Particle number measurement method

Abstract

There is provided a particle number measurement method capable of accurately measuring the number of particles generated by a specific factor. When the number of particles is measured by irradiating laser beam 25 into a main exhaust line 16 via a glass window 24, receiving lights (L1 and L2) scattered from particles (P1 and P2) crossing with the laser beam 25 by a photodetector 21, and calculating the number of particles based on the received scattered light, static particles P2 are considered as contaminants attached to the glass window 24 and the number of static particles P2 is subtracted from the measured number of particles within the main exhaust line 16.

Dependencies are inferred from the claim text.