Showing papers on "Parabolic reflector published in 1986"

An overview of near-field antenna measurements

Abstract: After a brief history of near-field antenna measurements with and without probe correction, the theory of near-field antenna measurements is outlined beginning with ideal probes scanning on arbitrary surfaces and ending with arbitrary probes scanning on planar, cylindrical, and spherical surfaces. Probe correction is introduced for all three measurement geometries as a slight modification to the ideal probe expressions. Sampling theorems are applied to determine the required data-point spacing, and efficient computational methods along with their computer run times are discussed. The major sources of experimental error defining the accuracy of typical planar near-field measurement facilities are reviewed, and present limitations of planar, cylindrical, and spherical near-field scanning are identified.

Steered-beam satellite communication system

Abstract: A satellite communication system employing a satellite in a geostationary orbit about the earth for communicating with ground stations disposed along a region of the earth positioned along an arc of a great circle of the earth. The satellite carries a frequency-scanning antenna array oriented for scanning a beam of electromagnetic radiation in one plane aligned with the arc of the great circle. Each position of the beam is formed with a different frequency of the radiation. The operating frequency of each ground station is selected to match the frequency of a beam directed from the satellite to the ground station. An antenna assembly formed of two confocal parabolic reflectors provides for a multiplication of the effective aperture of an array of radiating elements of the antenna, and also for a demagnification of a scan angle of radiation emanating from the array of radiating elements.

Linear collector for a parabolic reflector

Abstract: A parabolic reflector having support structure, mounted upon a rotatable track, for supporting a parabolic dish framework to which is mounted one or more support panels to which, in turn, are pivotally mounted a plurality of reflectors for focusing rays on a linear collector. The support panels include a plurality of concave recesses operable to receive bowl-shaped reflectors provided with polygonal rims so that the sides of adjacent reflectors will be in registry with one another. The support panels are provided with bolts, outwardly extending from the base of each recess, the bolts being received in slotted apertures in each reflector bowl for pivoting and fastening the reflector in a pre-selected position for focusing solar rays upon the collector. The collector includes a heat exchange media operable to conduct heat at extremely high temperatures for production of steam. A novel tracking system is also provided.

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.

Motor vehicle main beam headlamp incorporating an elliptical reflector and a parabolic reflector

Abstract: A headlamp of the type comprising: a light source (10); a two-focus elliptical reflector (20) having a base focus (F 1 ) and a front focus (F 2 ), said base focus being disposed in the vicinity of said light source and close to the base of the reflector, and said front focus being disposed in front of said base focus; and a parabolic reflector (30) having its focus (F 2 ) in the vicinity of said front focus of said elliptical reflector. The base of the elliptical reflector is provided with an opening for directly passing light from said light source, and a first sector (40) of a parabolic type reflector is provided with its focus in the vicinity of said light source and is disposed to reflect such light after passing through said opening along the vehicle axis direction (31, 41) to increase the on-axis main beam light intensity.

Signalling lamps with coloured lighting for a motor vehicle

Abstract: The invention relates to a signalling lamp for a vehicle, such as a motor vehicle, capable of emitting coloured, luminous signalling radiation through a colourless covering glass (32). According to the invention, the lamp comprises a reflector of the parabolic type (24'', 26) having a focal point (F'), an aperture formed in the reflector in the region of its base, a coloured filter (30) arranged in the aperture, means (20, 24) for emitting a concentrated beam of white light traversing the filter and directed towards the region of the focal point of the reflector, and a mirror (28) arranged in this region for returning the rays of the said beam, which are coloured by the filter, to the reflector assembly, the latter emitting the said coloured signalling radiation through the covering glass. In this way, a virtual coloured source is created at the focal point of the parabolic reflector, and the lamp appears perfectly colourless when extinguished.

Infra-red guard

Abstract: Pulsed infra-red rays from source 26 pass by way of collimating lens 28 and aperture mask 30 to diverging lens 22 from which they pass to partially-reflective window 18 whereat the rays are reflected as a beam onto parabolic mirror 16 which creates a substantially parallel curtain of rays across the space 14 to be monitored to impinge upon prismatic reflector 24 The beam reflected back from reflector 24 is in turn, reflected back by mirror 16 to the window 18 through which at least part of the beam passes to pass by way of an image lens 34 to detector 36 comprising, for instance, an array of photo-sensitive diodes Should there be an interruption of the curtain in the space 14, for instance as indicated at 40, there is a corresponding interruption at the detector 36 which sends an appropriate signal to reactive equipment (not shown) such as an alarm, fault display, or machine shut- off mechanism The mirror 16 is not essential, the beam reflected by the window 18 impinging directly on the prismatic reflector 24, (Fig 2, not shown)

Measuring device for concentration and partial pressure of gas

Abstract: PURPOSE:To remove a back light noise and to take accurate measurement by providing rotary sectors which rotate synchronously with each other on the optical axis of laser light emitted toward gas to be measured and a reflecting mirror between both sectors, and further providing a parabolic mirror for convergence and a spectroscope on the optical axis of reflected light CONSTITUTION:The rotary sectors 4A and 4B which rotate in synchronization with each other are provided on the optical axis of light emitted by a light source 1 through an elliptic mirror 2 and a parabolic mirror 3; a transmission hole 14 and a total absorbing surface 15 are arranged on the sector 4A at the light source side and a total reflecting surface 16, a total absorbing surface 16, and a transmission hole 4 are arranged on the sector 4B at the side of the gas to be measured A half-mirror 6 is arranged between the sectors 4A and 4B and a reflecting surface 7 is provided behind the gas 9 to be measured Reflected light from the mirror 6 is incident on a spectroscope 10 through an off-axis parabolic mirror 8 and a photodetector 11 detects light emitted by the spectroscope 10 Measurement light and reference light pass through a window 13 provided to a main body 12 Thus, the concn and partial pressure of many kinds of gas are measured simultaneously and accurately while a back light noise is removed

Luminaire having variable light distribution

Abstract: In a luminaire having a height-adjustable elongated light source (1) and a parabolic reflector which interacts therewith and consists of two shell-shaped reflector halves (2, 3) which can respectively be swivelled about a lower axis of rotation, a slatted louvre (9, 15) is provided whose transverse slats (9) engage with their ends (10) in the reflector halves (2 and 3) through enlarged cutouts (11) and are mounted on retaining rails (15) which extend along the outsides of the reflector halves.

Reflector element for fluorescent tubes which resembles a parabolic mirror

Abstract: In fluorescent tubes, the aim is to provide a parabolic mirror louvre which can be assembled from individual elements, and on the one hand can be produced cost effectively and on the other hand can be used with any installed fluorescent tube independently of the construction of its holder elements For this purpose, individual reflector elements are provided which can be plugged onto the fluorescent tubes (5) directly in a self-clamping fashion These reflector elements are in each case assembled from two concavely cambered strips (1) which are arranged in the cross-section opposite one another on a length of a parabolic curve and are connected to one another by transverse webs (2) The transverse webs (2) are provided with clips (3) for plugging onto the fluorescent tubes (5) The reflector elements can be lined up in the longitudinal direction with the aid of coupling elements (9, 10) The length of the reflector elements corresponds to the size increment of standardized fluorescent tubes (5) or an even multiple thereof In practice, reflectors can be produced for all standardized fluorescent tube lengths using one and the same reflector element

A High Precision Telescope Pointing System

Abstract: A novel method of telescope pointing has been developed based on He-Ne laser interferometric measurements of mirror position. We have applied this technique to a Pfund-type telescope, which consists of a fixed parabolic mirror illuminated by a flat mirror which rotates in altitude and azimuth. If the parabolic mirror is stationary the angle of pointing depends only on the change of orientation of the flat mirror with respect to the parabolic mirror. The relative angles of mirrors with radius of 1 meter are measured to a precision of ~.05 arcsec. Fluctuations in the index of refraction of the atmosphere between the mirrors are the primary source of this limit; however, changes in pointing position involving only a gradient in the index of refraction perpendicular to the optic axis are largely compensated by this pointing technique. Conversion of interference fringe counts to precise angle of pointing involves solutions of equations of modest complexity, but is easily handled by a small computer.

Laser scanning device

Abstract: PURPOSE:To improve magnetic characteristics without flawing the insulating film of a grain oriented electrical steel sheet by providing a cylindrical mirror or lens at the entrance side of a rotary polygon mirror so that its axial direction is parallel to the axis of rotation of said polygon mirror. CONSTITUTION:A laser beam 1 is reflected by the rotary polygon mirror 2 and converted as a fine circular beam by a parabolic mirror 3 on the surface 4 of the grain oriented electrical steel sheet at a distance of focal length (f). In this case, when the cylindrical mirror 10 is arranged at the entrance side of the polygon mirror 2 so that its axial direction 10-1 is parallel to the axis 2-1 of rotation of the polygon mirror 2, the mirror 10 only reflects the laser beam 1 by its yz plane and converges it by its zx plane. Therefore, the laser beam 1 have different convergence positions in its scanning direction and a direction perpendicular to it and has a cross section shape shown in 12 in a figure on the copper plate surface 4 and a shape shown by 12 at a position 5 close to the copper plate surface 4. Therefore, an elliptic beam having its long axis in the scanning direction is formed on the steel sheet surface 4, so that a magnetic domain is fractionized without flawing the steel sheet 4.

Supporting structure for a parabolic reflector antenna for a satellite communication system

Abstract: 1. Mounting frame, consisting of six struts (1 to 6) in all, two of which (5, 6) are designed to be adjustable in their length, of a symmetrical parabolic reflector antenna (14), which is to be directed at a geostationary communications satellite (ISV; DFS1; DFS2), moving in an equatorial orbit (OR), and which can be tilted about a declination axis (7), running in east-west direction, and a polar axis (8), crossing the said declination axis perpendicularly and thus aligned in parallel with the earth's axis, characterized in that in each case two (1, 2; 3, 4) of the four struts which are not adjustable in their length form an isosceles triangle with the declination axis (7) and are mounted together in two bearing locations (10, 11) on a foundation (9) so as to tilt about the declination axis (7), in that in each case the polar axis (8) runs through the two corners (12, 13) away from the declination axis (7) of the two superimposed isosceles triangles, in that the parabolic reflector antenna (14) is preferably articulated axially symmetrically at the two corners (12, 13) away from the declination axis (7) of the two triangles so as to tilt about the polar axis (8), to be precise such that, with the polar axis (8) running absolutely parallel to the earth's axis, the parabolic reflector antenna is inclined in relation to the polar axis (8) by an angle (gamma m ) dependent on the terrestrial latitude of the antenna site (M), in that the strut (5) designed so as to be adjustable in its length for setting the polar axis inclination (alpha) is attached by a both-ended swivel-joint mounting between the corner (13) away from the declination axis (7) of the lower of the two isosceles triangles and a foundation location (15), through which the plane defined by the angle bisectors of the two isosceles triangles runs, this foundation location (15) lying to the south of the declination axis (Fig. 2) in the case of an antenna site (M) in the northern hemisphere and lying to the north of the declination axis in the case of an antenna site in the southern hemisphere, and in that the other strut (6) designed so as to be adjustable in its length for setting the polar angle, is likewise attached by a both-ended swivel-joint mounting between a bearing location (16), provided for it eccentrically to the left or right on the rear of the parabolic reflector, and the one of the two strut bearing locations (10, 11) which is further remote from it in each case, through which locations the declination axis (7) runs.

Broadband Frequency Selective Surface

Abstract: Future communication satellites will use dichroic subreflectors to produce multiple focal regions from a single parabolic reflector. This additional focal region will allow for beams operating over different frequency bands to be produced by a single reflector and avoid the feed crowding or mechanical limitations current reflector antennas encounter. This paper presents parametric studies on a selected number of dichroic elements for possible use as a frequency selective subreflector. The theoretical and measured frequency response of tripoles and Jerusalem crosses are presented. This paper also addresses the design of multilayered dichroic panels to achieve improved gain slope and bandwidth. Designs capable of producing a 4:1 stopband and a 1.4:1 band separation for circular polarization and angles of incidence up to 40 degrees are shown.

CIRCE (Convolution of Incident Radiation with Concentrator Errors): A computer code for the analysis of point-focus solar concentrators

Abstract: In this paper a computer simulation code called CIRCE is discussed and examples of its application to several point-focus concentrating collector geometeries are presented. CIRCE, an acronym for Convolution of Incident Radiation with Concentrator Errors, was developed from HELIOS, a large multipurpose cone optics computer code for the analysis of central solar receiver systems. CIRCE was developed with the objective of providing knowledgeable users with an easily used design tool which does not require a large investment of time to obtain results. In CIRCE, the concentrator errors are convolved with the solar intensity profile (sunshape) to produce the flux-density distribution on a specified target plane. CIRCE may be used to analyze reflectors that are spherical, parabolic, or flat in shape and are either continuous surfaces or faceted. The current version of the code is restricted to the analysis of reflector systems which have flat rectangular or circular targets. Presented in this paper are examples of the use of CIRCE for optical performance calculations for both faceted and continuous parabolic dishes. In particular, the sensitivity of the optical efficiency to concentrator errors and to sunshapes (which are a function of the solar intensity level) is investigated for circular targets centered inmore » the concentrator focal plane. Results for a three facet concentrator are also presented and compared with those for an equivalent area continuous parabolic dish to demonstrate the capability of the code and the differences between these concentrators. In this last example, the performance degrading effects of astigmatic focusing are shown for the three facet reflector system.« less

Alignment device for a sighting apparatus having several channels

Abstract: The device is intended for a sighting apparatus comprising an infrared detector and a laser range-finder. It includes an optical combiner 12 having a hole-source 22 emitting in the first region and in the visible region, a semi-transparent plate 28 placed in the emission path of the hole-source 22 and reflecting a fraction of the light of a beam coming back to the source towards a separating plate 40 which directs the visible light towards the graticule of a sighting member 36 and the infrared light in the said other region towards a reflector, the image of which in the detector can be identified, and a parabolic mirror 13 placed so as to receive the exit beam of the source and the reflected beam, the combiner and the mirror both being placed so that the hole-source 22, the graticule 34 of the sighting member and the reflector 38 are at the focal point of the mirror.

Optical device which can be used in space-domain filtering and frequency-domain spectrum-analysing systems

Abstract: The optical device according to the invention comprises a dynamic optical system composed of a concave parabolic mirror 1, the concave surface of which is turned towards the entrance-exit (input-output) plane in which a reflection filter F, the centre of which coincides with the focal point of the concave parabolic mirror, is arranged between the information transparency 4 and the image receiver 5. It is characterised in that, in front of the reflection filter F, which is a holographic filter 3, is placed a non-linear adaptive optical element 8 having an amplitude transmission coefficient inversely proportional to the intensity of the incident light at each point of the filter 3. Usable in space-domain filtering and frequency-domain spectrum-analysing systems.

Comparison Of Large Aperture Telescopes With Parabolic And Spherical Primaries

Abstract: Quasi-Cassegrain-type four-mirror telescopes are compared to conventional two-mirror Cassegrain telescopes for use as high performance, very large aperture space telescopes. Spherical and parabolic primaries with continuous as well as segmented surfaces are considered. Imaging characteristics and misalignment sensitivities serve as the principal criteria of comparison. The evaluation shows that parabolic primaries yield superior wide-field performance, whereas spherical primaries hold distinct advantages regarding manufacturability and regarding certain alignment aspects in the case of segmentation.

Shaped beam reflector antenna

Abstract: A shaped beam antenna of the type comprising a main reflector and a feed horn for irradiating an electromagnetic wave upon said main reflector, the main reflector including, in sectional planes inclusive of a Y-Z plane and planes parallel thereto, a central section and horizontal side end sections adjoining the central section, where Cartesian coordinates are assumed having an origin near the feed horn, a Z-axis extending in a direction of the horizontal center axis of the feed horn, and X- and Y-axes extending in planes perpendicular to the Z-axis. The central section has a plurality of torus reflector segments and each of the side end sections has a plurality of parabolic reflector segments, and the torus and parabolic reflector segments are grouped into first and second portions, the first portion having the reflector segments which are symmetrical with respect to the Y-Z plane, the second portion having first and second sub-portions, the reflector segments of the first sub-portion and those of the second sub-portion being asymmetrical with respect to the Y-Z plane, whereby the maximum radiation direction of the beam reflected from the first portion lies in the Y-Z plane, and the maximum radiation direction of the beam reflected from the second portion lies in planes other than the Y-Z plane.

Testing device of parabolic mirror

Abstract: PURPOSE:To test a parabolic mirror by emitting laser light from the focal position of the parabolic mirror, projecting the reflected light on a plane mirror, reflecting the reflected light by the parabolic mirror, condensing the light at the focal position and reflecting the light again and projecting interference fringes on a detecting screen. CONSTITUTION:Laser light from a laser equipment 2 enters a light emitting section 1 and is emitted to a point A on the parabolic mirror 3 from a point O of the emitter section 1. The reflected light enters a point B of a plane mirror 4 and returns to the point O through the same path. Similarly, light emitted to a point C of the parabolic mirror 3 is reflected at a point D of the plane mirror 4 and returns to the point O. The length of light paths OAB and OCD are adjusted to become equal. A screen 5 that shades about a half of the parallel light is provided between the parabolic mirror 3 and plane mirror. Optical fibers 7 are used in the light emitting section, and the light returned to the point O is emitted again by the end face of the core 8 of the fibers 7, and at the same time, laser light from the equipment 2 is emitted. Thus, the distortion of the parabolic mirror can be tested from the pattern of interference fringes formed on the screen 5.

Instrumentation For Near-Millimeter Wave Propagation Studies

Abstract: Instrumentation for studying the propagation of near-millimeter waves has been designed and is currently being implemented at a 1 mile long test site in Sandusky, Ohio. An optically pumped near-millimeter (NMM) wave laser, used as a source of radiation for frequencies near 300 GHz, is located at one end of this site. The laser beam spot size arriving at the other end of the propagation path is controlled by a two-lens optical system placed at the laser's output. The receiver system consists of a parabolic reflector, a focal plane scanning system, and a fast-response liquid-helium-cooled InSb detector, all of which is controlled by a 68000-based microcomputer. Measurement of the characteristics of the received beam is based upon a quasi-optical method. The temperature/humidity atmospheric structure parameters and hydrometeor characteristics along the path are obtained simultaneously with the propagation measurements. These two measurements are then correlated to provide a meteorologically well-verified propagation model for near-millimeter wavelengths.

A Cassegrain reflector system for compact range applications

Abstract: An integral part of a compact range is the means of providing a uniform plane wave A Cassegrain reflector system is one alternative for achieving this goal Theoretically, this system offers better performance than a simple reflector system The longer pathlengths in the Cassegrain system lead to a more uniform field in the plane of interest The addition of the subreflector creates several problems, though System complexity is increased both in terms of construction and performance analysis The subreflector also leads to aperture blockage and the orientation of the feed now results in spillover illuminating the target areas as well as the rest of the range Finally, the addition of the subreflector leads to interaction between the two reflectors resulting in undesired field variations in the plane of interest These difficulties are addressed and through the concept of blending the surfaces, a Cassegrain reflector system is developed that will provide a uniform plane wave that offers superior performance over large target areas for a given size reflector system Design and analysis is implemented by considering the main reflector and subreflector separately Then the system may be put together and the final design and system analysis completed

A linearly-polarized dual-band diplexer in an offset reflector

Abstract: This paper assesses the performance of a dual linearly polarized 45° incidence frequency selective diplexer in an offset parabolic reflector. Three different plane frequency selective surfaces have been studied—single layers of concentric rings and double squares, and a four—layer surface consisting of capacitive patch arrays. All three give operating bands near 22 GHz and 32 GHz. The peak linear crosspolar levels of the diplexer alone and in the offset reflector are discussed, together with the copolar sidelobe performance of the complete antenna.

Laser light condenser

Abstract: PURPOSE:To simplify the adjustment of a focal position by adjusting the visible light out of the laser light which is adjusted to the same optical path in the 1st optical path adjusting part so as to enter perpendicularly a plane reflecting mirror and adjusting the invisible light so as to reflect in the optical axis direction of paraboloid in the 2nd adjusting part. CONSTITUTION:The plane mirror 12 is moved in a direction 16a and a test piece is put into the position intersecting with the optical axis in proximity to the plane mirror 18. The CO2 laser light 1 is irradiated on the test piece to put the trace of burn. The mirror 12 is returned to the position orthogonal with the optical axis and the He-Ne laser light 5 is oscillated. Said light is irradiated via a reflection face 11 to the test piece and the plane mirror is so adjusted that said laser light coincides with the trace of the burn of the light 1. The mirror 8 is then turned to adjust the He-Ne laser light light so as to be put into and out of an optical path 26 along the same and after the laser light is condensed to a focus 23, the CO2 laser light 1 is oscillated. The easy and sure adjustment of the condensing position of the light 1 is thus made possible while the parabolic mirror 10 is held stationary.

Large Inflatable Parabolic Reflectors In Space

Abstract: Large aperture parabolic reflectors are needed for space applications in different wave-length ranges including the millimetric and submillimetric ones where a high accuracy is required for the reflecting surfaces. We propose to get more accurate surfaces by replacing the preformed flexible membranes presently scheduled in the inflatable technology, by elastic disks whose thickness variation along a radius is calculated in order to obtain, after inflation, parabolic caps. As an illustration of the method, polyester and polyimide membranes are investigated. Provide a variable thickness from the center to the edge is obtainable, large aperture parabolic cap may reasonably be considered as feasible. The surface accuracy depends mainly on the elastic properties of the material and the thickness control.