Method and apparatus for preventing image artifacts

• US 20040218077A1
• Filed: 06/04/2004
• Published: 11/04/2004
• Est. Priority Date: 09/11/2000
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Saunders, Rowland Frederick, Petrick, Scott William, Perry, Douglas I.
• Granted Patent: US 7,561,196 B2
• Time in Patent Office: Days
• US Class Current: 348/297
• CPC Class Codes: H04N 25/30 for transforming X-rays into image signals
• CPC Class Codes: H04N 25/626 Reduction of noise due to residual charges remaining after image readout, e.g. to remove ghost images or afterimages
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30

Abstract

A pixel sensing subsystem for a solid state image sensor includes frame timing logic that produces a frame timing signal indicative of an end-of-frame time and a beginning-of-frame time and reset logic that produces a reset signal for a charge accumulator of pixel sensing electronics. The reset logic asserts the reset signal at least once between the end-of-frame time and the beginning-of-frame time to prevent saturation of the pixel sensing element.

Claims

1-27. -27. (Canceled)

28. A method for preventing image artifacts during image readout from a solid state image sensor, the method including:

indicating an end-of-frame time associated with image readout completion; and

switching a coupling between an image readout capacitor and a pixel sensing element to a coupling between said pixel sensing element and a between frame capacitor after said end-of-frame time.

29. The method of claim 28, further including:

indicating a beginning-of-frame time associated with image readout initiation; and

switching said coupling between said pixel sensing element and said between frame capacitor to said coupling between said image readout capacitor and said pixel sensing element after said beginning-of-frame time.

30. The method of claim 28, wherein said indicating step occurs by a frame timing logic producing a frame timing signal.

31. The method of claim 28, further including producing an output signal indicative of an amount of pixel discharge.

32. The method of claim 31, wherein said output signal is produced by said pixel sensing element.

33. The method of claim 28, wherein said between frame capacitor has a larger capacitance than said imaging capacitor.

34. The method of claim 28, wherein said pixel sensing element includes an operational amplifier.

35. A system for preventing image artifacts during image readout from a solid state image sensor, the system including:

a frame timing signal indicating an end-of-frame time associated with image readout completion;

a between frame capacitor accumulating charge after said end-of-frame time to prevent pixel sensing electronics from saturating; and

a switch coupling said between frame capacitor to a pixel sensing element after said end-of-frame time.

36. The system of claim 35, further including an image readout capacitor accumulating charge during image readout, wherein said frame timing signal also indicates a beginning-of-frame time associated with image readout initiation and said switch couples said pixel sensing element and said image readout capacitor after said beginning-of-frame time.

37. The system of claim 35, further including a frame timing logic producing said frame timing signal.

38. The system of claim 35, further including an output signal indicative of an amount of pixel discharge.

39. The system of claim 35, wherein said output signal is produced by said pixel sensing element.

40. The system of claim 35, wherein said between frame capacitor has a larger capacitance than said image readout capacitor.

41. The system of claim 35, wherein said pixel sensing element includes an operational amplifier.

42. A system for preventing image artifacts during image readout from a solid state image sensor, the system including:

a frame timing signal determining an end-of-frame time associated with image readout completion; and

pixel sensing electronics reading said solid state image sensor to determine at least one dark image after said end-of-frame time to prevent saturation of pixel sensing elements.

43. The system of claim 42, wherein said frame timing signal also determines a beginning-of-frame time associated with image readout initiation.

44. The system of claim 43, wherein said pixel sensing electronics read said image sensor to determine said at least one dark image between said end-of-frame time and said beginning-of-frame time.

45. The system of claim 42, further including an image processing back end discarding said at least one dark image.

46. The system of claim 43, wherein said pixel sensing electronics read said image sensor to determine said at least one live image between said beginning-of-frame time and said end-of-frame time.

47. The system of claim 46, wherein said pixel sensing electronics read said image sensor continuously.