Large Lens Research Articles

Posterior capsule opacification, capsular bag distension syndrome, and anterior capsular phimosis: A retrospective cohort study

ObjectiveTo determine the incidence and the risk factors involved in the development of the three main postoperative capsular complications: posterior capsule opacification (PCO), capsular bag distension syndrome (CBDS), and anterior capsular phimosis syndrome (ACP). Subjects, materials and methodsA retrospective cohort study was conducted on 801 patients submitted to cataract surgery in the ophthalmology unit of Hospital del Henares (Madrid) from March 2, 2009 to February 28, 2010. Computerized clinical charts were reviewed during July 2012. PCO was studied using the Kaplan–Meier method (log rank test). ResultsA total of 167 patients developed PCO. No association could be demonstrated between PCO and age, sex, diabetes mellitus, phaco technique, IOL model, tamsulosin intake, glaucoma, and age-related macular degeneration. Three patients developed CBDS, all of them have received a Akreos Adapt AO® (Bausch & Lomb). Two of them were young men who had received surgery for posterior subcapsular cataracts. Three patients developed ACP, 2 of whom had received a MicroSlim® IOL (PhysIOL). ConclusionsNo association was found between PCO and any of the studied variables. Male gender, young age, subcapsular cataract and large non-angulated lens such as Akreos Adapt AO® could be associated with CBDS. ACP could be more frequent when microincision IOLs (like MicroSlim®) are implanted.

Stray light reduction in optical computed tomography using a convergent cone-beam source

The planar diffuser light source for a cone-beam optical CT scanner was replaced with a filtered LED and large Fresnel lens. The source was focused on a camera and convergent cone-beam images were acquired. Images are sensitive to mismatches in the refractive index of vessels, samples and matching liquid. For PETE jars and water solutions, a loss of approximately 30% of the projections was demonstrated. Teflon PFA cylinders provided better refractive index matching and more accurate reconstructions. The convergent cone-beam source dramatically increased imaging efficiency by a factor of 1000 and reduced stray light levels by confining illumination to image forming rays.

Radiochromic film thickness correction with convergent cone- beam optical CT scanner

A cone-beam optical computed tomography (CT) scanner was modified by replacing the diffuse planar yellow light emitting diode (LED) source with violet and red LEDs and a large Fresnel lens. The narrow band sources provided transmission images of radiochromic EBT2 film at 420 and 633 nm, with air as a reference. The dose image was not detectable with the violet source. This demonstrated spectral independence of the two images. Assuming attenuation at 420 nm was dominated by absorption from yellow dye in the active film layer allowed a relative thickness image to be calculated. By scaling the 633 nm optical density image for relative thickness, non-uniformities in the recorded dose distribution due to film thickness variations, were removed.

Technique for Outdoor Test on Concentrating Photovoltaic Cells

Outdoor experimentation of solar cells is essential to maximize their performance and to assess utilization requirements and limits. More generally tests with direct exposure to the sun are useful to understand the behavior of components and new materials for solar applications in real working conditions. Insolation and ambient factors are uncontrollable but can be monitored to know the environmental situation of the solar exposure experiment. A parallel characterization of the photocells can be performed in laboratory under controllable and reproducible conditions. A methodology to execute solar exposure tests is proposed and practically applied on photovoltaic cells for a solar cogeneration system. The cells are measured with concentrated solar light obtained utilizing a large Fresnel lens mounted on a sun tracker. Outdoor measurements monitor the effects of the exposure of two multijunction photovoltaic cells to focused sunlight. The main result is the continuous acquisition of theV-I(voltage-current) curve for the cells in different conditions of solar concentration and temperature of exercise to assess their behavior. The research investigates electrical power extracted, efficiency, temperatures reached, and possible damages of the photovoltaic cell.

使用高精度三坐标测量仪实现透镜定中心

Due to the limits of light sources,the sizes of rotating platforms and the propagation of assembling errors,traditional methods of lens centering are not suitable for the assembly of largeaperture and multi-lens optical systems.Thus a new high-precision mechanical measurement method for lens centering was proposed based on a three Coordinate Measuring Machine(CMM).Principles and algorithms for measuring off-centering of the large aperture lens using the high-accuracy CMM were introduced.In the measurements,the angle between the optic axis of lens and the reference axis was calculated after the figure fitting of the measuring points,and then the centering of deviation was calculated.The method was verified by the assembling of a long focal length and large aperture imaging system.The assembling result shows that the lens off-centering is 6.47″and the repeatability error is(1.16×10-4)″.As changing the optical measurement into a mechanical measurement,this proposed method ensures the accuracy,reduces the difficulty and improves the efficiency of lens assembly.It is able to be applied to the high-precision assembly of large aperture transmitting optical systems.

Simulation-Based Optimization of Cure Cycle of Large Area Compression Molding for LED Silicone Lens

Three-dimensional heat transfer-curing simulation was performed for the curing process by introducing a large area compression molding for simultaneous forming and mass production for the lens and encapsulants in the LED molding process. A dynamic cure kinetics model for the silicone resin was adopted and cure model and analysis result were validated and compared through a temperature measurement experiment for cylinder geometry with cure model. The temperature deviation between each lens cavity could be reduced by implementing a simulation model on the large area compression mold and by optimizing the location of heat source. A two-step cure cycle was constructed to reduce excessive reaction peak at the initial stage and cycle time. An optimum cure cycle that could reduce cycle time by more than 29% compared to a one-step cure cycle by adjusting dwell temperature, heating rate, and dwell time was proposed. It was thus confirmed that an optimization of large area LED lens molding process was possible by using the present experiment and the finite element method.

Deformation and Thermal Analysis of the Guideways of a Large Scale Aspheric Machine Tool

Large scale aspheric lens are very important in both national defense and civil industries. For the fabrication of such lens, a large scale aspheric machine tool is developed. In this paper, we focus on the analysis of the temperature distribution and the deformation of the guideways of this machine tool. Thermal and strain deformation of three guideways are analyzed when the thickness of the oil film is different, and the relationship between the thickness of the oil film and the deformation is built up.

A Comparison of the Short-Term Settling of Three Scleral Lens Designs

Scleral gas-permeable lenses are rapidly gaining international popularity. Unlike corneal gas-permeable lenses, scleral lenses are fitted to the bulbar conjunctiva and settle into the tissue after insertion. To date, we are unaware of any studies examining the settling behavior of three varying scleral lens designs. The purpose of this study was to quantify the mean total settling and mean rates of settling for three scleral lens designs: Onefit P&A (Blanchard Contact Lens, Inc), Mini Scleral Design (msd) (Blanchard Contact Lens, Inc), and Jupiter (Visionary Optics). A randomized, repeated-measures study of Onefit P&A, msd, and Jupiter was performed. Subjects were fitted from a trial lens set, according to the manufacturer's guidelines. After insertion, lens settling was measured at 0 minutes, 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 4 hours, 6 hours, and 8 hours. Statistical analyses were performed using analysis of variance and two-stage, nonlinear regression analyses of settling over time. On average, the Onefit P&A, msd, and Jupiter lenses settled a total of 113.7, 133.7, and 88.1 μm, respectively. Although the rates of settling were not linear, analysis of variance revealed a significant difference in the average settling rates (p < 0.05) among the groups. Tukey analyses revealed a significant difference in the settling rates for msd and Jupiter comparison (p < 0.05). Nonlinear regression analyses predicted that the lenses settled to about 80% of the final estimated values for the Onefit P&A lens, 90% for msd, and 99% for the Jupiter, after 8 hours. We concluded that the amount of settling varied significantly among the three lens designs. Settling rates were greatest shortly after insertion. Larger lenses were estimated to be settled by 8 hours. Based on the results of this short-term study, careful consideration to the settling patterns of individual scleral lens designs should be given.

Opacificación de la cápsula posterior, síndrome de distensión capsular y síndrome de fimosis de la cápsula anterior: estudio de cohortes retrospectivo

ObjectiveTo determine the incidence and the risk factors involved in the development of the three main postoperative capsular complications: posterior capsule opacification (PCO), capsular bag distension syndrome (CBDS), and anterior capsular phimosis syndrome (ACP). Subjects, material and methodsA retrospective cohort study was conducted on 801 patients submitted to cataract surgery in the ophthalmology unit of Hospital del Henares (Madrid) from March 2, 2009 to February 28, 2010. Computerized clinical charts were reviewed during July 2012. PCO was studied using the Kaplan-Meier method (log rank test). ResultsA total of 167 patients developed PCO. No association could be demonstrated between PCO and age, sex, diabetes mellitus, phaco technique, IOL model, tamsulosin intake, glaucoma, and age-related macular degeneration. Three patients developed CBDS, all of them have received and Akreos Adapt AO® (Bausch & Lomb). Two of them were young men who had received surgery for posterior subcapsular cataracts. Three patients developed ACP, 2 of whom had received a MicroSlim® IOL (PhysIOL). ConclusionsNo association was found between PCO and any of the studied variables. Male gender, young age, subcapsular cataract and large non-angulated lens such as Akreos Adapt AO® could be associated with CBDS. ACP could be more frequent when microincision IOLs (like MicroSlim®) are implanted.

Cosmic equation of state from combined angular diameter distances: Does the tension with luminosity distances exist?

Using relatively complete observational data concerning four angular diameter distance (ADD) measurements and combined $\mathrm{SN}+\mathrm{GRB}$ observations representing current luminosity distance (LD) data, this paper investigates the compatibility of these two cosmological distances considering three classes of dark energy equation of state (EoS) reconstruction. In particular, we use strongly gravitationally lensed systems from various large systematic gravitational lens surveys and galaxy clusters, which yield the Hubble constant independent ratio between two angular diameter distances ${D}_{ls}/{D}_{s}$ data. Our results demonstrate that, with more general categories of standard ruler data, ADD and LD data are compatible at $1\ensuremath{\sigma}$ level. Second, we note that consistency between ADD and LD data is maintained irrespective of the EoS parametrizations: there is a good match between the universally explored Chevalier-Polarski-Linder model and other formulations of cosmic equation of state. Especially for the truncated generalized equation of state (GEoS) model with $\ensuremath{\beta}=\ensuremath{-}2$, the conclusions obtained with ADD and LD are almost the same. Finally, statistical analysis of generalized dark energy equation of state performed on four classes of ADD data provides stringent constraints on the EoS parameters ${w}_{0}$, ${w}_{\ensuremath{\beta}}$, and $\ensuremath{\beta}$, which suggest that dark energy was a subdominant component at early times. Moreover, the GEoS parametrization with $\ensuremath{\beta}\ensuremath{\simeq}1$ seems to be a more favorable two-parameter model to characterize the cosmic equation of state, because the combined angular diameter distance data ($\mathrm{SGL}+\mathrm{CBF}+\mathrm{BAO}+\mathrm{WMAP}9$) provide the best-fit value $\ensuremath{\beta}=0.75{1}_{\ensuremath{-}0.480}^{+0.465}$.

Correcting large lens radial distortion using epipolar constraint.

It is necessary to correct lens distortion for building 3D models from multiple 2D images. Lens distortion is usually dominated by radial components, and especially dominated by the first radial distortion term that is called large lens radial distortion. In this work, we propose a method for correcting large lens radial distortion based on epipolar constraint. It requires nothing but a number of image point correspondences from two views, while the distortion center is assumed to be at the image center. Experimental results show that the robustness and correction accuracy of the proposed method outperform those of the previous methods.

Genetic algorithm to design Laue lenses with optimal performance for focusing hard X- andγ-rays

In order to focus hard X- and gamma-rays it is possible to make use of a Laue lens as a concentrator. With this optical tool it would be possible to improve the detection of radiation for several applications, spanning from the observation of the most violent phenomena in the sky to nuclear medicine applications, for diagnostic and therapeutic purposes. A code named LaueGen, based on a genetic algorithm and aimed to designing optimized Laue lenses, has been implemented. The genetic algorithm was selected because the optimization of a Laue lens is a complex and discretized problem. The output of the code consists in the design of a Laue lens composed of diffracting crystals selected and arranged in such a way to maximize the performance of the lens. The code allows one to manage crystals of any material and crystallographic orientation. The program is structured in such a way that the user can control all the initial parameters of the lens. As a result, LaueGen is highly versatile and can be used for the design of very small lens, e.g. for nuclear medicine, to very large lens, e.g. for satellite-borne astrophysical missions.

Machining Mechanism of Fresnel Lens Mold

This paper analyzed the large diameter Fresnel lens mold machining mechanism based on modal test methods .The design and mold machining principle of Fresnel lens were introduced . Explored the cutting speed and feed on chip formation process. The results show that: the material strength and plastic brittle have significant impact on chip morphology in the H62 brass mold processing, an improvement of material strength with the increase of strain rate and the evolution process of the chip can be divided into: ribbon cuttings, serrated chips, cell chips.

Giant retinal tear complicated with subretinal lens fragment following femtosecond laser cataract surgery

Femtosecond laser-assisted cataract surgery is a new technique that offers the possibility to have some steps of the surgery done by an extremely precise machine with very high accuracy. Despite the high influence on the surgery steps of a nonsubjective machine, there are still some possible potential errors especially during the learning curve of the surgeon who is still crucial in both, the management and also the proceeding of the cataract surgery. We are reporting the case of a 61-year-old man, which was referred to our retinal department because of luxation of multiple lens fragments following femtosecond laser cataract surgery in his right eye, performed 1 day before. The anterior segment examination revealed residual lens cortex in the anterior chamber, an eccentric and intact anterior capsulorhexis, and a large posterior capsule rupture. During removal of the lens fragments from the posterior segment, a giant retinal tear was discovered in the infero-temporal periphery of the right eye, approximately 130 ° in circumferential extension, associated with a large subretinal lens fragment. Removal of the dropped lens fragments from both the vitreous and the subretinal space, as well as the management of the giant retinal tear are described. This case describes a rare intraoperative complication of a femtosecond laser-assisted cataract surgery, and we are trying to discuss different scenarios, which could have caused the capsular break and the retinal tear, thus offering possible pathways to prevent this kind of situations.

Basic Study on High Efficiency Ultra-Precision Grinding of the Optical Glass Lens

The demand for large aperture lenses with high surface quality and form accuracy used for single-lens reflex cameras has been increasing. Generally, large aperture glass lenses are produced by ultra-precision grinding. Considering the increasing global competition, the grinding process has to be improved. However, highly efficient grinding causes worse surface quality, which leads to much polishing and ultimately results in lower form accuracy. Thus in this study, aiming at the realization of highly efficient and precise grinding of glass lenses, cross grinding of optical glass BK7 is carried out. As a first step of the study, the influence of grinding conditions on the surface quality is investigated experimentally.

Influence of Light at Night on Melatonin Suppression in Children

The sensitivity of melatonin to light suppression is expected to be higher in children because children have large pupils and pure crystal lenses. However, melatonin suppression by light in children remains unclear. We investigated whether light-induced melatonin suppression in children is larger than that in adults. Thirty-three healthy primary school children (mean age, 9.2 ± 1.5 y) and 29 healthy adults (mean age, 41.6 ± 4.7 y) participated in two experiments. In the first experiment, salivary melatonin concentrations in 13 children and 13 adults were measured at night under a dim light (<30 lux) and a moderately bright light (580 lux) in an experimental facility. Pupil diameters were also measured under dim light and bright light. In the second experiment, melatonin concentrations in 20 children and 16 adults were measured under dim light in the experimental facility and under room light at home (illuminance, 140.0 ± 82.7 lux). In experiment 1, the melatonin concentration was significantly decreased by exposure to moderately bright light in both adults and children. Melatonin suppression was significantly larger in children (88.2%; n = 5) than in adults (46.3%; n = 6; P < .01), although the data for some participants were excluded because melatonin concentrations had not yet risen. In experiment 2, melatonin secretion was significantly suppressed by room light at home in children (n = 15; P < .05) but not in adults (n = 11). We found that the percentage of melatonin suppression by light in children was almost twice that in adults, suggesting that melatonin is more sensitive to light in children than in adults at night.

Circumventing Scherzer's Theorem: Large Numerical Aperture Objective Lenses for Pulsed Electron Microscopy

Scherzer’s theorem states that all static round magnetic and electro-static electron lenses possess positive spherical aberration [1]. As a result, in recent years, much effort has been invested in techniques to correct for the spatial aberrations (Cs) of objective lenses in high resolution electron microscopy. For pulsed electron sources, such as those required for ultrafast transmission electron microscopy (UTEM), an alternative strategy for Cs aberration correction is possible through the use of the dynamic lensing properties of RF cavities [2] that, when operated in the appropriate oscillation mode, can possess negative spherical aberration [3]. For single-shot imaging UTEM, which requires ~ 10 8 electrons/pulse, simulations indicate that a large numerical aperture (NA > 0.1) objective lens will also be required to mitigate against deleterious space-charge effects [4] – effectively by minimizing the time electrons experience a high charge density. Here, we present a theoretical analysis of the possibility of using the focusing properties of RF cavities to compensate for the spherical aberration of large NA objective lenses for pulsed electron microscopy.

Large aperture adaptive doublet polymer lens for imaging applications.

We report a full design process-finite element modeling, fabrication, and characterization-of adaptive doublet polymer lenses. A first-order model was developed and used to design fluidic doublets, analogous to their glass counterparts. Two constant-volume fluidic chambers were enclosed by three flexible membranes, resulting in a variable focal length doublet with a clear aperture of 19.0 mm. Chromatic focal shift was then used to compare numerical modeling to experimentally measured results over a positive focal length range of 55-200 mm (f/2.89 to f/10.5).

Angle of incidence averaging in reflectance measurements with optical microscopes for studying layered two-dimensional materials.

Reflectance spectrum measured using an optical microscope with a large numerical aperture objective lens is shown to get modified. The change is most prominent when there are optical interference related features in the spectrum. This modification is shown to arise primarily due to the wide range of angles of incidence involved in the measurement and a simple formulation is provided to correct for this in simulations. The importance of such analysis is brought out through a reflectance contrast spectroscopy based study for identifying mono-layer and bi-layer graphene and MoS2.

Using large aperture projection optics to monitor characteristic parameters of far field speckle

In order to systematically evaluate the characteristic parameters of far field speckle in the real atmosphere condition and analyze the influence of laser atmospheric propagation on the optoelectronic system, a monitoring method is presented using large aperture projection optics. The projection optics is made of low cost and large aperture Fresnel lens, which can project the irradiance distribution of far field speckle on the CCD detector. The receiving power and scintillation index on a certain aperture can be evaluated through CCD imaging process. The beam wander and beam radius can also be evaluated under the condition that the receiving aperture is large enough and the speckle would not leave the Fresnel lens because of the beam wander effect. The error of CCD pixel response non-uniformity and its influence and the calibration of CCD irradiance response function and image geometric projection coefficient are discussed. The experiments show that this system is feasible for the monitoring of far field speckle characteristic parameters in the laser atmospheric propagation. Especially for the free space optical communication, it can prove experiment data support on the slow fading research of median level and optimal design of detection threshold under the complex influence of atmospheric extinction and various kinds of turbulence effects.