Showing papers on "Phase correlation published in 1974"

Frame-to-frame coding of television pictures using two-dimensional Fourier transforms (Corresp.)

Abstract: Two systems are described for reducing the data rate required to transmit TV signals. Basic to the operation of both systems is the fact that if there is an object in the scene moving more or less in linear translation, then the two-dimensional frame-difference signal computed during the present frame will be very similar to the frame-difference signal which was computed during the previous frame except for a linear translation. Thus the Fourier transform of the frame-difference signal will also be similar during successive frames except for a linear phase shift.

Motion detection employing direct Fourier transforms of images

Abstract: 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.

Sequency Domain Design of Frequency Filters

Abstract: Each discrete transform has its advantages over other transforms. Fourier domain filters are easier to design than Walsh domain filters. But Walsh transforms can be computed much faster than Fourier transforms. This paper considers the problem of designing a Walsh domain filter, given a Fourier domain filter. Same procedure can be applied to other transforms. Given a Slant filter its equivalent Fourier filter or Walsh ifiter can be found.

The use of symmetry with the fast Fourier algorithm

Abstract: This paper presents an algorithm for making use of symmetry in the fast Fourier transform in a simple and general way which is applicable to nearly all space groups. This allows one to reduce storage requirements to approximately what is needed for an asymmetric unit of the electron-density function, and hence makes possible economical forward and reverse transforms of large unit cells in core.

On the response of arbitrary finite order and its relation to imaginary-time correlation functions

Abstract: The Nth-order response, effected by an external scalar field coupled to a system initially in thermodynamic equilibrium, is expressed with the help of imaginary-time correlation function using the spectral representation of its Fourier coefficients.