Laser beam projection system with dynamic phase compensation

Patent metadata

Field	Value
Publication number	US-10401499-B2
Application number	US-201615072214-A
Country	US
Kind code	B2
Filing date	Mar 16, 2016
Priority date	Mar 16, 2016
Publication date	Sep 3, 2019
Grant date	Sep 3, 2019

Abstract

A laser beam projection system builds on a coherent imaging to project a tightly focused laser beam onto a remote object. Coherent flood illumination and local oscillator (LO) illumination are based on one master oscillator. The coherent flood illumination is directed toward a remote object, with a second laser beam directed onto an aimpoint on the same object. A Doppler sensor provides Doppler shift data used to produce Doppler-shifted LO illumination received by a focal plane array, together with the return flood illumination. Interference between the Doppler-shifted LO illumination and the return flood illumination facilitates imaging the object despite the velocity. The wavefront error of the flood illumined remote object image is computed and compared to the desired wavefront of the second laser beam at the aimpoint, with the difference applied to a deformable mirror to shape the second laser beam wavefront for obtaining a desired aimpoint intensity profile.

First claim

What is claimed is:

1. A laser beam projection system, comprising:
a flood illumination source configured to produce coherent flood illumination that is directed toward a remote object, the coherent flood illumination derived from an output of a master oscillator (MO);
a local oscillator (LO) illumination source configured to produce LO illumination derived from an output of an LO, the LO output derived from the MO output;
a Doppler sensor configured to receive the LO illumination and a first portion of return illumination that comprises the coherent flood illumination reflected off the remote object;
at least one processor configured to generate, based on an output of the Doppler sensor, Doppler shift data for a Doppler shift corresponding to a longitudinal velocity of the remote object relative to the laser beam projection system;
a Doppler-shifted LO illumination source configured to produce Doppler-shifted LO illumination derived from the LO output and the Doppler shift data;
a high energy laser (HEL) source configured to produce an HEL beam derived from an output of an HEL MO;
a deformable mirror configured to direct the HEL beam from the HEL source toward the remote object; and
a focal plane array configured to receive a second portion of the return illumination and the Doppler-shifted LO illumination,
wherein the at least one processor is further configured to:
receive light intensity data from the focal plane array,
generate, based on the light intensity data, an image of the remote object,
determine a wavefront phase profile of the return illumination based on the image of the remote object,
calculate a wavefront error based on a comparison between the determined wavefront phase profile and a desired wavefront phase profile of the HEL beam on the remote object, and
control the deformable mirror to at least partially compensate the HEL beam for the calculated wavefront error.

2. The laser beam projection system according to claim 1 , wherein the at least one processor is configured to control the deformable mirror to adjust a high intensity hitspot formed by the HEL beam on the remote object.

3. The laser beam projection system according to claim 1 , further comprising:
an HEL LO illumination source configured to produce HEL LO illumination derived from the output of the HEL MO or from an output of an HEL LO that is derived from the HEL MO output, and
a Doppler-shifted HEL LO illumination source configured to produce Doppler-shifted HEL LO illumination derived from the HEL LO output and the Doppler shift data,
wherein the focal plane array is configured to receive the Doppler-shifted HEL LO illumination and at least a portion of HEL return illumination that comprises the HEL beam reflected off the remote object, and
wherein the light intensity data for at least some pixels of the focal plane array corresponds to interference of the Doppler-shifted HEL LO illumination with the HEL return illumination.

4. The laser beam projection system according to claim 3 , wherein the at least one processor is configured to control the deformable mirror to alter a location of the HEL beam on the remote object based upon locations of the pixels where the light intensity data corresponds to the interference of the Doppler-shifted HEL LO illumination with the HEL return illumination.

5. The laser beam projection system according to claim 3 , further comprising one or more fast steering mirrors configured to direct the HEL beam toward the remote object;
wherein the at least one processor is further configured to control the one or more fast steering mirrors to alter a location of the HEL beam on the remote object based upon locations of the pixels where the light intensity data corresponds to the interference of the Doppler-shifted HEL LO illumination with the HEL return illumination.

6. The laser beam projection system according to claim 1 , wherein the at least one processor is configured to control the deformable mirror to alter an intensity profile or a location of a high intensity hitspot formed by the HEL beam at an aim point on the remote object.

7. The laser beam projection system according to claim 1 , wherein the at least one processor is configured to apply a sharpness algorithm to the image of the remote object to determine the wavefront phase profile of the return illumination.

8. The laser beam projection system according to claim 1 , further comprising:
one or more fast steering mirrors configured to direct the HEL beam toward the remote object; and
a focus mechanism configured to focus the HEL beam onto the remote object.

9. The laser beam projection system according to claim 8 , wherein the at least one processor is configured to control a tilt of the one or more fast steering mirrors and to control a focus setting of the focus mechanism to partially compensate the HEL beam for the calculated wavefront error.

10. The laser beam projection system according to claim 8 , wherein the at least one processor is configured to decompose the wavefront error into separate tilt, focus and higher order components.

11. The laser beam projection system according to claim 10 , wherein the at least one processor is configured to control the one or more fast steering mirrors according to the tilt component of the wavefront error, to control the focus mechanism according to the focus component of the wavefront error, and to control the deformable mirror according to the higher order components of the wavefront error.

12. The laser beam projection system according to claim 10 , wherein the at least one processor is configured to control the deformable mirror according to the tilt, focus, and higher order components of the wavefront error.

13. A laser beam projection method, comprising:
using a flood illumination source, producing coherent flood illumination that is directed toward a remote object, the coherent flood illumination derived from an output of a master oscillator (MO);
using a local oscillator (LO) illumination source, producing LO illumination derived from an output of an LO, the LO output derived from the MO output;
receiving, at a Doppler sensor, the LO illumination and a first portion of return illumination that comprises the coherent flood illumination reflected off the remote object;
generating, based on an output of the Doppler sensor, Doppler shift data for a Doppler shift corresponding to a longitudinal velocity of the remote object relative to a coherent imaging system;
using a Doppler-shifted LO illumination source, producing Doppler-shifted LO illumination derived from the LO output and the Doppler shift data;
using a high energy laser (HEL) source, producing an HEL beam derived from an output of an HEL MO;
using a deformable mirror to direct the HEL beam from the HEL source toward the remote object;
receiving, at a focal plane array, a second portion of the return illumination and the Doppler-shifted LO illumination; and
using at least one processor:
receiving light intensity data from the focal plane array,
generating, based on the light intensity data, an image of the remote object,
determining a wavefront phase profile of the return illumination based on the image of the remote object,
calculating a wavefront error based on a comparison between the determined wavefront phase profile and a desired wavefront phase profile of the HEL beam on the remote object; and
controlling the deformable mirror to at least partially compensate the HEL beam for the calculated wavefront error.

14. The laser beam projection method according to claim 13 , wherein controlling the deformable mirror ad

Assignees

• Raytheon Co

Inventors

• Marron Joseph
• Halmos Maurice J
• Grayer Justin S
• Erten Gamze
• Sitter Jr David N

Classifications

• G01S7/4812 Primary

  transmitted and received beams following a coaxial path · CPC title

• G01P3/36

  Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light (G01P3/68 takes precedence; gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams G01C19/64) · CPC title

• G01S7/4917

  superposing optical signals in a photodetector, e.g. optical heterodyne detection · CPC title

• G01S17/58

  Velocity or trajectory determination systems; Sense-of-movement determination systems · CPC title

• G01S17/89 Primary

  for mapping or imaging · CPC title