We demonstrate a quantitative optical scatter imaging (OSI) technique, based on Fourier filtering, for detecting alterations in the size of particles with wavelength-scale dimensions. We generate our scatter image by taking the ratio of images collected at high and low numerical aperture in central dark-field microscopy. Such an image spatially encodes the ratio of wide to narrow angle scatter and hence provides a measure of local particle size. We validated OSI on sphere suspensions and live cells. In live cells, OSI revealed biochemically induced morphological changes that were not apparent in unprocessed differential interference contrast images. Unlike high-resolution imaging methods, OSI can provide size information for particles smaller than the camera's spatial resolution.
© 2001 Optical Society of America
(070.6110) Fourier optics and signal processing : Spatial filtering
(110.0180) Imaging systems : Microscopy
(170.1530) Medical optics and biotechnology : Cell analysis
(170.3880) Medical optics and biotechnology : Medical and biological imaging
(290.5850) Scattering : Scattering, particles
Nada N. Boustany, Scot C. Kuo, and Nitish V. Thakor, "Optical scatter imaging: subcellular morphometry in situ with Fourier filtering," Opt. Lett. 26, 1063-1065 (2001)