Acoustical imaging interferometer for detection of buried underwater objects

• US 6,700,833 B2
• Filed: 08/14/2002
• Issued: 03/02/2004
• Est. Priority Date: 09/17/2001
• Status: Expired due to Fees

• Current Assignee: Frantorf Investments GmbH LLC (Intellectual Ventures LLC)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Erikson, Kenneth R.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US10/219,169
• Publication Number:
  US 20030053373A1
• Time in Patent Office: 566 Days
• Field of Search: 367/11, 367/131, 367/87, 367/88, 367/7, 396/25, 348/81, 736/32, 736/33, 736/49, 736/27
• US Class Current: 367/88
• CPC Class Codes: G01S 15/003 Bistatic sonar systems; Multistatic sonar systems
• CPC Class Codes: G01S 15/88 Sonar systems specially adapted for specific applications seismic or acoustic prospecting or detecting G01V1/00
• CPC Class Codes: G01S 15/89 for mapping or imaging
• CPC Class Codes: G01S 7/6245 Stereoscopic displays; Three-dimensional displays; Pseudo-three dimensional displays
• CPC Class Codes: G01V 1/38 specially adapted for water-covered areas G01V1/28 takes precedence

Abstract

A method and system for underwater detection of fully or partially buried objects such as sea mines and underwater cables, consisting of a mobile underwater platform configured with a real-time, three dimensional acoustical camera with a downward directed field of view used as an imaging interferometer, coordinated with a high-intensity, low frequency acoustical transmitter directed as to disturb the loose particulate or elastic matter comprising the seafloor within the field of view of the camera. The images recorded by the camera display the relative motion of the seafloor material before and after an acoustical pulse, in contrast to the lesser or no motion of submerged solid objects. Distinguishing man-made from natural objects is aided by recognizing geometric shapes apparent within the varying image density, not common in nature.

Claims

1. A system for detecting objects under the seafloor comprising:

a mobile underwater platform;

an ultrasonic underwater camera with a field of view projecting downward, said camera having a frame rate and range gated response times for producing three dimensional volumetric images of a selected target area volume at least partially including said seafloor;

an acoustic transducer for applying an acoustic pulse to said seafloor within said field of view; and

a computer for coordinating operation of said camera and said acoustic transducer, wherein a first volumetric image of said target area volume is produced by the ultrasonic underwater camera, and a second volumetric image of said target area volume is produced by the ultrasonic underwater camera after an acoustic pulse is applied to said seafloor within said target area volume.

2. A system for detecting objects under the seafloor according to claim 1, wherein said computer is further adapted to compare images for evidence of movement of seafloor materials relative to said objects.

3. A system for detecting objects under the seafloor according to claim 1, further comprising:

means for identifying the location of said target area volume.

4. A system for detecting objects under the seafloor according to claim 1, further comprising:

means for transporting said images to the surface.

5. A system for detecting objects under the seafloor according to claim 1, further comprising:

means for recording said images.

6. A system for detecting objects under the seafloor according to claim 1, wherein said acoustical transducer is extendible from said platform towards said seafloor.

7. A system for detecting objects under the seafloor according to claim 1, further comprising:

means for discriminating man-made from natural objects detected in said images.

8. A system for detecting objects under the seafloor according to claim 1, further comprising:

means for detecting a distance from said camera to said seafloor.

9. A system for detecting objects under the seafloor according to claim 1, wherein said camera is na 3 MHz ultrasonic underwater camera configured for producing said three dimensional volumetric images at a 5 to 16 feet range at a rate of 15 frames/second, said camera having an acoustical lens configured for forming an image on a fully-populated, 128×

128 array of piezocomposite, acoustical transducer elements.

10. A system for detecting objects under the seafloor according to claim 1, wherein said camera is operating as an acoustical imaging interferometer configured with a resolution of less than one wavelength.

11. A system for detecting objects under the seafloor comprising:

a mobile underwater platform;

an ultrasonic underwater camera with a field of view projecting downward, said camera having a frame rate and range gated response times for producing three dimensional volumetric images of a selected target area volume at least partially including said seafloor;

an acoustic transducer for applying an acoustic pulse to vibrate said seafloor within said field of view; and

a computer for coordinating operation of said camera and said acoustic transducer wherein a volumetric image of said target area volume is produced after applying said acoustic pulse.

12. A system for detecting objects under the seafloor according to claim 11, wherein said camera is operating as an acoustical imaging interferometer configured with a resolution of less than one wavelength.

13. A method for detecting objects under the seafloor comprising:

positioning an ultrasonic underwater camera with its field of view projecting downward towards a selected target area volume at least partially including said seafloor, said camera having a frame rate and range gated response times for producing three dimensional volumetric images;

positioning an acoustic transducer for applying an acoustic pulse to said seafloor within said field of view;

producing a first volumetric image of said target area volume with said camera;

applying an acoustic pulse to vibrate said seafloor within said target area volume; and

producing a second volumetric image of said target area volume.

14. A method for detecting objects under the seafloor according to claim 13, further comprising:

comparing images for evidence of movement of seafloor materials relative to objects partially or fully submerged beneath said seafloor.

15. A method for detecting objects under the seafloor according to claim 13, further comprising:

transporting said images to the surface.

16. A method for detecting objects under the seafloor according to claim 13, further comprising:

recording said images.

17. A method for detecting objects under the seafloor according to claim 13, further comprising:

discriminating man-made from natural objects detected in said images.

18. A method for detecting objects under the seafloor according claim 13, wherein said producing includes producing said volumetric images at a 5 to 16 feet range at a rate of 15 frames/second.

19. A method for detecting objects under the seafloor according to claim 13, wherein said camera is operating as an acoustical imaging interferometer configured with a resolution of less than one wavelength.

20. A system for detecting objects wider the seafloor comprising:

a mobile underwater platform;

an ultrasonic underwater camera with a field of view projecting downward, said camera having a frame rate and range gated response times for producing three dimensional volumetric images of a selected target area volume at least partially including said seafloor;

an acoustic transducer for applying an acoustic pulse to said seafloor within said field of view;

a computer means for coordinating said camera and said acoustic transducer for producing a first volumetric image of said target area volume, and producing a second said volumetric image of said target area volume after applying said acoustic pulse; and

a means for comparing said first and second images for evidence of movement of seafloor materials relative to objects partially or fully submerged beneath said seafloor.

21. A system for detecting objects under the seafloor according to claim 20, further comprising:

means for discriminating man-made from natural objects detected in said images.

22. A system for detecting objects under the seafloor according to claim 20, wherein said camera is a 3 MHz ultrasonic underwater camera configured for producing said volumetric images at a 5 to 16 feet range at a rate of 15 frames/second.