OBJECTIVE LENS, CONDENSING OPTICAL SYSTEM, OPTICAL HEAD DEVICE, OPTICAL DISK DEVICE, OPTICAL DISK, MICROSCOPE AND EXPOSURE DEVICE

摘要

PURPOSE:To constitute a condensing optical system capable of condensing a light beam to a diffraction limit on an optical disk having the different thickness of a substrate, and an optical head device and an optical disk device capable of recording and reproducing the optical disk having the different thickness of the substrate. CONSTITUTION:A holographic lens 107 is designed so that the transmitted light (zero-order diffracted light) 61a of the light beam 3a may have sufficient intensity. An objective lens 4 is designed so that the condensing spot of the diffraction limit can be formed on the optical disk having the small thickness (t2) of the substrate 37 when the light beam 61 transmitted through the lens 107 without being diffracted is made incident. The +1st order diffracted light 64 diffracted by the lens 107 is condensed on an information medium 5 by the objective lens 4 and converged to the diffraction limit through the substrate 37 having the thickness t1 by compensating aberration.