A double-exposure far-field hologram contains particle displacement and velocity information for all particles within a given sample volume. The optical Fourier transform of such a hologram contains a set of fringes which are dependent on the probability density function (pdf) that characterizes the distribution of particle displacements or velocities. It is demonstrated that intensity data measured in the transform plane of a doubly exposed hologram may be processed to yield this pdf for particle motion in one dimension. In the 2-dimensional case, the marginal pdf's may be obtained when the orthogonal components of displacement are independent. Experimental results for 1- and 2-dimensional distributions are presented and good agreement between theory and experiment is observed.

An out-of-focus coherent image of a transilluminated particle in a transparent field is actually an in-line hologram of that particle. In the Fresnel field of the particle's cross-section, direct measurement of the particle diameter can be achieved with considerable effective defocus -- much greater than the depth of focus with an incoherent imaging system.

A method for two-dimensional pattern recognition, applicable to particle shape and size determination, is presented which employs fractal geometric analysis. Fractal contour transformation presents several advantages over spatial harmonic analysis: 1.preservation of translation, rotation, and scale invariance 2.reduced reliance upon high-frequency Fourier transform coefficients 3.improved signal-to-noise ratio of the fractal transform over the Fourier transform for surface feature discrinination. Coordinate transformation is evaluated with respect to its effect upon feature discrimination in polar-mapped multivariable contours. A variety of non-differentiable contours are analyzed. Results are presented in terms of correlation, signal-to-noise ration, and computational load.

A non blocked zero frequency filtering technique is used for improving the holographic recording of small objects. Since the filter is coated on the relay lens, the irradiance distributions in three planes (i.e., in projected images, diffraction patterns and reconstructed images) are calculated. Influences of filter diameter, filter transmittance and exposure level of holograms are considered for discussing the image forms and their contrast.

One of the most difficult optical instrumentation problems in the measurement of aerosol or droplet size distributions is to assure that accurate measurements have been made. Fully reliable standards against which aerosol and droplet measuring instrumentation can be compared and calibrated for in situ measurements do not yet exist. Therefore, it is desirable to compare one set of measurements against other independently made measurements to assure that consistent data are obtained. This work will describe how four independent measurements of particle size can be obtained simultaneously with the particle sizing interferometer (PSI). Examples of results from analytical studies intended to evaluate these techniques are presented. A result of this work has been to show how the PSI can be used as a polar nephelometer. This nephelometer can determine particle size, index of refraction, and a measure of particle symmetry by measuring both scattered intensity and visibility as a function of scatter angle. These PSI nephelometric studies have also found use in identifying appropriate angles where the scattered light collecting optics can be placed to obtain monotonic visibility or scattered intensity response functions to determine particle size.

The study of particulate formation and dynamics of motion in industrial multicomponent systems requires the knowledge of the distribution function of the size of those particulates. Two optical in situ techniques have been studied for on-line characterization of the size distribution in two-phase flows. The pointer beam technique (PB) offers good potential for measurement of particles in the size range of 0.1 < d < 10 pm. Polarization intensity ratio (PIR) is subject to severe oscillations which limit the size regions where it is useful.

The Phase/Doppler method which has proven to be successful in obtaining large particle size and velocity measurements in realistic environments has been extended to measure particles as small as 0.5 micrometer in diameter. Mie theory calculations served to determine the feasibility of obtaining adequate size resolution. Experiments were conducted using 0.54, 0.80, 0.94, 2.0, and 2.88 micrometer polystyrene latex spheres to verify the measurement capability. Although the measured distributions were relatively broad, the modes of the distributions were in good agreement with the specified size. Polydispersions with mean sizes on the order of 1 to 5 micrometers were measured and compared to measurements by other means. These results also were in good agreement.

A Phase Doppler Spray Analyzer (P/DSA) and a laser imaging system (LIS) was used to study the response of a P/DSA to non-spherical particles. Methanol particles with an aspect ratio ranging from 0.7 to 1.4 were used in this investigation. Results indicated that the P/DSA was quite sensitive to particle shape. A Berglund-Liu generator was used to produce particles of 98 um (volumetric diameter). The P/DSA instrument measured particle sizes ranging from 142 μm for a particle of aspect ratio 0.7 to 84 μm for an aspect ratio of 1.4. Particle diameters based on averaged x and y diameters for the laser imaging system ranged from 95 μm to 92 μm over the same range of aspect ratios.

Spatially resolved measurements of droplet size and velocity are desirable to aid in matching fuel injectors to combustor flow fields and to support the development of two phase flow modeling. Interferometric, laser based techniques have been available since the early '70s. Successful application to practical sprays, however, has been hampered by numerous difficulties. In this paper, two interferometric techniques (Visibility/Intensity Validation and Phase Doppler) are critically examined in characterizing the spray of an air-assist nozzle with Sauter mean diameter.c35 microns. The two techniques are compared to each other and are evaluated against a Malvern diffraction unit. With the use of a rotating grating for Visibility/Intensity Validation, the interference techniques compare well to each other and to the diffraction method. The Phase Doppler technique is more easily applied to the spray, due largely to its broadened size and velocity ranges. The consistency of the interferometric results raises questions with regard to the use of the Malvern's most frequently applied distribution model.

A new optical technique for determining the evaporation and condensation rate of flowing liquid droplets is described. The same technique can also be used to detect small shape distortions. The method is based on the precise measurement of resonance peaks in the fluorescence spectrum. These resonances, which are a sensitive function of the size, shape, and index of refraction of dye-impregnated dielectric micro-objects, have been called morphology-dependent resonances.

A software system was developed to fully utilize the features of a commercial high-speed digital image processor. This software system was designed to enable general-purpose image analysis as well as allow for the development of specialized analyses, such as object counting or pattern recognition. Over 60 image processing functions are provided. Almost all functions operate on a 512 x 512 x 8 bit image array in less than one-half of a second. Examples include a 256K byte histogram plotted over the image in 0.34 seconds and a pixel-by-pixel threshold comparison in 100 ms. All of these functions can be called via keyboard commands. In addition, the functions can be used as building blocks in an interpreted command language, thus creating additional specialized functions. A mode has been provided where the most commonly used functions can be invoked by pressing a terminal function key, with the resulting digital image immediately displayed on the monitor; and gray levels, coordinates, etc. presented on the operator's terminal. Although this package was developed with a DEC LSI-11 hosting a Recognition Concepts TRAPIX 55/32 image processor, the concepts can be used on many vision systems.