Objective lens for video disk reproduction

Abstract

Abstract PURPOSE:To obtain a clear objective lens of small-sized, lightweight constitution which has long operation distance, by permitting respective lenses in the 1st group of a biconvex lens and a negative meniscus lens cemented together, in the 2nd group of a biconvex lens and the 3rd group of a positive meniscus lens to meet requirements. CONSTITUTION:An objective lens system consists of a lens L1 constituted by cementing a biconvex lens 1 to a negative meniscus lens 2 having a concave surface on a photodetector side, a biconvex lens L2, and a positive meniscus lens L3 having a concave surface on a video disk side. Conditional inequalities (1)-(4) hold,where the focal lengths of the lens groups L1, L2, and L3, and the entire system are f1, f2 f3, and f, the space distance on the optical axis between the L1 and L2 is d1.2, and the radius of curvature of the cemented surface 3 is r1. Consequently, a semiconductor laser is usable as a light source and the system has small-sized, light- weight constitution, less residual aberrations and long operation distance.

Inventors

• 👤 Yoji Kubota
• 👤 Hidetoshi Hadama

Bibliographic Details