Optical recording medium having a constant birefringent property and an alterable photochromic property
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United States of America Patent
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May 31, 1994
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N/A
app pub date -
Oct 15, 1993
filing date -
Sep 22, 1989
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Abstract
A recording medium comprises a recording layer, a birefringent layer, and a reflecting layer. The recording layer is formed of a material whose optical rotatory power is alterable such that in one state no optical rotatory power is present and, in a second state, optical rotatory power is present. Information is recorded in the recording layer by selectively altering the state of the recording layer. The birefringent layer is formed of a material having constant birefringence without regard to the state of the recording layer. The reflecting layer reflects a light beam transmitted through the recording layer and the birefringent layer to reintroduce the beam into the birefringent layer and the recording layer. A method of reproducing information from this recording medium applies a polarized light beam to the recording medium and detects change of the polarized state of the polarized light beam reflected from the recording medium, thereby reading the information recorded in the recording layer. According to the inventive recording medium and reproducing method, the information is reproduced by detecting the presence of optical rotatory power of the recording layer.
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