LED module with outlet lens
A lighting module comprises an LED and a lens over the LED. The lens has a beam shaping surface and a pass through surface with a stepped profile. The steps of the stepped profile each comprise a riser portion and an output portion, wherein the riser portions are parallel with the ray direction passing through the surface at that location and the output portions are normal to the ray direction passing through the surface at that location. The pass through surface for example performs no beam shaping function. The stepped profile enables the thickness of the lens to be reduced to reduce the amount of material needed.
1. A lighting module comprising:
an LED having a light output area; and
a refractive lens over the LED for providing beam shaping of the light output of the LED, wherein the lens comprises an inner surface and an outer surface, wherein the outer surface is a smooth beam shaping surface which provides a beam shaping function essentially only via refraction, and the inner surface has a stepped profile, wherein the inner surface is nearer to the LED than the outer surface,
wherein the steps of the stepped profile each comprise a riser portion and an output portion, wherein the riser portions are parallel with a ray direction originating from a central point of the light output area of the LED and the output portions are normal to said ray direction.
2. A module as claimed in claim 1 , wherein the LED generates an output with a Lambertian intensity distribution.
3. A module as claimed in claim 1 , wherein output intensity of the module has a batwing distribution.
4. A module as claimed in claim 3 , wherein the beam shaping surface is shaped such that rays emitted along the optical axis are refracted away from the optical axis, and rays approaching 90° to the optical axis are refracted towards the optical axis.
5. A module as claimed in claim 1 , wherein the lens comprises a peanut lens.
6. A module as claimed in claim 1 , wherein the minimum thickness between the inner and outer surfaces is less than 1 mm.
7. A module as claimed in claim 6 , wherein the minimum thickness is less than 0.8 mm and more preferably less than 0.6 mm.
8. A module as claimed in claim 1 , wherein the maximum thickness between the inner and outer surfaces over the whole area of the inner and outer surfaces is less than three times the minimum thickness.
9. A module as claimed in claim 8 , wherein the maximum thickness between the inner and outer surfaces over the whole area of the inner and outer surfaces is less than double the minimum thickness.
10. A module as claimed in claim 1 , wherein the distance between the LED and the inner surface is in the range 1 to 20 times the lateral extent of a light output surface of the LED.
11. A module as claimed in claim 1 , wherein the width of the outer surface of the lens at its base is in the range 0.5 to 3 times the lens height.
12. A module as claimed in claim 1 , wherein the lens is formed of PC, PMMA, PET, PEN or COC.