Abstract

Optical data storage (ODS) lenses are mounted with an automatic refocusing mechanism to account for possible variations in the lens-disk distance, e.g., disk wobble. This auto-focus system, however, cannot compensate for laser mode hopping, which occurs on a nanosecond scale. One possible solution is to use frequency stabilized lasers, but these tend to be very expensive. Another option is to correct the longitudinal chromatic aberration of the lens over the spectral bandwidth of the source. Unfortunately, achromatizing the lens using conventional glass requires a positive and negative element, which significantly increases the size and weight of the lens, neither of which is desirable for optical data storage. An alternative option is the use of gradient index glass, and a fourth possible solution is to use a diffractive/refractive hybrid lens, which is the focus of this paper.

© 1992 Optical Society of America