a projection aligner includes a light source , a condenser lens system for directing light from the light source onto a mask on which a circuit pattern is formed , a projecting lens system for collecting on the surface of a wafer the light transmitted through the mask , and an aperture member disposed between the light source and the condenser lens system . the aperture member includes a transmitting zone for transmitting light from the light source and a phase shift member for producing a predetermined phase difference between light transmitted through the transmitting zone and light transmitted through a region surrounding the transmitting zone .