Showing papers on "Parabolic reflector published in 2008"

Tighter focusing with a parabolic mirror

Abstract: We demonstrate experimentally and theoretically that a parabolic mirror (PM) with a high numerical aperture (NA) of 1 focuses a radially polarized laser mode to the smallest diffraction-limited spot at a fixed NA and wavelength, having an area of 0.134 lambda(2). The measurements were performed with a confocal microscope, using the PM as a focusing and collecting element. The results stand in accordance with the theoretical calculations presented by Davidson and Bokor [Opt. Lett. 29, 1318 (2004)], who predicted a reduction in the total focal spot size of 43% as compared with an aplanatic lens.

High NA particle- and tip-enhanced nanoscale Raman spectroscopy with a parabolic-mirror microscope.

Abstract: Summary Detecting efficiently the plasmon-enhanced Raman signal of molecules created in the nanometre-sized gap between a metal nanoparticle or the apex of a sharp tip and a metal surface is the key problem in particle- or tip-enhanced local surface spectroscopy (Pettinger et al., 2004; Roth et al., 2006). The optical excitation field has to be polarized along the gap, and the field emerging from the gap has to be observed from the side. These geometrical restrictions usually limit the numerical aperture of the lens used for exciting the gap and collecting the scattered photons created in the gap. We present a novel method to overcome this problem. The solution is based on a confocal optical microscope with a high numerical aperture parabolic mirror for excitation and detection. Localized plasmons can be efficiently excited parallel to the surface normal by illuminating the parabolic mirror with a radially polarized doughnut mode and the field emerging sidewise from the gap can be efficiently collected by the rim of the parabolic mirror and directed to the detection system. First results on particle- and tip-enhanced Raman spectroscopic measurements of benzotriazole molecules adsorbed on gold films are presented.

Slope Measurements of Parabolic Dish Concentrators Using Color-Coded Targets

Abstract: A new short, yet highly accurate method for measuring the slope errors of parabolic dish concentrators has been developed. This method uses a flat target with colored stripes that is placed close to the focal plane and a digital camera located at an observation point on the optical axis at some distance from it. A specially developed image analysis algorithm detects the different colors in the images of the reflection of the target in the concentrator and assigns them their known position on the color target. This information, along with the geometric relationship between the components of the measurement setup and the theoretical parabolic shape of the concentrator, is used to calculate the normal vectors of the concentrator surface. From these normal vectors the radial and tangential slopes can be calculated and compared to the design values of the concentrator. The resulting slope errors not only give the total concentrator error for general characterization of the dish, but also indicate systematic errors in fabrication and mounting with high spatial resolution. In order to verify the quality of the results obtained, a ray-tracing code was developed that calculates the flux distribution on planes perpendicular to the optical axis. Measured slope errors of a DISTAL-2 dish concentrator are presented and the calculated flux distributions are compared to measured flux distributions. The comparison shows excellent agreement in the flux distribution on the absorber plane. This verifies the promising potential of this method for fast, highly precise measurement of imperfections in dish concentrator shape.

Integrated Small-Sized Semiconductor Ring Laser With Novel Retro-Reflector Cavity

Abstract: We have successfully designed and fabricated 1.55-mum semiconductor ring lasers with novel parabolic mirror retro-reflector cavities. The parabolic mirror is designed by means of ray-tracing and finite-difference time-domain to optimize its shape and position. The fabricated devices, with a range of sizes down to an equivalent circular ring radius of 16 mum, operate in continuous-wave mode at room temperature. Threshold current of 22 mA and output power up to 140 muW have been achieved for the smallest device. These devices are suitable for high-speed all-optical signal processing and digital photonic functions.

Flat Facet Parabolic Solar Concentrator With Support Cell for One and More Mirrors

Abstract: Parabolic dish solar concentrators are very expensive devices with a cost of up to a half of the total cost of a solar power station. The specific technology of parabolic mirror manufacturing makes the decrease of the cost very problematic. Even in mass production the cost of a parabolic mirror is estimated as $500 per square meter. There is another way to make a parabolic concentrator by approximating a parabolic surface with large number of small flat mirrors. We created a small prototype of this type of solar concentrator which contains 24 flat mirrors in the form of equilateral triangles with side length of 50mm. This prototype has special nuts to adjust the positions of the nodes in the points of connections of the apexes. These nuts make it possible to approximate the parabolic shape in an easy and inexpensive way.

Interferometric null test of a deep parabolic reflector generating a Hertzian dipole field.

Abstract: We report on interferometric characterization of a deep parabolic mirror with a depth of more than five times its focal length. The interferometer is of Fizeau type; its core consists of the mirror itself, a spherical null element, and a reference flat. Because of the extreme solid angle produced by the paraboloid, the alignment of the setup appears to be very critical and needs auxiliary systems for control. Aberrations caused by misalignments are removed via fitting of suitable functionals provided by means of ray tracing simulations. It turns out that the usual misalignment approximations fail under these extreme conditions.

Retro-directive ground-terminal antenna for communication with geostationary satellites in slightly inclined orbits

Abstract: A retro-directive antenna for communicating with a geostationary satellite autonomously detects the direction from which a signal is received, and transmits a beam that points back along the same direction. An array feed is used to illuminate a parabolic reflector. Each feed element of the retro-directive antenna is associated with a unique pointing direction of the beam in the far field. As the transmit energy is switched to different feed elements, the far-field beam is scanned, making it possible to track a geostationary satellite in a slightly inclined orbit. This eliminates the need for mechanical tracking and maintains high antenna gain in the direction of the geostationary satellite. The use of a toroidal reflector with multiple linear array feeds spaced in the azimuth direction enables multi-beam operation, allowing multiple geostationary satellites, spaced by up to fifteen beam widths in azimuth, to be tracked simultaneously and independently.

Gamma bang time/reaction history diagnostics for the National Ignition Facility using 90° off-axis parabolic mirrorsa)

Abstract: Gas Cherenkov detectors (GCDs) have been used to convert fusion gamma into photons to achieve gamma bang time and reaction history measurements. The GCDs designed for OMEGA used Cassegrain reflector optics in order to fit inside a 10in. manipulator. A novel design for the National Ignition Facility using 90° off-axis parabolic mirrors will increase light collection efficiency from fusion gammas and achieve minimum time dispersion. The broadband Cherenkov light (from 200to800nm) is relayed into a high-speed detector using three parabolic mirrors. Because light is collected from many source planes throughout the CO2 gas volume, the detector is positioned at the stop position rather than at an image position. The stop diameter and its position are independent of the light-generation location along the gas cell. The current design collects light from a 100mm diameter by 500mm long gas volume. Optical ray tracings demonstrate how light can be collected from different angled trajectories of the Compton electrons as they fly through the CO2 gas volume. A cluster of four channels will allow for increased dynamic range as well as for different gamma energy threshold sensitivities.

Enclosed solar collector

Abstract: A solar collector includes a plurality of elongated parabolic reflectors mounted within a glass-topped enclosure for pivotal movement such that each reflector is incrementally pivoted throughout the course of a day to remain substantially perpendicular to the sun. The incremental pivotal movement is caused by a motor energized from a solar switch having solar cells that also pivot throughout the day so that in one position of the switch, no electricity is being generated and transferred to the motor, but in a second position, the switch receives solar radiation and energizes the motor to again incrementally pivot each reflector along with the solar switch. The reflectors are therefore incrementally pivoted throughout the course of a day to follow the sun for optimal collection of solar radiation which is used to heat liquid carried by tubes positioned at the axis of generation of the parabolic reflectors and/or strips of solar cell material so that electricity can be generated alone, liquid heated alone, or liquid heated and electricity generated simultaneously.

Scattering of a line source by a cylindrical parabolic impedance surface.

Abstract: The scattering of the radiated fields of a line source by a cylindrical parabolic reflector, which has impedance boundary conditions on its surface, is obtained by using the surface integrals of the modified theory of physical optics. The reflected geometrical optics and edge diffracted fields are evaluated by using the asymptotic methods. The scattered fields are plotted numerically for various parameters such as surface impedance and angles of the edges.

Fiber-to-waveguide coupler based on the parabolic reflector

Abstract: We present a fiber-to-waveguide coupling structure, the so-called vertical J coupler, based on the parabolic reflector. The device addresses the multiple objectives of high coupling efficiency, large bandwidth operation, polarization insensitivity, and compact footprint. The optical mode emanating from a fiber arranged normal to the plane of the substrate is incident underneath the parabolic reflector, turned through 90 degrees and focused into a dielectric waveguide. The viability of the coupler is demonstrated by finite-difference time-domain electromagnetic simulation as well as preliminary fabrication and optical testing of the device.

Focal waveforms for various source waveforms driving a prolate‐spheroidal impulse radiating antenna (IRA)

Abstract: [1] Impulse radiating antennas (IRAs) are designed to radiate very fast pulses in a narrow beam with low dispersion and high field amplitude. For this reason they have been used in a variety of applications. IRAs have been developed for use in the transient far-field region using parabolic reflectors. However, in this paper we focus in the near field region and develop the field waveform at the second focus of a prolate-spheroidal IRA. Certain skin cancers can be killed by the application of a high-amplitude electric field pulse. This can be accomplished by either inserting electrodes near the skin cancer or by applying fast, high-electric field pulses without direct contact. We investigate a new manifestation of an IRA, in which we use a prolate spheroid as a reflector instead of a parabolic reflector and focus in the near-field region instead of the far-field region. This technique minimizes skin damage associated with inserting electrodes near the tumor. Analytical and experimental behaviors for the focal waveforms of two and four-feed arm prolate-spheroidal IRAs are explored. With appropriate choice of the driving waveform we maximize the impulse field at the second focus. The focal waveform of a prolate-spheroidal IRA has been explained theoretically and verified experimentally.

Capillary μFocus X-ray lenses with parabolic and elliptic profile

Abstract: The parameters of two elliptical poly-capillary lenses and one mono-capillary parabolic lens were characterized at the optical test bench of the BM05 ESRF beamline and at the BESSY μFocus beamline. The poly-capillary lenses with an input aperture of ∅ 5–6 mm have shown a focal spot size (FWHM) on the order of 6–20 μm with a gain factor of about 600–700 in a wide energy range. For the first time the parabolic mono-capillary lens has shown a focal spot size of

High Frequency Expressions for the Field in the Caustic Region of a Parabolic Reflector Coated with Isotropic Chiral Medium

Abstract: High frequency field expression for a parabolic reflector are derived using Maslov's method. Parabolic reflector has been coated with isotropic and homogeneous chiral medium. The effects of thickness of chiral layer, chirality parameter of the chiral medium and permittivity of the medium are studied.

Automatic Satellite Tracking System

Abstract: A satellite tracking system for tracking a synchronous satellite includes a satellite antenna system movably supported on a roof of a vehicle via a roof frame to move between an operation position and a folded position. At the operation position, the satellite antenna system is rotated on the roof frame to adjust a horizontal orientation of a parabolic reflector of the satellite antenna system while the parabolic reflector is pivotally lift at a predetermined inclination angle to align with the satellite. At the folded position, the parabolic reflector is pivotally dropped down until the parabolic reflector faces downwardly to the roof of the vehicle to conceal a signal transmitting device of the satellite antenna system between the parabolic reflector and the roof of the vehicle. Therefore, the satellite antenna system provides a relatively low profile at the folded position when the vehicle travels.

Micro-facet solar concentrator

Abstract: A low-cost micro-facet solar concentrator is proposed. A large number of small flat mirrors are situated in a parabolic surface to approximate a large parabolic mirror. Low-cost commercial flat mirrors can be used for manufacturing such concentrators. Geometrical analyses show that this concentrator will have a concentration rate of some hundreds of suns. The problems of production of micro mirrors, support components, and the automatic assembly of the concentrator are discussed. Rough estimations show that the cost of the concentrator should be ∼$55 per square metre of concentrator surface.

Update on two-year performance of 120 kWp concentrator PV systems using multi-junction III–V solar cells and parabolic dish reflective optics

Abstract: Multi-junction III–V solar cells have been in operation for the last two years in several 500X dish concentrator PV systems using reflective optics. The performance monitoring of these CPV systems on a 15-second basis has accumulated a very large amount of data and allowed for analysis of the influence of atmospheric parameters to the system efficiency. Dense array modules are assembled into large receivers of approximately a quarter of square meter in size and with a typical efficiency of 31.7% and power output of 36.5kWp under Standard Operating Conditions (SOC, 1000W/m2, AM1.5D, low AOD and 21°C cell temperature). At Normal Operating Cell Temperature (NOCT 53°C), the receiver efficiency and power output become 30% and 35.4kW. The DC efficiency of the dish unit is 24.5% at SOC. More interestingly, the specific Energy Production Rate (EPR) of each dish, being the ratio of the daily energy output and the daily incident direct-beam energy (DNR), was measured. In average, over a two-year period and over four dishes, the EPR was 27.5 m2, corresponding to the equivalent aperture of a 100%-efficient solar energy converter. The annualised efficiency of these CPV systems is 21.1%. A new generation of dense array modules have demonstrated efficiency of 36.1% at 50W/cm2 and 21°C. Also, a new redesigned optics has recently been implemented on one of the dishes and has demonstrated a significant boost in efficiency, bringing the SOC efficiency to 26.2% and an expected EPR of 30 m2. We expect that combining the 2nd generation modules with the redesigned optics would improve the DC efficiency to 28% at SOC.

Gas solid two-phase flow granule density detection device and method based on terahertz transmission and detector

Abstract: The utility model relates to a device and a method for detecting the particle concentration of the gas-solid flow based on the terahertz (THz) electromagnetic emission and detection device, comprising a femto-second laser, a coupling transmission optical fiber, a photoconductive antenna type THz electromagnetic emitter, an optical delay unit, an off-axis parabolic mirror, a THz detector, a phase-lock amplifier, a high-frequency power amplifier and a data acquisition and processing system controlled by a computer. The utility model reflects the THz wave sent from the THz electromagnetic emitter in parallel via the off-axis parabolic mirror and the THz wave through the gas-solid flow is condensed to the THz detector via the off-axis parabolic mirror. The particle concentration of the gas-solid flow on the section of a pipeline can be calculated with different models according to the measured THz time domain signal. The utility model has the advantages of simple structure, convenient installation, high measuring accuracy, safe use, and wide application in fields of petroleum, chemical industry, energy, metallurgy and environment.

Incident optical system and raman scattering measurement apparatus

Abstract: PROBLEM TO BE SOLVED: To provide an incident optical system and a Raman scattering measurement apparatus for correctly controlling an incident angle of totally-reflected light. SOLUTION: The incident optical system includes: a light transmitting member 11 having a planar sample surface 111 and a hemispherical curved surface 112; and a parabolic mirror 12 having a reflection surface 121 as a portion of a rotational parabolic surface 122. The curved surface 112 faces the reflection surface 121. The center of a sphere on the sample surface 111 corresponds to a focus 125 of the rotational parabolic surface 122. A laser light flux (a light flux) L is parallel to a rotational symmetric axis 123 of the rotational parabolic surface 122, reflected by the reflection surface 121, and collected to the focus 125 on the sample surface 111. Raman scattering light is generated from a sample S by evanescent light generated by a total internal reflection of the laser light L on the sample surface 111. Since an optical axis of the laser light L is moved in the direction in which it approaches or leaves the rotational symmetric axis 123, the incident angle of the laser light L to the sample surface 111 can be changed. COPYRIGHT: (C)2010,JPO&INPIT

Device for detecting light axis parallelism of laser and visual light system

Abstract: The present invention relates to an equipment for detecting the optical axle parallelism of a photoelectric detecting and control equipment, in particular to a device for detecting the optical axle parallelism of a laser and visible light system, and the device consists of a reflecting type collimator, a light source and a computer. The reflecting type collimator is formed by the way as follows: a light dimming piece, a hyperbolic mirror, a parabolic mirror with a centre hole, and a dichroic mirror forming a 45 degree angel with a light pipe optical axle are arranged from the closing-in end of the light pipe to the bottom in sequence, a CCD device is arranged on the focal plane of a collimation light path composed of the parabolic mirror and the hyperbolic mirror, a target surface center is positioned on the light pipe optical axle, and a cross fiber differentiate plate is arranged on a conjugating focal surface composed of the dichroic mirror; the light source is arranged at the light pipe position corresponding to the cross fiber differentiate plate; the image output end of the CCD device is connected with the image collection card of the computer. The present invention provides the effective technical method in order to realize the detection of laser of the photoelectric detecting and control equipment and the optical axle parallelism of a visual system.

Display device and lighting device

Abstract: PROBLEM TO BE SOLVED: To provide a lighting device for a liquid crystal dsiplay device having high light transmittance, low power consumption and uniform luminance distribution and achieving high optical design efficiency and a low price, and to provide an optical device. SOLUTION: Parallel light collimated by an off-axis parabolic mirror 10 is reflected by a cylindrical convex total reflection surface 5 disposed in a rice terrace shape to expand a luminous flux in a width of a liquid crystal sub pixel and luminous flux density made incident on a liquid crystal is made uniform by increasing reflection surface step differences of the cylindrical convex surface in inverse proportion to the luminous flux density. With a basic unit in which a light quantity of 1/3 of emission light of a rice terrace-shaped light guide plate 1 is transmitted through a sub pixel existing in a perpendicular direction of an incident part and in which a light quantity of 2/3 of one is reflected by a reflection surface 7 inclined in a stripe direction, reflected by a liquid crystal facing side reflection surface 8 in a stripe distributing element 2 and made incident on two liquid crystal sub pixels, the emission light quantity is distributed to three sub pixels in the same stripe. Distribution to separated positions is made possible by a reflection system of a transmission/reflection separation part and color display is made possible without using color filters by adopting a plurality of color light sources. COPYRIGHT: (C)2009,JPO&INPIT

A X-Band Planar Transmit-Array

Abstract: Planar arrays are a very interesting option to substitute reflector antennas because of their well-known characteristics of low profile, potential low cost, reliability and flexibility in achieving contoured beams and multiple beams with a simple planar geometry. Suitable solutions using planar antennas for space applications have been proposed using reflect-arrays with countered beams and multibeam. Another proposed solution consists of transmit arrays. In this case, the antenna acts as a lens [1]. This consists of a periodic planar array having two patch antennas connected by a line. One element receives the signal from –z direction and the other transmits the signal in the +z direction. By a proper selection of the phase delay in the connection line, the phase distribution in the transmitting array can be adjusted. In an equal output phase configuration the transmitting array behaviour would be similar to the obtained with a parabolic reflector, having the advantage of removing the feed blockage.

Solar power plant with rotation device

Abstract: The invention relates to a solar power plant with a rotary device having which panels, which are preferably formed with uniaxially guided parabolic trough, the parabolic trough having curved mirrors which are connected to each other and focus the sunlight on a running in the focal line of the absorber tube which the concentrated solar radiation into heat converts and outputs it to a circulating heat transfer medium. The invention is characterized in that each absorber tube is connected to a flexible metal hose, which metal hose is sealingly guided by a rotating device, which is necessarily rotated by a rotary drive of the parabolic mirror with.

Long-range, handheld searchlight

Abstract: A handheld searchlight for producing a high intensity beam of light output has an elongated housing including a handle portion for gripping by a user. A head has a window opening for transmitting a light beam. There is a mechanical coupling between the housing and the head. A parabolic reflector is mounted in the head facing the window and has an aperture for accommodating a high intensity lamp. The reflector has a longitudinal optical axis. The rotation of the head about the coupling causes movement of the parabolic reflector relative to the lamp along the optical axis thereby changing a spread of the high-intensity light beam. The searchlight further includes a rotatable bezel ring mounted on the head and a filter ring mount connected to the rotatable bezel. An optical filter is mounted in the filter ring mount.

Calibration of Cylindrical Reflector Antennas With Linear Phased Array Feeds

Abstract: The phase of the elements of a phased array feed is optimized to yield a maximum directivity for front fed and offset cylindrical parabolic reflector antennas. Calibration improves the reflector antenna performance, especially for front fed reflectors with larger feeds.

Analysis of High Frequency Field of Perfect Electromagnetic Conductor (PEMC) Parabolic Reflector Placed in Homogenous Chiral Medium

Abstract: High frequency fields of PEMC parabolic reflector are studied. The reflector is placed in homogenous and reciprocal chiral medium. Two cases are analyzed. Firstly, the chirality parameter is adjusted to support positive phase velocity (PPV) propagation for both the modes travelling in the medium. Secondly, the chirality parameter is adjusted so that one mode travels with positive and the other with negative phase velocity (NPV). The line plots of reflected field in the focal plane of the reflector are obtained for different values of admittance of the PEMC and chirality parameter.

Half parabolic dish reflector with planar reflector solar smelter

Abstract: Melting metals using the sun's energy is not new, but is new is making the technology ergonomic, and easy to use. Invented is a half-circular-planar-reflector with a cut-a-way-triangle, hinged and attached a half-shell-parabolic-reflector. When the sun is overhead, the sun's energy reflects off the flat half-circular-planar-reflector to a half-shell-parabolic-dish-reflector, which redirects the sun's energy to a crucible for smelting metals, which is also the focus of the sun's energy. The entire assembly rotates on top of a turntable, which can be steel wheel, floating on compressed air, bicycle wheels, or other suitable methods. The entire assembly rotates about a crucible located at the focal of the sun's energy. A smaller version of the smelter can be used for solar cooking.