| 摘要 |
PROBLEM TO BE SOLVED: To obtain a measuring method whereby the best focus position, astigmatism, etc., of a projection optical system are quickly and accurately detected. SOLUTION: The measuring method for measuring focus information on an image projecting optical system comprises a step for projecting a mark through the optical system using illumination lights having different incident directions of their main beams, thereby achieving the superimposition of mark images with both illumination lights on an approximately image forming plane, and obtaining focus information on the optical system from deviation information between superposed mark images.
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