Demosaicking is the interpolation of missed colour samples in a colour filter array (CFA). The term demosaicking has its roots in the word "mosaic" which, in turn explains the structure of a colour filter array typically used in a digital camera. The detectors (cells) of blue, red and green colours or their combinations are spread regularly (mosaicked) on the electronic sensor chip (CMOS, CCD or other technology). The resulting mosaic of colour samples is passed through an interpolation procedure to determine the intensities of colours that are not sampled by the array. The pattern of the mosaic is important as most interpolation methods make use of a priori knowledge of the configuration for a more precise image restoration. The most popular is currently the Bayer CFA. It has twice as many green detectors than blue or red, however there are alternative sensors which are based on cyan, magenta, yellow and green colours.