Scanning mirror systems and methods of manufacture
Described are scanning micromirror devices, methods of making scanning micromirror devices, two-dimensional optical scanning systems that incorporate 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, which directs reflected light onto a second scanning micromirror device oscillating at a relatively lower frequency, which directs reflected light for projection.
1. A two-dimensional optical scanning system comprising:
a first scanning micromirror device, wherein the first scanning micromirror device comprises:
a first platform coupled to a first base by a plurality of first support flexures, wherein the first platform is oscillatable 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, wherein the stress relief layer is positioned between the first reflector and the first platform;
a first conducting coil positioned on a second side of the first platform opposite to the first side of the first platform, the first conducting coil arranged to apply magnetic forces 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; and
a second scanning micromirror device in optical communication with the first scanning micromirror device, wherein the second scanning micromirror device comprises:
a first frame coupled to a second base by a plurality of second support flexures, wherein the first frame is oscillatable about a second axis;
a second platform coupled to the first frame, wherein the second platform is oscillatable about the second axis together with the first frame;
a second reflector positioned on the second platform;
a second conducting coil positioned on the first frame, the second conducting coil arranged to apply magnetic forces 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.
2. The two-dimensional optical scanning system of claim 1 , wherein the first platform has a thickness of from 100 μm to 500 μm.
3. The two-dimensional optical scanning system of claim 1 , wherein the stress relief layer provides a first stress distribution on the first side of the first platform and wherein the first conducting coil provides a second stress distribution on the second side of the first platform and wherein the first stress distribution and the second stress distribution are opposite.
4. The two-dimensional optical scanning system of claim 1 , wherein the first conducting coil is embedded into the second side of the first platform.
5. The two-dimensional optical scanning system of claim 1 , wherein the first magnetic field source is arranged to provide the first magnetic field oriented orthogonal to the first axis.
6. 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 forces to oscillate the first platform about the first axis or to sense oscillation or position of the first platform about the first axis.
7. The two-dimensional optical scanning system of claim 1 , wherein the first scanning micromirror device further comprises a plurality of conductive traces on the plurality of first support flexures for providing electrical communication with the first conducting coil, and wherein the plurality of conductive traces are arranged on the plurality of first support flexures in a configuration to apply opposite stresses on different sides of the plurality of first support flexures.
8. The two-dimensional optical scanning system of claim 1 , further comprising a hermetic packaging enclosing the first scanning micromirror device for maintaining a lower pressure at the first scanning micromirror device inside the hermetic packaging than outside the hermetic packaging.
9. The two-dimensional optical scanning system of claim 1 , wherein the second scanning micromirror device further comprises a second frame coupled between the first frame and the second platform, wherein the second frame is coupled to the first frame by a plurality of third support flexures and wherein the second frame is oscillatable about the second axis together with the first frame and the second platform.
10. The two-dimensional optical scanning system of claim 9 , wherein the second scanning micromirror device further comprises a temperature sensor incorporated in the second frame.
11. The two-dimensional optical scanning system of claim 9 , wherein the second scanning micromirror device further comprises a strain sensor incorporated in the second frame.
12. The two-dimensional optical scanning system of claim 9 , wherein the second scanning micromirror device further comprises a plurality of piezoelectric actuators incorporated in the second frame, wherein the plurality of piezoelectric actuators are arranged to alter a position of the second platform about a third axis orthogonal to the second axis or to alter a curvature of the second platform.
13. The two-dimensional optical scanning system of claim 1 , wherein the first scanning micromirror device has a first natural resonant frequency of 1 kHz to 10 MHz and wherein the second scanning micromirror device has a second natural resonant frequency of 15 Hz to about 2 kHz.
14. The two-dimensional optical scanning system of claim 1 , further comprising an optical relay providing optical communication between the first scanning micromirror device and the second scanning micromirror device.
15. The two-dimensional optical scanning system of claim 1 , further comprising a light source arranged to direct emitted light to the first reflector.
16. A head-mounted display system comprising:
the two-dimensional optical scanning system of claim 1 ; and
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.
17. The head-mounted display system of claim 16 , further comprising control circuitry operatively coupled to a light source and the first scanning micromirror device and the second scanning micromirror device, wherein the control circuitry is configured to display one or more images by synchronously:
controlling the light source to emit light corresponding to pixels of the one or more images;
controlling current flow in the first conducting coil to induce oscillation of the first platform about the first axis; and
controlling current flow in the second conducting coil to induce oscillation of the second platform about the second axis.
18. A method of projecting an image, the method comprising:
providing a two-dimensional optical scanning system, the two-dimensional optical scanning system comprising:
a first scanning micromirror device, wherein the first scanning micromirror device comprises:
a first platform coupled to a first base by a plurality of first support flexures, wherein the first platform is oscillatable 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, wherein the stress relief layer is positioned between the first reflector and the first platform;
a first conducting coil positioned on a second side of the first platform opposite to the first side of the first platform, the first conducting coil arranged to apply magnetic forces 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; and
a second scanning micromirror device in optical communication with the first scanning micromirror device, wherein the second scanning micromirror device comprises:
a first frame coupled to a second base by a plurality of second support flexures, wherein the first frame is oscillatable about a second axis;
a second platform coupled to the first frame, wherein the second platform is oscillatable about the second axis together with the first frame;
a second reflector positioned on the second platform;
a second conducting coil positioned on the first frame, the second conducting coil arranged to apply magnetic forces 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;
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, wherein the second frequency is smaller than the first frequency; and
illuminating the first reflector of the first scanning micromirror device with a light source to generate reflected light that is directed to the second scanning micromirror device and reflected by the second reflector of the second scanning micromirror device to generate output reflected light.
19. The method of claim 18 , further comprising directing the output reflected light from the second scanning micromirror device to an eyepiece.
20. The method of claim 18 , further comprising synchronously controlling oscillation of the first scanning micromirror device, oscillation of the second scanning micromirror device, and output color and/or intensity of light from the light source.