Apparatus and method for reducing image blur in a digital camera

• US 20040130628A1
• Filed: 01/08/2003
• Published: 07/08/2004
• Est. Priority Date: 01/08/2003
• 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.
• Granted Patent: US 7,212,230 B2
• Time in Patent Office: Days
• US Class Current: 348/208.4
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations
• CPC Class Codes: H04N 23/6811 based on the image signal
• CPC Class Codes: H04N 23/684 performed by controlling the image sensor readout, e.g. by controlling the integration time

Abstract

A digital camera delays the capture of a digital image after image capture has been requested until the motion of the digital camera satisfies a motion criterion. The digital camera thereby reduces image blur that would otherwise occur due to camera motion.

Claims

1. A digital camera, comprising:

an input control to initiate capture of a digital image;

a motion tracking subsystem responsive to the input control to track motion of the digital camera, an output of the motion tracking subsystem indicating the quantity of motion of the digital camera as a function of time; and

control logic configured to delay capture of the digital image until the output of the motion tracking subsystem satisfies a motion criterion.

2. The digital camera of claim 1, wherein the control logic is further configured to capture the digital image upon the expiration of a predetermined timeout period measured from an actuation of the input control, when the output of the motion tracking subsystem fails to satisfy the motion criterion within the predetermined timeout period.

3. The digital camera of claim 1, wherein the control logic is configured to capture the digital image while the output of the motion tracking subsystem is decreasing, when the output of the motion tracking subsystem does not satisfy the motion criterion.

4. The digital camera of claim 1, wherein the input control comprises a pushbutton switch having at least a first position and a second position, the first position activating the motion tracking subsystem, the second position requesting capture of the digital image.

5. The digital camera of claim 1, wherein the motion criterion comprises the output of the motion tracking subsystem reaching an approximate local minimum.

6. The digital camera of claim 5, wherein the output of the motion tracking subsystem reaching an approximate local minimum comprises the output of the motion tracking subsystem being below a threshold.

7. The digital camera of claim 6, wherein the control logic is configured to select as the threshold a value lying between a minimum and a maximum of the output of the motion tracking subsystem.

8. The digital camera of claim 7, wherein the input control comprises a pushbutton switch having at least a first position and a second position, the first position activating the motion tracking subsystem, the second position requesting capture of the digital image, and the minimum and the maximum are determined during an interval between an actuation of the input control to the first position and an actuation of the input control to the second position.

9. The digital camera of claim 6, wherein the control logic is configured to select the threshold, at least in part, based on a current focal length of a lens of the digital camera.

10. The digital camera of claim 6, wherein the control logic is configured to select the threshold, at least in part, based on a current shutter speed setting of the digital camera.

11. The digital camera of claim 6, wherein the input control comprises a pushbutton switch having at least a first position and a second position, the first position activating the motion tracking subsystem, the second position requesting capture of the digital image, and the control logic is configured to select the threshold, at least in part, based on an interval between an actuation of the input control to the first position and an actuation of the input control to the second position.

12. The digital camera of claim 11, wherein the control logic is further configured to increase the threshold with the passage of time after the actuation of the input control to the second position.

13. The digital camera of claim 6, wherein the control logic is configured to select the threshold, at least in part, based on prior measurements of the motion of the digital camera.

14. The digital camera of claim 1, wherein the motion tracking subsystem comprises:

an imaging module to convert optical images to digital images, the imaging module being capable of operation in a video preview mode, the video preview mode producing a series of digital preview frames, a portion of each digital preview frame comprising a motion measurement region; and

motion measurement logic configured to measure the motion of the digital camera by comparing at least one picture element in a first digital preview frame with at least one picture element in a second digital preview frame, the at least one picture element in each of the first and second digital preview frames lying within the motion measurement region of that digital preview frame.

15. The digital camera of claim 14, wherein the imaging module comprises one of a CCD sensor array and a CMOS sensor array.

16. The digital camera of claim 14, wherein the video preview mode of the digital camera is substantially the same as that employed during autofocus, and the motion measurement region coincides with an autofocus region within which autofocus is performed on a different series of digital preview frames.

17. The digital camera of claim 14, wherein the motion measurement region of each of the first and second digital preview frames comprises a central portion of that digital preview frame.

18. The digital camera of claim 14, wherein the motion measurement region of each of the first and second digital preview frames comprises a peripheral portion of that digital preview frame.

19. The digital camera of claim 14, wherein the motion measurement logic is configured to apply a window function that attenuates an edge sub-region of the motion measurement region of each of the first and second digital preview frames.

20. The digital camera of claim 14, wherein the at least one picture element in each of the first and second digital preview frames comprises a horizontal set of picture elements.

21. The digital camera of claim 14, wherein the at least one picture element in each of the first and second digital preview frames comprises a vertical set of picture elements.

22. The digital camera of claim 14, wherein the motion measurement logic is configured to compute horizontal and vertical motion components.

23. The digital camera of claim 1, wherein the motion tracking subsystem comprises at least one accelerometer.

24. The digital camera of claim 1, wherein the motion tracking subsystem comprises at least one gyroscope.

25. The digital camera of claim 1, wherein the output of the motion tracking subsystem comprises the square root of the sum of a horizontal motion component squared and a vertical motion component squared.

26. The digital camera of claim 1, wherein the output of the motion tracking subsystem comprises the sum of the absolute value of a horizontal motion component and the absolute value of a vertical motion component.

27. A method for reducing image blur in a digital camera, comprising:

tracking motion of the digital camera in response to a first input signal; and

delaying capture of a digital image, following receipt of a second input signal, until the motion of the digital camera satisfies a motion criterion.

28. The method of claim 27, wherein the first and second input signals are one and the same input signal.

29. The method of claim 27, further comprising:

capturing the digital image upon the expiration of a predetermined timeout period measured from receipt of the second input signal, when the motion of the digital camera does not satisfy the motion criterion within the predetermined timeout period.

30. The method of claim 27, further comprising:

capturing the digital image while the digital camera is decelerating, when the motion of the digital camera does not satisfy the motion criterion.

31. The method of claim 27, wherein the motion criterion comprises the motion of the digital camera reaching an approximate local minimum.

32. The method of claim 31, wherein the motion of the digital camera reaching an approximate local minimum comprises the motion of the digital camera being below a threshold.

33. The method of claim 32, wherein the threshold is selected to be a value lying between a minimum and a maximum motion of the digital camera measured during an interval between receipt of the first input signal and receipt of the second input signal.

34. The method of claim 32, wherein the threshold is selected, at least in part, based on a current focal length of a lens of the digital camera.

35. The method of claim 32, wherein the threshold is selected, at least in part, based on a current shutter speed setting of the digital camera.

36. The method of claim 32, wherein the threshold is selected, at least in part, based on an interval between receipt of the first input signal and receipt of the second input signal.

37. The method of claim 32, wherein the threshold is increased with the passage of time following receipt of the second input signal.

38. The method of claim 32, wherein the threshold is selected, at least in part, based on prior measurements of the motion of the digital camera.

39. The method of claim 27, wherein tracking motion of the digital camera comprises:

acquiring a series of digital preview frames in a video preview mode of the digital camera, a portion of each digital preview frame comprising a motion measurement region; and

comparing at least one picture element in a first digital preview frame with at least one picture element in a second digital preview frame, the at least one picture element in each of the first and second digital preview frames lying within the motion measurement region of that digital preview frame.

40. The method of claim 39, wherein the video preview mode of the digital camera is substantially the same as that employed during autofocus, and the motion measurement region coincides with an autofocus region within which autofocus is performed on a different series of digital preview frames.

41. The method of claim 39, wherein the motion measurement region of each of the first and second digital preview frames comprises a central portion of that digital preview frame.

42. The method of claim 39, wherein the motion measurement region of each of the first and second digital preview frames comprises a peripheral portion of that digital preview frame.

43. The method of claim 39, further comprising:

applying a window function that attenuates an edge sub-region of the motion measurement region of each of the first and second digital preview frames.

44. The method of claim 39, wherein the at least one picture element in each of the first and second digital preview frames comprises a horizontal set of picture elements.

45. The method of claim 39, wherein the at least one picture element in each of the first and second digital preview frames comprises a vertical set of picture elements.

46. The method of claim 39, wherein comparing at least one picture element in a first digital preview frame with at least one picture element in a second digital preview frame comprises computing horizontal and vertical motion components.

47. The method of claim 27, wherein tracking motion of the digital camera comprises measuring the motion of the digital camera using at least one accelerometer.

48. The method of claim 27, wherein tracking motion of the digital camera comprises measuring the motion of the digital camera using at least one gyroscope.

49. A digital camera, comprising:

means for initiating capture of a digital image;

means for tracking motion of the digital camera responsive to the means for initiating capture of a digital image, an output of the means for tracking motion of the digital camera indicating the quantity of motion of the digital camera as a function of time; and

means for delaying capture of the digital image until the output of the means for tracking motion of the digital camera satisfies a motion criterion.