Abstract: A spatial filter adapted to increase the angular spread of non-conjugated energy in a beam and suppress this energy to improve the efficiency of a phase conjugate system. In the illustrative embodiment, the filter includes first and second lenses and an aberrator to increase the angular spread. In the specific embodiment, an opaque plate, with a pinhole aperture therethrough, is sandwiched between the lenses to suppress the non-conjugated energy. The aberrator may be implemented with an amplifier or other suitable mechanism. Likewise, the aperture may be replaced with a highly angle-selective thick Bragg grating or other suitable arrangement. A phase conjugate master oscillator/power amplifier laser architecture is also disclosed.

Abstract: An all-reflective optical system includes an all-reflective afocal module, an all-reflective imaging module and an all-reflective switching structure being operated to direct a light beam through the afocal module and the imaging module. A first position of the switching structure directs the light beam to enter the first optical end of the afocal module and exit the second optical end of the afocal module, and thereafter to enter the input optical end of the imaging module. A second position of the switching structure directs the light beam to enter the second optical end of the afocal module and exit the first optical end of the afocal module, and thereafter to enter the input optical end of the imaging module. A third position of the switching structure directs the light beam to enter the input optical end of the imaging module so that the light beam completely bypasses the afocal module.

Abstract: A readout system for receiving return signals originating from one or more energy pulses fired toward a scene. The system includes a first mechanism for detecting energy received from the scene and providing a first signal in response thereto. A second mechanism times a rising edge and a falling edge of a pulse contained in the first signal and provides a second signal in response thereto. In a specific embodiment, a third mechanism determines characteristics of the pulse based on the second signal, which include characteristics, such as pulse width, pulse intensity, and/or pulse centroid, sufficient to generate an image of the scene.

Abstract: A two-stage hybrid cryocooler includes a first-stage Stirling expander having a first-stage regenerator having a first-stage-regenerator inlet and a first-stage-regenerator outlet, and a second-stage pulse tube expander. The second-stage pulse tube expander includes a second-stage regenerator having a second-stage regenerator inlet in gaseous communication with the first-stage regenerator outlet, and a second-stage regenerator outlet, and a pulse tube having a pulse-tube inlet in gaseous communication with the second-stage regenerator outlet, and a pulse-tube outlet. The second-stage regenerator and the pulse tube together provide a first gas-flow path between the first-stage regenerator and the pulse-tube outlet. A pulse tube pressure drop structure has a pulse-tube-pressure-drop inlet in gaseous communication with the pulse-tube outlet, and a pulse-tube pressure-drop outlet, and a gas volume is in gaseous communication with the pulse-tube pressure-drop outlet.

Abstract: An imaging spectrometer includes an all-reflective objective module that receives an image input and produces an objective module output at an exit slit, and an all-reflective collimating-and-imaging module that receives the objective module output as an objective-end input and produces a collimating-end output, wherein the collimating-and-imaging module comprises a reflective triplet. A dispersive element receives the collimating-end output and produces a dispersive-end input into the collimating-and-imaging module that is reflected through the collimating-and-imaging module to produce a spectral-image-end output. An imaging detector receives the spectral-image-end output of the collimating-and-imaging module. The objective module may be a three-mirror anastigmat having an integral corrector mirror therein, or an all-reflective, relayed optical system comprising a set of five powered mirrors whose powers sum to substantially zero.

Abstract: A system and method for combining a predetermined number of laser beams. The system (30) includes a collimating lens (34) for receiving and collimating the laser beams and a holographic device (36) positioned to receive beams from the collimating lens (34) and output beams which are co-aligned. The holographic device (36) includes a predetermined number of holographic optical elements (46, 48, 50), wherein each holographic optical element (46, 48, 50) is designed for a particular wavelength of the laser beams. In the preferred embodiment, the holographic optical elements are volume holograms, and the system further includes a blazed grating (38) positioned between the collimating lens (34) and the holographic device (36) to account for variations in the wavelengths of the laser beams due to environmental conditions.

Abstract: A radar processor is disclosed for processing the radar return samples from a Doppler radar receiver to discriminate helicopter targets from fixed-wing targets. The radar processor defines the spectral components of the radar return components due to the helicopter rotor hub as the “signal” component; and the spectral components due to the target skin, ground clutter and white noise as the “noise” component. The radar processor implements the Neyman Pearson criterion to calculate a detection statistic. Whether the calculated detection statistic exceeds a threshold determines whether a “helicopter presents” or a “helicopter absent” target condition is declared. The radar processor utilizes helicopter rotor hub reflected signals, and requires only a few milliseconds on target, and may therefore be readily implemented by scanning surveillance systems.

Abstract: A low power GPS tracking system. The novel system includes a first circuit adapted to collect samples of a signal for a first predetermined length of time and in accordance therewith generate an output signal, and a second circuit for cyclically powering on the first circuit for the first predetermined length of time and powering off the first circuit, or a portion thereof, for a second predetermined length of time. In an illustrative embodiment, the first circuit includes a receiver adapted to receive a GPS signal and output GPS data samples, and a processor adapted to calculate a navigation solution from the GPS data samples using an integrate and dump signal processing technique.

Abstract: A two-stage cryocooler (10) includes an ambient temperature portion (12), a first-stage temperature portion (14), and a second-stage temperature portion (16). The ambient temperature portion includes a surge volume (44) that is coupled to and in communication with the first-stage temperature portion. The surge volume may be coupled to a first-stage interface (36) of the first-stage temperature portion by use of an inertance tube (42). Locating the surge volume in the ambient temperature portion may advantageously reduce size and mass of the first-stage temperature portion. Also, thermal losses may be reduced by maintaining the surge volume at ambient temperature. Space and structural requirements for maintaining the system may be met more easily with the surge volume maintained in the ambient temperature portion of the two-stage cooler. The surge volume may be a separate unit, or may be a plenum or other chamber within an expander in the ambient temperature portion.

Abstract: A wide field of view imaging system (100). The novel system (100) includes a rotating mirror (18) having two reflective surfaces each surface, respectively, reflecting light from a scene to first and second sensors (10, 12) positioned to receive light from the mirror (18), wherein the first and second sensors (10, 12) each occupy a different portion of the volume surrounding the mirror (18). In the illustrative embodiment, the mirror (18) is a flat, double-sided mirror rotating at a constant velocity about an axis parallel with the surface of the mirror (18). The first and second sensors (10, 12) are all-reflective optical systems, with the first sensor (10) opposite the second sensor (12). In the preferred embodiment, the invention further includes third and fourth opposing sensors (14, 16) clocked 90° from the first and second sensors (10, 12).

Abstract: A solid-state eye-safe laser and method with gain boost by dual-wavelength, synchronized pumplights. The laser includes a medium doped with ions that emit light at a laser wavelength as a result of the transition of electron energy from an upper energy level manifold to a lower energy level manifold. A first pumplight couples energy into the medium at a first wavelength that excites a first portion of the ions into said upper energy level manifold. A second pumplight couples energy into said medium at a second wavelength that excites a second portion of the ions to a third energy level manifold. A fraction of the ions relax to the upper energy level manifold and thereby increase the gain of the laser (2). The laser may be an erbium crystal laser, using yttrium-aluminum-garnet operating near 1640 nanometers.

Abstract: A system and method for detecting breaklock for correlation trackers. The inventive system includes a first circuit (50) for computing energy EL in a residual image, a second circuit (52) for computing energy EI in an input image, and a third circuit (54) for computing a residual metric RL based on the residual image energy EL scaled by the input image energy EI. In the illustrative embodiment, the system further includes a fourth circuit (56) for comparing the residual metric RL to a threshold TR, and a fifth circuit (58) for setting a breaklock signal based on the output of the fourth circuit (56).

Abstract: A beam control system and method: The inventive system includes, an arrangement for receiving a first beam of electromagnetic energy; measuring wavefront aberrations in the first beam with a wavefront sensor; and removing global tilt from the measured wavefront aberrations to provide higher order aberrations for beam control. In the illustrative embodiment, the invention uses a traditional (quad-cell) Shack-Hartmann wavefront sensor to measure wavefront aberrations. An adaptive optics processor electronically removes the global tilt (angular jitter) from this measurement leaving only the higher-order Zernike components. These higher-order aberrations are then applied to wavefront control elements, such as deformable mirrors or spatial light modulators that correct the tracker image and apply a conjugate distortion to the wavefront of the outgoing HEL beam. A track error (angular jitter) component is supplied by a separate fine track sensor.

Abstract: An imaging optical system has an optical axis and a refractive optical group including a lens lying on the optical axis. At least one lens of the refractive optical group lying on the optical axis has an aspheric front surface and an aspheric back surface. An image surface lies on the optical axis, and the refractive optical group forms an image at the image surface. The image surface is preferably substantially planar. A detector, such as a focal plane array detector, lies on the optical axis such that a ray of light passing through the lens is incident upon the detector. It is preferred that there are two lenses lying on the optical axis, with each lens having an aspheric front surface and an aspheric back surface. The imaging optical system is suitable for use as a large-aperture, wide-field-of-view, compact system having an F number of less than about F/1.5, a field of view of more than about 45 degrees, and a telephoto ratio of less than about 2.0.

Abstract: An active-power filter includes control circuitry to combine an integrated output-voltage feedback signal, an input-voltage sense signal and an output-load feedforward signal to generate a control signal. An output-load subsystem draws the output current from the active-power filter and the output-load feedforward signal indicates when current drawn by an output-load subsystem changes. In some embodiments, the output-load subsystem may draw output current from the power converter having an output current ripple at a nominal frequency, which may range, for example, between about 35 and 100 Hz. The control circuitry may include an integrator to integrate the output-voltage feedback signal. The integrator may have a control loop bandwidth significantly less than the nominal ripple frequency to loosely regulate the output voltage while the input current drawn by the active-power filter is tightly regulated.

Abstract: An imaging optical system includes a first imaging structure having a first optical axis and a first field of view, wherein the first imaging structure forms an image on a common focal plane, and a second imaging structure having a second optical axis parallel to the first optical axis and a second field of view different from the first field of view, wherein the second imaging structure forms an image on the common focal plane. The imaging structures preferably contain identical lens modules, most preferably identical Petzval lenses, and achromatic or apochromatic prisms of different spatial orientations. A planar sensor structure lies in the common focal plane, wherein the first optical axis and the second optical axis pass through the planar sensor structure.

Abstract: A polarimeter simultaneously measures the Stokes vectors of a light beam using an optics unit with a slit with a slit axis, a foreoptics that focuses the light beam from the point location through the slit, a collimator that receives the light beam from the slit and collimates the light beam, a cylinder lens that receives the light beam from the collimator, wherein the cylinder lens has a cylindrical axis parallel to the slit axis, a re-imaging lens that images the light beam from the cylinder lens onto a focal plane, and a set of polarizing filters including three polarization filters having three different polarizations. The polarization filters are adjacent to each other in a direction perpendicular to the slit axis and lie between the cylinder lens and the focal plane so that the light beam is directed onto the set of polarizing filters.

Abstract: Active power filters and methods control and regulate the input current drawn from an electric power bus to a DC level. Load current fluctuations and ripple current reflected back to the electric power bus are significantly reduced or substantially eliminated. A switch mode power converter with a very low bandwidth output voltage regulation control loop uses input voltage feedforward, output load feedforward, and output voltage feedforward to provide a regulated DC input current significantly attenuating input ripple current drawn from the electric power bus.

Abstract: An imaging polarimeter sensor includes an achromatic beam-splitting polarizer that receives a polychromatic image beam of a scene and simultaneously produces a first polarized polychromatic image beam and a second polarized polychromatic image beam. The second polarized polychromatic image beam is of a different polarization than the first polarized polychromatic image beam and is angularly separated from the first polarized polychromatic image beam. The achromatic beam-splitting polarizer preferably includes a Wollaston prism through which the polychromatic image beam passes, and at least one grating through which the polychromatic image beam passes either before or after it passes through the Wollaston prism. An imaging detector receives the first polarized polychromatic image beam and the second polarized polychromatic image beam and produces an output image signal responsive to the first polarized polychromatic image beam and the second polarized polychromatic image beam.

Abstract: A solid state, laser light control device (20, 30) and material (10), and methods of producing same. The device (20, 30) and material (10) consist essentially of a host material (14) which contains: a dopant species (16) at a first valence state (a), the concentration of which increases with distance from the surface (18); and the same dopant species (16) at a second valence state (b), the concentration which decreases with distance from the surface (18). The method comprises the steps of: obtaining a doped solid state material (14); exposing the solid state material (14) to elevated temperature, for a period of time, in an oxidizing or reducing atmosphere. The elevated temperature and time of exposure are selected to change the valence state (a) of the dopant (16) in direct proportion to distance from the surface (18) of the solid state material (16).

Abstract: The invention concerns a washing composition for washing a surface to deposit thereon substantially water-insoluble particles. The aqueous washing composition of the invention comprises an anionic surfactant, the particulate substance to be deposited and a water-soluble cationic non-cellulosic polymer which enhances the deposition of the particulate substance onto the surface but which cationic polymer does not form in the composition a water-insoluble complex with the anionic surfactant, the cationic charge density of the polymer being from 0.0001 to 0.0017; the concentration of the cationic polymer in the washing composition being from 0.0001% to 0.01% by weight; and the concentration of the surfactant in the washing composition being from 0.01% to 5% by weight.