Ultra-bright light engine for projection displays
View Patent ↗A projector incorporating a prism and a plurality of light valves for modulating light that passes though the prism, wherein the color splitting-converging prism includes a dichroic coating having multiple layers of high and low index of refraction and ¼ wavelength thickness at each desired angle of incidence for reducing dichroic shift and thereby minimizing light loss.
1. For use in a projector incorporating a light engine with color splitting-converging prism, said prism having at least two prism elements wherein a first prism element comprises a red dichroic coating, a second prism element comprises a blue dichroic coating, the improvement comprising application of red and blue dichroic coatings to said respective prism elements, said coatings being characterized by respective reflectance per wavelength slopes steeper than −2% R/nm and 4% R/nm, respectively, for optimizing color separation within said prism and thereby increasing light throughput.
2. The improvement of claim 1 , wherein said respective reflectance per wavelength slopes are −6% R/nm and 8% R/nm, respectively.
3. The improvement of claim 1 , wherein said coatings consist of stacks of alternating layers of high and low index of refraction with layer thicknesses equivalent to ¼ wavelength at specific angles of incidence.
4. The improvement of claim 3 , wherein said coatings comprise 20 to 30 of said layers.
5. The improvement of claim 1 , wherein said dichroic coatings comprise alternating layers of TiO2 and SiO2.
6. The improvement of claim 5 , wherein said dichroic coating for the color blue is comprised of:
Thickness (um)
Material
0.19066
MgF2
0.022637
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.045302
TiO2
0.073405
SiO2
0.022637
TiO2
0.020536
TiO2
0.06900095
SiO2
0.0425814
TiO2
0.06900095
SiO2
0.0425814
TiO2
0.06900095
SiO2
0.020536
TiO2
7. The improvement of claim 5 , wherein said dichroic coating for the color red is comprised of:
Thickness (um)
Material
0.06514
SiO2
0.0803862
TiO2
0.1302744
SiO2
0.0803862
TiO2
0.06514
SiO2
0.061165
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.1223303
SiO2
0.07548
TiO2
0.061165
SiO2
0.06514
SiO2
0.0803862
TiO2
0.1302744
SiO2
0.0803862
TiO2
0.06514
SiO2
0.083546
MgF2
0.109806
ZrO2
0.0707337
Al2O3
8. The improvement of claim 1 , wherein said coatings are further characterized by having respective dichroic shifts less than first and second predetermined amounts, for minimizing light loss and thereby increasing light throughput.
9. The improvement of claim 8 , wherein said first and second predetermined amounts are 65 nm and 35 nm, respectively.
10. The improvement of claim 1 , wherein said coatings consist of multiple layers of high and low index of refraction and index matching layers, wherein layer thicknesses and materials for said multiple layers are chosen to provide prism dichroic coatings with dichroic shifts of less than 65 nm and less than 35 nm for blue and red, respectively, and thereby increase light throughput.
11. The improvement of claim 10 , wherein said dichroic coatings comprise alternating layers of TiO2 and SiO2.
12. The improvement of claim 10 , wherein said layer thicknesses and materials for said multiple layers are chosen to provide prism dichroic coatings with dichroic shifts of approximately 35 nm and 23 nm for blue and red, respectively.
13. Use of the improvement according to claim 1 in a 3-chip DMD projector utilizing one of either a Xe or UHP lamp with f#1.0–1.5.
14. Use of the improvement according to claim 1 in at least a 5-element prism within a 3-chip DMD projector.