LED Metrology

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LED Metrology

• LED spatial intensity distribution measurement
  research

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LEDs in present-day industry products

• LEDs for its optical parameters have a set of
  unique features and cant be compared with
  traditional lamp bulbs
• Because of large uncertainties are currently
  involved transfer from using lamp bulbs to LEDs
  is not a trivial task

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LED radiation spatial intensity distribution

• LED is not a point source, thats 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

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LED radiant intensity model for approximate
analysis
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LED radiation spatial intensity distribution
measurement instrument

• Design of goniometric instrument provide
  measurement in half sphere (solid angle 2p sr)

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LED radiation spatial intensity distribution
measurement instrument
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Instrument software

• Measurement is fully automated and dont need any
  user participation.
• User have some set of options for measurement
  accuracy adjustment

• Measurement result presented as 3D diagram
• Measurement data are saved in xml text file

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LEDs measurement instrument photos(made by
chapter member)
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Measurement uncertainties

• 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