Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Patent
1987-11-17
1989-06-27
Laroche, Eugene R.
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
369275, 369284, G02F 101, G02F 117
Patent
active
048423815
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to electrochromic data recording systems and has particular relevance to discs for recording digital data such as audio visual data.
Audio visual data can presently be recorded by a disc manufacturer on video discs and compact discs. It is a disadvantage of present video and compact disc systems that the digital optical information representing the video and audio material is fixed in the disc and cannot be altered after manufacture.
The laser video disc system has been fully described in the literature and is the subject of two recent books (one of these is "Principles of Optical Disc Systems", by G. Bouwhuis et al, Adam Hilger Ltd, 1985). The discs on which the digital optical information is stored, called video discs, are normally made from a master disc (cf. gramophone records). Some video disc systems however have an on-line optical recording facility, cf. magnetic discs. Writing involves running the laser at higher power levels and having a disc made of a suitable arrangement of materials so as to accept recording and give good reading properties. In such a system no mastering would be done. So far all the disc arrangements, herein called "disc stacks", involve thermal processes. Thus in one arrangement the recording material is a tellurium-selenium alloy thin film in which a hole is "burnt". Another arrangement involves bubble formation in a polymer film, and yet another depends upon thermally induced magneto-optic effects. There is a need for a disc stack on which the digital information can be written and subsequently erased and then rewritten, many times.
In British Patent Application No. 2164466 (published after the priority date hereof) there is described an electrochromic material in which a colour change, which may be in the visible range, may be made by the passage of an electric current only when the electrochromic material is at a suitably high temperature.
In United Kingdom Patent Application No. 2164170A there is disclosed an electrochromic material having two host layers each of which can receive and give up guest atoms. The optical density of at least one of these layers at some frequency of light is varied by the concentration of guest atoms. The colouration need not necessarily be in the visible spectrum. The two layers are coloured to different extents by the presence of the same amount of the same guest metal atom and indeed one layer may be scarcely affected or unaffected and this is used as the basis for varying the optical density of devices containing the said layers by driving guest atoms between the layers by passage of electric current.
It has now been discovered that it is possible to produce an electrochromic data recording device, preferably in the form of a disc, comprising means defining an axis of rotation a data recording portion surrounding the said axis, at least one electrochromic zone in said recording portion and means for selectively supplying to and withdrawing from said zone guest atoms which produce an optical change in said zone, which means is substantially inoperable at room temperature but is operable at an elevated temperature. The elevated temperature may be produced locally in the device by a laser to encode data in the device.
The invention relates not only to devices of this kind but also to apparatus for writing information into or erasing information from a device such as a disc according to the invention comprising means for supporting a recording device, means for applying a general electrical potential difference across the device over a recording area of the device, and a laser for selectively applying light energy to individual locations in the recording area to heat the device at said locations.
Means may be included for general heating of the device also. Such means may be controllable to heat the device selectively to (1) a lower temperature at which it is not conducting, and (2) a higher temperature at which it is conducting for erasure.
Means may be provided for heating selected zones of the device for partia
REFERENCES:
patent: 4075610 (1978-02-01), Crandall et al.
patent: 4728177 (1988-03-01), Green
Kazan, "Photochromic Disk File", IBM Technical Disclosure Bulletin, vol. 14, No. 5, Oct. 1971.
LaRoche Eugene R.
McCutcheon Nathan W.
National Research Development Corp.
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