On the basis of knowing the relative energy distribution of spectrum of light source, the irradiance measuring principle is described.

This apparatus is a multifunction spectrum testing set-up, which suits to measure for infrared detectors the wide range spectral sensitivity and also the distribution of spectral energy.

Requirements on the shape, duration, distribution in pulse shape and spectral compositions of ultrashort laser pulses in the development of picosecond image tube cameras are briefly described.