chapter  5
Photodetectors
Pages 82

In both the eye (see Section 4.2.1) and a camera, the light coming

from a source is focused with a lens onto a detection plane. In

the former case, the detection plane is the retina where cells,

which are sensitive to changes in light intensity, encode the image

and send it to the brain, while in the latter case, the detection

plane contains either a photographic ﬁlm (see Section 1.4.2) or an

electronic detector, inwhich light intensity is converted to an electric

signal. In the electronic camera, the photodetectors are required to

detect light, which put out an electrical signal whose amplitude is

proportional to the photons striking the surface. Such cameras can

be either analog or digital. In the former case, the detectors coupled

acquisition and display together and provide higher resolution but

with limited dynamic range and ﬁxed detector contrast, while in

the latter case, the detectors have separated acquisition and display

system providing higher dynamic range and noise-limited contrast

but with lower resolution.