Data disc optical reader containing a device for automatic data access
AssigneeThomson-Brandt
InventorsRene Romeas, Michel Thomas
Life of this patent
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Abstract
The invention concerns the reading by optical means of data recorded along a track on a disc; an address code, which increases one unit at each step, is recorded on the disc at the same time as the data. The optical reader contains a device for the fast movement of the reading head in a direction radial to the disc, a device for counting the number of track grooves thus crossed, a device for automatic access to some given data which contains a device for detecting addresses recorded and a programmed control circuit which triggers fast movement or a step by step movement of the reading head depending on whether the reading head is far from the track groove whose address has been recorded or is near to this track groove.
Claims21
An optical reader for data carrier disc, said data being recorded along a track formed of concentric grooves, said track containing a succession of alternate elements optically detectable, adresses for said grooves formed by coded numbers being recorded at the same time as said data on each corresponding groove, said optical reader comprising a radiating source, a reading head intended to receive the radiation and to focus it on said track, a rotating device causing said disc to rotate, a detecting device for detecting the radiation coming from said track and supplying an electrical signal, a demodulation device, for demodulation said electrical signal, having an output delivering a demodulated signal and a device for automatic access to the data recorded on said disc, said automatic access device comprising an address detection device intended to supply a detected address formed by a coded number, a rough search device to position said reading head from an initial groove to a predetermined distance from the track groove required, said required groove being identified by the recording of its address a.sub.x in a memory logic circuit, and a fine search device intended to make the said recorded address a.sub.x and the detected coincide.
Dependencies are inferred from the claim text.