A CCD based approach to high-precision size and refractive index determination of levitated microdroplets using Fraunhofer diffraction
- Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6142 (United States)
We describe a fast and convenient method of high precision size and refractive index determination of electrodynamically levitated microdroplets using Fraunhofer diffraction. The diffraction data were obtained with a 16-bit, unintensified charge coupled device (CCD) camera, and converted into angle-resolved elastic scattering intensity patterns by means of a carefully determined set of transformation parameters. The angular scattering patterns were analyzed without any {ital a priori} estimate of the droplet size and only a nominal estimate ({approx}2{percent}) of the refractive index. Experimental angular scattering patterns were fit to calculated patterns from Mie theory using a graded step-size and scaling algorithm and optimized with respect to both droplet diameter and refractive index (real part only) with a precision of {le}3 parts in 10{sup 4} and 1 part in 10{sup 3}, respectively. Potential application to quantitative fluorescence and Raman spectroscopy, as well as mixture analysis in microdroplets is discussed. {copyright} {ital 1997 American Institute of Physics.}
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 509121
- Journal Information:
- Review of Scientific Instruments, Vol. 68, Issue 6; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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