Patent ID: 7161670

Claim:
A system for inspection of substrates, comprising: a stage that supports the substrate, said stage being adapted to rotate and translate the substrate in one direction; a light source that provides a light beam illuminating a spot on the substrate at a grazing angle; a sensor array having a plurality of sensors thereon and positioned at a Fourier plane above the substrate to receive light scattered from the spot; a circuit that receives signals from the sensor array and determines whether the signals indicate a presence of a singularity on the substrate, wherein said circuit comprises: a filter that receives a signal from each of the plurality of sensors, and blocks any signal which is above a first threshold; an adder that receives and adds signals that pass through the first filter to provide an added signal; and a comparator that compares the added signal to a second threshold and issues a singularity indication if the added signal is above the second threshold.