Television – Camera – system and detail – Solid-state image sensor
Reexamination Certificate
1999-11-12
2004-03-02
Garber, Wendy R. (Department: 2712)
Television
Camera, system and detail
Solid-state image sensor
C348S296000
Reexamination Certificate
active
06700611
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an amplifying solid-state imaging device and a method for driving the same.
An amplifying solid-state imaging device, as well as a CCD solid-state imaging device, adopts “electronic shuttering” as a sort of electronic diaphragm. The “electronic shuttering” operation is performed to reset a signal charge storage section just before a photodiode in each pixel starts to store the signal charge, which has been created by the photodiode itself through photoelectric conversion, thereby making the charge storage period of the photodiode variable. The signal charge stored in pixels is read out on a row-by-row basis responsive to a horizontal sync signal. Thus, the electronic shuttering operation is also performed on the row-by-row basis (which is called a “focal plane operation”). More specifically, the electronic shuttering operation is performed on a certain row and then the signal charge starts to be stored. And after a predetermined time has passed since the start of charge storage, a signal readout operation is performed. When the readout operation is started, the storage section is reset again for the readout. The “predetermined time” defines the charge storage period of each photodiode and is of an equal length for every row. Accordingly, supposing each pixel is receiving light with the same intensity, the same quantity of charge will be stored on each and every row theoretically speaking.
FIG. 1
illustrates a schematic configuration of a conventional amplifying solid-state imaging device
100
. In the device
100
, an imaging section is made up of a plurality of pixels
102
arranged in columns and rows. Each of these pixels
102
includes a photodiode for storing charge in a quantity corresponding to the amount of light received. As shown in
FIG. 1
, a row select encoder
103
for selecting one pixel row after another from the imaging section is disposed on the right-hand side of the imaging section. In the example illustrated in
FIG. 1
, the number of pixel rows is m, which is equal to or larger than two. The row select encoder
103
includes the number m of row selectors that are connected in series to each other. An i
th
(where 1≦i≦m) row selector generates a reset signal for the electronic shuttering operation at a predetermined time, and then sends the signal out to all the pixels
102
belonging to the i
th
row. The row selectors included in the row select encoder
103
output the reset signal for the electronic shuttering operation at respective times, which are different from each other among the rows. That is to say, the reset signal is sequentially output in the descending order, i.e., from the first through m
th
pixel rows.
On the other hand, the row selecting operation for readout (i.e., an ordinary row selection) is also performed sequentially by the number m of row selectors. The interval between the electronic shuttering and readout operations is preset at the same length for every row. The signal read out from a selected row is supplied by a column select driver
107
to an output buffer
111
, from which the signal is output as a pixel signal.
When the electronic shuttering operation is performed, the photodiode within each pixel
102
has the potential thereof compulsorily reset at a predetermined level (which will be called a “reset potential” in this specification). The reset potential is supposed to be the same in each and every pixel
102
as a matter of principle. However, the present inventors found that since a reset potential on a certain row could shift into a different reset potential on another row, horizontal noise might appear on the screen as a result. The horizontal noise always appears on a particular set of rows on the screen, thus degrading the resultant image quality.
SUMMARY OF THE INVENTION
An object of the present invention is providing (1) an amplifying solid-state imaging device that can substantially eliminate the horizontal noise resulting from the electronic shuttering operation and (2) a method for driving the device.
To achieve this object, according to the present invention, a reset signal for electronic shuttering is generated and sent out at a time different from a conventionally defined one such that the reset signal for electronic shuttering is not provided while a pixel row is being selected to read a signal therefrom. As a result, the reset potentials, which would otherwise be variable depending on whether or not signal reading is being performed on other rows, can be equalized among all the pixel rows, thus eliminating the cause of the horizontal noise.
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Garber Wendy R.
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
Wilson Jacqueline
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