Abstract: A refinement of the Fourier transform fringe-pattern analysis technique which uses a 2-D Fourier transform is described. The 2-D transform permits better separation of the desired information components from unwanted components than a 1-D transform. The accuracy of the technique when applied to real data recorded by a system with a nonlinear response function is investigated. This leads to simple techniques for optimizing an interferogram for analysis by these Fourier transform methods and to an estimate of the error in the retrieved fringe shifts. This estimate is tested on simulated data and found to be reliable.

Abstract: A theoretical modeling is proposed to predict the efficiency factors for attenuation, total scattering, and backscattering for spherical and homogeneous phytoplanktonic cells in suspension. The input parameters of this modeling are the actual size distribution, the spectral values of absorption by the living cells, and an adjustable value of the real part of the refractive index. The variations in these parameters lead to very diverse spectral behavior of the efficiency factors. Theoretical predictions are compared to experimental results for some species to evaluate the reliability of the model for algal cells of various indices and morphologies.

Abstract: Symbolic substitution logic is based on optical pattern transformations This space-invariant mechanism is shown to be capable of supporting space-variant operations An optical implementation is proposed It is based on splitting an image, shifting the split images, superimposing the results, regenerating the superimposed image with an optical logic array, splitting the regenerated image, shifting the resulting images, and superimposing the shifted images Experimental results are presented Examples demonstrate how symbolic substitution logic can be used to implement Boolean logic, binary arithmetic, cellular logic, and Turing machines

Abstract: We examine the photon correlation and other vital performance characteristics of silicon avalanche photodiodes operated in photon counting or the Geiger mode, and assess their suitability as detectors for photon correlation spectroscopy and laser velocimetry measurements.

Abstract: Setting the scene Fournier theory deconvolution phase recovery reconstruction from projections Specke imaging and interferometry image processing system design program categories technical practicalities

Abstract: It is commonly observed that natural multiple-scattering media such as sand and soils become noticeably darker when wet. The primary reason for this is that changing the medium surrounding the particles from air to water decreases their relative refractive index, hence increases the average degree of forwardness of scattering as determined by the asymmetry parameter (mean cosine of the scattering angle). As a consequence, incident photons have to be scattered more times before reemerging from the medium and are, therefore, exposed to a greater probability of being absorbed. A simple theory incorporating this idea yields results that are in reasonable agreement with the few measurements available in the literature, although there are differences. Our measurements of the reflectance of sand wetted with various liquids are in reasonably good agreement with the simple theory. We suggest that the difference between reflectances of wet and dry surfaces may have implications for remote sensing.

Abstract: Using rigorous coupled-wave analysis, high spatial-frequency rectangular-groove surface-relief phase gratings are shown to be capable of exhibiting zero reflectivity. Thus these corrugated surfaces may act as antireflection coatings in a variety of applications. The diffraction characteristics of rectangular-groove surface-relief gratings are presented for several ratios of incident wavelength to grating period as a function of filling factor, groove depth, angle of incidence, and polarization. The conditions for zero reflectivity are identified. Results are compared with single-homogeneous-layer approximate theory results. In the limit of long wavelengths for an electromagnetic wave in a dielectric of refractive index n1 normally incident on a dielectric of index n2, it is determined that for antireflection behavior, the grating groove depth should be λ/4(n1n2)1/2 and the filling factor should be n1/(n1 + n2) or n2/(n1 + n2) for the electric field perpendicular or parallel to the grating vector, respectively. The spectral and angular responses of these gratings are like those of single-homogeneous-layer antireflection coatings. These gratings also exhibit birefringent retardation.

Abstract: Advanced filters are described for distortion-invariant space-invariant object identification and location in clutter using correlators. These correlation synthetic discriminant functions (SDFs) are extensions of earlier projection SDFs. They provide control of the sidelobe levels and the shape of the output correlation function as well as its peak intensity. The theory for synthesis of three such SDFs and a discussion of correlation plane detection criteria for use with these filters are presented.

Abstract: J. M. Cariou, J. Dugas, L. Martin, and P. Michel Laboratoire de Physique des Solides, Associé au CNRS, Université Paul Sabatier, 31062 Toulouse CEDEX, France. Received 30 July 1985. 0003-6935/86/030334-03$02.00/0. © 1986 Optical Society of America. For polymers, the thermal volume expansion coefficient is always much higher than the coefficient for inorganic materials. We have recently shown that the variation of the refractive index of polymers vs temperature is essentially due to the variation of density. From the Lorentz-Lorenz relation, the function (n + 2)/(n 1) appears perfectly linear in the various temperature ranges where no phase transition occurs. The slope of the representative curve exactly follows the thermal expansion coefficient α which keeps a constant value in each temperature range. Thus, α may be easily deduced from the refractive-index measure­ ment at various temperatures. At the same time, the tem­ peratures where discontinuities of (n + 2)/(n 1 ) or its derivative appear conveniently fit with the transition tem­ peratures which may be so determined. A correct observation of such behavior is that the tempera­ ture variations are so slow that the material is continuously kept in thermal equilibrium. Indeed, it is well known that the various molecular processes which induce the transitions are characterized by very large relaxation times. If the material undergoes temperature changes too fast, it remains in a metastable state which is not a true equilibrium state. Waxier et al. have interferometrically measured some optical properties of Plexiglas and Lexan and determined the evolution of dn/dt, with the temperature between -160°C and +60°C. They obtained irregular but continu­ ous curves which do not evidence, even in a crude way, any systematic change in their behavior which may be related to a phase transition. Nevertheless, in the temperature range studied, at about -30°C PMMA (Plexiglas) undergoes the so-called β transition which is attributed to the beginning of the rotation of lateral chains of methacrylate radicals. A relevant discontinuity of the coefficient of thermal expan­ sion has been observed for PMMAs various tacticities. In the same way, for polycarbonate, the glass transition at 125°C is out of the temperature range studied by these authors. However a so-called α peak was observed at ~60°C and was widely discussed by Neki and Geil. No noticeable anomaly appears in the Waxier results. We have measured the refractive index of commercial samples of PMMA (Altuglas) and polycarbonate (Lexan) between about -100°C and +150°C. To avoid any stress which could take place by contact with another material, the measurement method chosen was the minimum deviation of a prism. The PMMA prism was drawn from bulk material

Abstract: Laboratory measurements of the absorption coefficient and refractive index of solid CO2 are reviewed for all parts of the electromagnetic spectrum from the ultraviolet to the microwave with emphasis on values for temperatures above 77 K The available measurements in some cases require reinterpretation A compilation of the spectral absorption coefficient kabs is made for 52-nm to 160-nm wavelength (with some gaps because of lack of data), and the complex refractive index is then computed by Kramers-Kronig analysis The uncertainty in imaginary refractive index is discussed; it varies greatly with wavelength The real part of the refractive index is close to 14 for all parts of the spectrum except near strong absorption bands and is accurate to ±005 outside those bands No measurements of absorption are available for 180–330-nm, 10–25-μm, and 25-μm–25-mm wavelength, except in the strong narrow absorption lines Remeasurement of kabs is also needed for parts of the IR spectrum between 25 and 25 μm because of experimental error in the available measurements

Abstract: Relying on van de Hulst’s localization principle, a localized approximation to the generalized Lorenz-Mie theory is introduced. The validation of this simple approximation is obtained from numerical comparisons the Rayleigh-Gans theory. Other comparisons concerning scattering profiles are carried out first with theoretical data published in the literature and later with experimental measurements. Original results are given for coal particles as an example of the versatility of the method.

Abstract: Using the extended boundary condition method, scattering calculations from randomly oriented rotationally symmetric nonspherical particles were made, the size parameters (1-25) and the refractive indicies (1.5 0.02i) of which were chosen to relate to the transfer of solar and IR radiation in an aerosol atmosphere. Comparison of computations for 23 Chebyshev shapes to corresponding size-averaged spherical results revealed that nonsphericity increased absorption for size parameters larger than around 10 and decreased the asymmetry factor, and correspondingly increased the backscattered fraction, in the size ranges 8-15. The scattering efficiency was somewhat larger for nonspherical particles, while the single-scattering albedo tended to be smaller, and concavity was shown to almost always enhance spherical-nonspherical differences.

Abstract: A novel technique for the generation of single-pulse rotational CARS spectra is presented and demonstrated flows and flames. The technique is based on a multiple four-color interaction, where the rotational in gas with two photons of different frequencies from a broadband dye laser, and by coupling to a energies are excited photon from a frequency-doubled Nd:YAG laser a rotational CARS photon is created. An interesting third feature of the technique is the possibility of simultaneously generating both a rotational and vibrational using a double-folded BOXCARS arrangement. This technique is demonstrated on N2 CARS spectrum molecules.

Abstract: A new optical–digital computing system called OPALS (optical parallel array logic system) is presented. OPALS can execute various parallel neighborhood operations such as cellular logic as well as parallel logical operations for 2-D sampled objects. The system has the ability to perform iterative operations. OPALS is systemized, centering on the optical logic method using image coding and optical correlation techniques. The concept of array logic plays an important role in designing the OPALS, and new optical techniques for constructing the OPALS are proposed. Using these techniques, a pure optical version of the OPALS can be made.

Abstract: We have designed and tested a compact injection seeding system consisting of a diode-laser-pumped Nd:YAG master oscillator and a permanent-magnet Faraday isolator. With active resonator frequency stabilization, this system permits highly reliable single-axial-mode operation of a Q-switched Nd:YAG laser over a period of hours. The system is capable of injection seeding both stable and unstable resonator designs and is suitable for injection seeding commercial lasers with only minor modifications.

Abstract: The drift of an optical fiber gyroscope caused by the earth's magnetic field through the Faraday effect is studied theoretically in a simple model and also in a practical model. The mechanism of its reduction using polarization-maintaining optical fiber is clarified; it depends on the twist and the birefringence of the fiber. The presence of the twist component whose period is just equal to one turn of the sensing fiber loop causes the drift; ways of suppressing it are described. Influence of the practical parameters, such as imperfection of the polarizer, is also discussed.

Abstract: La television a cristal liquide est utilisee comme modulateur spatial dans un correlateur optique

Abstract: The absorption coefficient and index of refraction have been measured in the 2–30-cm−1 frequency range for the following materials at a temperature near 5 K: Pyrex, Fluorogold, Eccosorb CR110, Stycast 2850 FT, Plexiglas, TPX, Neoprene, Teflon, and Nylon. For some of these materials room temperature measurements were also made.

Abstract: Photon noise in photometric instruments is computed using two different methods. A first expression, derived from quantum physics, corresponds to the most widely used formulas and is applicable when diffraction phenomena are negligible. The second one is derived from the semiclassical approach of Hanbury Brown and Twiss. Properties of this expression, including consistency with the former one, asymptotical behavior, and scale properties are derived and discussed. The effect of polarization is studied, and practical examples are given.

Abstract: The design of an optical logic parallel processor is described. The central component is a Fabry-Perot cavity, filled with a nonlinear layer and a linear anisotropic layer, such as a sheet of mica. The two logic states are represented by two orthogonal states of the polarization of the light beam. Polarization logic, compared with on/off logic (bright or dark), requires less power, generates less heat, and is better suited for cascading.

Abstract: A new algorithm is described for numerical inversion of the equations Texp = T(n,k) and Rexp = R(n,k), where Texp and Rexp are measured normal-incidence transmission and reflection of a thin film on a thick substrate, and n + ik is the complex index of refraction of the thin film. The procedure simultaneously provides all pairs (n,k) consistent with the values of (T,R) measured at a specific wavelength and known film thickness. It requires no initial estimates for n and k.

Abstract: This paper describes recent measurements using coherent Doppler lidars operating at a wavelength of 10.6 microns aboard the NASA Ames Convair 990. The purpose of the measurements was to obtain data on the atmospheric wind fields and the distribution of the backscatter coefficient at 10.6 microns. A decription of the instruments is provided detailing the modifications incorporated following the 1981 test flights of the systems. The measurement program is outlined, and preliminary results are discussed.

Abstract: A comparison is made of four prominent Doppler lidar systems, ranging in wavelength from the near UV to the middle IR, which are presently being studied for their potential in an earth-orbiting global tropospheric wind field measurement application. The comparison is restricted to relative photon efficiencies, i.e., the required number of transmitted photons per pulse is calculated for each system for midtropospheric velocity estimate uncertainties ranging from + or - 1 to + or - 4 m/s. The results are converted to laser transmitter pulse energy and power requirements. The analysis indicates that a coherent CO2 Doppler lidar operating at 9.11-micron wavelength is the most efficient.

Abstract: A new method is proposed for the calibration of the sunphotometer. Well-known difficulties of the usual Langley-plot method when applied to unsteady turbidity conditions can be avoided by monitoring the circumsolar radiation. To realize this idea, an alternate of the Langley-plot method is developed, in which the logarithm of the sunphotometer reading is plotted against the ratio of intensity of singly scattered circumsolar radiation to that of direct solar radiation instead of the optical air mass in the usual Langley-plot method. Results of numerical simulations and field tests with a newly developed instrument show that the rms error of the calibration constant could be reduced to 1/5–1/10 of the usual method for wavelengths larger than 500 nm.

Abstract: High accuracy optical processors based on the algorithm of digital multiplication by analog convolution (DMAC) are studied for ultimate performance limitations. Variations of optical processors that perform high accuracy vector-vector inner products are studied in abstract and with specific examples. It is concluded that the use of linear analog optical processors in performing digital computations with DMAC leads to impractical requirements for the accuracy of analog optical systems and the complexity of postprocessing electronics.