Depth-sensitive imaging via polarization-state mapping

• US 8,264,536 B2
• Filed: 08/25/2009
• Issued: 09/11/2012
• Est. Priority Date: 08/25/2009
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: McEldowney, Scott
• Primary Examiner(s): Donaghue, Larry
• Application Number:
  US12/547,419
• Publication Number:
  US 20110050885A1
• Time in Patent Office: 1,113 Days
• Field of Search: 348/40, 348/42, 348/51, 348/54, 348/58, 348/59, 348/135
• US Class Current: 348/135
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06V 10/145 Illumination specially adapted for pattern recognition, e.g. using gratings

Abstract

A depth-sensitive imager for imaging a scene in three dimensions. The depth-sensitive imager comprises a light source configured to project a polarized illumination onto a surface of the scene, and a detector configured to capture an image of the scene by detecting light from the scene, in which image a polarization state of the light is encoded. The detected light includes a portion of the polarized illumination reflected from the surface. The depth-sensitive imager further comprises an analyzer configured to generate output responsive to a distance between the light source and the surface based on the image.

Claims

1. A depth-sensitive imager for imaging a scene in three dimensions, the scene comprising a surface, the depth-sensitive imager comprising:

a light source configured to project a polarized illumination onto the surface;

a detector configured to capture an image of the scene by detecting light from the scene, in which image a polarization state of the light is encoded, the light including a portion of the polarized illumination reflected from the surface; and

an analyzer configured to generate output responsive to a distance between the light source and the surface based on the image.

2. The depth-sensitive imager of claim 1, where the surface is one of a plurality of surfaces within the scene arranged at a corresponding plurality of distances from the light source, and where the output is further responsive to the plurality of distances based on the image.

3. The depth-sensitive imager of claim 1, where the light source is configured to project the polarized illumination with a plurality of polarized features spaced apart from each other, and the analyzer is configured to generate the output based on where the polarized features appear in the image.

4. The depth-sensitive imager of claim 1, where the light source is pulse-modulated, the detector is synchronized to the light source, and the analyzer is configured to generate the output based on a delay of the portion of the polarized illumination arriving at the detector.

5. The depth-sensitive imager of claim 1, where the polarization state is sufficient to enable a full Stokes vector representation of the image to be assembled.

6. The depth-sensitive imager of claim 1, where the analyzer is configured to generate the output based on a degree of polarization determined for each of a plurality of regions of the image.

7. The depth-sensitive imager of claim 1, where the analyzer is configured to generate the output based on a linear polarization orientation determined for each of a plurality of regions of the image.

8. The depth-sensitive imager of claim 1, where the output is generated responsive to a condition of the surface, and the analyzer is further configured to assess the condition by comparing the polarization state encoded in the image to a polarization state of the polarized illumination.

9. The depth-sensitive imager of claim 8, where the condition comprises a texture of the surface.

10. The depth-sensitive imager of claim 8, where the condition comprises an orientation of the surface.

11. The depth-sensitive imager of claim 1, where the light source comprises a laser.

12. The depth-sensitive imager of claim 1, where the detector comprises a polarization filter through which the light is transmitted before being detected.

13. The depth-sensitive imager of claim 1, where the detector comprises an array of windows through which the light is transmitted before being detected, where light forming each region of the image is transmitted through a group of adjacent windows of the array, and each window in the group of adjacent windows transmits light of a unique polarization state.

14. A method for imaging a scene in three dimensions, the scene comprising a surface, the method comprising:

projecting a polarized illumination onto the surface;

capturing an image of the scene by detecting light from the scene, in which image a polarization state of the light is encoded, the light including a portion of the polarized illumination reflected from the surface; and

analyzing the image to generate output responsive to a distance between the light source and the surface based on the image.

15. The method of claim 14, further comprising computing a full Stokes vector representation of the image.

16. The method of claim 14, where the output is generated based on a degree of polarization determined for each region of the image.

17. The method of claim 14, where the output is generated further based on a linear polarization orientation determined for each region of the image.

18. The method of claim 14, where the output is generated responsive to a texture or orientation of the surface, and the analyzer is further configured to assess the texture or orientation by comparing the polarization state encoded in the image to a polarization state of the polarized illumination.

19. A depth-sensitive imager for imaging a scene in three dimensions, the scene comprising a surface, the depth-sensitive imager comprising:

a laser configured to project onto the surface a polarized illumination comprising a plurality of polarized features spaced apart from each other;

a camera configured to capture an image of the scene by detecting light from the scene, in which image a degree of polarization of the light is encoded, the light including a portion of the polarized illumination reflected from the surface; and

an analyzer configured to triangulate a distance between the laser and the surface based on a spacing between adjacent polarized features in the image and further based on an angle between the adjacent polarized features in the polarized illumination.

20. The depth-sensitive imager of claim 19, where the laser is configured to emit at a near-infrared wavelength, and the camera is configured to detect light of the near-infrared wavelength.