Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1992-01-27
1995-05-09
Dzierezynski, P. M.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369 59, G11B 700
Patent
active
054146895
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optical information processing apparatus, and more particularly to a large-capacity high-speed optical disk device. The present invention further relates to a track/sector format suitable for such an optical disk device.
BACKGROUND ART
As for the prior art, one can refer to, for example, HITACHI HYORON, Vol. 65, No. 10 (October 1983), pp. 23-28. In a device disclosed by this reference, a disk is rotated at a constant angular velocity and there is used, as a data recording system, a pit position recording system in which "1" of code information after modification corresponds to the center of a pit. Also, the device employs a CAV (constant angular velocity) system in which the recording bit rate is constant over all circumferences of the disk. Accordingly, a bit length on the disk is different between inner and outer circumferences. For example, if the radius of the outermost circumference is twice as long as that of the innermost circumference, the bit length on the outermost circumference becomes twice as long as that on the innermost circumference. In the CAV system, the characteristic of a recording/reproducing system may be constant since the recording bit rate is the same over all circumferences. Also, the number of sectors per one track may be the same irrespective of the inner and outer circumferences of the disk.
In the case where it is desired to obtain a higher density than that in the CAV system, there can be considered systems as follows. A recording system as means for improving the linear recording density includes a pit edge recording system in which "1" of code information corresponds to the edge portion of an elongated hole or pit. In this system, it is possible to detect an edge position from a reproduced waveform even in the case where the linear recording density is made high as compared with that in the pit position recording system even if the characteristic of an optical system is the same. Further, if the pit edge recording system is used in combination with an MCAV (modified CAV) system in which the linear recording density is substantially constant over all circumferences of the disk and the rotating speed of the disk is made constant, it is possible not only to improve the linear recording density by virtue of the pit edge recording but also to attain a large capacity without bringing about the lowering of an access speed. When the radius of the outermost circumference is twice as long as that of the innermost circumference, the use of the MCAV system makes it possible to improve the capacity up to about 1.5 times as large as that in the CAV system. In order to use the pit edge recording system and the MCAV system in combination, there is required a track/sector format which is different from the conventional format used in the combination of the pit position recording system and the CAV system.
DISCLOSURE OF INVENTION
An object of the present invention is to provide an information recording/reproducing apparatus which is capable of attaining a high recording density and a high transfer rate by the combined use of a pit edge recording system and an MCAV recording system and to provide a format which is suitable for such an apparatus. According to the present invention, a capacity of at least 3.0 GB per one surface and a transfer rate of at least 1 MB/sec can be realized for a disk-like recording medium having a diameter of about 300 mm.
The pit edge recording system makes it possible to improve the recording bit density as compared with the pit position recording system even if an optical resolution is the same. FIG. 2 shows a comparison of the pit position recording system which is the conventional recording system and the pit edge recording system which is used in the present invention.
In the pit position recording system, if the interval between pits is shortened in order to improve the recording density, the level of a reproduced waveform 4 at a portion thereof including no pit is deteriorated due to an interference b
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Arai Shinichi
Isaka Kazuo
Kawamura Satoshi
Maeda Takeshi
Mizokami Takuya
Dzierezynski P. M.
Hitachi , Ltd.
Wong Don
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