| 摘要 |
Disclosed is a focal point position detecting method and a focal point position detecting system, in which an object having a mark is moved in an optical axis direction of a projection optical system, and, with respect to different movement positions of the object, the mark of the object is illuminated through the projection optical system. An image of the mark is picked up to produce imagewise information The imagewise information is corrected in accordance with an intensity of light illuminating the mark. The focal point position of the projection optical system is then detected on the basis of the imagewise information corrected with respect to each of the different movement positions of the object. With this arrangement, even if the intensity of illumination light changes, the influence upon the detection of focal point position is reduced, and the detection can be simple without complicatedness.
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