United States of America As Represented by the Secretary of the Air Force

Lockheed Missiles & Space Company, Inc.

Textron Systems Corporation

Richard H Pohle

David M Stubbs

Michael Forrest Reiley

Robert C Ohlmann

Methods and systems for three-dimensional imaging through turbulence such as produced by the Earth's atmosphere are described. A first light source may direct an output of pulses to a target through atmospheric turbulence. A first image sensor, for example a time of arrival sensor or focal plane, may receive light from the first light source and may be used to record two-dimensional images or image slices of the target. A second light source may also be used. A second image sensor may receive light reflected from the target. An atmospheric point spread function may be derived or calculated by a means for multiframe blind deconvolution from one or more images of the target received at the second image sensor. The point spread function may be used to deblur or improve the resolution of each of the two-dimensional image slices from the first image sensor. The two-dimensional image slices may be combined to form a three-dimensional image of the target.

Three-dimensional imaging with multiframe blind deconvolution

Systems and methods are disclosed for obtaining compact, high beam-quality imaging systems for use within a spherical housing of a sensor ball of a given size. Primary and secondary mirrors may be positioned or adapted for positioning within a spherical housing of a sensor turret or sensor ball having a window. Two or more fold mirrors may direct an optical path from the primary and secondary mirrors to one or more detectors or cameras. One or more beamsplitters may be included to produce two or more optical channels for simultaneous imaging. The beamsplitter may be a beamsplitter cube having field correction structures. Embodiments may have high beam quality and may be diffraction-limited with relatively wide fields of view (FOV). A cold shield may be included that reduces MWIR or LWIR reflections at a MWIR or LWIR focal plane array. A laser illumination or designation system may be included.

Spherically-enclosed folded imaging system

An optical phased array system is disclosed that uses three methods of phased array retargeting: optical retargeting, element slew, and rigid body array slew. These work together in hierarchical fashion to reduce the retargeting disturbances and enhance system performance by shortening retargeting timelines. The optical train configuration given here is an embodiment for the approach to use the rotation of each array element (e.g. telescopes) in the phased array to provide most of the large optical path length shift required for phasing during a phased array look angle shift by individual telescope slew (i.e. venetian blind steering). The optical train configuration discussed here provides about 97% of the optical path length compensation required for a slew to .+-.20 degrees from the array normal. This greatly reduces the amplitude required of the piston control mirror if an equal optical path length is to be maintained from object to sensor. The design geometry is specific to a seven element, one ring array although the concept is applicable to other array configurations.

Automatic compensation of optical path for gimbaled phased array

A lateral transfer system for an optical beam comprises bipentaprisms (10) and (11) secured to opposite ends of an elongate transfer structure (12). The bipentaprism (10) comprises optical elements (20) and (21) positioned with respect to each other to form an empty pentaprism, and optical elements (22) and (23) positioned with respect to each other to form an empty roof-pentaprism. Similarly, the bipentaprism (11) comprises optical elements (30) and (31) positioned with respect to each other to form an empty pentaprism, and optical elements (32) and (33) positioned with respect to each other to form an empty roof-pentaprism. The optical elements (22) and (32) are beam splitters, while the other optical elements are reflectors. The bipentaprisms (10) and (11) are positioned with respect to each other so that an input beam impinging upon reflecting element (20) of the bipentaprism (10) is reflected to the beam splitter (22), where the input beam is split into a transmitted component and a reflected component. The transmitted and reflected components travel on different paths through the transfer structure (12) to the bipentaprism (11), and emerge therefrom as a pair of output beams. The average direction of the two output beams is precisely referenced in angle to the input beam.

Lateral transfer system for an optical beam

A method of producing a buried long period grating which is substantially unaffected by material stability, high tolerance requirements, stringent machining requirements, and heat transfer. The method takes a plurality of rectangular-shaped pieces of dielectric material and by a series of appropriate cuts, coatings and attachments produces an effective buried long period grating.

Method of producing a buried long period grating

Wavefronts defined by square subapertures (13, 14, 15) are focussed into spots of light on a grating (17) having two intersecting sets of lines, which diffract each wavefront into two coinciding zeroth order components and four spaced-apart first order components. For each wavefront, the various orders of diffraction components are collimated to form corresponding images of the subaperture defining the wavefront. Quadrant detectors (23, 24, 25) are located so that zeroth order image (301) of subaperture (13) fills all quadrants of detector (23), zeroth order image (401) of subaperture (14) fills all quadrants of detector (24), and zeroth order image (501) of subaperture (15) fills all quadrants of detector (25). The four first order images of each subaperture are spaced apart from each other, but overlap and interfere with four different portions of the zeroth order image: i.e., first order images (321, 322, 323, 324) overlap zeroth order image (301) to produce interference patterns ( 351, 352, 353, 354); first order images (421, 422, 423, 424 ) overlap zeroth order image (401) to produce interference patterns (451, 452, 453, 454); and first order images (521, 522, 523, 524) overlap zeroth order image (501) to produce interference patterns (551, 552, 553, 554). Each interference pattern on each detector appears on a different quadrant of that detector. Relative motion between the diffraction lines on grating (17) and the spots of light focussed onto grating (17) is provided in order to cause periodic temporal fluctuations in the intensities of the four interference patterns appearing on each of the detectors (23, 24, 25). Any phase difference occuring between the intensity fluctuations of interference patterns on corresponding quadrants of different detectors (23, 24, 25) is a measure of the relative positions of the spots of light with respect to the sets of lines on grating (17). The relative positions of the different spots of light on the grating (17) provide an indication of the relative tilts of corresponding subaperture wavefronts with respect to each other or with respect to a reference tilt.

Wavefront tilt measuring apparatus

A light spot position sensor for a wavefront sampling system having a crossed Ronchi chopper disk interposed between the diffracted laser beams of the wavefront sampling system and the intensity detectors located within the wavefront sampler. The crossed Ronchi chopper disk interrupts, at a predetermined interval, the diffracted beam of light which focuses as a spot on the disk. The relative position of the spot(s) is determined with respect to an alignment beam, the position of which is known. By means of appropriate electronics the electronic phase of each frequency of the spot is detected and compared with the phase of each frequency of the known spot to provide a two axis spot position location.

Light spot position sensor for a wavefront sampling system

A grating output wavefront sampling system having a plurality of weak gratings located on the last mirror of a beam expander utilized in conjunction with a quasi-monochromatic light source. The gratings diffract a portion of the projected beam of light to a plurality of wavefront sensors, one sensor being utilized for each grating. Knowledge of the direction of the diffracted beams obtained from the wavefront sensors give information about the direction of the projected beam by virtue of conventional grating equations and Hartmann-subaperture tilt analysis. Consequently, if the wavelength and grating spacing are known, tilt and wavefront accuracy of the projected ray or beam are readily attainable.

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Monta Vista, CA, United States of America

Richard H Pohle