LCD Diffractive Element Design to Handle Multiple Disk Thicknesses
Abstract
We describe the design of a single diffractive LCD element placed adjacent to the objective lens that can be addressed to provide the required spherical aberration (SA) compensation for a plurality of disk substrate thicknesses. It is now commonplace that optical disk drives must be able to handle disks of more than one substrate thickness. The major problem is compensating for the SA introduced when the highly corrected objective lens is used with a disk substrate thickness other than that which it was specifically designed for. An abundance of methods for solving this problem in the specific case of CD/DVD backward compatibility exist in the literature; we use an active device to extend this to include HD-DVD as well. The LCD element acts as a switchable diffractive optical element. A set of electrodes defines the circular grating features that can be switched on or off to create diffractive lenses of the desired set of focal lengths. The liquid crystal modulates the phase and amplitude of the transmitted light according to the electrode pattern. We examine various approaches for the electrode layout that can implement 2-level, multi-level and continuous phase gratings in the LCD element. Two designs for the LCD wavefront compensator are presented that provide backward compatibility with DVD and CD formats from an HD-DVD system.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2000
- Accession Number
- ADP011862
Entities
People
- Hsi P. Shih
- Jau J. Ju
- Mark O. Freeman
- Yuan C. Lee
Organizations
- Industrial Technology Research Institute