IMAGING SYSTEM

• US 20100026850A1
• Filed: 07/29/2009
• Published: 02/04/2010
• Est. Priority Date: 07/29/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft International Holdings BV (Microsoft Corporation)
• Inventors: Katz, Sagi
• Granted Patent: US 8,890,952 B2
• Time in Patent Office: Days
• US Class Current: 348/234
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar

Abstract

An imaging system comprising: a light source for illuminating a scene with a known intensity light; a camera having an optic axis and center that images the scene responsive to light reflected by the scene from the illuminating, known intensity light; a range finder controllable to determine distances to surface elements of the scene imaged by the camera; a controller configured to determine reflectivity of a surface element of the scene imaged by the camera responsive to a distance of the surface element from the camera, the known intensity of illuminating light and light from the surface element imaged by the camera.

Claims

1. An imaging system comprising:

a light source for illuminating a scene with a known intensity light;

a camera having an optic axis and center that images the scene responsive to light reflected by the scene from the illuminating, known intensity light;

a range finder controllable to determine distances to surface elements of the scene imaged by the camera;

a controller configured to determine reflectivity of a surface element of the scene imaged by the camera responsive to a distance of the surface element from the camera, the known intensity of illuminating light and light from the surface element imaged by the camera.

2. An imaging system according to claim 1, wherein the controller processes determined distances to define normals to surface elements of the scene imaged by the camera.

3. An imaging system according to claim 2, wherein the controller determines reflectivity of a surface element of the scene responsive to the normal to the surface element.

4. An imaging system according to claim 3, wherein the controller determines an imaging direction for a surface element imaged by the camera along which imaging direction the camera images light from the surface element.

5. An imaging system according to claim 4, wherein the imaging direction is parallel to a line from the surface element to the optic center of the camera.

6. An imaging system according to claim 4, wherein the imaging direction is parallel to the optic axis of the camera.

7. An imaging system according to claim 4, wherein the controller determines reflectivity of a surface element responsive to the imaging direction.

8. An imaging system according to claim 7, wherein the controller determines reflectivity of a surface element responsive to a dot product of the normal and a vector parallel to the imaging direction.

9. An imaging system according to claim 4, wherein the controller is configured to identify a feature in the scene responsive to a product of the reflectivity determined for a surface element imaged by the camera times a cosine of an angle between the surface element'"'"'s imaging direction and normal.

10. An imaging system according to claim 1, wherein the controller is configured to identify a feature in the scene responsive to determined reflectivity of a surface element imaged by the camera.

11. An imaging system according to claim 4, and comprising a controller configured to provide an image of the scene wherein a gray level of a pixel in the image is substantially equal to a product of the reflectivity determined for a surface element imaged on the pixel times a cosine of an angle between the surface element'"'"'s imaging direction and normal.

12. An imaging system according to claim 1, and comprising a controller configured to provide an image of the scene comprising image pixels whose gray levels are substantially proportional to reflectivities determined for surface elements of the scene imaged on the pixels.

13. An imaging system according to claim 1, wherein the range finder comprises a gated time of flight range finder.

14. An imaging system according to claim 2 comprising a light source controllable to illuminate different regions of the scene independently of each other with intensities of light responsive to their respective normals.

15. An imaging system according to claim 1 comprising a light source controllable to illuminate different regions of the scene independently of each other with intensities of light responsive to their respective reflectivities.

16. A method of determining reflectivity of a surface element of a scene, the method comprising:

illuminating the scene with known intensity light;

imaging the surface element with light reflected by the surface element from the known intensity light;

determining distances to a plurality of surface elements of the scene;

determining a normal to the surface element responsive to the determined distances; and

determining the reflectivity of the surface element responsive to the normal and an amount of light from the known intensity light that is reflected by the surface element and imaged.

17. A method according to claim 16 and comprising determining an imaging direction substantially along which light from the surface element is imaged.

18. A method according to claim 17 and comprising determining the reflectivity responsive to the imaging direction.

19. A method according to claim 18 and comprising imaging the scene with a camera having an optic center and determining the imaging direction comprises determining the imaging direction to be a direction parallel to a line from the surface element to the optic center of the camera.

20. A method according to claim 18 and comprising imaging the scene with a camera having an optic axis and determining the imaging direction comprises determining the imaging direction to be a direction parallel to the optic axis.

21. A method according to claim 18, and determining reflectivity of a surface element responsive to a dot product of the normal and a vector parallel to the imaging direction.

22. A method according to claim 17 and comprising identifying a feature in the scene responsive to a product of the reflectivity times a cosine of an angle between the imaging direction and normal.

23. A method according to claim 16 and identifying a feature in the scene responsive to the reflectivity.

24. A method according to claim 17, and comprising providing an image of the scene wherein a gray level of a pixel in the image that images the surface element is substantially equal to a product of the reflectivity determined times a cosine of an angle between the imaging direction and normal.

25. A method according to claim 16, and comprising providing an image of the scene wherein a gray level of a pixel in the image that images the surface element is substantially proportional to the reflectivity.