The effect of vignetting on the measured angular light energy distribution in a particle size distribution measuring system is studied theoretically and experimentally. A series of correction charts are produced that allow the vignetted light energy distribution from a homogeneous particle field to be corrected, depending on the position and extent of the particle field with respect to the collection lens. This phenomenon is of great importance in the measure-ment of particle size distribution of systems where (1) the particle field cannot be within the focal length of the collection lens owing to difficulty in optical access, (2) the particle field extent is larger than the required collection lens focal length, or (3) an extended beam path is desirable owing to low concentration of the particles in the field.
A. A. Hamidi,
"Vignetting In Forward Light Scattering Particle Size Distribution Measurement Techniques," Optical Engineering 25(12), 251294 (1 December 1986). https://doi.org/10.1117/12.7974001