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Ring-toric lens for focus-error sensing in optical data storage.

M R Descour¹, D I Simon, W H Yeh

¹Optical Sciences Center, University of Arizona, Tucson, Arizona 85721, USA. michael.descour@opt-sci.arizona.edu

|February 29, 2008

Summary

New diffractive ring-toric lenses offer improved focus-error sensing for optical data storage. These lenses provide higher sensitivity to disk defocus, enhancing data retrieval accuracy.

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Area of Science:

Optics
Optical Engineering
Data Storage Technology

Background:

Accurate focus-error sensing is crucial for reliable data retrieval in optical storage systems.
Existing methods like astigmatic and obscuration techniques have limitations in sensitivity and performance.
Diffractive optical elements offer potential for novel sensing solutions.

Purpose of the Study:

To design and evaluate the performance of novel diffractive ring-toric lenses for focus-error sensing.
To compare the sensitivity of ring-toric lenses against established focus-error sensing methods.
To demonstrate the practical application of these lenses in optical data storage.

Main Methods:

Design of diffractive ring-toric lenses to image a point source into a ring-shaped image.

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Implementation of a segmented phi detector to generate a focus-error signal (FES).

Measurement of the FES slope as an indicator of sensitivity to disk defocus.

Main Results:

Ring-toric lenses successfully generate a ring-shaped image, with radius changes indicating focus error.
The FES slope for ring-toric lenses was measured at 0.7 per micrometer (µm⁻¹).
This measured FES slope is significantly higher than those achieved with astigmatic and obscuration methods.

Conclusions:

Diffractive ring-toric lenses represent an effective and highly sensitive solution for focus-error sensing.
The enhanced sensitivity of these lenses can improve the accuracy and reliability of optical data storage systems.
Further development could lead to widespread adoption in next-generation optical storage devices.