Reflective Lens Research Articles

Informatics and the Inca

In this paper the term informatics is used as a convenient umbrella term to stand for the overlapping disciplinary areas of information systems, information management and information technology. Much debate has occurred over the last few years surrounding the status of informatics as a discipline. We argue that this debate revolves around the issue of the most appropriate locus for the discipline and that this debate may be informed by a better definition for the central concept of information system. We describe the case of the Inca civilisation, their use of information specialists and a distinct ‘information technology’ and use this as a reflective lens for highlighting the core features of this central concept. What is fascinating about this particular case is that whereas the ‘information system’ described was critical to the effective operation of a large and successful Amer-Indian empire, the ‘information technology’ at its core did not even utilise written language. An examination of this case therefore provides a necessary intellectual distance but also grounding to our discussion of the centrality of the concept of information system to the discipline of informatics.

Comparative Proteomics Analysis of Barrett Metaplasia and Esophageal Adenocarcinoma Using Two-dimensional Liquid Mass Mapping

Esophageal adenocarcinoma, currently the seventh leading cause of cancer-related death, has been associated with the presence of Barrett metaplasia. The malignant potential of Barrett metaplasia is evidenced by ultimate progression of this condition to invasive adenocarcinoma. We utilized liquid phase separation of proteins with chromatofocusing in the first dimension and nonporous reverse phase HPLC in the second dimension followed by ESI-TOF mass spectrometry to identify proteins differentially expressed in six Barrett metaplasia samples as compared with six esophageal adenocarcinoma samples; all six Barrett samples were obtained from the identical six patients from whom we obtained the esophageal adenocarcinoma tissue. Approximately 300 protein bands were detected by mass mappings, and 38 differentially expressed proteins were identified by microLC-MS/MS. The false positive rates of the peptide identifications were evaluated by reversed database searching. Among the proteins that were identified, Rho GDP dissociation inhibitor 2, alpha-enolase, Lamin A/C, and nucleoside-diphosphate kinase A were demonstrated to be up-regulated in both mRNA and protein expression in esophageal adenocarcinomas relative to Barrett metaplasia. Candidate proteins were examined at the mRNA level using high density oligonucleotide microarrays. The cellular expression patterns were verified in both esophageal adenocarcinomas and in Barrett metaplasia by immunohistochemistry. These differentially expressed proteins may have utility as useful candidate markers of esophageal adenocarcinoma.

Thermal performance of a solar oven with augmented sunlight concentration

This paper describes the thermal performance of a novel solar oven that incorporates a compact reflec-tive lens, or ring array, to augment sunlight concen-tration. Performance is reported in terms of the pos-itive effect of the ring array versus a non-concen-trating lid, maximum operating temperature, ther-mal efficiency, performance under partly cloudy skies, and the effects of incidence angle and track-ing. Use of the ring array lens improved thermal efficiency by 4% in the test range up to 100°C, while boosting the maximum operating temperature from 138°C to 196°C. Comparative tests conducted under clear sky conditions against two other com-mercial types showed that when tracked in the azimuth plane at near-normal incidence angles, the new design generated maximum cooking power of 300 W and boiled water at a rate 13% faster than the next best commercial oven tested. Augmented sunlight concentration sensitised the new design to higher angles of incidence and performance was negatively affected in the non-tracked state. Under non-ideal operating conditions, including partial shading by cloud, the oven outperformed both commercial units.

RADAR CROSS-SECTION STUDIES OF SPHERICAL LENS REFLECTORS

The reflectivity of a Spherical Lens Reflector is investigated. The scattering of an electromagnetic plane wave by a Spherical Lens Reflector is treated as a classical boundary value problem for Maxwell’s equations. No restrictions are imposed on the electrical size of reflectors and the angular size of the metallic spherical cap. The competitiveness of the Spherical Lens Reflector against the Luneberg Lens Reflector is demonstrated. It has been found that Spherical Lens Reflectors with relative dielectric constant in the range 3.4 ≤ er ≤ 3.7 possess better spectral performance than 3or 5-layer Luneberg Lens Reflectors in a wide frequency range.

Scattering by a Luneberg Lens Partially Covered by a Metallic Cap

Scattering ofan electromagnetic plane wave by a Luneberg lens with an attached spherical metallic cap at arbitrary incidence angle is analysed using the Electric Field Integral Equation approach. The integral equation is solved numerically via Galerkin's method, using whole-domain basis functions. For verification, the numerical results are compared with the benchmark solution which was developed for normal incidence, and with published measured data. The developed approach is valid for use in the design of a Luneberg Lens Reflector for wide-scan applications.

Electrically switchable and optically rewritable reflective Fresnel zone plate in dye-doped cholesteric liquid crystals

This work demonstrates a reflective Fresnel zone plate based on dye-doped cholesteric liquid crystals (DDCLC) using the photo-induced realignment technique. Illumination of a DDCLC film with a laser beam through a Fresnel-zone-plate mask yields a reflective lens with binary-amplitude structures - planar and focal conic textures, which reflect and scatter probed light, respectively. The formed lens persists without any external disturbance, and its focusing efficiency, analyzed using circularly polarized light, is ~ 23.7%, which almost equals the measured diffraction efficiency of the used Fresnel-zone-plate mask (~ 25.6%). The lens is thermally erasable, rewritable and switchable between focusing and defocusing states, upon application of a voltage.

Ground-plane-backed hemispherical Luneberg-lens reflector

A spherical Luneberg-lens reflector provides excellent passive wideband and wide-angular radar-signature augmentation, and has been widely used. Much of its signature-enhancement performance over half of its angular coverage can potentially be achieved by using a corresponding low-profile, hemispherical Luneberg-lens reflector, mounted on a reflective ground plane. This paper presents a quantitative study of a practical design of an off-the-shelf hemispherical Luneberg-lens reflector to gain insight and to fully explore its performance limits. Extensive wideband and wide-angle measurements were carried out for this lens configuration, and a comprehensive numerical analysis was also conducted, using the finite-element method combined with a boundary integral equation to complement the test data. The effect, in practice, of a finite-sized ground plane, and the resulting vertically polarized traveling-wave interference to the direct lens reflector's return, were demonstrated. Key design issues are discussed, and potential solutions are suggested

Reflective thermal lens detection device

A reflective thermal lens detection device was developed for realizing a portable and sensitive detector for a microsystem. An aluminum mirror was formed on the main plate of a microchip, and a reflected probe beam was detected with a single pick-up unit. The background signal due to light absorption of the aluminum mirror was 60 times reduced when the microchannel and the mirror were separated with an interval of 600 microm. The tilt angle of the microchip significantly affected the precision of the measurement. Then a quadrant photodiode was used to detect the center of gravity of the reflected probe beam to regulate the tilt angle within +/-0.05 degrees , and this value was enough to achieve 1% CV (coefficient of variance) precision in the measurements. The limit of detection (LOD) was 60 nM for xylene cyanol solution, and the absorbance was 9.4 x 10(-6) AU. About 40 times higher sensitivity was obtained in comparison with a spectrophotometer.

A quantitative study of Luneberg-lens reflectors

Luneberg-lens reflectors, which provide passive wideband and wide-angle radar-signature augmentation, have been widely used in small military target drones, decoys, and marine vessels. Due to the difficulty of fabricating inhomogeneous dielectrics with a continuously varying index, Luneberg lenses are usually constructed with multilayered step-index dielectrics. This paper presents a quantitative study of a practical design of a three-layer Luneberg-lens reflector for C- and X-band operations. Extensive wideband and wide-angle measurements were carried out for this lens with three different cap reflectors, as well as for the lens alone without any reflector. A comprehensive numerical analysis, using the finite-element method combined with boundary integral equations, was also conducted. This was done to support the measured data and to provide additional insight for a better understanding of the performance and the limitations of the Luneberg-lens reflector than could be achieved with the traditional ray-optics method. The effect of reflector size is discussed, and the limitation of three-layer design is demonstrated. It has also been shown that very accurate material parameters must be ascertained so as to achieve the level of accuracy commonly desired in the computational electromagnetic codes applied to inhomogeneous dielectrics. The excellent agreement between the numerical and measured data indicates that this full-wave Maxwell solver can be used to explore the design limits and optimize designs for this type of lens reflector.

Tunable reflective lens array based on liquid crystal on silicon

We use a phase modulation method to form tunable lens arrays on liquid crystal on silicon (LCOS). With independent voltage adjustment on each pixel, LCOS generates a high-resolution gradual phase modulation profile, which makes it possible for the lens array to be freely tunable in focal length and other parameters. A tunable lens array is made on LCOS by use of this method, and we provide details of the theoretical analyses and experimental results.

A high-efficiency in-plane splitting coupler for planar photonic Crystal self-collimation devices

In this letter, we present the design, fabrication, and characterization of a high-efficiency in-plane splitting coupler for planar photonic crystal self-collimation devices. This splitting coupler consists of multiple concatenated in-plane reflective lenses and is capable of efficiently splitting and coupling a wide input beam into multiple narrow self-collimated beams. As an example, a one-to-two splitting coupler is simulated using the two-dimensional finite-difference time-domain method with an effective index used to account for the third dimension. The simulation shows a total coupling efficiency of 86% and a splitting ratio of two channels is 0.51 to 0.49. This device is also experimentally validated and the measured splitting ratio is 0.57 to 0.43.

Junkspace: Theology after Monumentality

This article addresses Dutch architect Rem Koolhaas's notion of ‘Junkspace’ Š infinitely reconfigurable, physical space that is always-already in transition, perpetually in a state of becoming Š and its implications for theology. Junkspace is the logical result of a culture in which ‘shopping’ is the last public activity. All public institutions Š churches, museums, the internet, hospitals, universities and airports Š increasingly are drawn into this framework. While this schema represents the suburban desire for control and predictability, it consequently flattens intellectual terrain. In other words, we have come to the point of shopping for politics, knowledge, ideology and theology. Rather than critique this hypothesis, the article explores its possibilities for new understandings of the secular, our desire for ‘the new’, and our need to intentionally forget or disavow. I argue that Junkspace may serve as a promising new metaphorical lens for theological reflection, which is now rendered provisional, incomplete, and migratory.

The promise of diffractive optics in maskless lithography

For photon-based maskless lithography, a system based on the incoherent addition of scanned, multiplexed, on-axis focal spots from an array of diffractive-optical elements, such as binary-phase zone plates, has advantages over systems based on partially coherent projection of the image of a micromechanical mirror array through a large refractive or reflective lens. We have fabricated binary-phase zone-plate arrays with numerical apertures up to 0.9 with near-ideal performance, and used them to achieve high quality lithography of arbitrary patterns. Using a wavelength of 400 nm we achieve k 1 factors as low as 0.32, without the use of any resolution enhancement techniques. Sufficient contrast is achieved in dense patterns despite the presence of diffracted orders other than +1. Advantages of our diffractive-optical approach include: the feasibility of wavefront engineering by using elements other than binary-phase zone plates; the simplicity of the planar processes needed to manufacture large arrays of high-NA diffractive-optical elements; and the ease of wavelength scaling, with the promise of ultimately approaching the limits of the lithographic process.

The promise of diffractive optics in maskless lithography

For photon-based maskless lithography, a system based on the incoherent addition of scanned, multiplexed, on-axis focal spots from an array of diffractive-optical elements, such as binary-phase zone plates, has advantages over systems based on partially coherent projection of the image of a micromechanical mirror array through a large refractive or reflective lens. We have fabricated binary-phase zone-plate arrays with numerical apertures up to 0.9 with near-ideal performance, and used them to achieve high quality lithography of arbitrary patterns. Using a wavelength of 400 nm we achieve k 1 factors as low as 0.32, without the use of any resolution enhancement techniques. Sufficient contrast is achieved in dense patterns despite the presence of diffracted orders other than +1. Advantages of our diffractive-optical approach include: the feasibility of wavefront engineering by using elements other than binary-phase zone plates; the simplicity of the planar processes needed to manufacture large arrays of high-NA diffractive-optical elements; and the ease of wavelength scaling, with the promise of ultimately approaching the limits of the lithographic process.

Numerical study of polarization‐dependent focusing for a bilayer planar FSS reflective lens at millimeter wavelengths

AbstractIn this paper, we numerically analyze the polarization‐dependent focusing properties of a planar reflective lens formed by two parallel layers of nonuniform “gangbuster” surfaces (GSs) above a ground plane. Since these GSs consist of superdense arrays of thin finite‐length parallel metallic wires, the desired phase patterns on such a lens surface are achieved by adjusting the lengths of these metallic wires for appropriate polarization components. In our analysis, we use the method of moments (MoM) and the transmission‐lines analogy, along with the surface‐equivalence theorem, to estimate the field intensity in the focal plane. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 361–365, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11382

Focus on Laboratory Equipment

Focus on Laboratory Equipment

The case for diffractive optics in maskless lithography

For photon-based maskless lithography we show that a system based on the incoherent addition of scanned, multiplexed, and on-axis focal spots from an array of diffractive-optical elements, such as binary-phase zone plates, has significant advantages over systems based on partially coherent projection of the image of a micromechanical mirror array through a large refractive or reflective lens. We show that zone-plate arrays with numerical apertures up to 0.9 can be manufactured with near-ideal performance, and used to achieve high-quality lithography of arbitrary patterns. Using a wavelength of 400 nm we demonstrate k1 factors as low as 0.32, without the use of any resolution-enhancement techniques; that sufficient contrast is achieved in dense patterns despite the presence of diffracted orders other than +1; and that a process-latitude greater than 10% is achieved for 150 nm lines and spaces. Advantages of our diffractive-optical approach include: the feasibility of wave-front engineering by using elements other than binary-phase zone plates; the simplicity of the processes needed to manufacture large arrays of high-numerical-aperture diffractive-optical elements; and the ease of wavelength scaling, with the promise of ultimately approaching the limits of the lithographic process.

Passive millimetre-wave imaging architectures

This paper discusses various passive millimetre-wave imaging systems. It includes sources of radiation, atmospheric transmission and a brief summary of their various applications. This is followed by a review of methods for detecting millimetre-wave radiation. From a cost analysis it is shown that scanned systems are at present far more cost effective than focal plane array of receivers for high-performance systems. Then various types of imaging system available are considered with greater emphasis on recent developments and their methods of beam forming. It is concluded that at present, and for the foreseeable future, optical beam forming and beam steering are the most cost-effective solutions. Some general remarks are included as to how receivers are matched to their collection apertures, followed by a section on optical beam-forming components. The recent development of a lightweight, low-cost, high-performance reflective lens is included. It is then shown how this may be combined with mechanical scanning systems to form high-performance passive millimetre-wave imaging systems.

Looking Back Together: Phenomenology and Nurturing the Reflective Lens in Student Writing

Looking Back Together: Phenomenology and Nurturing the Reflective Lens in Student Writing

Helping People Through Use of Theories

Many human service and vocational guidance practitioners are so busy they have little time to reflect on their work with clients, and on the clients and their situations. Yet reflection and study and analysis is more important now than ever to be helpful, especially in such arenas as counseling, vocational guidance and job placement. A variety of theories can be used as reflective lenses, to enable practitioners to understand clients and behavior, and then intervene appropriately. Several theories are briefly presented as suggestive examples. The author recommends use of a list or collection of theoretical materials, adjacent to their workplace settings, for guidance and human service professionals and paraprofessionals.