Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Patent
1996-09-20
1998-09-22
Dinh, Tan
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
3692752, 3692753, G11B 724
Patent
active
058125191
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The invention relates to a ROM-RAM disk and a method which makes it possible to read the ROM area and to write to the RAM area at the same time, as well as to read ROM and RAM simultaneously using a scanning unit.
A ROM-RAM disk is an optical recording medium which has memory areas which can only be read and memory areas which can both be read and written to. Memories which can only be read are called ROM or read only memory, and memories which can both be read and written to are called RAM or random access memory. A ROM is implemented on optical information media by means of so-called pits which form a spiral data track in the CD. While, in the case of the CD, a light-reflecting aluminium layer has depressions, so-called pits, which represent the data stored on the disk, the MOD has a magnetic layer in which data can be recorded and from which data can be read by means of different magnetization. Information and bits are likewise stored on a spiral data track in domains having a different magnetization direction. In this case, in contrast to an analogue record disc, the data track is read from the inside to the outside at a constant linear velocity, the so-called CLV.
DE-OS 37 32 875 discloses a recording medium which is in the form of a disk and represents a combination of an optical disk and a magneto-optical disk--a so-called ROM-RAM disk. On this recording medium, data are stored both in pits and in domains in a spiral data track. Since the pits and magnetic domains are arranged one above the other, the memory capacity or the memory volume of the ROM-RAM disk is theoretically equal to the sum of the memory volumes.
In order to be able to store and read the information which is stored on an optical information medium in pits or magnetic domains or in a RAM area or a ROM area, a minimum length of memory structures is required, which length is dependent on the wavelength of the scanning laser beam and the memory principle used. In the case of a laser beam wavelength of 780 nm, which is frequently used for scanning optical information media, the minimum length of a memory structure in the RAM area or in the ROM area is approximately 0.8 .mu.m, in order to implement a maximum memory volume. In order to reproduce information which is stored in the RAM area on a ROM-RAM disk, a minimum length of the recording structure for the RAM information of more than 1.38 .mu.m is required in order to be able to select and read the RAM information from the signal mixture, which consists of ROM information and RAM information. This results in it being necessary to read a ROM area or a RAM area and a ROM-RAM area at a different velocity and in it not being possible simultaneously to read the ROM-RAM area and to read the ROM area and to write to the RAM area at the same time. By increasing the linear velocity CLV, the memory volume of the ROM-RAM disk is necessarily reduced in comparison with the theoretical double memory capacity.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to create a ROM-RAM disk and a method which enable simultaneous reading of ROM and RAM and reading of the ROM area and writing to the RAM area at the same time, as well as a memory volume which is as large as possible.
A ROM-RAM disk is used as the basis, which has ROM and RAM memory areas superimposed in a spiral information track. In order to ensure a memory volume which is as large as possible in the case of an information medium of comparable diameter, despite the longer memory structures and increased linear velocity required to separate the information during reading, either the area of a ROM-RAM disk which has both ROM and RAM memory structures is provided only beyond a diameter beyond which a scanning or writing velocity is reached at a constant rotation speed, which velocity ensures reading and separation of the information stored in ROM and RAM structures, or the entire memory area is provided with a reduced data clock rate for the RAM as well as the ROM-RAM area, which is stored and read using a consta
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Kawamura Akira
Morimoto Yasuaki
Zucker Friedhelm
Deutsche Thomson-Brandt GmbH
Dinh Tan
Tripoli Joseph S.
Wein Frederick A.
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