Optical Disc Systems

Several types of laser-readable disc systems have emerged since the first demonstration of the Laser Vision optical video disc in 1972 At present there are three main categories  

Laser Vision video discs, diameter 30 cm, playable on two sides and containing analog video and audio information 

Compact Disc (CD) audio discs, diameter 12 cm, playable on one side and 

Several types of Direct Read After Write (DRAW) discs on which data can be digitally recorded either once (write-once) or repeatedly (erasable). Initial applications are largely in professional equipment, for example as storage systems for large archieves. 

Most systems make use of a relief structure consisting of small pits, arranged in circular or spiral tracks. 

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G. Bouwhuis, Prindples of Optical Disc Systems, Adam Hdgei, Bristol, U.K, 1985. 

Bouwhuis, G., Ed., Principles of Optical Disc Systems, Adam Hilger, Bristol, 1985. Makrolon CD2005 and DPl-1265 on plastics.bayer.com, 1997. 

Sabi Y, Yamamoto M, Watanabe H, Bieringer T, Haarer D, Hagen R, Kostromine SG, Berneth H. 2001. Photoaddressable polymers for rewritable optical disc systems. Jpn J Appl Phys 40 1613 1618. 

Principles of Optical Disc. Systems , G. Bouwhuis, Editor, Adam Hilger Ltd., Bristol 1985... 

Phase quadrature is an over-arching concept for all interferometric detection. However, achieving a common-path configuration that locks in a stable quadrature condition puts constraints on possible system designs. This section reviews the several configurations of common-path quadrature that have been demonstrated so far in spinning-disc systems. These are the micro-diffraction class, the adaptive optical class, the phase contrast and the in-line class. At the end of this section, we show that the phase-contrast and in-line classes are conjugate quadratures of each other. 

Rotating optical disk systems were first demonstrated in the 1960s and paved the way for the Philips Videodisc, introduced in 1973. Less than ten years later, following the successful development of the reliable, low-cost gallium-arsenide laser, the compact disc was launched, leading to the first penetration of laser technology into the consumer market. 

R M 2000, the Air Force Reliability and Maintainability Action Plan does not discuss the unique problems (and potential) of expert systems, particularly those which rely on the massive "knowledge bases" which can now be delivered on optical disc. Nor have they addressed the problems (and potential) associated with parallel processing, neural networks and "systems that learn". 

Peroxide hazard classification expert systems development at FM/Norwood is presently on hold until some of the resources noted become available. We have a way to go before a fully validated classification model is complete. At the same time, we are continuing to explore the possibility of using chemical database programs such as those available from Molecular Design Inc. and the University of Santiago, Chile (ARIUSA) as components of our chemical hazard expert systems. We are also looking at chemical databases on optical disc such as those available from DuPont, Aldrich, Micromedix and the Canadian Center for Occupational Safety and Health as components of future systems. 

Combinations of portable microcomputers, optical disc/card knowledge bases, expert systems technology, natural language processing and machine translation will have a major impact on the way we do business in the future. 

Fig. 8.7 Scheme of automatic centrifugal analyser. Analyser module (a) location of the transfer disc (b) the transfer of the reaction mixture takes place during centrifugation (c) optical detection system on a single, fixed point. 

Fig. 8.8 Scheme of the Technicon RA-100 analyser, (a) Sample, reagent and reaction discs, with two intermediate liquid transfer systems (d) optical detection system. (Courtesy of Technicon). 

On-Rotor on-Disc-Based Optical Detection Systems... 

Optical Detection on Centrifugal Microfluidic Lab-on-a-Disc Platforms, Fig. 2 Portable, lab-on-a-disc-based ELISA system with an absorbance optical detection system [6]. (a) Photograph and (b) schematic of the blood analyzer system. A detector module is installed to perform absorbance detection, (c) Top and bottom plate of the disc... 

Sensory systems Vision A 54-year-old male kidney transplant patient developed bilateral ischemic optic neuropathy while taking tacrolimus [143 ]. The right fundus was normal, but there was temporal pallor of the left optic disc. A Goldmann visual field test showed cecocentral scotoma with an inferior predilection in both eyes. Fluorescein angiography showed no fluorescence filling the optic disc in either eye, from the early phase to the late phase, which suggests absolute absence of blood flow to the optic disc. Visual acuity improved partially after withdrawal of tacrolimus. 

Shaft speed and torque, measured by a shaft mounted optical slitted disc system, providing filtered analogue voltage outputs. 

Sensory systems Vision A patient with ocular sarcoidosis developed reduced vision with optic disc hyperemia after long-term treatment with linezolid for osteomyelitis. Vision improved and the hyperemia disappeared after linezolid withdrawal [150 ]. 

Nervous system Bilateral anterior optic neuropathy has been reported in an otherwise healthy 43-year-old man who took terbinafine 500 mg/day for onychomycosis [1" ]. Terbinafine was withdrawn and his visual acuity improved considerably within 1 month, but there was slight pallor of the left optic disc and the visual fields of both eyes were still concentrically constricted. One plausible explanation for this effect of terbinafine may be that it is amphiphilic, which may allow binding to polar lipids and accumulation within lysosomes. Drug-induced lysosomal impairment has been presumed to be the basis of the retinal changes observed with other amphiphilic drugs, such as amiodarone, perhexilene, and suramin. 

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