Page 502 - Introduction to Information Optics

9.2. Parallel Optical Logic and Architectures 48:

B

z*ro

IMMM^^^M IMMM| Mwflk* IMWWMMIM*

Fig. 9.10. (a) Dual-rail spatial encoding for 1 and 0, (b) Symbolic substitution rules for binary
half-addition.

realized in two stages: recognition and substitution. In the recognition stage,
all the occurrences of the search pattern in the 2-D input plane are marked in
parallel. In the substitution stage, the scribe pattern is substituted in all the
locations where the search pattern is found. In its operation, the recognition
usually comprises the procedures of replicating, shifting, superimposing of the
input pattern and thresholding [64]. The substitution phase is functionally
similar to the recognition phase except for thresholding. Symbolic substitution
can be performed by coherent correlator architectures, shown in Fig. 9.11. The
first correlator (P1-P3) performs the recognition phase and the second

Ll L2 L3 L4
A P2 . A P3 , A P4 s\ A
/-

/
/ }
\J / V U V
Recognition Threshold Substitution „
Input „., ™ r- 1 Output
r
Filter Device Filter
Correlator 1 (Recognition) ( l Correlator 2 (Substitution) l
Fig. 9.11. Basic cascaded correlator architecture for symbolic substitution [70].