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Rotary recording medium having a guide track and recording and reproducing apparatus therefor
| Details |
Inventors: Yamaguchi, Hirohisa; Usami, Horoshi; Nagai, Tadao; Mashimo, Akira;
Assignee: TEAC Corporation (Tokyo, JP)
Primary Examiner: Faber; Alan
Assistant Examiner:
Attorney, Agent or Firm: Ladas & Parry
A disc comprises a recording surface which is divided into a plurality of equiangular sectoral regions and a guide track formed on the recording surface. Each track turn of the guide track is constituted by a row of pits formed in every other equiangular sectoral regions, and the pit is only formed in one of two mutually adjacent track turns of the guide track in each equiangular sectoral region so that the pits are formed in every other track turns in a radial direction of the disc in each equiangular sectoral region. An apparatus for playing the disc comprises a circuit for producing a switching pulse signal having a period dependent on a period of the pits of the guide track based on signals which are reproduced from the two mutually adjacent track turns by sub light beams, a circuit for alternately inverting a polarity of signals which are reproduced from the two mutually adjacent track turns by a main light beam for every one half period of the switching pulse signal and for generating a tracking error signal, a tracking device, and a device for recording and reproducing an information signal on and from an intermediate part of the disc between the two mutually adjacent track turns. |
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DETAILED DESCRIPTION Accordingly, it is a general object of the present invention to provide a novel and useful disc having a guide track and a recording and reproducing apparatus for playing the disc, in which the problems described heretofore are eliminated.
Another and more specific object of the present invention is to provide a disc comprising a recording surface which is divided into a plurality of equiangular sectoral regions and a guide track formed on the recording surface, where each track turn of the guide track is constituted by a row of pits formed in every other equiangular sectoral regions, and the pit is only formed in one of two mutually adjacent track turns of the guide track in each equiangular sectoral region so that the pits are formed in every other track turns in a radial direction of the disc in each equiangular sectoral region.
A track turn of an information signal recording track can be formed in a region between the two mutually adjacent track turns of the guide track.
According to the disc of the present invention, it is possible to obtain a tracking error signal from signals reproduced from the guide track by a main light beam.
Hence, although the conventional disc having two continuous spiral guide tracks (grooves) located on both sides of an information signal recording track suffers a problem in that a trailing sub light beam is affected by the pits of the information signal recorded by a main light beam, it is possible to eliminate such a problem according to the present invention.
Still another object of the present invention is to provide a disc in which the guide track has a depth of 1/2 the wavelength of the main light beam for recording and reproducing the information signal.
According to the disc of the present invention, it is possible to prevent diffraction in a reflected light from the guide track.
For this reason, a tracking error signal will not be affected by diffracted light even when the main light beam traverses the guide track.
As a result, the astigmatic focusing method can be used as a method of detecting a focal error, and the construction of an optical system in a recording and reproducing apparatus can be simplified compared to that of the conventional recording and reproducing apparatus which is designed to play the conventional disc having a single continuous spiral guide track
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