Micro-lithographic projection exposure apparatus has variable transmission filter which has refractive optical element with photo-chromic layer on which excitation light is irradiated by secondary illumination system

摘要

The exposure apparatus (10) has a primary illumination system (12) which directs the projection light generated by a light source (LS) towards a mask (14) to illuminate the illumination field (16). A projection lens (20) covers the illumination field in the underlying portion of the mask on a photosensitive layer (22). A variable transmission filter has a refractive optical element with a photo-chromic layer on which the excitation light is irradiated by a secondary illumination system, such that the absorption coefficient of the photo-chromic layer is changed.