Method and apparatus providing imaging auto-focus utilizing absolute blur value

• US 20090079862A1
• Filed: 09/25/2007
• Published: 03/26/2009
• Est. Priority Date: 09/25/2007
• Status: Abandoned Application

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Subbotin, Igor
• Application Number:
  US11/902,748
• Publication Number:
  US 20090079862A1
• Time in Patent Office: Days
• US Class Current: 348/345
• CPC Class Codes: H04N 23/67 Focus control based on electronic image sensor signals

Abstract

A method and apparatus for determining the need for and performing a refocusing of an imaging device using a blur value, which determines absolute sharpness. The blur detection is itself based on reading one or more edges. New lens positioning is controlled based on the blur value.

Claims

1. A method for controlling the focus of an imaging device, comprising:

receiving an image on a pixel array;

determining an edge slope for a current point in the received image;

calculating a difference in a minimum and a maximum signal around the current point, the difference being a height;

dividing the height by the edge slope to define a blur value; and

using the blur value to control focus of the imaging device.

2. The method of claim 1, comprising:

defining a respective blur value for a plurality of additional points; and

calculating an average blur value based on each defined blur value.

3. The method of claim 1, wherein the current point is in a window of pixels, wherein the window encompasses and area of the pixel array less than the full size of the pixel array.

4. The method of claim 3, wherein the pixel window comprises a 9×

9 group of pixels.

5. The method of claim 1, further comprising defining blur value for a still image capture.

6. The method of claim 1, further comprising defining blur value for continuous image capture.

7. A method of auto-focusing an imaging device, comprising:

focusing an image on a pixel array;

determining a first blur value for the image;

refocusing the image on the pixel array;

determining a second blur value for the image; and

repeatedly refocusing and determining additional blur values until the blur value is determined to be within a predetermined range.

8. The method of claim 7, further comprising comparing the second blur value to the first blur value, wherein if the second blur value is greater than the first blur value, a second refocus is performed.

9. The method of claim 7, wherein the acceptability of the focus is not determined until the second blur value is not greater than the first blur value.

10. The method of claim 7, wherein the second blur value is set to be the first blur value each time a refocus is performed.

11. A method of controlling a continuous auto-focus operation, comprising:

focusing an image on a pixel array;

determining a first blur value for the image;

refocusing the image on the pixel array;

determining a second blur value for the image;

comparing the second blur value to the first blur value;

setting the second blur value to be a new first blur value;

determining if motion is detected; and

if motion is detected, determining a third blur value for the image.

12. The method of claim 11, comprising refocusing if the second blur value is greater than the first blur value.

13. The method of claim 11, comprising determining if the second blur value relates to a focused image if the second blur value is not greater than the first blur value.

14. An imaging device, comprising:

a pixel array;

at least one lens;

a device providing relative movement between the lens and the pixel array for focusing an image passing through the lens on the pixel array; and

a circuit configured to determine the sharpness of the image focused on the pixel array by calculating edge height at a point of the pixel array and dividing by edge slope at the point.

15. The imaging device of claim 14, wherein the circuit configuration is provided as software instructions executed by a processor.

16. The imaging device of claim 14, wherein the circuit configuration is provided as a logic circuit.

17. The imaging device of claim 14, wherein the circuit at least partially controls the means for focusing.

18. An imaging device, comprising:

a pixel array;

a lens positioned to focus an image on the pixel array;

a first device configured to determine blur value of an image focused on the pixel array by determining the edge height at a point on the pixel array and dividing by the edge slope at the point; and

a second device configured to refocus the image on the pixel array based on the blur value.

19. The imaging device of claim 18, wherein the first device is a processor programmed with software.

20. The imaging device of claim 18, wherein the first device is a hardwired logic circuit.

21. The imaging device of claim 18, wherein the second device controls movement of the lens.

22. The imaging device of claim 18, wherein the second device controls movement of the pixel array.

24. The imaging device of claim 24, wherein the imaging device is part of a video camera.

23. The imaging device of claim 24, wherein the imaging device is part of a still camera.