Page 395 - Introduction to Information Optics

380 7. Pattern Recognition with Optics

CCD and then sent back to the LCTV panel for correlation operation. Figure
7.25b shows the output distribution, in which two distinctive blue spots can
easily be detected.

7.4. TARGET TRACKING

One interesting feature of using a hybrid-optical JTC is adaptivity; for
example, the reference scene and the dynamic input scene can be continuously
updated.

7.4.1. AUTONOMOUS TRACKING

By continually updating two sequential input scenes which display side-by-
side at the input domain of a JTC, it is possible to track a moving target. Let
us consider the two sequential scenes that are displayed with a video frame
grabber on the input SLM, with the previous and the current frames positioned
in the upper and lower half of the SLM. This is represented mathematically by

x
f, - 1 1 * - <. i,y-y t-i-j) and ft
\ "/ \
(7.22)

where 2a is the height of the display unit, t and t — 1 represent the current and
previous time frames, and (dx, 3y) is the relative translation of the target. The
complex light field at the Fourier domain can be shown to be

T(u, v) = F t^ !(«, v) exp < —i2n wx ( _, + v y t_ j ,(u, v)

• exp •{ —i2n \ u(x t_ ^ + dx) + v { y r _ l + Sy — - (7.23)

If the detected JTPS is sent back to the SLM for the correlation operation, the
output light distribution can be written as

C(x, y) = R ttt(x, y)+R t- ltt- ^x, y) + /?,.,_ t (x - <5x, y + 5y - a)

+ /?,_ lif (x — ^x, y — dy + a),