A system for combining outputs of multiple light sources includes a plurality of light sources, and a rotatable fold mirror oriented at an angle so as to reflect beams from each of the light sources towards the same direction at various times during its rotation. A projection optical system directs the beams towards a substrate. The light sources can be pulsed lasers or lamps. The rotatable fold mirror can be mounted on an air bearing, a magnetic bearing, or a fluid bearing, and can be oriented at about 45 degrees relative to the vertical. An optional fold mirror for folding an optical axis of the system is between the rotatable fold mirror and the projection optical system. The fold mirror can counter-rotate in synchronization with the rotatable fold mirror so as to keep the direction of the beams constant. The rotatable fold mirror can be mounted on an air bearing, which in turn is mounted on an air bearing support. The air bearing and the air bearing support have a pass hole for passing the beams. Alternatively, the rotatable fold mirror can be mounted below an air bearing support.