The imaging properties of scattering particles in laser beams

The scattering properties of spherical particles crossing a laser beam devi ate from the Lorenz-Mie solution for particles both smaller and larger than the beam dimensions. For smaller particles the local beam properties at th e position of the particle can be used in the Lorenz-Mie calculations, wher eas for larger particles the varying beam properties over the surface of th e particle must be accounted for. The Fourier Lorenz-Mie theory and the ext ended geometrical optics theory offer two methods for analysing such situat ions. These two methods are used to investigate the scattering fields of va rious scattering particles and to demonstrate the agreement of the results. The results are useful for understanding the signal origins in laser-Doppl er and phase-Doppler techniques, especially the 'trajectory effect' or 'Gau ssian beam effect'.