Image sensing device, process for driving such a device and electrical signal generated in such a device

• US 7,528,876 B2
• Filed: 03/06/2004
• Issued: 05/05/2009
• Est. Priority Date: 03/18/2003
• Status: Active Grant

• Current Assignee: Grass Valley Canada (Belden Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Centen, Petrus Gijsbertus Maria, Damstra, Nicolaas Johannes
• Primary Examiner(s): Misleh; Justin P
• Application Number:
  US10/549,133
• Publication Number:
  US 20060284995A1
• Time in Patent Office: 1,886 Days
• Field of Search: None
• US Class Current: 348/308
• 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 25/75 Circuitry for providing, modifying or processing image signals from the pixel array
• CPC Class Codes: H04N 25/771 comprising storage means other than floating diffusion
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

An image sensing device has an image cell with a photo-sensitive element, a detection node and an output pin. Charges accumulated during a first period of time are transferred from the photo-sensitive element to the detection node, thereby obtaining a first voltage, and kept on the detection node which is thus used as a memory. Some moments later, a first value corresponding to the first voltage is generated on the output pin, charges accumulated during a second period of time are transferred from the photo-sensitive element to the detection node, thereby obtaining a second voltage, and a second value is generated on the output pin corresponding to the second voltage. The signal thus generated is also proposed.

Claims

1. A method for driving an image sensing device having an image cell with a photo-sensitive element, a detection node and an output pin, wherein a reference signal and, via an output line, a value present at the output pin, are applied to a comparator, the method comprising the steps of:

transferring charges accumulated during a first period of time from the photo-sensitive element to the detection node, thereby obtaining a first voltage;

generating a first value corresponding to the first voltage;

comparing the first value with the reference signal and determining a signal representing the result of the comparing;

transferring charges accumulated during a second period of time from the photo-sensitive element to the detection node, thereby obtaining a second voltage;

generating a second value corresponding to the second voltage; and

selectively applying one of the first value or the second value to a single buffer, depending on a value of the signal resulting from the comparing;

wherein the first and the second periods of time are subsequent to each other and are nested within a frame or field period, wherein the first period of time is shorter than the second period of time, and wherein the second period of time ends on or after reselling the detection node after reading out the first value.

2. The method according to claim 1, wherein the step of generating the first value is separated from the step of transferring charges accumulated during the first period by approximately the second period.

3. The method according to claim 1, wherein the step of generating the first value occurs more than 20 μ

s later than the step of transferring charges accumulated during the first period and wherein the step of generating the second value occurs less than 20 μ

s later than the step of generating the first value.

4. The method according to claim 3, wherein the step of generating the first value occurs more than 1 ms later than the step of transferring charges accumulated during the first period and wherein the step of generating the second value occurs less than 100 μ

s later than the step of generating the first value.

5. The method according to claim 1, wherein the image sensing device generates a video signal comprising lines separated by horizontal blanking intervals, wherein the step of generating the first value occurs at least one line time minus a blanking interval time later than the step of transferring charges accumulated during the first period and wherein the step of generating the second value occurs less than the blanking interval time later than the step of generating the first value.

6. The method according to claim 1, wherein the image sensing device generates a video signal comprising horizontal blanking intervals and wherein the steps of generating the first value and generating the second value occur during a single horizontal blanking interval.

7. The method according to claim 1, comprising the steps of:

comparing the first value to a reference value prior to reading out the second value;

if the first value is above the reference value, generating an output value based on the first value;

if the first value is below the reference value, generating an output value based on the second value.

8. The method of claim 1, wherein the image sensing device has a first and a second image cell connected to a common output line, wherein the first signals of the first and the second image cell and the second signals of the first and the second image cell are applied to the common output line consecutively.

10. The method of claim 1, further including the steps of:

resetting the detection node prior to transferring charges accumulated during the second period of time from the photo-sensitive element to the detection node; and

applying the signal present in the detection node after resetting to the buffer, for subtraction.

9. Image sensing device having an image cell with a photo-sensitive element, a detection node and an output pin, comprising:

transfer means for transferring charges from the photo-sensitive element to the detection node;

read-out means for generating on the output pin a value based on the detection node voltage;

driving means for controlling the transfer means and the read-out means so that at least two values are generated during an integration period;

a single buffer connected to the output pin; and

comparator means for comparing at least one of said two values to a reference signal and for selectively applying the first value or the second value to the single buffer, depending on a value of the signal resulting from the comparing;

wherein the buffer comprises an integrating amplifier and a means for changing a sign of a value applied to the integrating amplifier.