Dual sensitivity image sensor

• US 20060050163A1
• Filed: 09/01/2005
• Published: 03/09/2006
• Est. Priority Date: 06/15/1999
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Barna, Sandor, Wang, Yibing Michelle
• Granted Patent: US 7,605,855 B2
• Time in Patent Office: Days
• US Class Current: 348/308
• CPC Class Codes: H04N 25/585 with pixels having different sensitivities within the sensor, e.g. fast or slow pixels or pixels having different sizes
• CPC Class Codes: H04N 25/59 by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 25/78 Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

A system of taking images of different sensitivities at the same time uses both an image sensor, and an auxiliary part to the image sensor. The image sensor element can be a photogate, and the auxiliary part can be the floating diffusion associated with the photogate. Both the photogate and the floating diffusion accumulate charge. Both are sampled at different times. The floating diffusion provides a lower sensitivity amount of charge than the photogate itself. The system can have a photogate and floating diffusion in each pixel along with a select transistor, a reset transistor, and a follower transistor. All of this circuitry can be formed of CMOS for example. The system can also operate in a column/parallel mode, where each column of the photo sensor array can have a column signal processor which samples and holds the reset signal, the floating diffusion signal and the photogate signal.

Claims

1-32. -32. (canceled)

33. An image sensing pixel comprising:

a first image sensing portion having a first light sensitivity and producing charge based on an amount of incident light; and

a second image sensing portion having a second sensitivity to light and producing charge based on the amount of incident light; and

an image processing portion having circuitry that produces an output indicative of both an amount of charge received by said first image sensing portion, and an amount of charge received by said second image sensing portion.

34. The pixel according to claim 33 wherein said first image sensing portion is a photogate, and said second image sensor is a floating diffusion region associated with said photogate in each said pixel.

35. The pixel according to claim 34 further comprising a transfer gate, located between said photogate and said floating diffusion region, which is selectively operable to separates charge stored in said photogate from said floating diffusion region and allow charge from said photogate to flow to said floating diffusion region.

36. The pixel according to claim 34 further comprising, in each said pixel, a reset transistor, connected between a reset voltage terminal and said floating diffusion region, and which operates to reset a value of said floating diffusion region to a specified level.

37. The pixel according to claim 34 wherein said image processing portion includes a plurality of sample and hold circuits.

38. The pixel according to claim 37 wherein said plurality of sample and hold circuits include a first sample and hold circuit for storing a reset signal level, a second sample and hold circuit for storing a photogate image signal level, and a third sample and hold circuit for storing a floating diffusion image signal level.

39. The pixel according to claim 38 further comprising a circuit for outputting a combination of said photogate signal level and floating diffusion level.

40. The pixel according to claim 34 further comprising a controlling circuit, operating to control times of integration of said photogate and said floating diffusion, such that said floating diffusion integrates for a same time or less time than an integration time of said photogate, and such that at least part of the time of integration of said floating diffusion overlaps a time of integration of said photogate.

41. A method of imaging, comprising:

obtaining both a high sensitivity signal and a low sensitivity signal in each of a plurality of pixels, wherein said high sensitivity signal is obtained by a first image sensing portion within each pixel, and said low sensitivity signal is obtained by a first image sensing portion within each pixel, said first and second image sensing portions having different image sensitivities; and

outputting both of said high sensitivity signal and low sensitivity signal from each of said plurality of pixels.

42. A method as in claim 41 wherein said first image sensing portion is a photogate and said second image sensing portion is a floating diffusion region, said floating diffusion region being further adapted to receive a charge from said photogate.

43. A method as in claim 42 further comprising:

obtaining a signal by resetting and determining a reset signal level of the floating diffusion region;

determining an integrated value indicating the level of the floating diffusion region, obtained by integrating a scene for a first specified time;

obtaining a second integrated level, obtained by integrating the scene in said photogate for a second specified time; and

outputting from each pixel reset, photogate, and floating diffusion signal levels.

44. A method as in claim 43 further comprising the step of combining at least two of said pixel reset, photogate and floating diffusion signal levels to produce an output signal.

45. A method as in claim 43 wherein said first integration time of said floating diffusion region is less than or equal to said second integration time of said photogate.

46. A method as in claim 43 wherein said obtaining and determining comprises first sampling said reset level, then sampling said floating diffusion level, and then transferring a photogate level to said floating diffusion level and sampling said floating diffusion level again to obtain a photogate level.