Hollow light integrator for light emitting diode digital micromirror device illuminator
Described are optical systems for a digital micromirror device (DMD) illuminator. The optical systems include a LED array, a tapered non-imaging collection optic, a reflective stop and a telecentric lens system. The telecentric lens system is disposed along an optical axis defined between the tapered non-imaging collection optic and the reflective stop. The telecentric lens system is configured as a first half of a symmetric one to one imager for an object plane on the optical axis and as a second half of the symmetric one to one imager for optical energy reflected from the reflective aperture stop. The optical systems reclaim optical energy emitted by the LED array that does not initially pass through the reflective stop and provide an improved intensity distribution at the DMD. Reductions in stray light and the thermal loads on the illuminator and DMD are achieved relative to conventional illumination systems for DMDs.
1. A hollow light integrator, comprising:
a hollow body having an input aperture at a first end, an output aperture at a second end opposite to the first end and a plurality of inside walls extending along an axis from the input aperture to the output aperture, each of the inside walls comprising a reflective surface, the first end comprising an input face that is normal to the axis and the second end comprising an output face that is tilted with respect to the axis; and
an optical field stop having a parallelogram shape and being disposed at the output face at the second end.
2. The hollow light integrator of claim 1 wherein the parallelogram shape is oriented with respect to the optical axis to compensate for a keystone distortion of an image formed by an imaging system in optical communication with the hollow light integrator.
3. The hollow light integrator of claim 1 wherein the first end of the hollow body includes a reflective region that surrounds the input aperture.
4. The hollow light integrator of claim 1 wherein the hollow body is formed of a fused silica material.
5. The hollow light integrator of claim 1 further comprising a taper having an output face in contact with the first end of the hollow body and wherein the output face of the taper is larger than the input aperture of the hollow body.
6. The hollow light integrator of claim 5 wherein the first end of the hollow body that is in contact with the output face of the taper has a reflective coating.
7. The hollow light integrator of claim 1 wherein the hollow body comprises four pieces of glass each having a reflective coating on an inner surface of the piece of glass.
8. The hollow light integrator of claim 1 wherein the hollow body comprises four metal sheets each having a reflective mirrored surface.
9. The hollow light integrator of claim 1 wherein the optical field stop has a non-rectangular parallelogram shape.