Abstract: Disclosed is a system for the signal processing of pattern profile information detected by optically or electronically scanning a pattern on an object such as a semiconductor wafer or a mask. The system includes a pattern information detector responsive to the scanning to generate an electric detection signal of a time series corresponding to the pattern along the scanning direction, position detecting means for generating a position signal discriminative for example of the direction of scanning each time the scanning advances a predetermined unit amount, and sampling extract means responsive to the position signals to successively sample the detection signal and obtain digital data of the pattern excluding any overlapping data of the pattern sampled at the same positions whereby even if the scanning involves minute oscillations of the scanning speed, the resulting noise in the detection signal is eliminated and an accurate pattern information signal corresponding to the absolute positions is extracted.