Topic
Lens (optics)
About: Lens (optics) is a research topic. Over the lifetime, 156482 publications have been published within this topic receiving 1244415 citations.
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TL;DR: In this article, an inversion method was used to reconstruct the image of the object without the need for any such prior knowledge, without the knowledge of the shape of the objects and the low spatial frequencies unavoidably lost in experiments.
Abstract: A solution to the inversion problem of scattering would offer aberration-free diffraction-limited three-dimensional images without the resolution and depth-of-field limitations of lens-based tomographic systems. Powerful algorithms are increasingly being used to act as lenses to form such images. Current image reconstruction methods, however, require the knowledge of the shape of the object and the low spatial frequencies unavoidably lost in experiments. Diffractive imaging has thus previously been used to increase the resolution of images obtained by other means. Here we experimentally demonstrate an inversion method, which reconstructs the image of the object without the need for any such prior knowledge.
787 citations
TL;DR: In this article, a planar lens without chromatic aberrations at three wavelengths is presented, which is based on low-loss dielectric resonators which introduce a dense spectrum of optical modes to enable dispersive phase compensation.
Abstract: The replacement of bulk refractive optical elements with diffractive planar components enables the miniaturization of optical systems. However, diffractive optics suffers from large chromatic aberrations due to the dispersion of the phase accumulated by light during propagation. We show that this limitation can be overcome with an engineered wavelength-dependent phase shift imparted by a metasurface and demonstrate a design that deflects three wavelengths without dispersion. A planar lens without chromatic aberrations at three wavelengths is also presented. Our design is based on low-loss dielectric resonators which introduce a dense spectrum of optical modes to enable dispersive phase compensation. The suppression of chromatic aberrations in metasurface-based planar photonics will find applications in lightweight collimators for displays, and chromatically-corrected imaging systems.
773 citations
TL;DR: In this article, Bernhard et al. proposed that the function of this structure might be to suppress reflexions by effectively proving a graded transition of refractive index between the air and the cornea.
Abstract: THE problem of surface reflexion from lenses has led1 to the development of multilayer interference structures which can suppress the reflexion from glass surfaces by a factor of 10 or more throughout the visible spectrum. But observations on the corneas of nocturnal insects indicate that nature may have anticipated the problems2. Electron microscope studies of the corneal lenses of moths reveal that the outer surface is covered in a regular array of conical protuberances, typically of about 200 nm height and spacing. Bernhard2 proposed that the function of this structure might be to suppress reflexions by effectively proving a graded transition of refractive index between the air and the cornea. The proposal was substantiated by measurements with microwave radiation reflected from a model of the array, scaled up appropriately for the longer wavelengths.
769 citations
TL;DR: In this paper, a two-dimensional microwave lens with a straight front face was used to generate fractional degree beams, which can operate at very short pulse lengths and can scan more beamwidths than any previously known device of its type.
Abstract: A new "time-delay" scanner consists of a constrained wide-angle two-dimensional microwave lens with a straight front face in which lens elements connect arbitrary points on the inner and outer contours. The lens can operate at very short pulse lengths and can scan more beamwidths than any previously known device of its type. A phase analysis shows that this design has very small coma aberrations and that the lens can generate fractional degree beams. Criteria developed for selecting optimum lens parameters are given. The radiation patterns of an experimental model in which the lens elements consist of coaxial cables show the expected wide-angle characteristics. In further tests incremental scanning was obtained through the use of phase shifters in the coaxial lens elements. The design of symmetrical three-dimensional lenses is briefly discussed. A table of lens contour parameters is given for an optimum lens design with scan angle \alpha of 30\deg .
758 citations
TL;DR: Some time ago, R. W. Mandi paid me a visit and asked me to publish the results of a little calculation, which was made at his request, and this note complies with his wish.
Abstract: Some time ago, R. W. Mandi paid me a visit and asked me to publish the results of a little calculation, which I had made at his request. This note complies with his wish.
755 citations