A method for in-line quality control and monitoring for the determination of the thickness, optical properties, functional properties and quality of thin films of transparent inorganic and organic materials during their growth processes onto polymeric substrates, characterized by: (a) in-situ and real time fast multiple ellipsometric measurements taken simultaneously at 32 wavelengths in the energy region from Visible to Far Ultraviolet, 1.5-6.5 eV, where the transparent inorganic and organic materials exhibit their absorption peaks, (b) simultaneous ellipsometric measurement of at least 32 different wavelengths, that represent a pseudo-dielectric function spectra in Visible-Far Ultraviolet energy region, collected in short time in the range of ms using a Fast Multiwavelength Ellipsometer (FMWE) unit, that is adapted in a vacuum growth chamber, or in air, (c) parameterization and analysis of the measured pseudo-dielectric function with the use of a geometrical phase model, air/thin film(s)/polymeric substrate, for the calculation of the wavelength dependent optical parameters of each film using the modified Tauc-Lorentz model, thus providing the Penn gap E 0, energy gap Eg, refractive index n(E=0), the thickness and deposition rate of transparent thin films grown onto polymeric substrates, (d) calculation of the transparent oxides, nitrides and other inorganic and organic thin films stoichiometry x and composition through the Penn gap or mean gap Eo, and of the stoichiometry, composition and quality of thin films grown onto the polymeric substrates that are related to the refractive index n(E=0), (e) determination of the final functional properties of transparent thin films on polymeric substrates through the optical properties such as the Penn gap E 0, the energy gap Eg and the refractive index n(E=0). (a) in-situ and real time fast multiple ellipsometric measurements taken simultaneously at 32 wavelengths in the energy region from Visible to Far Ultraviolet, 1.5-6.5 eV, where the transparent inorganic and organic materials exhibit their absorption peaks, (b) simultaneous ellipsometric measurement of at least 32 different wavelengths, that represent a pseudo-dielectric function spectra in Visible-Far Ultraviolet energy region, collected in short time in the range of ms using a Fast Multiwavelength Ellipsometer (FMWE) unit, that is adapted in a vacuum growth chamber, or in air, (c) parameterization and analysis of the measured pseudo-dielectric function with the use of a geometrical phase model, air/thin film(s)/polymeric substrate, for the calculation of the wavelength dependent optical parameters of each film using the modified Tauc-Lorentz model, thus providing the Penn gap E 0, energy gap Eg, refractive index n(E=0), the thickness and deposition rate of transparent thin films grown onto polymeric substrates, (d) calculation of the transparent oxides, nitrides and other inorganic and organic thin films stoichiometry x and composition through the Penn gap or mean gap Eo, and of the stoichiometry, composition and quality of thin films grown onto the polymeric substrates that are related to the refractive index n(E=0), (e) determination of the final functional properties of transparent thin films on polymeric substrates through the optical properties such as the Penn gap E 0, the energy gap Eg and the refractive index n(E=0).