| 摘要 |
PURPOSE:To surely remove a return signal by comparing a particle detection signal with its differential signal and deciding the return signal by a return decision means, and removing the return signal from an object to be processed by a processing means. CONSTITUTION:A detecting means 1 outputs a particle detection signal M1 and a differential signal generating means 2 outputs differential signal M2 of the detection signal M1. The return signal decision means 3 compares the particle detection signal M1 with the differential signal M2 and outputs a signal (e) deciding the return signal when the signal M2 is smaller; and a return signal removing means 4 removes a particle detection signal in the signal M1 which becomes the return signal from the object to be processed.
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