Angular aperture

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

Mirror arrangement for a beam path in a multiple-reflection measuring cell

Abstract: The invention is directed to a mirror arrangement for a beam path in a multiple-reflection cell for measuring the absorption of light in a measuring gas. In the measuring arrangement, an entrance aperture is imaged on an exit aperture via an entrance aperture mirror, a field mirror and an exit aperture mirror. This arrangement is improved in that the astigmatism of the imaging error is considerably reduced. For this purpose, the form of the aperture mirrors is approximately defined by an ellipsoid wherein the focal point spacing is approximately equal to half the distance between the entrance aperture and the exit aperture.

Apparatus and method for measuring a wavefront using a screen with apertures adjacent to a multi-lens array

Abstract: A wavefront sensor is provided to determine characteristics of an incoming distorted energy beam, such as a tilt angle and/or a degree of focus. The sensor includes a multi-lens array, a screen, and a beam detector. The multi-lens array focuses the energy beam to a multiple focal points. The screen, positioned adjacent to the multi-lens array, has at least one aperture to allow a portion of the energy beam to pass, while blocking the remainder of the energy beam from arriving at the multi-lens array. Each aperture is aligned with a lens of the multi-lens array. The beam detector detects the resulted focal point(s) of the energy beam passing through the corresponding aperture(s) and determines the characteristics of the passing energy beam. The screen may include a central aperture to measure a local tilt angle of a segment of incoming wavefront entering a lens of the lens array. The screen may also include a plurality sets of apertures configured to align in a plurality of directions, each set of apertures measuring a degree of focus of the incoming wavefront along the corresponding direction. The screen may further include a combination of central aperture and a plurality sets of apertures aligned in a plurality of directions to simultaneously measure the local tilt angle and degree of focus of the incoming wavefront.

Fresnel region fields of circular aperture antennas

Abstract: A different approach to the Fresnel region fi eld approximation i in t roduced. Instead of using t he conventional t run cated power series expansion approximation, thc Ne wto n's iteration formula for square root is used. By using such an app roximation for circular a pertures with tapered illumination of the form (112)\", the Fresnel r egion fields can finally be expressed in terms of a new class of function s Woe')', u). The function wg is s hown to be related to th e Lomm el's funcLion s of two variables, and the fun ction Wo is then obtained from the fun ction TVOl by a simple recurre nce relationsh ip. Fi eld dist ribu t ions for n = O, 1, 2, 3, 4 and at distances}~ D2/A, ~ D2,'A, Y:l D2jA, D2/A, 2D2/A, \"\" have been com puted and prese nted as sets of curves. General and qu antitative properti es of the fi elds are clearly demonstrated by t hese curves. It i~ a lso shown that the fi eld of any other nonuni form illumination with circular symm etry can be ex pressed in term s of t he fi elds of t he basic i ll umination of the form (1 12) \".

Super wide-angle lens system and image-capturing device using the same

Abstract: In order to provide a fast super wide-angle lens system having the f-number of f/2.8 and a wide angle of view of 2ω=100° or more in an imaging area of a digital camera and an image-capturing device equipped with the super wide-angle lens system. The lens system includes, in order from an object, a first lens group G 1 having negative refractive power, an aperture stop S, and a second lens group G 2 having positive refractive power, and the lens system satisfies predetermined conditional expressions.

Antenna - aperture distributions from holographic type of radiation-pattern measurement

Abstract: Two methods are presented for determining antenna aperture distributions from the magnitudes (moduli) of radiation patterns. Antennas under test are measured in the presence of fixed-reference antennas. Invoking the principle of holography, the radiation-pattern measurements are arranged so that all the required information can be obtained without having to make any phase measurements. The methods are illustrated with laboratory experiments, performed with acoustic antennas, for which the aperture distributions are determined to an estimated accuracy of within 5%.