Light redirecting element comprising a forward diffracting region and a scattering region
View Patent ↗Improved Light Re-directing Elements (ILRE) are provided in which a diffracting region is combined with a light scattering region to correct angular chromatic dispersion. Further embodiments include optical devices and systems using ILRE to reduce moiré, efficiently re-direct light, improve spatial and angular color and luminance uniformity, and reduce wavelength dispersion. In one embodiment, the light scattering region is a volumetric anisotropic light scattering region. Embodiments are included for use of ILRE in light emitting devices, displays and light fixtures.
1. An optical element comprising:
a) an input surface;
b) an output surface;
c) a light transmissive diffractive region;
d) a light scattering region optically coupled to the light transmissive diffractive region and disposed between the light transmissive diffractive region and the output surface;
wherein a portion of incident light with a wavelength, λ, incident at an angle θ 1 is diffracted forward by the light transmissive diffractive region and subsequently diffused by the light scattering region such that a ratio of angular diffusion of the light scattering region to angular chromatic dispersion of at least one light transmissive diffractive element is greater than 0.5.
2. The optical element of claim 1 wherein θ 1 is greater than 30 degrees.
3. The optical element of claim 1 wherein λ is selected from a wavelength range of 400 to 700 nanometers.
4. The optical element of claim 1 wherein θ 1 is an angle selected from a range between 50 and 80 degrees.
5. The optical element of claim 1 wherein the light transmissive diffractive region is a linear diffraction grating comprising linear diffractive elements oriented parallel to a first direction.
6. The optical element of claim 5 wherein the linear diffractive elements have a substantially triangular cross section.
7. The optical element of claim 5 wherein the linear diffractive elements have a substantially rectangular cross section.
8. The optical element of claim 1 wherein the light scattering region anisotropically scatters light and has a full angular width at half maximum intensity in a first plane comprising the first direction less than a full angular width at half maximum intensity in a second plane orthogonal to the first plane.
9. The optical element of claim 1 wherein the light scattering region anisotropically scatters light and has a full angular width at half maximum intensity in a first plane comprising the first direction greater than a full angular width at half maximum intensity in a second plane orthogonal to the first plane.
10. The optical film of claim 1 wherein a ratio of angular diffusion of the light scattering region to angular chromatic dispersion of at least one light transmissive diffractive element is greater than 1.
11. The optical element of claim 1 wherein light emitted by the optical element from the output surface has a peak intensity within 30 degrees from normal of the output surface.
12. The optical element of claim 1 wherein the light scattering region comprises a volumetric light scattering material.