- The optical transfer function (OTF) for image degradation by nonharmonic vibrations is analyzed. Previous analyses of vibration image degradation were restricted to sinusoidal vibrations only or to general vibrations determined by the displacement function. However, most of the real-life vibrations are nonharmonic and in general are determined only by the power density spectrum envelope. We present a method to calculate the OTF or the expected OTF for any high-frequency vibration determined by its power spectral density. The calculation method is practical for analysis and design of imaging systems that are subject to real-life vibrations and for use in restoration of vibrated images.