Restoration Of Linearly Smeared Transparencies

Photographic distortion caused by one-dimensional linear motion of the film during exposure is treated in this paper. The distortion (point spread)function is obtained by making a photographic record of the pulse shape. This data is in turn used by a digital computer to produce the Fourier transform of the point spread function. Optical spatial filtering of the distorted image with an inverse filter using a coherent, monochromatic optical processor has been used. Images which have been smeared by up to three times the minimum resolution length have been restored. The filtering technique consists of manipulating both the phase and amplitude of the distorted scene. In general, the theory of optimal filtering has considered additive noise in the form of signal-to-noise ratios. The signal-to-noise ratio has been treated by considering it as a constant or some function of the spatial frequency. In the latter case, improvement in both restoration and cosmetics was obtained. Film linearity of both the input and output imagery is controlled by processing the film over the linear portion of the Ta vs. E curve. MTF curves of the frequency response before and after filtering are presented. Theoretical error analysis was performed on the restored imagery and good agreement between theory and experiment was obtained.