Beam Expander Laser Particle Size Distribution Test System

The research of this thesis is based on the project "device for detection and alarm of ultra-high concentrate dust" that is supported by Jiangsu laser institute. The on-line detection technique for the particles distribution in radius without laser beam expansion is investigated in theory and experiment.A method for detecting the collective particles distribution in intensity by optical diffraction technique without laser beam expansion is first proposed. For the collective particles, the time-integration is proved equivalent in theory to the space- integration in the angular distribution of scattering optical energy. The conventional system for particles detection based on fore-scattering principle is simplified and some practical problems, such as the stray light induced by beam expansion and the volume increase, are resolved. In this way, the signal-to-noise ratio of this detection system is greatly increased and the corresponding volume is reduced. The stability of the whole system is enhanced. Due to the available particle detectors that can only measure wet dust, a novel dust generator is designed, which can be applied for dry dust detection on line. With the development of computers and CCD technique, the high-sensitive CCD surface has substituted the conventional photoelectric circle surface as the photoelectric detector, which leads to the distinct increase in both accuracy and speed. Besides, how to eliminate the main light influence and determine the center of recorded images are also studied in detail.