OPTICAL HEAD AND OPTICAL INFORMATION RECORDING AND REPRODUCING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an optical head and an optical information recording/ reproducing device which can make recording and reproducing on optical recording media of the specifications both for the next generation using a thin base plate and for the conventional DVD or CD by making the wavelength short for the light source and the numerical aperture of the objective lens high. SOLUTION: The light of 405 nm wavelength from the optical-system 1a is made parallel light and radiated to the objective lens 4a and focused on a base plate 5a 0.1 mm thick. The light of 650 nm wavelength from the optical- system 1b is radiated to the objective lens 4a as the divergent light and focused on a base plate 5b 0.6 mm thick. Spherical aberration remaining in the light of the 650 nm wavelength is reduced by the magnification change of the objective lens 4a and further reduced by the selective wavelength filter 3a.