Data recording and/or reproducing apparatus, and disc-shaped recording medium

Abstract

A data recording and/or reproducing apparatus is disclosed which scans a head over a disc on which a servo pattern for moving the head to a predetermined position is recorded in an arc forming a part of a concentric circle. The apparatus comprises a track No. detector and fine signal detector, for detection of the servo pattern, a circumferential position detector to detect a circumferential position on the disc, an offset calculator to calculate an offset of a current position on the disc from the detected circumferential position, and a positional difference calculator. The calculated offset of the current position is added to the positioning signal to control the head scanning orbit on the disc to be spiral.

What is claimed is:  
     
         1 . A data recording and/or reproducing apparatus in which a signal recording and/or reproducing head is scanned over a disc-shaped recording medium on which a positioning signal to move the signal recording and/or reproducing head to a predetermined position is recorded along an arc of a concentric circle, comprising: 
 means for detecting a positioning signal recorded along the arc;    means for detecting a circumferential position on the disc-shaped recording medium; and    means for calculating an amount of offset from a signal indicative of the detected circumferential position;    the calculated offset amount being added to the positioning signal to control the head for a scan along a spiral scanning orbit.    
     
     
         2 . The apparatus as set forth in  claim 1 , wherein during idling with no data recording or reproduction, the head is controlled to scan along a concentric orbit over the disc-shaped recording medium.  
     
     
         3 . The apparatus as set forth in  claim 2 , further comprising a means for holding the amount of offset, the offset amount held by the holding means being added to the positioning signal to control the head for a scan along a concentric orbit over the disc-shaped recording medium during idling with no data recording or reproduction.  
     
     
         4 . The apparatus as set forth in  claim 2 , further comprising a means for selecting, depending upon the type of a data to be recorded, whether the head is to be controlled to scan along a spiral or concentric orbit over the disc-shaped recording medium.  
     
     
         5 . The apparatus as set forth in  claim 4 , wherein the head is controlled to scan along a spiral orbit over one side of the disc-shaped recording medium adapted to record data on either side thereof, and along an inverted spiral orbit over the other side of the recording medium.  
     
     
         6 . The apparatus as set forth in  claim 2 , wherein the arc forming a part of the concentric circle, along which the positioning signal is recorded, has a radius variable from one circumferential position to another.  
     
     
         7 . The apparatus as set forth in  claim 1 , further comprising a means for selecting, depending upon the type of a data to be recorded, whether the head is to be controlled for a scan along a spiral or concentric orbit over the disc-shaped recording medium.  
     
     
         8 . The apparatus as set forth in  claim 1 , wherein the head is controlled to scan along a spiral orbit over one side of the disc-shaped recording medium adapted to record data on either side thereof, and along an inverted spiral orbit over the other side of the recording medium.  
     
     
         9 . The apparatus as set forth in  claim 1 , wherein the arc forming a part of the concentric circle, along which the positioning signal is recorded, has a radius variable from one circumferential position to another.  
     
     
         10 . The apparatus as set forth in  claim 1 , wherein the disc-shaped recording medium is rotated at a constant angular velocity.  
     
     
         11 . A data recording and/or reproducing apparatus in which a signal recording and/or reproducing head is scanned over a disc-shaped recording medium having recorded along an arm of a concentric circle having a radius variable from one circumferential position to another a track address information signal under which the head is moved to a predetermined radial position of the disc-shaped recording medium, comprising: 
 means for detecting, based on an information read by the head, the track address information signal recorded along the circular arc of the concentric circle;    means for detecting, based on the head-read information, a circumferential position of the head on the disc-shaped recording medium;    means for detecting, based on the signal indicative of the circumferential position on the disc-shaped recording medium, an amount of offset with respect to the track address information signal; and    means for controlling, based on the track address information signal and offset amount, the head for a scan along a spiral orbit over the disc-shaped recording medium.    
     
     
         12 . The apparatus as set forth in  claim 11 , wherein the head is controlled to scan along a concentric orbit over the disc-shaped recording medium during idling with no data recording or reproduction.  
     
     
         13 . The apparatus as set forth in  claim 12 , further comprising a means for holding the amount of offset, the offset amount held by the holding means being added to the positioning signal to control the head for a scan along a concentric orbit over the disc-shaped recording medium during idling with no data recording or reproduction.  
     
     
         14 . The apparatus as set forth in  claim 12 , further comprising a means for selecting, depending upon the type of a data to be recorded, whether the head is to be controlled to scan along a spiral or concentric orbit over the disc-shaped recording medium.  
     
     
         15 . A disc-shaped recording medium having recorded along an arc forming a part of a concentric circle thereon a positioning signal to move a signal recording and/or reproducing head to a predetermined position, 
 the arc along which the positioning signal is recorded having a-radius variable from one circumferential position to another.    
     
     
         16 . The disc-shaped recording medium as set forth in  claim 15 , wherein the data track along which data is recorded is formed spirally.  
     
     
         17 . The disc-shaped recording medium as set forth in  claim 15 , wherein data can be recorded on either side thereof and a data track is formed in a spiral form on one of the disc sides and in an inverted spiral form on the other side.  
     
     
         18 . The disc-shaped recording medium as set forth in  claim 15 , having formed thereon servo zones in which at least the position information signal is recorded, and data zones into and/or from which data is recorded and/or reproduced.  
     
     
         19 . The disc-shaped recording medium as set forth in  claim 18 , wherein the servo zone has recorded therein a signal indicative of a circumferential reference position on the medium.