Projection optical device

摘要

An optical device projects a pattern of a first object on a second object through an optical system. Changes in the temperature of the optical system or changes in the ambient temperature of the optical system are detected and, on the basis of the detected temperature, any focus deviation or displacement of the optical system due to the temperature change is corrected. The correction of the focus deviation is achieved by controlling the temperature of the optical system or the position of the second object.