Patent ID: 7187641
Filing Date: 2007-03-06
Classification: G11B

Abstract:
1. An objective lens, comprising: a first meniscus-shape lens including a first object-side surface, which has a convex surface, and a first image-side surface, the first meniscus-shape lens having a positive reflective power; and a second meniscus-shape lens including a second object-side surface, which has a convex surface, and a second image-side surface, the second meniscus-shape lens having a positive reflective power; the first meniscus-shape lens and the second meniscus-shape lens being arranged in that order from an object side, wherein the objective lens satisfies the following formulas: where f is an object-side focus length of the objective lens, fF is a front focus, fB is a back focus, L H1H2 is a length between an object-side principal point H 1 and an image-side principal point H 2 , and L is a length on an optical axis of the objective lens between the first object-side surface and the second image-side surface.