Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1997-03-26
2001-04-17
Young, W. R. (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044370, C369S053200
Reexamination Certificate
active
06219316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a compatible recording or reproduction device with three-point scanning for recording media having different track spacings.
2. Related Art
Optical and magnetic recording media having different track spacings are generally known. Recording media having a relatively small track spacing mainly belong to a more recent generation and, as a rule, permit the recording or the reproduction of larger volumes of information or data. In order also to be able to continue using recording media of an earlier generation, having a relatively large track spacing, in recording or reproduction devices of a more recent generation for recording media having a relatively small track spacing, these recording or reproduction devices must be compatible with the different recording media. It is desirable, for example, to be able to play CDs, too, in a recording or reproduction device for optical recording media having a high storage density, a so-called SD, which is also referred to as a Super Density disk. Compared with the CD, the SD has a higher storage density, which is achieved, inter alia, by a smaller track spacing. In order to be able to read both an SD and a CD in a recording or reproduction device, a compatible tracking system is therefore necessary. On account of the higher track density or the smaller track spacing in the case of the SD, the tracking of the SD with a generally known three-beam system is more critical than in the case of a CD. In a compatible recording or reproduction device which permits the playback both of a CD and of an SD using the same optical scanning system, it is therefore necessary to set the three-beam tracking in a manner such that it is optimal for the SD. This means that the beams provided for tracking, which are also referred to as the auxiliary beams E and F of the optical system, have to be adjusted in such a way that they are tangent to the SD track on both sides. As a result, the tracking on a CD using the three-beam system becomes more difficult since the auxiliary beams are imaged virtually completely on the CD track, which has a larger width. The amplitude and the phase spacing for tracking become smaller, with the result that the reproduction of a disk having high eccentricity cannot be ensured.
From EP 129 760, it is already known to match the spacing between the beams provided for tracking and the main light spot to the corresponding requirements by rotating the grating with which the auxiliary beams IF are produced. However, this necessitates control means, which require an additional outlay.
SUMMARY OF THE INVENTION
The object of the invention, therefore, is to provide a compatible recording or reproduction device which makes it possible, even without changing the setting of the three-point scanning system, to use recording media having different track spacings in this device.
This object is achieved according to the invention in accordance with the main claims. Advantageous developments are specified in the subclaims.
According to the invention, the three-point scanning system is set in such a way that the scanning centre points have a lateral spacing from one another which is approximately both an integer multiple of one quarter of the track spacings and a common multiple of the different track spacings. Accordingly, the spacing of the scanning centre points for a compatible recording and reproduction device for SD and CD is selected in such a way that it amounts to approximately {fraction (7/4)} of the track spacing of the recording medium having the smaller track spacing and approximately ¾ of the track spacing of the recording medium having the larger track spacing. The recording medium having the smaller track spacing is the SD and the recording medium having the larger track spacing is the CD. However, the application of the invention is not restricted to recording media having a spiral data or information track. The data or information tracks of the recording medium may also be parallel tracks. Furthermore, the invention is not restricted to optical recording media such as the SD and CD, but rather can equally be used for recording media in connection with multi-track recording and different track spacings.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in more detail below with reference to drawings, in which:
FIG. 1
shows recording media having different track spacings and three-point scanning,
FIG. 2
shows recording media having different track spacings and scanning point arrangement of a compatible recording or reproduction device,
FIG. 3
shows a diagram of the auxiliary beam intensity, and
FIG. 4
shows the structure of a compatible recording or reproduction device.
REFERENCES:
patent: 4449215 (1984-05-01), Reno
patent: 4686663 (1987-08-01), Kuhn
patent: 4737946 (1988-04-01), Yamashita et al.
patent: 5235583 (1993-08-01), Jongenelis et al.
patent: 5708636 (1998-01-01), Takahashi et al.
patent: 5815473 (1998-09-01), Takahashi et al.
patent: 5917790 (1999-06-01), Ohta et al.
patent: 3323007 (1984-06-01), None
Buechler Christian
Dang Lieu-Kim
Schroeder Heinz-Joerg
Deutsche Thomson-Brandt GmbH
Kiel Paul P.
Tripoli Joseph S.
Young W. R.
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