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. An optical system for a digital micromirror device illuminator, comprising:
a light emitting diode (LED) array;
a tapered non-imaging collection optic having an input aperture in optical communication with the LED array to receive optical energy emitted by the LED array and having an output aperture;
a reflective aperture stop; and
a telecentric lens system disposed between the tapered non-imaging collection optic and the reflective aperture stop along an optical axis defined between the LED array and the reflective aperture stop, the telecentric lens system 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 toward an image plane on the optical axis, wherein the reflective aperture stop provides reflected optical energy that propagates from the output aperture of the tapered non-imaging collection optic through the input aperture of the tapered non-imaging collection optic and is incident at the LED array.
2. The optical system of claim 1 wherein the object plane and the image plane are coincident on the optical axis.
3. The optical system of claim 2 wherein the object plane and the image plane are located at the output aperture of the tapered non-imaging collection optic.
4. The optical system of claim 1 wherein the reflected optical energy incident at the LED array is diffusely reflected and wherein at least a portion of the diffusely reflected optical energy propagates from the input aperture of the tapered non-imaging collection optic to the output aperture of the tapered non-imaging collection optic.
5. The optical system of claim 1 further comprising a hollow light integrator having an input face with an input aperture therein and an output face with an output aperture therein, the input aperture of the hollow light integrator being adjacent to the output aperture of the tapered non-imaging collection optic.
6. The optical system of claim 5 wherein the input face and the output face of the hollow light integrator are tilted with respect to each other.
7. The optical system of claim 5 wherein the object plane and the image plane are coincident on the optical axis and located at the output aperture of the hollow light integrator.
8. The optical system of claim 1 wherein the LED array is an ultraviolet LED array.
9. The optical system of claim 1 wherein the reflective aperture stop comprises a transmissive central region surrounded by a reflective outer region.
10. The optical system of claim 5 wherein the tapered non-imaging collection optic comprises an output face comprising the output aperture of the tapered non-imaging collection optic and wherein the output face of the tapered non-imaging collection optic is larger than the input aperture of the hollow light integrator.