Laminated phase plate and optical pickup using thereof
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United States of America Patent
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Issued Date -
Mar 24, 2005
app pub date -
May 25, 2004
filing date -
May 30, 2003
priority date (Note) -
Abandoned
status (Latency Note)
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Abstract
It is an object of the present invention to provide a wave plate which functions as a 1/4 wave plate where wave front aberration, temperature characteristics, and incident angle dependence are improved with respect to a plurality of wavelengths of an optical pickup unit or the like compatible with DVD and CD, and an optical pickup using the wave plate. In the laminated wave plate where a wave plate whose phase difference is a with respect to a monochromatic light of a wavelength .lambda. and a wave plate whose phase difference is .beta. are laminated so that their optical axes cross, and which the laminated wave plate functions as the 1/4 wave plate, a relationship between the phase difference a and the phase difference .beta. satisfies the following condition: .alpha.=.pi.n .beta.=.pi.m/2 however, n>1, and m>1 a material of one wave plate is a film having birefringence characteristics and a material of the other wave plate is quarts.
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