Frequency tunable resonant scanner with auxiliary arms

• US 7,516,896 B2
• Filed: 02/18/2005
• Issued: 04/14/2009
• Est. Priority Date: 08/05/1999
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Helsel, Mark P., Wine, David W.
• Primary Examiner(s): Le; Thien M.
• Assistant Examiner(s): Taylor; April A
• Application Number:
  US11/062,037
• Publication Number:
  US 20050139678A1
• Time in Patent Office: 1,516 Days
• Field of Search: 235/454, 235/462.01, 235/462.25, 235/462.28
• US Class Current: 235/462.25
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G02B 27/0176 characterised by mechanical features

Abstract

A MEMs scanning device has a variable resonant frequency. In one embodiment, the MEMs device includes a flexible arm that extends from an oscillatory body. An electrical field applies a force to the flexible arm, thereby bending the flexible arm to change the moment of inertia of the oscillatory body and a secondary mass carried by the flexible arm. The shifted combined center of mass changes the resonant frequency of the MEMs device. In another embodiment, an absorptive material forms a portion of a torsional arm that supports the oscillatory body. The mechanical properties of the absorptive material can be varied by varying the concentration of a gas surrounding the absorptive material. The varied mechanical properties change the resonant frequency of the scanning device. A display apparatus includes the scanning device and the scanning device scans about two or more axes, typically in a raster pattern. Various approaches to controlling the frequency responses of the scanning device are described, including active control of MEMs scanners and passive frequency tuning.

Claims

1. A method for aberration compensation in a scanned beam system comprising:

scanning a beam of light across a field of view;

receiving pixel values;

producing the beam by modulating at least one light source at clocked pixel times so as to produce illumination spots in desired locations in the field of view, wherein the field of view includes a projection surface, wherein the projection surface includes a human retina; and

clocking pixels at times corresponding to an aberration map so as to compensate for aberrations in the system.

2. A method for aberration compensation in a scanned beam system comprising:

scanning a beam of light across a field of view; and

clocking pixels at times corresponding to an aberration map so as to compensate for aberrations in the system, wherein the aberration is optical aberration, and wherein the optical aberration arises at least partly from curvature of an object in the field of view.

3. A method for aberration compensation in a scanned beam system, comprising:

scanning a beam of light across a field of view; and

clocking pixels having values corresponding to an aberration map so as to compensate for aberrations in the system, wherein the pixel values are determined by averaging second pixel values corresponding to an image with no aberration.

4. The method for aberration compensation in a scanned beam system of claim 3:

wherein the averaging is weighted averaging corresponding to a deviation in beam position in the field of view arising from the aberration.

5. A method for aberration compensation in a scanned beam system, comprising:

scanning a beam of light across a field of view; and

clocking pixels having values corresponding to an aberration map so as to compensate for aberrations in the system, wherein clocking pixels having values corresponding to an aberration map includes determining for each pixel an actual beam location, the location being determined according to the aberration;

determining for each pixel a plurality of desired second beam locations adjacent to the actual beam location; and

performing averaging of second pixel values corresponding to the desired second beam locations to determine the pixel value.

6. A method for aberration compensation in a scanned beam system, comprising:

scanning a beam of light across a field of view;

clocking pixels having values corresponding to an aberration map so as to compensate for aberrations in the system;

receiving second pixel values; and

producing the beam by modulating at least one light source at pixel values so as to produce illumination spots in the field of view, the location of the illumination spots corresponding to the actual beam location and the pixel values calculated from adjacent non-illuminated spots corresponding to the received second pixel values.

7. The method for aberration compensation in a scanned beam system of claim 6:

wherein the field of view includes a projection surface.

8. The method for aberration compensation in a scanned beam system of claim 7:

wherein the projection surface includes a display screen.

9. The method for aberration compensation in a scanned beam system of claim 7:

wherein the projection surface includes a human retina.

10. A method for aberration compensation in a scanned beam system, comprising:

scanning a beam of light across a field of view;

clocking pixels having values corresponding to an aberration map so as to compensate for aberrations in the system;

detecting at least a portion of beam light reflected from the field of view from a plurality of illuminated spots;

comparing the locations of the plurality of illuminated spots to a plurality of desired spot locations; and

averaging the values of the detected plurality of spots to produce a second value corresponding to each of the desired spot locations.

11. The method for aberration compensation in a scanned beam system of claim 10, further comprising:

outputting the image.

12. The method for aberration compensation in a scanned beam system of claim 11:

wherein outputting the image includes transmitting the image to a decoder for further processing.

13. The method for aberration compensation in a scanned beam system of claim 11:

wherein outputting the image includes displaying the image.

14. The method for aberration compensation in a scanned beam system of claim 11:

wherein outputting the image includes storing the image.

15. The method for aberration compensation in a scanned beam system of claim 10:

Wherein averaging includes weighted averaging.

16. The method for aberration compensation in a scanned beam system of claim 10:

wherein the aberration is optical aberration.

17. The method for aberration compensation in a scanned beam system of claim 16:

wherein the optical aberration arises at least partly from curvature of an object in the field of view.

18. The method for aberration compensation in a scanned beam system of claim 16:

wherein the optical aberration arises at least partly from an aberration in a post-scanning optical element.