H. Sagehorn et al., Characterization of airborne fibers via Fraunhofer theory: Examination of the validity of Fraunhofer theory using the exact scattering theory MMP, PART PART S, 18(2), 2001, pp. 55-63
Owing to the health hazard of respirable airborne fibers, there is great in
terest in detectors able to monitor fibers online. This paper features such
an optical fiber detector which is based on Fraunhofer theory for the esti
mation of fiber size. Because Fraunhofer theory is not an exact theory and
does not take into account the three-dimensional shape of fibers and their
material properties, comparative computations with an exact theory, the mul
tiple multipole method (MMP), a variant of the generalized multipole techni
que, were performed. For small fiber diameters these simulations showed dif
ferences between diffraction patterns calculated via Fraunhofer theory and
scattering patterns computed with MMR The differences were strongly depende
nt on the optical properties of the fiber material.