Fly’s eye arrays are used in pairs to spatially homogenize or make uniform a light source at the illumination plane.  The two arrays are called the objective array and the field array and are used with a condenser lens.  The objective array images the source at the field array.  The field array reimages with the condenser lens all of the fields so they overlap at the illumination plane and create a uniform irradiance.  A typical fly’s eye array has from seven to eleven channels in each direction.  Each of these channels are optically overlapped at the illumination plane to achieve uniform light from a nonuniform source.