Design approaches with a lenslet array and a single, high-numerical-aperture annular-field objective lens for optical data storage systems that incorporate large numbers of parallel read-write-erase channels

To achieve very high data rates (>10(9) bits/s) in optical data storage systems it is necessary to employ a large number of laser beams for parallel read-write-erase operations. Bringing all these beams to diffraction-limited focus with a high-numerical-aperture objective lens (while maintaining focus and tracking) requires techniques that are fundamentally different from those that are currently practiced in the field of optical data storage. We present two possible solutions to the problem of designing an objective lens for such systems, one involving an array of high-quality lenslets and the other based on a single, high-numerical-aperture annular-field-of-view conventional lens. Both approaches have advantages and disadvantages, on which we elaborate in the course of our discussions.