| 摘要 |
A projection exposure apparatus includes a projection optical system for projecting a pattern of a first object onto a second object, a correcting mechanism for changing an optical characteristic of the projection optical system, a positional information detecting device for detecting a relative positional relationship between first and second marks, which are disposed at different positions, wherein the positional information detecting device detects the first mark with the use of the projection optical system and without the use of the second mark, and detects the second mark without the use of the projection optical system, a discriminating device operable, after the detection of the relative positional relationship by the positional information detecting device is repeated at a predetermined time interval or successively, to discriminate a relation between first positional information obtained as a result of an earlier detection and second positional information obtained as a result of a later detection made by the positional information detecting device, and an actuator for actuating the correcting mechanism on the basis of the discrimination made by the discriminating device, to change the optical characteristic of the projection optical system.
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