Importance

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Abstract

An optical recording medium includes a silver grain layer containing a large number of blackened fine silver grains and a coloring matter layer containing coloring matter on a base board and the coloring matter has an ability of absorbing near-infrared ray. When laser beam having a density of optical energy more than a boundary which represents a threshold with respect to the density of optical energy is radiated to the optical recording medium, a part of the latter is deformed to form a plurality of convexities which will be utilized as optical recording pit. The recording pits formed in this way are detected by presence or absence of reflection of radiated light whereby the content of optical recorded informations can be read. The optical recording pits are not deformed further irrespective of how long a reading light comprising laser beam having a density of energy less than the threshold is repeatedly radiated to the optical pits. Accordingly, any reduction of S/N ratio of a signal does not take place as time elapses.

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First Claim