In a research project on laser lighting, involving the Danish lamp manufacturer Focus Lighting and DTU Fotonik, one task was to demonstrate the reshaping of a Lambertian light distribution from a phosphor-converted laser beam to a completely uniform circular light distribution. The developed reflector is now being tested in a prototype lamp at Danish Outdoor Lighting Lab. in Albertslund, Denmark.
PROBLEM
White light generated by converting blue light via a phosphor material is emitted in a Lambertain angular distribution. For some illumination purposes it is desired to have the illumination in a uniform manner in which case one needs an optical element to reshape the light distribution.
SOLUTION
The lamp prototype comprises a freeform metal reflector with a hole in the middle. Blue laser light is launched through the hole to hit a small reflective plate with phosphor. A Lambertian distribution of converted white light is reflected back from the phosphor plate towards the reflector, which reshapes the angular light distribution to form a uniformly illuminated circular area 6 meters under the lamp.
