US 9,541,635 B2 · Laser phase diversity for beam control in phased laser arrays

Abstract

Systems and methods that combine forward-model image reconstruction techniques with tomographic estimation of three-dimensional atmospheric turbulence to enable high-quality anisoplanatic imaging and beam control through the atmosphere over an extended field of view using a phased laser array. The system projects laser energy onto specific locations of extended objects in various geometries, overcomes atmospheric anisoplanatism and backscatter; estimates phase across the full aperture, and reconstructs the target object in great detail to enable high-resolution aimpoint selection and maintenance. Aimpoint maintenance is performed by sequentially analyzing a passive image and a laser spot in rapid succession, in each subaperture at high signal-to-noise ratio. As a further improvement, backscatter issues from the projected laser beam are eliminated by cycling the laser and/or sequentially lasing on different wavelengths within the laser gain bandwidth.

Claims19

Dependent claims

A system comprising a beam director and a multiplicity of laser channels arranged for transmitting light to and receiving light from said beam director, wherein each of said laser channels comprises:

a laser for outputting a laser beamlet;
a phase modulator for modulating a phase of the laser beamlet output by said laser;
a polarizing beam splitter arranged such that a laser beamlet output by said laser will impinge on said polarizing beam splitter;
a diverging lens arranged such that laser light transmitted through said polarizing beam splitter will impinge on said diverging lens, wherein said diverging lens is displaceable in three mutually orthogonal directions;
a primary lenslet arranged such that laser light transmitted through said diverging lens will impinge on said primary lenslet and laser light transmitted through said primary lenslet will impinge on said beam director;
a set of actuators for actuating displacement of said diverging lens in said three mutually orthogonal directions;
and
a focal plane array arranged such that light that passed through said diverging lens and then impinged on said polarizing beam splitter will impinge on said focal plane array, said focal plane array converting impinging light into electronic imaging data.

5 more elements

A method for concentrating a laser beam formed by a laser array on an aimpoint on a target object in a field of view of a beam director, comprising:

(a) acquiring a multiplicity of incoherent images of the target object while applying phase diversity and while the laser array is turned off;
(b) reconstructing full-aperture wavefronts for each isoplanatic patch of the target object from said incoherent images using a combination of focus diversity or phase tomography based on subaperture image measurements;
(c) reconstructing a multiplicity of subaperture images with reduced blurring due to phase aberrations from said incoherent images;
(d) selecting a crude aimpoint close to or inside an aimpoint region based on said multiplicity of reconstructed subaperture images;
and
(e) firing a multiplicity of lasers using a reconstructed global phase appropriate for an isoplanatic patch around said crude aimpoint.

3 more elements

A system comprising a laser array, a lenslet array, a multiplicity of focal plane arrays, a multiplicity of polarizing beam splitters, and a multiplicity of sets of actuators, wherein:

said laser array comprises a multiplicity of phase modulators;
said lenslet array comprises a multiplicity of diverging lenses, each of said diverging lens being independently displaceable in three mutually orthogonal directions by a respective set of said multiplicity of sets of actuators;
said polarizing beam splitters are respectively disposed between a respective laser of said laser array and a respective diverging lens such that a respective laser beamlet output by said respective laser will first pass through a respective polarizing beam splitter and then pass through a respective diverging lens;
said focal plane arrays are respectively arranged such that light that has passed through a respective diverging lens and then impinged on a respective polarizing beam splitter will impinge on said respective focal plane array, said focal plane arrays converting impinging light into electronic imaging data;
and
a computer system receives incoherent imaging data from said focal plane arrays, said computer system being programmed to transmit control data to said multiplicity of said sets of actuators for causing displacements of said diverging lenses and phase data to said phase modulators for setting the overall subaperture phase, said control data and phase data being derived from said incoherent imaging data by reconstructing full-aperture wavefronts using a multi-frame blind deconvolution algorithm, a forward model, or integration of subaperture tilts.

3 more elements

Dependencies are inferred from the claim text.

Laser phase diversity for beam control in phased laser arrays

Life of this patent

Laser phase diversity for beam control in phased laser arrays

Life of this patent

Abstract

Claims19