OBJECTIVE OPTICAL SYSTEM FOR OPTICAL RECORDING MEDIUM, AND OPTICAL PICKUP DEVICE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To improve the flexibility in optical system arrangement selection for miniaturizing a device so that it is possible to condense light at a prescribed position in a state in which aberration is improved even if used light is allowed to enter also three kinds of optical recording media as parallel light, by changing the space between a diffraction optical element and an objective lens according to the type of the optical recording medium by using an objective optical system comprising the diffraction optical element and the objective lens.

SOLUTION: The diffraction optical element L1in which a surface at a light source side is set to be a diffraction optical surface with a plane as a base and a surface at the side of the optical recording medium is set to be a recessed aspherical surface, and both convex objective lenses L2in which both the surfaces are rotational aspherical surfaces are arranged successively from the light source side so that the space is variable. Each light used for AOD9a, DVD9b, CD9c enters as parallel light, and secondary diffraction light (λ1) primary diffraction light (λ2), and primary diffraction light (λ3) outputted from each L1are condensed on a prescribed optical recording medium. An air space D2between L1and L2is set so that an interval d1 in λ1 condensation becomes equal to an interval d2 in λ2 condensation and is smaller than an interval d3 in λ3 condensation.

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