Pattern detecting apparatus

摘要

A pattern detecting apparatus is disclosed which comprises, in order to detect the center of a positioning pattern on a sample with high accuracy in a wide range, means for illuminating the positioning pattern, means for defining an illumination range in which the positioning pattern is illuminated, means for focusing reflected light from the positioning pattern on a predetermined image plane, means for electrically detecting a bright and dark image on the image plane in accordance with positions on the image plane, means for removing a signal corresponding to the outside of the illumination range from the output signal of the detecting means and for holding, in place of the removed signal, a level of the output signal produced within the illumination range, and means for detecting a position of the center of the positioning pattern from the output signal of the holding means.