For detecting particles with a diameter of less than 100 nm, it is necessary to measure the backward scattered light (scattering angle greater than 90°).

For this purpose the detectors were positioned close to the measuring cell in the ANALYSETTE 22 NanoTec. A semiconductor laser with green light that is also used for measuring forward scattering is used as a light source. Particular attention was placed in the design of the backward scattering detectors on the suppression of undesirable signal components, caused, for example, by reflexes on the measuring cell glasses.