Off-state light baffle for digital projection
View Patent ↗A light modulation assembly for a digital projection apparatus comprising: a solid-state light source that provides an illumination beam; a spatial light modulator having a plurality of tiltable micro-mirrors, each micro-mirror being actuable to tilt with respect to a tilt axis between a first tilt position that provides on-state light and a second tilt position that provides off state light, and wherein the micro-mirrors deflect the illumination beam along an arced path defining a deflection plane as they are tilted between the first tilt position and the second tilt position; and a light baffle disposed alongside the optical axis and in the path of the off state light from the micro-mirrors, the light baffle having a light-trapping surface adapted to absorb the off-state light from the micro-mirrors on the spatial light modulator, the light-trapping surface having a plurality of protruding fins that extend outward from the light-trapping surface at an oblique angle.
1. A light modulation assembly for a digital projection apparatus comprising:
a solid-state light source that provides an illumination beam;
a spatial light modulator disposed in the path of the illumination beam, the spatial light modulator having a plurality of tiltable micro-mirrors, each micro-mirror being actuable to tilt with respect to a tilt axis between a first tilt position that provides on-state light and a second tilt position that provides off-state light, wherein the micro-mirrors deflect the illumination beam along an optical axis to provide the on-state light when they are at the first tilt position, and the micro-mirrors deflect the illumination beam away from the optical axis to provide the off-state light when they are at the second tilt position, and wherein the micro-mirrors deflect the illumination beam along an arced path defining a deflection plane as they are tilted between the first tilt position and the second tilt position; and
a light baffle disposed alongside the optical axis and in the path of the off-state light from the micro-mirrors, the light baffle having a light-trapping surface adapted to absorb the off-state light from the micro-mirrors on the spatial light modulator, the light-trapping surface having a plurality of channels extending in a lengthwise direction, wherein each channel is defined by protruding fins that extend outward from the light-trapping surface at an oblique fin angle with respect to the deflection plane, the lengthwise direction of the channels being substantially parallel to the deflection plane.
2. The light modulation assembly of claim 1 wherein the protruding fins are oriented at a fin angle of less than 60 degrees relative to the deflection plane.
3. The light modulation assembly of claim 1 wherein the protruding fins are shaped and oriented such that the off-state light undergoes at least 2 reflections before exiting the light-trapping surface.
4. The light modulation assembly of claim 1 wherein the fins are tapered to a knife edge.
5. The light modulation assembly of claim 4 wherein the fins have two side surfaces, and wherein at least one of the side surfaces is beveled.
6. The light modulation assembly of claim 1 wherein the channels have rounded bottoms.
7. The light modulation assembly of claim 1 wherein the channels have beveled bottoms.
8. The light modulation assembly of claim 1 wherein the light-trapping surface is oriented at an oblique slope angle with respect to the deflection plane.
9. The light modulation assembly of claim 8 wherein the fin angle and the slope angle are selected together with a channel width and a fin shape including a fin thickness such that substantially all of the off-state light undergoes at least 2 reflections before exiting the light-trapping surface.
10. The light modulation assembly of claim 1 wherein the light baffle is made using a light absorbing material.
11. The light modulation assembly of claim 1 wherein the light-trapping surface is coated with a light absorbing material.
12. The light modulation assembly of claim 1 wherein the light-trapping surface is treated such that it is light absorbing.
13. The light modulation assembly of claim 1 wherein the light baffle is notched to prevent interference between the light baffle and the on-state light from the micro-mirrors on the spatial light modulator.
14. The light modulation assembly of claim 1 wherein the light baffle includes a fluid conduit located behind the light-trapping surface through which cooling fluid is circulated in order to remove heat from the light baffle.
15. A digital projection apparatus including one or more light modulation assembly according to claim 1 , together with projection optics for projecting the on-state light from the spatial light modulators in the one or more image forming assemblies onto a display surface.
16. The digital projection apparatus of claim 15 wherein the digital projection apparatus is a color projection apparatus adapted to project color digital image data having at least three color channels, and wherein the color projection apparatus includes at least three light modulation assemblies having different color light sources.