Dynamic constancy of brightness or size of projected content in a scanning display system

Patent metadata

Field	Value
Publication number	US-9762873-B2
Application number	US-201514845698-A
Country	US
Kind code	B2
Filing date	Sep 4, 2015
Priority date	Sep 4, 2015
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A scanning projector includes a MEMS device with a scanning mirror that sweeps a beam in two dimensions. Actuating circuits receive scan angle information and provide signal stimulus to the MEMS device to control the amount of mirror deflection on two axes. The scan angle information may be modified to maintain a constant image size, a constant image brightness, and/or to correct for keystone distortion.

First claim

What is claimed is:

1. A scanning display system comprising:
a first laser light source to emit first laser light;
a second laser light source to emit second laser light;
a scanning mirror to reflect and scan the first laser light received from the first laser light source and the second laser light from the second laser light source and to create a visible image on a projection surface;
a photodetector to detect the second laser light reflected off the projection surface;
a time-of-flight (TOF) detection circuit responsive to the photodetector to measure distances from the scanning display system to multiple points on the projection surface;
a mirror actuating circuit to drive the mirror with signals that cause the mirror to deflect through angular extents in two dimensions; and
a display size control circuit to average the distances from the scanning display system to the multiple points, and to modify the angular extents of mirror deflection based on the average to maintain a constant display size on the projection surface.

2. The scanning display system of claim 1 wherein the display size control circuit is responsive to user input.

3. The scanning display system of claim 1 wherein the display size control circuit is configured to determine when the distances from the scanning display system to the multiple points diverge beyond a threshold to determine if keystone distortion is present.

4. The scanning display system of claim 3 wherein the display size control circuit is configured to modify angular extents of mirror deflection to correct keystone distortion.

5. The scanning display system of claim 1 wherein the second laser light source comprises an infrared laser light source.

6. The scanning display system of claim 1 wherein the first laser light source comprises at least one visible laser light source.

7. A scanning display system comprising:
at least one visible laser light source;
at least one nonvisible laser light source;
a scanning mirror to reflect and scan light received from the at least one visible laser light source and the at least one nonvisible laser light source and create a visible image on a projection surface;
a photodetector to detect nonvisible laser light reflected off the projection surface;
a time-of-flight (TOF) detection circuit responsive to the photodetector to measure distances from the scanning display system to multiple points on the projection surface;
an ambient light sensor to provide ambient light level information;
a mirror actuating circuit to drive the mirror with signals that cause the mirror to deflect through angular extents in two dimensions; and
a display size control circuit to average the distances from the scanning display system to the multiple points to determine an average distance, to average the ambient light level information received over time to determine an average ambient light level, and to modify the angular extents of mirror deflection in response to the average distance and the average ambient light level to maintain a constant display size and a constant image brightness on the projection surface.

8. The scanning display system of claim 7 wherein the display size control circuit is responsive to user input.

9. The scanning display system of claim 7 wherein the display size control circuit is configured to determine if keystone distortion is present.

10. The scanning display system of claim 9 wherein the display size control circuit is configured to modify angular extents of mirror deflection to correct keystone distortion.

11. The scanning display system of claim 7 wherein the at least one nonvisible laser light source comprises an infrared laser light source.

12. The scanning display system of claim 7 wherein the at least one visible laser light source comprises one or more red laser light sources, one or more green laser light sources, and one or more blue laser light sources.

13. A method of operating a scanning display system comprising:
creating visible laser light pulses to represent pixels in an image;
reflecting the visible laser light pulses off a scanning mirror to display the image on a projection surface;
creating nonvisible laser light pulses;
reflecting the nonvisible laser light pulses off the scanning mirror;
receiving reflections of the nonvisible laser light;
measuring a time-of-flight (TOF) of the reflections of nonvisible laser light to determine distances from the scanning display system to multiple points on the projection surface;
averaging the distances from the scanning display system to the multiple points on the projection surface to determine an average distance from the scanning display system to the projection surface; and
modifying angular extents of mirror deflection in response to the average distance from the scanning display system to the projection surface.

14. The method of claim 13 wherein modifying angular extents of mirror deflection in response to the average distance from the scanning display system to the projection surface comprises modifying the angular extents of mirror deflection to maintain a substantially constant image brightness.

15. The method of claim 13 wherein modifying angular extents of mirror deflection in response to the average distance from the scanning display system to the projection surface comprises modifying the angular extents of mirror deflection to maintain a substantially constant image size.

16. The method of claim 13 further comprising modifying the angular extents of mirror deflection to correct keystone distortion.

Assignees

• Microvision Inc

Inventors

• Honkanen Jari
• Viswanathan P Selvan

Classifications

• G01S17/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) · CPC title

• H04N9/3135

  Driving therefor · CPC title

• G01S7/4817 Primary

  relating to scanning · CPC title

• H04N9/3161

  using laser light sources (using laser beams scanning the display screen H04N9/3129) · CPC title

• G09G5/10

  Intensity circuits · CPC title