TWO-POSITION IMAGE FORMING OBJECT LENS FOR OPTICAL PICKUP

摘要

PROBLEM TO BE SOLVED: To provide a two-position image forming object lens for an optical pickup which can be used in common for a 0.6 mm disk and a 1.2 mm disk. SOLUTION: In the two-position image forming object lens 26, an aberration to a light focus in the recording surface of the loaded disk is corrected, and at least one side surface of the incident surface and the exit surface is provided with the first aspherical surface and the second aspherical surface which are different each other. Light passing through the whole area of the first aspherical surface and the second aspherical surface is focused on the 0.6 mm disk, and light passing through the area of the first aspherical surface is mostly used for the 1.2 mm disk. According to the optical pickup having such a two-position image forming object lens 26, the ratio of signals to noises of reproduced signals is improved with high optical efficiency because of not dividing the light and the optical pickup capable of performing not only reproducing but also recording is obtained.