Showing papers on "Parabolic reflector published in 1987"

High‐frequency expression for the field in the caustic region of a cylindrical reflector using Maslov's method

Abstract: High-frequency expressions in the caustic region are derived for the wave reflected by a circular and a parabolic cylindrical reflector using Maslov's method when a plane wave is incident obliquely. Maslov's method is a systematic procedure for predicting the field in the caustic region combining the simplicity of ray and generality of the transform method. Numerical computations are made for the field pattern around the caustic or cusp region and the variation of peak positions of the reflected field with respect to the incident angle.

Geometrical aberration of a generalized Wolter type I telescope.

Abstract: Using two hyperboloids, we can control spherical aberration and coma of an imaging x-ray telescope. The coma-free condition is satisfied only at a particular radius of the first mirror. The best performance is obtained when we allow the coma-free condition at the outer edge and cancel about half of the defocused image for the largest height of an object by introducing spherical aberration.

Cone shaped fresnel reflector

Abstract: A Fresnel-type reflector having the physical shape of a cone. In a preferred embodiment, the reflector is made by forming a reflective coating on a structured surface of a thin flexible film and forming the film into the shape of a cone. The structures on the surface are designed to cause the reflector to imitate the optical properties of a parabolic reflector when the reflector of the invention is formed into the shape of a cone.

Reading head in integrated optics for reading information recorded on a magnetic support

Abstract: The head comprises a light source (S), a polarizer (P), a parabolic mirror (MP1), a second parabolic mirror (MP2), a polarization converter grating (RCP), a reflector (M), a separating plate (LS) and a detector (D). The beam diffracted by (RCP) constitutes a reference beam and the beam which has passed through (RCP) an analysis beam. The interference state of these two beams is dependent upon the orientation of the magnetization of the support to be read.

Holographic aspheric gratings printed with aberrant waves

Abstract: In astrophysics, holographic gratings use, as far as possible, spherical grating's surface and printing laser waves. However, to obtain high spectral resolution, aberrations must be corrected up to the fourth degree, which generally requires aspheric surfaces for the grating or the laser waves. To date, technological progress makes the fabrication of such gratings possible, so we have developed a complete theory of these deformations and have written a computer program which we believe solves any grating's aberration problems.

Optical interface for a magneto-optical current transducer

Abstract: A magneto-optical current measuring device includes a collimating lens arrangement for focusing a light signal into a parallel beam of light, which beam of light, when polarized is communicated through a Faraday rotator which is disposed in surrounding proximity to the transmission line in which it is desired to measure the current flow. The collimating lens element is formed of a segment of a parabolic lens and a spacer lens element which has a flat surface formed by an edge opposite the parabolic surface, this flat surface extending to the focal length of the parabolic surface. The collimating lens element is constructed in the manner of a monolithic configuration and is then secured together with the polarizing element to the Faraday rotator in a manner so as to eliminate all air-to-glass interfaces.

Laser curtain having an array of parabolic mirrors each focusing radiation on a corresponding detector positioned in mirror's focal point

Abstract: A laser beam fanned into a triangular plane configuration by mirrors, succeeding additional mirrors focusing the laser curtain rays back onto a spot, the spot having a light detecting, electrical transmitting element such that a square wave pulse is generated as the laser timely sweeps the collecting mirror, a breach in the square wave occurring when the laser ray curtain is penetrated breaking a laser beam, thus said penetration being detected, a system of three laser curtains in X, Y, and Z coordinates, having means of traversing an object to be measured, determining the exterior of each of its six sides.

Light absorption analyser

Abstract: A light absorption analyzer can work in either a reflection or a transmission mode, according to which probe head is fitted to it. Light is caused to be of a desired wavelength for the analysis by passing non-monochromatic light from a high-intensity flash tube source (which is not a point source) to an interference filter. Only parallel light emanating from the filter is focused by a concave parabolic mirror on a point where at least one fibre-optic collector is positioned. This light can then be passed directly to the probe for passage through the sample, since it is only light of a specified wavelength which will have travelled parallel from the filter and will therefore be focused at the point. Some of the light is taken off a reference detector to provide a reference signal for comparison with that derived from a test detetor fed by a return fibre-optic from the probe. A comparator is programmed to give a quantitiative readout of the absorption by the test sample.

Clip fasteners for parabolic dish reflector panels

Abstract: A parabolic reflector having support structure, preferably mounted on wheels for rotation, for supporting a dish framework to which is mounted a multiplicity of adjacently placed reflector members for focusing solar rays on a linear collector. The reflector members are in the form of sheets having the shape of funnel sections, i.e., infundibuliform, to provide a reflective concave surface. Each of the reflector members define slots which are aligned with and adjacent like slots of adjacently placed reflector members for receiving bendable tabs of clip fasteners. The clip fasteners, besides serving to securely connect adjacent reflector members, also include apertures for receiving rivets or other fasteners for attachment to the underlying parabolic framework. The clips include a reflective surface for maximizing reflector efficiency. The linear collector includes a cylindrical, elongated shell for receiving focused solar rays. Heat exchange media flows upward into the collector through a central tube which is separated from the exit passage adjacent the shell by means of solid insulative material to prevent heat exchange between the incoming and exiting heat exchange media.

Dual band feed system

Abstract: A dual frequency band microwave antenna feed for a parabolic reflector has a circular waveguide for a low frequency band and a smaller circular waveguide for a higher frequency band disposed in and concentric with the low band guide. A twisted conductive baffle is disposed in each guide to permit 90° rotation of linearly cross-polarization signals and a pair of in-line ports is attached to each guide for output of such pairs of cross-polarization signals.

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.

Parabolic reflector antennas and method of making same

Abstract: A method is provided for manufacturing a parabolic reflector antenna carried by a parabolic support made from an appropriate insulating material. The method of the invention includes in combination the following steps: levelling out or smoothing the irregularities of the surface of said support by application of an appropriate levelling means, such as a lacquer or a polymer film or similar, total metallization of this surface thus levelled by metal deposition under a vacuum, forming of a mask or screen having orifices corresponding to the elements of the desired grid, interpositioning of this mask between an appropriate laser source and a focusing lens, focusing of the laser beam emitted by this source on the metallized surface of the reflector by following the contours of the orifices formed in the mask, scanning of the surface of the reflector by means of the laser beam for cutting out said grid therein, compensation of the variations of distance between the surface of the parabolic reflector and the laser source, and thus the focusing optics of the laser beam emitted thereby, during scanning of this surface.

New main reflector, subreflector and dual chamber concepts for compact range applications

Abstract: A compact range is a facility used for the measurement of antenna radiation and target scattering problems. Most presently available parabolic reflectors do not produce ideal uniform plane waves in the target zone. Design improvements are suggested to reduce the amplitude taper, ripple and cross polarization errors. The ripple caused by diffractions from the reflector edges can be reduced by adding blended rolled edges and shaping the edge contour. Since the reflected edge continues smoothly from the parabola onto the rolled surface, rather than being abruptly terminated, the discontinuity in the reflected field is reduced which results in weaker diffracted fields. This is done by blending the rolled edges from the parabola into an ellipse. An algorithm which enables one to design optimum blended rolled edges was developed that is based on an analysis of the continuity of the surface radius of curvature and its derivatives across the junction. Futhermore, a concave edge contour results in a divergent diffracted ray pattern and hence less stray energy in the target zone. Design equations for three-dimensional reflectors are given. Various examples were analyzed using a new physical optics method which eliminates the effects of the false scattering centers on the incident shadow boundaries. A Gregorian subreflector system, in which both the subreflector and feed axes are tilted, results in a substantial reduction in the amplitude taper and cross polarization errors. A dual chamber configuration is proposed to eliminate the effects of diffraction from the subreflector and spillover from the feed. A computationally efficient technique, based on ray tracing and aperture integration, was developed to analyze the scattering from a lossy dielectric slab with a wedge termination.

The formation of optical membrane reflector surfaces using uniform pressure loading

Abstract: Potentially high quality optical reflector surfaces are attainable with the use of pressure formed membranes. Such reflector surfaces offer the prospect of very low weight and low cost. The formation of such surfaces, using initially flat circular membranes with uniform pressure loading, is studied in this paper. Finite axisymmetric deformations, along with both linear and nonlinear material response is considered. A wide range of focal-length-to-diameter ratios (above 0.6) are addressed and the structural/optical response mechanisms that lead to optical distortions relative to ideal parabolic reflector shapes are also considered. Results show that elastic material response can often lead to a significantly larger deviation from the ideal shape than will inelastic material response. This results primarily from the ability to limit stress nonuniformities when inelastic material response is operative. Furthermore, when under pressure loading the membrane focal length decreases monotonically with increasing radius for both linear and nonlinear material response. Further, the predicted focal length variation is increasingly nonlinear near the membrane support.

Offset dual parabolic cylindrical reflectors employed as a compact range

Abstract: Compact ranges using dual parabolic cylindrical reflectors are investigated, and the dependence of the aperture field on the feed pattern and system geometrical parameters is studied. A uniformity factor is defined to indicate the aperture field uniformity and the significance of the diffracted fields is explored. Offset configurations are also considered and studied. It is shown that their feed location and orientation can be optimized to minimize the geometrical-optics cross polarization. The effects of offset angle on the edge diffraction and aperture shape are also studied. >

Comparison of induced current and aperture field integrations for an offset parabolic reflector

Abstract: The fields predicted by integration of the physical optics induced currents on the reflector (ICM) and the geometrical optics aperture fields (AFM) on the surface that caps the reflector are compared numerically for offset parabolic reflectors. It is found that the AFM solutions are very close to ICM solutions for the main beam and the first few sidelobes but discrepancy remains for the far-out sidelobes. This discrepancy is found to come mainly from the difference of polarization matrix for each method.

Sidelobe reduction of a parabolic reflector with auxiliary reflectors

Abstract: Reducing the sidelobe level of a reflector antenna in a particular direction is desirable in many applications. A simple way of achieving this reduction is to add auxiliary reflectors either internally over the main reflector surface or externally outside the main reflector surface. Design curves are presented on the size of these auxiliary reflectors versus feed taper and F/D to achieve a prescribed sidelobe reduction. Typically, for a 10 dB sidelobe reduction, the diameter of the auxiliary reflector is about a third of the main reflector diameter (10 percent in surface area).

Headlamp for vehicles

Abstract: A headlamp for vehicles has a lens and a parabolic reflector which are made of synthetic resin and which are joined together by heat. A composite, light scattering reflector for scattering or spreading the light to be concentrated to the upper and central portion of the lens to an extend that no glare is generated, is arranged at the upper and central portion of the parabolic reflector. The composite reflector may be integrally formed with the main parabolic reflector, or may be a separate element joined to the main parabolic reflector.

Image expanding apparatus

Abstract: An optical toy image generator of the present invention comprises a parabolic reflector having a central opening for movable receipt of an image bearing shaft. The image bearing shaft contains a distorted representation which will appear on the shiny mirrored surface of the reflector as a dynamic changing proper image to the viewer who is facing the reflector's parabolic surface.

A Grinding Apparatus For Making A Middle-Size Parabolic Mirror Using The Link Mechanism Method

Abstract: A large solar furnace that has a parabolic mirror with a diameter of 10m, a focal length of 3.2m and a heliostat mirror with an area of 15x15m was made by the authors at T6hoku University in 1962, and subsequently a small solar furnace having a parabolic mirror with a diameter of 1.5m, a focal -length of 0.5m and a heliostat mirror with an area of 2x2m was constructed at T6hoku Gakuin University in 1986. The large solar furnace could melt tungsten with a melting point of 3400°C, and the small solar furnace drove a stirling engine made in West Germany that had a rated power of 400W. The parabolic mirror of the segment type at TohokU University was made by a grinding apparatus that used a cam mechanism, and the parabolic mirror at T6hoku Gakuin University was made by an apparatus (hand-made by students)which employed a link mechanism to draw the parabolic curve. In this paper, the grinding apparatus used for making the segmental parabolic mirror with a diameter of 2-3m and a focal length of 0.5-1.0 m is reported. This mirror was used in a middle-size solar heat engine. The heat engine in this system was a Stirling engine with a rated power of 1-3KW, and the grinding apparatus (the precision parts moved in a linear track ) employed a compact link mechanism.

Fabrication and testing of off-axis parabolic mirrors

Abstract: Methods have been devised to fabricate and test off-axis segments of parabolic mirrors manufactured from a parent parabolic mirror. Four off-axis parabolic mirrors were fabricated from Zerodur (special grade) by cutting up one large on-axis parabolic mirror. Interferometric measurements were made on the parent mirror and off-axis segments before and after cutting. The measurements show that the surface figure of the segments did not change as a result of the cutting. The surface figure of the final mirror segments was better than λ 13 peak-to-valley and λ 13 rms (λ = 0.6328 μm).

Compact range for variable-zone measurements

Abstract: A compact range for testing antennas or radar targets includes a source for directing energy along a feedline toward a parabolic reflector. The reflected wave is a spherical wave with a radius dependent on the distance of the source from the focal point of the reflector.

Longitudinal spherical aberration of a thick lens

Abstract: An expression for the longitudinal spherical aberration produced by a spherical refracting surface from parallel incident light in the fifth‐order approximation is derived. A simple experiment to measure the location of focal points formed by nonparaxial rays is also described. The results of the measurements are in good agreement with the theory.

Heat collection device for solar thermal engine

Abstract: PURPOSE: To improve heat collection efficiency by laying out a curved mirror before or after a focal point of a parabolic mirror and condencing into an endoergic member installed at an arbitrary opening position of the parabolic mirror. CONSTITUTION: If an attempt is made to install a curved mirror 3 before or after a focal point of a parabolic mirror 2, a solar light 1 can be collected into an arbitrary opening position 21 by selecting the properties of the curved face, the focal point and mounting direction. For example, if an attempt is made to select a parabolic face, a solar light can be condensed with a parallel light within an area identical to the diameter of a curved mirror 3, which serves to collect heat under control, say, limited to 800 to 1000 deg. C. The curved mirror 3 is supported by a support member whose lower end is fixed to a reinforcing member 5. The curved mirror, which is small in size and light in weight, is not provided with any drive unit. Therefore, this construction makes it possible to support the mirror with ease in terms of strength. As an example, an endoergic member comprises an endoergic pipe laid out in a focal line of a curved mirror, and a transparent cover which covers the outside of the endoergic pipe. The heat thus absorbed is conveyed to a heat medium for engine drive flowing within the endoergic pipe and taken out. COPYRIGHT: (C)1989,JPO&Japio

Laser beam machining device

Abstract: PURPOSE:To reduce the weight, to improve the responsibility in position controlling and to enable the working of high accuracy by enabling the laser beam irradiation from every angle with two reflection systems. CONSTITUTION:The optical axis C of a parabolic mirror 19 is coincided with the prescribed line of the body to be worked by moving the machine head 14 on which the parabolic mirror 19 is provided. The machine head 14 is rotated with its rocking and is moved as well in X axis and Z axis directions by rotating the driving motor 17 provided on the outer peripheral part of a horizontal arm 8c. With the rocking rotation of the head 14 the optical axis C is kept vertically for the working face of the body to be worked at all times in succession and also moved vertically in Z axis direction, so the focus of the laser beam is always directed for the working face. In this way, the laser beam is held vertically for the working face of the body to be worked without changing the focus at all times only with the rocking rotation of the head 14 with moving it in X axis and Z axis directions, and the laser beam machining is performed in succession.

Head lamp for automobile

Abstract: An improved vehicle headlamp for developing forward illumination and having reduced dimensions relative to prior art headlamps is disclosed. The lamp comprises an enclosed concave parabolic reflector of a rectangular cross section type and having a single tungsten-halogen light source coaxially located within the enclosed reflector. The headlamp has a glare shield arranged around the light source when the headlamp is utilized for low beam application and a heat shield located about the light source for both low and high beam applications. The light source is of a tubular shape and has a bulbous portion preferably of an ellipsoidal shape. The efficacy of the light source is improved by means of an infrared reflective coating placed on its outer surface.

Device for the mutual alignment of multicolour light beams, and optical sight comprising such a device

Abstract: The mutual alignment device is intended for an optical sight which comprises a source providing a beam of parallel light, such as the laser of a telemeter laser, to be matched with receivers. The device comprises an optical mixer (10) having at least two holes (24, 32) each illuminated by an emission in one of the spectral ranges for which the alignment has to be produced and a plate (28) for combining the emissions into a common exit beam (16) of the unit; and a parabolic mirror (12) placed so as to receive the exit beam at an angle in relation to its axis, the mixer and the mirror being constituted so that all the holes (22, 32) forming sources are at the focus of the mirror. The mixer comprises a sensor (38) which is sensitive in the emission range of the source of parallel light, and is such that, when the beam of the source of parallel light is coaxial to the exit beam, the said sensor (38) is also at the focus of the mirror.

Light source moving type exposure device

Abstract: PURPOSE:To perform precise exposure, by performing moving exposure by means of a lamp house provided with a parabolic mirror having a long focal length, light source, and a 1st and a 2nd light intercepting bodies CONSTITUTION:A light source 15 provided at the focal point of a parabolic mirror or reflecting mirror 16 which is approximate to the parabolic mirror, the 1st light intercepting body 17 which is provided just below the light source 15 and intercepts direct rays of light to an original picture 8d and body 11 to be exposed, and the 2nd light intercepting body 18 which is provided closely to the original picture and body to be exposed and produces shadows that make the accumulated exposure quantity of each section of the original picture and body to be exposed uniform, are provided Since the utilization efficiency of the light source 15 is made higher and direct rays of light can be intercepted over a wide extent, the use of a shallow parabolic mirror having a long focal length becomes possible and the rays of light can be transformed to nearly parallel rays by reducing scattered rays of light Moreover, since the original picture and body to be exposed are positioned and fixed and the light source side is moved at the time of exposure, problems of positional discrepancy between the original picture and the body to be exposed caused by vibrations are solved and highly precise positioning becomes possible Therefore, highly precise exposure can be realized

The Study On The Small Solar Heat Engine That Was Driven By The Segment Type Parabolic Mirror

Abstract: A small solar heat engine designed by the authors consisted of a small solar furnace and a Stirling engine; the fabricating apparatus for the parabolic mirror was reported in the last conference of 13th 'Ea") In this paper, the construction for this solar furnace and the efficiency of the Stirling engine are reported.