CCD output processing stage that amplifies signals from colored pixels based on the conversion efficiency of the colored pixels
AssigneeNational Semiconductor Corporation
InventorsDavid Michael Boisvert, Andrew Kenneth John McMahon
Life of this patent
Estimating the term…
Abstract
The reduced signal-to-noise ratio of colored pixels that results from a lower conversion efficiency is eliminated by utilizing a programmable gain amplifier which individually applies a gain to the output of each colored pixel so that the maximum signal level of each colored pixel is matched to the maximum input range of an A/D converter.
Claims23
An image processing stage for processing an image signal, the image signal having a plurality of pixel periods, the stage comprising:
- a correlated double sampler (CDS) connectable to receive the image signal, the CDS removing an effect of a reset signal from the image signal in each pixel period to leave a residual signal in each pixel period;
- a digital-to-analog (D/A) converter that converts offset values into offset signals and outputs the offset signals, the residual signal in each pixel period being combined with an offset signal to leave an offset-corrected signal in each pixel period;
- a programmable gain amplifier (PGA) that receives gain values, and amplifies the offset-corrected signal in each pixel period by a gain value of the gain values to form an amplified signal in each pixel period;
- an analog-to-digital (A/D) converter that digitizes the amplified signal in each pixel period to form a digitized value for each pixel period;
- and
- a controller that outputs the offset values to the D/A converter, and the gain values to the amplifier.
An image processing stage that processes an image signal that has a first portion that corresponds with a first color and an adjoining second portion that corresponds with a different second color, the stage comprising:
- a correlated double sampler (CDS) that receives the image signal, removes a reset component from the image signal to leave a residual signal that has a first portion that corresponds with the first color and an adjoining second portion that corresponds with the second color, and outputs the residual signal;
- a digital-to-analog (D/A) converter that converts a first offset value into a first offset signal that corresponds with the first color, and a second offset value into a second offset signal that corresponds with the second color, and outputs the first and second offset signals, the first and second offset signals being different;
- a programmable gain amplifier (PGA) that receives an offset corrected signal, a first gain value that corresponds with the first color, and a second gain value that corresponds with the second color, the offset corrected signal having a first portion that represents a combination of the first portion of the residual signal and the first offset signal, and an adjoining second portion that represents a combination of the second portion of the residual signal and the second offset signal, the PGA amplifying the first portion of the offset corrected signal with the first gain value and the second portion of the offset corrected signal with the second gain value, the first and second gain values being different;
- and
- a controller that outputs the first and second offset values to the D/A converter, and the first and second gain values to the amplifier.
A method for processing an image signal that has a first portion that corresponds with a first color and an adjoining second portion that corresponds with a second color, the method comprising the steps of:
- removing a reset component from the image signal to leave a residual signal that has a first portion that corresponds with the first color and an adjoining second portion that corresponds with the second color, and outputting the residual signal;
- converting a first offset value into a first offset signal that corresponds with the first color and a second offset value into a second offset signal that corresponds with the second color, and outputting the first and second offset signals;
- forming an offset corrected signal that has a first portion that represents a combination of the first portion of the residual signal and the first offset value, and an adjoining second portion that represents a combination of the second portion of the residual signal and the second offset value;
- and
- receiving a first gain value that corresponds with the first color and a second gain value that corresponds with the second color, and amplifying the first portion of the offset corrected signal with the first gain value and the second portion of the offset corrected signal with the second gain value.
Dependencies are inferred from the claim text.