USA As Represented by Secretary of the Navy

United States of America As Represented by the Secretary of the Air Force

Philip Morris Inc.

E.i. Dupont De Nemours and Company

US Government As Represented by the Secretary of the Army

David P Casasent

Demetri Psaltis

Charles F Hester

Roeland M Hekker

Izhak M Livny

Gregory S Mercurio

Marc A Franke

The Fourier transform optical processing system of the present invention includes generating an electrical signal in response to a first image and modulating a beam of coherent light with means that is responsive to the electrical signal. A Fourier transform image of the modulated coherent light beam is formed, an then detected. The detector provides a second electrical signal representative of the Fourier transformed image. Other aspects of the invention include comparing the second electrical signal to a reference electrical signal for producing an output signal representing any differences; optically preprocessing the image; detecting the Fourier transform image and generating signals representative of its Fourier transform characteristics; and modulating a coherent light beam using a liquid crystal or other spatial light modulating device.

Transform optical processing system

Lines of text (e.g., printing on a product) are verified by forming a one-dimensional image of each line substantially parallel to its length. This one-dimensional image information is compared to corresponding information for the intended lines of text. This comparison is preferably done using acousto-optic correlator systems. Space and frequency multiplexing may be used to allow parallel processing of several lines of text and/or to allow comparisons with multiple references to be made simultaneously. The invention may be used to determine the acceptability of products based on the correctness of the text image, and to reject products on which the correct text does not appear.

Methods and apparatus for optical product inspection

Products having optically detectable straight line segments are inspected for acceptability by forming one or more one-dimensional images of the product in which properly aligned straight line segments are respectively focused to points in the image. Such parameters as the location and image intensity of these one-dimensional image points are used to determine whether or not the product is acceptable. An optical Hough transform underlies these product inspection techniques.

A method of recognizing different perspective views or images (i.e., multivariant views) of the same object (i.e., intraclass patterns). Each intraclass pattern, or different representation of the same object, is described as an orthonormal basis function expansion, and a single averaged matched spatial filter is produced from a weighted linear combination of these functions. The method eliminates the multiple matched spatial filters, and the extensive postprocessing of the matrix output from a multichannel correlator, which are used in the prior art.

Method of multivariant intraclass pattern recognition

A multiple-invariant, space variant optical processor in which two functions described by any number of separate distortion parameters can be correlated with no loss in signal-to-noise ratio of the correlation. The unknown distortion parameters can also be determined in this scheme. Experimental confirmation of the key step, determination of the non-linear phase portion of a complex optical transform can be provided.

Multiple-invariant space-variant optical processing

A correlation method and apparatus for electrical signal transmission and ception of coded waveforms are disclosed which makes use of a coordinate transformation of the original waveform prior to transmission, effecting an inverse coordinate transformation upon reception and then correlating the resultant waveform with the original waveform. More particularly, the coordinate transformation and its inverse comprises a non-linear transformation preferably of the logarithmic type which when utilized in an electro-optical signal processor of a radar system, for example, provides Doppler invariant output data, as well as additional noise immunity.

Space variant signal processor

A method and apparatus for determining the value of a Doppler frequency shift component .DELTA.f present in a signal f .+-. .DELTA.f employing a correlation process which utilizes the Mellin transform and is scale invariant. The location of the correlation peak in the reference coordinate system used provides a measure of the magnitude of .DELTA.f. The sequence of steps involved in the correlation process when optical apparatus is used include forming a transmittance pattern of the signal f .+-. .DELTA.f, which has a horizontal scale that is the natural log of the time scale of the original signal, forming a similarly scaled transmittance pattern of the reference signal, f, and utilizing the first patttern in the input plane of a frequency plane correlator that has a holographic matched spatial filter that is produced from the second pattern and contains a term corresponding to the conjugate of the Mellin transform of the reference signal in its frequency plane.

Doppler processing method and apparatus

A method and electro-optical apparatus for correlating two functions, f.sub.1 (x,y) and f.sub.2 (x,y) which are shifted, scaled and rotated versions of each other without loss of signal-to-noise and signal-to-clutter ratios as compared to the autocorrelation case. The coordinates of two correlation peaks provide an indication of the scale and orientation differences between the two functions. In performing the method, the magnitudes of the Fourier transforms of the functions are obtained, .vertline.F.sub.1 (.omega..sub.x, .omega..sub.y).vertline. and .vertline.F.sub.2 (.omega..sub.x,.omega..sub.y).vertline. and then a polar coordinate conversion is performed, and the resultant functions F.sub.1 (r,.theta.) and F.sub.2 (r,.theta.) are logarithmically scaled in the r coordinate. The functions thus produced F.sub.1 (e.sup..rho.,.theta.) and F.sub.2 (e.sup..rho.,.theta.) are Fourier transformed to produce the Mellin transforms M.sub.1 (.omega..sub..rho., .omega..sub..theta.) and M.sub.2 (.omega..sub..rho.,.omega..sub..theta.). The conjugate of one of these Mellin transforms is obtained, and the product of this conjugate with the other Mellin transform is produced and, subsequently, Fourier transformed to complete the correlation process.

Positional, rotational and scale invariant optical correlation method

Correlation methods and apparatus are disclosed which make use of Mellin transforms that are scale and shift invariant. There is no loss in the signal-to-noise ratio of the correlation, and data is available for determining any scale difference between the input and reference data.

Correlation methods and apparatus utilizing mellin transforms

A real-time radar processor utilizing a coherent optical system for provig target fine range and Doppler/azimuth angle data with increased signal-to-noise and signal-to-clutter ratios. Radar signals detected by a linear phased array or successive echo signals detected by the receiver are arranged in a 2-D input format for parallel processing in a multi-channel 1-D optical correlator. Target range and azimuth angle reference data may be stored in a matched spatial filter hologram or recorded in a 2-D format similar to that of the detected radar signals according to which of three different correlation configurations are employed in the optical system. The coordinates of the correlation peak in the output plane of the correlator are proportional to the target's fine range and Doppler/azimuth angle, depending upon the type of radar signals being processed.

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Pittsburgh, PA, United States of America

David P Casasent