Transient measurement of light-emitting diode characteristic parameters for production lines

A new instrument has been developed for transient measurement of light-emitting diodes (LEDs), including photometric parameters, colorimetric parameters, and electrical parameters in a matter of milliseconds, by combining spectrometer with a human photopic vision detector and data acquisition card (DAQ). The instrument can provide communication interface for sorter to realize automatic sorting of measured LEDs samples. The light emitted from the measured LEDs, which are illuminated under pulse current operation condition, is captured by the spectrometer and the human photopic vision detector. The spectral power distributions of LEDs are recorded by spectrometer, and processed to provide colorimetric parameters. We employ two novel algorithms including look-up table method and curve fitting method to determine the dominant wavelength of LED. In combination with linear interpolation, the look-up table method can locate dominant wavelength with a resolution of 0.1 nm. A programmable constant current source/voltage source is designed for power supply to drive LED. The luminous intensity of LED can be derived by detecting the photocurrent of human photopic vision detector. We also describe the calibration of the human photopic vision detector. This calibration provides detector-specific correction factor that enables accurate extraction of luminous intensity of LED. The instrument has been used to measure and inspect the quality of packaging LED.