title: Scattering information obtained by optical microscopy: differential dynamic microscopy and beyond.
abstract: We describe the use of a bright-field microscope for dynamic light scattering experiments on weakly scattering samples. The method is based on collecting a time sequence of microscope images and analyzing them in the Fourier space to extract the characteristic time constants as a function of the scattering wave vector. We derive a theoretical model for microscope imaging that accounts for (a) the three-dimensional nature of the sample, (b) the arbitrary coherence properties of the light source, and (c) the effect of the finite numerical aperture of the microscope objective. The model is tested successfully against experiments performed on a colloidal dispersion of small spheres in water, by means of the recently introduced differential dynamic microscopy technique [R. Cerbino and V. Trappe, Phys. Rev. Lett. 100, 188102 (2008)]. Finally, we extend our model to the class of microscopy techniques that can be described by a linear space-invariant imaging of the density of the scattering centers, which includes, for example, dynamic fluorescence microscopy.
authors.affiliation: Dipartimento di Chimica, Biochimica a Biotecnologie per la Medicina, Università degli Studi di Milano, via Fratelli Cervi 93, Segrate, Milano I-20090, Italy. fabio.giavazzi@unimi.it
authors.forename: Fabio
authors.initials: F
authors.lastname: Giavazzi
authors.forename: Doriano
authors.initials: D
authors.lastname: Brogioli
authors.forename: Veronique
authors.initials: V
authors.lastname: Trappe
authors.forename: Tommaso
authors.initials: T
authors.lastname: Bellini
authors.forename: Roberto
authors.initials: R
authors.lastname: Cerbino
mesh_terms: D005583:Fourier Analysis; D007753:Laboratories; D008853:Microscopy / Q000379:methods*; D008856:Microscopy, Fluorescence; D009038:Motion; D055620:Optical Phenomena; D012542:Scattering, Radiation