Target-tracking laser designation

• US 5,973,309 A
• Filed: 08/27/1997
• Issued: 10/26/1999
• Est. Priority Date: 08/27/1997
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Livingston, Peter M.
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): Luu, Thanh X.
• Application Number:
  US08/919,412
• Time in Patent Office: 790 Days
• Field of Search: 250/203.1, 250/203.2, 250/203.6, 356/139.04
• US Class Current: 250/203.1
• CPC Class Codes: F41G 3/145 using a target illuminator
• CPC Class Codes: G01S 17/46 Indirect determination of position data
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves

Abstract

The present invention provides a laser tracking system including a laser generator for generating a beam of laser energy, a beam steerer for steering the beam of laser energy such that it moves in a search pattern, and a receiving device that receives laser energy reflected from a targeted object and that causes the beam steerer to vary the search pattern in response to the reflected laser energy. A tracking method associated with the laser tracking system includes the steps of generating a beam of laser energy, steering the beam of energy in a search pattern, detecting a hit spot formed from laser energy being reflected from a targeted object, diminishing the size of the search pattern in response to the detection of the hit spot, and focusing the diminished search pattern on a feature of the targeted object corresponding to the hit spot. The laser tracking system and associated method presented provide a number of advantages over conventional tracking systems. The laser tracking system employs closed loop methodologies allowing the system to accurately track targeted objects using continuously updated tracking data. The laser tracking system is able to seek and lock on to vulnerable features of potential targets. Further, the laser tracking system is able to maintain a desired aim point indefinitely and without operator intervention. This aim point maintenance allows an associated weapon to disable a target, despite any relative tracker-target motion during the munitions launch and flight.

Claims

1. A laser tracking system for tracking a target, comprising:

a laser generator for generating a beam of laser energy;

a beam steerer for steering said beam of laser energy, and for causing said beam of laser energy to move in a search pattern;

a receiving device that receives laser energy reflected from a targeted object and that causes said beam steerer to vary said search pattern in response to said reflected laser energy, said receiving device being operable to determine an angular displacement between said reflected laser energy and a reference axis of said receiving device; and

a drive device coupled to said receiving device, said drive device providing rotation of said beam steerer and said receiving device in response to drive signals generated by said receiving device.

2. The system of claim 1, wherein said beam steerer steers the beam of laser energy so as to oscillate said beam of laser energy.

3. The system of claim 2, further comprising a first dither generator for causing said beam steerer to dither said beam of laser energy in a first direction and a second dither generator for causing said beam steerer to dither said beam of laser energy in a second direction.

4. The laser tracking system of claim 1 wherein said receiving device comprises:

a positioned sensor operable to receive an incident beam of energy containing target tracking information and to determine an angular displacement between said incident beam of energy and said reference axis of said receiving device; and

a glint detector that receives said incident beam of energy and that causes the size of said search pattern to be reduced when said reflected laser energy is detected in said incident beam of energy.

5. The system of claim 4 wherein said position sensor is responsive when said incident beam of energy contains said reflected laser energy.

6. The system of claim 4 further comprising a beam splitter for separating said incident beam of energy into separate components to be delivered to said position sensor and said glint detector.

7. The system of claim 4 wherein said position sensor generates an error signal corresponding to said angular displacement, thereby causing said drive device to rotate said laser tracking system to drive said angular displacement to zero.

8. The system of claim 4 wherein said glint detector and said position sensor operate to collectively reduce the size of said search pattern and focus said search pattern on a detected feature of said targeted object.

9. The system of claim 4 further comprising a frequency selective filter for processing said incident beam of energy before it is received by said glint detector.

10. The system of claim 4 wherein said position sensor is responsive when said incident beam of energy contains targeted object centroid information.

11. A laser based tracking method comprising the steps of:

generating a beam of laser energy;

steering said beam of laser energy in a search pattern;

detecting a hit spot formed from laser energy being reflected from a targeted object;

measuring an angular displacement between said hit spot and a reference axis;

generating an error signal corresponding to said angular displacement;

orienting a tracking device to reduce said errors signal to zero;

diminishing the size of said search pattern in response to said step of detecting said hit spot; and

focusing said diminished search pattern on a feature of said targeted object corresponding to said hit spot.

12. The method of claim 11 further comprising detecting a target centroid on said targeted object.

13. The method of claim 12 wherein the focusing step comprises the steps of:

measuring an angular displacement between said target centroid and a reference axis;

generating an error signal corresponding to said angular displacement; and

orienting said tracking device to reduce said error signal to zero.