US 7,256,828 B2 · Weighted gradient based and color corrected interpolation

Abstract

The apparatus and method invented are operating upon a digital image signal obtained from an image sensor. The sensor is covered with different colored filters and is only able to record the color transmitted through each specific filter into the photosite or pixel. This type of sensor is known as a color filter array or CFA sensor. The different colored filters are arranged in a predefined pattern across the sensor. To obtain a full color image the missing color information is estimated by a set of weighed values obtained by an inverted gradient function. The set of weighted values is found from the neighboring pixels in the four compass directions, north, east, west and south or is found horizontally and vertically. The surrounding pixels are corrected by the chrominance channel to better fit the center pixel in the luminance channel, prior to using the gradient functions. The chrominance channel is interpolated in a similar manner and is also corrected to better fit the center pixel before the inverted gradient functions are applied.

Claims64

Dependent claims

A method to obtain a full color image by estimating the missing color information of a single sensor camera comprising:

providing an exposure unit comprising a color filter array (CFA), an analog/digital converter of the raw image, an interpolation unit, and a color processing unit;
interpolating luminance channel comprising
computing inverted and normalized gradient functions in the four compass directions using luminance and chrominance data;
and then
interpolating the luminance considering luminance and chrominance using results of said computing inverted and normalized gradient functions;
interpolating chrominance channel;
correcting luminance channel;
and
correcting chrominance channel.

6 more elements

A method to obtain a full color image by estimating the missing color information of a single sensor camera comprises:

providing an exposure unit comprising a C-M-Y color filter array (CFA), an analog/digital converter of the raw image, an interpolation unit, and a color processing unit;
interpolating luminance channel used as proxy for magenta comprising:
computing inverted and normalized gradient functions in the four compass directions using luminance and chrominance data;
and then
interpolating the luminance considering luminance and chrominance using results of said computing inverted and normalized gradient functions;
interpolating chrominance channel used as proxy for yellow and cyan;
correcting luminance channel;
and
correcting chrominance channel.

6 more elements

A method to obtain a full color image by estimating the missing color information of a single sensor camera comprising:

providing an exposure unit comprising a Diagonal Bayer Pattern color filter array (CFA), an analog/digital converter of the raw image, an interpolation unit, and a color processing unit;
interpolating luminance channel used as proxy for green comprising
computing inverted and normalized gradient functions in the four compass directions using luminance and chrominance data;
and then
interpolating the luminance considering luminance and chrominance data using results of said computing inverted and normalized gradient functions in the four compass directions using luminance and chrominance data;
interpolating chrominance channel used as proxy for red and blue;
correcting luminance channel;
and
correcting chrominance channel.

6 more elements

A method to obtain a full color image by estimating the missing color information of a single sensor camera comprising:

providing an exposure unit comprising a color filter array (CFA), an analog/digital converter of the raw image, an interpolation unit, and a color processing unit;
computing gradient functions in specific directions using luminance and chrominance data to prepare an interpolation of the luminance channel;
interpolating the luminance considering luminance and
chrominance data using results of said computing gradient functions in specific directions using luminance and chrominance data to prepare an interpolation of the luminance channel;
estimating chrominance at opposite chrom inance locations using luminance and chrominance data considered;
computing gradient functions in specific directions, using chrominance and luminance data to prepare an interpolation of the chrominance channel;
interpolating chrominance at luminance locations considering chrominance and luminance data using results from said computing gradient functions in specific directions, using chrominance and luminance data to prepare an interpolation of the chrominance channel;
computing two gradient functions, horizontally and vertically, using information from all color channels to prepare a correction of the luminance channel;
correcting the luminance channel horizontally and vertically if the gradient functions are not equal;
computing gradient functions using enhanced chrominance and luminance data to prepare a correction of the chrominance channel.;
and
interpolating chrominance determining correction of chrominance both at luminance and opposite chrominance locations considering chrominance and enhanced luminance data using results from said computing gradient functions using enhanced chrominance and luminance data to prepare a correction of the chrominance channel.

9 more elements

Dependencies are inferred from the claim text.

Weighted gradient based and color corrected interpolation

Life of this patent

Weighted gradient based and color corrected interpolation

Life of this patent

Abstract

Claims64