Contaminant dispersal measurement using laser light sheet illumination and digital image processing techniques.

This paper describes a method for measuring tbe dispersal of airborne contaminants by light-sheet illumination of aerosol tracen and digital image processing techniques. The goals of the research were twofold: to use field-portable and safe equipment to make near-instantaneous measurements of tracer aerosol concentrations over arbitrarily positioned two-dimensional planes of near-mom dimensions; and to carefully define similarity conditions under which aerosol dispersal can be considered an accurate surrogate for passive molecular dispersal. The measurement method involves five procedures: tracer generation by condensation of a glycol vapor; light sheet illumination using a projected laser; image capture using a CCD video camera linked to an analog-to-digital converter; point-calibration measurement, via light attenuation, of aerosol concentration; and image processing using a public-domain microcomputer-based program. This paper will briefly review the method and evaluation tests and will emphasize technical and theoretical issues concerning the relationship between captured images and aerosol concentration and the similarity of tracer to molecular dispersal.