LED Metrology n LED spatial intensity distribution measurement

LED Metrology n LED spatial intensity distribution measurement research

LED’s in present-day industry products n n LED’s for its optical parameters have a set of unique features and can’t be compared with traditional lamp bulbs Because of large uncertainties are currently involved transfer from using lamp bulbs to LED’s is not a trivial task

LED radiation spatial intensity distribution n LED is not a point source, that’s why there are some difficulties appears during radiant intensity measurement Radiant intensity changes with the distance from LED to detector Publication CIE 127 recommends to use a new term “averaged light intensity”

LED radiant intensity model for approximate analysis

LED radiation spatial intensity distribution measurement instrument n Design of goniometric instrument provide measurement in half sphere (solid angle 2π sr)

LED radiation spatial intensity distribution measurement instrument

Instrument software n n Measurement result presented as 3 D diagram Measurement data are saved in xml text file Measurement is fully automated and don’t need any user participation. User have some set of options for measurement accuracy adjustment

LEDs measurement instrument photos (made by chapter member)

Measurement uncertainties n n LED radiation properties changes with forward current and temperature. Some little current fluctuations cause large result uncertainties Detector SNR and ADC error provide additional uncertainty for result Errors in LED positioning during measurement give an uncertainty that changes with signal derivative in diagram region LED angle value is the main factor that doesn't allow to receive equally precise results for different LEDs