Theoretical Model for the Image Formed by a Spherical Particle in a Coherent Imaging System: Comparison to Experiment.

摘要

A simple theoretical model is presented that allows calculation of the image produced by a spherical absorbing particle illuminated by monochromatic, coherent laser light. Results presented in this reprint are restricted to single-lens imaging system configurations. The method uses classic Lorenz-Mie scattering theory to obtain the electromagnetic field external to an absorbing spherical particle and a Fourier optics approach to calculate the intensities in the image plane. Experimental results evaluating focus characteristics are examined for 50 micrometer diameter water droplets using an N2 laser imaging system in conjunction with a digital image processor, and the experimental images are compared to the results of the theoretical mode. Comparative focus criteria results are particularly useful in aerosol science research involving dynamic particles size measurements in which criteria for focus and depth of field must be established. Keywords: Spray analysis; Image formation; Focus effects. (JHD)