To provide a device and method capable of measuring a particle diameter distribution and a concentration distribution of particles even when a particle diameter is large.
In a particle diameter measuring device using a laser diffraction method, spatial resolution of interference fringe measurement is enhanced by using a CCD element 6a as a detector for acquiring an interference fringe, and an interference fringe in a dynamic range of the CCD element 6a can be measured by providing a 0-order diffracted light shielding plate 5 between a Fourier transform lens 3 and the CCD element 6a. By providing an ND filter 4 decaying laser beam intensity between the Fourier transform lens 3 and the 0-order diffracted light shielding plate 5, interference between a CCD element 7 face and its protective film is eliminated.
MIHASHI HIDEO
OKAWA KATSUHISA
