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A novel version of the dark-field optical microscopy for optically-thin specimens, termed optical scatter imaging (OSI) permitted to characterize components of a specimen with sizes smaller than the resolution of the camera that is coupled with the optical microscope. It also enabled observing morphological changes in the specimen that are difficult to discern with the conventional optical microscopy. That technique was based on analog spatial filtering of light scattered by the specimen, a form of analog Fourier filtering.
Alexandrov et al (2005) described an improvement to that microscopic imaging technique, that they call digital Fourier microscopy (DFM). This improvement relies on digital recording of a hologram of a thin specimen formed by interference of light scattered by that specimen and a that emitted by a reference point source both converted to collimated light by a lens with a focal plane positioned in the specimen-reference plane.
The hologram is processed digitally with a Fourier filter formulated to enhance images of components of the specimen with desired light scattering properties, for example, the angular scattering pattern, while attenuating images of other specimen components. As the scattering pattern depends on a specimen component (particle) size, refractive index, shape, structure, and orientation, this opens a range of possibilities in flexible characterization of the specimen components (see also DFM improved) without having to modify the optomechanical setup of the instrument.
| CITATION: Jonasz M. 2006. OSI enhanced: Digital Fourier Microscopy (DFM) (www.tpdsci.com/Tpc/OSIDFM1.php). In: Top. Part. Disp. Sci. (www.tpdsci.com). |
HISTORY: Published: 12-Jan-2006 Modified: 21-Jun-2006 Peer-reviewed: PENDING |
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