Image pickup apparatus having non-destructively readable image pickup means for picking up an object image

• US 7,589,774 B2
• Filed: 06/03/2005
• Issued: 09/15/2009
• Est. Priority Date: 08/01/2000
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tashiro, Kazuaki, Kaifu, Noriyuki, Yuki, Osamu
• Primary Examiner(s): Ometz; David L
• Assistant Examiner(s): Quiett; Carramah J
• Application Number:
  US11/143,726
• Publication Number:
  US 20050259170A1
• Time in Patent Office: 1,565 Days
• Field of Search: 378 987- 989, 378 9811- 9812, 348/297, 348/347
• US Class Current: 348/308
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 5/325 Image enhancement, e.g. by subtraction techniques using polyenergetic X-rays

Abstract

An image sensing apparatus including an X-ray image sensing unit having a non-destructive read function, adapted to sense an object image, and a subtractor adapted to sequentially output as a corrected value a difference between a plurality of frames sequentially read out non-destructively from the X-ray image sensing unit and a frame read out before the plurality of frames.

Claims

1. An image pickup apparatus comprising:

image pickup means for picking up an object image, wherein the image pickup means is arranged to be non-destructively readable;

driving means for driving said image pickup means so that a first frame image picked up by said image pickup means is non-destructively read out from said image pickup means when a first time period elapses without reset of said image pickup means during the first time period after said image pickup means is reset, a second frame image picked up by said image pickup means is non-destructively read out from said image pickup means when a second time period elapses without reset of said image pickup means during the second time period after the first time period, and a third frame image picked up by said image pickup means is non-destructively read out from said image pickup means when a third time period elapses without reset of said image pickup means during the third time period after the second time period; and

subtraction means for effecting a subtraction process between said first and second frame images derived by non-destructive reading, and for effecting a subtraction process between said second and third frame images derived by non-destructive reading, and for outputting frame images resulting from the subtraction processes sequentially.

2. An apparatus according to claim 1, further comprising a comparator arranged to compare an output value read out from said image pickup means with a predetermined reference value, wherein a read-out mode of said image pickup means is switched to a normal read-out mode when the output value exceeds the predetermined reference value.

3. An apparatus according to claim 1, wherein said image pickup means includes one or more pixel portions, wherein each pixel portion includes a photoelectric conversion element and a read-out transistor, and wherein each pixel portion is arranged so that the photoelectric conversion element is connected to a control terminal of the read-out transistor.

4. An apparatus according to claim 3, wherein a non-control terminal of the read-out transistor is connected to a load, and wherein the read-out transistor is constructed by an amplifier having a voltage amplification factor of one.

5. An apparatus according to claim 4, wherein the load includes a constant current source or a resistor.

6. An apparatus according to claim 3, wherein the read-out transistor is connected in series to a switching transistor for selecting pixel portions arranged in a row direction.

7. An apparatus according to claim 1, wherein the photoelectric conversion element is connected in series to a reset transistor, and wherein a read-out mode of said image pickup means is switched between a normal read-out mode and a non-destructive read-out mode by controlling the reset transistor in accordance with a mode switching signal.

8. An apparatus according to claim 2, further comprising a counter which is connected to an output of said comparator and which determines a count value representing the number of times that the output value exceeds the predetermined reference value, wherein a read-out mode of said image pickup means is switched from a non-destructive read-out mode to the normal read-out mode when the count value reaches a predetermined value.

9. An apparatus according to claim 2, further comprising storing means for storing a corrected value for every frame image, wherein said storing means is arranged to output the corrected value of a previous frame image for a frame image immediately following the normal read-out mode.