SEMI-ACTIVE OPTICAL TRACKING SYSTEM

• US 20100283988A1
• Filed: 05/08/2009
• Published: 11/11/2010
• Est. Priority Date: 05/08/2009
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Mosier, Daniel J., Denney, Dwight L., Yoon, John
• Granted Patent: US 8,049,870 B2
• Time in Patent Office: Days
• US Class Current: 356/4.01
• CPC Class Codes: F41G 1/34 combined with light source, e.g. spot light
• CPC Class Codes: F41G 3/145 using a target illuminator
• CPC Class Codes: F41G 5/08 Ground-based tracking-systems for aerial targets
• CPC Class Codes: G01S 3/7865 using correlation of the live video image with a stored image
• CPC Class Codes: G06T 2207/30212 Military
• CPC Class Codes: G06T 7/251 involving models

Abstract

A system and method for tracking an airborne target including an illumination source (e.g., a diode laser array) is used to enhance a target signature and a detector (e.g., a passive high-speed camera) is used to detect to electromagnetic radiation (e.g., infrared radiation) reflected off the target. The received electromagnetic radiation may be processed by a digital computer and passed through a spatial filter that implements a band limited edge detection operation in the frequency domain. The filter may remove low spatial frequencies that attenuate soft edged clutter such as clouds and smoke as well as filter out artifacts and attenuated medium to high spatial frequencies to inhibit speckle noise from the detector as well as speckle from the laser return off the target.

Claims

1. A tracking system for use with a high energy laser, the system comprising:

an illuminator for generating electromagnetic radiation to be directed at an airborne target;

a track telescope having a track detector configured to receive electromagnetic radiation reflected from the airborne target;

a processor coupled to the track detector and a steering controller of a high energy laser (HEL), wherein the processor processes target information based at least in part on the received electromagnetic radiation detected from the track detector by applying a band-limited edge detection operation to the target information and generates band-limited edge detection data used to identify edges of the airborne target in order to track the airborne object.

2. The tracking system of claim 1, wherein the illuminator is at least one selected from a group consisting of a solid-state laser, a fiber laser or a laser diode array, wherein the illuminator has an output beam that is directed to a target through either free-space coupled or fiber-coupled delivery.

3. The tracking system of claim 2, wherein the illuminator outputs the electromagnetic radiation in an electromagnetic spectrum range between visible (about 0.5 micrometer) and infrared (about 10.0 micrometer).

4. The tracking system of claim 1, wherein the track detector is a camera operable to detect the electromagnetic radiation reflected from the airborne target.

5. The tracking system of claim 1, wherein further including a storage element coupled to the processor, wherein the storage element stores reference target information associated with one or more airborne targets.

6. The tracking system of claim 5, wherein the reference target information is stored in a database of reference objects that may be used to predict the attitude of the target.

7. The tracking system of claim 6, wherein the database includes a plurality of airborne targets and track information associated with each of the plurality of airborne targets.

8. The tracking system of claim 6, wherein at least one reference object is in the form of a silhouette.

9. A method for tracking an airborne target, the method comprising:

generating electromagnetic radiation to be directed at an airborne target;

receiving electromagnetic radiation reflected from the airborne target with a track detector;

processing the received electromagnetic radiation to generate a control signal to control a steering controller used to direct a high energy laser (HEL), wherein the received electromagnetic radiation detected is processed by applying a band-limited edge detection operation to target information based at least in part on the received electromagnetic radiation to generate band-limited edge detection data used to identify edges of the airborne target in order to track the airborne object.

10. The method of claim 9, wherein the electromagnetic radiation is produced by at least one of a solid-state laser, a fiber laser, or a laser diode array, wherein an output beam formed from the electromagnetic radiation is directed to a target through either free-space coupled or fiber-coupled delivery and the electromagnetic spectrum range is between visible (about 0.4 micrometer) and infrared (about 10.0 micrometer).

11. The method of claim 9, wherein the step of receiving the electromagnetic radiation is performed by a camera operable to detect the electromagnetic radiation reflected from the airborne target.

12. The method of claim 11, wherein the camera generates a target image of the detected electromagnetic radiation.

13. The method of claim 12, the target image is converted from a spatial domain to a frequency domain and the band-limited edge detection operation is performed on the target information in the frequency domain.

14. The method of claim 13, wherein the band-limited edge detection operation removes frequencies between a low threshold value and above a high threshold value of the band-limited edge detection data.

15. The method of claim 9 further including comparing a first target image acquired by the track detector with a second target image acquired by the track detector to determine movement of the airborne target in a period of time between the first target image and the second target image.

16. The method of claim 15 further including calculating a centroid associated with the airborne target from information derived from the first target image and the second target image.

17. The method of claim 15 further including calculating a centroid associated with the airborne target from information derived from band-limited edge detection data associated with the first target image and the second target image.

18. The method of claim 15 further including comparing target information associated with the received electromagnetic radiation with an object list that includes one or more airborne targets stored in a storage element coupled to the processor, wherein the object list is stored in a database of reference objects that may be used to predict an attitude and/or shape of the airborne target.

19. A method for tracking an airborne target, the method comprising:

generating electromagnetic radiation to be directed at an airborne target;

receiving electromagnetic radiation reflected from the airborne target with a track detector;

processing the received electromagnetic radiation to generate a control signal to control a steering controller used to direct a high energy laser (HEL), wherein the received electromagnetic radiation detected is processed by applying a band-limited edge detection operation to target information based at least in part on the received electromagnetic radiation to generate band-limited edge detection data used to identify edges of the airborne target;

processing one or more reference images stored in a storage element coupled to the processor by applying a band-limited edge detection operation to the one or more reference images;

determining an offset value for aiming a high energy laser (HEL) based on the offset value;

providing the offset value to a steering controller coupled to the processor for steering the HEL.

20. The method of claim 19, wherein the electromagnetic radiation is produced by at least one of a solid-state laser, a fiber laser, or a laser diode array, wherein an output beam formed from the electromagnetic radiation is directed to a target through either free-space coupled or fiber-coupled delivery and the electromagnetic spectrum range is between visible (about 0.4 micrometer) and infrared (about 10.0 micrometer).

21. The method of claim 19, wherein the step of receiving the electromagnetic radiation is performed by a camera operable to detect the electromagnetic radiation reflected from the airborne target.

22. The method of claim 21, wherein the camera generates a target image of the detected electromagnetic radiation.

23. The method of claim 22, the target image is converted from a spatial domain to a frequency domain and the band-limited edge detection operation is performed on the target information in the frequency domain.

24. The method of claim 23, wherein the band-limited edge detection operation removes frequencies between a low threshold value and above a high threshold value of the band-limited edge detection data.

25. A high energy laser (HEL) tracking system comprising:

an illuminator for generating electromagnetic radiation to be directed at an airborne target;

a track telescope having a track detector configured to receive electromagnetic radiation reflected from the airborne target, wherein the track detector is configured to detect the electromagnetic radiation reflected from the airborne target;

a track source selector for selecting a type of airborne target to track, wherein the selector is operable in a first setting to when the airborne target is a mortar shell and operative in a second setting when the airborne target is an unmanned aerial vehicle (UAV);

a processor coupled to the track detector and a steering controller of a high energy laser (HEL), wherein the processor process target based at least in part on the received electromagnetic radiation detected from the track detector by applying a band-limited edge detection operation to the target information and generates band-limited edge detection data used to identify edges of the airborne target in order to track the mortar shell or the UAV.