| 摘要 |
PROBLEM TO BE SOLVED: To carry out highly precise focus control while preventing degradation of the focusing signal due to wavelength multiplexing by achromatizing the optical systems of the detector and illuminator. SOLUTION: The optical pickup consists of a beam splitter 16 which passes the optical beam from the semiconductor laser 14 and deflects the reflected light from an optical disk 1, a condenser lens 22 to detect this reflected light, a cylindrical lens 23, and a detecting means composed of photo detectors 24. It is made possible to carry out precise focusing even in wavelength multiplexing by using an achromatizing means (achromat lens) which is a combination of concavo-convex lens of different signs in wavelength distribution against the shift of the spot in the direction of an optical axis caused by chromatic aberration in each wavelength in the color made on the optical disk 1. |
