Micro-optic lens for data storage

A new type of microlens for data storage applications that has improved off-axis performance is described. The lens consists of a micro Fresnel pattern on a curved substrate. The radius of the substrate is equal to the focal length of the lens. If the pattern and substrate are thin, the combination satisfies the Abbe sine condition. Therefore, the lens is free of coma. We analyze a 0.5 numerical aperture, 0.50 mm focal length lens in detail. A 0.16 numerical aperture lens was fabricated holographically, and results are presented.