The sizing of fibres using optical scattering.

The light scattering pattern from absorbing cylinders has been shown to be adequately described by Fraunhofer diffraction for cylinders with diameters as small as 4 micrometers for light of wavelength 632.8 nm. A simple inversion procedure based on a Fourier transform of the scattering pattern may be used to obtain the size distribution of fibre widths. For fibres of diameter less than 4 micrometers the same inversion procedure may be used when an electron micrograph of the fibres becomes the scattering object. The size distribution for aligned and unaligned fibres may be obtained directly, and no initial calibration is required.