Projection display surface providing speckle reduction
View Patent ↗A projection display surface for reducing speckle artifacts from a projector having at least one narrow band light source having an incident visible wavelength band, wherein the incident visible wavelength band has an incident peak wavelength and an incident bandwidth, comprising: a substrate having a reflective layer that reflects incident light over at least the incident visible wavelength band; and a fluorescent agent distributed over the reflective layer, wherein the fluorescent agent absorbs a fraction of the light in the incident visible wavelength band and emits light in an emissive visible wavelength band having an emissive peak wavelength and an emissive bandwidth; wherein return light from the projection display surface produced when incident light in the incident visible wavelength band is incident on the projection display surface contains light in both the incident visible wavelength band and emissive visible wavelength band, thereby reducing speckle artifacts.
1. A projection display surface for reducing speckle artifacts from a projector having at least one narrow band light source having an incident visible wavelength band, wherein the incident visible wavelength band has an incident peak wavelength and an incident bandwidth, comprising:
a) a substrate having a reflective layer that reflects incident light over at least the incident visible wavelength band; and
b) a fluorescent agent distributed over the reflective layer, wherein the fluorescent agent absorbs a fraction of the light in the incident visible wavelength band and emits light in an emissive visible wavelength band having an emissive peak wavelength and an emissive bandwidth;
wherein return light from the projection display surface produced when incident light in the incident visible wavelength band is incident on the projection display surface contains light in both the incident visible wavelength band and emissive visible wavelength band, thereby reducing image artifacts, and wherein the projection display surface is polarization preserving such that polarization of the return light is substantially the same as the polarization of the incident light.
2. The projection display surface of claim 1 wherein the reduced image artifacts are speckle artifacts or observer metameric failure artifacts.
3. The projection display surface of claim 1 wherein the emissive bandwidth is wider than the incident bandwidth and is at least five nanometers in width.
4. The projection display surface of claim 1 wherein the emissive bandwidth is no more than 50 nanometers.
5. The projection display surface of claim 1 wherein the emissive peak wavelength is shifted relative to the incident peak wavelength.
6. The projection display surface of claim 5 wherein the emissive peak wavelength is shifted by no more than 40 nanometers relative to the incident peak wavelength.
7. The projection display surface of claim 1 wherein the fluorescent agent is a fluorescent dye.
8. The projection display surface of claim 7 wherein the fluorescent dye is rhodamine 6G, Alexa Fluor 532 or BODIPY 530/550.
9. The projection display surface of claim 1 wherein the fluorescent agent is a quantum dot.
10. The projection display surface of claim 9 wherein the quantum dots are fabricated using CdS, CdSe, ZnSe, InAs, GaAs or GaN.
11. The projection display surface of claim 1 wherein the fluorescent agent is uniformly distributed on the substrate.
12. The projection display surface of claim 1 wherein the fluorescent agent is sparsely distributed on the substrate.
13. The projection display surface of claim 1 wherein an amount of the fluorescent agent distributed over the reflective layer is adjusted to substantially minimize a speckle visibility.
14. The projection display surface of claim 1 wherein the substrate is made of a reflective material, and wherein the reflective layer corresponds to the top surface of the substrate.
15. The projection display surface of claim 1 further including a protective coating layer that protects the projection display surface.
16. The projection display surface of claim 15 wherein the fluorescent agent is included in the protective coating layer.
17. The projection display surface of claim 15 wherein the protective coating layer is applied over the top of the fluorescent agent.
18. The projection display surface of claim 1 wherein light in the incident visible wavelength band and the emissive visible wavelength band are perceived by a human observer to have the same color name.
19. The projection display surface of claim 1 wherein the fraction of the light in the incident visible wavelength band that is absorbed by the fluorescent agent is between 2% and 40%.
20. The projection display surface of claim 1 wherein the speckle artifacts are reduced by the mechanism of spectral broadening.
21. The projection display surface of claim 1 wherein the emissive peak wavelength is longer than the incident peak wavelength, and further including a second fluorescent agent distributed over the reflective layer, wherein the second fluorescent agent absorbs a fraction of the light in the incident visible wavelength band and emits light in a second emissive visible wavelength band having a second emissive peak wavelength and a second emissive bandwidth, the second emissive peak wavelength being shorter than the incident peak wavelength.
22. The projection display surface of claim 1 further including one or more light absorbing agents distributed over the reflective layer which absorb ambient light in one or more wavelength bands which do not substantially overlap with the incident visible wavelength band or the emissive visible wavelength band.
23. A projection display surface for reducing speckle artifacts from a color projector having at least three narrow band light sources having first, second and third incident visible wavelength bands, respectively, wherein each incident visible wavelength band has an associated incident peak wavelength and an associated incident bandwidth, comprising:
a) a substrate having a reflective layer that reflects incident light over at least the first, second and third incident visible wavelength bands; and
b) a first fluorescent agent distributed over the reflective layer, wherein the first fluorescent agent absorbs a fraction of the light in the first incident visible wavelength band and emits light over a first emissive visible wavelength band having a first emissive peak wavelength and a first emissive bandwidth;
wherein return light from the projection display surface produced when incident light in the first incident visible wavelength band is incident on the projection display surface contains light in both the first incident visible wavelength band and first emissive visible wavelength band, thereby reducing speckle artifacts, and wherein the projection display surface is polarization preserving such that polarization of the return light is substantially the same as the polarization of the incident light.
24. The projection display surface of claim 23 wherein the emissive bandwidth is wider than the incident bandwidth and is at least five nanometers in width.
25. The projection display surface of claim 23 wherein the first emissive peak wavelength is closer to the first incident peak wavelength than to either the second or third incident peak wavelengths.
26. The projection display surface of claim 23 wherein the first emissive visible wavelength band extends to no less than 30 nanometers away from the second or third incident peak wavelengths.
27. The projection display surface of claim 23 wherein the fraction of the light in the first incident visible wavelength band that is absorbed by the first fluorescent agent is between 2% and 40% and the fraction of the light in the second and third incident visible wavelength bands that is absorbed by the first fluorescent agent is negligible.
28. The projection display surface of claim 23 further including:
c) a second fluorescent agent distributed over the reflective layer, wherein the second fluorescent agent absorbs a fraction of the light in the second incident visible wavelength band and emits light over a second emissive visible wavelength band having a second emissive peak wavelength and a second emissive bandwidth;
wherein return light from the projection display surface produced when incident light in the second incident visible wavelength band is incident on the projection display surface contains light in both the second incident visible wavelength band and second emissive visible wavelength band.
29. The projection display surface of claim 28 further including:
d) a third fluorescent agent distributed over the reflective layer, wherein the third fluorescent agent absorbs a fraction of the light in the third incident visible wavelength band and emits light over a third emissive visible wavelength band having a third emissive peak wavelength and a third emissive bandwidth;
wherein return light from the projection display surface produced when incident light in the third incident visible wavelength band is incident on the projection display surface contains light in both the third incident visible wavelength band and third emissive visible wavelength band.