White balance by tunable spectral responsivities.
The development of color pixels in modern digital imaging has led to devices in which color detection is not based on the use of physical color filters but relies on the wavelength dependence of the silicon absorption coefficient in the visible range. In some of these devices the responsivity of each color channel can be electrically tuned by changing the applied voltages. Exploiting this feature, this paper presents a new method of white balance that compensates for changes in the illuminant spectrum by changing accordingly the spectral responsivities, and therefore the native color space, of the detector. Different sets of responsivities corresponding to the different RGB color channels can be selected, depending on the illuminant, in order to keep the chromatic components of a white object independent of the illuminant. An implementation of this method with the transverse field detector, a color device with tunable spectral responsivities, is discussed. Experimental data show that the method is effective for three spectral sources that are strongly different from a chosen reference source. The color error in a perceptive color space after the subsequent color correction (specific for each set of base filters) does not change significantly in the tuning interval of interest for image acquisition.
Zaraga
Federico
F
Electronics and Information Department, Politecnico di Milano, via Ponzio 34/5, I-20133 Milano, Italy.
Langfelder
Giacomo
G