Optical information recording medium which uses diffraction grat

Details Optical information recording medium which uses diffraction grat Optical information recording medium which uses diffraction grat

1994-04-28

1996-10-29

Dinh, Tan

Dynamic information storage or retrieval

Storage medium structure

Optical track structure

369109, G11B 724, G11B 700

Patent

active

055703380

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an optical information recording medium from which information is optically reproduced and an information reading method for the same and, more particularly, to an optical information recording medium which uses diffraction gratings as information recording elements so that information can be recorded at a very high density and from which a plurality of pieces of information are read at once simultaneously so that information can be read at a higher speed, and an information reading method for the same.


BACKGROUND ART

Generally, optical recording has advantages in that, e.g., a recording medium and a head do not contact each other when compared to magnetic recording, and high-density recording can be performed. Various types of media are known as optical recording media for optical recording, e.g., a read-only medium, a write-once medium, and an erasable programmable medium.
Optical recording media of these types have already been in practical use in various fields in the forms of, e.g., an optical recording disk (e.g., a CD, a CD-ROM, a CD-I, a laser disk, write-once and programmable disks, and a magneto-optical disk) and an optical card (e.g., a ROM card, write-once and programmable cards, and a magneto-optical card).
In a conventional read-only or write-once optical recording disk, a laser beam generated by a light source, e.g., a semiconductor laser, is focused to form a spot having a diameter of 1 to 2 .mu.m on the disk surface, and the surface state of the corresponding portion on the disk surface is detected by utilizing light reflected by the disk surface.
More specifically, when a pit is present, light is randomly reflected to reduce the intensity of the reflected light. When a pit is not present, light is reflected by a mirror surface. Data is read by utilizing a difference (intensity of light) between these two states.
In this case, however, a decrease in spot diameter of the laser light beam is limited to as small as about 1 to 2 .mu.m, and it is impossible to decrease the spot diameter to be extremely smaller than this.
Accordingly, the information amount of the conventional optical recording disk is limited by the fact that one pit on the disk represents one piece of information and by the limited spot diameter of the laser light beam. As a result, information recording at a high density exceeding a certain limit cannot be performed.


DISCLOSURE OF INVENTION

It is the first object of the present invention to provide an optical information recording medium which uses diffraction gratings as information recording elements so that information can be recorded at a very high density and from which a plurality of pieces of information are read at once simultaneously so that information can be read at a higher speed, and an information reading method for the same.
It is the second object of the present invention to provide an optical information recording medium which uses diffraction gratings as information recording elements so that information can be recorded at a very high density, from which a plurality of pieces of information are read at once simultaneously so that information can be read at a higher speed, and which can be produced in mass production with a good formability at a low cost, and an information reading method for the same.
It is the third object of the present invention to provide an optical information recording medium which uses diffraction gratings as information recording elements so that information can be recorded at a very high density, from which a plurality of pieces of information are read at once simultaneously so that information can be read at a higher speed, and which can improve a security effect, and an information reading method for the same.
In order to achieve the first object, in an optical information recording medium according to the first aspect of the present invention, at least one cell comprising diffraction gratings is disposed on a planar substrate, and the cell is divided into n (n is an integer

REFERENCES:
patent: 4847478 (1989-07-01), Sugiura
patent: 5007690 (1991-04-01), Chern et al.
patent: 5331626 (1994-07-01), Sugiura
patent: 5337301 (1994-08-01), Sugiura et al.
patent: 5359591 (1994-10-01), Nomoto
patent: 5400313 (1995-03-01), Belser et al.
Patent Abstracts of Japan, vol. 17, No. 358, (M-1440), Jul. 7, 1993.

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