Taut, torsional flexure and a compact drive for, and method of, scanning light using the flexure
View Patent ↗A taut, torsional flexure is used in a compact drive for scanning light and is of beneficial use in a lightweight, compact image projection module, especially for mounting in a housing having a light-transmissive window, the module being operative for causing selected pixels in a raster pattern to be illuminated to produce an image of high resolution of VGA quality in color.
1. A drive for scanning light, comprising:
a support;
a flexure on the support and having torsion portions extending along an axis, and first and second end portions spaced apart along the axis;
a light-reflecting scan mirror on the flexure for joint movement therewith;
means for flexing the flexure in opposite circumferential directions about the axis for oscillating the scan mirror about the axis; and
means integral with the flexure for tensioning the flexure by pulling the first and second end portions apart along the axis to a taut state in which the flexure is flexed.
2. The drive of claim 1 , wherein the flexing means includes a permanent magnet on the flexure, and an electromagnetic coil on the support and operative for generating, in response to a periodic drive signal, a periodic electromagnetic field which interacts with a permanent magnetic field of the magnet to flex the flexure and oscillate the magnet and, in turn, the scan mirror.
3. The drive of claim 2 , wherein the flexure has a support portion intermediate the torsion portions, and wherein the magnet and the scan mirror are mounted on the support portion.
4. The drive of claim 2 , wherein the support has a recessed compartment across which the flexure spans, and wherein the magnet is at least partially received in the compartment.
5. The drive of claim 3 , wherein the support portion extends along the axis for a predetermined distance, and wherein the scan mirror extends along the axis for a distance greater than said predetermined distance and at least partially overhangs the torsion portions.
6. The drive of claim 5 , wherein the scan mirror has a rear portion mounted on the support portion of the flexure, and wherein the rear portion is recessed to provide mechanical clearance for the torsion portions to twist during the flexing of the flexure.
7. The drive of claim 1 , wherein the first end portion is anchored to the support, and wherein the tensioning means is integral with the flexure at the second end portion thereof.
8. The drive of claim 7 , wherein the support has at least one pin, and wherein the one end portion of the flexure has at least one cutout for positioning the at least one pin therein.
9. The drive of claim 7 , wherein the support has a projection, and wherein the tensioning means includes a resilient flap integral with the second end portion of the flexure, and wherein the flap resiliently bears against the projection and pushes the end portions of the flexure away from one another in the taut state.
10. The drive of claim 9 , wherein the flap has a curved shape in the taut state, and wherein the projection has a curved surface of complementary contour to the curved flap.
11. The drive of claim 9 , wherein the flap has a free edge, and wherein the projection has a ridge for engaging the free edge.
12. The drive of claim 9 , wherein the second end portion lies in a plane and frames a rectangular cutout, and wherein the flap has a rectangular shape corresponding to the rectangular cutout, and wherein the flap has a free edge elevated relative to the plane in the taut state and a hinged edge in the plane.
13. The drive of claim 1 , and further comprising at least one vibration damper on the flexure and the support.
14. A tensionable, torsionable flexure for enabling oscillation of a scan mirror, comprising:
a support portion for supporting the scan mirror;
a pair of torsion portions extending along an axis; and
a pair of end portions spaced apart along the axis, one of the end portions having an integral tensioning flap for tensioning the flexure by urging the end portions apart along the axis to a taut state in which the scan mirror is supported for oscillation.
15. The flexure of claim 14 , wherein all the portions are together constituted of a single piece of resilient material.
16. The flexure of claim 14 , wherein the one end portion has a generally planar frame bounding the flap, and wherein the flap has a curved shape in the taut state.
17. A method of scanning light, comprising the steps of:
mounting a light-reflecting scan mirror on a flexure having torsion portions extending along an axis, and first and second end portions spaced apart alone the axis;
flexing the flexure in opposite circumferential directions about the axis for oscillating the scan mirror about the axis; and
self-tensioning the flexure by tensioning the flexure by pulling the first and second end portions apart along the axis to a taut state in which the flexure is flexed.
18. The method of claim 17 , wherein the self-tensioning step is performed by forming a flap out of, and integral with, the second end portion of the flexure.
19. The method of claim 17 , and the step of damping the flexure against vibrations.
20. The flexure of claim 17 , wherein the flexing step is performed by mounting a permanent magnet on the flexure for joint oscillation with the scan mirror, and by applying a periodic drive signal to an electromagnetic coil for generating a periodic electromagnetic field that interacts with a permanent magnetic field of the magnet and causes the magnet and the scan mirror to oscillate about the axis.