Showing papers on "Parabolic reflector published in 1990"

Collimation optical system especially for helmet display device

Abstract: PURPOSE: To remove the cause of aberration an to improve the quality of a video by making a 1st mirror reflective and a 2nd mirror partially transparent. CONSTITUTION: This collimation optical system is constituted of a device for generating an optical video or a light source 1, an objective collimating lens or a collimator 2, a 1st parabolic mirror 4 and a 2nd parabolic mirror 5 in order along the same optical path. The mirrors 4 and 5 form a confocal system, and the mirror 4 is a total reflection mirror and the mirror 5 is translucent so as to make radiation from outside landscape pass. the mirrors 4 and 5 are put at the end of a photocoductor formed of a plate 10 made of transparent material having two parallel surfaces, and form the confocal optical system for enlarging 1. Thus, wider visual field is obtained while holding the accurate quality of the video.

Inflatable concentrators for solar propulsion and dynamic space power

Abstract: This paper describes the development of an inflatable concentrator for solar propulsion, providing the source of heat to a hydrogen engine aboard the Solar Rocket. The latter is a device designed to carry payloads from a low earth orbit (LEO) to a geosynchronous orbit (GEO) at significant mass savings in comparison to chemical propulsion; it involves two light-weight parabolic reflectors in an off-axis configuration focusing solar radiation into the absorbers of the engine, which causes the emission of a hot hydrogen jet. Each of the reflectors has an elliptical rim with a 40 m major axis, providing heat to the propellant sufficient to produce about 40 lbs. of thrust. The same concentrator concept is contemplated for space power application to focus solar radiation on a conversion device, e.g., a photovoltaic array or the high temperature end of a dynamic engine. Under the present project, a one-fourth scale, 9X7 m off-axis inflatable concentrator has been under development as a pilot for the full-scale flight unit. The reflector component consists of a reflective membrane made of specially designed gores and a geometrically identical transparent canopy. The two form together an inflatable lenslike structure which, upon inflation, assumes the accurate paraboloidal shape. Thismore » inflatable structure is supported along its rim by a strong, bending-resistant torus. The paper describes the development of this system including the analysis leading to determination of the gore shapes, the reflector membrane design and testing, the analysis of the supporting torus, and a discussion of the effects of the space environment.« less

Parabolic solar collector body and method

Abstract: A solar collector structure and method of fabrication are disclosed, the solar collector being of the linear, parabolic reflector-type. The parabolic reflector body includes an elongated layered structure having a concave parabolic reflective surface. The reflector body is supported and reinforced by a longitudinal beam member bonded to the convex backside of the layered structure. The layered structure includes a first reflective layer and a supporting molded layer formed of an amorphous hard-curing adherent material such as concrete or stucco. The entire reflector body structure is fabricated on an elongated convex mold. The method of fabrication includes forming the mold using a screed-moving apparatus which moves longitudinally along the mold. As the parabolic reflector body is formed on the mold, the screed-moving apparatus is again used to shape portions of the reflector body. A means for fabricating a parabolic reflector body, including both the elongated mold and the molded and reflective portions of the reflector body, together with the reinforcing longitudinal beam member, is also disclosed.

Orthogonal parabolic reflector systems

Abstract: An Orthogonal Parabolic Reflector (40) is generated by rotating a parabolic curve 90° to the axis of symmetry passing through the focal point (42) of the parabola. The Orthogonal Parabolic Reflector (40) can concentrate a section of the linear source or sink (41) on the axis of rotation to the focal point (42), resulting in integrating the intensity as a point source or sink at the focal point (42) with almost no physical dimension effects.

Reflector for hand held flashlight

Abstract: A hand held flashlight uses first and second light bulbs and first and second reflectors to generate a spot beam for illuminating distant objects and a flood beam for illuminating objects that are near. The first reflector is a parabolic reflector with the first light bulb being positioned at its focus to generate the spot beam. The second light bulb is positioned within the second reflector to produce the flood beam. A diffusing lens can be inserted in front of the second reflector to provide the appropriate divergence for the flood beam. The spot beam is preferably oriented at an angle relative to the axis of the flashlight for ease of use. The flashlight is designed so that the spot beam faces in a forward direction and the flood beam in a downward direction.

An efficient plane wave spectral analysis to predict the focal region fields of parabolic reflector antennas for small and wide angle scanning

Abstract: An efficient approach is described for calculating the field distribution in the focal region of an electrically large, symmetric or offset parabolic reflector antenna with an arbitrary rim contour, when the concave reflector surface is fully illuminated by an obliquely incident arbitrary electromagnetic plane wave. The dominant contribution to the focal-region fields is found by transforming the physical-optics integral over the reflector surface into a plane-wave spectral (PWS) integral. The PWS integral is evaluated rapidly via the fast Fourier transform (FET) algorithm to furnish, in only a single computation, the field for every place in the focal plane (or any plane parallel to it) within the focal region for a given direction of the incident wave. The correction to the physical-optics field is relatively small in the focal region and may therefore be neglected. Numerical results based on this PWS approach are presented, and their accuracy is established by comparison with results based on other approaches. >

Quasi-optical antennas for plasma scattering

Abstract: Two types or quasi-optical antennas are examined for their suitability as a means of directing the radiation from a tunable gyrotron millimetre-wave source into a plasma for scattering. The first type of antenna has a single parabolic reflector. The second has two reflectors; the first elliptical, the second parabolic. This combination has the advantage of focusing the beam into a spot at the centre of the plasma.

Radiometer system incorporating a cylindrical parabolic reflector and minimum redundancy array feed

Abstract: A radiometer system is disclosed, the system incorporating a cylindrical parabolic reflector and a plurality of radiation sensors disposed along the focal line of the reflector in a minimum redundancy array. Digital processing circuitry is connected to the output of the sensors for digitally processing signals using a cross-correlation signal processing and fast Fourier transform circuitry to generate image signals, the system providing reduced weight and increased signal integration time. Several embodiments of the system are disclosed including analog and digital versions having a multiplicity of antenna configurations.

Method and device for measuring particle size of extremely small particle by light scattering method

Abstract: PURPOSE:To measure the particle size of extremely small particles nondestructively without contacting by irradiating the surface of a sample which moves at an equal speed nearby a 1st focus of an elliptic condenser with converged laser light, detecting scattered light which is converged on a 2nd focus, and processing a detection signal CONSTITUTION:The laser light 2 emitted by a laser 1 is passed through a chopper 3, a spatial filter 4, a collimator lens 5, a polarizing prism 6, a beam splitter (BS) 7, and a lambda/4 plate 8, and reflected by a parabolic mirror 9 to travel backward, and the light is reflected by a BS 7 and converged in a spot The laser light which is made incident from an incidence opening 13 is converged on the 1st focus 11 of an elliptic surface mirror 10, reflected by the surface of the sample 15 in equal-speed motion, and reflected by the elliptic surface mirror 10, and the light is converged on a 2nd focus 12 and made incident on a detector E through a projection opening 14 and a parabolic light condenser 22 Its output is inputted to a computer 30 through a detector 29, whose pulse train output is integrated and the maximum value of the output voltage is compared with correlation data of the particle size and the maximum voltage to calculate the particle size of the extremely small particles sticking on a wafer 15

Fabrication of aspheric surfaces through controlled deformation of the figure of spherical reflective surfaces

Abstract: An aspheric mirror, for example in the form of an off-axis parabolic mirror or a toric mirror, that includes a first element having a front surface which defines a spherical reflector and a spaced apart rear surface. The spherical reflector includes a constant radius of curvature, an X-axis with an X-axis radius of curvature and a Y-axis with a Y-axis radius of curvature. The first element possesses a first rigidity factor. A second element includes a front surface sized to mate with the rear surface of the first element along an interface zone. The second element possesses a second rigidity factor. An interface contour device produces a differential contour within the interface zone between the first and second elements. The interface contour device is aligned to modify the X-axis radius of curvature of the shperical reflector without significantly modifying the Y-axis radius of curvature. A compression device compresses the first and second elements together to deflect the first element relative to the second element to modify the X-axis radius of curvature without substantially modifying its Y-axis radius of curvature to produce an aspheric mirror.

Inflatable concentrators for solar propulsion and dynamic space power

Abstract: This paper described the development of an inflatable concentrator for solar propulsion, providing the source of heat to a hydrogen engine aboard the Solar Rocket. The device involves two lightweight parabolic reflectors in an off-axis configuration focusing solar radiation into the absorbers of the engine, which causes the emission of a hot hydrogen jet. The reflector component consists of a reflective membrane made of specially designed gores and a geometrically identical transparent canopy. The development of this system includes the analysis leading to the determination of the gore shapes, the reflector membrane design and testing, the analysis of the supporting torus, and a discussion of the effects of the space environment.

Dismountable and air-transportable antenna for two-way telecommunications with a satellite

Abstract: The antenna is preferably of the offset type and comprises plural thin and separable parabolic elements jointed into a parabolic reflector, and several substantially rectangular separable panels assembled into a prismatic lattice frame for supporting the reflector. The panels are substantially perpendicular to the lower base of the lattice and have curved upper edges formed in a duplicate mould according to the reflector and separable from the reflector elements. The antenna also comprises a telescopic elevation angle lifting mast and a circular aximuth positioner, both jointed to the frame and dismountable. The dismounted antenna is transportable in the form of standardized packages in the hold of long-distance airliner.

Beam alignment device and method

Abstract: We describe a device for aligning optical beams that uses either an elliptically curved or a parabolically curved mirror arranged in the reflected beam path between a rotatable mirror, which is placed at the focus of the curved mirror, and the desired target. With the elliptical mirror, the device provides variable angle, fixed position of incidence of the reflected beam upon a target placed at the second focus of the ellipse. With the parabolic mirror, the device provides variable position, fixed angle of incidence of the reflected beam upon a target. Combinations of these devices may be used to solve a variety of beam steering and/or beam alignment problems. These devices are particularly useful for experiments and applications involving ultrashort optical pulses since the time of flight through either of these devices is a constant independent of the angle of incidence and the position of incidence.

Antenna having a parabolic reflector

Abstract: An antenna with a parabolic reflector (1) and at least one supply line (2) is specified, on whose free end an exciter is fitted. The supply line (2) is constructed as a bending-resistant, tubular component of metal. It projects through a central opening (5) of the reflector (1) and is fixed to the same by means of a metallic retaining flange (7). For simple, corrosion-free and dimensionally accurate installation, the retaining flange (7) is soldered circumferentially to the supply line in the course of prefabrication.

Nutating subreflector for a millimeter wave telescope

Abstract: Nutating a Cassegrain telescope’s secondary mirror is a convenient method of steering the telescope beam through a small angle Using this principle we have constructed a high performance beam switch for a millimeter wave telescope A low mass, graphite‐epoxy laminate secondary mirror is driven by linear electric motors operated in a frequency compensated control loop By design, the nutator exerts little net oscillating torque on the telescope structure, resulting in virtually vibration free operation The inherent versatility of beam switching by subreflector nutation allowed us to test a variety of switching waveforms without making any hardware changes To reduce the peak stresses on the mechanical linkage between the mirror and the motors and to attain a minimum transition time between mirror positions, we use a digitally generated driving waveform tailored to the system’s transfer function The nutator can shift the telescope beam by 10 arcminutes, a 125° rotation of the 75‐cm‐diam secondary mirror

Analysis of the thermal environment and thermal response associated with thermal-acoustic testing

Abstract: A method is developed for predicting the radiant heat flux distribution produced by a bank of quartz radiant heaters which accounts for the specular and diffuse effects of a flat reflector or the diffuse effects of individual parabolic reflectors. This analysis is experimentally verified for a single unreflected lamp and a single lamp with a flat reflector. Observations on the further development of this analysis and experimental validation are discussed.

Modeling of compliant tube underwater reflectors

Abstract: A theoretical method for determination of multiple scattering of an acoustical wave by a grating of elastic obstacles is presented. The main advantages of the method are: The same formulation works for finite arbitrary gratings as well as for infinite plane gratings; and the calculation of the properties of the whole grating is decoupled from the calculation of the scattering properties of the individual components set in free field. Some results on compliant tube gratings (plane gratings and a parabolic reflector) are shown and compared to experiments.

Mud flap mounted vehicle reference lighting system

Abstract: A lighting system for over-the-road tractor-trailers or other large vehicles includes a plurality of lamps, mounted on a rear mud flap and directed downward and to the side, so as to cast a light pattern in an illuminated region on the road surface which is visible to the driver. Each lamp is mounted within a parabolic reflector and has a louver bolted on the bottom of the light to direct the light along a selected axis so as to effectively position the pattern at the most desirable location to allow the driver to see and control the rear of the truck. The driver is able to determine where the rear of the vehicle is by glancing at his side-mounted rear-view mirror and seeing the light pattern on the road surface. This facilitates maneuvering of the truck in tight spaces and in passing on the highway.

Lunar radiators with specular reflectors

Abstract: A unique radiator, suitable for use in relatively hot thermal environments such as the moon, has been devised and analyzed The radiator uses a parabolic specular reflector to deflect the solar rays and to shield the radiator from the hot lunar soil It can provide sink temperatures on the order of 147 K and effective emittances approximately equal to the emittance of the surface of the radiator Similar performance can be obtained on sun-oriented spacecraft that have a limited view of space

Design and fabrication of an erectable truss for precision segmented reflector application

Abstract: The design of a first generation, 4-meter-diameter, doubly-curved, tetrahedral support truss for precision parabolic reflector panels, incorporating joints specifically designed for on-orbit astronaut assembly, is presented. Operational and design features of the erectable joint are detailed. Methods used to achieve very accurate strut lengths are described. Initial static and dynamic truss test results are presented which demonstrate linear structural response and predictability. Truss surface accuracy, determined photogrammetrically, is shown to be within 0.003 inch (RMS) of design.

Determination of the Distribution of Incident Solar Radiation in Cavity Receivers With Approximately Real Parabolic Dish Collectors

Abstract: The absorption of solar heat and the attendant thermal and mechanical loadings on the tubes of cavity receivers depend predominantly on the flux distribution of the incident solar radiation. For an axially symmetric cavity receiver with a parabolic dish collector, it is simple to determine the insulation pattern on the receiver internal surfaces if the system is ideal. In such a system the surface of the dish is perfectly parabolic (no contour flaws are present), and the sun’s central ray impinges on the dish surface parallel to the focal axis (no sun tracking flaws are present). These two conditions cannot be achieved in practice, and therefore the feasible parabolic dish system is referred to as a “real” system although, in actual fact, it is only an approximation to any actual system. The purpose of this paper is to devise calculation principles which permit analysis of a receiver designed for ideal conditions (Bammert and Seifert, 1983; Bammert and Hegazy, 1984; Johanning, 1987) to verify its structural adequacy under the nonideal conditions to be expected in reality. Of the many possible imperfections in real collectors, two were selected which increase the loadings sustained. The first case concerns flaws in the contour of the dish surface. These locally increase the radiation concentration on the receiver inside walls and tubing. In the second case, sun-tracking errors give rise to axially asymmetric radiation distributions. In both examples, greater than design basis loadings will occur in the receiver tubing. Both kinds of flaws considered in this paper are of a purely deterministic nature. Other flaws statistically distributed on the dish surface (Kohne and Kleih, 1987, Guven, Bannerot, and Mistree, 1983; O’Neill and Hudson, 1978; Ratzel et al., 1987) do not cause structural overloading but must be taken into account in thermal performance analysis. The paper presents a method of analyzing the flux distribution on the internal surfaces of a cavity receiver with an approximately real parabolic dish collector. After a discussion of the theoretical principles, the effects of the collector contour and sun tracking errors on the insulation pattern are described with reference to an example.

A two‐dimensionally focusing, quasi‐optical antenna for millimeter‐wave scattering in plasmas

Abstract: A two‐dimensionally focusing, quasi‐optical antenna having one elliptical reflector and one parabolic reflector has been built for use with a tunable gyrotron in order to carry out millimeter‐wave scattering measurements on the TORTUS tokamak plasma at the University of Sydney. The advantages of this antenna are the following: (1) The elliptical reflector focuses the radiation beam in the toroidal direction, while the parabolic reflector focuses in the direction of major radius. This gives excellent two‐dimensional focusing in the plasma region, and consequently excellent spatial resolution. (2) The focal point can be easily swept along the direction of major radius in the whole plasma region, simply by changing the angle of the parabolic reflector by a small amount. These features have been demonstrated experimentally using the tunable gyrotron source, GYROTRON III, and in computations of the radiated fields.

Light valve projector

Abstract: PURPOSE: To project incident light from a light source to a rectangular modulator and a projection lens as uniform illumination light by forming an incident aperture and a projection aperture of a non-imaging reflector respectively in rectangles having almost parallel edge parts and satisfying specific relational equations. CONSTITUTION: A converging optical system in the projecting device is provided with the non-imaging reflector 10 for converging light rays projected from a light source 2 through the incident aperture 12 having an incident angle 2θi in a large range and dimension Di and uniformly illuminating the projection aperture 20 having an outgoing angle 2θo in a small range and large dimension Do . The reflector 10 is constituted so as to have a composite parabolic reflector shape having two axes (x), (y) orthogonal to the optical axis 18 of the reflector 10 and satisfy relational equations I, II. Here, Dix and Diy are the dimension of the incident aperture 12, θix and θiy are maximum incident angles, Dox and Doy are the dimension of the projection aperture 20, θox and θoy are maximum out-going angles, and ni and no are respective refractive indexes of the apertures 12, 20. The edge parts of both the apertures 12, 20 are formed in parallel.

Reflection lighting device with parabolic mirror

Abstract: PURPOSE: To reduce the size and to improve the light convergence efficiency by using the parabolic mirror as a main mirror and providing an auxiliary reflecting mirror which reflects light from a light source toward the light source without any loss at the open end part of the parabolic mirror. CONSTITUTION: A spot light source is placed at a focus F, the depth of the main mirror 11 consisting of the parabolic mirror is represented as the angle X, centered on the focus F, from a vertex P that an optical path O passes to the open end Q, and this angle X is set to ≥90°. Further, an auxiliary spherical mirror (auxiliary reflecting means) 13 is provided at the open end part of the main mirror 11 and reflects the light from the light source to the light source and its projection aperture diameter D 1 is set substantially equal to the open end part diameter ϕ 3 of the main mirror 1. The light has loss or irradiates a nonillumination area more in the case of unsatisfying the above conditions. Consequently, the device which is high light utilization efficiency and reducible in size is obtained. COPYRIGHT: (C)1992,JPO&Japio

Development of composite materials for spacecraft precision-reflector panels

Abstract: One of the critical technology needs for large precision reflectors required for future astrophysics and optical communications is in the area of structural materials. Therefore, a major area of the Precision Segmented Reflector Program at NASA is to develop lightweight composite reflector panels with durable, space environmentally stable materials which maintain both surface figure and required surface accuracy necessary for space telescope applications. Results from the materials research and development program at NASA Langley Research Center are discussed. Advanced materials that meet the reflector panel requirements are identified. Thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared to the baseline material.

An inflatable parabolic reflector antenna - Its realisation and electrical predictions

Abstract: Results of investigations are presented for the potential electrical performances of an inflatable reflector antenna (prime-focus) illuminated by a three frequency coaxial feed. The feed has been deigned and tested, the reflector has been folded and deployed and assessed for its surface accuracy. The measured reflector surface data have been red into a physical optics program, in which the feed patterns as measured have been inserted also. Secundary pattern performances have been derived.

Parabolic cylindrical surfaces employed as line sources and their use for illuminating conical reflectors

Abstract: The properties of line sources simulated by a parabolic cylindrical surface utilizing a point source are investigated. The factors controlling the cross-polarization and the means for elimination of the aperture blockage are also identified and studied. The line source is then used to illuminate a conical reflector with a 90° vertex angle. The performance of the resulting dual reflector system and the effects of various design parameters on its radiation patterns are investigated and presented.

Scanning type infrared ray image pickup device

Abstract: PURPOSE:To prevent a performance from being influenced with the temperature of an infrared scene by making one surface of a plane reflecting surface to compose a rotary polygon mirror into a rotary parabolic mirror and setting a focusing position formed with the reflected light of the mirror surfaces so as to satisfy specific conditions. CONSTITUTION:Five surfaces among six surfaces of a rotary polygon mirror 2 are made into plane mirrors 4, an ordinary scanning is executed, and an infrared video is obtained. The remaining one surface is made into a rotary parabolic mirror 10 in which the center of the position of a diaphragm 5 of a detector lens 6 is made into a focus. In an instant when the parabolic mirror 10 executes the scanning in a normal position, a multielement detector 7 to arrange a detecting element array in a perpendicular direction to a paper surface can detect the mean temperature of a scene in the Defocus cone. Here, 11 indicates a parabolic curve, 12 indicates a parabolic surface rotary axis, and 13 indicates the conical bottom surface position which the detector 7 receives the light. When the light-receiving optical path of the detector 7 is reversely traced, it is made into a parallel beam after it is reflected at the mirror 10 and conducted to an infinite focus optical system as shown by an arrow Q. Consequently, each detecting element of the detector 7 is made to see the same temperature as a visual field, and further, the temperature is equal to the mean temperature in the conical visual field.

Revolution reflector antenna

Abstract: The present invention relates to a revolution reflector antenna comprising at least one revolution reflector, made from a material having a liquid phase and a solid phase and obtained by centrifugation of the material in its liquid phase, subsequently passed into its solid phase. Application to any field in which a parabolic reflector of very high surface precision is necessary.

Uniform light distribution device for triangular prismatic reflector - uses diffuse reflection of light entering from extended source with dispersion angle not greater than 35 deg.

Abstract: The prism (1) is bounded by a transparent surface (3) of material (e.g. polycarbonate or polymethacrylate) with high refractive index and max. total reflection angle, and a diffuse reflecting surface (2) which scatters light entering through the base (4) from a fluorescent strip lamp (5) and parabolic reflector (6). Possible angles of the prism (1) are 90 to 110 deg. (alpha) and 60 to 80 deg. (beta) at its base (4), and 5 to 15 deg. between its diffuse reflecting and transparent faces (2,3). USE/ADVANTAGE - Advertising and information displays. Improved legibility with brightness varying within range which does not exceed 3:1.