Scanning Projection Apparatus with Tangential Compensation

• US 20120281024A1
• Filed: 05/02/2011
• Published: 11/08/2012
• Est. Priority Date: 05/02/2011
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Champion, Mark
• Granted Patent: US 8,711,186 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02B 27/0031 for scanning purposes
• CPC Class Codes: G09G 3/025 with scanning or deflecting the beams in two directions or dimensions
• CPC Class Codes: G09G 5/10 Intensity circuits
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161

Abstract

A scanning projector includes a scanning mirror that sweep a beam in two dimensions. Tangential distortion in a fast-scan dimension is compensated by incorporating a tangent function when determining the light beam location and interpolating pixel data. Tangential distortion in a slow-scan dimension is compensated by driving the scanning mirror nonlinearly in the slow scan dimension such that the light beam sweeps across the display surface at a constant rate.

Claims

1. An apparatus comprising:

a laser light source;

a mirror being oscillatable on a first axis, the mirror being positioned to reflect light from the laser light source and sweep a light beam sinusoidally through an angle and across a display surface in a first dimension, resulting in tangential distortion in the light beam location on the display surface as a function of time; and

a beam position determination component that determines a location of the light beam on the display surface, wherein the beam position determination component determines the beam location as a function of the sinusoidal sweep as well as the tangential distortion.

2. The apparatus of claim 1 further comprising an interpolation component to interpolate between pixel values in a source image to determine a display pixel value at the beam location.

3. The apparatus of claim 1 wherein the beam position determination component determines the pixel location as:

4. The apparatus of claim 1 wherein the pixel location determination component determines the pixel location as an approximation of:

5. The apparatus of claim 4 wherein the pixel location determination component determines the pixel location as a Taylor series approximation.

6. The apparatus of claim 1 wherein the mirror sweeps nonsinusoidally on a second axis.

7. The apparatus of claim 6 wherein the mirror sweeps through an angle nonlinearly in time on the second axis to approximate a time linear sweep of the light beam on the display surface in a second dimension.

8. The apparatus of claim 7 further comprising a control loop responsive to an angular position of the mirror on the second axis, the control loop including a feedback circuit to determine harmonic coefficients to drive mirror movement on the second axis.

9. The apparatus of claim 1 further comprising a wireless interface.

10. The apparatus of claim 1 further comprising eyewear that includes a projection module to house the laser light source and the mirror.

11. The apparatus of claim 1 further comprising a head-up display module to house the laser light source and the mirror.

12. An apparatus comprising:

a laser light source;

a mirror being movable on two axes, the mirror being positioned to reflect light from the laser light source and onto a display surface, to sweep a light beam sinusoidally in a first dimension responsive to mirror movement on a first axis of the two axes, and to sweep the light beam nonsinusoidally in a second dimension responsive to movement on a second axis of the two axes; and

a control loop responsive to a position of the mirror on the second axis, the control loop including a feedback circuit to determine harmonic coefficients to drive mirror movement on the second axis to sweep the light beam linearly with time across the display surface in the second dimension.

13. The apparatus of claim 12 further comprising a light beam position determination component that determines a location of the light beam in the first dimension on the display surface, wherein the light beam position determination component determines the beam location as a function of the sinusoidal sweep as well as a tangential error resulting from the sinusoidally swept light beam illuminating a flat surface.

14. The apparatus of claim 13 wherein the light beam position determination component determines the location of the light beam in the first dimension as:

15. The apparatus of claim 13 wherein the light beam position determination component determines the location of the light beam in the first dimension as:

16. The apparatus of claim 12 further comprising a wireless transceiver.

17. A method comprising:

oscillating a mirror on a first axis to sweep a light beam in a first dimension on a display surface resulting in a sinusoidal sweep of the light beam with tangential distortion in the light beam location on the display surface as a function of time;

determining a display pixel location on the display surface as a function of the sinusoidal sweep and the tangential distortion in the first dimension;

interpolating source pixel data to arrive at display pixel data to display at the display pixel location; and

commanding a laser light source to produce light in accordance with the display pixel data.

18. The method of claim 17 wherein determining a display pixel location is an approximation of:

19. The method of claim 17 further comprising sweeping the mirror on a second axis nonlinearly to sweep the light beam in a second dimension on the display surface linearly with time.

20. The method of claim 19 further comprising:

sensing a position of the mirror on the second axis; and

modifying a mirror drive signal to drive mirror movement on the second axis.