Exposure apparatus and method

An exposure apparatus for exposing a pattern of a reticle onto an object to be exposed, via a projection optical system, utilizing exposure light, includes an optical element for determining a shape of an effective light source on a predetermined surface that substantially has a Fourier transformation relationship with the reticle, a detector for detecting the shape of the effective light source and a light intensity on the object, and a corrector for correcting a variance of performance of the projection optical system, and a controller for controlling the corrector based on a detection result of the detector.