Effect of crystalline lens surfaces and refractive index on image quality by model simulation analysis

The surfaces and refractive index of crystalline lens play an important role in the optical performance of human eye.On the basis of two eye models,which are widely applied at present,the effect of lens surfaces and its refractive index distribution on optical imaging is analyzed with the optical design software ZEMAX (Zemax Development Co.,San Diego,USA).The result shows that good image quality can be provided by the aspheric lens surfaces or (and) the gradient-index (GRIN) distribution.It has great potential in the design of intraocular lens (IOL).The eye models with an intraocular implantation are presented.     

Weakly and properly nonessential objectives in multiobjective optimization problems

In this work we characterize objective functions which do not change the set of efficient solutions (weakly efficient solutions, properly efficient solutions). Necessary and sufficient conditions for an objective function to be weakly nonessential (properly nonessential) are presented. We establish relations between weakly nonessential, properly nonessential and nonessential functions.     

Unequal probability sampling from a finite population: A multicriteria approach

In this note we address the problem of determining selection probabilities for multipurpose surveys, when the aim is the simultaneous minimization of variances for each variable under study. A characterization of the set of Pareto-optimal designs is given for designs with replacement and also for a class of designs without replacement, namely, Poisson designs.     

Box-constrained multi-objective optimization: A gradient-like method without “a priori” scalarization

The aim of this paper is the development of an algorithm to find the critical points of a box-constrained multi-objective optimization problem. The proposed algorithm is an interior point method based on suitable directions that play the role of gradient-like directions for the vector objective function. The method does not rely on an “a priori” scalarization and is based on a dynamic system defined by a vector field of descent directions in the considered box. The key tool to define the mentioned vector field is the notion of vector pseudogradient. We prove that the limit points of the solutions of the system satisfy the Karush–Kuhn–Tucker (KKT) first order necessary condition for the box-constrained multi-objective optimization problem. These results allow us to develop an algorithm to solve box-constrained multi-objective optimization problems. Finally, we consider some test problems where we apply the proposed computational method. The numerical experience shows that the algorithm generates an approximation of the local optimal Pareto front representative of all parts of optimal front.     

Focal shift for off-axial partially coherent flat topped beams passing a thin lens

Focal shift is evaluated for partially coherent off-axis flat topped beams propagated through a thin lens. We have shown that the focal shift decreases as the off-axis parameter (x₀) increases and, for fully coherent flat topped beams, focal shift is enhanced as the order of flat topped beam decreases, but the partially coherent one does not show this behavior. Also we have shown that there is a critical point for partially coherent flat topped beams. We investigated the dependency of focal shift in thin lens on correlation length and focal length.     

Diffraction of partially coherent X‐rays in clessidra prism arrays

When small triangular prisms are arranged in arrays which have an overall appearance like an hourglass (in Italian: clessidra) they can focus X‐rays owing to a combined action of diffraction and refraction. From the optical point of view these objects can be regarded as a Fresnel variant of concave transmission lenses. Consequently they can provide larger apertures than purely refractive lenses. However, one has to recognize that clessidra lenses will strongly diffract as the lens structure is periodic in the direction perpendicular to the incident beam. In experiments the diffraction is reduced because it is difficult to illuminate the large apertures with a full spatially coherent wavefront. So the illumination is at best partially coherent. In order to interpret available experimental data for this condition, diffraction theory has been applied appropriately to the clessidra structure, taking into account the limited spatial coherence. The agreement between the theoretical simulations and experimental data is very good, keeping the lens properties at their projected values and allowing for only two free model parameters. The first is the lateral spatial coherence; the second is a lens defect, a rounding of all edges and tips in the structure. Both values obtained from the simulations have been found to be in agreement with expectations.     

Thermal Lens Spectroscopy for Quantitative Determination of a Cu(II) Complex With an 8-Aminoquinoline Derivative in Tap Water and Mining Wastewater Samples Using a Dual Beam Technique

Abstract

This article describes the quantitative determination of Cu(II) using thermal lens spectrometry. The chromogenic reaction involving Cu(II) and 5-(4-sulphophenylazo)-8-aminoquinoline in alkaline solution was studied in different experimental conditions such as pH, ligand concentration, methanol volume, and presence of interfering ions. A collinear dual beam set-up has been used for direct quantitation in water samples without a pre-concentration step. The optimized conditions provided a linear calibration in the concentration range from 3.0 to 15.0?×?10^?7?mol L^?1. The detection and quantitation limits were 6.13?×?10^?8? and 2.04?×?10^?7?mol L^?1, respectively. Resultantly, an application to Cu(II) determination in tap water (recovery 99.8–103.3%) and mining (synthetic) wastewater (95.3–98.0%) shows relative SDs ≤ 3.1%. The method is presented as a new alternative for the direct Cu(II) determination in real samples.     

800万像素手机广角镜头设计

为了满足市场对高像素手机广角镜头的需求,设计出一款800万像素大相对孔径的手机广角镜头。该手机镜头由4片塑料非球面透镜和1片红外滤光片组成,镜头的光圈值F为2.45,视场角为80°,采用Omnivision公司的OV8850型号800万像素CMOS图像传感器,最大分辨率为3 280 pixel×2 464 pixel,CMOS图像传感器的像素尺寸为1.1 μm,奈奎斯特频率为454 lp/mm。设计结果显示,镜头在1/2奈奎斯特频率处,0.7视场内的MTF值均大于0.48,全视场的MTF值大于0.38;在奈奎斯特频率处,0.7视场内的MTF值大于0.15;最大畸变小于2%,因此可获得优良的成像质量。     

基于六角形晶格的光子晶体零折射率特性及其光学应用研究

运用色散特性分析的方法,在六角形晶格光子晶体能带结构的布里渊区中心找到了狄拉克点,用等效媒质理论验证了在这一点上光子晶体的等效介电常量和等效磁导率同时为零,即存在狄拉克频点,用此六角形晶格光子晶体可以实现零折射率材料.随后运用有限元数值仿真方法,研究了此六角形晶格结构在狄拉克频点及其附近所呈现的零折射率特性.将此种六角形晶格光子晶体经过合理设计用以制作凹透镜,发现可以实现远场的亚波长聚焦.此外在凹透镜的入射面处引入防反射结构可以在一定程度上增强聚焦效果,提高了系统的分辨率.