Optical exposure apparatus and methods of using same, for patterning a workpiece and photo-cleaning the optical components in the apparatus, which can be contaminated by moisture and organic compounds in the atmosphere. The apparatus comprises an illumination optical system having a light source and one or more optical components, and a projection lens having an object plane and an image plane and one or more optical components. The optical exposure apparatus includes an exposure optical path or an exposure light beam through a predetermined space in the optical exposure system. An optical path deflection member for deflecting light is introduced into the exposure optical path so as to create a second optical path that differs from the exposure optical path. Also disclosed is a method of photo-cleaning the aforementioned optical components, including the steps of forming an exposure optical path and then changing this path to create a second optical path that differs from the exposure optical path. An additional method of photo-cleaning a projection lens is disclosed, including the steps of providing an illumination light beam along an optical axis, providing and inserting a photo-cleaning optical member having refractive power into the beam, and refracting the beam so as to illuminate the lens surfaces comprising the projection lens.