Page 374 - Introduction to Information Optics

7.1. Basic Architectures

CCD array
/,, SIM 3
detector

Microcomputer
Fig. 7.5. A hybrid optical VLC.

be used to make decisions. Even the simplest type of decision making is based
on the comparison of an output with a stored value. Such an operation cannot
be performed optically without the intervention of electronics.
Many deficiencies of optical systems happen to be strong points in their
electronic counterparts. For instance, accuracy, controllability, and program-
mability are some obvious traits of digital computers. Thus, the idea of
combining an optical system with its electronic counterpart is rather natural
as a means of applying the rapid processing speed and parallelism of optics to
a wider range of applications.
We will show a few commonly used hybrid-optical architectures, as applied
to pattern recognition. F'or convenient discussion, these architectures are
repeated in Figs. 7.5, 7.6, and 7.7, respectively. In view of these figures, we see
that optical- electronic interfacing devices such as SLMs and CCD cameras are
used. Remember, the operations of VLC and JTC are basically the same. There
are, however, some major distinctions between them. For example, the spatial
filter synthesis (Fourier hologram) in the VLC is independent of the input scene,

LCTV
CCD,

Microcomputer

Fig. 7.6. A hybrid JTC.