OPTICAL ELEMENT FOR OPTICAL DISK AND OPTICAL HEAD USING THE SAME

摘要

PURPOSE:To correct aberration occurring in an optical disk substrate with a different thickness. CONSTITUTION:An optical element 7 with an aspherical surface and without power is inserted into parallel luminous flux so as to cancel the aberration occurring due to the difference of the disk thickness. Then, the aberration occurring due to the difference of the disk thickness is corrected completely without shortening an operation distance unnecessarily. That is, a spot within a diffraction limit is obtained even for the optical disk with a different thickness.