Illumination light color estimating method of obtaining white balance and image sensing apparatus

Claim 3

A method according to claim 1 , wherein clip processing is executed to make the estimated illumination light color fall within a predetermined range.

Claim 4

A method according to claim 1 , wherein an image formed from the three primary color signals is segmented into a plurality of blocks, the signal of interest is defined from the three primary color signals in each block, the white point is obtained in each black, and an average value of coordinate points corresponding to the white points of each block is estimated as the illumination light color.

Claim 5

A method according to claim 2 , wherein a weight used to obtain the average value is determined on the basis of brightness information of the three primary color signals.

Claim 6

A method according to claim 4 , wherein the weight used to obtain the average value increases as a degree of color saturation represented by average color data of the block decreases.

Claim 7

An image sensing apparatus which estimates an illumination light color using three primary color signals to obtain white balance, comprising: means for acquiring average values of the three primary color signals from an image sensing element, the three primary color signals having signal levels equalized with respect to illumination light having a predetermined color temperature in a predetermined image sensing area of the image sensing element; means for setting the signal with the higher level, one of red and blue signals contained in the average value, as a signal of interest; means for reducing the red or blue signal in the signal of interest together with a green signal at the same ratio when the green signal is larger than a value obtained by dividing a resultant value by the green signal, and for reducing the red or blue signal in the signal of interest when the green signal is smaller than the resultant value, the resultant value being obtained by multiplying the red signal by the blue signal; and means for obtaining a white point at which a geometric average of the signal of interest obtained by the reduction processing has the same level as that of the green signal and estimating a color corresponding to the white point as the illumination light color.

Claim 8

An image sensing apparatus which estimates an illumination light color using three primary color signals to obtain white balance, comprising: means for acquiring average values of the three primary color signals from an image sensing element, the three primary color signals having signal levels equalized with respect to illumination light having a predetermined color temperature in a predetermined image sensing area of the image sensing element; means for setting the signal with the higher level, one of red and blue signals contained in the average value, as a signal of interest; means for reducing the red or blue signal in the signal of interest together with a green signal at the same ratio when the green signal is larger than a value obtained by dividing a resultant value by the green signal, and for reducing the red or blue signal in the signal of interest when the green signal is smaller than the resultant value, the resultant value being obtained by multiplying the red signal by the blue signal; and means for obtaining a white point at which a geometric average of the signal of interest obtained by the reduction processing has the same level as that of the green signal and estimating a color corresponding to the white point as the illumination light color.

Claim 11

An image sensing apparatus which estimates an illumination light color using three primary color signals to obtain white balance, comprising: means for acquiring average values of the three primary color signals from an image sensing element, the three primary color signals having signal levels equalized with respect to illumination light having a predetermined color temperature in a predetermined image sensing area of the image sensing element; means for executing reduction processing of one of the signal levels of the average values of the three primary color signals to make a value of a color temperature calculated from the average values close to the value of the predetermined color temperature; means for obtaining first and second color coordinate value information to stop the reduction processing when the current light source is to be a first and a second illumination light color; means for obtaining, from the three primary color signals, evaluation value information representing whether the current light source is close to the first or second illumination light source; means for determining on the basis of the evaluation value information whether the current light source has the first or second illumination light color; and means for estimating the illumination light color from color coordinate value information of the determined illumination light color and the received average values of the three primary color signals.

Claim 12

An image sensing apparatus which estimates an illumination light color using three primary color signals to obtain white balance, comprising: means for acquiring average values of the three primary color signals from an image sensing element, the three primary color signals having signal levels equalized with respect to illumination light having a predetermined color temperature in a predetermined image sensing area of the image sensing element; means for executing reduction processing of one of the signal levels of the average values of the three primary color signals to make a value of a color temperature calculated from the average values close to the value of the predetermined color temperature; means for obtaining first and second color coordinate value information to stop the reduction processing when the current light source is to be a first and a second illumination light color; means for obtaining, from the three primary color signals, evaluation value information representing whether the current light source is close to the first or second illumination light source; means for determining on the basis of the evaluation value information whether the current light source has the first or second illumination light color; and means for estimating the illumination light color from color coordinate value information of the determined illumination light color and the received average values of the three primary color signals.