Implementing autofocus in an image capture device while compensating for movement

• US 9,215,363 B2
• Filed: 11/16/2004
• Issued: 12/15/2015
• Est. Priority Date: 09/29/2004
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Stavely, Donald J., Bianchi, Mark J., Bloom, Daniel M., Schinner, Charles E., Spears, Kurt E., Brake, Wilfred
• Primary Examiner(s): KHAN, USMAN A
• Application Number:
  US10/989,990
• Publication Number:
  US 20060066744A1
• Time in Patent Office: 4,046 Days
• Field of Search: 348/352, 348/220.1, 348/208.1, 348/155, 348/345, 348/208.12
• US Class Current: 1/1
• CPC Class Codes: G03B 13/16 combined with focusing aids
• CPC Class Codes: G03B 3/00 Focusing arrangements of general interest for cameras, projectors or printers
• CPC Class Codes: H04N 23/61 based on recognised objects
• CPC Class Codes: H04N 23/675 comprising setting of focusing regions
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations

Abstract

A system and method for focusing an image capture device are disclosed. One embodiment is a method comprising moving an autofocus window in response to detected movement of the image capture device.

Claims

1. A method for focusing an image capture device on an object of interest, comprising:

capturing a first focus image when an autofocus lens is at a first focus position, the first focus image having an autofocus window that is directed towards a target object upon which the image capture device is to focus on;

detecting movement of the image capture device, the movement occurring between capture of the first focus image and a second focus image;

discriminating the movement of the image capture device between intended movement and unintended movement;

adjusting a position of the autofocus window while maintaining a corresponding number of pixels of the autofocus window based on discriminating between the intended movement and the unintended movement, the adjustment always being opposite to the detected movement such that the target object remains stationary within the autofocus window during the detected movement, the adjustment being only in response to unintended movement of the image capture device;

re-centering the autofocus window when the movement of the image capture device is the intended movement;

capturing a second focus image when the autofocus lens is at a second focus position;

identifying at least one direction of movement of the image capture device;

determining a direction that is opposite in direction to the movement direction of the image capture device without any user-input; and

shifting the position of the autofocus window in the direction that is opposite in direction to the direction of the image capture device movement to define the second focus image; and

wherein the autofocus window automatically and continuously moves back toward a center of an image capture region, while the direction of the image capture device still follows movement of the autofocus window on the image capture region, the movement on the image capture region is quicker than the autofocus window moving back toward the center of the image capture region.

2. The method of claim 1, wherein the target object remains substantially stationary within the autofocus window during the detected movement.

3. The method of claim 1, further comprising determining a first focus metric derived from the first focus image and a second focus metric derived from the second focus image.

4. The method of claim 1, further comprising:

determining a focus position for the autofocus lens; and

adjusting the autofocus lens so that the object of interest is focused for image capture.

5. The method of claim 1, further comprising:

receiving image data from a first group of pixels residing in a photosensor that captures an image of the target object, the first group of pixels corresponding to the first focus image;

determining a second group of pixels based upon the detected movement wherein the second group of pixels corresponds to the second focus image; and

receiving the image data from the second group of pixels.

6. The method of claim 5, wherein the first group of pixels and the second group of pixels reside in the photosensor that captures the image of the object of interest.

7. The method of claim 1, further comprising:

identifying at least one direction of movement of the image capture device; and

shifting position of the autofocus window in a direction that is opposite in magnitude to the direction of the image capture device movement to define the second focus image.

8. The method of claim 7, wherein the shifting position of the autofocus window further comprises shifting position of the autofocus window in the direction that is a fraction of the magnitude of the direction of the image capture device movement.

9. The method of claim 1, further comprising focusing an image capture device lens based upon the shifted autofocus window.

10. The method of claim 1, further comprising:

receiving information from at least one sensor that detects the movement of the image capture device; and

processing the received information to determine the movement of the image capture device.

11. The method of claim 1, further comprising:

capturing a first image;

capturing a second image;

comparing the first image with the second image; and

determining the movement of the image capture device based upon at least one difference between the compared first image and second image.

12. The method of claim 11, wherein determining the movement is based upon a correlation function between the first image and the second image.

13. The method of claim 1, further comprising:

capturing a plurality of focus images when the autofocus lens is at a corresponding plurality of different focus positions, the plurality of focus images having the autofocus window;

detecting the movement of the image capture device as the plurality of focus images are captured; and

adjusting position of the autofocus window as the plurality of focus images are captured, the adjustments corresponding to the detected movement such that the target object remains stationary within the autofocus window during the detected movement and while the plurality of focus images are captured.

14. The method of claim 1, further comprising:

capturing a first plurality of focus images when the autofocus lens is at the first focus position, the first plurality of focus images having a corresponding plurality of autofocus windows that are directed towards at least an object upon which the image capture device is to focus on;

detecting the movement of the image capture device, the motion occurring between capture of the first focus image and the second focus image;

adjusting the position of the plurality of autofocus windows, the adjustment corresponding to the detected movement such that the object remains stationary within the plurality of autofocus windows during the detected movement;

capturing a second plurality of focus images when the autofocus lens is at the second focus position; and

selecting one of the first plurality of focus images and a corresponding one of the second plurality of focus images to determine focus.

15. The method of claim 1, wherein detecting the movement further comprises generating a motion vector from successive focus images using a video compression algorithm.

16. The method of claim 15, wherein generating the motion vector further comprises generating the motion vector from a moving picture experts group (MPEG) video compression algorithm.

17. The method of claim 1, wherein discriminating is based on frequency of the detected movement.

18. The method of claim 1, wherein intended movement is from following a moving subject, and unintended movement is from hand shake.