Polyspectral rangefinder for close-in target ranging and identification of incoming threats

• US 7,916,278 B2
• Filed: 04/01/2005
• Issued: 03/29/2011
• Est. Priority Date: 04/06/2004
• Status: Active Grant

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Smith, M. James
• Primary Examiner(s): Alsomiri; Isam
• Application Number:
  US10/592,694
• Publication Number:
  US 20080273190A1
• Time in Patent Office: 2,188 Days
• Field of Search: 356/3.1, 356/4.01, 356/5.01, 356/5.03, 356/28, 356/29, 356/141.2, 356/614, 356/622, 356/623
• US Class Current: 356/4.01
• CPC Class Codes: F41G 3/14 Indirect aiming means
• CPC Class Codes: F41G 5/08 Ground-based tracking-systems for aerial targets
• CPC Class Codes: F41H 11/02 Anti-aircraft or anti-guided missile or anti-torpedo defence installations or systems cartridges or missiles for producing smoke or for dispensing radar chaff or infrared material F42B5/15, F42B12/48, F42B12/70; informative reference: details of radar or sonar systems G01S7/00; jamming or electronic countermeasures G01S7/38, G01S7/495, H04K3/00
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01C 3/06 Use of electric means to obtain final indication
• CPC Class Codes: G01S 17/46 Indirect determination of position data
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves

Abstract

A computationless system is provided for determining the direction of and distance to a target, involving bathing an area surrounding an area to be protected with a polyspectral series of narrow fan beams of different colors from at least two spaced-apart projectors. The differently colored beams go out at different angles, thus to color-code map the area surrounding the protected space where beams of different colors cross to form color-coded cells. Light reflected back to the area to be protected from a threat has a color code corresponding to the colors associated with beams that cross at the threat, thus to identify by the reflected colors where in space the threat is located.

Claims

1. A method for rapidly ascertaining where in space an incoming threat is located relative to a protected space, comprising the steps of:

projecting from two spaced points a multiplicity of narrow angularly displaced differently colored fan beams such that fan beams from the spaced points intersect in a surveilled area adjacent the protected space to provide a mosaic of locations, each location having a unique two-color code; and

,

detecting using a wide field of view detector the location of a threat entering into the surveilled area by ascertaining the colors of the returns from a threat at the intersection of two beams, the identity of the detected colors providing a two color code indicating where in the surveilled area the threat is located.

2. The method of claim 1, wherein the detecting step includes providing a sensor at the protected space to sense returned radiation from the threat and further including the step of countermeasuring the threat based on a line between the sensor and the location in the surveilled area at which the threat is determined to be located.

3. The method of claim 1, wherein the sensor utilizes color filters to separate out different colors of returned light.

4. The method of claim 1, wherein the detecting step includes the step of pre-mapping the surveilled area in terms of color cells at which beams from the two positions cross, each cell having a unique set of colors associated therewith.

5. The method of claim 4, wherein the map of color cells includes color bins, one each corresponding to a color cell.

6. The method of claim 5, wherein the detecting step includes entering the color bins into a lookup table and ascertaining from the lookup table the identity of the color bin and the corresponding location of the associated color cell in the surveilled area.

7. The method of claim 6, and further including deploying a countermeasure based on information in the lookup table.

8. A method for rapidly ascertaining the location of an incoming close-in threat in time to countermeasure the threat, comprising:

providing a polyspectral rangefinder in which a multiplicity of narrow beams of differently-colored light are projected out at two spaced-apart points with differently colored beams being angularly spaced apart such that differently colored beams intersect to form a number of two-color cells at predetermined intersection point locations, thus to provide a two-color code for each area that the beams intersect;

detecting threat location by the colors of beams reflected by the threat to the rangefinder using a computationless direct method such that threat location is available as soon as reflected light and the associated color code is detected; and

,

directing a countermeasure to the detected threat location, whereby countermeasuring is available for close-in threats.

9. The method of claim 8, wherein the detecting step includes providing a map of the color cells in a lookup table that correlates color code with location.

10. The method of claim 9, wherein the directing step includes using the lookup table to direct the countermeasure to the threat location.

11. The method of claim 8, wherein the angular orientation of the beams is dependent on distance to a predetermined region in the surveilled area.

12. The method of claim 11, wherein the beams have a non-uniform angular distribution.

13. A system for determining the distance to a target comprising:

a first projector for directing a first set of narrow beams of light from a first position on a sensor platform comprising a first plurality of colors toward the target;

a second projector for directing a second set of narrow beams of light from a second position on said sensor platform comprising a second plurality of colors toward the targets so that said second set intersects a beam from said first set in an intersection area, said intersection area being comprised of a plurality of color cells formed by said intersections, with each position of intersecting crossed beams being uniquely identified by a two color code, wherein each of said color cells has a unique two color signature; and

,

a receiver for sensing a reflection of light from the target and ascertaining the position of the target based on the detected color code, said detected color code corresponding to the color cell in which the target is located.

14. The system of claim 13, wherein each of said projectors includes a broadband laser, a multiplexer for outputting light at different wavelengths and optics for focusing the outputted light from said multiplexer into respective beams.

15. The system of claim 14, wherein said mutiplexer includes a main optical filter coupled to said broadband laser and secondary optical filters tapped off said main optical filter at different wavelength-selective gratings such that each of said secondary filters carries a different color.

16. The system of claim 13, wherein said receiver includes a demultiplexer coupled to received reflected light for filtering out different colors of received reflected light.

17. The system of claim 16, wherein said demultiplexer includes a main optical filter and a plurality of secondary optical fibers tapped from said main optical filter at respective wavelength-selective gratings.

18. The system of claim 17, and further including detectors at the ends of said secondary optical fibers for outputting a signal when light of a predetermined wavelength exists in the associated fiber.

19. The system of claim 18, wherein said receiver includes a lookup table having color cell bins associated with predetermined locations in the intersecting beam area, said detectors being coupled to said lookup table such that said lookup table outputs threat location corresponding to the outputs of at least two detectors.

20. The system of claim 13, wherein said beams are non-uniformly distributed.