An exposure method includes, in a case of exposing unmeasurable shots which are arranged linearly and whose focus value cannot be measured and a measurable shot which is adjacent to the unmeasurable shots and whose focus value can be measured, exposing alternately the measurable shot and the unmeasurable shots such that the unmeasurable shots are exposed using the focus value of the adjacent measurable shot exposed immediately before the unmeasurable shots.

Fringe-projection autofocus system devoid of a reference mirror. Contributions to error in determination of a target surface profile caused by air non-uniformities measured based on multiple measurements of the target surface performed at different wavelengths, and/or angles of incidence, and/or grating pitches and subtracted from the measured profile, rendering the system substantially insensitive to presence of air turbulence. Same optical beams forming a fringe irradiance pattern on target surface are used for measurement of the surface profile and reduction of measurement error by the amount attributed to air turbulence.