Spatial non-uniformity correction of a color sensor

Details Spatial non-uniformity correction of a color sensor Spatial non-uniformity correction of a color sensor

1997-05-06

2001-05-01

Garber, Wendy (Department: 2612)

Television

Camera, system and detail

Combined image signal generator and general image signal...

C348S273000, C348S246000

Reexamination Certificate

active

06226034

ABSTRACT:

FIELD OF THE INVENTION
This invention relates in general to image processing and relates more particularly to the correction of spatial non-uniformities of an image produced by a color image sensor.
BACKGROUND OF THE INVENTION
The need for uniformity correction to correct for hue shifts in a single color-filter-array (CFA) image sensor has been recognized. Such sensors uses a regular pattern of colored dyes directly over the pixel sites in order to capture one color component per pixel. One particular pattern used in a digital still camera consists of a regular 2×2 pixel array of kernels. Each kernel consists of two green pixels on one diagonal, and one each of a red and blue pixel on the other diagonal. In order to reconstruct a full RGB (red, green, blue) image, processing is required to reconstruct the missing color information at each pixel site.
The sources of the non-uniformities is due to at least two mechanisms: non-uniformities in the poly-oxide sensor layer, resulting in a spatially varying spectral response, and the non-uniform application of the dyes when they are spun onto the die. The behavior of these non-uniformities is such that they are slowly varying. It has been found that a quadratic model provides an accurate enough of a fit to the actual non-uniformity profile.
When the digital image from a CFA digital camera is transferred to a computer, all spatial and colorimetric processing is done by software on the host computer, as the application does not demand real-time processing. Included in this processing is an algorithm to correct the red and blue color planes for non-uniformities. As these corrections are performed in software by the host computer, multiplications are left in the implementation of the algorithm.
There is a need to correct spatial non-uniformities in a video rate (as opposed to still-frame) color imager, where we wish to process the color information in real-time to be able to support a live color display output. Thus, the processing needs to be performed in real-time. It is therefore essential in such an application to reduce the costs of the implementation such that they can be implemented economically in off-the-shelf components.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a solution to the needs discussed above.
According to an aspect of the present invention, there is provided a color imaging system comprising a color image sensor having a matrix of photosites and a color filter array (CFA) masking the matrix of photosites, such that each photosite captures one color of first, second, and third colors, the CFA constituting a repetitive pattern of the first, second and third colors, the sensor producing a color image signal including a matrix of monocolor pixels corresponding to the color filter array pattern; and a field programmable gate array which is programmed as a spatial non-uniformity color corrector for correcting each of the monocolor pixels of the color image signal by a simplified quadratic function along each image axis.
ADVANTAGEOUS EFFECT OF THE INVENTION
The present invention has the following advantages:
1. Correction of spatial non-uniformities in a CFA color image sensor is done in real time at video rates to support a live color display output.
2. The correction technique is implemented economically in off-the-shelf components.


REFERENCES:
patent: 4298887 (1981-11-01), Rode
patent: 4757385 (1988-07-01), Hieda
patent: 5333055 (1994-07-01), Murata et al.
patent: 5521837 (1996-05-01), Frankle et al.
patent: 5585945 (1996-12-01), Ikeda et al.
patent: 5850472 (1998-12-01), Alston et al.
patent: 5874994 (1999-02-01), Xie et al.

Affiliated with

Also associated with

Rating

Spatial non-uniformity correction of a color sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Spatial non-uniformity correction of a color sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spatial non-uniformity correction of a color sensor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2565663