A new hardware modification of the spectral transparency method (STM) to estimate the particle size distribution function and particle concentration using a wide range of probe radiation wavelengths and applying high-speed video recording is suggested. Issues of solving the reverse problem of aerosol optics using a regularizing algorithm, the parameterization method, are identified. A new algorithm for solving the aerosol optics inverse problem is designed using direct search technology and employing, as measuring data, not absolute values of spectral attenuation coefficients but their relations for specified wavelengths. This effectuation of the STM enables measurement of disperse parameters of submicron aerosol fluxes, as well as to determine dispersivity of natural aerosols and those used in technological processes and of the condensed phase of combustion products from high-energy materials. A hardware-software system that implements the modified STM is developed.