Small-sized particle flux monitor

PURPOSE: To detect particles in a detecting region with high sensitivity by detecting the scattered light when a converged strong light ray is emitted to the region. CONSTITUTION: A short wavelength light ray 3 from a laser diode is converged by a convergent lens 2, passed through a detecting region near the opening 9 of a cover 10, and collided with a beam stop 7. The lens 2 is regulated at its focal distance so as to converge the ray 3 to the region. The surface of the stop 7 is covered with a material 8 made of an Si piece which absorbs the light and reflects the residual light in a beam stop cavity. The scattered light generated by the collision of the ray 3 with the particles passing the region is captured by a photodiode 4, and the quantity of the particles in the region is obtained from its intensity. Thus, the particles in the region can be detected with high sensitivity. COPYRIGHT: (C)1990,JPO