New collection systems for multi LED light engines

Sheng Han Tu*, Jui-Wen Pan, Chih Ming Wang, Yeeu Chang Lee, Jenq Yang Chang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Light emitting diodes (LEDs) have numerous advantages as light sources in projectors. LEDs are more compact, exhibit a larger color gamut, have a longer lifetime, and need a lower supply voltage. However, there is still one important disadvantage: the optical power per unit of étendue (luminance) of an LED is significantly low. As a result of the étendue limitations of LEDs, the projected flux on the screen will not be high. Despite this shortcoming, LED's are still of great interest for low power applications because of their other superior properties. Thus we collect the available light flux optimally and combine multiple high luminance LEDs within the system. In this study we discuss three collection systems designed to collect the LED flux with high optical efficiency while retaining small device size. The best collection efficiency attained with our collection systems is 96%. The fabrication tolerance and cost of our collection systems are also analyzed.

Original languageEnglish
Pages (from-to)318-322
Number of pages5
JournalOptical Review
Issue number3
StatePublished - 1 May 2009


  • Collection system
  • Light emitting diode (LED) light source
  • Light engine
  • Pocket size projector


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