LED Light-Spectrum-Modulator as a dynamic laboratory light source

Halogen filament lamps are normally used for transmission or absorption measurements. They have a high Intensity in the red spectral range which decreases continuously towards the blue range reaching down to a factor of 1/100. This requires a highly dynamic spectrometer, particularly when the sample shows very high absorption in the blue region. Another way is the use of optical filters to smoothen the reference spectrum and reduce infrared radiation. The analytical considerations show that the problem can be reduced with LEDs. An LED Light-Spectrum-Modulator can produce almost arbitrary spectral distribution. It consists of 22 single-color LEDs with a peak wavelength spacing of 20 nm and with width at half maximum of 20 nm. For absorption or transmission measurements a continuous and almost equable spectrum can be generated. In addition the intensity of reference light sources can be raised in spectral range with high absorption and the infrared radiation can be prevented completely. This can increase the accuracy of the measurement enormously and thus reduces the requirements for the spectrometer.