Is a
Patent attributes
Current Assignee
Patent Jurisdiction
Patent Number
Date of Patent
September 21, 2010
Patent Application Number
11984803
Date Filed
November 21, 2007
Patent Primary Examiner
Patent abstract
A coupling lens for chromatic aberration correction is placed between a light source and an objective lens for focusing light beams with a plurality of wavelengths on an information recording surface of an optical recording medium, and at least one surface of the coupling lens includes a plurality of annular zones having a step concentric with an optical axis. The coupling lens is designed so that when a wavelength λ1=380 to 430 nm and a height of the step is d=m1λ1/(n1−1) where m1 is an actual number and n1 is a refractive index of the coupling lens at the wavelength λ1, 9.9≦m1≦10.1 is satisfied.
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