Polychromatic target identification with a color liquid-crystal-TV-based joint-transform correlator

A real-time polychromatic target-detection technique that uses a computer-addressable color liquid-crystal- TV-based joint-transform correlator (JTC) is presented. One of the major features of the polychromatic JTC is that the spectra content of the object can be exploited. Since the liquid-crystal-TV panel is computer addressable, the JTC system can be made adaptive, by which the joint-transform power spectrum can be manipulated. Experimental demonstration of the proposed polychromatic JTC is provided, in which we show that the spatial and the spectral content of targets can be detected.     

Thermal images generated by a line-scanning technique: statistical properties

The analysis of statistical parameters of computer-generated therfial images by a line-scanning technique indicates an approach to efficient image transmission.     

Planar waveguide refractive index distribution functions determined precisely from mode indices

The inverse WKB (IWKB) approximation has been extended to derive the index distribution functions from the measured mode indices of a planar waveguide. Through the use of this technique, the forms of the index distribution functions are obtained by IWKB approximation and a criterion is used to derive the functions accurately. The results are compared to the exponential and Fermi distributions. It is shown that the index profile, surface index, and waveguide depth can be obtained more accurately than with the original IWKB approximation. Finally, the index distribution function of a c-cut proton-exchanged LiTaO(3) waveguide is given by this technique, the mode indices calculated with this function agree with the experimental results in the range of 10(-4).     

Structural properties of precipitates formed by hydrolysis of Fe3+ ions in Fe2(SO4)3 solutions

The structural properties of the solid phase, formed by the hydrolysis of Fe³⁺ ions in Fe₂(SO₄)₃ solutions at 90 or 120 °C, were investigated using X-ray diffraction,⁵⁷Fe Mössbauer spectroscopy, Fourier transform-infrared spectroscopy (FT—IR) and transmission electron microscopy. The concentration regions of Fe₂(SO₄)₃ were determined for the precipitation of goethite, -FeOOH, or hydronium jarosite, H₃OFe₃(OH)₆(SO₄)₂ as a single phase. Superparamagnetic behaviour of -FeOOH particles was observed. Hydrolysis of Fe³⁺ ions in 0.1 M Fe₂(SO₄)₃ solutions at 120 °C produced H₃OFe₃(OH)₆(SO₄)₂ and basic sulphate, Fe₄(OH)₁₀SO₄. The interpretation of⁵⁷Fe Mössbauer and FT—IR spectra is given.     

Investigation of the characteristics of thermionic converters with a Mo (110) single-crystal collector with Ion-implanted oxygen

Institute of Nuclear Reactors, Russian Scientific Center "Kurchatovskii Institut." Translated from Atomnaya énergiya, Vol. 76, No. 2, pp. 151–152, February, 1994.     

Effect of external index of refraction on multimode fiber couplers

The dependence of the performance of fused-taper multimode fiber couplers on the refractive index of the material surrounding the taper region has been investigated both theoretically and experimentally. It has been identified that for a 2 × 2 multimode fiber coupler there is a range of output-power-coupling ratios for which the effect of the external refractive index is negligible. When the coupler is tapered beyond this region, the performance becomes dependent on the external index of refraction and lossy. To analyze the multimode coupler-loss mechanism, we develop a two-dimensional ray-optics model that incorporates trapped cladding-mode loss and core-mode loss through frustrated total internal reflection.

Computer-simulation results support the experimental observations. Related issues such as coupler fabrication and packaging are also discussed.

     

Effect of molecular anisotropy on backscattered ultraviolet radiance

The effect of molecular anisotropy on backscattered UV (BUV) radiances is computed by accounting for it in both Rayleigh optical thickness and the scattering-phase matrix. If the effect of molecular anisotropy is included only in the optical thickness and not in the phase matrix, then for high sun (θ(0) ～ 0°), the nadir radiance (I(0)) leaving the top of the atmosphere is approximately 1.8% higher than the radiance (I(op)) computed with the effect included in the phase matrix. For very low sun (θ(0) > 80°), I(0) is approximately 2.3% lower than I(op). For off-nadir radiances the relative increase (decrease) depends on both the local zenith angle as well as the azimuth angle. Also, an increase in the surface reflectivity decreases the effect of molecular anisotropy on the upwelling radiances. Exclusion of the anisotropy factor in the Rayleigh-phase matrix has very little effect (<1%) on ozone retrieval from the BUV-type instruments. This is because of the ratio technique used in the retrieval algorithm, which practically cancels out the anisotropy effect.