GB2152695A

GB2152695A - Information storage and retrieval

Info

Publication number: GB2152695A
Application number: GB8400257A
Authority: GB
Inventors: Larry Daniels
Original assignee: Applied Holographics PLC
Current assignee: Opsec Security Group Ltd
Priority date: 1984-01-06
Filing date: 1984-01-06
Publication date: 1985-08-07
Also published as: GB8400257D0

Abstract

A method and disc for the storage of information comprising making a 3-dimensional representation of the information, for example, music in the form of a record, compact disc, etc reproducing this representation as a hologram (1) and scanning the hologram with laser (5) light to produce electrical signals representative of the information stored. <IMAGE>

Description

SPECIFICATION Information storage and retrieval INTRODUCTION This invention relates to information storage and retrieval and particularly, although not exclusively, to the recording of sound information, for example music, on a disc so that the music may be reproduced whenever required by the use of suitable equipment.

It has been found recently that very great benefits can be achieved by the use of so called "compact discs" for the recording and reproduction of music. So called compact discs give reproduction which is much sharper in tonal quality and is almost completely free of interference and spurious noise when compared with the well known plastics record or disc.

These compact discs are made of metal and the information is stored on these discs in much the same way as the information is stored on a plastics disc, i.e. by the formation of a single groove the dimensions and contours of which vary greatly. The essential difference between a compact disc and a plastics disc is that instead of a stylus being used to. pick up the information a laser beam is used with the compact disc and the laser light which is reflected from the contours of the groove is picked up by a receiver, converted into electrical energy and this electrical signal used after suitable amplification to feed a loudspeaker. Apart from quality control an added advantage of the laser method is that the disc does not wear out.

One of the main disadvantages at the present time in the production of compact discs is the cost of recording the information. Several stages have to be employed in the manufacture of a disc.

OBJECT OF THE INVENTION It is the main object of this invention to produce a so called compact disc very much more cheaply than has hitherto been possible.

STATEMENT OF INVENTION According to the present invention there is provided a method of information storage and retrieval which includes the recording of the information in 3-dimensional form, reproducing the 3-dimensional representation as a hologram for the storage of the information and scanning the hologram with laser light to produce electrical signals representative of the information stored.

In one particular aspect of the invention the method includes the storage of sound, for example music.

The invention also includes a disc on which is stored information comprising a rigid base and a hologram fixed to the base said hologram possessing the stored information in the form of a track whereby the track may be scanned by laser light to retrieve the information.

Conveniently the hologram may be faced with a protective transparent covering.

DRAWINGS Figure 1 is a diagrammatic view of a method of information storage and retrieval in accordance with the invention; and Figure 2 shows a cross section through a disc constructed in accordance with the invention.

SPECIFIC DESCRIPTION Referring first of all to Fig. 1 a disc generally indicated at 1 comprises a rigid base 2 which preferably is made of metal and must be rigid enough so as to prevent an distortion of a hologram 3 fixed rigidly thereto. This hologram 3 is in the form of a disc having a track with contoured sides and depth or with other characteristics equivalent to the 3-dimensional counterpart which would be a normal so called compact disc. The hologram 3 may be produced from a compact disc of normal construction and would be a faithful reproduction of the compact disc when scanned with laser light.

The disc 1 is mounted so as to be rotatable about an axis 4 at a given speed.

A laser 5 emits laser light 6 which is reflected by mirror 7 to irradiate at point 8 part of the groove in hologram 3. This laser light is reflected back from the hologram 3 and is picked up by sensor 9 which feeds the continuous electrical signals being received to further equipment (not shown) which will inevitably comprise an amplifier and loud speaker thereby reproducing the sound inherent within the hologram.

The mirror 7 with sensor 9 may be arranged for radial travel in relation to the disc 1 on platform 10 the radial travel in the directoin of arrows 11 being synchronised with the speed of rotation about axis 4 of the disc 1.

A modification of the disc 1 is shown in Fig. 2 in that the hologram 3 is faced with a protective transparent covering 12 so as to prevent any inadvertent damage occuring to the hologram itself. This protective covering may simply be a transparent plastics material.

The protective covering 12 may not only face the hologram but may encapsulate the entire disc.

Although the invention has been described above in relation to a compact disc it has wider application for the shorage and retrieval of any type of information which could nor mally be stored by 3-dimensional means. So far as the scanning laser is concered the hologram accurately replaces the 3-dimensional disc and therefore the reproduction obtained by the hologram is equally as accu rate as that obtained from its 3-dimensional counterpart.

Claims

1. A method of information storage and retrieval which includes the recording of the information in 3-dimensional form, reproducing the 3-dimensional representation as a hologram for the storage of the information and scanning the hologram with laser light to produce electrical signals representative of the information stored.

2. The method as claimed in Claim 1, which includes the recording of sound information in 3-dimensional form on a disc, reproducing the 3-dimensional form of the sound information as a hologram on a disc and scanning the hologram with laser light to produce electrical signals for the reproduction of the sound.

3. The method as claimed in Claim 2, in which the hologram is mounted on a backing to prevent distortion.

4. A disc on which is stored information, comprising a rigid base and a hologram fixed to the base, said hologram possessing the stored information in the form of a track whereby the track may be scanned by laser light to retrieve the information.

5. A disc as claimed in Claim 4, in which the hologram is faced with a protective transparent covering.

6. A method of information storage and retrieval substantially as herein described.