Objective lens, optical element, optical pick-up apparatus and optical information recording and/or reproducing apparatus equipped therewith
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United States of America Patent
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Jan 18, 2011
Grant Date -
Mar 26, 2009
app pub date -
Dec 2, 2008
filing date -
Oct 12, 2001
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A hybrid objective lens has a refractive lens and a diffractive optical element constructed by plural coaxial ring-shaped zones on at least one optical surface thereof. When n1, n2 and n3 each is a diffraction order of a diffracted ray having a maximum light amount among diffracted rays of each of first, second and third light flux having wavelength .lamda.1, .lamda.2 and .lamda.3 when respective light flux comes to be incident into the diffractive structure respectively, the following formulas are satisfied: |n1|>|n2|, and |n1|>|n3|, and the hybrid objective lens converges a n1-th, n2-th and n3-th order diffracted ray of the first, second and third light flux onto an information recording plane of each of the first, second ant third optical information recording medium respectively so as to form an appropriate wavefront within respective prescribed necessary image side numerical apertures.
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