Patent ID: 7298687
Filing Date: 2007-11-20
Classification: G11B

Abstract:
1. An optical recording media objective lens for converging working lights of a first wavelength and a second wavelength at predetermined points onto a first optical recording medium and a second optical recording medium, respectively, the working light of the first wavelength being converged at a first numerical aperture onto the first optical recording medium and the working light of the second wavelength being converged at a second numerical aperture onto the second optical recording medium for recording or reproducing information, said optical recording media objective lens comprising: an aperture adjusting zonal part on at least one of its lens surfaces for apparently eliminating light at the periphery of a light flux having a wavelength λ the aperture adjusting zonal part is formed between two concentric stepped parts about the optical axis of the objective lens in a manner such that the following Conditions (1) and (2) are satisfied where Δ Δ m and n are integers; δ δ wherein the following Condition (3) is also satisfied: where a is the distance in a direction orthogonal to the optical axis between the boundary of the smaller one of the first and second numerical apertures and the inner one of the two stepped parts, b is the distance in a direction orthogonal to the optical axis between the inner stepped part and the outer stepped part, and c is the distance in a direction orthogonal to the optical axis between the outer stepped part and the boundary of the larger one of the first and second numerical apertures.