Raytheon Company

William Hale Wellman

Lee M Savage

Mary Morabito O'Neill

Eric J Gudim

Joseph F Borchard

Douglas W Anderson

Mary Dominique O'Neill

Gregory K Pierce

Michael Aidan Gritz

John T Broad

Rafael Hernandez

Charles R Stallard

Aldon L Bregante

Rao S Ravuri

A method for improving geolocation accuracy in a passive radar warning receiver, using synchronized data curve-fit and interpolation to asynchronous and noisy receiver and navigation measurements over observation periods that are extended to reduce inaccuracies caused by noise. The present disclosure yields synchronized data samples at intervals short enough that constant-rate equations are valid, even though the actual motions over the observation interval may be more complex and have higher-order dynamics. It reduces noise, synchronizes data samples, and is readily adapted to motions with variable acceleration. The method generates rate samples short enough to satisfy constant rate assumptions, yet fit data over intervals long enough to enhances measurement accuracy by reducing measurement noise.

Geolocating a remote emitter

Methods and apparatus for determining an angle of arrival in a radar warning system that uses tracking to provide a more accurate angle of arrival than conventional systems. In exemplary embodiments, angle of arrival and range are mapped from measured body angles to a 3D coordinate system where modern tracking techniques are applied to improve accuracy and stabilization of measurements, then mapped back into body angles for display.

Methods and apparatus for determining angle of arrival (AOA) in a radar warning receiver

Several types of noise limit the performance of remote sensing systems, e.g., systems that determine the location, color, or shape of remote objects. When noise detected by sensors of the remote sensing systems is known and well estimated, a Kalman filter can converge on an accurate value without noise. However, non-Gaussian noise bursts can cause the Kalman filter to diverge from an accurate value. Current approaches arbitrarily boost noise with fixed additive or multiplicative factors, which slows filter response and often fails to give timely results. Such noise boosts prevent divergence due to badly corrupted measurements. Disclosed embodiments eliminate a subset of noise measurements having the largest errors from a data set of noise measurements and process the remaining data through the Kalman filter. Advantageously, disclosed embodiments enable a Kalman filter to converge on an accurate value without the introduction of noise boost estimates.

Iterative Kalman filtering

Accurate remote tracking of fixed objects from a moving platform requires overcoming platform noise. Such tracking becomes difficult when the only inertial reference (such as a central aircraft inertial navigation system) is remote from the sensor, which experiences non-measured angular movements due to airframe vibrations and flexing. In such a scenario, Kalman filtering cannot converge on a true value because all noise sources are not known. Current na&#xef;ve approaches arbitrarily boost noise with fixed additive or multiplicative factors. However, such approaches slow filter response and; thus, often fail to give timely results. Embodiments of the present disclosure derive inertial reference parameters to quantify noise of the sensor that is remote from the inertial reference. Advantageously, disclosed embodiments enable use of remote sensors with an existing inertial reference, rather than consolidating sensors and the inertial reference at a single location or providing inertial references at each sensor.

Kalman filtering with indirect noise measurements

Various embodiments provide an optical alignment apparatus that includes a mirror structure having a plurality of mirrors, the mirror structure being configured for mounting a lens. The plurality of mirrors are arranged so as to redirect a collimated beam of radiation into the lens at different angles so as to measure one or more alignment parameter of the lens.

Method and apparatus for multiple field-angle optical alignment testing

A monolithic body () has a compound optical surface that defines a centrally located lens element (B) that is transmissive to light having wavelengths of interest, such as infrared radiation (IR), and a reflector (B) disposed about the lens element that is reflective to the light. The monolithic body is comprised of a material selected for fabricating a refractive lens element. The compound optical surface has a centrally located portion defining the lens element surrounded by a generally curved surface region having a reflective coating that defines the reflector. The centrally located portion may be coated with an anti-reflection coating. The compound optical surface is preferably formed in one operation, such as one that uses a diamond point turning operation.

Monolithic lens/reflector optical component

An imaging sensor system includes an optics system that images a point feature of a scene at an image plane with a blur-circle image having a blur diameter, and a detector array at the image plane. Special array patterns and signal detector logic are used to improve the accuracy of the determination of the object location. In one form, the detector array is a one-dimensional detector array comprising a plurality of detector subelements each having a width of from about &#xbd; to about 5 blur diameters, and a length of n blur diameters. Each detector subelement overlaps each of two adjacent detector subelements along their lengths. An overlap of each of the two adjacent detector subelements is m blur diameters, and a center-to-center spacing of each of the two adjacent detector subelements is nblur diameters. The value of n is equal to about 3m, and the value of m is equal to about n/2. In another form, the detector is a two-dimensional detector array of detector subelements. The detector subelements are sized and staggered such that an area of the blur-circle image may not simultaneously be split equally among four detector subelements.

Imaging sensor system with staggered arrangement of imaging detector subelements, and method for locating a position of a feature in a scene

An infrared sensor element having an antenna coupled directly into a rectifier. Infrared radiation impinging the antenna induces an alternating current. The rectifier converts the alternating current into a rectified signal. The rectified signal corresponds to a magnitude of the incident infrared radiation impinging the antenna, and can be used for detection and imaging operations. Coupling the antenna directly into the rectifier eliminates the need for a photodetector. The wavelength of sensor elements can be separately tuned. A sensor made up of a plurality of such sensor elements can operate in a time-division multiplexed mode sensing different infrared bandwidths in separate time segments. Two or more sensors each made up of a plurality of sensor elements can be co-located in a single focal plane and operated separately to detect infrared radiation in different bandwidths. A sensor element can also operate in bandwidths other than infrared.

Antenna-coupled-into-rectifier infrared sensor elements and infrared sensors

An object such as an aircraft in flight is obscured from infrared detection when viewed from an external viewing location. The method includes providing the object having an externally viewable hot region associated therewith, wherein the hot region has a temperature greater than 150&#xb0; C. A source of an obscuring agent is provided, wherein the obscuring agent comprises a mixture of carbon dioxide gas and water vapor. The obscuring agent is ejected from a dispensing location so as to flow between the hot region and the external viewing location. The obscuring agent has a temperature of less than that of the hot region.

Obscuration method for reducing the infrared signature of an object

A position of a feature in a scene is located by forming an image of the feature using a segmented array having a plurality of array subelements. Each of the array subelements has an output signal. The output signals from at least two spatially adjacent array subelements are cooperatively analyzed to establish a data set reflective of an extent to which output signals responsive to the image of the feature are produced from exactly one or from more than one of the adjacent array subelements. The data set is used to reach a conclusion as to a location of the image of the feature on the segmented array. Increased positional accuracy is attained with no loss of sensitivity.

Method for analyzing output data of array subelements of an imaging segmented array

A wide-angle IR imaging system (A) has an entrance aperture () for admitting IR from a scene and a dewar (A) that contains a coldshield () that encloses a cooled IR detector () disposed at an image plane (A). The dewar includes a dewar window (), and an optical axis of the IR imaging system passes through the dewar window and the image plane. The IR imaging system further includes a plurality of uncooled optical elements () disposed along the optical axis between the entrance aperture and the dewar window, and a plurality of generally annular reflector segments (A,B) disposed around the optical axis between the dewar window and the entrance aperture. Each of the reflector segments has a reflective surface that faces the dewar window. An opening through an outermost reflector segment furthest from the dewar window defines an effective cooled aperture stop, or warm stop (A) of the IR imaging system, and at least one of the optical elements () is disposed between the effective cooled aperture stop and another one of the reflector segments (A) that is located nearer to the dewar window. In the preferred embodiment the at least one optical element, and the reflector segment that is located nearer to the dewar window, are comprised of a single monolithic body () that has a compound optical surface.

Optical system for a wide field of view staring infrared sensor having improved optical symmetry

A window mounting system for optical sensors including a removable connection for window replacement, an alignment system to assure precision registration of the window or dome with the sensor internal optics, and thermal insulation to limit heat transfer from the window to the optics housing and sensor. The removable connection maintains precise optical alignment of curved domes with significant optical power, yet also is effective with simple flat windows.

Window mounting for optical sensor

Sensing in an elevated-temperature environment is provided using a sensor system having a sensor housing with an exterior wall with a window-support region having an outwardly facing external face, and a window through the window-support region of the exterior wall and affixed to the exterior wall. A sensor unit contained within the sensor housing receives an input signal through the window. A thermal-insulation layer is on the external face of the window-support region of the exterior wall at a location immediately adjacent to the window. The sensor system is operated in an environment wherein the window-support region of the exterior wall is heated to a temperature of greater than about 100&#xb0; C. in the event that no thermal-insulation layer is present. In a typical application, the sensor system is attached to an aircraft such that the external face is in a forward-facing orientation, and the aircraft is operated such that the external face is heated by aerodynamic heating.

Sensor system and method for sensing in an elevated-temperature environment, with protection against external heating

A sensor system for viewing the light energy of a scene has an imaging detector which converts incident light energy into an electrical signal. Two colors are separately imaged by the detector in two imaging regions. The imaging system for each color includes a color filter positioned between the scene and the respective region of the detector, an optical train that focuses filtered color scene energy, and an optical fiber bundle having an input end that receives the respective color scene energy from the optical train and an output end that directs the color scene energy onto the respective region of the detector using a nonlinear mapping. The optical fiber bundle is formed of a plurality of optical fibers wherein each of the optical fibers has an input shape and size at its input end and an output shape and size at its output end. The output shape and size are different from the input shape and size. The sensor system further includes an electronic device operable to read the electrical signal of the detector, and image-processing electronics.

Multicolor staring missile sensor system

A method and system of time-to-intercept determination for a radiation source using passively-sensed irradiance data. The invention provides a plurality of noise reduction features to reduce the noise present in the data and improve the accuracy of the time-to-intercept computation. The method includes reducing data noise by defining an acceptable noise level and eliminating any excessively noisy data from the time-to-intercept computation. The method further includes constantly updating the time-to-intercept computation by using irradiance values that are advanced in time. Other features of the present invention includes averaging of irradiance values over a time interval, filtering of the irradiance data received by the method, and triggering at a predetermined time-to-intercept. The invention also includes a time-to-intercept system and processor implementing the above method.

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Santa Barbara, CA, United States of America

William Hale Wellman