method, to create an insulator that separates the conductive coil from the silicon wafer. A metal seed layer 510 can be deposited in the recesses, such as a tantalum / copper seed layer, by a sputtering process, for example. At this point, the wafer may appear similar to that shown in FIG. 5A, where the SOI wafer is identified by reference numeral 500, the recess is identified by reference numeral 505, and the metal seed layer is identified by reference numeral 510.

[0049] Following this, a copper layer can be deposited on the metal seed layer for the bulk of the conductive coil, such as using an electrochemical deposition process. A chemical mechanical polishing or planarization process can be used to remove excess copper and the metal seed layer to create a flat surface for the device, resulting in copper-filled recesses. At this point, the wafer can appear similar to that shown in FIG. 5B, where the copper-filled recesses are identified by reference numeral 515.

[0050] A plasma enhanced chemical vapor deposition process can be used to passivate the surface to create a silicon nitride / silicon oxide layer. Vias 520, which provide access points for electrical contact to the conductive coil, can be established by a photolithography process, followed by etching the vias and stripping any remaining photoresist. At this point, the wafer may appear similar to that shown in FIG. 5C, where the vias are identified by reference numeral 520.

[0051] A second metal layer 525, such as a titanium / molybdenum layer, can be deposited to provide conductivity. The second metal layer can provide electrical connection to the conductive coil in the via 520 established above. The second metal layer 525 can be subjected to photolithography to define where the second metal layer 525 is to be retained, followed by an etching process (e.g., a wet etching process) and a photoresist stripping process. Another passivation layer 530 (e.g., silicon oxide) can be created using a plasma enhanced chemical vapor deposition process or the like. At this point, the wafer can appear similar to that shown in FIG. 5D, where the second metal layer is identified by reference numeral 525 and the passivation layer is identified by reference numeral 530.

[0052] A photolithography process may be used to define the location of the platform of the scanning micromirror device, the top passivation layer may be thinned or removed by an etching process, and any remaining photoresist may be stripped. For the reflector of the scanning micromirror device, a reflective layer 535, such as an aluminum layer, may be deposited and patterned using a series of deposition, photolithography, etching, and photoresist stripping processes. A passivation layer 530 may again be created (e.g., by plasma enhanced chemical vapor deposition). At this point, the wafer may appear similar to that shown in FIG. 5E, where the reflector is identified by reference numeral 535 and the passivation layer is identified by reference numeral 540.

[0053] A photolithography process can be used to define a second via 540 for connecting to a second metal layer to allow for wire bonding and the like. The via can be etched, followed by stripping any remaining photoresist. Another photolithography process can be used to define the area between and surrounding the platform of the scanning micromirror device, the supporting flexure, and (if applicable) a frame positioned between the base and the platform. The recess can be established by one or more etching processes and a photoresist stripping process. At this point, the wafer can appear similar to that shown in FIG. 5F, where the via for the second metal layer is identified by reference numeral 545.

[0054] A protective layer, such as parylene, is deposited over the device, followed by stripping of the protective layer from the back side, protecting the top side while allowing processing of the bottom side of the device. In this example, the back side can be subjected to photolithography, followed by one or more etching processes to remove the silicon oxide layer, the silicon nitride layer, the handle wafer, and the buried oxide layer. The parylene and any remaining photoresist layer can be stripped. Finally, the wafer can be diced, such as by a stealth or laser dicing process. The resulting wafer 550 can appear similar to that shown in FIG. 5G, where the scanning micromirror platform is identified by reference numeral 555.

[0055] It should be understood that the steps outlined in this example are merely one example of a process for fabricating components of a scanning micromirror device, and that other processes or orders of steps may be used. Example 2 Example 2: Fabrication of a scanning micromirror device, conductive coil, and stress relief layer

[0056] This example provides an overview of a processing scheme for fabricating a scanning micromirror device. Various details described in this example will enable one skilled in the art to understand an exemplary process used to fabricate a scanning micromirror device useful with the image projection system, head mounted display system, and two-dimensional scanning system described herein. It should be understood that conventional processes may be used for some processing steps. Not all processing steps may be described in detail in this example so as not to obscure other disclosed aspects. It should be understood that the figures described in this example are for illustrative purposes and may not be to scale.

[0057] 6A-6H provide schematic diagrams of various points in the fabrication process for making a scanning micromirror device. In this example, the fabrication process begins with a silicon wafer 600 that is polished on both sides. As a first step, the location of the conductive coil is established using a photolithography process, which may indicate the location on the wafer where the conductive coil may be integrated into the platform of the resulting scanning micromirror device. The silicon may be etched after the photolithography step to create recessed locations for the conductive coil, followed by stripping of any photoresist. The wafer may undergo a dry oxidation process, followed by deposition of a silicon nitride layer (SiN), such as using a low pressure chemical vapor deposition method, to create an insulator that separates the conductive coil from the silicon wafer. A metal seed layer 610, such as a tantalum / copper seed layer, may be deposited in the recesses, for example, by a sputtering process. At this point, the wafer may appear similar to that shown in FIG. 6A, where the silicon wafer is identified by reference numeral 600, the recess is identified by reference numeral 605, and the metal seed layer is identified by reference numeral 610.

[0058] Following this, a copper layer can be deposited over the metal seed layer for the bulk of the conductive coil, such as using an electrochemical deposition process. A chemical mechanical polishing or planarization process can be used to remove excess copper and the metal seed layer and create a flat surface for the device, resulting in copper-filled recesses 605. At this point, the wafer can appear similar to that shown in FIG. 6B, where the copper-filled recesses are identified by reference numeral 615.

[0059] A plasma enhanced chemical vapor deposition process can be used to passivate the surface to create a silicon nitride / silicon oxide layer. Vias, which provide access points for electrical contact to the conductive coil, can be established by a photolithography process, followed by etching the vias and stripping any remaining photoresist. At this point, the wafer may appear similar to that shown in FIG. 6C, where the vias are identified by reference numeral 620.

[0060] A second metal layer 625, such as a titanium / molybdenum layer, can be deposited to provide conductivity. The second metal layer can provide electrical connection to the conductive coil in the via established above. The second metal layer 625 can be subjected to photolithography to define where the second metal layer 625 is to be retained, followed by an etching process (e.g., a wet etching process) and a photoresist stripping process. Another passivation layer 630 (e.g., silicon oxide) can be created using a plasma enhanced chemical vapor deposition process or the like. At this point, the wafer can appear similar to that shown in FIG. 6D, where the second metal layer is identified by reference numeral 625 and the passivation layer is identified by reference numeral 630.

[0061] All of the above steps can be used to create a conductive coil on the back side of a silicon wafer, as shown in Figures 6A-6D. It should be understood that the reference terms "back side and front side" or "top side and bottom side" are merely examples describing opposite sides of the wafer, and that these terms are not intended to be limiting. Additionally, it should be understood that the steps outlined are merely one example of a process for fabricating components of a scanning micromirror device, and that other processes or sequences of steps may be used.

[0062] A stress relief layer 635, such as a copper layer, and a reflective layer 640, such as an aluminum layer, can be deposited on the front side of the wafer using photolithography steps, etching steps, and photoresist stripping processes, etc., to define the locations of the stress relief layer 635, the reflective layer 640, and the platform. A passivation process (e.g., silicon oxide and / or silicon nitride layer deposition by plasma enhanced chemical vapor deposition) can optionally be used to isolate the stress relief layer and the reflective layer from each other and from the silicon wafer. At this point, the wafer may appear similar to that shown in FIG. 6E, where the stress relief layer is identified by reference numeral 635 and the reflective layer is identified by reference numeral 640.

[0063] A photolithography process can be used to define a second via to connect to the second metal layer. The via can be etched, followed by stripping any remaining photoresist. A third metal layer 645, such as aluminum, can be deposited into the via with photolithography, etching, and photoresist stripping used to pattern the third metal layer. At this point, the wafer may appear similar to that shown in FIG. 6F, where the third metal layer is identified by reference numeral 645.

[0064] The overall shape of the scanning micromirror platform is established by identifying areas of the passivation layer on the back side of the device for selective removal by photolithographically patterning the back side and etching the passivation layer, which can then be followed by stripping of any excess photoresist. In this case, the passivation layer on the back side is significantly thicker and therefore it may be difficult to remove them by etching from the front side, so they can be selectively removed from the back side at this stage, if desired. A protective layer such as parylene is deposited over the device, which can then be followed by stripping of the protective layer from the front side in preparation for etching through the silicon wafer. At this point, the wafer may appear similar to that shown in FIG. 6G, where the parylene protective layer is identified by reference numeral 650.

[0065] Finally, the overall shape of the scanning micromirror platform can be established from the front side of the device by lithographically patterning and etching the passivation layer, followed by etching the silicon through the parylene layer, which is then subsequently peeled off. Finally, the wafer can be diced, if desired, such as by a stealth or laser dicing process. The resulting wafer 660 can have features similar to those shown in FIG. 6H. In some cases, the wafer can be diced later, such as after vacuum package assembly, as described below in Example 3. Example 3 Example 3: Sealed or vacuum packaging for scanning micromirror devices

[0066] This example provides an overview of making a vacuum package for a scanning micromirror device. Various details are described in this example to enable a person skilled in the art to understand an exemplary process used to make a scanning micromirror device that is useful with the image projection system, head mounted display system, and two-dimensional scanning system described herein. It should be understood that conventional processes can be used for some processing steps. Not all processing steps may be described in detail in this example so as not to obscure other disclosed aspects. It should be understood that the figures described in this example are for illustrative purposes and may not be to scale.

[0067] 7A-7G provide schematic diagrams of various points in the fabrication / assembly process for vacuum packaging of a scanning micromirror device. In this example, fabrication of the top packaging begins with a silicon wafer that is polished on both sides. As a first step, the wafer can be drilled and / or machined to create the holes and recesses needed to accommodate the scanning micromirror device and its motion. A cleaning process can be used to prepare for the next part of the process. At this point, the top packaging wafer can appear similar to that shown in FIG. 7A, where the silicon wafer is identified by reference numeral 700, the through-holes are identified by reference numeral 705, and the recesses are identified by reference numeral 710.

[0068] The glass frit paste can be screen printed across the top of the silicon wafer to bond and seal a transparent cap, such as a glass (e.g., borosilicate glass) or crystalline cap. At this point, the top packaging may appear similar to that shown in FIG. 7B, where the transparent cap is identified by reference numeral 715 and the glass frit paste is identified by reference numeral 720. The transparent cap can be coated on one or both sides with an anti-reflective coating.

[0069] Processing of the bottom packaging may begin similarly with a silicon wafer 725 that has been polished on both sides. A top side recess 730 may be photolithographically patterned and etched, followed by stripping of any excess photoresist. Locations for holes on the bottom side may also be patterned via photolithography. At this point, the bottom packaging wafer may appear similar to that shown in FIG. 7C, where the silicon wafer is identified by reference numeral 725, the top side recess is identified by reference numeral 730, and the patterned photoresist on the back side is identified by reference numeral 735.

[0070] The bottom side may be partially etched to create recesses for holes to be later fully etched, followed by stripping of any excess photoresist. The devices may be protected by a parylene protective layer 745 or the like, which may be removed from the front side for further processing. At this point, the bottom packaging wafer may appear similar to that shown in FIG. 7D, where the partial etch is identified by reference numeral 740 and the protective layer is identified by reference numeral 745.

[0071] The top side is lithographically patterned to define the deeper recesses 750, and locations for holes 755 can be partially etched from the bottom side in a previous step. The wafer can then be etched to create the second recesses 750 and complete the holes 755, followed by stripping of any excess photoresist and protective layer material. The second recesses 750 can be useful, for example, to accommodate the motion of the platform of a scanning micromirror device. At this point, the bottom packaging wafer can appear similar to that shown in FIG. 7E, where the deeper recesses are identified by reference numeral 750 and the holes are identified by reference numeral 755.

[0072] The top and bottom packaging can be assembled into a scanning micro-mirror device, for example, prepared according to Example 2 above. For the top side, glass frit paste 770 can be screen printed onto the bottom side of the top packaging for bonding 765 to the top side of the scanning micro-mirror device 760. At this point, the assembly can appear similar to that shown in FIG. 7F, where the scanning micro-mirror device is identified by reference numeral 760, the top packaging is identified by reference numeral 765, and the glass frit paste is identified by reference numeral 770.

[0073] For the bottom side, glass frit paste 780 can be screen printed onto the top side of bottom packaging 775 for bonding to the bottom side of scanning micro-mirror device 760. The assembled vacuum packaged scanning micro-mirror device may appear similar to that shown in FIG. 7G, where the scanning micro-mirror device is identified by reference numeral 760, the top packaging is identified by reference numeral 765, the bottom packaging is identified by reference numeral 775, and the glass frit paste is identified by reference numeral 780. As shown, the holes in the bottom packaging are positioned to align the third metal layer onto the bottom side of the scanning micro-mirror device.

[0074] Although the above description of creating a vacuum package refers to a scanning micromirror device prepared according to Example 2 above, other scanning micromirror devices can benefit from and be positioned within the vacuum package according to this example. For example, U.S. Provisional Patent Application No. 63 / 034,884, filed June 4, 2020, and incorporated herein by reference, describes two-dimensional microelectromechanical system mirrors having electromagnetic actuation, and these micromirror devices can be similarly packaged using the vacuum packaging components and techniques described above. Such a system may utilize a single micromirror device for two-dimensional scanning, as opposed to other systems described herein that employ a first scanning mirror device for oscillation along a first direction and a second scanning mirror device for oscillation along a second direction perpendicular to the first direction. In one specific example, the scanning micromirror device 760 may comprise a two-dimensional microelectromechanical system mirror including a base, a first platform coupled to the base by a plurality of first support flexures, a second platform coupled to the first platform by a plurality of second support flexures, and a second platform including a reflector. The first platform may be capable of oscillating about a first axis, which may be useful for controlling the oscillation of the reflected light in a first direction. The second platform may be capable of oscillating about a second axis orthogonal to the first axis, which may be useful for controlling the oscillation of the reflected light in a second direction, which may be orthogonal (e.g., perpendicular) to the first direction. The first platform, the second platform, and the plurality of second support flexures together may exhibit a first resonance having a first resonant frequency, with the first resonance corresponding to an oscillatory motion of at least the first platform, the second platform, and the plurality of second support flexures about the first axis.The first platform, the second platform, and the plurality of second support flexures together may exhibit or further exhibit a second resonance having a second resonant frequency (the second frequency is greater than the first frequency), the second resonance corresponding to oscillatory motion of the at least second platform about the second axis. The first platform, the second platform, and the plurality of second support flexures together may exhibit or further exhibit a third resonance having a third resonant frequency (the third frequency is twice the second frequency), the third resonance corresponding to oscillatory motion of the at least second platform about the first axis. Computing Device Components

[0075] A computing device may be incorporated as part of the systems described above, such as image projection systems, head mounted display systems, and two-dimensional scanning systems. A computing device may be useful for implementing aspects of the methods and systems described above. For example, a computing device may be useful for controlling modulation of a light beam. A computing device may also be useful for controlling the orientation and / or oscillation of a scanning mirror. A computing device may also be useful for controlling the application of voltage or current. An exemplary computing device comprises hardware elements that may be electrically coupled (or otherwise communicate) via a bus. The hardware elements may include one or more processors, including but not limited to one or more general purpose processors and / or one or more special purpose processors (such as digital signal processing chips, graphics acceleration processors, video decoders, and / or the like), one or more input devices, which may include but are not limited to a mouse, a touch screen, a keyboard, a remote control, voice input, and / or the like, and one or more output devices, which may include but are not limited to a display device, a printer, a speaker, a servo, a linear actuator, a rotary actuator, and the like.

[0076] A computing device may further comprise (and / or be in communication with) one or more non-transitory storage devices, which may include, but are not limited to, disk drives, drive arrays, optical storage devices, solid-state storage devices such as solid-state drives ("SSD"), random access memory ("RAM"), and / or read-only memory ("ROM"), which may be programmable, flash-updateable, and / or the like. Such storage devices may be configured to implement any suitable data storage, including, but not limited to, various file systems, database structures, and / or the like.

[0077] The computing device may also include a communications subsystem, which may include, but is not limited to, a modem, a network card (wireless or wired), an infrared communication device, a wireless communication device, and / or a chipset (Bluetooth® device, Bluetooth® Low Energy or BLE device, 802.11 device, 802.15.4 device, WiFi device, WiMax device, cellular communication device, etc.), a G.hn device, and / or the like. The communications subsystem may enable data to be exchanged with a network, other computer systems, and / or any other device described herein. In many embodiments, the computing device will further comprise a working memory, which may include a RAM or ROM device as described above.

[0078] A computing device may also include software elements shown as currently residing in working memory, including an operating system, device drivers, executable libraries, and / or other code, such as one or more application programs, that may be equipped with computer programs provided by various embodiments and / or that may be designed to implement methods and / or configure systems provided by other embodiments as described herein. Simply by way of example, one or more procedures described for the methods discussed above may be implemented as code and / or instructions executable by a computer (and / or a processor within the computer), and in certain aspects such code and / or instructions may then be used to configure and / or adapt the computer (or other device) to perform one or more operations in accordance with the methods described, or for operation of the devices and systems described.

[0079] A set of these instructions and / or code may be stored on a non-transitory computer-readable storage medium, such as the non-transitory storage devices described above. In some cases, the storage medium may be incorporated within a computer system, such as the computing device described above. In other embodiments, the storage medium may be provided within an installation package, separate from the computer system (e.g., a removable medium such as a compact disc, or a cloud or network-based storage system), such that the storage medium may be used to program, configure, and / or adapt a computer with the instructions / code stored thereon. These instructions may take the form of executable code that is executable by a computing device or a component thereof, and / or may take the form of source and / or installable code upon compilation and / or installation on the computing device (e.g., using any of a variety of commonly available compilers, installation programs, compression / decompression utilities, etc.), which then takes the form of executable code.

[0080] It will be apparent to those skilled in the art that substantial variations may be made according to specific requirements. For example, customized hardware may also be used and / or particular elements may be implemented in hardware, software (including portable software such as applets), or both. Furthermore, connection to other computing devices, such as network input / output devices, may also be employed.

[0081] As described above, in one aspect, some embodiments may employ a computing device to perform the methods according to various embodiments. According to one set of embodiments, some or all of the procedures of such methods are performed by the computing device in response to the processor executing one or more sequences of one or more instructions contained in a working memory (which may be embedded in an operating system and / or other code, such as an application program). Such instructions may be read into the working memory from another computer-readable medium, such as one or more non-transitory storage devices. By way of example only, execution of a sequence of instructions contained in the working memory may cause the processor to perform one or more procedures of the methods described herein.

[0082] The terms "machine-readable medium", "computer-readable storage medium", and "computer-readable media", as used herein, refer to any medium involved in providing data that causes a machine to operate in a tangible manner. These media may be non-transitory. In an embodiment implemented using a computing device, various computer-readable media may be involved in providing instructions / code to a processor for execution and / or may be used to store and / or carry such instructions / code. In many implementations, computer-readable media are physical and / or tangible storage media. Such media may take the form of non-volatile media or volatile media. Non-volatile media include, for example, optical and / or magnetic disks, such as non-transitory storage devices. Volatile media include dynamic memory, such as, but not limited to, working memory.

[0083] Common forms of physical and / or tangible computer readable media include, for example, floppy disks, flexible disks, hard disks, magnetic tapes or any other magnetic media, CD-ROMs, any other optical media, any other physical media with a pattern of marks, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip or cartridge, or any other medium from which a computer can read instructions and / or code. Network-based and cloud-based storage systems can also be useful forms of computer readable media.

[0084] Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution. By way of example only, the instructions may initially be carried on a magnetic and / or optical disk of a remote computer. The remote computer may load the instructions into its dynamic memory and send the instructions as signals over a transmission medium to be received and / or executed by the computing device.

[0085] The communications subsystem (and / or its components) generally receive signals and a bus may then carry the signals (and / or the data, instructions, etc. carried by the signals) to a working memory, from which a processor retrieves and executes the instructions. The instructions received by the working memory may optionally be stored on a non-transitory storage device either before or after execution by the processor.

[0086] Furthermore, it should be understood that the components of a computing device may be distributed. For example, some processing may be performed in one location using a first processor, while other processing may be performed by another processor remote from the first processor. Optionally, the systems described herein may include multiple independent processors that may exchange instructions or issue commands or provide data to each other. Other components of a computing device may be distributed as well. Thus, a computing device may be interpreted as a distributed computing system that performs processing at multiple locations. In some instances, a computing device may be interpreted as a single computing device, such as a distinct laptop, desktop computer, or the like, depending on the context.

[0087] While preferred embodiments of the invention have been shown and described, it will be apparent that the invention is not limited to these embodiments alone. Numerous modifications, changes, variations, substitutions, and equivalents will become apparent to those skilled in the art without departing from the spirit and scope of the invention, as set forth in the claims.

Claims

1. 1. A two-dimensional optical scanning system comprising: A first scanning micro-mirror device, the first scanning micro-mirror device comprising: a first platform coupled to a first base by a plurality of first support flexures, the first platform being oscillable about a first axis; a stress relief layer positioned on a first side of the first platform; a first reflector positioned on a first side of the first platform, the stress relief layer being positioned between the first reflector and the first platform; a first conductive coil positioned on a second side of the first platform opposite the first side of the first platform, the first conductive coil arranged to apply a magnetic force about the first axis to the first platform; a first magnetic field source arranged to apply a first magnetic field to the first platform; a first scanning micromirror device comprising: a second scanning micro-mirror device in optical communication with the first scanning micro-mirror device, the second scanning micro-mirror device comprising: a first frame coupled to a second base by a plurality of second support flexures, the first frame being capable of oscillating about a second axis; a second platform coupled to the first frame and disposed to be surrounded by the first frame, the second platform being oscillable together with the first frame about the second axis; a second reflector positioned on the second platform; and a second conductive coil positioned on the first frame, the second conductive coil arranged to apply a magnetic force about the second axis to the first frame; and a second magnetic field source arranged to apply a second magnetic field to the first frame; and a second scanning micromirror device comprising: A two-dimensional optical scanning system comprising:

2. The two-dimensional optical scanning system of claim 1 , wherein the first platform has a thickness of between 100 μm and 500 μm.

3. 2. The two-dimensional optical scanning system of claim 1, wherein the stress relief layer provides a first stress distribution on a first side of the first platform and the first conductive coil provides a second stress distribution on a second side of the first platform, the first stress distribution and the second stress distribution being opposing.

4. The first conductive coil is embedded within a second side of the first platform.

2. The two-dimensional optical scanning system of claim 1.

5. The two-dimensional optical scanning system of claim 1 , wherein the first magnetic field source is arranged to provide the first magnetic field that is oriented orthogonal to the first axis.

6. 2. The two-dimensional optical scanning system of claim 1, wherein the first scanning micromirror device further comprises one or more piezoelectric actuators arranged to apply a force to oscillate the first platform about the first axis or to sense the oscillation or position of the first platform about the first axis.

7. 2. The two-dimensional optical scanning system of claim 1, wherein the first scanning micro-mirror device further comprises a plurality of conductive traces on the plurality of first support flexures for providing electrical communication with the first conductive coil.

8. 10. The two-dimensional optical scanning system of claim 1, further comprising a hermetic packaging enclosing the first scanning micro-mirror device to maintain a lower pressure on the first scanning micro-mirror device inside the hermetic packaging than outside the hermetic packaging.

9. 2. The two-dimensional optical scanning system of claim 1, wherein the second scanning micro-mirror device further comprises a second frame coupled between the first frame and the second platform, the second frame coupled to the first frame by a plurality of third support flexures, and the second frame, together with the first frame and the second platform, is capable of oscillating about the second axis.

10. The two-dimensional optical scanning system of claim 9 , wherein the second scanning micro-mirror device further comprises a temperature sensor integrated into the second frame.

11. The two-dimensional optical scanning system of claim 9 , wherein the second scanning micro-mirror device further comprises a strain sensor integrated into the second frame.

12. 10. The two-dimensional optical scanning system of claim 9, wherein the second scanning micromirror device further comprises a plurality of piezoelectric actuators mounted on the second frame, the plurality of piezoelectric actuators being arranged to modify a position of the second platform or a curvature of the second platform about a third axis perpendicular to the second axis.

13. 2. The two-dimensional optical scanning system of claim 1, wherein the first scanning micro-mirror device has a first natural resonant frequency between 1 kHz and 10 MHz, and the second scanning micro-mirror device has a second natural resonant frequency between 15 Hz and 2 kHz.

14. The two-dimensional optical scanning system of claim 1 , further comprising an optical relay providing optical communication between the first scanning micro-mirror device and the second scanning micro-mirror device.

15. The two-dimensional optical scanning system of claim 1 , further comprising a light source arranged to direct light emitted onto the first reflector.

16. 1. A method for projecting an image, the method comprising: A two-dimensional optical scanning system is provided, the two-dimensional optical scanning system comprising: A first scanning micro-mirror device, the first scanning micro-mirror device comprising: a first platform coupled to a first base by a plurality of first support flexures, the first platform being oscillable about a first axis; a stress relief layer positioned on a first side of the first platform; a first reflector positioned on a first side of the first platform, the stress relief layer being positioned between the first reflector and the first platform; a first conductive coil positioned on a second side of the first platform opposite the first side of the first platform, the first conductive coil arranged to apply a magnetic force about the first axis to the first platform; a first magnetic field source arranged to apply a first magnetic field to the first platform; a first scanning micromirror device comprising: a second scanning micro-mirror device in optical communication with the first scanning micro-mirror device, the second scanning micro-mirror device comprising: a first frame coupled to a second base by a plurality of second support flexures, the first frame being capable of oscillating about a second axis; a second platform coupled to the first frame and disposed to be surrounded by the first frame, the second platform being oscillable together with the first frame about the second axis; a second reflector positioned on the second platform; and a second conductive coil positioned on the first frame, the second conductive coil arranged to apply a magnetic force about the second axis to the first frame; and a second magnetic field source arranged to apply a second magnetic field to the first frame; and a second scanning micromirror device comprising: and inducing a first oscillation of the first scanning micromirror device at a first frequency; inducing a second oscillation of the second scanning micromirror device at a second frequency, the second frequency being less than the first frequency; and illuminating a first reflector of the first scanning micro-mirror device with a light source to generate reflected light, the reflected light being directed to the second scanning micro-mirror device and reflected by a second reflector of the second scanning micro-mirror device to generate an output reflected light; A method comprising:

17. The method of claim 16 , further comprising directing the output reflected light from the second scanning micromirror device to an eyepiece.

18. 17. The method of claim 16, further comprising synchronously controlling oscillation of the first scanning micro-mirror device, oscillation of the second scanning micro-mirror device, and an output color and / or intensity of light from the light source.

19. The method of claim 16, wherein the two-dimensional optical scanning system comprises the two-dimensional optical scanning system according to any of claims 1-15.

20. The two-dimensional optical scanning system according to any one of claims 1 to 15, an eyepiece comprising one or more optical components configured to receive and redirect light reflected by the second scanning micromirror device to one or two eyes of a user; A head mounted display system comprising:

21. and a control circuit operatively coupled to a light source, the first scanning micro-mirror device, and the second scanning micro-mirror device, the control circuit synchronously controlling: controlling the light source to emit light corresponding to pixels of the one or more images; controlling a current in the first conductive coil to induce oscillation of the first platform about the first axis; controlling a current in the second conductive coil to induce oscillation of the second platform about the second axis; configured to display one or more images by 21. The head mounted display system of claim 20.

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