A method of monitoring local nanometer-level deviations of the surfaces of large optical components (elements) from a given profile has been developed, scientifically validated, and experimentally confirmed. The method is based on an algorithm for calculating the objective function—the spectral density of a one-dimensional correlation function in a wide spectral range of spatial frequencies. Theoretical and experimental studies have been made of the nonexcluded systematic and random error components of determining the optimization parameter of the objective function being used—the rms deviation of the local deviations of the surfaces of large optical components from a given profile.