OPTICAL PICKUP DEVICE AND RECORDING/REPRODUCING DEVICE

摘要

PROBLEM TO BE SOLVED: To always keep constant a light quantity incident on the aperture diaphragm of an object lens while correcting a spherical aberration by preliminarily passing a luminous flux incident on the object lens through an expander lens and also to make performable excellent writing and reading of an information signal to an optical recording medium by not changing rim intensity(RI). SOLUTION: The aperture diaphragm 6 of the object lens 7 is positioned at the focal position of a second lens group 5b of the side close to the object lens 7 consisting of the expander lens 5.