Abstract

Recently, high density optical disk systems employing 0.6mm substrate thickness, such as Digital Versatile Disk (DVD), have been standardized. In these systems, compatibility with conventional optical disk systems employing 1.2mm substrate thickness, such as Compact Disc (CD), is strongly required. In case of reading a 0.6mm disk and a 1.2mm disk using the same optical head, it is necessary to compensate for the spherical aberration due to different substrate thickness. Several kinds of optical heads have been reported for this purpose, such as a dual focus type¹⁾, a twin lens type²⁾, and a variable aperture type³⁾.

© 1996 Optical Society of America