| 摘要 |
PURPOSE:To facilitate the adjustment of the title position detector in a simple constitution by a method wherein the position of a pattern image re-focussed on a detecting surface is periodically oscillated in specific amplitude in the width direction of a photodetecting surface to be periodically detected according to the driving signals so that the detection signals reaching specific state when the pattern image is being oscillated centering on the photodetecting surface may be outputted. CONSTITUTION:When the exposed surface of a wafer 3 is beneath a focussing surface, a slit pattern image 16 is being oscillated at the end of the second auxiliary photodetecting surface 28c on the surface of a photoelectric conversion element 2. In such a state, a direction detecting signal S6 has a negative value while a position detecting signal S3 has zero value. Later, when the exposed surface of the wafer 3 is lifted passing the focussing surface of a projection optical system 2, the slit pattern image 16 intersects a photodetecting surface 28a in the R direction so that the position detecting signal S3 may be changed taking S curve shape by synchronous rectification (a). In such a constitution, the zero-cross point of this position detecting signal S3 is to indicate the coincidence position of the exposed surface with the focussing surface. |
