Detection system for spatially-distributed set of radiation beams

Abstract

Sampling of each bit position at its center is assured, despite random variations from one code to another in both spatial displacement of the radiation beams with respect to the contiguous sensing elements of an array and the width of the radiation beams, with only the center-to-center spacing between adjacent bit positions remaining predetermined and invariant. This is accomplished by (1) employing a sync bit as the first bit of the code, (2) loading each sensing element into a corresponding stage of a shift register, (3) shifting out the shift register at a predetermined clock rate, (4) applying no counting input to a counter until the detection of a read out sync bit from the shift register and then applying a counting input to the counter at one-half the clock rate while the sync bit is being read out and thereafter at the clock rate itself. Counts registered in the counter control a sampling gate for passing each successive bit of the code read out from the shift register at its center particularly suitable for codes obtained from reconstructed embossed plastic Fraunhofer holograms that have been dynamically pressed.