An analysis of passing the light emission that has Gaussian spectrum through the polarization-optical scheme (POS) with half-wave phase plate has been performed. The results of theoretical calculations of the coherence length of the radiation as a function of the contrast of POS output intensities are obtained for the different widths ∆λ of the Gaussian emission spectrum. The research results of the contrast of POS with λ/2 phase plate are obtained for the following case: high-power leds radiation of red, green and blue spectrum; semiconductor laser red wavelengths; a second harmonic ND-laser (green wavelength range).