Ellipsoidal Reflector Research Articles

Ray tracing in ellipsoidal reflectors for optical biometry of media.

In this paper, an analytical basis of ray tracing for optical biometry of media by ellipsoidal reflectors was developed. A ray-tracing algorithm was created, which involves determining the point of interaction of the incident beam with the ellipsoidal reflector, calculating the direction of the reflected beam, and determining the intersection point of the reflected ray with the second ellipsoid focal plane, taking into account the statistical weight of photons. For imaging in the optical biometry of media by ellipsoidal reflectors, the results of a real experiment and a Monte Carlo simulation for chicken muscle tissue samples of different thicknesses for the wavelength of 632.8nm are used.

Comparison-Based Optical Assessment of Hyperboloid and Ellipsoid Reflectors in a Beam-Down Solar Tower System With Linear Fresnel Heliostats

Beam-down concentrating solar tower (BCST) is known for its merits in easy installation and maintenance as well as lower convection heat loss of the central receiver (CR) when comparing to a traditional concentrated solar tower system. A point-line-coupling-focus (PLCF) BCST system using linear Fresnel heliostat (LFH) as the first stage concentrator (heliostat) and hyperboloid/ellipsoid reflector as the tower reflector (TR) is proposed and theoretically analyzed and compared in this paper. Theoretical investigation on the ray concentrating mechanism with two commonly used reflector structures, namely, hyperboloid and ellipsoid, is conducted utilizing Monte Carlo ray-tracing (MCRT) method. The objective of this study is to reveal the achievable optical performance of these types of TRs in the PLCF system considering the effect of LFH tracking errors on TR astigmatism as well as the differences of optical efficiency factors and power transmission in a large-scale biomimetic layout. Results indicate that the ellipsoid system is superior in terms of interception efficiency over the hyperboloid system due to smaller astigmatism at the CR aperture, especially at larger facet tracking error. However, the ellipsoid reflector shows significantly lower TR shading efficiency resulting from the larger TR surface area compared to that of the hyperboloid reflector. The total optical efficiency of the hyperboloid system is always better than that of the ellipsoid system, and this efficiency gap decreases as the ratio ε increases. The hyperboloid TR is proved to be more promising and practical for the PLCF system.

Quasi-optical frequency selective surface with phase compensation structure correcting the beam distortion.

In space-borne quasi-optical feed system, frequency selective surface (FSS) should meet both electrical properties and mechanical requirements. In the paper, we design and fabricate three FSSs to achieve these goals. We present a novel FFS with phase compensation structure correcting the beam distortion. The phase compensation structure consists of short-ended circular waveguide array, inspired by the idea of reflect array antenna. The first FSS meets the need of electrical performance, however, which is too weak to pass the mechanical test. The second one overcomes the former problem, but brings the aberration in reflection beam, due to the discontinuity of the reflection phase. The third one with phase compensation structure meets all the demands. The insertion phase of the unit cell compensates 119 and 183 GHz two reflection bands, reconfigures the field distributions on the cross section of beam waist simultaneously. What' more, this FSS extends the functionality of the original FSS. To some extent, the FSS with phase compensation structure shares the ellipsoidal reflector's pressure to adjust the beam.

Super directive Yagi–Uda nanoantennas with an ellipsoid reflector for optimal radiation emission

In this paper, the optimal designs of silicon Yagi–Uda nanoantennas (NAs) with an ellipsoid reflector have been proposed and analyzed using the 3D finite-difference time-domain method. The combination of nanospheres, nanowires, and ellipsoid reflectors has been employed to enhance the antenna directivity. The nanoantenna geometrical parameters are optimized using the particle swarm optimization algorithm. The optimized spherical NA with an ellipsoid reflector shows high directivity of 19.89, which is higher than the conventional counterpart by 65.75%. This enhancement is attributed to the different supported modes by the ellipsoid reflector, which increases the forward radiation and suppresses the backward one. Further, the optimized nanowire design with an ellipsoid reflector has achieved a directivity of 23.4. In addition, the radiation efficiency has been increased to 80.2% and 75.9% for optimized spherical and nanowire antennas, respectively. This enhancement is attributed to the efficient coupling between array elements as well as reduced sidelobe and back-lobe levels.

Design and Characterization of a 7.2 kW Solar Simulator

A 7.2 kW (electric input) solar simulator was designed in order to perform accelerated testing on absorber materials for concentrating solar power (CSP) technologies. computer-aided design (cad) software integrating a ray-tracing tool was used to select appropriate components and optimize their positioning in order to achieve the desired concentration. The simulator comprises four identical units, each made out of an ellipsoidal reflector, a metal halide lamp, and an adjustable holding system. A single unit was characterized and shows an experimental average irradiance of 257 kW m−2 on a 25.4 mm (1 in) diameter spot. Shape, spot size, and average irradiance are in good agreement with the model predictions, provided the emitting arc element model is realistic. The innovative four-lamp solar simulator potentially demonstrates peak irradiance of 1140 kW m−2 and average irradiance of 878 kW m−2 over a 25.4 mm diameter area. The electric-to-radiative efficiency is about 0.86. The costs per radiative and electric watt are calculated at $2.31 W−1 and $1.99 W−1, respectively. An upgraded installation including a sturdier structure, computer-controlled lamps, a more reliable lamp holding system, and safety equipment yields a cost per electric watt of about $3.60 W−1 excluding labor costs.

Theoretical Research on Ellipsoidal Structure Methane Gas Detection Based on Near Infrared Light Sources of PbSe Quantum Dots

To improve the precision and sensitivity of the detection in near infrared gas detection system, the selection of light source and design of gas chamber structure are two key links. In this paper, the near infrared (NIR) light sources fabricated with PbSe quantum dots (QDs) and a new gas cell structure using an ellipsoid reflector were designed to test the concentration of methane (CH4). The double wavelengths differential detection method was used in the paper. The signal wavelength is 1.665 μm from the NIR QD-based light source with 5.1 nm PbSe QDs. The reference wavelength is 1.943 μm from the NIR QD-based light source with 6.1 nm PbSe QDs. The experimental results show that the differential gain signal could be enhanced 80 times when the major axis, the focus, and the open length of the ellipsoid reflector are 4.18 cm, 3.98 cm, and 0.36 cm, respectively. The structure will be convenient for the signal amplifying, AD converting, and other process in the latter circuits, and therefore both the detection sensitivity and precision can be improved.

Dome-Shaped Ellipsoidal Reflector Antenna for UHF-RFID Readers With Confined Near-Field Detection Region

This letter proposes and demonstrates the concept of ellipsoidal reflector antennas for radio frequency identification reader applications at UHF band. The antenna can be potentially integrated with environmental structures to confine the reader detection region. The energy bounding characteristics result from the dual-focus feature of an ellipsoidal reflector in its near-field region, as the feed located at one of the two foci can create a focused field distribution around the other focus. An axial energy focusing is, thus, formed to confine the energy in a restricted region (near-field beam focusing), also minimizing the interference effects outside of the targeted area. Both numerical simulations and experimental results are presented to demonstrate the feasibility of this antenna concept.

A prediction model for two-dimensional pressure distribution from underwater shock wave focusing by an ellipsoidal reflector.

Underwater shock wave focusing by ellipsoidal reflector is an important method for medical treatment, detection, and acoustic warfare. However, its pressure field is difficult to predict due to complicated physics. In this study, the pressure by focusing is modeled based on theories of shock wave propagation, nonlinear reflection, and nonlinear focusing, and the calculation domain is determined by approximate equations of wave fronts and lines. The pressure field during the whole process is described by combining direct and focusing pressures in the time and space domains. On this basis, the focusing behavior is simulated, and obtained pressure profiles are compared with experimental results, and the influence of reflector length on focusing performance is also discussed. The results indicate that although there are some rough assumptions, this model can simulate the underwater focusing in some detail and does a good job of predicting the pressure distribution, especially for the positive peak pressure, with an error below 10%; as the reflector length increases, the dynamic focus tends to move linearly forward to the other geometric focus, and the pressure gain increases continuously but the growth rate decreases.

Confocal Terahertz Imaging of Ancient Manuscripts

Terahertz imaging has the potential to identify and decipher portions of ancient manuscripts, which may be unreadable at infrared and visible wavelengths. We use a scanning confocal terahertz microscope to scan a medieval parchment with music notes and pentagrams written with different inks. The microscope is based on a continuous-wave solid-state source at 0.3 THz, emitting in the free space with a horn antenna, and a high numerical-aperture ellipsoidal reflector. We present terahertz images with diffraction-limited lateral resolution of approximately 0.5 mm, where the different inks all give similar high contrast. Symbols written on the “verso” side of the parchment, barely glimpsed in the near-infrared photograph, leave a clear imprint in the terahertz images. Artifacts due to imperfect flatness of the parchment are also briefly discussed.

Novel solid-state solar thermal simulator supplying 30,000 suns by a fibre optical probe.

An efficient 3.168 kW solid-state solar thermal simulator (SSSTS), capable of supplying ~30,000 suns at a focal plane via a fibre optical delivery, has been developed. The source consists of 41 diode lasers, each operated at a wavelength and power of ~915 nm and ~80 watt, respectively. The SSSTS provides a semi-top hat radiation profile and can be focused to a diameter of ~10.5 mm. The electro-optical power efficiency of the SSSTS was evaluated to be 55%, where the maximum value of the uniform radiation flux exceeds 36.6MW/m2. As such, the present technology is relevant to solar thermal applications that are not wavelength-sensitive or where narrow line-width is desirable. Additionally, the fibre optical delivery feature enables ease of direction onto a suitable target, without the need of large ellipsoidal reflectors usually employed for the conventional arc solar simulators. To demonstrate the new SSSTS, ZnO:Zn particles were introduced into the path of the radiation to investigate the change in their own temperature by using the laser induced phosphorescence technique (LIP). The temperature of the averaged particles was measured at a different radiation flux over a ~87 mm2 cross sectional area. A change in the average particle temperature of up to 225°C was detected within the measurement volume when the SSSTS was operated at a flux of ~30,000 suns. The unique characteristics of the SSSTS, namely, the uniformity, high power flux, efficiency, ease of delivery, and precise control of the radiation flux responds to the current demands of solar thermal research.

A Quarter Ellipsoidal Reflector Enhancing Fluorescence Collection Efficiency For Multiphoton Microscopes

In this paper, we present a fluorescence collection enhancement method for multiphoton microscopy by a quarter ellipsoidal reflector (QER). It is proven to be compatible with commercially available two-photon microscopes without significant customization. The structure and working principle of the QER is demonstrated. A QER was fabricated to collect most backscattered photons not collected by an objective lens of an epifluorescence microscope and then reflected photons into an external detector. Fluorescence collection efficiency improvement of 2.75-fold in numerical simulation is obtained. The method is also validated by imaging turbid phantoms and ex vivo biological tissue. Quantum efficiency (QE) corrected experimental results obtained by our method are comparable with those obtained by a nondescanned detection (NDD) scheme of a commercially available multiphoton microscope system. Finally, our method is shown to have potential in neuroscience research for deep tissue imaging.

IMAGE PROCESSING AT ELLIPSOIDAL PHOTOMETRY

Ellipsoidal photometry using Charge-Coupled Device (CCD photometry), as a new kind of optical diagnostics of scattering media in reflected and/or transmitted light, requires the development of specific principles of data analysis. The object of this work was substantiation the principles of ellipsoidal CCD photometry at implementation of a new data processing method of spatial distribution of scattered optical flux. Procedure of photometric analysis include the steps of determining the image significance, as well as the size, configuration and illuminance in its respective areas with regard to the criteria to optimize the shape and sensitivity of the zone. Zone analysis schemes of photometric images for media with a radially symmetric and directed scattering are developed. Recommended to use the method of comparison with etalon for studies the technical surfaces and turbid media to determine their roughness and optical characteristics, respectively. During the analysis of biological media, there is a possible of prognosis the spatial distribution of the brightness of the image by means of statistical modeling of optical radiation in the system «biological medium + ellipsoidal reflector». That confirmed by comparing results of the numerical (direct Monte Carlo simulation) and the real experiment for samples different thickness of muscle porcine tissue in vitro. Parameters of the optical radiation, which used as input data for the simulation, correspond to a laser wavelength of 632.8 nm with a Gaussian distribution profile of power of 2 mW. As a CCD detector was used monochrome camera DMK-21Au04.AS, and ellipsoidal reflector with an eccentricity of 0.66 and working aperture of 33.75 mm. Obtained results of zone distribution of illumination across the field in real experimental photometric images during biometrics showed correlation with the total transmission, absorption and diffuse scattering coefficients. This interdependence may be important part of improvement inverse methods of determination the optical parameters of biological media.

Design and Implementation of Monopulse Antenna for Submillimeter Wavelengths’ Application

This communication presents the methodology design and implementation of a monopulse antenna based on quasi-optical (QO) technology at submillimeter wavelengths. The designed monopulse antenna consists of QO sum–difference comparator, beam-waveguide (BWG) feed systems and Cassegrain dual reflector. The BWG system between the feed horn and QO sum–difference comparator is composed of spherical thin lens, ellipsoid reflector mirrors, and plane mirrors. Four ellipsoid reflector mirrors are employed for the BWG feed system between QO sum–difference comparator and Cassegrain dual reflector. The parameters of all components are determined by using Gaussian beam theory. Then, the antenna configuration is simulated and slightly optimized by finite-difference time-domain (FDTD) method combining with Stratton-Chu formulas. The simulated results have good performance at the center frequency of 375 GHz, with the sidelobe levels below $-15.4$ dB in sum patterns, the maximum null depth is approximately $-34.0$ dB and lower than 0.05-dB amplitude imbalance in difference patterns. A prototype of the proposed monopulse antenna was manufactured and measured in the radiating near-field zone. The presented measurement results agree well with the corresponding simulated results and validate the correctness of design indirectly. It indicates that this type of monopulse antenna presents an excellent candidate for tracking systems at submillimeter wavelengths.

Characterization of a 6 kW high-flux solar simulator with an array of xenon arc lamps capable of concentrations of nearly 5000 suns.

A systematic methodology for characterizing a novel and newly fabricated high-flux solar simulator is presented. The high-flux solar simulator consists of seven xenon short-arc lamps mounted in truncated ellipsoidal reflectors. Characterization of spatial radiative heat flux distribution was performed using calorimetric measurements of heat flow coupled with CCD camera imaging of a Lambertian target mounted in the focal plane. The calorimetric measurements and images of the Lambertian target were obtained in two separate runs under identical conditions. Detailed modeling in the high-flux solar simulator was accomplished using Monte Carlo ray tracing to capture radiative heat transport. A least-squares regression model was used on the Monte Carlo radiative heat transfer analysis with the experimental data to account for manufacturing defects. The Monte Carlo ray tracing was calibrated by regressing modeled radiative heat flux as a function of specular error and electric power to radiation conversion onto measured radiative heat flux from experimental results. Specular error and electric power to radiation conversion efficiency were 5.92 ± 0.05 mrad and 0.537 ± 0.004, respectively. An average radiative heat flux with 95% errors bounds of 4880 ± 223 kW ⋅ m(-2) was measured over a 40 mm diameter with a cavity-type calorimeter with an apparent absorptivity of 0.994. The Monte Carlo ray-tracing resulted in an average radiative heat flux of 893.3 kW ⋅ m(-2) for a single lamp, comparable to the measured radiative heat fluxes with 95% error bounds of 892.5 ± 105.3 kW ⋅ m(-2) from calorimetry.

Study of reflection-typed LED surgical shadowless lamp with thin film Ag-based metallic glass

Abstract Traditional surgical shadowless halogen lamp can cause mercury pollution and increase heat radiation. In this study, single one light-emitting diode (LED) is used as light source for shadowless surgical light, whose light performance is comparable with traditional halogen light bulbs. This surgical shadowless lamp with multi-focal ellipsoidal curve reflector was designed and made. Reflection-typed shadowless surgical light is better than projection-typed one. This design can reduce significantly the use of LEDs. Various recipes of Ag–Cu–Al thin film metallic glass (Ag-based TFMG) were determined and coated on the curve as reflector materials, possessing great mechanical strength and anti-bacterial effect. The Ag-based can affect the light temperature and light color. Appropriate alloy elements of this metallic glass could be formulated to absorb IR range wavelength to reduce the wound damage during surgery. For the optical measurement, the central illuminance (Ec) was 110,500 lx, d 50 /d 10 was 58.9% and working depth was 32.8 cm. The shadow dilution with single mask and double masks were 58.96% and 56.16%, respectively. Then, for the combination of tubes, the shadow dilution of lamp with single mask and double masks were 57.46% and 58.03%, respectively. The experimental results meet the rule of IEC-60601-2-41.

Study on the ellipsoidal reflector interception methods for quasi-optical systems

For quasi-optical system,in order to improve the application performance of quasi-optical system on weather satellites,a new method of intercepting ellipsoidal reflectors that can effectively reduce extra energy loss in transmission and decrease the sizes of reflectors was proposed. Ellipsoidal reflectors are important optical elements for light beam transmission in quasi-optical system. The traditional method of intercepting ellipsoidal reflectors would introduce extra energy loss which deteriorates the performance of the whole system.To solve this problem,by building a Gaussian beam transmission model,traditional method of designing ellipsoidal reflectors was improved—translating ellipsoidal reflectors according to the beam waist radius. Simulations reveal that improved method performs better than traditional method—it not only reduces the maximal electrical level from- 30 d B to- 35 d B but also decreases the size of mirror by 10% to 30% which will benefit the electrical performance of quasi-optical system as a whole. All in all,improved method makes for decreasing the size and increasing signal-to-noise ratio( SNR) of the whole system,which ensures energy maintenance of weak meteorological signals during transmission process and improved method is of great significance to improve the properties of the quasi-optical system.

Time-resolved spectra of solar simulators employing metal halide and xenon arc lamps

The time-resolved spectra of the irradiation emitted from solar simulators employing the two types of high-intensity discharge arc lamps that are commonly used in solar simulators, i.e. metal halide (here 6kW) and xenon arc (here 5kW) lamps, are reported. The lamp emission was recorded by a fast-response photodiode, which reveals that the amplitude of oscillating irradiation intensity from the metal halide lamp is approximately 60% of the peak intensity, while its oscillation frequency is twice of the frequency of the AC power supply, here 100Hz. The irradiation of the xenon arc lamp is powered by a modulated DC supply to oscillate at 300Hz, with an amplitude that is found to be only approximately 9% that of the peak intensity. An intensified CCD camera, which was coupled with a spectrometer operating in a range of 350–900nm, was synchronized with the lamp to provide phase-resolved spectra. The irradiation from the xenon arc lamp was found to be spectrally stable with time; while that from the metal halide lamp varies significantly throughout oscillation cycle, especially at the shorter-wavelengths of below 550nm. All spectra were calibrated to reveal that the time-averaged spectrum of the simulator with a metal halide lamp matches the solar spectrum significantly better than does that from a xenon arc lamp. The reflecting surface of polished ellipsoidal reflector was found to reduce the intensity of selected frequency bands by up to 10%, while that from both the polished ellipsoidal reflector and conical concentrator was found to reduce the intensity in selected frequency bands by up to 20%.

Effects of Burst Electromagnetic Wave Focusing and Their Combination With Nanosecond Pulsed Electric Fields on HeLa S3 Cells

Burst electromagnetic waves focusing, nanosecond pulsed electric fields (nsPEF), and their combinations were applied to HeLa S3 cells to investigate their respective biological effects. The research was motivated by its application for cancer therapy. Burst electromagnetic waves, characterized by high-frequency (800 MHz) and narrow-band signals, were applied through a focusing system consisting of an ellipsoidal reflector and a radiating antenna. Burst widths of electromagnetic waves were adjusted to 1 and 5 ms. For nsPEF exposure, a magnetic pulse power modulator with an 80-ns pulsewidth and repetition frequencies of 0.5 and 1 pulse per second was employed. Cervical cancer cells (HeLa S3) subjected to electric fields were cultured in an incubator for 24 h and stained using propidium iodide to monitor the cell death rate. Sole application of burst electromagnetic waves was found not to change the cancer cell survival, while sole application of nsPEF suppressed the cells growth. The combination of nsPEF and focused burst electromagnetic wave was found to be very effective in producing maximum cell death rate. The results show the importance of the exposure combination component, as a first step, to design a more efficient and less-invasive cancer therapy system.

Optical Design of Multisource High-Flux Solar Simulators

We present a systematic approach to the design of a set of high-flux solar simulators (HFSSs) for solar thermal, thermochemical, and materials research. The generic simulator concept consists of an array of identical radiation modules arranged in concentric rows. Each module consists of a short-arc lamp coupled to a truncated ellipsoidal specular reflector. The positions of the radiation modules are obtained based on the rim angle, the number of concentric rows, the number of radiation modules in each row, the reflector radius, and a reflector spacing parameter. For a fixed array of radiation modules, the reflector shape is optimized with respect to the source-to-target radiation transfer efficiency. The resulting radiative flux distribution is analyzed on flat and hemispherical target surfaces using the Monte Carlo ray-tracing technique. An example design consists of 18 radiation modules arranged in two concentric rows. On a 60-mm dia. flat target area at the focal plane, the predicted radiative power and flux are 10.6 kW and 3.8 MW m−2, respectively, and the predicted peak flux is 9.5 MW m−2.

Tensile testing of materials at high temperatures above 1700 °C with in situ synchrotron X-ray micro-tomography.

A compact ultrahigh temperature tensile testing instrument has been designed and fabricated for in situ x-ray micro-tomography using synchrotron radiation at the Advanced Light Source, Lawrence Berkeley National Laboratory. It allows for real time x-ray micro-tomographic imaging of test materials under mechanical load at temperatures up to 2300 °C in controlled environments (vacuum or controlled gas flow). Sample heating is by six infrared halogen lamps with ellipsoidal reflectors arranged in a confocal configuration, which generates an approximately spherical zone of high heat flux approximately 5 mm in diameter. Samples are held between grips connected to a motorized stage that loads the samples in tension or compression with forces up to 2.2 kN. The heating chamber and loading system are water-cooled for thermal stability. The entire instrument is mounted on a rotation stage that allows stepwise recording of radiographs over an angular range of 180°. A thin circumferential (360°) aluminum window in the wall of the heating chamber allows the x-rays to pass through the chamber and the sample over the full angular range. The performance of the instrument has been demonstrated by characterizing the evolution of 3D damage mechanisms in ceramic composite materials under tensile loading at 1750 °C.