Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Patent
1982-08-16
1985-10-01
Faber, Alan
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
369 54, 369 58, 369111, G11B 700
Patent
active
045450447
ABSTRACT:
In an optical disc having a file region and a directory region for carrying various pieces of information or data, one or more designated information can be erased by irradiating a laser light beam on a corresponding region in the file region where the light beam is modulated by a superposing writing signal which may be a d.c. or a predetermined a.c. signal. When it is intended to renew the information, designated information is first read out and stored in an external memory prior to performing superposing writing. Meanwhile, the data is renewed and is then written on an unused region in the file region. The directory of the renewed data region is also written so that the renewed information will be read out by searching the new directory. In another embodiment of the invention, the information in the file region is not erased to renew the same, but its directory is erased by superposing writing. A new directory for a renewed information, which is written in unused region in the same manner as the above, is written so that the renewed information can be read out by using the new directory. When reproducing, an envelope of the reproduced signal is detected to see whether information can be read out or not. Thus, erased information is skipped to reproduce only unerased information.
REFERENCES:
patent: 4051329 (1977-09-01), Blondet
patent: 4125860 (1978-11-01), Ishii
patent: 4241240 (1980-12-01), Shigematsu
patent: 4321635 (1982-03-01), Tsuyuguchi
Koishi Kenji
Ohara Shunji
Satoh Isao
Yoshida Tomio
Faber Alan
Matsushita Electric Industrial Company Limited
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