A record disk bearing a servo pattern and record disk apparatus comprising such a record disk.

摘要

A servo pattern (70) of detectable marks is so disposed on a record disk (66) that when the disk is rotated past a sensor device (72) for sensing the marks, there is a plurality of nested (e.g. substantially concentric) paths along which the rate of sensing the marks is individual to each path whereby it is possible to define a record track (68) on the disk by reference to a selected one of the paths.
<??>The servo pattern (70) does not interfere with or use any of the recording capacity of the record medium (74) on the disk. The servo pattern is sensed by a sensor (72) different from any transducer (12) used to access the record medium. The record medium can be a conventional magnetic layer and the servo pattern can be formed of optically reflective or non-reflective spots overlying or underlying the magnetic record medium.
<??>The sensor (72) is mounted for common radial movement with the transducer (12). As the record disk spins, the sensor produces an output signal from which is derived a mark sensing rate signal. Each record track (68) is defined by an individual mark sensing rate. A servo control system positions the transducer (12) so that the mark sensing rate is maintained at the rate defining a desired record track (68).