A lighting panel comprises a light source and a light modifying panel positioned over the light source, in the form of a set of protrusions over the base, the protrusions facing the light source. The protrusions comprise circular/elliptical/polygonal cylinders or cone sections with a small cone taper angle.
1. A lighting unit, comprising:
a light source comprising an array of LEDs with a first pitch; and
a light modifying panel positioned over the light source for modifying the light output from the light source before it enters a space to be illuminated,
wherein the panel comprises a base and a set of protrusions over the base, the protrusions facing the light source, the set of protrusions having a second pitch different from the first pitch,
wherein the protrusions comprise circular, elliptical or at least 5-sided polygonal cylinders, or circular, elliptical or at least 5-sided polygonal cone sections, having a flat circular elliptical or polygonal top, wherein for cone sections the cone taper angle is less than 5 degrees.
2. A unit as claimed in claim 1 , wherein for cone sections, the cone taper angle is less than 2 degrees.
3. A unit as claimed in claim 1 , wherein for cone sections, the cone taper angle is less than 1 degree.
4. A unit as claimed in claim 1 , wherein the base comprises a light scattering surface on a side opposite the protrusions.
5. A unit as claimed in claim 1 , wherein the tips of the protrusions are provided with a scattering surface.
6. A unit as claimed in claim 1 , further comprising a diffuser between the light source and the panel.
7. A unit as claimed in claim 1 , wherein the panel is injection moulded.
8. A unit as claimed in claim 1 comprising a ceiling luminaire.
9. A lighting unit, comprising:
a light source comprising an array of LEDs with a first pitch; and
a light modifying panel positioned over the light source for modifying the light output from the light source before it enters a space to be illuminated,
wherein the panel comprises a base and a set of protrusions over the base, the protrusions facing the light source, the set of protrusions having a second pitch different from the first pitch,
wherein the protrusions comprise circular, elliptical or at least 5-sided polygonal cylinders, or circular, elliptical or at least 5-sided polygonal cone sections, having a flat circular elliptical or polygonal top, wherein for cone sections the cone taper angle is less than 5 degrees,
wherein the protrusions each have a height H which satisfies H>N (D−H*tan α), where α is the cone taper angle with α=0 for cylinders, D is the diameter of the tip, and N is given by 1/N=tan(sin −1 (sin 35/n)) where n is the refractive index of the panel material.
10. A unit as claimed in claim 9 , wherein N is in the range 2.3 to 2.7.
11. A unit as claimed in claim 10 , further comprising a beam shaping optical arrangement provided over the LED array.
12. A unit as claimed in claim 11 , wherein the beam shaping optical arrangement performs a collimation function.
13. A unit as claimed in claim 11 , wherein the beam shaping optical arrangement performs a batwing optical distribution function.
14. A unit as claimed in claim 11 , wherein the beam shaping optical arrangement comprises at least first and second different types of lens.