Rod and spherical silica microlenses fabricated by CO2 laser melting

The fabrication and testing of glass microlenses with rod and spherical shapes are described. The sizes of the lenses range from tens of micrometers to several millimeters. The surfaces of the lenses were fabricated by the melting method. These surfaces have been studied by several methods. The theoretical behavior of the lenses was investigated by ray tracing. Some applications of the lenses are presented.     

Design of a wavelength multiplexer-demultiplexer by the use of planar microlenses

The ray-tracing method is applied to design a wavelength multiplexer-demultiplexer by the use of planar microlenses as focusing and collimating elements. By simulating both uniform and Gaussian intensity distributions of the input sources, we find the position of the input-output components of the wavelength multiplexe-rdemultiplexer, which maximizes the coupling efficiency in each channel. Losses are also evaluated.     

Modeling microlenses by use of vectorial field rays and diffraction integrals

A nonparaxial vector-field method is used to describe the behavior of low-f-number microlenses by use of ray propagation, Fresnel coefficients and the solution of Maxwell equations to determine the field propagating through the lens boundaries, followed by use of the Rayleigh-Sommerfeld method to find the diffracted field behind the lenses. This approach enables the phase, the amplitude, and the polarization of the diffracted fields to be determined. Numerical simulations for a convex-plano lens illustrate the effects of the radii of curvature, the lens apertures, the index of refraction, and the wavelength on the variations of the focal length, the focal plane field distribution, and the cross polarization of the field in the focal plane.     

Failure analysis of plastic spherical shells impacted by a projectile

The main objective of the current work is to present an adequate model for the large deformation of a plastic spherical shell impacted by a projectile. On the basis of experiments, the deformation mode of a spherical shell was developed by introducing an isometric transformation of surface bending and the Perzyna–Symonds viscoplastic constitutive equations. By adopting a numerical method, the deformation of a spherical shell under local impact was investigated and the deformation mode was obtained. Finally, a comparison made between theoretical predictions, numerical results and experimental values indicated that the three groups of results were in better conformity with each other.     

Testing of refractive silicon microlenses by use of a lateral shearing interferometer in transmission

Wave aberrations of refractive photoresist microlenses and silicon microlenses were measured with a lateral shearing interferometer. Because of the silicon elements, a near-infrared working wavelength (lambda = 1.32 mum) was used. The wave front was evaluated by a phase step technique with four steps. Integration of the phase distributions was performed with a computationally efficient Fourier transformation algorithm. The influence of the detector vidicon nonlinearity on the measured wave front was calculated. The defocusing behavior of the interferometer was investigated by fitting the measured wave fronts with the help of Zernike circle polynomials. It is shown that the reproducibility can be kept below lambda/100 rms. Examples for the measured wave fronts of plano-convex silicon microlenses are discussed in detail.     

Analytical model of a three-dimensional integral image recording system that uses circular- and hexagonal-based spherical surface microlenses

A mathematical model for a three-dimensional omnidirectional integral recording camera system that uses either circular- or hexagonal-based spherical surface microlens arrays is derived. The geometry of the image formation and recording process is fully described. Matlab is then used to establish the number of recorded micro-intensity distributions representing a single object point and their dependence on spatial position. The point-spread function for the entire optical process for both close and remote imaging is obtained, and the influence of depth on the point-spread dimensions for each type of microlens and imaging condition is discussed. Comparisons of the two arrangements are made, based on the illustrative numerical results presented.     

Temperature stresses in a multilayer hollow spherical body under heating by steady sources

Closed analytical solutions are obtained of steady-state problem of heat conduction and static thermoelasticity for a multilayer hollow spherical body heated by steady sources.     

Vacuum heating of spherical alumina particles

Heating of spherical alumina particles by high-intensity laser radiation under vacuum conditions to the melting temperature is investigated with account for the nonuniform distribution of energy sources with respect to the particle volume.B. I. Stepanov Institute of Physics, Academy of Sciences of Belarus, Minsk. Translated fron Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 3–4, pp. 307–312, September–October, 1994.     

Effective spherical aberration compensation by use of a nematic liquid-crystal device

The next generation of optical data storage system beyond DVDs will use blue laser light and an objective lens with a high numerical aperture of 0.85 to increase storage capacity. Such high numerical aperture systems have an inherent higher sensitivity to aberrations. In particular, the spherical aberration caused by cover layer thickness tolerances and--more obvious--by dual-layer disks with a typical separation of approximately 20 microm between the two layers must be compensated. We propose a novel transmissive nematic liquid-crystal device, which is capable of compensating spherical aberration that occurs during the operation of optical pickup systems.     

Gradient-index microlenses: numerical investigation of different spherical index profiles with the wave propagation method

Ion-exchange microlenses are available with different gradient-index profiles. We investigate the dependence of the imaging properties on the steepness of the index profiles. Therefore we model the index distribution by the Fermi function as radial distribution with spherical symmetry. The results are compared to index profiles according to the Doremus model.     

Release of components from a plastic container during microwave heating

A thermoformed, microwavable container made from a polypropylene/Saran®/polypropylene coextruded material was selected as the test container. Samples of the specimen were microwaved in sealed glass vials for periods ranging from 3 to 7 min. After heating, the head space of the vials was sampled and analysed. The microwaving process was carried out in an Amana Radarange® microwave oven on full power. Sample surface temperature as a function of microwaving time and the quantitative identification of volatile compounds released by the polymer during microwaving were determined. Five major components were detected and quantified in the head space of the vial using gas chromatography. The quantity of each component increased with increased microwaving time. Using mass spectrometry, the five components were identified; four were hydrocarbons and the fifth was butylated hydroxytoluene (BHT). Release of organic components during brief microwaving of polymers may be a near-the-surface phenomenon.     

Characterization of microlenses by digital holographic microscopy

We demonstrate the use of digital holographic microscopy (DHM) as a metrological tool in micro-optics testing. Measurement principles are compared with those performed with Twyman-Green, Mach-Zehnder, and white-light interferometers. Measurements performed on refractive microlenses with reflection DHM are compared with measurements performed with standard interferometers. Key features of DHM such as digital focusing, measurement of shape differences with respect to a perfect model, surface roughness measurements, and optical performance evaluation are discussed. The capability of imaging nonspherical lenses without any modification of the optomechanical setup is a key advantage of DHM compared with conventional measurement tools and is demonstrated on a cylindrical microlens and a square lens array.     

气体绝对除菌用高通量氟聚物微滤膜的制备

采用气相和液相相结合的程序相转化工艺与间歇传质控制技术在连续制膜机上制备出具有实际使用价值的气体绝对除菌用高通量氟聚物微滤膜,滤膜的过滤精度为0.01μm,过滤效率为99.99995%,通气量为25 Nm3/(min·m2)(△P=0.01 MPa),膜体具有网络、絮状、圆洞多元孔结构,技术经济指标达到了国际领先水平.     

Elastic–plastic behaviour in materials loaded with a spherical indenter

Certain ceramic materials display an indentation response similar to that observed for ductile metals when loaded with a spherical indenter. This unusual behaviour, for what are nominally brittle materials, influences the mode of contact damage in applications such as machining, wear, impact damage and hardness testing. The shape of the plastic zone beneath the indenter is typically fully contained within the circle of contact on the specimen surface and thus conventional hardness theories, such as the popular expanding cavity model, provide an inadequate account of indentation response of the material. The present work demonstrates, by experiment, finite element modelling and theoretical considerations, that the indentation response is determined by the interaction between the evolving plastic zone and the mechanical properties of the specimen material, in particular, the ratio of the elastic modulus to the yield stress. This revised version was published online in November 2006 with corrections to the Cover Date.     

新型塑性加工制备球形孔多孔金属及其性能

将铝板塑性加工成半球孔层金属结构薄层,以此为基本单元按一定方式连接形成球形孔多孔金属,研究了孔结构对球形孔多孔金属性能的影响.结果表明,平板层相连的球形孔结构,使其强度高于同样条件下堆积的空心金属球结构.这种新型球形孔多孔金属的强度较高,能够有效地吸收能量,铝板的厚度和孔隙率对其压缩和能量吸能性能有明显的影响.     

Theory of spherical holographic gratings recorded by use of a multimode deformable mirror

We present the theory of spherical holographic gratings recorded by use of a deformable plane mirror and consider its application to the optimized Rowland Mounting. We illustrate the efficiency of such a mounting by computing two high-resolution gratings (3800 grooves/mm) with f/24 and f/10 apertures.     

Preparation of spherical zirconium salt particles by homogeneous precipitation

Spherical basic zirconium sulphate particles were prepared by homogeneous precipitation in mixed solutions of zirconium sulphate and urea. Values of [SO ₄ ^2– ]/[Zr⁴⁺] and [urea]/[Zr⁴⁺] in starting mixed solutions and cooling rate may affect the formation of spherical particles. Complexes such as [Zr(OH)_n]^4–n could prevent the formation and thus lead to gel precipitation. In addition, spherical particles could only be obtained in the presence of SO ₄ ^2– ; for NO^3– and Cl^–, only gel precipitation occurred.     

Refractive-index measurement of gradient-index microlenses by diffraction tomography

Diffraction tomography is applied to reconstruction of the gradient-index distribution of planar gradient-index microlenses, fabricated by thermal ion exchange. Measurements of the single-phase projections are performed by phase-shifting interferometry For reconstruction, the Rytov approximation for smooth inhomogeneities is applied. Results are compared with measurement results from other methods and simulation results.     

Capillary extrusion flow of a fluoropolymer melt

The capillary extrusion-forming flow of a fluoropolymer (FEP) melt was studied both experimentally and numerically. The excess pressure drop due to entry (related to the Bagley correction), the compressibility, and the effect of pressure and temperature on viscosity on the capillary data analysis have been examined. Using a series of capillary dies having different diameters, D, and length-to-diameter L/D ratios, a full rheological characterization has been carried out, and the experimental data have been fitted both with a viscous model (Cross) and a viscoelastic one (the Kaye—Bernstein, Kearsley, Zapas/Papanastasiou, Scriven, Macosko or K-BKZ/PSM model). For the viscous model, the viscosity is a function of both temperature and pressure. For the viscoelastic K-BKZ model, the time-temperature shifting concept has been used for the non-isothermal calculations, while the time-pressure shifting concept has been used to shift the relaxation moduli for the pressure-dependence effect. It was found that the viscous simulations gave good results in the range of apparent shear rates studied. The viscoelastic simulations gave slightly better results in reproducing the experimental data, especially for the entrance pressure losses for L/D?=?0. It is concluded that pressure-dependence of the viscosity and viscoelastic effects are small to moderate in flow of the FEP melt, which is a linear polymer.