Photocopying – Including fiber optics
Patent
1983-02-14
1985-06-11
Moses, R. L.
Photocopying
Including fiber optics
355 5, 355 7, 364518, G03G 1500
Patent
active
045224820
DESCRIPTION:
BRIEF SUMMARY
This invention relates to information storage and retrieval involving optical storage.
In an information storage system, it is a common requirement to input a quantity of information less than the total capacity of the system, to index that information for easy retrieval and to refer to that information (i.e. to use it) using the index. At a later date more information may be input and the process repeated until the storage capacity of the system is full or nearly full. It may then be possible to extend the storage capacity. This type of use is exemplified by a conventional filing cabinet in which documents may be placed and indexed in such a manner that they can be found easily, and in which more documents can be added as they come to hand.
Because of the bulk of large quantities of paper, it is now common to store information in various forms more compact than the original characters or graphical representations on paper. Common forms of high density information are small-scale reproductions of the original, encoded forms of the original such as video (television-type) encoding and digital representations of the characters constituting the original.
Two different optical storage systems have hitherto found commercial acceptance, one employing microfilm and the other employing optical laser storage methods.
In microfilm systems, high capacity optical data storage is effected photographically on light-sensitive microfilms, such as microfiche. Capacities of up to ten million bits/mm.sup.2 have been achieved, the maximum being limited by the quality of the photographic emulsions available. The production of microfilms for a very high capacity system is therefore very expensive. Microfiche is one type of microfilm system which involves reproducing a large number of pages of information on a single sheet which can be searched manually in two dimensions. Such a microfiche system is disclosed in U.S. Pat. No. 4,179,743. In addition to storing pages, the system stores adjacent each page a marker related to the content of the page. That system is therefore applicable only to storing information which is intrinsically ordered or self-indexed (in the manner of a dictionary).
Optical laser storage systems using discs have been made wherein information is stored in the form of a coded series of pits in concentric rings, or in spirals, on the surface of a transparent disc. The information is read using a source of coherent laser illumination focussed on each of the pits in turn as the disc is rotated. The spot size of the illumination must be less than or comparable to the area of a single pit. The light diffracted by the pits, either on reflection or in transmission, is monitored and is used to reconstruct electronically an image of the stored information. In this case the information is necessarily encoded and so is not directly readable, requiring the use of electronic decoders to convert the stored information into signals suitable for a video display unit.
A disc system has been proposed with which it is possible to image optical information without the use of laser light and somewhat in the manner of microfilm or microfiche. Such a system is disclosed in British Patent Specification No. 1091981 and comprises the use of a disc having a spiral groove and, between the turns of the groove, a flat spiral land having a coating of photographic emulsion constituting a video track. A reading head is employed which has a pick-up which physically engages the groove for the purpose of accurately locating the reading head relative to the video track. Video data is recorded on the track so that a flying spot scanner can scan picture elements in a linear fashion.
An object of the present invention is to provide an optical information recording arrangement which permits information to be recorded in relation to an absolute position measuring system, enabling items of information to be recovered readily by a control system utilising that measuring system.
An object of preferred embodiments of the present invention is to provide a
REFERENCES:
patent: 3972610 (1976-08-01), Gross
patent: 4179743 (1979-12-01), Suzuki et al.
Journal of Optics, vol. 11, No. 1, Jan./Feb. 1980, (Paris, FR), "System d'Impression a Laser", p. 10.
Bradbrook John D.
Fisher John H.
Pettigrew Robert M.
Smith Alan M.
Comtech Research
Moses R. L.
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