Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Patent
1994-11-01
1997-02-04
Nelms, David C.
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
369100, 369116, G11B 1110, G11B 700
Patent
active
056006128
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a magnetooptic recording method, a magnetooptic recording medium and a magnetooptic recording apparatus.
BACKGROUND ART
While magnetooptic recording media capable of storing information with high densities are expected to come into wide use as large-capacity external memories, of these media an optical disc is attracting notice as an external memory for computers on the ground that it can effect the playback at a high speed. While there have been proposed various kinds of magnetooptic recording media which are different information storing method and size, in accordance with the ISO standards, the magnetooptic recording medium of the write-once type capable of writing information only once and the magnetooptic type capable of erasing the information have been standardized with respect to the size of 5.25 inches in diameter, whereas the ROM type and the magnetooptic type used exclusively for playback purposes as well as the partial ROM type featuring the coexistence of the magnetooptic type and the ROM type have been standardized with respect to the size of 3.5 inches in diameter, and these types are expected to be put on a still wider market in the future.
Also, recently the application of the optical disc has also been started in the field of digital audio. For instance, players have been put on the market in which the write-once type optical disc or magnetooptic disc is used as a master source in a digital multiple track recording of 24 to 48 tracks. In addition to these products adapted for use by the specialists, there has been the advant of products adapted for use by the general consumers, such as, a CD-R (a compact disc of the write-once type) and an MD (miniature disc) and their future trend attracts notice.
In these optical discs, the guides for orderly arranging the information marks by the laser beam from an optical pick-up of a recording and playback apparatus, i.e., the guides for tracking purposes are formed in the form of recessed or raised grooves spirally from the inner periphery toward the outer periphery of the disc. These grooves are called as guide grooves.
Explaining the guide grooves in greater detail, as defined according to the ISO standards, those portions constituting the recesser or the far portions as looked from the optical pick-up are called as lands and the other portions constituting the raised portions or the near portions as looked from the pick-up are called as grooves. Information is recorded on either the lands or the grooves. When recorded on the lands, it is called as a land recording system, whereas when recorded on the grooves, it is called as a groove recording system. The paths for recording the information are called as tracks, and the spacing between the center of one track and the center of the adjacent track is called as a track pitch.
Generally, each of the tracks is further divided into a plurality of portions which are called as sectors and each of the sectors is composed of an address part, a flag part, a data part and a buffer part. The address part indicates a physical address on the disc, the flag part indicates whether the sector is a recorded sector, defective sector, deleted sector or the like, the data part is a region for recording the desired information and the buffer part is provided as a buffer region for preventing the leading portion of the next sector from being recorded away even if a variation is caused in the rotation of the disc. The mark size of the data part is relatively small so as to record the information with a density which is as high as possible. Therefore, during recording it is necessary to effect the recording in synchronism with a certain frequency used as a reference and during playback it is necessary to effect the discrimination timing of playback signals in synchronism with the reference frequency; otherwise, there is the danger of failing to play back the desired recorded information due to any variations of the playback timing. The signals of this reference frequenc
REFERENCES:
patent: 5233596 (1993-08-01), Tani
patent: 5297128 (1994-03-01), Yamaguchi
patent: 5323374 (1994-06-01), Arai
patent: 5329512 (1994-07-01), Fukimoto
Kurita Shinichi
Miyata Kazutomo
Saito Jun
Yamanaka Yoshihiro
Mai Son
Nelms David C.
Nikon Corporation
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