Recording medium having substrate with thickness dependent on numerical aperture of object lens, method of forming the optical medium and optical recording/reproducing apparatus
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United States of America Patent
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Jun 8, 2004
Issued Date -
N/A
app pub date -
Jul 20, 2001
filing date -
Apr 4, 1998
priority date (Note) -
Expired
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Abstract
A high density optical disc that can be driven changeably with the existent optical disc by the same driving apparatus. On the recording surface of the optical disc, a light transmissive layer with a thickness of about 0.2 to 0.4 mm is formed. The recording face is accessed by allowing a light beam with a wavelength of 395 to 425 nm in a spot shape to be irradiated onto it. Also, the light beam is converged in a spot shape by an objective lens having the numerical aperture of about 0.62 to 0.68.
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