Laser detection and image fusion system and method

Patent metadata

Field	Value
Publication number	US-9897688-B2
Application number	US-201414554254-A
Country	US
Kind code	B2
Filing date	Nov 26, 2014
Priority date	Nov 30, 2013
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

Abstract

This invention describes a method for operating a weapon targeting system comprising the steps of using a laser to fire a single pulse at a target to obtain a reflected laser pulse; detecting the reflected laser pulse as a signal by a SWIR focal plane; detecting background illumination by using the SWIR focal plane; scene clutter filter and using optical filtering if it is necessary to suppress background illumination.

First claim

What is claimed is:

1. A laser marker and laser marker verification system comprising:
synchronizing an integration time of an exposure window of a first camera focal plane to an arrival of at least a single laser pulse reflected from an object, whereby said at least a single laser pulse originates from a laser source comprising and under the control of the laser marker system or originates from an external source not under control of the laser marker system;
determining arrival timing of said laser pulse and focal plane array (FPA) exposure window synchronization timing for said at least a single reflected laser pulse or said series of reflected laser pulses from an adjunct system;
detecting said reflected at least one laser pulse as a signal by said first camera focal plane array (FPA) with synchronous timing and minimized exposure window duration corresponding to a laser pulse event in a first image;
obtaining a second image of said object without said reflected at least one laser pulse;
spatially aligning said first and second images to eliminate effects of camera motion between said first and said second images;
spatially correlating the location of said detected reflected at least one laser pulse in an image to corresponding locations in other acquired images; and
providing an indication of said laser spot location in imagery of said object in a scene.

2. The system of claim 1 wherein said at least a single pulse is a single short wave infrared (SWIR) pulse.

3. The system of claim 1 comprising eliminating background clutter by subtracting said second image from said first image to create a difference image.

4. The system of claim 1 wherein wavelength band of said first and said second camera is one of SWIR, long wavelength infrared (LWIR), mid-wavelength infrared (MWIR), and visible, such that said first camera is sensitive to a wavelength of said laser and wavelength band of said first camera is different from wavelength band of said second camera.

5. The system of claim 1 wherein said at least a single laser pulse originates from an integral laser illuminator and pulse fire timing is under control of said system and synchronized to a focal plane detector array exposure window.

6. The system of claim 1 comprising synchronizing timing of said focal plane detector array exposure window to pulsed laser illumination from an external laser source not under control of said system.

7. The system of claim 1 comprising applying a threshold value to pixel data from a difference image to reject pixel amplitudes below a defined minimum signal level as noise and to identify the pixels above said threshold value as signal to create a thresholded image.

8. The system of claim 7 comprising applying a spatial filter to said thresholded image to identify a candidate pixel grouping that best matches an expected pixel by pixel extent of said laser pulse energy.

9. The system of claim 1 wherein receiver optics comprise an instantaneous field of view (IFOV) of about 200 μrad, an aperture diameter of about 60 mm, an F/# of about 2.08, a horizontal field of view (HFOV) of about 7.3 degrees, and a spectral bandwidth of about 0.9 μm to about 1.7 μm.

10. A method for operating a laser marker and verification system comprising the steps of:
providing a first imaging system capable of detecting reflected laser pulse energy from an illuminated source and synchronizing an exposure window of a detector array of said first imaging system to arrival of a laser pulse, wherein said laser firing comprises
predictive timing generated by a laser pulse detector correlated to known pulse repetition frequency (PRF) codes utilized by infrared markers and designators;

providing an optical filter to reduce amount of ambient light on said detector array, and capable of being inserted in and removed from an optical path of said system;
processing images from said imaging system comprising frame subtraction and spatial filtering to identify a spatial location of said detected laser energy in acquired imagery; and
inserting symbology indicative of a spatial location of a laser spot in output imagery of a first camera.

11. The method of claim 10 further comprising:
filtering with a narrow bandpass optical filter in an optical path allowing said laser pulse energy to pass through while suppressing as out-of-band detected background illumination particularly in bright conditions, whereby signal-to-noise ratio is increased allowing an increase in said exposure window duration.

12. The method of claim 10 wherein said exposure window duration is adjusted dynamically to account for bright day, overcast and night time operation.

13. The method of claim 10 comprising providing a second imaging system aligned to a field of view of said first imaging system;
transferring spatial location of said detected laser pulse energy to said second imaging system;
identifying a spatial location in imagery of said second imaging system; and
inserting symbology indicative of said spatial location of said laser spot in output imagery of said second imaging system.

14. The method of claim 10 wherein illumination conditions comprise bright sun, overcast daylight, full moon, quarter moon, clear starlight, and overcast starlight.

15. The method of claim 10 wherein a source of said detected reflected laser pulse energy is an external system issuing pulses in a known pattern, whereby prediction of arrival of next laser pulse is accomplished so that acquisition of said pulse by said first camera focal plane array is during exposure time of said first camera focal plane array.

16. The method of claim 10 comprising transferring said laser spot location to optional additional cameras for indication of laser spot location in the imagery of these cameras.

17. The method of claim 10 wherein a frame of imagery not containing reflected laser energy is collected as representative of the scene and subtracted from a frame of imagery that also includes energy from said reflected laser pulse.

18. The method of claim 10 comprising a thresholding process and spatial filtering process applied to a difference image.

19. A laser marker and laser marker verification system for transferring a location of and displaying a laser spot display marker acquired through use of a first camera operating in a wavelength band sensitive to a laser wavelength to an image acquired from a second camera operating in a wavelength band insensitive to said laser wavelength comprising:
collecting imagery from a focal plane array (FPA) of said first camera;
saving said first camera image of AN object;
firing a single laser pulse at said object;
detecting reflected single laser pulse by said first camera FPA;
detecting background illumination by said first camera FPA;
suppressing said first camera background illumination;
applying a scene thresholding noise rejection filter;
applying a spatial filter to said first camera image to allow detection of said location of said laser spot in said first camera image;
determining coordinates of said laser spot in said first camera image;
collecting an image of said object using a second camera;
locating laser spot coordinates determined from first camera image in said second camera image; and
displaying said laser spot display marker at said laser spot coordinates in said second camera image.

Assignees

• Bae Systems Information & Electronic Systems Integration Inc
• Bae Sys Inf & Elect Sys Integ

Inventors

• Choiniere Michael J
• Cirillo Brendan P
• Constantino Robert W
• Degtiarev Egor V
• Feda Francis M
• Hu Haijun H
• Mallalieu Mark R
• Odonnell Brian F

Classifications

• F41G3/06

  with rangefinder (rangefinders per se G01C) · CPC title

• G06T2207/10048

  Infrared image · CPC title

• G06T7/254

  involving subtraction of images · CPC title

• F41G3/145

  using a target illuminator · CPC title

• G06T2207/20224

  Image subtraction · CPC title