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AssigneePanasonic Intellectual Property Management Co., Ltd.
InventorsKatsuhiko Hayashi, Yasuhiro Tanaka, Michihiro Yamagata, Yoshiaki Komma
Estimating the term…
An objective lens element having excellent compatibility with optical discs having different base material thicknesses is provided. The objective lens element has optically functional surfaces on an incident side and an exit side. At least either one of the optically functional surfaces on the incident side and the exit side includes a diffraction portion which satisfies at least either one of the following formulas (1) and (2): θ1×θ2<0 (“×” represents multiplication) (1), (sin θ2)/λ2=−(sin θ1)/λ1 (2), where θ1 is the diffraction angle of a light beam having a diffraction order providing the maximum diffraction efficiency at the wavelength λ1, and θ2 is the diffraction angle of a light beam having a diffraction order providing the maximum diffraction efficiency at the wavelength λ2.
An objective lens element having optically functional surfaces on an incident side and an exit side, the objective lens element converging a first incident light beam of wavelength λ1 through a base plate having a thickness t1 to form a spot, and converging a second incident light beam of wavelength λ2 longer than the wavelength λ1 through a base plate having a thickness t2 larger than the thickness t1 to form a spot, wherein:
Dependencies are inferred from the claim text.