Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1985-07-08
1990-08-07
Canney, Vincent P.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 97, 369 4421, 235456, 235487, 235494, G11B 709
Patent
active
049473832
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to information storage media in which information is stored as multiple machine readable data entries arranged in frames which are themselves arranged in plural, generally parallel channels, and which further contain machine readable synchronization markers. The data entries may typically be bits of digital data. In further aspects, the invention is concerned with the reading or observation of the synchronization markers for various purposes including the achievement of synchronization between the reading head and the channels and frames. Finally, the invention provides an arrangement for distinguishing local faults in position indicators from true indications of position errors.
BACKGROUND ART
Applicant's prior international patent application No. PCT/AU81/00188 (International Publication No. WO81/01109) discloses a simple microfiche constituting an information storage medium of the kind in question That application outlines a technique for compensating for fractional misregistration between detector elements of the read head and optically machine readable data entries in the fiche, and also suggests compensation for integral or larger scale misregistration by utilizing characteristic marker patterns among the data entries in the frames.
It is known to synchronize read heads with rows of data entries by means of accurate synchronization markers at the end of each row. In the most basic case, such markers comprise perforations which register with sprocket teeth, but machine readable markers are also employed. It is further known to provide, for synchronization purposes, markers of specific shape among data entries, or characteristic opaque or transparent zones.
The significance of applicant's aforementioned international patent application is that it renders practicable the storage of information on microfiche in optically readable binary format. It is an objective of the present invention to provide a convenient arrangement of synchronization markers which occupies a minimum of possible information storage space and which performs substantially all the principal synchronization functions required. It is a further objective to provide a method of reading information from a storage medium of the kind described.
Even once synchronization has been initially achieved, local faults may arise in the regular position indicators or markers by which synchronization is sustained. Many devices currently exist which need to determine the position of a read head relative to data, but most such devices are read/write in that they can record data as well as read it. Any fault during the writing process may result in mispositioned data and the reading process needs to recognize this possibility. Hence it is common for each position determination to override all previous determinations in an absolute fashion, or if any note of previous determinations is made, they serve only to alert the reading system to the presence of an error.
In the case of magnetic discs, for example, the synchronization pattern along the track (whether before the sector number data or on the servo surface) must normally be complete and accurate for the sector to be accessible. Any fault in the pattern generally results in the sector being unusable.
Similarly the next frame on magnetic tape drives must be observed within a specified period since the last or an error is reported, so that a systematic error in frame positioning such as an incorrect density cannot in general be accommodated.
Such position determination processes as used in the conventional computer context may well be best suited to read/write media. When applied to a read only medium whose production is carefully controlled, such as the optically readable media with which this invention is primarily concerned, they suffer excessive sensitivity to faults arising from spot obliteration such as by dust, medium nonuniformity etc. Reverting to the example above, a single bit fault in the synchronization pattern on a magnetic disc is suffi
REFERENCES:
patent: 3072889 (1963-01-01), Willcox
patent: 3209129 (1965-09-01), Sundblad
patent: 3322935 (1963-07-01), Wyke et al.
patent: 3437793 (1969-04-01), Van Berkel et al.
patent: 3542286 (1970-11-01), Binkley et al.
patent: 3718914 (1973-02-01), Muller
patent: 3727183 (1973-04-01), LeMay
patent: 3780266 (1973-12-01), Mudsam et al.
patent: 3795902 (1974-03-01), Russell
patent: 3872445 (1975-03-01), Pease
patent: 3896295 (1975-07-01), La Plante
patent: 3919697 (1975-11-01), Walker
patent: 3959784 (1976-05-01), Meier
patent: 4074114 (1978-02-01), Dobras
patent: 4087166 (1978-05-01), Rothbart et al.
patent: 4118735 (1978-10-01), Wilkinson
patent: 4149269 (1979-04-01), Abe et al.
patent: 4198701 (1980-04-01), Reddersen et al.
patent: 4213040 (1980-07-01), Gokey et al.
patent: 4228468 (1980-10-01), Nagano et al.
patent: 4251126 (1981-02-01), Minoura et al.
patent: 4300123 (1981-11-01), McMillin et al.
patent: 4328415 (1982-05-01), Eaton
patent: 4357596 (1982-11-01), Feilchenfeld
patent: 4430563 (1984-02-01), Harrington
patent: 4439672 (1984-03-01), Salaman
Patent Abstracts of Japan, vol. 6, no. 237 (P-157) (1115) Nov. 25, 1982.
Patent Abstracts of Japan, vol. 1, no. 129, Oct. 25, 1977, p. 5869 E 77.
Canney Vincent P.
Hudson Allen Limited
Young W. R.
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