Westinghouse Electric Corporation

Northrop Grumman Systems Corporation

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

Martin G Woolfson

John G Romanski

David W Coffey

Scott A Imhoff

Floyd C Bentley

Giora A Bendor

Martin M Morici

James R Brinsley

Guy W Cheesman, Iii

Robert H Plath

The time separation of laser pulses comprised of a relatively fixed reference pulse and a time varying doublet pulse in a doublet pulse laser radar is linearly modulated for eliminating velocity ambiguity upon reception and detection. A range-Doppler map can be directly generated which not only reveals target range and velocity, but also can be processed to indicate target motion, such as rotation.

Time modulated doublet coherent laser radar

A 'bang-bang', i.e. digital tracking system for a remote laser designated target having position, rate and acceleration errors. The system is responsive to the sign of the error signal (up/down, right/left) in relation to boresight as opposed to the amplitude of the received signal output from an optical quadrature detector to determine the occurrence of two consecutive zero crossings of boresight following a system gain change where there is a change in sign for consecutive signal detections and as a result thereof reduces the size or amplitude of the digital control step which is utilized to determine the limit cycle of the oscillation of the tracker's optics. Additionally, an estimate of the velocity error is determined from the number of signal detections between successive zero crossings, i.e. from up to down, or vice versa, and left to right, or vice versa and summed with the control step to provide a composite tracking error signal which is applied to a gimbal drive mechanism controlling the tracker optics.

Bang-bang laser spot tracker

A classifier employing general frame wavelets for improving target recognition while decreasing computational intensity is disclosed. A wavelet selection means compares a portion of a time dependent input signal from a receiver with a set of sample wavelets, each wavelet being bandpass limited, locally supported, and mean zero, and selects a prototype wavelet resembling the input portion. A resolving means expands the prototype wavelet onto a basis of wavelet functions having variations in scale and delay, and resolves the input signal onto the basis of functions. A regionpass filter identifies a region from a grid of resolved coefficients that contains features of a target from the input signal and discards coefficients outside the region. A separability filter passes select coefficients from a scale band within the identified region where separability among known targets is high. A comparator compares the selected coefficients with an exemplar of known targets to indicate a recognition of the target.

General frame wavelet classifier

A video signal preprocessor for discriminating a target image from background in the video frame signals generated by an electro-optical sensor electrically representing the field of view thereof is disclosed. A predetermined portion of each video frame signal is selected and divided into a predetermined number of elements. Each element is assigned a gray level value from a plurality of discrete gray level values as a measure of video intensity. A discriminant function of gray level values is formed from the video data of an initial video frame signal based on the number of elements assigned to each discrete gray level value. Elements which have assigned gray level values corresponding to those of the formed discriminant function are then selected from the video frame signals subsequent to the initial one and may represent a substantial image of the target. Further preprocessing may be performed by categorizing the gray level values of the discriminant function into a set of discrete modes. A signal representative of the velocity of the group of elements having gray levels corresponding to each mode is generated for each mode of the set of modes. A target set of modes is identified from the set of modes based on the generated velocity signals and a predetermined velocity signal representative of the background velocity. Only elements which have assigned gray levels corresponding to the target set of modes are selected from the video frame signals to represent a target image.

Apparatus and method for preprocessing video frame signals

A binary correlation video tracker and a video preprocessor included therein, which function cooperatively to form binary patterns of values for the picture elements (pixels) in a predetermined pixel array of each of a plurality of frames of video gray level information generated by an electro-optical sensor, is disclosed. Histograms are formed for selected pixel arrays in the predetermined array of a video frame in accordance with a set of predetermined gray level values. The formed histograms are combined in accordance with a discriminant function to form a composite histogram from which at least one gray level value of the set is selected. Those pixels of the predetermined array which have gray level values corresponding to the selected at least one gray level value are assigned one of two predetermined values, the other pixels being assigned the other of the two predetermined values, whereby a binary pattern of values for the predetermined pixel array is formed. Accordingly, the video tracker selects a reference binary pattern of pixels from the formed binary pattern of the predetermined pixel array of one video frame. The selected reference binary pattern is used for performing auto and cross-correlation operations in the video tracker in accordance with a binary correlation coefficient function. In the cross-correlations, another reference binary pattern of pixels and position thereof in the predetermined array is derived for each of the video frames generated subsequent the one video frame, the results being used in the computation of tracking errors in the video tracker. In the auto correlations, a maximum autocorrelation value is derived for use in determining when the reference binary pattern may be updated with the another reference binary pattern for further binary correlation processing.

Binary correlation video tracker

In an electro-optical (E-O) system, the reference axis of a beam of light emitted from a light source is aligned colinear with the boresight image axis and the combined images with their colinear axes spatially fixed are guided to the field of view of an electro-optical sensor which is operative to generate sequentially frames of electrical information in a raster scan format representative of the field of view. The light source of the system is controlled to effect a predetermined time pattern of light beam image intensity variations as sensed by the electro-optical sensor. A position of the sensed light beam image in the generated frame of electrical information is detected in accordance with the predetermined time pattern intensity variation thereof. A positional relationship of the detected image position with respect to the predetermined frame reference position is established for the generated frame information of the electro-optical sensor. The raster scanned field of view is adjusted in the generated frames of electrical information as a function of the established positional relationship to converge the detected position of the sensed light beam image to the predetermined frame reference position, preferably centered within the generated frames of electrical information. Since the light beam axis and boresight axis are spatially fixed colinear by the optical elements of the system, the boresight axis is rendered substantially at the predetermined frame reference position in the generated frames of electrical information.

Autoboresighting electro-optical system

In an area correlation video tracker, a reference subarray of picture elements acquired from a selected track window array of picture elements of an acquisition video frame is cross-correlated in accordance with a predetermined metric function with the picture elements of the selected track window array of each of a number of video frames generated subsequent the acquisition video frame. From these cross-correlations, a minimum cross-correlation value is derived and a subarray of picture elements associated therewith is identified in the track window array of the subsequently generated video frames. An adaptive threshold processor performs autocorrelations in accordance with the predetermined metric function with the video information of the acquisition frame to derive a reference threshold correlation value and with the video information of each of the number of subsequently generated frames to correspondingly derive another threshold correlation value each. An update condition is rendered in the video frame having a derived one cross-correlation value greater than the reference threshold correlation value. The update condition causes the values of the picture elements of the reference subarray to be replaced with the values of the picture elements of the identified subarray corresponding to the one cross-correlation value and causes the reference threshold correlation value to take on the value of the another threshold correlation value derived in the video frame associated with the one cross-correlation value, whereby subsequent cross-correlations will be performed with the updated values until another update condition is rendered.

Adaptive updating processor for use in an area correlation video tracker

A video tracker for controlling the scanning of a sensor in an electro-optical tracking system in which the track point for the sensor is determined by balancing a volume signal from a first half of the track window with a volume signal from the second half of the track window in both horizontal and vertical directions of the track window to provide azimuth and elevation error signals. The volume signal for each half of the track window is determined by the product of the area of the corresponding half of the track window and the amplitude of the average linear video signal within that portion of the track window. Further, a multiplexed, time domain multiplier compares the gain of the azimuth and elevation error signals in successive fields of the sensor to normalize the gain of the azimuth and elevation error signals with respect to the displacement of the volumetric centroid of the target from the center of the track window.

Volumetric balance video tracker

An amplitude control apparatus utilizing an oscillator with an amplitude regulation loop to provide positive feedback to the oscillator and thereby providing zero amplitude error.

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Baltimore, MD, United States of America

Martin G Woolfson