Patent ID: 8288943

Claim:
An illumination device comprising: a light emitting diode (LED) arranged to emit LED emission; a transmissive support comprising a luminescent material arranged to absorb at least part of the LED emission, and emit luminescent material emission wherein the LED and the luminescent material are configured to generate light of a predetermined color; a translucent exit window arranged to transmit at least part of the light; a LED cavity and a diffuser cavity, wherein the LED cavity has a LED cavity side wall and a LED cavity cross section, and the diffuser cavity has a diffuser cavity side wall and a diffuser cavity cross section, wherein, relative to the LED, the transmissive support is downstream of the LED and upstream of the translucent exit window; the LED cavity is upstream of the transmissive support and downstream of the LED; the diffuser cavity is downstream of the transmissive support and upstream of the translucent exit window; the ratio of the diffuser cavity cross section and LED cavity cross section is larger than 1; wherein the LED cavity side wall comprises a LED cavity reflector arranged to reflect at least one LED emission and luminescent material emission back into the LED cavity; wherein the transmissive support has a thickness (d 1 ) in the range of 0.1 to 5 mm; wherein the LED cavity reflector has a reflector thickness (d 2 ) in the range of 0.2 to 5 mm; wherein the thickness ratio of the thickness (d 2 ) and the thickness (d 1 ) is in the range of 0.5 to 10.