| 摘要 |
PURPOSE:To remove measuring errors generated by the thermal effect of a photosensitive element due to the convergence of transmitted light by providing light receiving means for a laser beam behind a small through-hole formed in the central portion of a detector and obtaining the particle size distribution of a sample particle group from the result of a light reception by said means and a received light intensity distribution on the detector. CONSTITUTION:A laser beam directed to a particle group W to be measured in a dispersed and flying condition is converged on a detector 2 comprised of a plurality of photosensitive elements arranged on the focal plane of a lens 1 disposed behind the particle group W and a received light intensity in the radial direction of the detector 2 is obtained. A transmitted light intensity measuring detector 3 is provided in a position behind a small through-hole 2a formed in the central portion of the detector 2 and a predetermined distance apart therefrom. The laser beam that has passed the small through-hole 2a is again diffused on the light receiving surface of the detector 3 and the energy per unit area of the laser beam has been weakened, the detector being difficult to be thermally affected, resulting in no measuring error. |
