Light Scattering Theory for Bubbles in Water: Inverse Scattering, Coated Bubbles and Statistics

摘要

Light scattering theory was applied to practical problems related to the detection and sizing of bubbles in ocean water. The emphasis of these calculations was on scattering from microbubbles illuminated by a Gaussian beam into angles close to the critical scattering angle (approximately 83 deg). This emphasis is appropriate for applications to an instrument being developed by NORDA. The specific problems include: (a) Computational analysis of the effects of surface films on the optical scattering properties of bubbles in water; (b) Physical optics approximation for the scattering from a coated bubble--explanation of the shift in the coarse structure and polarization effects; (c) Brewster-angle scattering from coated and uncoated bubbles: applications to measurement of film thickness and to the discrimination of bubbles from particles; (d) Detector placement and inversion of scattering data to obtain the bubble size on an event-by-event basis; and (e) Statistical properties of the photodetector voltages and a possible alternative to event-by-event data inversion. The event-by-event inversion procedure for obtaining the size of each bubble is discussed in an Appendix. Keywords: light scattering; mie theory; inverse scattering. (Author)