Forward scattering measurement device with a high angular resolution.

A new optical device to measure forward scattered light in a range of 3 degrees to 20 degrees has been developed and tested. The scattered light is focused on a plane where its axial position is proportional to the scattered angle theta. A motorized iris diaphragm located at this plane selects the scattered light between 0 degrees and a variable angle theta. This light is collected by an integrating sphere and converted into an electrical signal by an APD. The device was tested with suspensions of polystyrene microspheres of 3 different sizes. The obtained results are in good agreement with the Mie theory.