Optical recording medium
AssigneeSony Corporation
InventorsTamotsu Yamagami, Yoichiro Sako
Life of this patent
Estimating the term…
Abstract
An optical storage medium provided with both a read-write area in which read-write data can be rewritably stored and a read-only area in which read-write data is previously stored in an unerasable manner. In the read-write area, a guide track is previously formed for tracking control, and read-write data is rewritably stored, for example photomagnetically, along the guide track. In the read-only area, data is stored along a read-only track that is offset over a portion of its length in a direction lateral to the track direction to represent the read-only data. This read-only data may be reproduced by detecting the laser light radiated from an optical pickup and reflected by the medium by a two-segment photodetector.
Claims14
An optical medium for storing a read-write information signal and a read-only information signal that can be read by the same optical means, the medium comprising:
- a first area including a means for rewritably storing the read-write information signal, the means including an unmodulated, pre-formed track;
- and
- a second area, radially separated from the first area, the second area including a read-only track along which the read-only information signal is stored, the read-only information signal being stored in a plurality of frames, each frame including a frame sync signal, the read-only track having a track direction and a length in the track direction, the read-only track:
- being in a nominal position in a direction lateral to the track direction over first portions of its length, and being in an offset position, offset from the nominal position in a direction lateral to the track direction, over second portions of its length, to represent the read-only information signal, and
- being in the offset position over a second portion of its length equal in length to a predetermined length to provide the frame sync signal,
- the read-only information signal, when read from the read-only track, generating a read-only signal having a frequency, the read-only information signal being stored on the read-only track such that the frequency of the read-only signal is sufficiently higher than the frequency of tracking error signals produced when the read-only information signal is read from the read-only track.
An optical medium for storing a read-write information signal and a read-only information signal, the read-write information signal and the read-only information signal each comprising a plurality of bits, each bit being in one of a first state and a second state, the read-write information signal and the read-only information signal being read from the medium by the same optical means, the medium comprising:
- a first area including a means for rewritably storing the read-write information signal, the means including an unmodulated, pre-formed track;
- and
- a second area, radially separated from the first area, the second area including a read-only track along which the read-only information signal is stored, the read-only track having a track direction, the read-only track being in a nominal position over a first portion of its length to represent each bit of the read-only information signal in the first state, and the read-only track being in an offset position, offset from the nominal position in a direction lateral to the track direction, over a second portion of its length, to represent each bit of the read-only information signal in the second state.
Dependencies are inferred from the claim text.