The influence of Bayer filters on the quality of photogrammetric measurement

Bayer colour filter arrays (CFA) are commonly used to obtain digital colour imagery from a single-chip CCD or CMOS camera. Colour information is captured via a regular array of colour filters placed over the image sensor, and the full colour image is reconstructed in a demosaicing process. Colour imagery derived in such a way is prone to visual artefacts including false colours, poor edge definition and a loss of image and colour sharpness. Such artefacts are suspected of degrading the quality of photogrammetric measurements made from demosaiced images. An approach to demosaicing based on the use of tuneable Gaussian filters is proposed. The new approach is designed to minimise image artefacts and is specifically aimed at improving the quality of photogrammetric measurements made with the demosaiced imagery. Results are given for a specific application of Bayer CFA cameras to underwater stereo length measurement of fish. The results show a reduction in visual artefacts and an improvement in the quality of stereo measurements.