Photoreceptor matrix for optical video playback system

DETAILED DESCRIPTION What is claimed is: 1.
In an optical readout system for scanning a video record with a reading beam of energy to derive information stored in a track on said record, a photoreceptor matrix comprising: four photoreceptors a, b, c and d with (a,b) arranged as a tandem pair along the direction of said track and with (c,d) also arranged as a tandem pair along the direction of the track, said pairs being symmetrically disposed on opposite sides of a reference plane that extends along the direction of said track and is coincident with the axis of said beam and tangent to said track at the point where it is scanned by said beam, with photoreceptors a and c having a leading relationship relative to said reading beam and photoreceptors b and d having a lagging relationship thereto; and first circuit means coupled to all of said photoreceptors for differentially combining the output signals thereof of said photoreceptors to develop a radial error correction signal (a+b) - (c+d) having a polarity and amplitude related to the sense and degree of radial tracking misregistration.
2.
A matrix in accordance with claim 1 which also includes second circuit means also coupled to all four of said photoreceptors for summing their outputs to derive a signal a + b + c + d representing information stored in said record.
3.
A matrix in accordance with claim 2 which further includes third circuit means likewise coupled to all four of said photoreceptors to combine the output signals thereof to develop another output signal (a +c) - (b+d) representing additional information stored in said record.
4.
A matrix in accordance with claim 3 for reading a record in which the stored information represents an angel-velocity-modulated carrier signal, in which the stored information further represents another information signal having a frequency below the band occupied by said modulated carrier signal, in which said second circuit means is selective to frequencies corresponding to said other information signal, and in which said third circuit means derives said modulated carrier signal