Trw Limited

Northrop Grumman Systems Corporation

Donald W Davies

Richard A Hutchin

Mark S Slater

A lateral shearing interferometer wavefront sensor system ( ) that employs a double-shear/full aperture approach to correct for branch points in the wavefront of an optical beam ( ) that has been aberated. The wavefront sensor system ( ) includes a lateral shearing interferometer ( ) having a beam splitter ( ) that splits the beam ( ) into a first split beam ( ) and a second split beam ( ), a beam shifter ( ) that shifts the first split beam ( ) relative to the second split beam ( ), and a beam combiner ( ) that combines first shifted split beam ( ) and the second split beam ( ) into a combined beam ( ). The combined beam ( ) provides an interference pattern that includes a plurality of interfered beam portions ( ). A deformable mirror ( ) includes a plurality of actuators ( ) which deform the mirror ( ) to correct the beam wavefront. The interfered portions ( ) are twice the distance apart between actuators ( ),or a double shear such that interfering portions ( ) do not align with branch cuts between the actuators ( ).

Low signal-to-noise ratio branch-point-capable adaptive optics sensor

An optical system ( ) for correcting wavefront aberrations of an optical beam ( ). The beam ( ) is received by an entrance pupil ( ), where a portion of the beam ( ) at the entrance pupil ( ) is coupled off of the main beam ( ) to be used as a reference beam ( ). The reference beam ( ) is taken from a small enough portion of the main beam ( ) so that the temporal coherence of the reference beam wavefront is substantially in phase. The reference beam ( ) is amplified by a coherent reference amplifier ( ), expanded and collimated. The main beam ( ) and the collimated beam ( ) are applied to a beam splitter ( ) that splits the main beam ( ) and the reference beam ( ) into two separate beam paths, where the main beam ( ) and the reference beam ( ) traveling along a common path are coupled together. One optical path from the beam splitter ( ) is applied to a detector array ( ) and the other optical path from the beam splitter ( ) is applied to a light valve ( ). Those portions of the main beam ( ) that are more than 90&deg; out of phase with the reference beam ( ) destructively interfere at the detector array ( ). The outputs of the detectors in the array ( ) are measured by threshold electronics ( ). The threshold electronics ( ) cause the light valve ( ) to attenuate the portions of the beam on the other path that are the destructively interfering portions of the main beam ( ) and the reference beam ( ) so those portions do not pass through the light valve ( ). Therefore, only those portions of the main beam ( ) that are substantially in phase with the reference beam ( ) continue on through the receiver optics.

Adaptive optics system using wavefront selection

An improved lateral shearing interferometer system for use with an original optical wavefront and a displaced optical wavefront having a phase difference from the original optical wavefront is disclosed. It comprises a lateral shearing interferometer that responds to the original optical wavefront and the displaced optical wavefront and develops an optical interference pattern representative of the optical phase differences. An optical detector located at the focal plane of the optical interference pattern provides a selective array of electrical signals representative of separated portions of the interference pattern. A data processor is programmed to indicate the separated portions of said interference pattern, which has pixels in non-adjacent locations in odd rows and no pixels in even rows. The pixels correspond to locations of actuators for correcting the phase difference.

Lateral shearing interferometer system with masked interference pattern

A dual sensor wavefront correction system is adaptable to correcting wavefronts including wavefronts that are severely scintillated. The system includes a Hartmann wavefront sensor as well as a unit shear lateral shearing interferometer (LSI) wavefront sensor. The optical output signals from the Hartmann wavefront sensor are applied to a real reconstructor which provides an estimation of the distortion in the wavefront during most conditions except for conditions of severe turbulence. In order to provide compensation for the phase discontinuities in a scintillated wavefront, a unit shear lateral shearing interferometer (LSI) wavefront sensor is provided. The optical output signals from the unit shear LSI wavefront sensor are processed by a complex reconstructor in order to provide relatively accurate estimates of the tilt signals at the discontinuities. The output of the real reconstructor and the complex reconstructor are combined in a synergistic manner to provide a composite correction signal to the actuators of a deformable mirror. As such, the wavefront correction system has a relatively wide dynamic range and is not blind to discontinuities in the wavefronts as a result of turbulence. A steering mirror may also be provided to optimize the dynamic range of the deformable mirror.

Dual sensor atmospheric correction system

A spectrometer construction incorporates a single lens system (11) to both focus light input to the spectrometer on a diffraction grating (9) and to focus the light dispersed by the diffraction grating into separate spectral constituents back through that lens onto an image plane (15) for processing. Ordinary photographic lenses with fast lenses of f2 or better are able to serve as the lens system, thereby providing a higher quality system at lower cost than previously possible. With the light path doubling back through the spectrometer lens the space required for a spectrometer's optical system is reduced and results in a more compact spectrometer.

Compact fast imaging spectrometer

An image processing system and method for performing optical signal processing including target recognition and filtering. The system is particularly useful in remote or mobile imaging processing systems where the data gathering capabilities exceed the ability of the system to transmit this data over conventional data links. The system includes a spectrometer which receives portions of an image and produces a plurality of spectra of individual pixels in the image. A light-sensitive detector receives the spectra and converts the spectra into electrical signals. A memory unit stores a predetermined matrix of coefficients, each coefficient corresponding to one wavelength of said spectral signal. A multiply and accumulate unit received one spectral signal and a corresponding matrix coefficient and adds the products to generate a spectral measure for each pixel in the image. By changing the matrix in the memory unit, it is possible to synthesize a wide variety of desired optical processing functions such as target recognition, correlation and filtering.

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Torrance, CA, United States of America

Donald W Davies