Long cavity laser sensor for large FOV auto-tracking

• US 8,923,359 B1
• Filed: 07/29/2011
• Issued: 12/30/2014
• Est. Priority Date: 08/06/2010
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Browder, Mark K., Wood, James Richard, Perryman, Gary Paul
• Primary Examiner(s): Diacou, Ari M
• Application Number:
  US13/194,639
• Time in Patent Office: 1,250 Days
• Field of Search: 372/99, 372/29.014, 372/29.021
• US Class Current: 372/99
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 7/4808 Evaluating distance, position or velocity data
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/4916 using self-mixing in the laser cavity
• CPC Class Codes: G01S 7/4918 Controlling received signal intensity, gain or exposure of sensor
• CPC Class Codes: G01S 7/51 Display arrangements
• CPC Class Codes: H01S 3/0014 Monitoring arrangements not otherwise provided for photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003
• CPC Class Codes: H01S 3/08 Construction or shape of optical resonators or components thereof
• CPC Class Codes: H01S 3/105 by controlling the mutual position or the reflecting properties of the reflectors of the cavity , e.g. by controlling the cavity lengthH01S3/10076, H01S3/13 take precedence
• CPC Class Codes: H01S 3/115 using intracavity electro-optic devices
• CPC Class Codes: H01S 3/1306 Stabilisation of the amplitude
• CPC Class Codes: H01S 3/139 by controlling the mutual position or the reflecting properties of the reflectors of the cavity , e.g. by controlling the cavity length

Abstract

The presently disclosed technique presents laser-based method and apparatus for use in remote sensing. In general, objects within a field of view are lased by a long cavity laser apparatus. Returns are detected, captured, and processed to identify actual objects of interest. These can then be communicated to a user. Over time, the actual objects of interest can be auto-tracked.

Claims

1. A laser-based, remote sensing apparatus, comprising:

a long cavity laser comprising;

a gain medium; and

a segmented mirror configured to return electro-magnetic radiation (EMR) emitted from the gain medium to the gain medium;

wherein the long cavity laser is configured to establish a laser beam of the EMR between the long cavity laser and a first object in a field of view (FOV) in response to a reflection of the EMR from the first object;

a detector configured to;

receive EMR from the FOV, the EMR including a reflected portion of the laser beam; and

detect the laser beam based on the reflected portion; and

a controller coupled to the segmented mirror and the detector, and configured to signal the segmented mirror to alter a reflectivity of a portion of the segmented mirror to thereby change an energy level of the laser beam between the long cavity laser and the first object.

2. The laser-based, remote sensing apparatus of claim 1, wherein the controller is further configured to:

determine a first object modulation signature of the first object based on the reflected portion; and

identify the first object based on a comparison of the first object modulation signature to a plurality of modulation signatures.

3. The laser-based, remote sensing apparatus of claim 2, wherein the first object modulation signature is determined by a time series analysis of the reflected portion.

4. The laser-based, remote sensing apparatus of claim 1, wherein the detector comprises a focal plane array.

5. The laser-based, remote sensing apparatus of claim 1, wherein the detector comprises a two-dimensional array of pixels.

6. The laser-based, remote sensing apparatus of claim 1, wherein the controller is further configured to:

determine, based on the reflected portion, a location of the first object within the FOV; and

overlay the location of the first object on a display of the FOV.

7. The laser-based, remote sensing apparatus of claim 1, wherein the controller is configured to aurally communicate a bearing from the apparatus to the first object.

13. The laser-based, remote sensing apparatus of claim 1, wherein the long cavity laser is further configured to establish an additional laser beam of the EMR between the long cavity laser and a second object in the FOV in response to a reflection of the EMR from the second object.

14. The laser-based, remote sensing apparatus of claim 13, wherein the detector is further configured to detect the additional laser beam based on a reflected portion of the additional laser beam.

15. The laser-based, remote sensing apparatus of claim 1, wherein the detector is further configured to:

determine, based on the reflected portion, a first location of the first object within the FOV at a first time; and

determine, based on the reflected portion, a second location of the first object within the FOV at a second time, wherein the second location differs from the first location.

16. The laser-based, remote sensing apparatus of claim 1, wherein the detector comprises an array of pixels, and wherein the detector is further configured to:

determine, based on the reflected portion, a first location of the first object within the FOV at a first time based on a location of the reflected portion on the array of pixels; and

track a change of location of the first object from the first location to a second location based on a change of location of the reflected portion on the array of pixels.

8. A method comprising:

establishing, by a long cavity laser comprising a gain medium and a segmented mirror that is configured to return electro-magnetic radiation (EMR) emitted from the gain medium to the gain medium, a laser beam of the EMR between the long cavity and a first object in a field of view (FOV) in response to a reflection of the EMR from the first object;

receiving EMR from the FOV, the EMR including a reflected portion of the laser beam;

detecting the laser beam based on the reflected portion; and

signaling the segmented mirror to alter a reflectivity of a portion of the segmented mirror to thereby change an energy level of the laser beam between the long cavity laser and the first object.

9. The method of claim 8, further comprising:

determining a first object modulation signature of the first object based on the reflected portion; and

identifying the first object based on a comparison of the first object modulation signature to a plurality of modulation signatures.

10. The method of claim 9, wherein determining the first object modulation signature comprises determining the first object modulation signature by a time series analysis of the reflected portion.

11. The method of claim 8, further comprising:

determining, based on the reflected portion, a location of the first object within the FOV; and

overlaying the location of the first object on a display of the FOV.

12. The method of claim 8, further comprising aurally communicating a bearing from the the long cavity laser to the first object.

17. A laser-based detection system, comprising:

a long cavity laser comprising;

a gain medium; and

a segmented mirror configured to return electro-magnetic radiation (EMR) emitted from the gain medium to the gain medium;

wherein the long cavity laser is configured to establish a laser beam of the EMR between the long cavity laser and an object in a field of view (FOV) in response to a reflection of the EMR from the object;

a detector comprising an array of pixels, and configured to;

receive EMR from the FOV, the EMR including a reflected portion of the laser beam; and

detect the laser beam based on the reflected portion; and

a controller coupled to the detector and configured to determine a location of the object in the FOV based on a location of the reflected portion on the array of pixels.