Roland Winston

Bio: Roland Winston is an academic researcher from University of California, Merced. The author has contributed to research in topics: Nonimaging optics & Concentrator. The author has an hindex of 55, co-authored 473 publications receiving 13911 citations. Previous affiliations of Roland Winston include University of California & Philips.

High collection nonimaging optics

Abstract: Nonimaging optics departs from the methods of traditional optical design to develop instead techniques for maximizing the collecting power of concentrating elements and systems. Designs which exceed the concentration attainable with focusing techniques by factors of four or more and approach the theoretical limit are possible (ideal concentrators). The methodology for designing high collection nonirnaging systems is described.

Principles of solar concentrators of a novel design

Abstract: A new principle for collecting and concentrating solar energy, the ideal cylindrical light collector, has been invented. This development has its origins in detecting Cherenkov radiation in high energy physics experiments. In its present form, the collector is a trough-like reflecting wall light channel of a specific shape which concentrates radiant energy by the maximum amount allowed by phase space conservation. The ideal cylindrical light collector is capable of accepting solar radiation over an average ∼8-hr day and concentrating it by a factor of ∼10 without diurnal tracking of the sun. This is not possible by conventional imaging techniques. The ideal collector is non-imaging and possesses an effective relative aperture (f-number) =0·5. This collector has a larger acceptance for diffuse light than concentrating collectors using imaging optics. In fact, the efficiency for collecting and concentrating isotropic radiation, in comparison with a flat plate collector, is just the reciprocal of the concentration factor.

Light Collection within the Framework of Geometrical Optics

Abstract: The problem of light collection is examined from first principles within the framework of geometrical optics. From the outset, we distinguish between light collection and the usual theory of image formation. From phase-space considerations, we derive the sine inequality, a generalization of the Abbe sine law appropriate to nonimaging systems. We construct two- and three-dimensional nonimaging systems that reduce the f number to the least allowed by the sine inequality. Such systems give substantially improved light collection as compared with conventional systems.

Wireless Infrared Communications

Abstract: The use of infrared radiation as a medium for high-speed short-range wireless digital communication is discussed. Available infrared links and local-area networks are described. Advantages and drawbacks of the infrared medium are compared to those of radio and microwave media. The physical characteristics of infrared channels using intensity modulation with direct detection (IM/DD) are presented including path losses and multipath responses. Natural and artificial ambient infrared noise sources are characterized. Strategies for designs of transmitter and receivers that maximize link signal-to-noise ratio (SNR) are described. Several modification formats are discussed in detail, including on-off keying (OOK) pulse-position modulation (PPM), and subcarrier modulation. The performance of these techniques in the presence of multipath distortion is quantified. Techniques for multiplexing the transmissions of different users are reviewed. The performance of an experimental 50-Mb/s on-off-keyed diffuse infrared link is described.

Small molecular weight organic thin-film photodetectors and solar cells

Abstract: In this review, we discuss the physics underlying the operation of single and multiple heterojunction, vacuum-deposited organic solar cells based on small molecular weight thin films. For single heterojunction cells, we find that the need for direct contact between the deposited electrode and the active organics leads to quenching of excitons. An improved device architecture, the double heterojunction, is shown to confine excitons within the active layers, allowing substantially higher internal efficiencies to be achieved. A full optical and electrical analysis of the double heterostructure architecture leads to optimal cell design as a function of the optical properties and exciton diffusion lengths of the photoactive materials. Combining the double heterostructure with novel light trapping schemes, devices with external efficiencies approaching their internal efficiency are obtained. When applied to an organic photovoltaic cell with a power conversion efficiency of 1.0%±0.1% under 1 sun AM1.5 illuminati...