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| Thermal transfer sheet |
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| What is claimed is: 1. A compound of the formula ##STR29## wherein K is the radical of a coupling ... |
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| Dye transfer type thermal printing sheets and method for printing |
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| Process for trichromatic dyeing or printing |
| What is claimed is: 1. A process for the trichromatic dyeing or printing of natural and synthetic ... |
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| Pressure-sensitive copying paper |
| We claim: 1. Pressure-sensitive copying paper comprising base paper neutral- or alkaline-sized with ... |
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| Heat transfer sheet |
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| Tear webbing |
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| Jet printing ink composition for glass |
| I claim: 1. An ink composition consisting essentially of 1 - 30% by weight linear novolac resin 0.4 ... |
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Optical card having optical grooves for access and wobbled marks for tracking and a recording-reproducing apparatus therefor
| Details |
Inventors: Nakamura, Shigeru; Tsunoda, Yoshito; Maeda, Takeshi;
Assignee: Hitachi, Ltd. (Tokyo, JP)
Primary Examiner: Levy; Stuart S.
Assistant Examiner: Weinhardt; Robert
Attorney, Agent or Firm: Antonelli, Terry, Stout & Kraus
An optical card of the present invention has a card-shaped recording layer whose optical characteristic is varied by a laser beam applied thereon, and a resin layer for protecting this recording layer. The recording layer has optical grooves provided at a substantially equal interval in the opposite end portions of the recording layer respectively and varying the light intensity of the laser beam when the beam traverses the grooves, and first and second optical markers provided at a prescribed interval in the direction of extension of each of the optical grooves and varying the light intensity of the laser beam which passes them. The optical grooves are made longer every prescribed number thereof than others, and the longer optical grooves are used for zone access, while the shorter optical grooves are used for track access in a zone. The first and second optical markers are provided at positions deviated alternately at equal distance from the center of a track, and operate as so-called wobble pits to detect a track error. These markers are used also as timing marks for generating a clock signal. |
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DETAILED DESCRIPTION In order to enable recording in an optical card apparatus, a laser beam flux needs to be focused as a minute spot on an information recording surface.
For this purpose, it is necessary to provide a tracking servo system for positioning the minute spot accurately and a system for recognizing a track address, unlike the aforesaid reproduction-only optical card apparatus.
One object of the present invention is to furnish an optical card and a recording-reproducing apparatus therefor which enable the recognition of the track address without using any special address pits.
Another object of the present invention is to furnish an optical card and a recording-reproducing apparatus therefor which enables the access to a zone comprising many tracks.
A further object of the present invention is to furnish an optical card and a recording-reproducing apparatus therefor which enables precise tracking by means of a simple system and further enables the detection of a clock signal and a position of a track.
The optical card of the present invention is characterized in that optical reference markers are provided beforehand at positions located on the right and left sides of the center of a track alternately and spaced at equal distance therefrom, and in that optical reference grooves are also provided beforehand in the opposite ends of the track.
In the same way as in an optical disk, it can be supposed to form a track in the form of a projection or a groove on a recording surface and to record address pits in the form of bosses or pits in one end of the groove beforehand.
While the optical disk rotates at a fixed speed, however, the optical card moves in reciprocation, and therefore the address pits can not be recorded effectively in a scanning section required for the feeding speed of the optical card to reach a prescribed rate.
Moreover, data areas are lessened, since address pit areas are also necessitated.
In place of the address pits, in the present invention, an optical reference groove or projection, for instance, is provided in the opposite ends of each track (an imaginary channel for recording data pits), and the passing of a light spot across these optical reference grooves is detected to recognize a track address whereat the light spot is positioned
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