Showing papers on "Parabolic reflector published in 2015"

Design and Calibration of a Compact Quasi-Optical System for Material Characterization in Millimeter/Submillimeter Wave Domain

Abstract: A compact quasi-optical setup based on conventional rectangular horn antennas and two symmetrical parabolic mirrors is designed to provide a plane wave on the material under test. To measure the scattering parameters at millimeter/submillimeter wavelengths, a commercial vector network analyzer and waveguide frequency extension units are used. The calibration of the system is performed with a simple practical deembedding process to determine the S-parameters on the material surface without using high-cost micrometer positioners. A reliable extraction method is presented to derive the material permittivity and calculate the errors and uncertainties as direct functions of the sample and setup geometry and their physical characteristics. Several materials are measured and the complex permittivity is presented together with a detailed uncertainty budget.

Aerial projection of three-dimensional motion pictures by electro-holography and parabolic mirrors.

Abstract: We demonstrate an aerial projection system for reconstructing 3D motion pictures based on holography. The system consists of an optical source, a spatial light modulator corresponding to a display and two parabolic mirrors. The spatial light modulator displays holograms calculated by computer and can reconstruct holographic motion pictures near the surface of the modulator. The two parabolic mirrors can project floating 3D images of the motion pictures formed by the spatial light modulator without mechanical scanning or rotating. In this demonstration, we used a phase-modulation-type spatial light modulator. The number of pixels and the pixel pitch of the modulator were 1,080 × 1,920 and 8.0 μm × 8.0 μm, respectively. The diameter, the height and the focal length of each parabolic mirror were 288 mm, 55 mm and 100 mm, respectively. We succeeded in aerially projecting 3D motion pictures of size ~2.5 mm3 by this system constructed by the modulator and mirrors. In addition, by applying a fast computational algorithm for holograms, we achieved hologram calculations at ~12 ms per hologram with 4 CPU cores.

A Reflectarray-Based Dual-Surface Reflector Working in Circular Polarization

Abstract: This paper presents the design of a dual-surface reflector (DSR) antenna working in dual circular polarization (CP) This DSR consists in a linearly polarized dual-gridded reflector (DGR) that is made of a solid parabolic reflector on which a reflectarray that reflects horizontal polarization (HP) and is transparent to the vertical polarization (VP) is affixed The conversion from linear polarization (LP) to CP of this antenna is realized by introducing a three-layer meander-line circular polarizer optimized for oblique incidence The antenna system was designed to generate two main beams in different directions and orthogonal CPs This antenna has been fabricated and characterized For the two polarizations, the realized gain is higher than 30 dB with a cross-polarization discrimination (XPD) higher than 27 dB in the 18–20 GHz frequency band

5.5 W continuous-wave TEM 00 -mode Nd:YAG solar laser by a light-guide/2V-shaped pump cavity

Abstract: A significant progress in TEM00-mode solar laser power and efficiency with heliostat–parabolic mirror system is reported here. A double-stage light-guide/2V-shaped pump cavity is used to efficiently couple and redistribute the concentrated pump light from a 2-m-diameter parabolic mirror to a 4-mm-diameter, 30-mm-length, 1.1 at.% Nd:YAG single-crystal rod. The light guide with large rectangular cross section enables a stable uniform pumping profile along the laser rod, resulting also in an enhanced tracking error compensation capacity. 5.5 W cw TEM00-mode solar laser power was measured at the output of a thermally near unstable asymmetric resonator. 150 and 157 % improvement in TEM00-mode solar laser collection efficiency and slope efficiency were obtained, respectively.

Device and method of manufacture or repair of a three-dimensional object

Abstract: The invention relates to a device (10) for the manufacture or repair of a three-dimensional object (36) comprising at least one installation space (12) for a layer-wise, successive solidification of at least a solidifiable material (16) in predefined areas for layerwise construction of the three-dimensional object (36) or layered repair of individual portions of the three-dimensional object (36) within the installation space (12); and at least one laser device (18) for generating at least one laser beam (20, 28, 30, 32, 40, 44, 46, 48, 50) by means of which a material layer (22) is locally fusible to an object layer and / or sinterability. The device (10) comprises at least one parabolic mirror (24, 34) or at least one parabolic mirror-like formed device, wherein an inner surface (42) of the parabolic mirror (24, 34) or the parabolic mirror-like device is oriented concave to the material layer (22) and the laser means (18) above and / or disposed outside of a building platform (14) such that the generated laser beam (20, 28, 30, 32, 40, 44, 46, 48, 50) via a beam deflection by means of the parabolic reflector (24, 34) or the parabolic mirror-like device on the material layer (22) is incident, wherein a projection (P1, P2) of the parabolic mirror (24, 34) or the parabolic mirror-like device is larger or smaller than at least one building area (B) of the building platform (14) which is designed for applying the material (16). The invention further relates to a method of manufacture or repair of a three-dimensional object (36).

Scheme for the detection of mixing processes in vacuum

Abstract: A scheme for the detection of photons generated by vacuum mixing processes is proposed to observe the quantum electrodynamic photon-photon interaction. The strategy consists in the utilization of a high numerical aperture parabolic mirror that tightly focuses two copropagating laser beams with different frequencies. This produces a very-high-intensity region in the vicinity of the focus, where the photon-photon nonlinear interaction can then induce new electromagnetic radiation by wave-mixing processes. These processes are investigated theoretically. The field at the focus is obtained from the Stratton-Chu vector diffraction theory, which can accommodate any configuration of an incoming laser beam. The number of photons generated is evaluated for an incident radially polarized beam. It is demonstrated that using this field configuration, vacuum mixing processes could be detected with envisaged laser technologies.

Shape control of slack space reflectors using modulated solar pressure.

Abstract: The static deflection profile of a large spin-stabilized space reflector because of solar radiation pressure acting on its surface is investigated. Such a spacecraft consists of a thin reflective circular film, which is deployed from a supporting hoop structure in an untensioned, slack manner. This paper investigates the use of a variable reflectivity distribution across the surface to control the solar pressure force and hence the deflected shape. In this first analysis, the film material is modelled as one-dimensional slack radial strings with no resistance to bending or transverse shear, which enables a semi-analytic derivation of the nominal deflection profile. An inverse method is then used to find the reflectivity distribution that generates a specific, for example, parabolic deflection shape of the strings. Applying these results to a parabolic reflector, short focal distances can be obtained when large slack lengths of the film are employed. The development of such optically controlled reflector films enables future key mission applications such as solar power collection, radio-frequency antennae and optical telescopes.

High power broadband light source

Abstract: A system for generating high power broadband light includes multiple light-sustained plasma light sources. Each one of the light-sustained sources includes a pumping source, a gas containment structure for containing gas and configured to receive pumping illumination from the pumping source and a parabolic reflector element arranged to collect at least a portion of the broadband radiation emitted by the generated plasma and form a collimated broadband radiation output. The system also including a set of optical elements configured to combine the collimated broadband outputs from the parabolic reflector elements of the multiple light-sustained plasma light sources into an aggregated broadband beam.

Ray Tracing Study of Optical Characteristics of the Solar Image in the Receiver for a Thermal Solar Parabolic Dish Collector

Abstract: This study presents the geometric aspects of the focal image for a solar parabolic concentrator (SPC) using the ray tracing technique to establish parameters that allow the designation of the most suitable geometry for coupling the SPC to absorber-receiver. The efficient conversion of solar radiation into heat at these temperature levels requires a use of concentrating solar collectors. In this paper detailed optical design of the solar parabolic dish concentrator is presented. The system has diameter mm and focal distance mm. The parabolic dish of the solar system consists of 11 curvilinear trapezoidal reflective petals. For the construction of the solar collectors, mild steel-sheet and square pipe were used as the shell support for the reflecting surfaces. This paper presents optical simulations of the parabolic solar concentrator unit using the ray tracing software TracePro. The total flux on the receiver and the distribution of irradiance for absorbing flux on center and periphery receiver are given. The goal of this paper is to present the optical design of a low-tech solar concentrator that can be used as a potentially low cost tool for laboratory scale research on the medium-temperature thermal processes, cooling, industrial processes, polygeneration systems, and so forth.

Optical design of an LED motorcycle headlamp with compound reflectors and a toric lens.

Abstract: An optical design for a new white LED motorcycle headlamp is presented. The motorcycle headlamp designed in this study comprises a white LED module, an elliptical reflector, a parabolic reflector, and a toric lens. The light emitted from the white LED module is located at the first focal point of the elliptical reflector and focuses on the second focal point. The second focal point of the elliptical reflector and the focal point of the parabolic reflector are confocal. We use nonsequential rays to improve the optical efficiency of the compound reflectors. The toric spherical lens allows the device to meet the Economic Commission of Europe, regulation no. 113 (ECE R113). Furthermore, good uniformity is obtained by using aspherical surface optimization of the same toric lens. The reflectivity of the reflector is 95%, and the transmittance of each lens surface is 98%. The average deviation of the high beam is 14.17%, and the optical efficiency is 66.45%.

Membrane-based deformable mirror: intrinsic aberrations and alignment issues

Abstract: A deformable mirror (DM) is an important component of an adaptive optics system. It is known that an on-axis spherical/parabolic optical component, placed at an angle to the incident beam introduces defocus as well as astigmatism in the image plane. Although the former can be compensated by changing the focal plane position, the latter cannot be removed by mere optical realignment. Since the DM is to be used to compensate a turbulence-induced curvature term in addition to other aberrations, it is necessary to determine the aberrations induced by such (curved DM surface) an optical element when placed at an angle (other than 0 deg) of incidence in the optical path. To this effect, we estimate to a first order the aberrations introduced by a DM as a function of the incidence angle and deformation of the DM surface. We record images using a simple setup in which the incident beam is reflected by a 37 channel micro-machined membrane deformable mirror for various angles of incidence. It is observed that astigmatism is a dominant aberration, which was determined by measuring the difference between the tangential and sagittal focal planes. We justify our results on the basis of theoretical simulations and discuss the feasibility of using such a system for adaptive optics considering a trade-off between wavefront correction and astigmatism due to deformation. (C) 2015 Optical Society of America

Mid-infrared spectroscopy-based trace gas detection method and device combining long-optical-path open light path with wavelength modulation technique

Abstract: The invention discloses mid-infrared spectroscopy-based trace gas detection method and device combining a long-optical-path open light path with a wavelength modulation technique. The detection device mainly consists of a continuous wave quantum cascade laser (CW-QCL), a laser driving and controlling unit, a plane mirror, a beam splitter, a visible laser, a reference gas pool, mercury, tellurium and cadmium (MCT) detector, an off-axis parabolic mirror, a corner reflector, a digital lock-in-amplifier and a computer. By using the CW-QCL as a light source, long-optical-path open light path is combined with the wavelength modulation technique to detect multi-component trace gas with high sensitivity.

Device and method for testing nonlinear polarization coefficient and absorption coefficient at terahertz band

Abstract: The invention relates to a device and a method for testing a nonlinear polarization coefficient and an absorption coefficient at a terahertz band. Laser is split into one path of pump light and one path of probe light by a beam splitter, wherein the probe light is reflected by a reflector group with an adjustable light path, is attenuated by a metal attenuation piece used for adjusting the beam intensity of incident laser and then is reflected to a high resistance silicon chip by the reflector; the pump light split by the beam splitter is reflected to enter a terahertz generation device so as to generate terahertz collimating light and the generated terahertz collimating light is focused on a sample rack at a focus position by a parabolic mirror by virtue of a terahertz polarizing plate, and the terahertz is converted into parallel light which is reflected to the high resistance silicon chip by another parabolic mirror; and the two paths of light are coincided at the high resistance silicon chip, are focused to a detection crystal by the parabolic mirrors, are focused to reach a Wollaston prism by virtue of a 1/4 wave plate after being scattered by using a convex lens and are respectively focused to two photoelectric detectors. A test sample only needs to be arranged at the position of the sample rack or the detection crystal in a light path, namely the nonlinear polarization coefficient and the absorption coefficient of the sample at the terahertz band can be tested.

OAM generator based on parabolic reflector and circular-ring-shaped array feed source

Abstract: The invention relates to an OAM generator based on a parabolic reflector and a circular-ring-shaped array feed source. The OAM generator shown in the picture (a) is composed of the circular-ring-shaped array feed source, the rotary parabolic reflector and a supporting mechanism. A structure of the circular-ring-shaped feed source is shown in the picture (b) and used for generating an original OAM radio frequency wave beam, N array elements distributed at equal intervals along the circumference are utilized, the stimulation amplitudes of the array elements are equal, and phases are shown in the mode shown in the specifications, wherein n represents the serial number of the array elements, l represents an OAM mode, a spiral phase item in the shape shown in the specifications can be formed in an array factor of the feed source, and an OAM radio frequency wave beam with the pattern number being l can be generated. When the OAM mode of the generator during working needs to be adjusted, only the phase relation among various array element currents needs to be reset. The rotating parabolic reflector is used for improving the quality of the OAM radio frequency wave beam and can narrow the OAM radio frequency wave beam, directionality and radiation gains can be improved, and the transmission distance of an OAM radio frequency carrier is increased. The OAM generator based on the parabolic reflector and the circular-ring-shaped array feed source can be applied to a wireless communication system, and compared with the existing wireless technology, the system capacity and the spectrum effectiveness can be greatly improved.

Intrinsic formation of electromagnetic divergence and rotation by parabolic focusing

Abstract: A linearly polarized electromagnetic wave is found to form divergent and rotation fields after focused by an off-axis parabolic mirror These distributions are generated within a subwavelength scale around the focus and at times when the electric field at the focus vanishes We theoretically and experimentally show that not only the direction but also the structure of the distributions varies with the incident polarization In addition, the distributions move in one direction with a phase velocity faster than the speed of light

Experimental investigation of effect of variation of mass flow rate on performance of parabolic dish water heater with non-coated receiver

Abstract: Concentrated solar collectors have high efficiency. Therefore, when concentrating collectors are used for water heating application, the system yields higher efficiency. From a hot climate perspective, there is a huge potential available for low-cost solar water heating systems. With the system described in this paper, the needs of hot water in the domestic sector can be fulfilled instantly. Authors used the parabolic dish collector for instant water heating. This paper describes the effect of variation of mass flow rate on performance of the parabolic dish water heater prototype. Design of the solar parabolic dish collector consists of a novel truncated cone-shaped helical coiled receiver made up of copper at focal point. This prototype was evaluated for its performance during the month of April and May 2010.

Optical model and numerical simulation of the new offset type parabolic concentrator with two types of solar receivers

Abstract: The paper presents a physical and mathematical model of the new offset type parabolic concentrator and a numerical procedure for predicting its optical performances. Also presented is the process of design and optical ray tracing analysis of a low cost solar concentrator for medium temperature applications. This study develops and applies a new mathematical model for estimating the intercept factor of the solar concentrator based on its geometrical and optical behavior. The solar concentrating system consists of three offset parabolic dish reflectors and a solar thermal absorber at the focus. Two types of absorbers are discussed. One is a flat plate circular absorber and the other a spiral smooth pipe absorber. The simulation results could serve as a useful reference for design and optimization of offset parabolic concentrators.

Detection device and detection method of off-axis parabolic mirror surface shape precision

Abstract: The invention relates to a detection device of off-axis parabolic mirror surface shape precision The detection device is composed of a Fizeau interferometer, a standard spherical mirror, an auxiliary concave spherical column, a base disc, a five-dimensional adjusting frame, a standard plane mirror, a two-dimensional adjusting frame, a supporting fixing bottom plate, a first base and a second base; the Fizeau interferometer is provided with the standard spherical mirror; the standard spherical mirror is a light beam output window of the Fizeau interferometer; the base disc is located below the Fizeau interferometer; the base disc is provided with an off-axis parabolic mirror to be detected and the auxiliary concave spherical column; the base disc is located at the top surface of the five-dimensional adjusting frame; the standard plane mirror is arranged at the bottom surface of the two-dimensional adjusting frame; and the two-dimensional adjusting frame is located above the off-axis parabolic mirror to be detected With the detection device of the off-axis parabolic mirror surface shape precision of the invention adopted, the surface shape precision of the off-axis parabolic mirror can be accurately and quickly detected

3D mapping of intensity field about the focus of a micrometer–scale parabolic mirror

Abstract: We report on the fabrication and diffraction-limited characterization of parabolic focusing micromirrors. Sub–micron beam waists are measured for mirrors with 10-μm radius aperture and measured fixed focal lengths in the range from 24 μm to 36 μm. Optical characterization of the 3D intensity in the near–field produced when the device is illuminated with collimated light is performed using a modified confocal microscope. Results are compared directly with angular spectrum simulations, yielding strong agreement between experiment and theory, and identifying the competition between diffraction and focusing in the regime probed.