Static ceramic phosphor assemblies for high power, high luminance SSL-light sources for digital projection and specialty lighting

摘要

Laser pumped phosphor (LPP) technology has started to replace high intensity discharge lamps in digital projectors. LPPtechnology is typically based on garnet phosphors that are excited with blue laser diodes at 445 – 465 nm. The luminanceof LPP light sources can well surpass 1000 cd/mm~2 and thus address high luminance applications that could not benefitfrom the advantages of solid state lighting (SSL) so far. Due to the recent cost down of blue laser diodes, digitalprojectors with LPP light sources that make use of fast spinning phosphor wheels and laser powers >100 Watts are nowwidely commercially available.Another commercially available application of LPP technology are laser headlights. To avoid moving parts, laserheadlights make use of static phosphor assemblies, but they operate at only a few Watts of laser power. A static phosphorassembly consists of a ceramic phosphor that is bonded onto a heat spreader. Due to their good thermal and opticalproperties, static ceramic phosphors are excellent light converters even at higher powers. They enable high luminancelight sources with a luminous flux that is far beyond the flux needed for car headlights. Static converters will alsoimprove the performance of light sources for microscopy, machine vision and any other etendue limited specialtylighting application.We investigate factors that determine the achievable power and luminance such as irradiance limit, conversion efficacy,spot confinement and cooling. Experimental and numerical results are presented.