Patent US 4,063,281

Method and apparatus for directly converting between an image and the spatial or temporal Fourier transform thereof. To convert an image into its Fourier transform representation, the image interacts with strain waves in media that have electrical properties varying as a function of both the intensity pattern of the image and strain waves in the media. The electrical properties are measured to derive signals representing Fourier series terms defining the image. The derived signals are used to detect motion (including motion in the plane of the image), for image stabilization and scaling, and for pattern recognition. A new DEFT device (Direct Electronic Fourier Transform) obtains a Fourier transform representation of an image by utilizing photon assisted tunnelling current through an isolator film junction between two thin conductor films. Another new DEFT device provides spatial scanning similar to television raster scanning but utilizing completely different principles. Still another new DEFT device generates a two-dimensional spatial Fourier transform representation of an image without the need for two-dimensional scanning of the strain wave. An image is reconstructed from electrical signals obtained as described above by interacting uniform (but not necessarily coherent) light with strain waves that are a function of these electrical signals.