Angular aperture

About: Angular aperture is a research topic. Over the lifetime, 1771 publications have been published within this topic receiving 27257 citations.

Antenna beam patterns which retain shape with defocusing

Abstract: A narrow beam is formed by radiation from a large aperture having a flat phase front. Any curvature of the phase front, as by defocusing, causes widening of the beam and reduction of the directive gain. Certain symmetric and antisymmetric forms of aperture excitation, based on the probability function, have been known to yield radiation patterns of the same shape. It is found that these patterns retain their shape when widened by defocusing, so that the effects of defocusing can be expressed by simple and exact formulas. Also they retain some ideal relations that are peculiar to their use as sum and difference patterns in a tracking radar of the simultaneous-lobing or monopulse type. The simplification results from the fact that the attenuation for tapering the aperture excitation, and the phase shift by defocusing, are both proportional to the square of the aperture coordinates from the center. The amount of defocusing is then expressed by the constant ratio of these two quantities in radians per napier. While these forms ideally require a line or circle aperture of unlimited extent, they can be approximated with an aperture of finite extent. Therefore the resulting simple concepts and rules are helpful in practical situations.

Illumination assembly including a rigid light-guiding element incorporating a numerical-aperture alteration taper

Abstract: An illumination assembly includes a light-emitting element that emits light over a light-source numerical aperture and an elongated light-guiding element including opposed incident and emission ends between which ends light propagates by total internal reflection. The light-guiding element includes along a portion of its length a numerical-aperture alteration taper having opposed small and large ends exhibiting, respectively, a small-end numerical aperture and a large-end numerical aperture lower in magnitude than the small-end numerical aperture. The alteration taper is oriented such that the small end is more proximate the incident end than the large end. The incident end is in light-collecting proximity and alignment with the light-emitting element such that light emitted from the light-emitting element over the small-end numerical aperture and received into the small end of the alteration taper is emitted from the emission end of the light-guiding element at an emission numerical aperture lower in magnitude than the small-end numerical aperture.

A new correction lens

Abstract: A new electrostatic lens capable of correcting third-order aperture aberration is proposed. The new lens is called a self-aligned quadrupole correction lens and consists of an electrostatic quadrupole and an aperture electrode. An octopole field component is automatically created within the quadrupole field by excitation of the aperture electrode. The potential distributions of this lens are calculated by successive over-relaxation techniques involving the numerical solution of Laplace's equation in three dimensions. Correction properties for all the aperture aberration coefficients are obtained by using the potential distributions. The aperture aberrations have been accurately measured by means of the shadow-image technique, and compared with those calculated using the above potential distributions. It was confirmed experimentally that the aberration in the convergent plane can be cancelled completely by the new correction method.

Microscope objective with ball lens and protection plate

Abstract: An objective lens system with protection glass for a microscope and having a numerical aperture of 1.25 and using an immersion oil, having a first, second, third and fourth lens groups, the first lens group being a plano-parallel plate cemented to a hemispherical lens, the second lens group being one aplanatic meniscus, the third lens group being three cemented doublets, and the fourth lens group being two lens components including a positive and a negative meniscus component which are arranged with their concave surface opposite each other. The objective lens system has a relatively small number of lens components, and the aberration, especially chromatic, spherical, coma, astigmatic difference and curvature of field, are corrected favorably.

Imaging lens with high resolution and short overall length

Abstract: An exemplary imaging lens includes, in this order from the object side to the image side thereof, a first lens of positive refraction power, a second lens of negative refraction power, a third lens of positive refraction power, and a fourth lens of negative refraction power. The imaging lens satisfies the formulas of: (1) 1 15 and (3) R7>0, R6<0, where T is the overall length of the imaging lens, F is the effective focal length of the imaging lens, R3 is the radius of curvature of the object-side surface of the second lens, R6 is the radius of curvature of the image-side surface of the third lens, and R7 is the radius of curvature of the object-side surface of the fourth lens.