Optical foreign matter inspection device

Abstract

An optical foreign matter inspection device includes a rotation stage; a laser light source; a sensor that is a charge accumulation type sensor; a detecting circuit; a light emission timing signal generating circuit configured to generate a light emission timing synchronizing signal synchronized with laser emission; a trigger signal generating circuit configured to receive a first signal (a stage encoder signal) indicating a rotation state of a sample, and generate a trigger signal synchronized with the light emission timing synchronizing signal; a number-of-emitted-pulse calculating circuit configured to receive the light emission timing synchronizing signal and the first signal, and calculate the number of pulses in each period corresponding to a position in a radial direction of the sample; and a processing system configured to measure a state of each position on a surface of the sample by using a detection signal and the number of pulses.