发明申请
US20080019256A1 Objective lens and optical pickup system 审中-公开
物镜和光学拾取系统

Objective lens and optical pickup system
摘要:
There is provided an optical pickup system which includes a first light source emitting first light having a wavelength λ1, a second light source emitting second light having a wavelength λ2 longer than the wavelength λ1, a third light source emitting third light having a wavelength λ3 longer than the wavelength λ2, and an objective lens focusing the first light on an information recording surface of a first optical recording medium, focusing the second light on an information recording surface of a second optical recording medium, and focusing the third light on an information recording surface of a third optical recording medium. In the optical pickup system, at least one lens surface of the objective lens is divided into a plurality of concentric sections with an optical axis, having a step at each boundary between the sections, each of the sections has a different aspherical shape and m1>m2>0 and −0.060≦m3≦−0.020 are satisfied where an imaging magnification at the first light is m1, an imaging magnification at the second light is m2, and an imaging magnification at the third light is m3 in the objective lens. This enables a decrease in aberration at the first light and the second light and an increase in object distance at the third light. Further, this step enables the shared use of a photodetector for detecting the first light and a photodetector for detecting the second light.
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