20
Experiments
Introduction
Classification
Time-multiplexing
Spatial codification
Direct codification
Spatial codification:
De Bruijn sequences (I)
•  A De Bruijn sequence (or pseudorrandom sequence) of order m over an alphabet of n symbols is a circular string of length nm that contains every substring of length m exactly once (in this case the windows are unidimensional).
1000010111101001
•
 m=4  (window size)
 n=2 (alphabet symbols)
•
• Formulation:
Given P={1,2,...,p} set of colours.                      
• We want to determine S={s1,s2,...sn} sequence of coloured slits.
Node: {ijk} Π                                                         
Number of nodes: p3 nodes.
Transition {ijk} Ù {rst} Þ j = r, k = s
• The problem is reduced to obtain the path which visits all the nodes of the graph only once (a simple variation of the Salesman’s problem).
–Backtracking based solution.
–Deterministic and optimally solved by Griffin.
 m = 3  (window size)
 n = p (alphabet symbols)
Conclusions