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Shared Row-Specific or Column-Specific Devices in Complementary Metal Oxide Semiconductor Pixel Array

IP.com Disclosure Number: IPCOM000119042D
Original Publication Date: 1997-Nov-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 91K

Publishing Venue

IBM

Related People

Gowda, S: AUTHOR [+5]

Abstract

Disclosed is a new configuration of the devices used in the pixel of a Complementary Metal Oxide Semiconductor (CMOS) imager array to transfer the signal charge from the pixel to the column line. The new configuration shares devices between pixels in order to maximize the light-collecting area of the pixel.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Shared Row-Specific or Column-Specific Devices in Complementary Metal
Oxide Semiconductor Pixel Array

      Disclosed is a new configuration of the devices used in the
pixel of a Complementary Metal Oxide Semiconductor (CMOS) imager
array to transfer the signal charge from the pixel to the column
line.  The new configuration shares devices between pixels in order
to maximize the light-collecting area of the pixel.

      The block diagram of a typical CMOS imager chip is shown in
Fig. 1.  It consists of a pixel array having M rows and N columns of
pixels.  The pixels generate analog signals that are proportional to
the light intensity that they are exposed to.  A possible pixel
circuit is shown in Fig. 2, along with the column line that is used
to drive the signal to the A/D converter.  The pixels are addressed
one row at a  time by the row decoder circuits.  The digital signal
from the A/D is passed through image processing logic and then driven
off-chip.

      The pixel in a CMOS imager array (Fig. 2) consists of a
photosensitive area where the impinging light is converted into
electrical charge and circuitry to read the charge out of the
photosensitive area.  In order to collect charge in the
photosensitive area and then read this charge out, several operations
must be done in  sequence.  Before light can be collected in the
photosensitive area of  the pixel, any residual charge from a
previous image or electrical leakage must be flushed out of the
pixel.  This is done by using the "Reset" signal and transistor M1.
After the signal charge is collected  in the photosensitive region,
it is transferred to the charge storage node through transistor M3.
The signal charge is then read out of the  storage region through
transistor M4, and then onto the column data line  through transistor
M2.  The data on the column line drives the A/D converter circuits.
The devices M1 through M4 are placed in the...