An imagery characteristic is corrected by changing the position and/or
orientation of a reticle or lens elements of a projection lens system.
Correction of the imagery characteristic, however, causes displacement of
the projected pattern image of the reticle. The relation between the
driving amount of the lens elements and reticle and the lateral
displacement of the center of the pattern image of the reticle is stored
as a table in advance. When the lens elements and/or the reticle are
driven, lateral displacement of the pattern image can be obtained by
accessing the table. Alternatively, the lateral displacement can be
determined using a base-line amount corresponding to a distance between a
detection center of a substrate position detector and a center of the
projected image. Once the pattern image displacement is determined, the
substrate can be accurately positioned. In another arrangement, a mask
alignment method prevents positional shift of a projected image of a mask
pattern even if the projection magnification of the projection optical
system is changed.
