Corner Reflector Array Research Articles

Air Floating Image based on a Dihedral Corner Reflector Array

Air Floating Image based on a Dihedral Corner Reflector Array

Radially arranged dihedral corner reflector array for wide viewing angle of floating image without virtual image.

We proposed a new type of dihedral corner reflector array (DCRA) called "radially arranged DCRA". Our radially arranged DCRA could display a floating, three-dimensional image with a wide viewing angle without producing virtual images because dihedral corner reflectors were radially arranged for the designed paths of rays. In this research, we designed a reflector array pattern and evaluated the viewing angle of the floating image displayed by our radially arranged DCRA. During evaluation, we measured the reflection ratio of the radially arranged DCRA and demonstrated a floating image. Compared with a conventional DCRA, our radially arranged DCRA could expand the viewing angle from ± 30° to ± 90° without producing virtual images.

再帰透過による空中映像における広視野角実現のための直交ミラーアレイの分割配置

We proposed divided-type dihedral corner reflector array (DCRA) in order to display floating image with wide viewing angle. DCRA is a kind of optical device which can display floating image of real object by retrotransmission. The viewing angle of the floating image is, however, narrow, because the angle of incident ray which can be retrotransmission is limited. Therefore, we expand a range of viewing angle by dividing and combining DCRA to use the region in which the ray can be retrotransmission. In this paper, we evaluated the viewing angle of our divided DCRA by analyzing angular distribution of retrotransmissive ratio. As a result, we showed that the divided DCRA can be expanded the viewing angle of floating image to 180 deg.

UAVSAR Polarimetric Calibration

Uninhabited aerial vehicle synthetic aperture radar (UAVSAR) is a reconfigurable polarimetric L-band SAR that operates in quad-polarization mode and is specifically designed to acquire airborne repeat-track SAR data for interferometric measurements. In this paper, we present details of the UAVSAR radar performance, the radiometric calibration, and the polarimetric calibration. For the radiometric calibration, we employ an array of trihedral corner reflectors, as well as distributed targets. We show that UAVSAR is a well-calibrated SAR system for polarimetric applications, with absolute radiometric calibration bias better than 1 dB, residual root-mean-square (RMS) errors of ~0.7 dB, and RMS phase errors ~5.3°. For the polarimetric calibration, we have evaluated the methods of Quegan and Ainsworth et al. for crosstalk calibration and find that the method of Quegan gives crosstalk estimates that depend on target type, whereas the method of Ainsworth et al. gives more stable crosstalk estimates. We find that both methods estimate leakage of the copolarizations into the cross-polarizations to be on the order of -30 dB.

Fabrication of a Dihedral Corner Reflector Array for a Floating Image Manufactured by X-ray Lithography Using Synchrotron Radiation

Fabrication of a Dihedral Corner Reflector Array for a Floating Image Manufactured by X-ray Lithography Using Synchrotron Radiation

MOONLIGHT: A NEW LUNAR LASER RANGING RETROREFLECTOR INSTRUMENT

Since 1969 Lunar Laser Ranging (LLR) to the Apollo Cube Corner Reflector (CCR) arrays has supplied several significant tests of gravity: Geodetic Precession, the Strong and Weak Equivalence Principle (SEP, WEP), the Parametrized Post Newtonian (PPN) parameter , the time change of the Gravitational constant (G), 1/r 2 deviations and new gravitational theories beyond General Relativity (GR), like the unified braneworld theory (G. Dvali et al., 2003). Now a new generation of LLR can do better using evolved laser retroreflectors, developed from tight collaboration between my institution, INFN–LNF (Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali di Frascati), and Douglas Currie (University of Maryland, USA), one of the fathers of LLR. The new lunar CCR is developing and characterizing at the “Satellite/Lunar laser ranging Characterization Facility” (SCF), in Frascati, performing our new industry standard space test procedure, the “SCF-Test”; this work contains the experimental results of the SCF-Test applied to the new lunar CCR, and all the new payload developments, including the future SCF tests. The International Lunar Network (ILN) research project considers our new retroreflector as one of the possible “Core Instruments”

MOONLIGHT: A NEW LUNAR LASER RANGING RETROREFLECTOR INSTRUMENT

Since 1969 Lunar Laser Ranging (LLR) to the Apollo Cube Corner Reflector (CCR) arrays has supplied several significant tests of gravity: Geodetic Precession, the Strong and Weak Equivalence Principle (SEP, WEP), the Parametrized Post Newtonian (PPN) parameter , the time change of the Gravitational constant (G), 1/r<sup>2</sup> deviations and new gravitational theories beyond General Relativity (GR), like the unified braneworld theory (G. Dvali et al., 2003). Now a new generation of LLR can do better using evolved laser retroreflectors, developed from tight collaboration between my institution, INFN–LNF (Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali di Frascati), and Douglas Currie (University of Maryland, USA), one of the fathers of LLR. The new lunar CCR is developing and characterizing at the “Satellite/Lunar laser ranging Characterization Facility” (SCF), in Frascati, performing our new industry standard space test procedure, the “SCF-Test”; this work contains the experimental results of the SCF-Test applied to the new lunar CCR, and all the new payload developments, including the future SCF tests. The International Lunar Network (ILN) research project considers our new retroreflector as one of the possible “Core Instruments”

Volumetric display using rotating prism sheets arranged in a symmetrical configuration

A volumetric display that creates a distortion-free three-dimensional (3D) image in midair is described. The proposed system consists of rotating prism sheets used as an optical scanner and a dihedral corner reflector array (DCRA), which is a distortion-free imaging element. Two prism sheets are arranged in a symmetrical configuration to reduce an unnatural motion parallax caused by optical aberrations. A cross-section of the 3D image is formed by the DCRA in midair and moved by the rotating prism sheets to create a 3D displayable space. A 3D volume image was displayed without image distortion or unnatural motion parallax.

Floating volumetric image formation using a dihedral corner reflector array device

A volumetric display system using an optical imaging device consisting of numerous dihedral corner reflectors placed perpendicular to the surface of a metal plate is proposed. Image formation by the dihedral corner reflector array (DCRA) is free from distortion and focal length. In the proposed volumetric display system, a two-dimensional real image is moved by a mirror scanner to scan a three-dimensional (3D) space. Cross-sectional images of a 3D object are displayed in accordance with the position of the image plane. A volumetric image is observed as a stack of the cross-sectional images. The use of the DCRA brings compact system configuration and volumetric real image generation with very low distortion. An experimental volumetric display system including a DCRA, a galvanometer mirror, and a digital micro-mirror device was constructed to verify the proposed method. A volumetric image consisting of 1024×768×400 voxels was formed by the experimental system.

Reconfigurable angular diversity antenna with quad corner reflector arrays for 2.4 GHz applications

The authors propose a reconfigurable angular diversity antenna, constructed with quad corner reflector arrays and switching control, that can provide effective polarisation. With switches in the control unit of the base station, a high radiation gain antenna to provide cross-pair polarisations for receiving operations, as well as an omni-directional radiation pattern for transmitting, has been reconfigured. Simulation and measurement results including frequency responses, radiation patterns and three-dimensional polar plots demonstrate the design of an antenna. Diversity measurements with correlation and root mean square (RMS) error vector magnitude (EVM) are presented in order to evaluate the proposed antennas. The angular diversity technique can be applied to wireless local area network (WLAN) and multiple-input and multiple-output (MIMO) systems.

Etched corner reflector array lasers: a detailed study

The effect of the corner reflector size on the performance of an etched corner reflector array laser is studied. Experimental evidence is presented to show that the operation of the corner reflector array laser is governed by the diffraction principle. The light output increases markedly if the reflector size is large enough so that diffraction can be neglected. This general principle should prove useful in the design of unguided photonic integrated circuits.

A corner reflector InGaAs-GaAs strained layer single quantum well coupled laser array

An InGaAs-GaAs-AlGaAs strained layer single quantum laser array with a reactive ion etched corner reflector array as its rear facet has been fabricated. The corner reflectors play a two-fold role as a highly reflective rear mirror and as a phase-locking coupler. Phase locked operation with beam widths as low as 0.64/spl deg/ are obtained at pumping currents up to 4/spl times/I/sub th/ and output powers up to 60 mW. The coupling mechanism and the benefit of the corner reflector to output performance are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Preliminary analysis of ERS-1 SAR for forest ecosystem studies

The authors examine an image obtained by the C-band VV-polarized ERS-1 SAR with respect to potential land applications. A scene obtained near noon on Aug. 15, 1991, along the US-Canadian border near Sault Ste. Marie is calibrated relative to an array of trihedral corner reflectors and active radar calibrators distributed across the swath. Extensive contemporaneous ground observations of forest stands are used to predict sigma degrees at the time of the SAR overpass using a first-order vector radiative transfer model (MIMICS). These predictions generally agree with the calibrated ERS-1 data to within 1 dB. It is demonstrated that the dynamic range of sigma degrees is sufficient to perform limited discrimination of various forest and grassland communities even for a single-date observation. Furthermore, it is demonstrated that retrieval of near-surface soil moisture is feasible for grass-covered soils when plant biomass is less than 1 tonne/ha. >

SIR-B image calibration by a corner reflector array

Abstract SIR-B image data taken over a corner reflector array are analysed to calibrate the image and to estimate the 3dB resolution. Square trihedral corner reflectors having different radar cross-sections (RCSs) are successfully used to relate an image data number to RCS. RCS of the background surface is estimated and its effect is also included in the above relation. The 3dB resolutions are estimated by two independent techniques. The results obtained from the two techniques agree with each other within their relative difference by 5·6 per cent except for one case. The estimated resolutions are larger than those predicted by the Jet Propulsion Laboratory. The estimates should be regarded as the image resolutions and do not represent the sensor characteristics.

On the use of multiple antenna arrays and corner reflector assemblies in radio positioning applications

Modern radio positioning systems often use multiple-antenna arrays or corner reflector arrays in order to increase the system range. A theoretical investigation of the movement of the antenna phase center on these arrays is carried out, and the resulting distance error is presented for several array configurations.

The Corner Reflector

In July of 1969. the Apollo astronauts placed an array of corner reflectors on the moon. The array was used to reflect an earth-originating pulsed laser beam back to earth. The total travel time of a pulse (about 2.5 seconds) yielded a more accurate determination (to within 6 inches) of the distance from the earth to the moon (approximate mean value, 239000 miles).

Enhancement of Radar Imagery by Maximum Entropy Processing

The maximum entropy spectrum (MES), a sampled data power spectrum estimator, is applied to the enhancement of imagery obtained by synthetic array radar (SAR) imaging systems. MES offers better frequency resolution than conventional Fourier transform methods for certain signal classes. Since azimuth ground resolution in SAR systems is obtained by doppler frequency measurement of the radar return, the method is capable of enhancing the resolution of SAR maps. The principal signal requirement is adequate signal-to-noise ratio. The maximum entropy method has been tested using data obtained by the Hughes FLAMR radar system. The super-resolution capabilities of the method are demonstrated using FLAMR images of corner reflector arrays.

Unidirectional antennas for 450 to 460 mc

The 450- to 460-mc emergency communications band is, in a sense, between vhf and microwaves as far as unidirectional antennas are concerned; therefore, antennas commonly used for both applications are practical possibilities for this band. It is the purpose of this paper to summarize the characteristics of several types of antennas that might be used for this application. While there are many types of unidirectional antennas, three stand out as presenting the best possibilities from a practical standpoint. They are the corner reflector, the Yagi or parasitic array, and the parabolic.