摘要：

A pattern detector for precise position measurement of a wafer, used in a mask aligner used in manufacturing a semiconductor device is disclosed. A positioning pattern on the wafer is magnified and projected by a magnifying optical system and the magnified projected image is precisely detected to determine a position of the positioning pattern. As a light to form the magnified projected image, plurality of monochromatic lights of different wavelengths are available through optical filters and the magnifying optical systems are arranged one for each of the monochromatic lights. By selecting one of the optical filters, the magnified projected image of the positioning pattern is formed by the monochromatic light having an optimum wavelength to the wafer and the precise position of the positioning pattern on the wafer can be detected.

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