Patent ID: 8355581

Claim:
A system for detecting the contour of an object situated on a surface, the system comprising: (a) an image acquisition assembly, wherein there is relative motion between said image acquisition assembly and said object, said image acquisition assembly comprising: (1) a line detector, operable for scanning said surface line by line by virtue of said relative motion, wherein each line is scanned during a scan cycle, said line being transverse to the direction of said relative motion; and (2) a light source, operable for emitting light toward said line detector during active periods between idle periods, such that during each of said active periods said light is emitted for at least one cycle synchronized with said scan cycle, allowing said line detector to acquire a first group of at least one lit scan line, and during each of said idle periods lasting for at least another cycle synchronized with said scan cycle, no light is emitted, allowing said line detector to acquire a second group of at least one unlit scan line, wherein said object passes between said line detector and said light source by virtue of said relative motion, and (b) a processor coupled with said image acquisition assembly, said processor receiving and analyzing scan lines acquired by said line detector, wherein for each of said first group of at least one lit scan line and a successive one of said second group of at least one unlit scan line, said processor identifies a token pattern consisting of a lit segment of said first group adjoining an unlit segment of said second group, said processor searches along said first group and said successive second group for locations where said token pattern ends or reappears, thereby defining edges of said object, and combining the collection of said defined edges to produce a contour of said object.