Lens of electrically controllable focal length made by a glass lens and liquid-crystal layers

A variable-focus lens is made with one or two liquid-crystal layers and a glass lens. The lens has an aperture near that of the glass lens, and its focal length is electrically changeable from that of the glass lens. The principle is described, and the lens is demonstrated experimentally.     

Lens based on the use of left-handed materials

A new lens that is a modification of the Veselago lens is proposed. It consists of a slab of the left-handed material embedded into a regular material. The materials for the new lens should have the same refractive index, unlike that of the Veselago lens in which the materials should in addition have the same impedance. Therefore the new lens should be easier to manufacture. As the Veselago lens, the new lens might be useful for the three dimensional imaging. In contrast to the Veselago lens the new lens has multiple foci, and it may image an object that is located at any large distance from the slab.     

Harmonic diffractive lenses

The harmonic diffractive lens is a diffractive imaging lens for which the optical path-length transition between adjacent facets is an integer multiple m of the design wavelength λ(o). The total lens thickness in air is mλ(o)/(n - 1), which is m times thicker than the so-called modulo 2π diffractive lens. Lenses constructed in this way have hybrid properties of both refractive and diffractive lenses. Such a lens will have a diffraction-limited, common focus for a number of discrete wavelengths across the visible spectrum. A 34.75-diopter, 6-mm-diameter lens is diamond turned in aluminum and replicated in optical materials. The sag of the lens is 23 μm. Modulation transfer function measurements in both monochromatic and white light verify the performance of the lens. The lens approaches the diffraction limit for 10 discrete wavelengths across the visible spectrum.     

Improvement of chromatic aberration of a plastic rod lens array. 1. Combination-color lens arrays consisting of several kinds of rod lenses with different gradient constants and different color filter functions

We propose a new type of rod lens array with improved chromatic aberration. The new rod lens array consists of several kinds of rod lenses with different gradient constants and different color filter functions. The gradient constant of each lens was prepared such that the total conjugate length was identical to the specific wavelength of the lens with a constant lens length. We call our new type of rod lens array a combination-color lens array. The characteristics of this color-type lens array are as follows: high angular aperture, short focal length, and ease of production with established procedures. The optical resolution of the rod lens array is 300 dpi in a wide wavelength range that is high enough to be applied to color scanners.     

Nested shell optical model of the lens of the human eye

A nested shell model of the human lens is developed based on the known anatomical construction of the lens, on the known way in which the lens grows throughout its life, on the measured characteristics of the lens surfaces as a function of the age of the lens, on the measured changes in the shape of the lens during accommodation, and on measured material characteristics of the lens materials, such as density and index of refraction throughout. The observed changes in central surface curvature and thickness force the shell thicknesses to vary in a predictable way and in turn force the shell surface asphericity to take certain values. Thus, in addition to giving the shape of each shell, the model predicts the change expected in the asphericity of the lens surfaces as the lens ages and adds cortical cell layers. Two examples are given, one for a 25-year-old lens and one for a 40-year-old lens, to show how the cortical layers change their shapes throughout the cortex and over time as the lens ages. The performance of the model of this paper is compared to that of two other nested shell models, one where the layers have constant thickness and one where the lens posterior is fixed within the eye over time, to show the superior performance of this model with respect to maintaining a constant refractive error for the eye as the lens ages and grows.     

Colliding shock lens as an intracavity Q-switch element

We show how a varifocal pulsed gas lens, the colliding shock lens, can be used as an intracavity element to Q switch a ruby laser. By placement of the shock lens in tandem with a second lens, a giant pulse is obtained. The second lens may be a conventional glass lens or a continuous-wave gas lens.     

A combined electrostatic lens

With a view to increasing the intensity of charged particle beams, a combined electrostatic lens consisting of three coaxial cylinders has been theoretically studied. The proposed lens is capable of focusing both paraxial beams (by an axisymmetric lens) and nonparaxial beams (by a coaxial cylindrical lens). The parameters of this combined lens have been evaluated by numerical methods. The gain in the beam intensity provided by the proposed lens in comparison to the widely used single axisymmetric lens is determined.     

Modified integrated optic Fresnal lens for waveguide-to-fiber coupling

The traditional design procedure for the waveguide Fresnel lens was carried over from those of bulk optics and micro-optics. In this design it is assumed that the lens thickness is negligibly small with respect to the focal length. This criterion does not hold for many integrated optic devices, in particular those with small mode-index modulations and long wavelengths. Under these conditions, the focal properties of the lens become unpredictable and the lens efficiency is reduced, both of which severely limit the usefulness of the lens as a waveguide-to-fiber coupler. To correct for this shortcoming, the standard Fresnel lens design procedure was modified to acocunt for the thickness of the lens explicitly. Both the standard and the modified Fresnel lens designs are outlined. A comparison of the limitations of the two lenses predicts better performance for the modified Fresnel lens. This is supported through computersimulation results for a pair of test lenses.     

Characteristics of the thick,compound refractive lens

A compound refractive lens (CRL), consisting of a series of N closely spaced lens elements each of which contributes a small fraction of the total focusing, can be used to focus x rays or neutrons. The thickness of a CRL can be comparable to its focal length, whereupon a thick-lens analysis must be performed. In contrast with the conventional optical lens, where the ray inside the lens follows a straight line, the ray inside the CRL is continually changing direction because of the multiple refracting surfaces. Thus the matrix representation for the thick CRL is quite different from that for the thick optical lens. Principal planes can be defined such that the thick-lens matrix can be converted to that of a thin lens. For a thick lens the focal length is greater than for a thin lens with the same lens curvature, but this lengthening effect is less for the CRL than for the conventional optical lens.     

Measurement of parameters of simple lenses using digital holographic interferometry and a synthetic reference wave

The use of digital holographic intrerferometry in the testing of simple thin lenses is explored. Focal length, radius of curvature, and refractive index are the lens parameters that can be determined using this method. The digital holograms using the lens under test are recorded at various positions of the test lens using off-axis geometry. This is combined with a digitally computed plane wavefront to determine the curvature of the light beam emerging from the test lens. Focal length is the position of the test lens where a single fringe results. The radius of curvature of the test lens is also determined similarly using a long focal length lens to concentrate a collimated beam onto the test lens. The nonuniformities on the lens surface could also be found by using this method. The implementation of the method is shown by using computer simulations in the case of biconvex lenses. The method can be utilized to measure the parameters of plano-convex and concave lenses also.     

镜片全自动测量系统的研究

为了提高镜片焦度测量的精度和效率,针对镜片测量时因手动调节而存在镜片偏心等问题,提出了一种结合哈特曼检测法、机器视觉技术以及步进电机控制系统来测量镜片的技术方案.基于此方案设计并制作了一种镜片全自动测量系统.系统实现了对哈特曼光阑下多光斑实时大小和位置的分析,利用搭建的机械模块自动校准镜片位置并测量镜片.用-15m-1...     

Computer Generated Diffractive Multi-focal Lens

The method has been proposed for computing Fresnel-type multi-focal lenses on the basis of special-type phase nonlinearity. A multi-focal lens is represented as a mathematical superposition of a thin lens and nonlinearity distorted Fresnel lens. Selection of the nonlinearity type is reduced to the problem of the groove form determination for the phase diffraction grating with pre-set energy distribution between orders. In particular, bi-focal lens and seven-focal lens have been investigated.     

Panoramic lens

An infrared panoramic lens system that utilizes two lens groups to project a full 3600 cylindrical field of view onto a two-dimensional annular format is described. Each lens group has its well-defined role. The first group is a lens block that converts a cylindrical field of view into a two-dimensional annular format located within the lens itself, and the second group relays this image to some accessible location downstream from the optical system.     

Studies on the diffraction image of a thermal lens

We calculated the intensity distribution behind a thermal lens by using a numerical quadrature of the Fresnel diffraction integral and compared it to several given approximate models for laser light detection in the center behind a thermal lens, which includes a new approximate solution of the diffraction integral with applicability to strong thermal lenses. Consideration of the aberrant nature of the thermal lens is crucial even if the thermal lens is weak. A simple approximate formula for the position of the most intense interference ring stating a linear dependence of the thermal lens strength is given. The transverse profile of a weak thermal lens is discussed. It is shown that spherical aberration modifies the central intensity even if a Gaussian profile is observed.     

New Design of High NA Photolithographic Lens Using Diffractive Optical Element

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Liquid-crystal lens with a focal length that is variable in a wide range

A liquid-crystal (LC) lens driven by two voltages is reported. The lens has a focal length that is electrically tunable. The range of the variable focusing power is very wide, covering approximately 0.8-10.7 D. In the entire focal range the LC lens maintains high optical quality. The LC lens can be driven in a simple way to prevent the occurrence of a disclination line. The use of the LC lens in image formation is demonstrated.     

Patch-fed planar dielectric slab waveguide Luneburg lens

The design of a patch-fed planar dielectric slab waveguide Luneburg lens weighing only 45 g and operated at 27 GHz in TM₀ mode is described. The measured half-power beamwidth (HPBW) for a 10.8 lambda, 12-cm diameter lens fed by a microstrip patch placed in intimate contact with the lens rim is 6.9deg with 16.8 dB gain and 10% bandwidth for -10 dB feed return loss, lens cross-polar levels were below -20 dB. The lens is also capable of operating in the TE₀ mode with similar radiation performance to that of the TM₀ mode. Here, measured HPBW and gain is 8 and 15.5 dB at 27 GHz. Unlike other planar lens arrangements, because of its ability to handle both TM₀ and TE₀ modes the lens has the potential to deal with the circularly polarised signals, this aspect is also explored.     

Design of a double-sided telecentric zoom lens

A method is presented for the calculation of paraxial design parameters of a double-sided telecentric zoom lens with easy variation of the magnification range. The telecentric lens consists of a zoom lens with a fixed distance between focal points and a lens with a fixed focal length. The third-order aberration analysis is also performed, and spot diagrams are calculated for two f-number values.     

Self-centering of a ball lens by laser trapping: fiber-ball-fiber coupling analysis

Fiber-to-fiber coupling through use of a laser-trapped microball lens is examined. A model based on radiation pressure predicts that the ball lens will align axially between the fiber endfaces. Laser manipulation of the ball lens axial position results in a configuration in which the ball lens optically bridges the gap between the fibers. Experimental results are presented for several fiber endface separations, and it is found that the presence of the microball lens can increase the coupling by a factor of 2 above the level expected by direct fiber-to-fiber coupling for the same fiber endface separation.