ILLUMINATOR WITH REFRACTIVE OPTICAL ELEMENT

• US 20120229611A1
• Filed: 03/07/2011
• Published: 09/13/2012
• Est. Priority Date: 03/07/2011
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Pellman, Asaf, Cohen, David, Yahav, Giora
• Granted Patent: US 9,551,914 B2
• Time in Patent Office: Days
• US Class Current: 348/49
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: G03B 2215/0592 installed in front of light emitter

Abstract

An illumination system having a refractive optical element that compensates for dependence in irradiance of images of objects captured by a photosensor is provided. The refractive optical element may structure the light such that similar objects in the same spherical surface in the field of view of the camera have the same irradiance on the camera photosensor. The illumination system may have an image sensor, a light source, and a refractive optical element. The image sensor has a photosensor that captures images of objects in a field of view. The irradiance of images of objects having a given exitance that are captured by the photosensor may depend on angular displacement from an optical axis of the image sensor. The refractive optical structures light from the light source to illuminate the field of view to compensate for the dependence of irradiance on angular displacement from the optical axis.

Claims

1. An illumination system, comprising:

an image sensor having a photosensor that captures images of objects in a field of view, the image sensor having an optical axis, irradiance of images of objects having a given exitance that are captured by the photosensor depend on angular displacement from the optical axis;

a light source; and

a refractive optical element that receives light from the light source and structures the light to illuminate the field of view to compensate for the dependence of irradiance on angular displacement from the optical axis.

2. The illumination system of claim 1, wherein the refractive optical element includes a plurality of lenses.

3. The illumination system of claim 1, wherein the refractive optical element includes one or more arrays of rectangular lenses.

4. The illumination system of claim 1, wherein the refractive optical element includes a plurality of arrays of lenses.

5. The illumination system of claim 1, further comprising a collimator that receives the light from the light source, the refractive optical element receives collimated light and structures the collimated light to illuminate the field of view to compensate for the dependence of irradiance on angular displacement from the optical axis.

6. The illumination system of claim 1, wherein the refractive optical element is part of a single component that serves as the refractive optical element and a collimator.

7. The illumination system of claim 1, wherein refractive optical element is between the light source and the collimator.

8. The illumination system of claim 1, further comprising logic for generating a depth image based on the light received by the photosensor.

9. The illumination system of claim 1, wherein the refractive optical element diffuses the light to illuminate objects in the field of view in accordance with 1/cos⁴ θ

, where θ

is the angular displacement from the optical axis.

10. A depth camera system comprising:

an image sensor having a photosensor that captures images of objects in a field of view, the image sensor having an optical axis;

a light source;

a collimator that collimates the light source;

a refractive diffuser that receives light from the light source and structures the light within the field of view in accordance with 1/cos⁴ θ

, where θ

is the angular displacement from the optical axis; and

logic for generating a depth image based on the light received by the photosensor.

11. The depth camera system of claim 10, wherein the refractive diffuser includes a plurality of lenses.

12. The depth camera system of claim 10, wherein the refractive diffuser structures the light such that similar objects in the same spherical surface in the field of view, but at different angular displacements from the optical axis, have substantially the same irradiance on the photosensor.

13. The depth camera system of claim 10, wherein the refractive diffuser structures the light to compensate for dependence of irradiance of images of objects having a given exitance that are captured by the photosensor on angular displacement from the optical axis.

14. The depth camera system of claim 13, wherein the refractive diffuser is configured to structure the light to drop off in intensity outside of the field of view.

15. The depth camera system of claim 10, wherein refractive diffuser is between the light source and the collimator.

16. The depth camera system of claim 10, wherein the refractive diffuser is part of a single component that serves as the refractive diffuser and the collimator.

17. A method of generating a depth image, comprising:

refracting light onto objects in a field of view using a refractive diffuser;

capturing light that reflects from objects in the field of view at a photosensor having an optical axis, irradiance of images of objects having a given exitance that are captured by the photosensor depend on angular displacement from the optical axis, the refracting the light includes structuring the light to compensate for the dependence of irradiance on angular displacement from the optical axis; and

generating a depth image based on the captured light.

18. The method of claim 17, wherein refracting the light includes diffusing the light in accordance with the formula 1/cos⁴ θ

, wherein θ

is the angular displacement from the optical axis.

19. The method of claim 17, wherein the refracting light onto objects in a field of view using a refractive diffuser includes structuring the light to falloff in intensity outside of the field of view.

20. The method of claim 17, further comprising:

generating a light beam;

collimating the light beam, the refracting light includes refracting the collimated light beam.