Abstract: An optical system for illuminating an arcuate field efficiently and uniformly using a short arc source. A first light source having a length along its axis of symmetry emits light with angular uniformity 360.degree. in azimuth about its axis of symmetry. This light is divided into a plurality of sections of equal angular extent in azimuth and recombined to form adjacent secondary light sources while preserving the uniformity of angular uniformity in each section and simultaneously orienting the sections of light about parallel remote from the first source of light which has a length axes in each section. This forms a second source of light equal to the sum of the lengths of the secondary sources of light with uniform angular distribution over an angular extent of nearly 360.degree. divided by the number of the secondary light sources. By appropriate selection of parameters the difference in the numerical apertures of the illuminated arcuate field is selectable.