Anti-glare filter for illumination systems, including LED lighting systems
An anti-glare film for a light source is disclosed. The light source may be a light source with a Lambertian distribution, such as an LED light source. The anti-glare film may include a micro-frustum array to reduce the angular distribution of the light source and thus reduce glare. In some implementations, anti-glare film may further include a light shaping diffuser.
1. A lighting system, comprising:
a transparent film having a first side and an opposed second side, the first side configured to receive light from an overhead illumination light source having a Lambertian distribution and the second opposed side patterned with frustums designed to narrow the angular distribution of light output from the transparent film in order to reduce glare; and
wherein the frustums reduce an intensity of light at ±60 degrees by at least a factor of 4 compared with a Lambertian distribution.
2. The lighting system of claim 1 wherein the frustums comprise an array of pyramidal frustums.
3. The lighting system of claim 1 , wherein the frustums comprise an array of conical frustums.
4. The lighting system of claim 1 where the frustums comprise concentric rings having a trapezoidal cross-section.
5. The lighting system of claim 1 , wherein the first side of the transparent film comprises a light shaping diffuser.
6. The lighting system of claim 1 , where the second side of the transparent film is patterned to implement a light shaping diffuser, wherein the geometric heights of the frustums and light shaping diffuser are added together to form a surface relief pattern.
7. The lighting system of claim 1 , wherein the overhead illumination light source is an LED light source.
8. A lighting system, comprising:
a transparent film having a first side to receive light from an LED illumination light source and an opposed second side with a micro frustum array to narrow a bidirectional scatter distribution from the LED illumination light source to a narrower optical distribution to reduce glare;
one of the first or second side patterned with a light shaping diffuser (LSD); and
wherein the micro frustum array reduces an intensity of light at ±60 degrees by at least a factor of 4 compared with a Lambertian distribution.
9. The lighting system of claim 8 , wherein the first side is patterned with the LSD.
10. The lighting system of claim 8 wherein the second side is patterned with the LSD.
11. The lighting system of claim 8 , wherein the LSD is configured to improve optical homogeneity.
12. The lighting system of claim 8 , wherein the LSD comprises a surface relief structure including pseudo-random, non-periodic structures.
13. An overhead lighting system, comprising:
a Light Emitting Diode (LED) light source having an output with a Lambertian distribution;
a transparent film having a first side facing the LED light source and an opposed second side;
the second side patterned with a surface microstructure designed to narrow a bidirectional scatter distribution from the LED light source into a narrower optical distribution to reduce glare; and
wherein the surface microstructure reduces an intensity of light at ±60 degrees by at least a factor of 4 compared with a Lambertian distribution.
14. The overhead lighting system of claim 13 , wherein the surface microstructure comprises a micro frustum array.
15. The overhead lighting system of claim 13 , wherein the surface microstructure comprises a set of concentric rings each having a trapezoidal cross section.
16. The overhead lighting system of claim 13 , wherein the first side is patterned with a light shaping diffuser (LSD) to perform at least one light shaping function on the light received from the LED light source.