Disclosed is an exposure apparatus for printing, by exposure, a pattern
of an original on a substrate, which includes a housing tightly filled with a predetermined
ambience and for accommodating therein at least a portion of an exposure light
optical axis, and a detection system having an optical system, wherein a portion
of a light path of the detection system is disposed in a first space enclosed by
the housing, and wherein at least another portion of the detection system including
an electric element thereof is disposed in a second space outside the housing.