Showing papers on "Parabolic reflector published in 2002"

Led light assembly

Abstract: An light source utilizes a parabolic reflector to collimate light emitted from at greater than a predetermined angle relative to the optical axis of an LED arranged at the focus of the reflector. An optional collimating lens is arranged to collimate light emitted at less than the predetermined angle. Both variations provide light in the form of a substantially collimated beam. The parabolic reflector is preferably extended along its focal point to form a linear parabolic section having a linear focal axis. A linear array of LEDs is arranged such that the linear focal axis passes through the area of light emission of each LED. The linear parabolic section may be provided with parabolic dish ends. Alternatively, the ends of the parabolic section may be left open for increased wide angle visibility.

Laser communication system

Abstract: An optical wireless transceiver (200) for communicating broadband signals through free space includes an input, a regenerator (206), a splitter (218) and a plurality of lasers in transmitter modules (225). A very fast (low f-number) optical receiver module includes a reflector, preferably a Mangin mirror or parabolic reflector with field corrector, aligned with an input aperture. A photodiode receives the signal from the reflector for subsequent demodulation. The transceiver provides signal regeneration and switchable data rates. Connections are made to optical or electrical digital inputs and outputs bearing signals of various protocols.

Exact optics: a unification of optical telescope design

Abstract: A perfect-focus telescope is one in which all rays parallel to the axis meet at a point and give equal magnification there. It is shown that these two conditions define the shapes of both primary and secondary mirrors. Apart from scale, the solution depends upon two parameters: s, which gives the mirror separation in terms of the effective focal length, and K, which gives the relative position of the final focus in that unit. The two conditions ensure that the optical systems have neither spherical aberration nor coma, no matter how fast the F ratio. All known coma-free systems emerge as approximate special cases. In his classical paper, K. Schwarzschild studied all two-mirror systems for which the profiles were conic sections. We make no such a priori shape conditions but demand a perfect focus and solve for the shapes of the mirrors.

Parabolic refractive X-ray lenses

Abstract: Parabolic refractive X-ray lenses are optical components, especially suitable for third-generation synchrotron radiation sources. This article describes the status of the development of our lenses and illustrates the possibilities for micrometre and submicrometre focusing and for X-ray imaging in absorption and phase contrast. The parabolic lens profile ensures distortion-free imaging of high quality. First characteristics of Be lenses are given. A microscope based on Be lenses is expected to have a lateral resolution below 80 nm.

Inflatable multi-function parabolic reflector apparatus and methods of manufacture

Abstract: An inflatable, multifunction, multipurpose, parabolic reflector apparatus having a plurality of manufactured parabolic mirrors (14, 16) made from a pressure-deformable reflective covering of an inflatable ring (12) for focusing electromagnetic energy from radio frequency radiation (RF) through the ultraviolet radiation (UV) and solar energy for (1) heating and cooking, for (2) electrical power generation, for (3) enhancing the transmission and reception of radio signals, for (4) enhancing vision in low-light environments, and for (5) projection optical signals or images. The device also has non-electromagnetic uses, such as the collection of water. A first main embodiment utilizes two reflective membranes.(14, 16) A second main embodiment utilizes a reflective membrane and a transparent membrane. Portability is enhanced by complete collapsing of the inflatable device.

The Large Adaptive Reflector: A Giant Radio Telescope with an Aero Twist

Abstract: A multi-national grouping of radio astronomers has identified the need for a major new instrument, called the Square Kilometer Array (SKA), to be constructed in the coming decade. This giant radio telescope will be 100 times more powerful than any in existence today. The innovative Canadian concept for the underlying design of the telescope, the Large Adaptive Reflector (LAR), is among the best candidates and is well positioned to be adopted by the international community. The LAR is a concept for a low-cost, large-aperture, wideband, radio telescope, designed to operate over the wavelength range from 2mt o 1.4 cm. Theproposed design for the LAR includes two central components. The first is a long focal length, large-diameter parabolic reflector, composed of actuated hexagonal panels, mounted on the ground. The second component is a focal package supported at a height of 500 m by a large helium balloon (aerostat) and a system of three or more taut tethers. The telescope is steered by simultaneously changing the lengths of the tethers with winches (thus changing the position of the feed) and by modifying the shape of the reflector. Simulations have shown that in operating wind conditions, the position of the feed platform can be stabilized to within a few centimetres. This paper gives an overview of the present state of the LAR design, with an emphasis on the airborne subsystem. Construction of a 1/3-scale model of the tethered aerostat subsystem, with a footprint of "only" 0.5 km 2 , is presently underway in Penticton, B.C. It will allow a validation of the underlying design and the study of some fascinating issues in the design and control of this system. Continued on page 240

Electron microscope and spectroscopy system

Abstract: An electron microscope (10) is adapted to enable spectroscopic analysis of a sample (16). A parabolic mirror (18) has a central aperture (20) through which the electron beam can pass. The mirror (18) focuses laser illumination from a transverse optical path (24) onto the sample, and collects Raman and/or other scattered light, passing it back to an optical system (30). The mirror (18) is retractable (within the vacuum of the electron microscope) by a sliding arm assembly (22). An adjustable kinematic mount (44) defines the inserted position of the parabolic mirror (18). A second parabolic mirror (104) is provided to direct the scattered or generated light towards an optical analyser. The parabolic mirrors are positioned in an aberration cancelling orientation and such that they compensate for inaccuracies in the position of the sliding arm assembly (22).

Optical design of a solar flux homogenizer for concentrator photovoltaics

Abstract: An optical solution is described for the redistribution of the light reflected from a 400-m2 paraboloidal solar concentrating dish as uniformly as possible over an approximately 1-m2 plane. Concentrator photovoltaic cells will be mounted at this plane, and they require a uniform light distribution for high efficiency. It is proposed that the solar cells will be mounted at the output of a rectangular receiver box with reflective sidewalls (i.e., a kaleidoscope), which will redistribute the light. I discuss the receiver box properties that influence the light distribution reaching the solar cells.

Light emitting diode reflector

Abstract: The present invention relates to a light emitting diode reflector which is installed in portable lighting equipment such as electric torches. The light emitting diode reflector comprises a reflector which is a one piece parabolic mirror, a front cover which is placed upon the open end of the reflector and a light emitting diode which is mounted at the center of the front cover facing the reflector. The light emitting diode reflector increases the light intensity significantly to meet the user's requirement and maintains the advantage of energy saving of using a light emitting diode as the light source.

Optical disc unit

Abstract: An optical disc drive according to the present invention reads and/or writes data from/on an optical disc having at least one information layer with a light beam and includes: a spherical aberration detecting section for generating a spherical aberration signal representing a spherical aberration produced at a focal point of the light beam on the information layer of the disc; a spherical aberration changing section for changing the spherical aberration; a spherical aberration regulating section for generating an aberration correction signal to correct the spherical aberration by driving the changing section; and means for detecting a value of the aberration correction signal that minimizes the spherical aberration when the focal point of the light beam is located on the information layer of the disc and for detecting the depth of the information layer, which corresponds to a distance from the information layer on which the focal point of the light beam is located to the surface of the disc, based on the value.

Etendue efficient coupling of light using dual paraboloid reflectors for projection displays

Abstract: With the introduction of Digital Micromirror Device (DMD) and Liquid Crystal on Silicon (LCOS) technologies, imagers for projection displays become increasingly smaller, thus requiring more intense, focused light with lower etendue values. To illuminate these smaller imagers, a patented dual paraboloid reflector system has been developed to collect and focus light from an arc lamp onto the imager without loss of brightness. This powerful optical platform provides the control and etendue efficiency that has been missing in standard illumination sy stems. The dual paraboloid reflector system consists of two parabolic reflectors placed symmetrically facing each other. The first parabolic reflector collects and collimates it into a parallel beam. The second parabolic reflector intercepts the parallel beam and focuses the light with unity magnification, i.e. 1:1 imaging, into a tapered light pipe (TLP) with conserved brightness. The TLP transforms the focused light into an output with the needed area, shape, and numerical aperture (NA). It also acts as a homogenizer so that the intensity profile at the output surface is uniform and eventually provides a uniform intensity profile at the screen. The reflection of light twice in the dual paraboloid reflector system provides a high IR and UV rejection ratios, resulting in less degradation of the optical components. Polarization and color recycling systems are also designed taking advantage of this reflector configuration.

Determination of the surface properties of a solar-powered steam generating parabolic mirror, so that misalignments can be corrected to ensure maximum operating efficiency

Abstract: Method for determining the surface properties of a parabolic mirror (40) in which a screen is placed between the focal point (20) of the mirror and the intersection of the normals from the mirror edges. The screen has a line image on it that is reflected by the mirror to a camera detector. The actual image is compared with an ideal image and from the differences, conclusions made about the mirror surface. The invention also relates to a device for implementing the above method.

Ultrasonic flow measurement of fluids such as natural gas, has acoustic transceivers that direct divergent beams of sound waves to sections of the pipe shaped to form parabolic reflectors

Abstract: At ends of a measurement pipe (1) are located acoustic transducers acting as transceivers. The first (2) beams a divergent beam (4) of sound waves to a section (8) of the pipe shaped to form a parabolic reflector. This directs a parallel beam (9) to a second parabolic reflector (10) which directs a convergent beam (11) to the second transducer (3). Over the resultant sound path all the individual sound waves (5-7) have the same length so that the presence of turbulence in the pipe is indicated by time delays and frequency shifts between the individual waves.

Reflector lighting fixture, especially for in-the-floor, in-the-wall or in-the-ceiling lighting

Abstract: A parabolic reflector lighting fixture for use as an in-the-wall or in-the-floor or in-the-ceiling light has its lamp shiftable in a lumen plane perpendicular to the axis of symmetry of the parabolic reflector through the focal point. The parabolic reflector is limited to reflect light only between the intersection of this lumen plane and the reflector and between this intersection and the apex of the reflector.

Conceptual design of high power advanced low mass (HPALM) solar thermionic power system

Abstract: The conceptual design of an innovative solar space power system based on thermionic conversion of heat to electricity is in progress. The system is particularly attractive for large power requirements (>20 kW). Solar energy is collected with an inflatable structure, which can be a parabolic reflector or a Fresnel lens or reflector. The solar flux is further concentrated with a secondary concentrator before entering the thermal receiver. The heat is converted to electricity directly by cylindrical inverted multi-cell (CIM) thermionic converters. Initial estimates of volume and mass yield a preliminary specific mass of ∼100 W/kg and a preliminary specific stowed volume of ∼80 W/m3.

Enhancement of TXRF intensity by using a reflector

Abstract: We investigated the possibility of enhancing the TXRF intensity by applying an Si reflector. This Si reflector was attached just above the Si sample carrier. The angle between the reflector and the sample carrier was changed by tilting the reflector. We attempted to focus the primary x-rays on the analyzed area by multi-reflection effects between the reflector and the sample carrier. The intensity of Au Lα emitted from a thin layer of Au deposited on an Si sample carrier, was measured as a function of the angle between two Si plates. The observed peaks were explained from simple calculations, suggesting that the reflection of primary x-rays on both the reflector and the sample carrier results in a significant increases in x-ray intensities. In addition, Ar Kα emitted from the air, was reduced substantially by applying the reflector. This indicates that a reflector is also useful for reducing the x-ray background that originates from the air and the sample carrier. Copyright © 2002 John Wiley & Sons, Ltd.

Reflector with complex parabolid surface for elongated light source

Abstract: A surface mountable strobe incorporates an elongated light source and a multi-element reflector. The reflector includes a first generally circular partial parabolic reflector element with an axis of rotation which corresponds to an axis of symmetry of the source. The first reflector element produces a spike of on-axis radiant energy which substantially exceeds the off-axis output profile. A plurality of spaced apart arcuate reflector elements provides output light profiles in horizontal and vertical planes which intersect at or near the axis of the source.

A new troughlike nonimaging solar concentrator

Abstract: A new two-dimensional concentrator for solar energy collection has been developed. The concentrator has the following advantages, when compared with the classic Compound Parabolic Concentrators invented by Roland Winston, W. T Welford, A. Rabl, Baranov, and other researchers: 1) It allows the use of parabolic mirrors, which have a reflecting area much smaller for a given concentration ratio and acceptance angle. 2) Between the mirror and the absorber, there is a large gap so that conduction losses are reduced. Convection losses can be reduced, too, if the absorber is enclosed within a glass tube. 3) It can be easily manufactured. Instead of seeking the shape of the mirrors for a given shape of the absorber, we have made the inverse statement of the problem, and we have obtained the optimal shapes of the absorbers with a prescribed acceptance angle, for parabolic mirrors, assuming that the intercept factor is unity, the mirrors are perfect, and the absorber surfaces are convex. The concentrator should be east-west oriented, and could be seasonal or monthly tilt adjusted. This concentrator could have many practical applications, such as fluid heating, steam generation, etc.

Solar collecting and tracking apparatus

Abstract: PURPOSE: A solar collecting and tracking apparatus is provided to track the sunlight to collect solar energy in the optimum state by using power generated from collected solar energy. CONSTITUTION: A solar collecting and tracking apparatus includes a solar tracking section(41) and a solar collecting section(40). The solar tracking section(41) controls rotating motors(17,19) by calculating the direction and the length of a shadow of a vertical stick(5) placed on an opto-electronic component(6). The solar collecting section(40) collects solar energy reflected from an inner peripheral portion of a parabolic mirror(1) using a convex lens(8). A solar cell panel(2) is rotatably installed along an upper end of the parabolic mirror(1). A rotating motor is rotated by control signals from a control box(13), thereby adjusting the position of the parabolic mirror(1).

Angular Resolution of the Pachmarhi Array of Cerenkov Telescopes

Abstract: The Pachmarhi Array of Cerenkov Telescopes consists of a distributed array of 25 telescopes that are used to sample the atmospheric Cerenkov Photon showers. Each telescope consists of 7 parabolic mirrors each viewed by a single photo-multiplier tube. Reconstruction of photon showers are carried out using fast timing information on the arrival of pulses at each PMT. The shower front is fitted to a plane and the direction of arrival of primary particle initiating the shower is obtained. The error in the determination of the arrival direction of the primary has been estimated using the {\it split} array method. It is found to be $\sim 2.4^\prime ~$ for primaries of energy $ > 3 TeV$. The dependence of the angular resolution on the separation between the telescopes and the number of detectors are also obtained from the data.

Shape error measurement using ray-tracing and fringe scanning methods: projection of grating displayed on a liquid crystal panel

Abstract: We present an improved Hartmann test, which has high spatial resolution with respect to the measuring points, for measuring projection mirrors. In the method, grid lines with a sinusoidal transmittance distribution are displayed on a liquid crystal panel and illuminated with a collimated laser beam. The beam transmitted through the liquid crystal panel reflects off the mirror surface being tested and reaches a screen. A charge-coupled device camera detects the projected images, which contain information about the inclination of the surface being tested. Any error in the shape of the mirror surface is identified by integrating the inclination. To increase the spatial resolution, the fringe scanning method is performed by shifting the grid lines on the liquid crystal panel. The grid lines are optimized for the shape of the mirror being tested. Because the grid lines are displayed by an electrical method, the shifting operation is easy and rapid, and furthermore, the displacement can be done precisely. The shape error of an off-axis parabolic mirror made of plastic is measured by the proposed method.

Coupling configuration for optically coupling an optical conductor to an opto-receiver

Abstract: A coupling configuration for connecting an optical conductor to an opto-receiver has a parabolic mirror or a spherical mirror that reflects light emerging from the optical conductor onto a launching mirror through which the light is launched into the opto-receiver. Such a configuration is largely adjustment-free and therefore particularly suitable for the connection of single-mode fibers (SMF).

Projection display system using two lamp sources

Abstract: The invention relates to a projection display system comprising two lamp sources (32,46) each having a different geometric aligning means. By combining a first light source (32) having an annular cross-sectioned beam and a second light source (46) having a circular cross-sectioned beam sized to be identical to said annulus, a light beam is created that provides more light and greater beam uniformity than has heretofore been available using low cost components. The annular beam is produced by a first lamp apparatus having a rear spherical reflector (88) and a front parabolic reflector (84) oriented along an optical axis. The circular beam is produced by a second lamp apparatus having a front spherical reflector (104) and a rear parabolic reflector (106) and having an orientation orthogonal to said optical axis. When the two beams are combined at an oval-shaped flat reflector (52) positioned at a 45° angle to the optical axis, a complementary beam is formed which provides a highly efficient and uniformly distributed light source.

Lighting device producing asymmetrical light beam and equipped with non-reflective cover

Abstract: The light fitting (10) has a parabolic reflector (18) which is aligned asymmetrically with the protective glass (14) to give a beam directed in the forward sense and suitable for illuminating sports grounds or motorway tunnels. Anti-reflective coatings (42,44) are applied to both sides of the protective glass to reduce the amount of light projected backwards by double reflection

Parabolic reflector and antenna incorporating same

Abstract: A parabolic reflector (20) for an antenna has a plurality (N) of concentric annular sections (20a-20e) arranged in series from a first annular section (20a) nearest a central axis (40) of the reflector to a last annular section (20e, 30e) defining an outer perimeter (45) of the reflector. Each section (20a-20e) has a parabolic reflecting surface between inner and outer perimeters. The sections (20a-20e) are configured such that the focal point (41) associated with at least the last section (20e) lies inside an internal volume (42) of the reflector and are arranged with respect to each other along the central axis, such that an overall depth of the reflector is substantially minimised. The inner perimeters of all the sections (20a-20e) are preferably arranged to lie substantially on a plane (29) which is perpendicular to the central axis (40). The outer perimeter of each section (20a-20d) except the last section is preferably connected with the inner perimeter of the succeeding section by means of an annular strip (28). The strips (28) may either each have an angle of inclination to the reflector central axis of between 0 and 3° or they may lie on respective cones running from the respective inner perimeters of the respective sections to which they are joined, to the furthest located focal point or ring.

Design of offset reflector with elliptical flat scan mirror and its applications to a dual-frequency, dual-polarization airborne rain radar observations

Abstract: This paper presents the analysis, design, and development of a dual-frequency (Ku and Ka-band), and dual-polarization at each frequency, airborne rain radar antenna (ARRA) system. JPL is currently developing an airborne rain radar instrument to make such observations from NASA's DC-8 aircraft. The antenna system uses a highly reflective elliptical scan mirror in conjunction with an offset parabolic reflector illuminated by a common-aperture feed system, consisting of a corrugated horn with four input ports. The reflecting mirror is rotated in azimuth to scan the antenna beam in the cross-track direction (/spl plusmn/20/spl deg/) for wide swath coverage, and in elevation to compensate for the motion of the aircraft. The calculated results, as well as the measured electrical performance over wide-angle scanning, are presented. The theoretical results (calculated) guiding the antenna optimization are based on physical optics (PO) analysis and agree well with the measurements and our design goals.

Generation of focused shock waves by multi-channel electrical discharges in water

Abstract: A novel method for generation of focused shock waves based on multi-channel partial electrical discharges in water with an increased conductivity has been developed. The multi-channel discharge is formed on a composite anode consisting of a metallic electrode covered by a thin porous ceramic layer. Two versions of the generators have been realized. In the first one a cylindrical pressure wave is created on a cylindrical anode 60 mm in diameter and 100 mm long. At the applied voltage of 30 kV, a large number of short discharge channels distributed almost homogeneously on the anode surface are initiated. Each channel creates a semi-spherical pressure wave, and by superposition of all of the waves a cylindrical pressure wave propagating from the anode is formed. The cylindrical pressure wave is focused by a metallic parabolic reflector (cathode) and near the focus it is transformed to a strong shock wave. In the second version a convergent spherical pressure wave is formed by the same kind of the multi-channel discharge on a composite anode in the form of a part of spherical cavity. The discharge volume with the conductive water solution is separated from the experimental space (distilled water) by an acoustically transparent membrane. When supplying the discharges by 1 /spl mu/F condenser bank charged to 30 kV, the amplitude of the shock wave reached 100 MPa at the focal point for the both generators. The shock waves are sharply focused to a focal area of 3 mm, in diameter transversally (full width at a half maximum) and of 40 mm longitudinally. Interaction of two shock waves generated by two subsequent discharges has been demonstrated. Cellular damage induced by the shock waves was demonstrated on hemolysis of human erythrocytes and on damage of lymphocytes.

Conceptual design of high power advanced low mass (HPALM) solar thermionic power system

Abstract: The conceptual design of an innovative solar space power system based on thermionic conversion of heat to electricity is in progress. The system is particularly attractive for large power requirements (>20 kW). Solar energy is collected with an inflatable structure, which can be a parabolic reflector or a Fresnel lens or reflector. The solar flux is further concentrated with a secondary concentrator before entering the thermal receiver. The heat is converted to electricity directly by cylindrical inverted multicell (CIM) thermionic converters. Initial estimates of volume and mass yield a preliminary specific mass of /spl sim/80 W/kg and a preliminary specific stowed volume of /spl sim/40 kW/m/sup 3/.