Abstract

We discuss the design and performance of diffractive ring-toric lenses for focus-error sensing in optical data storage. A ring-toric lens images a point source of light to a ring-shaped image. Focus-error sensing is accomplished by means of monitoring the change in ring radius: The ring expands in response to a diverging wave front, and the ring contracts in response to a converging wave front. We describe the use of a segmented phi detector to generate a focus-error signal (FES). We found that the FES slope, a measure of sensitivity to disk defocus, is higher for the ring-toric lenses described in this paper than for other techniques such as the astigmatic and the obscuration methods. We measured an FES slope of 0.7 per micrometer of disk defocus (µm^-1). The corresponding theoretical FES slope is 0.96 µm^-1.

© 1999 Optical Society of America

Ring-lens focusing and push-pull tracking scheme for optical disk systems

James J. Zambuto, Ronald E. Gerber, J. Kevin Erwin, and M. Mansuripur
Appl. Opt. 33(34) 7987-7994 (1994)

Causes of focus-error feedthrough in optical-disk systems: astigmatic and obscuration methods

Bruce E. Bernacki and M. Mansuripur
Appl. Opt. 33(5) 735-743 (1994)

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

José M. Sasián and Masud Mansuripur
Appl. Opt. 38(7) 1163-1168 (1999)

Characterization of a novel focusing/tracking technique with increased feedthrough immunity for optical-disk applications: the double-astigmatic method

Bruce E. Bernacki, Keith Bates, M. Mansuripur, Delbert Hansen, and Daniel Cisneros
Appl. Opt. 32(29) 5789-5796 (1993)

Evaluation of partial-response maximum-likelihood detection for phase-change optical data storage

Chubing Peng and M. Mansuripur
Appl. Opt. 38(20) 4394-4405 (1999)