Implementing autofocus in an image capture device while compensating for movement

• US 20060066744A1
• Filed: 11/16/2004
• Published: 03/30/2006
• 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., Brake, Wilfred, Schinner, Charles E., Spears, Kurt E.
• Granted Patent: US 9,215,363 B2
• Time in Patent Office: Days
• US Class Current: 348/352
• 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;

adjusting position of the autofocus window, the adjustment corresponding to the detected movement such that the target object remains stationary within the autofocus window during the detected movement; and

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

2. The method of claim 1, wherein the target object corresponds to the object of interest.

3. The method of claim 1, wherein the target object corresponds to at least a portion of the object of interest.

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

5. 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.

6. 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.

7. 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.

8. The method of claim 7, 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.

9. 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.

10. The method of claim 9, 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.

11. 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 direction to the direction of the image capture device movement to define the second focus image.

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

13. 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.

14. 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.

15. The method of claim 14, wherein determining the movement is based upon a correlation function between the first image and the second image.

16. 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.

17. 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.

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

19. The method of claim 18, wherein generating the motion vector further comprises generating the motion vector from a moving picture experts group (MPEG) video compression algorithm.

20. An image capture device, comprising:

a photosensor configured to capture an image of an object of interest;

an autofocus window defined as a grouping of pixels residing in the photosensor, the autofocus window being directed towards a target object upon which the image capture device is to focus on;

an adjustable-focus lens configured to focus the image of the object of interest onto the photosensor; and

a processor system configured to execute logic that determines movement of the image capture device occurring between capture of a first focus image when the adjustable-focus lens is at a first focus position and capture of a second focus image when the adjustable-focus lens is at a second focus position, configured to execute logic to adjust position of the autofocus window such that the target object remains stationary within the autofocus window during the detected movement, and further configured to generate a signal that causes the adjustable-focus lens to focus the image of the object of interest onto the photosensor.

21. The image capture device of claim 20, wherein the target object remains substantially stationary within the autofocus window during the detected movement.

22. The image capture device of claim 20, further comprising a group of pixels residing in the photosensor, the group of pixels defining the autofocus window.

23. The image capture device of claim 20, wherein the photosensor captures a first image and later captures a second image such that the processor system executes logic to determine the movement based upon differences between the captured first image and the captured second image.

24. The image capture device of claim 20, further comprising at least one sensor that detects the movement of the image capture device and that communicates to the processor system a signal corresponding to the detected movement.

25. An autofocus window comprising a group of pixels residing in a photosensor of an image capture device having an autofocus system and an autofocus lens, wherein when the autofocus window is directed towards at least a portion of an object of interest upon which the image capture device is to focus on, such that position of the autofocus window remains stationary during detected movement of the image capture device.

26. The autofocus window of claim 25, wherein the position of the autofocus window remains substantially stationary during the detected movement.

27. The autofocus window of claim 25, wherein the autofocus window comprises a first group of pixels in a first location at a first time, and wherein the autofocus window further comprises a second group of pixels in a second location at a second time, and wherein a difference between the first location and the second location corresponds to a direction that is substantially opposite to the detected movement of the image capture device occurring between the first time and the second time.

28. The autofocus window of claim 27, wherein the first group of pixels captures a first focus image at the first time, and wherein the second group of pixels captures a second focus image at the second time.

29. The autofocus window of claim 28, wherein a difference in content of the first focus image and content of the second focus image is analyzed to determine a focus of the object of interest on the photosensor, such that the autofocus system determines a focus position for the autofocus lens, and such that the autofocus lens is adjusted to the autofocus system so that the object of interest is focused for image capture.

30. The autofocus window of claim 25, further comprising a second group of pixels residing in the photosensor that define a second autofocus window, wherein position of the second autofocus window remains substantially stationary during the detected movement of the image capture device.

33. The program of claim 25, wherein the target object remains substantially stationary within the autofocus window during the detected movement.

31. A system for focusing an image capture device, comprising:

means for capturing a first focus image at a first time when an autofocus lens is at a first focus position, the first focus image having an autofocus window that is directed towards at least a portion of an object of interest upon which the image capture device is to focus on;

means for detecting movement of the image capture device, the movement occurring between capture of the first focus image and a second focus image at a second time,

means for adjusting position of the autofocus window, the adjustment corresponding to the detected movement such that the portion of the object of interest remains substantially stationary within the autofocus window during the detected movement; and

means for capturing the second focus image when the autofocus lens is at a second focus position.

32. A program for focusing an image capture device, stored on computer-readable medium, the program comprising logic configured to perform:

receiving information from a photosensor corresponding to a captured 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 motion occurring between the captured first focus image and a second captured focus image;

adjusting position of the autofocus window, the adjustment corresponding to the detected movement such that the target object remains stationary within the autofocus window during the detected movement; and

receiving the information from the photosensor corresponding to the second captured focus image when the autofocus lens is at a second focus position.

34. A method for focusing an image capture device, comprising moving an autofocus window in response to detected movement of the image capture device.

35. The method of claim 34, wherein the autofocus window is moved during autofocus.

36. The method of claim 34, 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 to the direction of the image capture device movement.

37. A method for focusing an image capture device, comprising:

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

shifting position of an autofocus window in a direction that is opposite to the direction of the image capture device movement.

38. The method of claim 37, further comprising shifting position of the autofocus window in the direction that is substantially opposite to the direction of the image capture device movement wherein a target object remains substantially stationary within the autofocus window during the detected movement.