RECORDING/REPRODUCING OBJECTIVE LENS OF OPTICAL INFORMATION RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To obtain an objective lens which is integrally molded with a bobbin part to regulate a diameter of condensed luminous flux, by configuration of the objective lens of an optical pickup.SOLUTION: A level difference 3 is formed in a bent surface S1 on a light source side of the objective lens 1 integrally molded with the bobbin 2 at a location on the side of an optical information recording medium, which corresponds to a numerical aperture NA to be required according to a wavelength of the laser light source and an information recording density, the bent surface having a discontinuous change in a normal direction. By this arrangement, the luminous flux passing through the refraction surface on outer side from the discontinuous part 3 is not focused on a light focusing point where the light passing through the inside thereof is focused. The luminous flux diameter effective for the recording/reproducing operation is regulated by this discontinuous part 3 to form the condensed light beam with a predetermined numerical aperture NA.