4. Image acquisition systems

Since the development of computer systems, images are no longer exploited solely by observing their projection on a screen, but also by automatically processing some of the data they contain. These data consist of light intensity levels as a function of two spatial coordinates I(x, y), for a monochrome image and several intensity values I ₁ (x, y), I ₂ (x, y), I ₃ (x, y), ..., at each point x, y for a color image. When images are recorded on film, automatic reading systems, called acquisition systems, are therefore required to acquire these values.

The film recording consists of local variations in transparency. An image, often enlarged, of this optical object illuminated by transmission is formed by a lens on a photodetector....