Optical foreign matter inspection device

An optical foreign matter inspection device for inspecting a foreign matter on a surface of a sample, comprising:

• a rotation stage allowing the sample to be placed thereon and configured to be rotationally driven, the rotation stage generating a first signal indicating or capable of specifying a rotation state of the sample on the rotation stage, the first signal being a pulse signal generated according to at least a rotation speed and a rotation angle of the rotation stage;
• a laser light source configured to irradiate the surface of the sample with a pulsed laser;
• a charge accumulation type sensor configured to detect light scattered or reflected from the surface of the sample;
• a detecting circuit configured to perform analog-digital conversion on and detect an output signal of the charge accumulation type sensor;
• a light emission timing signal generating circuit configured to generate a light emission timing synchronizing signal that is synchronized with a light emission timing signal for the pulsed laser of the laser light source;
• a trigger signal generating circuit configured to receive the light emission timing synchronizing signal and the first signal, generate a trigger signal for controlling a timing for charge accumulation in the charge accumulation type sensor and a timing for detection in the detecting circuit, the trigger signal being synchronized with the light emission timing synchronizing signal, and provide the trigger signal to the charge accumulation type sensor and the detecting circuit;
• a number-of-emitted-pulse calculating circuit configured to receive the light emission timing synchronizing signal and the first signal, and based on the light emission timing synchronizing signal and the first signal, calculate a number of pulses of the pulsed laser in each period, of a plurality of periods, of the first signal, based on the light emission timing synchronizing signal, at each pixel at a plurality of positions simultaneously, which are at a set of predetermined distances in a radial direction with respect to a center of the sample, along a circumferential line on the sample;
• and
• a processing system configured to measure a state of each position, associated with the rotation, on the circumferential line on the surface of the sample by using the detection signal and the number of pulses.