Abstract: A method of thickness measurements of thick petrochemical films on a water surface has includes irradiating a surface by an optical beam, receiving a reflected signal, analyzing the dependence of intensity of the reflected signal on a wavelength, determining a film thickness based on the analysis, using three wavelengths for irradiation of the surface, selecting the wavelengths from conditions n 2 ? ? 1 ? 2 = 2 ? n 2 ? ( ? 2 ) ? 2 , where n2 (?1) and n2(?2) are refraction coefficients of petrochemical product at the wavelengths: ?1 and ?2, ?3 is equal to a wavelength of absorption maximum of petrochemical product, and using for the determination of the film thickness results of the analysis of intensity of the reflected signal at the three wavelengths.

Abstract: A method of measuring a thickness of thin films has the steps of irradiating a surface by an optical beam, receiving a reflected signal, analyzing a dependence of the reflected signal on a wavelength, determining a film thickness based on the analysis, and using for the irradiation three wavelengths which are close to each other, the determining including determining the film thickness based on the analysis of intensity of the reflected signal at the three wavelengths.

Abstract: Detection of oil pollution on water surfaces includes providing echo signals obtained from optical radiation of a clean water area at two wavelengths, optically radiating an investigated water area at two wavelengths and obtaining echo signals from the optical radiation of the investigated water area at the two wavelengths, comparing the echo signals obtained from the radiation of the investigated area at two wavelengths with the echo signals obtained from the radiation of the clean water area, and based on the comparison, determining presence or absence of oil pollution in the investigated water area.