Determining the spectral responsivity from relative measurements by using multicolor light-emitting diodes as probing light sources

We measured the ratio of the photocurrent generating from a detector under test to that from a reference one when they were irradiated by the same light-emitting diodes (LED) in the same configuration. We recorded data for various LEDs with their spectra covering different regions in the spectral response range of the test detector. If the spectral responsivity of the reference detector and LEDs’ lineshape functions had been predetermined, we can use a resolution-enhancement algorithm to reconstruct the spectral responsivity from multiple data measured by using multicolor LEDs as probing light sources. We have also successfully generalized the algorithm to the case with an arbitrary broad-band detector as the reference detector and found an alternative algorithm which leads to the same solution. After a suitable correcting step, the resulting spectral responsivity was found to be free from the broadening effect due to the finite bandwidth of LED and in good agreement with the one directly measured by using spectrally pure light as probing light.