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Purpose: Evaluating the impact of splitting toric power on patient tolerance to misorientation such as with intraocular lens rotation. Setting: University vision clinic. Methods: Healthy, non astigmats had +1.50D astigmatism induced with spectacle lenses at 90°, 135°, 180° and +3.00D at 90°. Two correcting cylindrical lenses of the opposite sign and half the power each were subsequently added to the trial frame misaligned by 0°, 5° or 10° in a random order and misorientated from the initial axis in a clockwise direction by up to 15° in 5° steps. A second group of adapted astigmats with between 1.00 and 3.00DC had their astigmatism corrected with two toric spectacle lenses of half the power separated by 0°, 5° or 10° and misorientated from the initial axis in both directions by up to 15° in 5° steps. Distance, high contrast visual acuity was measured using a computerised test chart at each lens misalignment and misorientation. Results: Misorientation of the split toric lenses caused a statistically significant drop in visual acuity (F =70.341; p <0.001). Comparatively better acuities were observed around 180°, as anticipated (F =3.775; p =0.035). Misaligning the split toric power produced no benefit in visual acuity retention with axis misorientation when subjects had astigmatism induced with a low (F =2.190, p =0.129) or high cylinder (F =0.491, p =0.617) or in the adapted astigmats (F =0.120, p =0.887). Conclusion: Misalignment of toric lens power split across the front and back lens surfaces had no beneficial effect on distance visual acuity, but also no negative effect. [ABSTRACT FROM AUTHOR]

Abstract: We propose a variational-difference method for designing the optical free form surface of progressive-addition lenses (PALs). The PAL, which has a front surface with three important zones including the far-view, near-view and intermediate zones, is often used to remedy presbyopia by distributing optical powers of the three zones progressively and smoothly. The problem for designing PALs could be viewed as a functional minimization problem. Compared with the existing literature which solved the problem by the B-spline finite element method, the essence of the proposed variational-difference numerical method lies in minimizing the functional directly by finite difference method and/or numerical quadratures rather than in approximating the solution of the corresponding Euler–Lagrange equation to the functional. It is very easily understood and implemented by optical engineers, and the numerical results indicate that it can produce satisfactory designs for optical engineers in several seconds. We believe that our method can be a powerful candidate tool for designing various specifications of PALs. [Copyright &y& Elsevier]

We study on the negative and positive effect of surface roughness and loss coefficient on subwavelength imaging of the superlens structure. It has been found that even though surface roughness enables more transmission of high spatial frequency components, the random interferential noise between neighborhood images becomes more severe with increasing distortion. We show that additional loss is able to restrain the interferential noise caused by random roughness while preserving the imaging integrity. The results with practical parameters prove that the mean contrast and uniformity are improved by adding adequate loss on rough surface. Moreover, other two situations are further studied: (a) a single superlens with roughness on different interfaces and (b) a multilayered alternated metal-dielectric superlens with roughness on each surface. We found that the roughness on the imaging surface (metal-photoresist interface) plays a major role in determining the superlens imaging. The multilayer superlens is able to enhance the subwavelength imaging with fractionalized thinner films. But with the further fractionizing layers, the multilayer becomes more vulnerable to the roughness due to the multiple mixing and distorting. We still prove that additional loss is able to improve the performance in both situations. [ABSTRACT FROM AUTHOR]

Background: The accuracy of the Holladay 2 (H2) formula is well-documented. This formula requires seven variables to estimate effective lens position (ELP) for the IOL power calculation. The lens thickness (LT) value is one of the required variables. Interestingly, the IOLMaster, which is one of the most commonly used optical biometers, can provide all the required ocular variables except LT value. It has become a pertinent issue to evaluate the accuracy of theH2 formula when it is used without the LT value. The purpose of this study was to evaluate the results when using the H2 formula, without the LT value, and compare such results to those obtained using the Haigis formula and the Hoffer Q formula. Methods: The Institutional review board (IRB) gave their approval for the conduct of this prospective comparative study. One hundred and sixty-three eyes of 143 cataract patients from the Ophthalmology Department, Siriraj Hospital, Thailand were recruited. All eyes were measured using the IOLMaster (Carl Zeiss Meditec, Jena, Germany) for keratometry (K), axial length (AL), anterior chamber depth (ACD), and horizontal white-to-white (WTW) corneal diameter. Then, the LT measurement was obtained by A-scan ultrasonography (Quantel Axis-II, Quantel Medical, USA). Every patient underwent uncomplicated phacoemulsification by a single surgeon (NC) with a single technique using a single IOL model. Post-operative refraction was obtained at 3 months. The mean absolute errors (MAEs), median absolute errors (MedAEs) and percentage of the eyes within ±0.25, ±0.50, and ±1.00 D of predicted refraction was calculated for H2 formula both with and without LT input, Haigis, and Hoffer Q formula. The results were also classified into a group of short AL (<22.0 mm), average AL (22.0 to 24.5 mm) and long AL (>24.5 mm). Results: There was no statistically significant difference in either MAEs or MedAEs of all formulas in all AL groups including the H2 with and without LT. There was a trend toward lower MAEs and MedAEs for H2 in the long AL group. Percentage of the eyes within ±0.25, ±0.50, and ±1.00 D of predicted refraction were similar in all AL groups. Conclusion: The preliminary results of this study showed that the H2 formula performed well even without the LT value. It was comparable to the Haigis and Hoffer Q formulas. [ABSTRACT FROM AUTHOR]

We have designed and characterized a new inlet and aerodynamic lens for the Aerodyne aerosol mass spectrometer (AMS) that transmits particles between 80 nm and more than 3 μm in vacuum aerodynamic diameter. The design of the inlet and lens was optimized with computational fluid dynamics (CFD) modeling of particle trajectories. Major changes include a redesigned critical orifice holder and valve assembly, addition of a relaxation chamber behind the critical orifice, and a higher lens operating pressure. The transmission efficiency of the new inlet and lens was characterized experimentally with size-selected particles. Experimental measurements are in good agreement with the calculated transmission efficiency [ABSTRACT FROM AUTHOR]

Purpose: To study the microanatomic edge structures of anterior lens capsule specimens derived from manual and femtosecond laser–assisted capsulotomies. Setting: Department of Ophthalmology, Goethe-University, Frankfurt, Germany. Design: Experimental study. Methods: Of 60 eyes with lens removal and intraocular lens implantation, 30 received a manual capsulotomy and 30 received a femtosecond laser–assisted capsulotomy (Lensx, rigid curved interface, pulse energy 15 μJ, spot separation 4 μm, layer separation 3 μm). After anterior capsule removal, tissues were immediately fixed in 4.5% formalin. Approximately 30 minutes after fixation, the tissues were removed from the fixation containers and air dried for at least 2 hours. Fifteen capsules in each group had further staining for light microscopy (LM). The surface of the capsulotomy edge was the primary focus of LM and scanning electron microscopy (SEM). Cell configuration, capsule shape, and abnormalities were evaluated. Results: Subjective LM and SEM analysis showed smooth edges at all magnifications, no cell destruction, and cells up to the cutting edge in the manual capsulotomy group. Light microscopy demonstrated almost continuous anterior capsule incisions of the femtosecond laser–assisted capsulotomy, a prominent demarcation line along the cutting edge, and several tags and bridges. Scanning electron microscopy showed microgrooves and valley- and mountain-like structures as signs of the photodisruption process. Conclusion: Compared with manual procedures, curved, rigid interface femtosecond laser–assisted capsulotomy specimens using 15 μJ pulse energy showed tags, bridges, rougher edges, and demarcation lines on the capsulotomy edges on SEM but subjectively estimated a more round shape on LM. Financial Disclosures: Mr. Klaproth received travel reimbursements and/or lecture fees from Alcon Laboratories, Inc., Rayner Intraocular Lenses Ltd., and Oculus GmbH. Dr. Kohnen received travel reimbursements, grant support, and/or lecture fees from Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Bausch & Lomb, Carl Zeiss Meditec AG, Neoptics AG, Rayner Intraocular Lenses Ltd., and Schwind eye-tech-solutions GmbH and Co. KG; he is a consultant to Alcon Laboratories, Inc., Carl Zeiss Meditec AG, Rayner Intraocular Lenses Ltd., and Schwind eye-tech-solutions GmbH and Co. KG. No other author has a financial or proprietary interest in any material or method mentioned. [Copyright &y& Elsevier]

Purpose: To evaluate whether postoperative refractive power adjustment of a light-adjustable lens (LAL; Calhoun Vision, Inc, Pasadena, CA) improves refractive outcomes in patients who have undergone prior LASIK or photorefractive keratectomy. Design: Retrospective case series. Participants: Thirty-four eyes in 21 cataract patients with a mean age of 62.6±9.7 years and a history of myopic corneal refractive surgery were implanted with the LAL during cataract surgery performed at a single clinic in Victoria, Canada. Methods: Two weeks after uncomplicated cataract surgery, we used a light delivery device to deliver a spatially resolved 365-nm beam of ultraviolet light to alter the shape of the LAL and hence its refractive power. To obtain the desired refractive change, 1, 2, or 3 adjustments were used. After adjustments, we applied 2 lock-in treatments to the LAL to consume unpolymerized macromeres in the LAL. The final manifest refraction spherical equivalent (MRSE) achieved then was compared with the initial refractive target before LAL implantation. Main Outcome Measures: The MRSE to target refraction, mean absolute error of cohort to target refraction, and percentage of cohort within ±0.25 diopters (D), ±0.50 D, ±1.0 D, and more than ±1.0 D relative to target refraction. Results: The MRSE relative to target refraction after final lock-in was within ±0.25 D in 74% of eyes, within ±0.50 D in 97% of eyes, and within ±1.00 D in 100% of eyes. Mean absolute error was 0.19 D with a standard deviation of ±0.20 D. Conclusions: In patients with a history of laser refractive surgery, LAL implantation and postimplantation adjustment provide a precise refractive outcome. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. [ABSTRACT FROM AUTHOR]

We propose a planar polymeric liquid crystal (LC) lens with a low cell gap (\sim4.6~\mum) for a 2-D/3-D switchable auto-stereoscopic display. The proposed lens consists of two LC layers, one is a photopolymerized LC lens layer with a non-uniform refractive index with parabolic curve distribution, and the other is a half-wave LC switching layer of the vertical alignment type, which performs the 2-D/3-D image switching. The optimized refractive index of the LC lens layer was simply realized by polymerizing the LC molecules using a reactive mesogen. The proposed LC lens allow fast 2-D/3-D switching with low voltage and a simple fabrication process because of a low cell gap of the switching layer. We verified the electro-optical characteristics of the proposed LC lens by fabricating each layer after optimizing the cell structure. The measured focal length as a function of the applied voltage in the 3-D mode was compared with the calculated focal length and we confirmed that the measured results agreed with the calculated results. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of reducing the number of visual acuity measurements made in a defocus curve on the quality of data quantified. Setting: Midland Eye, Solihull, United Kingdom. Design: Evaluation of a technique. Methods: Defocus curves were constructed by measuring visual acuity on a distance logMAR letter chart, randomizing the test letters between lens presentations. The lens powers evaluated ranged between +1.50 diopters (D) and −5.00 D in 0.50 D steps, which were also presented in a randomized order. Defocus curves were measured binocularly with the Tecnis diffractive, Rezoom refractive, Lentis rotationally asymmetric segmented (+3.00 D addition [add]), and Finevision trifocal multifocal intraocular lenses (IOLs) implanted bilaterally, and also for the diffractive IOL and refractive or rotationally asymmetric segmented (+3.00 D and +1.50 D adds) multifocal IOLs implanted contralaterally. Relative and absolute range of clear-focus metrics and area metrics were calculated for curves fitted using 0.50 D, 1.00 D, and 1.50 D steps and a near add-specific profile (ie, distance, half the near add, and the full near-add powers). Results: A significant difference in simulated results was found in at least 1 of the relative or absolute range of clear-focus or area metrics for each of the multifocal designs examined when the defocus-curve step size was increased (P<.05). Conclusion: Faster methods of capturing defocus curves from multifocal IOL designs appear to distort the metric results and are therefore not valid. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. [ABSTRACT FROM AUTHOR]

In this study, a procedure for optimization of an LED lens module design based on 3 LED light sources was divided into two phases. For preliminary optimization of the dimensions of the LED lens module in Stage I, an optical analysis with orthogonal arrays and TracePro (an optical design package) combined with analysis of variance was conducted to investigate relationships between the multiple optical quality characteristics (viewing angle and average illuminance) and dimension parameters and find the initial optimal parameter combination of the LED lens module. In Stage II, the initial optimal parameter combination determined in Stage I was employed to develop an orthogonal array L(5) for optical simulation. The experimental data of the orthogonal array were used to train and test the back-propagation neural network to develop an optical quality predictor, which was integrated into the genetic algorithms and the particle swarm optimization in order to find the optimal parameter combination that conformed to optical quality. From the experimental results, the proposed optimization procedure contributes to a precise viewing angle to achieve the goal of optical quality and improved the average illuminance in development of the product. The procedure to optimize the optical design developed in this study can be applied to design all types of LED lens modules and improve the optical design and technology of the LED lens industry. [ABSTRACT FROM AUTHOR]

The article discusses Dutch Jewish philosopher Benedictus de Spinoza, focusing particularly on his interest and career in optics making instruments such as telescopes, microscopes, and magnifying glasses. An overview of optical theory and the importance of improvements in optical technologies to seventeenth-century science is presented. Efforts by Dutch astronomer Christiaan Huygens to create his own lenses are considered. Spinoza's interest in optics is compared to that of Italian astronomer and mathematician Galileo Galilei.

The article discusses the history of the Buffalo, New York, microscope lens manufacturing company Spencer Lens Company. The author begins by providing biographical information on company-founder Charles Achilles Spencer and explaining his development of high-resolution microscope lenses and the Horizontal Monocular Compound Microscope. Surgeon and microscopist Roswell Park's involvement in the business management of the company beginning in 1895 is detailed, as is the work of subsequent company president Harvey N. Ott in the mechanization of lens production at the company.

To meet today's demanding requirements for increased performance, reduced size, lower mass, and cost, simple lenses containing multiple aspheric surfaces are required. It is now common for the number of aspheric surfaces used in an infrared lens to exceed the actual number of lens elements. Multiple aspheric and diffractive surfaces provide additional degrees of freedom in the lens design. This is required to achieve increased levels of imaging performance demanded by reduced pitch detectors. Aspheric surfaces also enable a greater diversity of materials to be used such that athermal solutions can be realized without the need for additional lens elements. More recent advances in detector technology will demand multispectral operation, but the requirements for simple, inexpensive optics will remain. Innovative use of aspheric components can also create very simple multispectral optics to fulfil this emerging need. This paper will review the range of applications that can be satisfied using no more than two optical components, highlighting the specific benefits that aspheric and diffractive surfaces provide. Consideration will also be given to future developments where enhanced functionality can be achieved using computational imaging techniques. Examples will be given for several military applications including weapon sights, driver's vision enhancement and remote weapon stations. [ABSTRACT FROM AUTHOR]

This paper describes a process for designing a faceted freeform Fresnel lens. Where a traditional Fresnel lens uses a profile revolved around a central axis, a freeform Fresnel lens uses individual triangular or trapezoidal facets that comprise a freeform surface. This type of lens combines the capability of a freeform surface with the benefits of a Fresnel lens, in particular: thin profile, low cost, small size, and relatively simple geometry calculations. An algorithm is presented to design such a lens that generates an output intensity distribution without depending on symmetry in the light source, the lens aperture, or the output intensity distribution. Two example systems are presented, demonstrating how a freeform Fresnel lens can reshape a beam of light without relying on symmetry. [ABSTRACT FROM AUTHOR]

Rudolf Kingslake (1903 to 2003) is perhaps the most widely-known name in lens design and is arguably recognized as the father of lens design in the United States. Although his contributions in optical design, engineering, and education after he moved to the United States in 1929 are generally well-known, little has been written about his technical activities beforehand. In the early summer of 1929, the president of the University of Rochester, Rush Rhees, visited England to recruit faculty members for the new Institute of (Applied) Optics and hired 26-year-old Rudolf Kingslake as its first faculty member, and appointed him as assistant professor of geometrical optics and optical design. The following review of Kingslake's nine published papers while at the Imperial College illustrates his early and already remarkable talents in the field of optical engineering and justifies Dr. Rhees' insightful decision. Kingslake made significant contributions in the area of optical testing. In particular, he expanded the utility of the Hartmann test to measure oblique aberrations and improved the metrology for large optics, and was the first to mathematically analyze interferograms to obtain the primary aberration coefficients. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present microlens arrays (MLA) with long focal length (in millimeter range) based on thermal reflow process. The focal length of microlens is usually in the same order of lens diameter or several hundred microns. To extend focal length, we made a photoresist (SU-8) MLA covered by a Polydimethylsiloxane (PDMS) film on a glass substrate. Because the refractive index difference between PDMS and photoresist interface is lower than that of air and MLA interface, light is less bended when passing through MLA and is focused at longer distance. Microlenses of diameters from 50μm to 240μm were successfully fabricated. The longest focal length was 2.1mm from the microlens of 240μm diameter. The numerical aperture (NA) was reduced 0.06, which is much lower than the smallest NA (~0.15) by regular thermal reflow processes. Cured PDMS has high transmittance and becomes parts of MLA without too much optical power loss. Besides, other focal lengths can be realized by modifying the refractive index different between two adjacent materials as described in this paper. [Copyright &y& Elsevier]

Abstract: This study proposed a two-stage LED lens design optimization system, and used the viewing angle and the luminance uniformity as the optical quality objective. Optical design software (TracePro) and the orthogonal table of Taguchi method were used for simulation experiment. In the first stage, the viewing angle was used as the optical quality objective to find out the preliminary optimization of lens shape. The optimal LED lens size parameter combination of the first stage was used in the second stage to create L25(56) orthogonal table, and then the Back-Propagation Neural Network (BPNN) was used to establish the LED lens quality predictor to predict the FWHM angle and luminance uniformity in different overall sizes. The Genetic Algorithm (GA) with the quality predictor was used to find out the optimum design parameter combination of overall size according to the required quality objective. A LED with wide viewing angle and high luminance uniformity was taken as an example in this study to design a LED optical lens with 135° FWHM angle and 93.35% uniformity. [Copyright &y& Elsevier]

We study here the problem of determining a system of two refractive interfaces transforming a plane wavefront of a given shape and radiation intensity into a coherent output plane wavefront with prescribed output position, shape and intensity. Such interfaces can be refracting surfaces of two different lenses or of one lens. In geometrical optics approximation, the analytic formulation of this problem in both cases requires construction of maps with controlled Jacobian. Though this Jacobian can be expressed as a second order partial differential equation of Monge-Ampère type for a scalar function defining one of the refracting surfaces, its analysis is not straightforward. In this paper we use a geometric approach for reformulating the problem in certain associated measures and defining weak solutions. Existence and uniqueness of weak solutions in Lipschitz classes for both cases are established by variational methods. Our results show, in particular, that two types of interfaces exist in each case for the same data: one of these types always consists of two interfaces, one of which is concave or convex and the second convex or concave, while the interfaces of the second type may be neither convex nor concave. The availability of a design with convex/concave lenses is particularly important for fabrication. The truly geometric nature of this problem permits its statement and investigation in $${\mathbb {R}^{N+1},\, N \geqq 1}$$ . [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a novel application of Particle Swarm Optimization (PSO) technique to lens design. A mathematical model is constructed, and merit functions in an optical system are employed as fitness functions, which combined radiuses of curvature, thicknesses among lens surfaces and refractive indices regarding an optical system. By using this function, the aberration correction is carried out. A design example using PSO is given. Results show that PSO as optical design tools is practical and powerful, and this method is no longer dependent on the lens initial structure and can arbitrarily create search ranges of structural parameters of a lens system, which is an important step towards automatic design with artificial intelligence. [Copyright &y& Elsevier]

The magnetic electron objective lens is of a great importance which limit the resolving power of the electron microscope. The present work investigates the objective focal properties of a single polepiece magnetic electron lens of truncated cone polepiece shape of the selected geometrical dimensions for practical applications. The lens has been fabricated consist of cast shield made of mild steel combined with exciting isolated cooper coil of 500 turns. The theoretical and experimental results presented the magnetic flux density distribution and the objective focal properties of the lens, in mode of operation when the direction of incident electrons beam facing the lens back plate of the lens. Moreover, the theoretical and experimental results are in a good agreements. [ABSTRACT FROM AUTHOR]

The genetic algorithm (GA) is applied to the optimization of a sub-millimeter wave horn-lens collimation equipment operating at 150 GHz, and measurement is carried out to validate the performance of the optimized geometry. The aperture-integration (AI) method is employed to formulate the fitness function of GA in dealing with complex field distribution from an arbitrary radiation source. A diagonal horn and the auxiliary lens are fabricated according to the GA-optimized geometry, and their radiation properties are measured employing a BWO (Backward-wave Oscillator) with a golay cell terahertz detector. The measurement indicates that the gain and near-field beam radius conform to the values predicted by GA. [ABSTRACT FROM AUTHOR]

A planar array of passive lens elements can be phased to approximate the effect of a curved dielectric lens. The rotational orientation of each element can provide the required phase shift for circular polarization. The array elements must be designed so that the hand of circular polarization changes as the electromagnetic wave passes through the lens. An element is presented that is based on an aperture-coupled microstrip patch antenna, and two lenses are designed. Each lens has a diameter of 254 mm and contains 349 elements. The elements have identical dimensions but the rotational orientation of each element is selected to provide a specific lens function. The first lens is designed to collimate radiation from a feed horn into a beam pointing 20^\circ from broadside. At 12.9 GHz the aperture efficiency is 48%. The second lens acts as a Wollaston-type prism. It splits an incident wave according to its circular polarization components. [ABSTRACT FROM AUTHOR]

The article presents a compact projection lens with double-layered diffractive optical elements (DOEs) based on properties DOEs including mass savings and freely modulate the wavefront of incident light. The DOEs are composed of five lenses half the weight of its original structure. It compares the analysis for the lenses which results in the savings in mass at the same specification with double-layered DOEs.

We have designed and implemented a large aperture electrostatic Einzel lens that magnifies the images of low energy ions or electrons in a standard velocity map imaging apparatus by up to a factor of 5 while allowing the normal use of the apparatus (without blocking any part of the detector). The field strength in the interaction region remains reasonably constant with or without magnification, and the lens can be used in the normal 'crush' mode or with any of the different variants of the 'slicing' mode. We have characterized the performance of the lens by imaging ion recoil due to two-photon resonant three-photon ionization [(2+1) REMPI] of O(3P2) atoms and by imaging slow NO molecules from the near-threshold photodissociation of the NO-Ar van der Waals complex. [ABSTRACT FROM AUTHOR]

The phase errors of the conventional trifocal Rotman lens and its modified quadrufocal designs could be reduced by adopting a non-focal design scheme. The non-focal design produces minimum average phase errors for all beam ports rather than achieving zero-phase error for only selected focal points. Fundamental models of designing and optimising typical trifocal and quadrufocal planar bootlace lenses are reviewed. Results based on the non-focal design method are compared to the ones from conventional designs, and noticeable improvements demonstrate that the non-focal design scheme is an alternative way of optimising the phase errors for the Rotman lens design. As in referenced papers on multiple-focal designs, the emphasis is on the phase-error analysis and not on experimental verifications. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present advances in the design of lenses based on left-handed extraordinary transmission metamaterials which provide high transmission and focusing despite the subwavelength size of their constituent apertures. Due to the effective negative index of refraction of the close-stack of subwavelength hole arrays, concave profiles are required for focusing instead of the convex geometries of dielectric lenses. An analysis of the foci produced by plano- and bi-concave lens is carried out. [Copyright &y& Elsevier]

Abstract: A slab with permittivity , relative to the environment, can be used as a near-field superlens (NFSL) for one polarization. To design a NFSL for any chosen visible wavelength, we investigate periodic silver–dielectric composites with effective permittivity close to . The initial design choices are based on the Maxwell Garnett mixing formula, and these are further refined using a combination of the Rayleigh formula and the Drude model for the complex permittivity of silver. The most promising composite turns out to be a silver slab with cylindrical air-holes occupying a volume fraction between 35 and 73%, which covers the whole visible range from 400 to 700nm. The quasistatic accuracy of the predicted effective permittivity is verified using an accurate analytical solution, and the superlensing effect is demonstrated for one composite NFSL setup for violet light using numerical simulations. Finally, the correction required by nanoscale size effects on the permittivity function of silver is taken into consideration and its effect on the performance of the composite lens is estimated. [Copyright &y& Elsevier]

Electron lenses are extremely poor: if glass lenses were as bad, we should see as well with the naked eye as with a microscope! The demonstration by Otto Scherzer in 1936 that skilful lens design could never eliminate the spherical and chromatic aberrations of rotationally symmetric electron lenses was therefore most unwelcome and the other great electron optician of those years, Walter Glaser, never ceased striving to find a loophole in Scherzer’s proof. In the wartime and early post-war years, the first proposals for correcting Cswere made and in 1947, in a second milestone paper, Scherzer listed these and other ways of correcting lenses; soon after, Dennis Gabor invented holography for the same purpose. These approaches will be briefly summarized and the work that led to the successful implementation of quadupole–octopole and sextupole correctors in the 1990s will be analysed. In conclusion, the elegant role of image algebra in describing image formation and processing and, above all, in developing new methods will be mentioned. [ABSTRACT FROM AUTHOR]

The article discusses the applications of mathematical lens. Being cited are the questions that assume cylinders and cones do not include the interior points. The author cites a solution saying that if the radius of a cylinder is one, and the angle of inclination of the plane that intersects is 45 degrees, it is important then to find the equation of the intersection. It is also important to generalize the equation for a cylinder having the radius and angle of inclination. Hence, the author emphasizes the significance of describing the changes in the elliptical cross section of a cylinder as the intersecting plane more vertical.

Abstract: This research formulates an elliptical-based Fresnel lens concentrator system using optical geometry and ray tracing technique. The author incorporates solar spectrum with the refractive indices of lens materials to form different color mixes on the target plane. The model illustrates the solar spectrum distributions under the Fresnel lens. It can be used to investigate each spectral segment''s distribution patterns and helps to match the concentration patterns of different wavelengths to different solar energy applications. [Copyright &y& Elsevier]

While computer technology continues to enhance the teaching and learning of all science disciplines, computer simulations, in particular, have become exceptionally beneficial in physics education. In addition to the manner in which physics instructors integrate computer simulations into their instructional practices, the design of a simulation may also determine its potential for influencing a student's conceptual development and understanding. This paper examines the effects of four differently designed simulations on students' predictions and subsequent understanding of how images are formed by converging lenses, specifically in relation to outcomes when portions of the lens or object are covered. Results indicated that differing numbers of rays depicted in the lens simulations had little effect on student predictions, but the origination point(s) of the rays did influence student predictions. Also reported is how minimal instructor scaffolding substantially influenced student use and value perceptions of the simulation. [ABSTRACT FROM AUTHOR]

This article discusses the development of an ultrasonic injection molding (UIM) system, whereby ultrasonic waves are applied to injection molding technology. When optical lenses were molded, it was discovered that the process increased the weight when applied immediately after the resin was filled into a cavity. The application of ultrasonic waves also generated oscillatory flow within the cavity. Shrinkage during the packing and holding stages was reduced by oscillatory flow provided by ultrasonic vibrations.

A computer code for analyzing nano-particle motions in an aerodynamic particle beam focusing system was developed. The code uses an accurate three-dimensional model for the Brownian diffusion of nano-particles in strongly varying pressure field in the aerodynamic lens system. Lagrangian particle trajectory analysis was performed assuming a one-way coupling model. The particle equation of motion used included drag and Brownian forces. The prediction of the 3-D model for penetration efficiency, beam divergence angle, beam diameter and radial cumulative fraction were evaluated and were compared with those of the axisymmetric models. The simulation results showed that for particle diameters less than 30 nm in helium gas, the Brownian force could significantly affect the beam focusing and particle penetration efficiency. Some potential errors in the naive usage of axisymmetric model were discussed. It was shown that the earlier axisymmetric models lead to the incorrect mean square radial displacement of Brownian particles. The present 3-D approach, however, leads to the correct value of the radial mean square displacement of 4Dt. The effect of the inlet orifice and relaxation region on the performance of the lens system was also investigated. It was shown that the major losses of the 4 to 10 nm particles occur in the inlet orifice and relaxation region walls. For 15 to 30 nm particles, the main losses occur at the inlet orifice walls. Some alterations of the shape of the inlet orifice were examined and a new design is suggested to reduce the loss of the particles at the inlet flow control orifice. [ABSTRACT FROM AUTHOR]

Motivated by the anticipated advantageous performance of diamond kinoform refractive lenses for synchrotron X-ray radiation studies, this report focuses on progress in designing, nanofabricating and testing of their focusing performance. The method involves using lift-off and plasma etching to reproduce a planar definition of numerically determined kinoform refractive optics. Tests of the focusing action of a diamond kinoform refractive lens at the APS 8-ID-I beamline demonstrate angular control of the focal spot. [ABSTRACT FROM AUTHOR]

This paper describes a fast rendering algorithm for verification of spectacle lens design. Our method simulates refraction corrections of astigmatism as well as myopia or presbyopia. Refraction and defocus are the main issues in the simulation. For refraction, our proposed method uses per-vertex basis ray tracing which warps the environment map and produces a real-time refracted image which is subjectively as good as ray tracing. Conventional defocus simulation was previously done by distribution ray tracing and a real-time solution was impossible. We introduce the concept of a blur field, which we use to displace every vertex according to its position. The blurring information is precomputed as a set of field values distributed to voxels which are formed by evenly subdividing the perspective projected space. The field values can be determined by tracing a wavefront from each voxel through the lens and the eye, and by evaluating the spread of light at the retina considering the best human accommodation effort. The blur field is stored as texture data and referred to by the vertex shader that displaces each vertex. With an interactive frame rate, blending the multiple rendering results produces a blurred image comparable to distribution ray tracing output. [ABSTRACT FROM AUTHOR]

The different methods of optical systems' optimization such as Newton and least squares along with their modifications are reviewed. The Monte Carlo technique, as a statistical method which can overcome the shortcomings of these classic methods (such as the rate of convergence, the possibility of finding the overall minimum and avoiding local minima), is presented and compared with the others. A numerical example is presented to verify the method. [ABSTRACT FROM AUTHOR]

The article highlights the ZEISS Optical Optimization & Management process used by Carl Zeiss Vision in developing GT2 lens in the U.S. The author stated that ZEISS has always relied on a sophisticated lens design process that delivers the most advanced progressive lenses available. He added that careful management of the overall global configuration of the lens design is the first stage of the ZEISS Optical Optimization & Management process. Moreover, the second stage of the process is an intensive, point-by-point refinement of the entire lens surface using computer raytracing and sophisticated optimization routines.

Abstract: The mechanisms involved in photoresist microlens formation are investigated in order to understand the lack of sphericity of certain experimental microlenses. A characterization of the resist rheological properties has enabled to demonstrate that there is a competition between surface tensions and resist crosslinking reaction during the final process bake. Depending on the process conditions, the crosslinking reaction kinetics dominate and prevent the correct formation of the microlens. [Copyright &y& Elsevier]

Part I. Focuses on the evolution of the motion picture camera lens. Changes in lens diameter; Application of magnesium chloride coating in 1946; Improvement in lens design criteria and optical design methodology.

Purpose: To compare the shape recovery ratios after compression of haptic materials used in the manufacture of intraocular lenses (IOLs).Setting: Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.Methods: The loop memory of 40 silicone-optic posterior chamber IOLs was studied. All the IOLs had modified-C haptics made of poly(methyl methacrylate) (PMMA; n = 10), polyimide (n = 10), polyvinylidene fluoride (PVDF; n = 10), and polypropylene (PP; n = 10). After the overall diameter of each lens was measured (day 0), the lenses were inserted into plastic wells (9.5 mm in diameter) and immersed in water (37°C) for 1 month. They were then placed on an open plate and allowed to reexpand for 2 months. Overall diameter measurements were performed within 5 minutes of the IOLs’ removal from the wells and at subsequent time points (days 14, 28, 30, 60, 74, 88, and 95).Results: The loop memory of each lens was expressed as the difference between the initial overall diameter measurement (pretest) and the measurement at each time point; the lower the value, the higher the memory. The overall difference among the 4 groups was statistically significant at each time point (P ≤ .001). From days 30 to 95, silicone-PMMA, silicone-elastimide, and silicone-PVDF IOLs had similar loop memory mean values, which were significantly lower than the mean value of silicone-PP IOLs (P < .05). The latter design tended to be deformed after removal from the wells, with increased optic-haptic angulation.Conclusion: Studying the loop memory of haptic materials (PMMA, polyimide, PVDF, and PP) used in the manufacture of posterior chamber IOLs can help surgeons choose an appropriate IOL for each patient. [Copyright &y& Elsevier]

Purpose: To analyze the rates of and reasons for intraoperative explantation of foldable and rigid intraocular lenses (IOLs) to determine the complication profile of each IOL design.Setting: Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.Methods: The study comprised data analysis of foldable (n = 85) and rigid (n = 15) IOL specimens that were explanted immediately after primary implantation.Results: Eighty-five foldable intraoperative explants were accessioned. These comprised 14.5% of the 586 foldable IOL explants received between January 1988 and September 2000. There were 15 rigid poly(methyl methacrylate) (PMMA) intraoperative explants out of 2077 rigid explant specimens (0.7%). Fifty-one (60%) of the foldable IOLs requiring intraoperative explantation were the 1-piece silicone plate-haptic large-hole design, and 29 (34.1%) were the 3-piece silicone polyimide-haptic design. The most frequent reason for explantation of both designs was optic damage, 37.3% in the large-hole design and 55.2% in the polyimide design. Optic damage did not occur in rigid PMMA IOLs.Conclusion: Some foldable IOL designs have a higher risk of damage during surgical insertion than rigid designs. Two modern foldable IOLs, the silicone plate-haptic large-hole and the silicone polyimide-haptic, appear to be more prone to damage during folding, loading, and implantation than other IOLs. [Copyright &y& Elsevier]

An introduction is presented in which the editor discusses various reports within the issue on topics including research papers on development of polytopes and convex sets, formulation of polynomial size extension for stable set polytopes and positive semidefinite lift of convex lenses cone.

Ever since they began to take an interest in lens grinding, the brothers Christiaan and Constantijn Huygens searched for high-quality glass to turn in to lenses. Historical research in combination with optical measurements on preserved lenses has allowed the verificationof the lenses ground by the brothers, and also provided information on who helped them with the necessary knowledge and material. [ABSTRACT FROM AUTHOR]

Describes a method for fabricating micromirrors and microlenses on polymer substrates. Production of microelements with diameters of approximately several hundred micrometers and f number ranging from 3 to 11; Layout of the recording setup used to fabricate the optical elements; Profile of an infrared fabricated micromirror.