Optical muzzle blast detection and counterfire targeting system and method

• US 6,496,593 B1
• Filed: 05/05/1999
• Issued: 12/17/2002
• Est. Priority Date: 05/07/1998
• Status: Expired due to Fees

• Current Assignee: University Research Foundation, Inc.
• Original Assignee: University Research Foundation, Inc.
• Inventors: Ippolito, Thomas J., Krone, Norris J. Jr., Pierson, Roger B., Ertem, Mehmet C., Burchick, Duane A.
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): AZARIAN, SEYED H
• Application Number:
  US09/305,306
• Time in Patent Office: 1,322 Days
• Field of Search: 382/103, 340/540, 340/600, 250/330, 250/339.05, 250/334, 250/349, 250/332, 250/342, 348/155, 348/154
• US Class Current: 382/104
• CPC Class Codes: F41G 3/147 based on detection of a firing weapon
• CPC Class Codes: G01S 3/784 using a mosaic of detectors
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80

Abstract

A system for remote detection of muzzle blasts produced by rifles, artillery and other weapons, and similar explosive events. The system includes an infrared camera, image processing circuits, targeting computation circuits, displays, user interface devices, weapon aim point measurement devices, confirmation sensors, target designation devices and counterfire weapons. The camera is coupled to the image processing circuits. The image processing circuits are coupled to the targeting location computation circuits. The aim point measurement devices are coupled to the target computation processor. The system includes visual target confirmation sensors which are coupled to the targeting computation circuits.

Claims

1. In a method of detecting muzzle blasts at a distance comprising the steps of generating an infrared image signal of a selected field of view and outputting said infrared image signal in frames as a live infrared video signal, spectrally filtering each frame of said live infrared video signal to pass only frequencies within a predetermined infrared frequency range, temporally filtering each frame of said live infrared video signal to only include events within a predetermined time period, spatially filtering each frame of said live video signal to pass only said video signals having a predetermined shape, and combining the results of the spectral, temporal and spatial filtering to determine the presence or absence of a muzzle blast within said field of view, determining the coordinates of position of any detected muzzle blast within said field of view.

2. The method defined in claim 1 including the step of detecting any muzzle blast sound burst in said field of view, measuring the time interval between detection of said muzzle blast within said field of view and the time of detection of said muzzle blast sound burst, and calculating the distance to said muzzle blast.

3. The method defined in claim 1 including actuating a warning device upon detection of a muzzle blast within said field of view.

4. The method defined in claim 1 including the step of coupling said coordinates of position to a return fire aiming device and controlling the direction of fire of said return fire device in accordance with said detection of a muzzle blast.

5. The method defined in claim 1 including determining the range to said muzzle blast from said observation point by comparing the time of occurrence of the radiant energy by the muzzle blast with the detection of a sound burst from said muzzle blast and calculating the range from said observation point to said muzzle blast.

6. The method defined in claim 1 wherein said infrared image signal is defined by an array of pixels and each pixel location is adaptively tracked and the effect of background clutter is reduced by varying the detection threshold at each pixel according to the past activity around the pixel location.

7. The method defined in claim 1 wherein said spatially filtering each frame of said live video signal to pass only video signals having predetermined shape comprises adaptively filtering said infrared image signal so that image areas of high activity have higher threshold levels and areas of less activity have lower threshold levels whereby the threshold level becomes a varying surface across the image.

8. The method defined in claim 1 wherein false alarms caused by edge effects, thermal effects such as convection, camera vibration and moving objects are eliminated or minimized by performing a spatial low pass filter operation on a variance estimate signal.

9. The method defined in claim 1 wherein detection is provided in the exposure material in the following manner:

select one frame of data,

within a region of interest in the selected frame, count the number of saturated pixels and the number of full-darkness pixels,

measure the value of the darkest pixel and the distance between the brightest pixel and change the pedestal and gain setting for the image,

and repeat for the next frame.

10. The method defined in claim 9 wherein the variable exposure determines the amount of under- or over-exposure desired such that when the exposure is set at a positive value, the pedestal and gain dynamics are set to allow a number of pixels to stay saturated and, similarly, when a negative exposure control zone is selected it allows the number of pixels to stay at zero or under.

11. In a system for detecting a muzzle blast wherein an infrared camera adapted to be trained on a selected field of view outputting frames of real time infrared video signals, spectral filter (SF) for detecting predetermined intensity variations in each frame of infrared video signals to provide a first signal component indication of an event signature, a temporal event filter (TEF) connected to said SF for detecting rapid transient signatures and outputting signals representative of candidate-event times and location in said selected field of view, a spatial filter (SF) connected to said TEF for passing video signals having selected shapes, a computer connected to said SF for comparing the output of said SF with a selected threshold and outputting a binary decision indicating the presence or absence of a muzzle blast in a sequence of frames of said real time infrared video signals, a locator for determining the X and Y coordinates of the position of said muzzle blast in said selected field of view, and a display for displaying said X and Y coordinates and said range signal to a return fire shooter.