Scanned Proximity Detection Method and Apparatus for a Scanned Image Projection System

• US 20100053591A1
• Filed: 11/09/2009
• Published: 03/04/2010
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Brown, Margaret K., DeJong, Christian Dean, Hudman, Joshua M., Gibson, Gregory T.
• Granted Patent: US 8,251,517 B2
• Time in Patent Office: Days
• US Class Current: 356/3.90
• 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 encoded image projection system (100) is configured to determine the proximity of the system to a projection surface (106). The encoded image projection system (100) includes a light encoder (105) that scans a non-visible light beam (115) on the projection surface (106) selectively when scanning visible light to create an image. A detector (118) is then configured to receive reflections of the non-visible light beam (115) from the projection surface (106). A control circuit (120) is configured to determine the distance (124) between the projection surface (106) and the system from, for example, intensity data or location data received from the detector (118). Where the distances (124) are below a threshold, the control circuit (120) can either reduce the output power of the system or turn the system off.

Claims

1. A encoded image projection system configured for proximity detection, comprising:

a light encoder configured to encode a light beam across a projection surface;

a detector configured to receive a reflected beam from the projection surface; and

a control circuit configured to determine a distance between the encoded image projection system and the projection surface based upon a comparison of signals corresponding to the reflected beam with a threshold.

2. The encoded image projection system of claim 1, wherein where the distance is less than a predetermined minimum distance, the control circuit is configured to reduce an output power of the encoded image projection system.

3. The encoded image projection system of claim 1, wherein where the distance is less than a predetermined minimum distance, the control circuit is configured cause the encoded image projection system to cease projecting images on the projection surface.

4. The encoded image projection system of claim 3, wherein the predetermined minimum distance is 100 millimeters.

5. The encoded image projection system of claim 1, wherein the light encoder comprises a MEMS scanning mirror, further wherein the light beam comprises one of an infrared beam or an ultraviolet beam.

6. The encoded image projection system of claim 5, wherein the detector comprises one of an infrared input filter or an ultraviolet filter and one of a charge-coupled photodetector device or a CMOS photodetector device.

7. The encoded image projection system of claim 1, wherein the control circuit is configured to determine the distance by comparing a location of the reflected beam with a location threshold using three or fewer least significant bits of intensity data delivered to the control circuit from the detector.

8. A method of determining a distance between a encoded projection system and a projection surface, the method comprising:

delivering one or more light beams to a encoding device;

delivering a non-visible light beam to the encoding device with the one or more light beams;

scanning, with the encoding device, an image on the projection surface with the one or more light beams and scanning, selectively, a pattern with the non-visible light beam;

receiving a reflected non-visible light beam from the projection surface in response to scanning the pattern;

and determining the distance by comparing the non-visible light beam to a threshold.

9. The method of claim 8, further comprising orienting the one or more light beams and the non-visible light beam as collinear beams and multiplexing the non-visible light beam with visible light beams.

10. The method of claim 8, further comprising determining a rate of change in proximity by comparing the non-visible light beam to data corresponding to a previously captured non-visible light beam.

11. The method of claim 10, further comprising determining an estimated reflectivity of at least a portion of the projection surface and adjusting the threshold based upon the estimated reflectivity.

12. The method of claim 8, wherein the determining the distance comprises determining a centroid of at least a portion of the pattern, wherein the determining the distance further comprises comparing the centroid to a location threshold value stored in a memory of the encoded projection system.

13. The method of claim 12, further comprising one of reducing an output power of the encoded projection system or turning the encoded projection system OFF when the distance is less than a location threshold.

14. The method of claim 8, wherein the scanning the pattern of the non-visible light beam comprises scanning the pattern within a region of interest within the image, wherein the region of interest is larger when the projection surface is closer to the encoded projection system than when the projection surface is farther from the encoded projection system.

15. The method of claim 8, further comprising generating one or more of an intensity value or a location value in response to the receiving the non-visible light beam, and integrating the one or more of the intensity value or the location value prior to the determining the distance.

16. An imaging system capable of determining a distance between the imaging system and a projection surface, the imaging system comprising:

one or more light sources configured to selectively produce one or more light beams;

an additional light source configured to selectively produce an alternate light beam;

one or more optical alignment devices configured to orient the one or more light beams and the alternate light beam as collinear light;

a light encoder configured to produce images by scanning the collinear light along the projection surface;

a photodetector configured to detect reflected light from the alternate light beam reflecting from the projection surface; and

a controller configured to determine the distance between the projection surface and the imaging system from at least location data generated by the photodetector in response to detecting the reflected light.

17. The imaging system of claim 16, wherein the controller is further configured to determine the distance from location data generated by the photodetector.

18. The imaging system of claim 16, wherein the light encoder is configured to produce the images by scanning in a raster pattern, wherein the additional light source is configured to produce the alternate light beam during one of a fly-back portion of the raster pattern, a fly-forward portion of the raster pattern, or during horizontal or vertical over-scan portions of the raster pattern.

19. The imaging system of claim 16, wherein the controller is configured to determine a centroid of a pattern formed by the reflected light, wherein the controller is further configured to determine the distance by comparing location of the centroid to a location threshold.

20. The imaging system of claim 16, wherein the one or more light sources are disposed in a first device, and the additional light source is disposed in a second device.