Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1987-10-06
1989-03-07
Sikes, William L.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369100, 369113, 369114, 369115, 369121, 346 76L, 346125, 346138, 358296, 358300, G11B 700, G01D 1510, H04N 121
Patent
active
048113271
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to information accumulating devices and, in particular, to optical storage devices.
BACKGROUND ART
Intelligence of computers is largely dependent on the sophistication of their external memory. At present, the overall speed of computers is lower by two or three orders than that of their computing units precisely because of inadequate external memories. Basic technical characteristics of external memories include information capacity, recording density, access time, information exchange speed, and storage reliability. Optical external memories possess certain advantages as contrasted to magnetic external memories, such as larger capacity, greater density and reliability and are therefore more promising.
Known in the art is an optical memory (IEEE Spectrum, 1979, 11, N.2, pp.33-38) comprising a source of modulated coherent radiation including a laser and a modulator and optically connected with a movable information carrier made as a sealed optical disk, a recording medium being coated on the internal surfaces of transparent walls of the disk, and an information addressing unit.
However this optical memory is deficient in that it is not very reliable and its recording density is not sufficiently high. It is not reliable because the optical disk is rather fragile and, also, because the working surfaces of the optical disk tend to deform by changes in the atmospheric pressure. Low recording density is due to variations in recording density for storage tracks having different radii. The resolution of the "dry" objective lens in the movable optical head is low which adds to this disadvantage, the numerical aperture of the lens cannot be larger than one.
The closest prior art, both technically and by the result obtained, is an optical memory (GB, A, No. 1 580 398) comprising optically connected elements: a source of modulated coherent radiation and a cylindrical information carrier equipped with a rotational drive. The cylindrical information carrier is a rigid nontransparent cylinder whose external surface is covered by a recording coating and which carries, by means of separating rings, an external relatively thin protective transparent cylinder. In the process of operation the external protective transparent cylinder rotates with the rigid nontransparent cylinder. The internal space of the cylindrical information carrier is communicated with the atmosphere in order to avoid deformation of the external protective cylinder by changes in the atmospheric pressure.
But this optical memory also has several disadvantages. Its recording density is low and it is not sufficiently reliable. Low recording density is due to the fact that the recording coating used to register information can be applied only on the external surface of the rigid nontransparent cylinder and, also, due to the use of a "dry" objective lens having a low numerical aperture. This optical memory is not reliable because the internal space of the cylindrical information carrier is not sealed off from the environment and, when the temperature conditions of the carrier change in the process of operation in relation to the temperature of the environment, this carrier "breathes" in or out. The internal space sucks in large amounts of dust, moisture, and other foreign bodies which are deposited on the surface of the recording coating, which substantially reduces reliability of information reading-recording. The reliability of this prior art memory device is also affected because the surface of the protective cylinder is often damaged in the process of its fast rotation.
This invention is to provide an optical storage device having such an arrangement as to increase the sharpness of focus of the radiation beam carrying information and, simultaneously, to make more dense recording more reliable.
This is achieved by that in an optical storage device comprising a source of modulated coherent radiation, which is optically connected to a cylindrical information carrier equipped with a drive for rotation, and provided w
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IEEE Spectrum, 1979, 11, N.2, pp. 33-38.
Antonov Alexandr A.
Gapchenko Leonid M.
Gorshkov Nikolai V.
Kovtun Valery D.
Krjuchin Andrei A.
Healy Brian M.
Institut Problem Modelirovania v energetiki AN Ukr. SSR
Sikes William L.
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