Parabolic reflector

About: Parabolic reflector is a research topic. Over the lifetime, 3375 publications have been published within this topic receiving 30735 citations. The topic is also known as: paraboloid reflector & paraboloidal reflector.

Performance of the Far Ultraviolet Spectroscopic Explorer mirror assemblies

Abstract: The Far Ultraviolet Spectroscopic Explorer is a NASA astrophysics satellite which produces high-resolution spectra in the far-ultraviolet (90.5-118.7 nm bandpass) using a high effective area and low background detectors. The observatory was launched on its three-year mission from Cape Canaveral Air Station on 24 June 1999. The instrument contains four coaligned, normal incidence, off-axis parabolic mirrors which illuminate separate Rowland circle spectrograph channels equipped with holographically ruled diffraction gratings and delay line microchannel plate detectors. The telescope mirrors have a 352 x 387 mm aperture and 2245 mm focal length and are attached to actuator assemblies, which provide on-orbit, tip, tilt, and focus control. Two mirrors are coated with silicon carbide (SiC) and two are coated with lithium fluoride over aluminum (Al:LiF). We describe mirror assembly in-flight optical and mechanical performance. On-orbit measurements of the far-ultraviolet point spread function associated with each mirror are compared to expectations based on pre-flight laboratory measurements and modeling using the Optical Surface Analysis Code and surface metrology data. On-orbit imaging data indicate that the mirrors meet their instrument-level requirement of 50 percent and 95 percent slit transmission for the high- and mid-resolution spectrograph entrance slits, respectively. The degradation of mirror reflectivity during satellite integration and test is also discussed. The far-ultraviolet reflectivity of the SiC- and AlLiF-coated mirrors decreased about six percent and three percent, respectively, between coating and launch. Each mirror is equipped with three actuators, which consist of a stepper motor driving a ball screw via a two-stage planetary gear train. We also discuss the mechanical performance of the mirror assemblies, including actuator performance and thermal effects.

Simulation of a cylindrical reflector by conducting circular cylinders

Abstract: A cylindrical reflector is simulated by N parallel circular conducting cylinders of arbitrary radius and distribution along the trajectory of the continuous reflector surface. The resulting radiation pattern of the transmitting reflector antenna is computed as the backscattering pattern of the circular cylinders due to a line source excitation. The results for large N are compared with published data for a cylindrical parabolic reflector by Kinzel and for a corner reflector by Tsai. It is shown that the beamwidth and first sidelobe level can be improved by using cylinders of unequal radii and spacing but that, contrary to expectation, further improvement by increasing the number of cylinders is not necessarily possible.

Motor vehicle headlamp comprising a parabolic reflector with modified base

Abstract: A motor vehicle headlamp, of the type capable of creating a main beam, and a dipped beam limited by a cutoff, comprises two axial filaments 11, 12 aligned on the optical axis Ox of the headlamp, and acting as light sources respectively for the main beam and for the dipped beam, a reflector 200 and a closure glass 30. According to the invention, the reflector is divided into two lateral zones 202, 203 and a central zone 201, the lateral zones are paraboloid portions whose foci Fo are situated on the optical axis between the two filaments, the central zone is a zone which reflects the light rays emitted by the filament so that they converge in a region substantially distant from the closure glass, and the central zone and the lateral zones are connected with continuity in two substantially vertical planes situated on either side of the optical axis of the headlamp. Application to attenuating the intensity of the dipped beam at the centre of the glass, and to spreading the beam sideways.

Off-axis mirror based optical system design for circularization, collimation, and expansion of elliptical laser beams

Abstract: In this paper, we present two optical system design methods for beam circularization, collimation, and expansion of semiconductor laser output beam for possible application in LIDAR systems. Two different optical mirror systems are investigated: an off-axis hyperbolic/parabolic mirror system and an off-axis parabolic mirror system. Equations specific to these mirror systems are derived and computer package programs such as ZEMAX and MATLAB are used to simulate the optical designs. The beam reshaping results are presented.