Anthony G. Dewey

Optical recording in the blue using a frequency-doubled diode laser

We have developed a 428 nm blue laser source based on resonator-enhanced frequency doubling of a GaAlAs diode laser and have used this source to demonstrate writing and reading on an MO disk. The power, beam quality, and noise of the blue laser are sufficient for high-density optical recording.

Projection systems for light valves

This paper classifies schlieren projection systems for light valves (LVs) into three groups according to the type of illumination. The requirements for uniform illumination and the tradeoffs between brightness, contrast, and resolution are discussed for different systems. Consideration is given to transmissive versus reflective LVs, black-on-white versus white-on-black, image overlay, color, and luminous efficiency.

Optimizing the noise performance of a magneto-optic read channel

In a magneto-optic head with differential detection, the light level on the data detectors is determined by the ratio of a semi-polarizing beam splitter. This paper presents a way of measuring the various noise sources with a common set of values and uses this data to choose the beam splitter ratio that optimizes the SNR.

Laser-Addressed Liquid Crystal Projection Displays

A summary is given of recent work on laser-addressed smectic liquid crystal projection displays. Details of the cell construction are given along with some considerations on optimizing contrast ratio. Two display demonstrations are described. The first employs a GaAs laser, has 500x500 picture element capacity, and operates at keyboard-entry speeds. The second demonstration uses an argon laser, has 1024x1024 picture elements, two color capability, and can be written in several seconds.

CD-erasable (CD-E) disk technology

CD-ROM has established itself as the preferred medium for the cost-effective distribution of software and various types of multimedia information. The ongoing price reductions of write- once CD-R media and drives are broadening the application range of CD-R from CD- prototyping and small-scale data distribution towards data archiving and bck-up at the desktop. The addition of erasability would increase the attractiveness of recordable CD technology and enable its wide-spread use for personal recording of all types of data files with convenient data interchange. A CD-erasable system (CD-E) with the following characteristics would be very desirable: 1) compatible with existing computer systems and software, 2) erasable with direct overwrite (DOW), 3) recordable using CD-R recorders with minimum modification, 4) readable on CD-ROM players with minimum modification, and 5) reliable. The potential of Ag-In-Sb-Te phase-change materials for CD-E discs and some basic studies have been previously reported by Ricoh. In this paper, we present detailed results of DOW recording on Ricohs CD-E discs at 2.4-2.8 m/s (CD double speed). We conclude that reliable writing and reading as outlined in the concept above can be achieved with this CD-E system.