Imaging device

• US 8,629,927 B2
• Filed: 04/09/2008
• Issued: 01/14/2014
• Est. Priority Date: 04/09/2008
• Status: Active Grant

• Current Assignee: HL Klemove Corporation
• Original Assignee: Gentex Corporation
• Inventors: Bechtel, Jon H., Andrus, Jeremy C.
• Primary Examiner(s): Ye, Lin
• Assistant Examiner(s): HSU, AMY R
• Application Number:
  US12/082,215
• Publication Number:
  US 20090256938A1
• Time in Patent Office: 2,106 Days
• Field of Search: 348/302, 348/311, 348/294
• US Class Current: 348/302
• CPC Class Codes: B60R 2001/1253 with cameras, video cameras or video screens
• CPC Class Codes: H04N 25/57 Control of the dynamic range
• CPC Class Codes: H04N 25/575 with a response composed of multiple slopes
• CPC Class Codes: H04N 25/589 with different integration times, e.g. short and long exposures
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors

Abstract

The present invention relates to improved imaging devices having high dynamic range and to monitoring and automatic control systems incorporating the improved imaging devices.

Claims

1. An imaging device, comprising:

an array of four transistor (4 T) pixels wherein each active 4 T pixel of said array of 4 T pixels is independently controlled to select one of a plurality of integration periods of a frame period, each said 4 T pixel comprising;

a transfer gate, wherein said transfer gate is independently controllable with respect to any other transfer gates associated with any other active 4 T pixel of said array of 4 T pixels, such that said transfer gate controls selection of one said integration period from said plurality of integration periods for said 4 T pixel;

wherein a non-digitized sample reading of the light is taken and compared to a threshold value to determine one of said integration period from said plurality of integration periods for said 4 T pixel.

2. An imaging device as in claim 1 wherein a pre-sample integration period is used to initiate a selectable integration period.

3. An imaging device as in claim 2 wherein time is provided within at least one image acquisition sequence to take a pre-sample reading to determine whether or not to select the longest of the available integration periods.

4. An imaging device as in claim 2 wherein a first time to acquire a pre-sample reading plus a second time associated with the presently selected longest integration period fit within a longest image acquisition sequence time interval.

5. An imaging device as in claim 3 wherein a first time to acquire a pre-sample reading plus a second time associated with the presently selected longest integration period fit within a longest image acquisition sequence time interval.

6. An imaging device as in claim 5 wherein said longest image acquisition sequence time interval is less than 0.069 seconds.

7. An imaging device as in claim 5 wherein said longest image acquisition sequence time interval is less than 0.039 seconds.

8. An imaging device as in claim 6 wherein the determination to reset a given pixel to initiate a selected integration period is based at least in part on a result of a compare task of an indication of the accumulated charge on said given pixel to a threshold level after said pre-sample integration.

9. An imaging device as in claim 1 wherein the execution of tasks following a first pre-sample to select an integration period for a given pixel is confined to a period during which the longest integration may take place for said pixel.

10. An imaging device as in claim 9 wherein reset to begin an integration period is bypassed for a pixel if a recorded indication of an active integration period for said pixel indicates that an integration period is selected and in progress for said pixel.

11. An imaging device as in claim 1 wherein a parallel addressable group of pixels constitutes a substantial portion of a row of pixels in said array of pixels.

12. An imaging device as in claim 1 wherein a value resulting from a pre-sample integration period is compared against a threshold for selecting a desired integration period.

13. An imaging device as in claim 12 wherein compare task is analog and is performed at at least one location generally external to said array of pixels.

14. An imaging device as in claim 1 wherein four or fewer bits of data are stored for each pixel in memory.

15. An imaging device as in claim 14 wherein said memory is fabricated on a same integrated circuit substrate as said array of pixels.

16. An imaging device as in claim 15 wherein dynamic memory is used for memory associated with each pixel.

17. An imaging device as in claim 16 wherein said dynamic memory incorporates capacitive elements to store a bit value.

18. An imaging device as in claim 16 wherein refresh tasks for said dynamic memory is scheduled along with other image acquisition tasks.

19. An imaging device as in claim 1 wherein only one digitized reading of an integrated charge level is taken for each pixel and digitized readings are taken for pixels in a predetermined order.

20. An imaging device as in claim 1 wherein different sets of selectable integration periods are provided for different image acquisition sequences.

21. An imaging device as in claim 20 wherein a first of said set of selectable integration periods is utilized in ambient lighting conditions above a threshold and a second of said set of selectable integration periods is utilized in ambient light conditions below a threshold.

22. An imaging device as in claim 1 wherein all integration periods which may be selected for a pixel end at the same time.

23. An imaging device as in claim 1 wherein readout of parallel addressable groups of pixels is performed at periodic intervals during an image acquisition sequence.

24. An imaging device as in claim 1 wherein a ratio of a longest to a shortest available integration period is greater than 3500.

25. An imaging device as in claim 1 wherein a ratio of any available integration period other than a shortest to a next shorter available integration period is less than 10.

26. An imaging device as in claim 1 wherein said available integration periods decrease ratio-metrically.

27. An imaging device as in claim 1 wherein said available integration periods decrease geometrically.

28. An imaging device as in claim 1 wherein a sample reading is taken with said pixel and a decision to initiate a particular integration period is at least partially based on a comparison of said sample reading from said pixel against a threshold value.

29. An imaging device as in claim 1 wherein said pixel is reset by switching said transfer gate and a reset transistor to a conductive state, such that a different said selectable integration period is selected.

30. An imaging device as in claim 1 wherein said pixel is sampled by switching said transfer gate to a conductive state, such that a light induced charge is transferred.

31. An imaging device, comprising:

an array of four transitory (4 T) pixels comprising at least a first row of 4 T pixels, wherein said first row comprise a plurality of 4 T pixels, each of said plurality of 4 T pixels configured to be independently controlled to select one of a plurality of integration periods of a frame period, each of said plurality of 4 T pixels comprising;

a transfer gate, wherein said transfer gate of a first 4 T pixel in said first row is independently controllable with respect to said transfer gate of at least one other active 4 T pixel of said first row, such that said transfer gate controls selection of one said integration period from said plurality of integration periods for each said 4 T pixel;

wherein a non-digitized sample reading of the light is taken and compared to a threshold value to determine one of said integration period from said plurality of integration periods for said 4 T pixel.

32. An imaging device as in claim 31 wherein a pre-sample integration period is used to initiate a selectable integration period.

33. An imaging device as in claim 32 wherein a first time to acquire a pre-sample reading plus a second time associated with a presently selected longest integration period fit within a longest image acquisition sequence time interval.

34. An imaging device as in claim 32 wherein time is provided within at least one image acquisition sequence to take a pre-sample reading to determine whether or not to select a longest available integration period.

35. An imaging device as in claim 34 wherein a first time to acquire a pre-sample reading plus a second time associated with the presently selected longest integration period fit within a longest image acquisition sequence time interval.

36. An imaging device as in claim 35 wherein said longest image acquisition sequence time interval is less than approximately 0.069 seconds.

37. An imaging device as in claim 35 wherein said longest image acquisition sequence time interval is less than approximately 0.039 seconds.

38. An imaging device as in claim 32 wherein the determination to reset a given pixel to initiate said selected integration period is based at least in part on a result of a compare task of an indication of the accumulated charge on said given pixel to a threshold level after said pre-sample integration.

39. An imaging device as in claim 31 wherein the execution of tasks following a first pre-sample to select an integration period for a given pixel is confined to a period during which the longest integration may take place for said pixel.

40. An imaging device as in claim 31 wherein a parallel addressable group of pixels constitutes a substantial portion of said first row of pixels in said array of pixels.

41. An imaging device as in claim 31 wherein a value resulting from a pre-sample integration period is compared against a threshold for selecting a desired integration period.

42. An imaging device as in claim 41 wherein a compare task is analog and is performed at at least one location at least partially external to said array of pixels.

43. An imaging device as in claim 31 wherein four or fewer bits of data are stored for each pixel in memory.

44. An imaging device as in claim 43 wherein said memory is fabricated on a same integrated circuit substrate as said array of pixels.

45. An imaging device as in claim 31 wherein only one digitized reading of an integrated charge level is taken for each pixel, and said digitized readings are taken for pixels in a predetermined order.

46. An imaging device as in claim 31 wherein different sets of selectable integration periods are provided for different image acquisition sequences.

47. An imaging device as in claim 46 wherein a first of said sets of selectable integration periods is utilized in ambient lighting conditions above a threshold and a second of said sets of selectable integration periods is utilized in ambient light conditions below a threshold.

48. An imaging device as in claim 31 wherein all integration periods which may be selected for a pixel of said array of pixels end at approximately the same time.

49. An imaging device as in claim 31 wherein a reset to begin an integration period is bypassed for a pixel of said array of pixels if a recorded indication of an active integration period for said pixel indicates that an integration period is selected and in progress for said pixel.

50. An imaging device as in claim 31 wherein dynamic memory is used for memory associated with each pixel.

51. An imaging device as in claim 50 wherein said dynamic memory incorporates capacitive elements to store a bit value.

52. An imaging device as in claim 50 wherein refresh tasks for said dynamic memory is scheduled along with other image acquisition tasks.

53. An imaging device as in claim 31 wherein readout of parallel addressable groups of pixels of said array of pixels is performed at periodic intervals during an image acquisition sequence.

54. An imaging device as in claim 31 wherein a ratio of a longest to a shortest available integration period is greater than 3500.

55. An imaging device as in claim 31 wherein a ratio of any available integration period other than a shortest to a next shorter available integration period is less than 10.

56. An imaging device as in claim 31 wherein said available integration periods decrease ratio-metrically.

57. An imaging device as in claim 31 wherein said available integration periods decrease geometrically.

58. An imaging device as in claim 31 wherein a sample reading is taken with said pixel and a decision to initiate a particular integration period is at least partially based on a comparison of said sample reading from said pixel against a threshold value.

59. An imaging device as in claim 31 wherein said pixel is reset by switching said transfer gate and a reset transistor to a conductive state, such that a different said selectable integration period is selected.

60. An imaging device as in claim 31 wherein said pixel is sampled by switching said transfer gate to a conductive state, such that a light induced charge is transferred.