Hughes Aircraft Company

Raytheon Company

Mark J Rehfield

Gerard L Rafanelli

Susan B Mount

Eric B Jensen

Brent L Ellerbroek

Stephen K Johnson

Marilyn A Sperka

A spinning strip aperture imaging radiometer sensor system and data processing methods for detecting moving objects derived from a plurality of image frames acquired by a strip aperture imaging sensor. A moving object in any individual image frame results in a motion smear signature in the total synthesized image. The motion smear signature is processed to detect the moving objects. One embodiment of the system comprises a rotating strip aperture telescope, a two dimensional detector array that detects images in the telescope's focal plane, a rotation compensation device that prevents rotational smear during integration time of detectors of the array, a signal processor that records a plurality of image frames of a scene imaged by the telescope as it rotates around its optical axis, and that implements method(s) for detecting the moving objects present in the recorded images. A hierarchy of moving object detection processors and methods,is disclosed that includes spatial, temporal, spatial frequency, and temporal frequency domain detection processors, and is compatible with multi-spectral background rejection techniques. Selection of the appropriate processing procedure and method depends upon the scenario, and the effective signal to noise ratio characteristics of the moving object.

Moving object and transient event detection using rotation strip aperture image measurements

An extended scene wavefront sensing apparatus and procedure that separates (deconvolves) scene effects from wavefront errors of an optical or similar system. The present wavefront sensing apparatus and procedure uses a point source wavefront slope sensor in scene scanning mode and estimates wavefront errors by using a cross-correlation or cross-coherence procedure that operates on the outputs of the point source wavefront slope sensor. A signal processing procedure employed by the point source wavefront slope sensor provides output signals corresponding to wavefront slopes at forward optics pupil locations geometrically projected to the location of the transmission and reflection measurement plane detector pairs. During the scanning process, each of the detector pairs (equivalent to a subaperture) measures the effects of the local unchanging wavefront error in the forward optical system and temporal variations due to the scanning scene. By cross correlating or cross-cohering each detector pair's temporal difference with differences from selected reference detector pairs, the scene induced variations in the measurement are eliminated, thereby leaving the stationary wavefront error component of the measurement. The lead/lag time in the temporal differences output between detector pairs and reference detector pairs are then used to estimate the wavefront slope differences between equivalent subapertures. The wavefront slope differences are used in a reconstructor to generate wavefront errors or wavefront slope errors, except for an unobservable global tilt.

Wavefront error estimation derived from observation of arbitrary unknown

A spinning strip aperture imaging radiometer sensor system and data processing method that is capable of synthesizing full circular aperture images from a plurality of image frames acquired by the strip aperture imaging sensor. One embodiment of the imaging system comprises a rotating strip aperture wide field of view telescope, a two dimensional detector array used to detect images in the telescope's focal plane, a rotation compensation device used to prevent rotational smear during the integration time of the detectors, a signal processor used to record a plurality of image frames of a target scene that is imaged by the telescope as it rotates around its optical axis, and a signal processor and method used to synthesize the full circular aperture image from the recorded images. The operation of the full aperture image synthesis method hinges upon the ability of the rotating strip aperture to measure all of the spatial frequencies contained in a full circular aperture image measurement. Having knowledge of the strip apertures' spatial frequency passband, and the temporal registrations of each of the recorded strip aperture images permits synthesis of the full aperture image by the sensor system and image synthesis method. Image synthesis may be accomplished in the spatial or spatial frequency domains. General and illustrative examples of the image synthesis procedure and first order noise performance predictions are described. A general form of the invention utilizes two dimensional spatial frequency information to greatly reduce the line of sight stability requirements of the telescope.

Full aperture image synthesis using rotating strip aperture image

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Rancho Palos Verdes, CA, United States of America

Mark J Rehfield