Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1988-08-12
1991-03-19
Richardson, Robert L.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
G11B 700
Patent
active
050016911
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to information recording and reading techniques using modulated electromagnetic beam effect, wherein the read-write head and optical information carrier are displaced in relation to each other.
2. Description of the Related Art
Known in the art is an optical storage device (U.S. Pat. No. 4,404,571) employing a cylindrical information carrier. This known optical storage device has a very low density of information recording, since it uses only one optical head and has intervals between tracks.
The closest prior art, both technically and by the effect obtained, is an optical storage device (DE, A, 2 522 405) comprising an optical information carrier having reference tracks on the recording coating thereof, at least two optical heads which are optically connected with said optical information carrier, each said optical head being made of several optically connected elements, including a source of modulated coherent radiation, a movable optical element, a beam splitter, a photodetector having its first output connected to a repective input of an external control device, at least two autofocusing units, each having its input connected to a second output of the photodetector of a respective optical head, while the output of each autofocusing unit is kinematically connected to a movable optical element of its optical head, at least one tracking unit made as a disc, having its input connected to a third output of the photodetector.
This optical storage device is deficient in that its information recording density is insufficient because it is equipped with an inadequate tracking system which provides tracking of information tracks on the entire surface of the recording coating of the optical information carrier.
SUMMARY OF THE INVENTION
The invention is to provide an optical storage device in which a larger part of the recording coating of the optical information carrier is made free from reference tracks and record information tracks instead in order to make the density of recording on the optical information carrier much higher.
The invention consists of an optical storage device comprising an optical information carrier having reference tracks on its recording coating, and at least two optical heads optically connected to the optical information carrier. Each such optical head comprising several optically connected elements arranged one after another, including a source of modulated coherent radiation, a movable optical element, a beam splitter, a photodetector having its first output connected to a respective signal input of a control unit coupled to a data trunk line, whose signal outputs are connected to inputs of sources of modulated coherent radiation of respective optical heads. The invention further comprises at least two autofocusing units, each having its input connected to a second output of the photodetector of a respective optical head, while the output of each autofocusing unit is kinematically connected with a movable optical element of its optical head. At least one unit for tracing a track on the optical information carrier, which has its input electrically connected to a third output of a photodetector. The invention also comprises a track switching unit inserted between the input of the track tracing unit and the third output of the photodetector whose fourth output is connected to a second input of the track switching unit whose third input is connected to a first address output of the control unit. An information addressing unit 13 kinematically connected with the optical information carrier and has its first input connected to a second adress output of the control unit, while its second input is connected to the output of the track tracing unit. There is provided an optical information carrier placed in a container filled with an immersion fluid and having transparent parts in the walls thereof, which are located opposite optical heads, a stationary optical element being placed on each such transparent part, th
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patent: 4423426 (1983-12-01), Kitamura
Antonov Alexandr A.
Petrov Vyacheslav V.
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