Open AccessSpatial filtering technique to image and measure two-dimensional near-forward scattering from single particles
Author(s) -
Matthew J. Berg,
Steven C. Hill,
Gorden Videen,
Kristan P. Gurton
Publication year - 2010
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.18.009486
Subject(s) - optics , refractive index , scattering , mie scattering , light scattering , forward scatter , spatial filter , particle (ecology) , spheres , measure (data warehouse) , optical instrument , optical tweezers , materials science , spatial frequency , physics , oceanography , astronomy , database , computer science , geology
This work describes the design and use of an optical apparatus to measure the far-field elastic light-scattering pattern for a single particle over two angular-dimensions. A spatial filter composed of a mirror with a small through-hole is used to enable collection of the pattern uncommonly close to the forward direction; to within tenths of a degree. Minor modifications of the design allow for the simultaneous measurement of a particle's image along with its two-dimensional scattering pattern. Example measurements are presented involving single micrometer-sized glass spherical particles confined in an electrodynamic trap and a dilute suspension of polystyrene latex particles in water. A small forward-angle technique, called Guinier analysis, is used to determine a particle-size estimate directly from the measured pattern without a priori knowledge of the particle refractive index. Comparison of these size estimates to those obtained by fitting the measurements to Mie theory reveals relative errors low as 2%.