Raytheon Company

Massachusetts Institute of Technology

Ratheon Company

Michael K Holz

Terry A Dorschner

Irl W Smith

Gary J Swanson

Brandon William Pillans

James R Leger

David L Corkum

Anthony J Ross

Nathan M Mintz

Gregory V Burnett

Anthony Ross

Brandon W Pillans

A system and computer-implemented method for detecting concealed cargo and/or concealed passengers in a vehicle includes obtaining weight distribution data for the vehicle; obtaining vehicle loading data; measuring a center of mass of the vehicle to obtain an actual center of mass position of the vehicle; and executing one or more computer program modules configured to determined a predicted center of mass position of the vehicle using the obtained vehicle loading data and the obtained weight distribution data of the vehicle; compare the actual center of mass position of the vehicle with the predicted center of mass position of the vehicle; and provide a signal if the actual center of mass position of the vehicle departs from the predicted center of mass position of the vehicle by at least a predetermined threshold, the signal being representative of concealed cargo and/or concealed passengers in the vehicle.

System and method for detection of concealed cargo in a vehicle by center of mass measurement

An electronically variable light attenuator and method for electronically attenuating light. The attenuator has an array of liquid crystal regions. The regions in a first set thereof are interspersed with the regions in a second set thereof. The array is adapted to receive a beam of light directed along an axis. A pair of electrodes is provided. At least one of the sets of regions is disposed between the electrodes. The regions in the first set are configured to produce a first diffraction pattern in response to the received light and the regions in the second set are configured to produce a second diffraction pattern in response to the received light. The pair of electrodes are arranged to enable the first and second diffraction patterns to combine with a degree of interference along an axis selected in accordance with an electric field produced between the pair of electrodes and through the at least one of the sets of regions. The array degree of interference is greatest in the absence of the electric field. With such an arrangement, a relatively low cost, high power, fail-safe, electronically variable light attenuator is provided.

Electronically variable light attenuator

A ring laser gyro uses a composition for the gain medium which optimizes the effect of the Fresnel-Fizeau drag on the output signal of the gyro. In one embodiment, a composition of the gain medium is used which produces no change in the Fresnel-Fizeau component of the output signal as the discharge current varies from a nominal amount. In another embodiment, a gain medium composition is used which eliminates the Fresnel-Fizeau component of the output signal at a predetermined level of discharge current.

Ring laser gyro

A ring laser gyro uses means for shaping the gas flow, which inevitably develops as a result of a DC discharge, to optimize the effect of the Fresnel-Fizeau drag on the output signal of the gyro. In one embodiment, a sufficient component of the gain medium flow is provided to produce a substantially constant Fresnel-Fizeau component of the output signal even in the presence of variations of the discharge current. In another embodiment, a sufficient component of gain medium flow is provided to substantially eliminate the Fresnel-Fizeau component of the output signal at a predetermined level of discharge current.

A laser mirror mounting arrangement for a laser formed within a laser body is shown. The mounting arrangement includes a mounting base mounted upon the laser body. A stem is attached to the mounting base to which, in turn, the laser mirror is mounted. The stem has a coefficient of thermal expansion selected to maintain the mirror in a fixed position. This is accomplished by permitting the stem to expand due to thermal expansion in one direction, while the laser body expands due to thermal expansion in the opposite direction.

Passive pathlength control mirror for laser

A technique for coherent aperture filling by amplitude phase exchange is described which suppresses the far field side lobes of an array of lasers. The power contained in these side lobes is transferred to the central lobe so that it contains greater than 90% of the total array power. This is achieved by a field transformation which generates from the uniform phase and varying amplitude distribution of the input array a varying phase modulation with nearly uniform, i.e., aperture filled, amplitude distribution in the output beam. Far-field grating lobes from the nonuniformity in phase are then suppressed by an additional phase correcting element matched to compensate the phase modulation. In a preferred embodiment, the field transformation element, including a single step binary phase shifter flanked by a pair of lenses in an a focal imaging configuration, is followed by a binary phase grating for phase compensation.

Coherent aperture filling of an array of lasers

A laser gyroscope is described having a ring resonator adapted to support a plurality of resonant transverse electric and magnetic field modes TEM.sub.qmn, wherein the longitudinal mode index q is a sequentially different integer for each mode and the transverse mode indices m and n are constant. The gain medium bandwidth is sufficient to simultaneously support at least two adjacent modes, such as TEM.sub.qmn and TEM.sub.(q+1)mn modes. Each mode is split into a set of four components having distinct frequencies, arranged in orthogonally polarized pairs, typically counter-propagating right-handed and left-handed circularly polarized. At least six components can resonate, arranged in three pairs of alternating polarization, two of the pairs from a first mode, for example TEM.sub.qmn, and the third pair formed from the first two components from a second mode, for example TEM.sub.(q+1)mn, with the frequency difference between counter-propagating components of such first pair synchronized to the frequency difference between components of such like polarized third pair, thus resulting in a common frequency difference for all similarly polarized pairs. A magnetic field is applied to the gain medium to equalize the frequency dispersion for each component pair. With such arrangement, pathlength control is not required and the mode components are free to drift in frequency as the pathlength changes. The circulating power is increased to reduce the laser gyro noise due to spontaneous emission.

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Newton Centre, MA, United States of America

Michael K Holz