DISTANCE MEASURING APPARATUS

摘要

PURPOSE:To reduce measurement errors caused by pattern distributing condition and line width and conduct high-accuracy measurement, by correcting a slice level of an edge distance detecting unit according to the edge distances. CONSTITUTION:A pattern 3a formed on a mask on a stage 4 is observed with an objective lens 5 as an image pick-up system. An enlarged image of the pattern 3a is detected with a photoelectric sensor 50 and distribution of luminous intensities is read into a memory 51 through an A/D converting circuit 102. An edge distance detecting unit 52 detects leading and trailing edge positions from a luminous intensity distribution waveform and the distance is displayed on a display unit 108. A slice level is corrected according to the edge distance subjected to measurement with a correcting unit 53. The correcting amount is stored as a table as predetermined after adding various conditions of the optical system and the edge distances. A distance-identifying unit 54 judges whether correction is necessary or not.