Laser diffraction has become a popular technique in many fields for measuri
ng particle size distributions (PSDs). It is not only one of the standard t
echniques for laboratory measurements but is also gaining importance for on
-line process monitoring and process control. This article reports some dev
elopments of this technique while recognizing the potential that still exis
ts. In this report both particle size and shape are taken into account. For
optimum results, both effective sensing and analysis of the diffraction pa
ttern are required. This is the goal of our present study with a special in
terest in on-line application. In this paper, a statistical approach - prin
cipal component analysis (PCA) - to the scattered Light signals from a conv
entional detector array is shown to improve the sensitivity to a few large
particles relative to the main size distribution. For determining particle
shape, a wedge-type photo-detector for sensing the azimuthal Light intensit
y has been applied together with the procedures of cross-correlation, sweep
selection for single particle presence and Fourier analysis. Finally, a no
vel light scattering sensor is presented, which enables the measurement of
both size and shape and which offers even more promising applications for o
n-line process control. (C) 2000 Elsevier Science S.A. All rights reserved.