System for reproducing pulse time modulated waveforms stored along a diffractive track

Claim 1

A system for reproducing from a recorded track having an axis, a pulse time modulated waveform, comprising: a record containing said recorded track and having at least one reference surface, said recorded track being formed from non-contiguous surface irregularities; uniform upward and downward facing media abutting on said reference surface for forming a modulating structure; the edges of said surface irregularities having closed contours in said reference surface, the width of said closed contours measured transversely of said axis being substantially constant and not in excess of two microns; the non-uniform length and spacing of said closed contours along said track being at least equal to said width; said surface irregularities forming in said reference surface a set of adjacent track portions; said adjacent track portions being flanked by clearance bands consisting of smooth portions of said reference surface; a reproducing device arranged for optically reading out said modulating structure; said reproducing device including illumination means for projecting a spot of radiant energy converging onto said phase modulating structure, said spot substantially occupying the width of any one of said track portions, light emerging from said track portion having a spatial distribution representing an amount of track misregistration between said spot and track, photoelectric detection means arranged for partially collecting the modulated radiant energy emerging from the portion of said modulating structure illuminated by said spot, and detecting an amount and direction of track misregistration from said spatial distribution and positional control means for causing said spot to displace with respect to the read-out track to compensate for any misregistration of the spot and track; said photoelectric detection means comprising at least one photodetector assembly for sensing the spatial distribution of said modulated radiant energy, said photodetector assembly being positioned in a detection plane.

Claim 2

A system for reproducing from a recorded track having an axis, a pulse time modulated waveform, comprising: a record containing said recorded track and having at least one reference surface, said recorded track being formed from non-contiguous surface irregularities; uniform upward and downward facing media abutting on said reference surface for forming a modulating structure; the edges of said surface irregularities having closed contours in said reference surface, the width of said closed contours measured transversely of said axis being substantially constant and not in excess of two microns; the non-uniform length and spacing of said closed contours along said track being at least equal to said width; said surface irregularities forming in said reference surface a set of adjacent track portions; said adjacent track portions being flanked by clearance bands consisting of smooth portions of said reference surface; a reproducing device arranged for optically reading out said modulating structure; said reproducing device including illumination means for projecting a spot of radiant energy converging onto said phase modulating structure, said spot substantially occupying the width of any one of said track portions, light emerging from said track portion having a spatial distribution representing an amount of track misregistration between said spot and track, photoelectric detection means arranged for partially collecting the modulated radiant energy emerging from the portion of said modulating structure illuminated by said spot, and detecting an amount and direction of track misregistration from said spatial distribution and positional control means for causing said spot to displace with respect to the read-out track to compensate for any misregistration of the spot and track; said photoelectric detection means comprising at least one photodetector assembly for sensing the spatial distribution of said modulated radiant energy, said photodetector assembly being positioned in a detection plane.