OBJECTIVE LENS, OPTICAL HEAD USING THE SAME AND OPTICAL DISK DEVICE

摘要

PROBLEM TO BE SOLVED: To record and to reproduce information of optical disks having different thicknesses employing a single optical head. SOLUTION: This optical head consists of a light source 1, an objective lens 8 which converges a luminous flux 3 emitted from the source 1 to the optical information medium having disk base material thicknesses t1 or t2 and collects reflected light beams 13a and a photodetector 16 which receives the beams 13a. If the thickness t2 is approximately twice as thick as t1, the peripheral section is constituted so that the aberration becomes approximately minimum to the thickness t1 and the center section is constituted so that the aberration becomes approximately minimum to a disk base material thickness (t2×0.7 to t2).