Fast Camera Auto-Focus

• US 20100080482A1
• Filed: 09/30/2008
• Published: 04/01/2010
• Est. Priority Date: 09/30/2008
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Li, Pingshan, Murakami, Yoshihiro, Nakamura, Makibi, Wong, Earl Quong, Kushida, Hidenori, Sugiura, Mamoru, Triteyaprasert, Soroj
• Granted Patent: US 8,194,995 B2
• Time in Patent Office: Days
• US Class Current: 382/255
• CPC Class Codes: H04N 23/67 Focus control based on electronic image sensor signals

Abstract

A camera auto-focuses using computed blur differences between images of a three-dimensional scene. The camera computes the blur difference between two images of the scene acquired at two different picture numbers. The camera uses the computed blur difference to predict a third picture number, where the camera uses the third picture number to auto-focus a camera lens on the scene.

Claims

1. A computerized method comprising:

computing a blur difference between a first and a second image of a three-dimensional scene, the first image acquired through a camera lens focused at a first picture number and the second image acquired through the camera lens focused at a second picture number, wherein the first and second picture numbers represent different focus distances of the camera lens; and

predicting a third picture number based on the computer blur difference, wherein the third picture number is subsequently used to auto-focus the camera lens on the scene.

2. The computerized method of claim 1, wherein the predicting is further based on a blur difference curve associated with the first picture number.

3. The computerized method of claim 2, further comprising:

retrieving the blur difference curve from one of a plurality of stored blur difference curves.

4. The computerized method of claim 3, wherein each of the plurality of stored blur difference curves is associated with a different picture number.

5. The computerized method of claim 2, further comprising:

determining the blur difference curve using the computed blur difference.

6. The computerized method of claim 1, wherein the computing a blur difference is further based on using an image mask.

7. The computerized method of claim 1, wherein the computing a blur difference comprises:

convolving the first image into the second image with a blur kernel.

8. The computerized method of claim 1, wherein the first picture number is a picture number at one of a minimal focus distance and an infinite focus distance.

9. The computerized method of claim 1, wherein the first picture number is predicted from a blur difference of a third and fourth image.

10. The computerized method of claim 1, wherein the second picture number is adjacent to the first picture number.

11. A machine readable medium having executable instructions to cause a processor to perform a method comprising:

computing a blur difference between a first and a second image of a three-dimensional scene, the first image acquired through a camera lens focused at a first picture number and the second image acquired through the camera lens focused at a second picture number, wherein the first and second picture numbers represent different focus distances of the camera lens; and

predicting a third picture number based on the computer blur difference, wherein the third picture number is subsequently used to auto-focus the camera lens on the scene.

12. The machine readable medium of claim 11, wherein the predicting is further based on a blur difference curve associated with the first picture number.

13. The machine readable medium of claim 12, further comprising:

retrieving the blur difference curve from one of a plurality of stored blur difference curves.

14. The machine readable medium of claim 13, wherein each of the plurality of stored blur difference curves is associated with a different picture number.

15. The machine readable medium of claim 12, further comprising:

determining the blur difference curve using the computed blur difference.

16. The machine readable medium of claim 11, wherein the computing a blur difference comprises:

convolving the first image into the second image with a blur kernel.

17. An apparatus comprising:

means for computing a blur difference between a first and a second image of a three-dimensional scene, the first image acquired through a camera lens focused at a first picture number and the second image acquired through the camera lens focused at a second picture number, wherein the first and second picture numbers represent different focus distances of the camera lens; and

means for predicting a third picture number based on the computer blur difference, wherein the third picture number is subsequently used to auto-focus the camera lens on the scene.

18. The apparatus of claim 17, wherein the means for predicting is further based on a blur difference curve associated with the first picture number.

19. The apparatus of claim 18, further comprising:

means for retrieving the blur difference curve from one of a plurality of stored blur difference curves.

20. The apparatus of claim 18, further comprising:

means for determining the blur difference curve using the computed blur difference.

21. The apparatus of claim 17, wherein the means for computing a blur difference comprises:

means for convolving the first image into the second image with a blur kernel.

22. A system comprising:

a processor;

a memory coupled to the processor though a bus; and

a process executed from the memory by the processor to cause the processor to compute a blur difference between a first and a second image of a three-dimensional scene, the first image acquired through a camera lens focused at a first picture number and the second image acquired through the camera lens focused at a second picture number, wherein the first and second picture numbers represent different focus distances of the camera lens and predict a third picture number based on the computer blur difference, wherein the third picture number is subsequently used to auto-focus the camera lens on the scene.