ELECTROOPTIC FOCUSING SYSTEM FOR A HIGH-DENSITY OPTICAL DISK

We have developed an electro-optic cell as a fine-adjustment focusing system for an optical disk. The cell is fabricated from transparent le ad lanthanum zirconate titanate ceramic and has concentric-patterned i ndium tin oxide electrodes. The electro-optic cell can generate a rela tive phase shift in the pupil function. We have confirmed, theoretical ly and experimentally, that the phase shift induces a change in focal position that is as much as twice the focal depth without degrading th e region near the main lobe of the point-spread function.