Laser illuminated micro-mirror projector
View Patent ↗A digital image projector includes a plurality of light modulation assemblies and a dichroic combiner. Each light modulation assembly includes at least one laser light source configured to provide an illumination beam, an optional a coated surface, and a spatial light modulator. If the coated surface is present, the respective laser light source is configured to direct the illumination beam to the coated surface, which directs the illumination beam toward the respective spatial light modulator. Otherwise, the respective laser light source is configured to direct the illumination beam directly toward the respective spatial light modulator. The spatial light modulator redirects output modulated light back to the coated surface, if present, and out of the corresponding light modulation assembly. The dichroic combiner directs the output modulated light from each of the plurality of light modulation assemblies toward a projection lens for projection onto a display surface.
1. A digital image projector comprising:
a plurality of light modulation assemblies, each light modulation assembly comprising:
at least one laser light source configured to provide an illumination beam,
a coated surface treated to transmit and reflect light according to its incident angle, wherein the coated surface has a mirror coating design, an edge filter coating design, a bandpass filter coating design, or a notch filter coating design, and
a spatial light modulator comprising an array of micromirrors,
wherein the coated surface is configured to direct the illumination beam toward the spatial light modulator, and
wherein each micromirror in the spatial light modulator is selectively actuable to modulate the illumination beam and to redirect output modulated light back to the coated surface and out of the corresponding light modulation assembly; and
a dichroic combiner comprising a plurality of surfaces treated to selectively transmit or reflect light according to its wavelength and configured to direct the output modulated light from each of the plurality of light modulation assemblies toward projection optics for projection onto a display surface.
2. The digital image projector of claim 1 , wherein each of the coated surfaces is substantially parallel to its respective spatial light modulator.
3. The digital image projector of claim 1 , wherein each of the coated surfaces is configured to reflect the illumination beam and to transmit modulated light.
4. The digital image projector of claim 1 , wherein each of the coated surfaces is disposed to transmit the illumination beam and to reflect modulated light.
5. The digital image projector of claim 1 , wherein each of the coated surfaces is treated to transmit light over a first range of angles relative to normal and to reflect light over a second range of angles relative to normal, and wherein the second range of angles is larger than the first range.
6. The digital image projector of claim 1 , wherein each of the coated surfaces is treated to transmit light over a first range of angles relative to normal and to reflect light over a second range of angles relative to normal, and wherein the first range of angles is larger than the second range.
7. The digital image projector of claim 1 , wherein each laser light assembly further comprises a polarization rotator configured to alternate light polarization between two orthogonal states and configured to be located between the respective at least one laser light source and the respective coated surface in a path of the respective illumination beam, and wherein the digital image projector is a stereoscopic digital image projector.
8. The digital image projector of claim 7 , wherein the coated surfaces and the surfaces of the dichroic combiner minimize a phase difference between the two orthogonal states over operational angles and wavelengths.
9. The digital image projector of claim 8 , wherein the phase difference between the two orthogonal states is less than 20 degrees.
10. The digital imager projector of claim 7 , further comprising a compensation material configured to, at least in part, cause the phase difference between the two orthogonal states to be less than 20 degrees.
11. The digital image projector of claim 7 , wherein the polarization rotator is rotatable.
12. The digital image projector of claim 7 , wherein the polarization rotator is a shutter having a reflective portion.
13. The digital image projector of claim 7 , wherein the coated surfaces and the surfaces of the dichroic combiner substantially preserve a polarization state of transmitted and reflected light.
14. A digital image projector comprising:
a plurality of light modulation assemblies, each light modulation assembly comprising:
at least one laser light source configured to provide an illumination beam, and
a spatial light modulator comprising an array of micromirrors, each micromirror selectively actuable to modulate the illumination beam and to redirect output modulated light out of the corresponding light modulation assembly; and
a dichroic combiner comprising a plurality of dichroic surfaces treated to selectively transmit or reflect light according to its wavelength and configured to direct the output modulated light from each of the plurality of light modulation assemblies toward projection optics for projection onto a display surface, wherein each dichroic surface is made using a multi-layer dielectric thin film coating.
15. The digital image projector of claim 14 , wherein each laser light assembly further comprises a polarization rotator configured to alternate light polarization between two orthogonal states and configured to be located between the respective at least one laser light source and the respective spatial light modulator in a path of the respective illumination beam, and wherein the digital image projector is a stereoscopic digital image projector.
16. The digital image projector of claim 15 , wherein the dichroic combiner substantially preserves a polarization state of transmitted and reflected light.
17. The digital image projector of claim 14 , wherein the projection optics includes a projection lens with a back focus to focal length ratio greater than 2.5:1.
18. The digital image projector of claim 15 , wherein the coated surfaces and the surfaces of the dichroic combiner minimize a phase difference between the two orthogonal states over operational angles and wavelengths, and wherein the phase difference between the two orthogonal states is less than 20 degrees.
19. The digital image projector of claim 15 , wherein the coated surfaces and the surfaces of the dichroic combiner minimize a phase difference between the two orthogonal states over operational angles and wavelengths, and wherein the phase difference between the two orthogonal states is substantially zero degrees.
20. The digital image projector of claim 15 , wherein an overall light throughput of both orthogonal polarization states from each laser light source is substantially equal.