THREE DIMENSIONAL SHAPE CORRELATOR

• US 20080273210A1
• Filed: 10/29/2007
• Published: 11/06/2008
• Est. Priority Date: 04/12/2007
• Status: Active Grant

• Current Assignee: US of A As Represented By The Secretary of The Navy
• Original Assignee: US of A As Represented By Secretary of The Navy
• Inventors: Hilde, Jeffrey J.
• Granted Patent: US 7,616,817 B2
• Time in Patent Office: Days
• US Class Current: 356/601
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G06V 10/255 Detecting or recognising potential candidate objects based on visual cues, e.g. shapes
• CPC Class Codes: G06V 20/64 Three-dimensional objects

Abstract

A three dimensional shape correlation computer software program which uses laser radar data for target identification. The correlation program obtains a scan of laser radar data of a target from a Ladar sensor. The data includes a plurality of X,Y,Z coordinate detection points for the target. The software simulates the sensor scan using a 3D wire-frame model of the target. An X,Y,Z coordinate location is computed for every point in the computer model of the target. The software compares the X,Y,Z coordinate detection points for the target with the X,Y,Z coordinate points for the computer model to determine if the points match. When there is a match a target identification is declared.

Claims

1. A method for recognizing and identifying a target comprising the steps of:

(a) generating a three dimensional shape of said target by scanning a surface of said target and measuring three dimensional points on the surface of said target, wherein a ladar sensor scans the surface of said target to generate said three dimensional points;

(b) providing an X,Y,Z coordinate for each of said three dimensional points measured on the surface of said target;

(c) generating a plurality of three dimensional models of targets to be identified wherein one of said plurality of three dimensional models has a surface which is a match to the surface of said target which is being scanned by said ladar sensor to identify said target;

(d) providing a modeled X,Y,Z coordinate for each of said three dimensional points on the surface of each of said three dimensional models;

(e) comparing the X,Y,Z coordinate for each of said three dimensional points on the surface of said target to the modeled X,Y,Z coordinate for each of said three dimensional points on the surface of each of said three dimensional models; and

(f) matching the X,Y,Z coordinate for said three dimensional points on the surface of said target to the modeled X,Y,Z coordinate for said three dimensional points on the surface of one of said three dimensional models wherein a match of said target to one of said three dimensional models allows for an identification of said target.

2. The method of claim 1 further comprising the steps of:

(a) generating an actual distance measurement between said ladar sensor and each of said three dimensional points scanned on the surface of said target;

(b) generating a synthesized distance measurement between a computer modeled ladar sensor and each of said three dimensional points on the surface of each of said three dimensional models; and

(c) comparing the actual distance measurement for each of said three dimensional points to the synthesized distance measurement for each of said three dimensional points on the surface of each of said three dimensional models to confirm a positive identification for said target.

3. The method of claim 2 further comprising the step of generating a graphical plot which has a Y-axis illustrating the actual distance measurement between said ladar sensor and each of said three dimensional points scanned on the surface of said target and an X-axis illustrating the synthesized distance measurement between the computer modeled ladar sensor and each of said three dimensional points on the surface of each of said three dimensional models.

4. The method of claim 3 further comprising the step of generating a diagonal line on said graphical plot which indicates a target match whenever the modeled X,Y,Z coordinate for said three dimensional points on the surface of one of said three dimensional models lie on said diagonal line.

5. The method of claim 1 wherein said method accurately identifies a target type at least ninety five out of one hundred times said ladar sensor detects the target.

6. An apparatus for recognizing and identifying a target comprising:

(a) sensor means for scanning a surface of said target to be identified;

(b) means for generating a three dimensional shape of said target from scanning the surface of said target and measuring three dimensional points on the surface of said target;

(c) means for providing an X,Y,Z coordinate for each of said three dimensional points measured on the surface of said target;

(d) model generating means for generating a plurality of three dimensional models of targets to be identified wherein one of said plurality of three dimensional models has a surface which is a match to the surface of said target which is being scanned by said sensor means to identify said target;

(e) means for providing a modeled X,Y,Z coordinate for each three dimensional point on the surface of each of said three dimensional models;

(f) comparison means for comparing the X,Y,Z coordinate for each of said three dimensional points on the surface of said target to the modeled X,Y,Z coordinate for each of said three dimensional points on the surface of each of said three dimensional models; and

(f) target identifying means for matching the X,Y,Z coordinate for said three dimensional points on the surface of said target to the modeled X,Y,Z coordinate for said three dimensional points on the surface of one of said three dimensional models wherein a match of said target to one of said three dimensional models allows for an identification of said target.

7. The apparatus of claim 6 further comprising:

(a) means for generating an actual distance measurement between said sensor means and each of said three dimensional points scanned on the surface of said target;

(b) means for generating a synthesized distance measurement between a computer modeled sensor means and each of said three dimensional points on the surface of each of said three dimensional models; and

(c) means for comparing the actual distance measurement for each of said three dimensional points to the synthesized distance measurement for each of said three dimensional points on the surface of each of said three dimensional models to confirm a positive identification for said target.

8. The apparatus of claim 7 further comprising a graphical plot which has a Y-axis illustrating the actual distance measurement between said sensor means and each of said three dimensional points scanned on the surface of said target and an X-axis illustrating the synthesized distance measurement between the computer modeled sensor means and each of said three dimensional points on the surface of each of said three dimensional models.

9. The apparatus of claim 8 further comprising a diagonal line generated on said graphical plot which indicates a target match whenever the modeled X,Y,Z coordinate for said three dimensional points on the surface of one of said three dimensional models lie on said diagonal line.

10. The apparatus of claim 6 wherein said apparatus accurately identifies a target type at least ninety five out of one hundred times said sensor means detects the target.

11. The apparatus of claim 6 wherein said sensor means measures said X,Y,Z coordinate for each of said three dimensional points on the surface of said target within a one meter standard deviation range noise to less than 0.5 degrees for roll, pitch and yaw, and a position error to less than 20 centimeters.

12. A three dimensional shape correlator apparatus for recognizing and identifying a target comprising:

(a) a ladar sensor for scanning a surface of said target to be identified, wherein a scan of the surface of said target is obtained from a reflection of a laser beam from the surface of said target which is detected by said ladar sensor, said ladar sensor responsive to said scan of the surface of said target generating ladar data which includes a three dimensional shape of said target and measurements of three dimensional points on the surface of said target;

(b) a navigation unit for receiving said ladar data from said ladar sensor, said navigation unit processing said ladar data to provide an X,Y,Z coordinate for each of said three dimensional points measured on the surface of said target by said ladar sensor;

(c) a digital processor for generating a plurality of three dimensional models of targets to be identified wherein one of said plurality of three dimensional models includes a surface which is a match to the surface of said target which is being scanned by said ladar sensor to identify said target;

(d) said digital processor providing a modeled X,Y,Z coordinate for each three dimensional point on the surface of each of said three dimensional models;

(e) said digital processor comparing the X,Y,Z coordinate for each of said three dimensional points on the surface of said target to the modeled X,Y,Z coordinate for each of said three dimensional points on the surface of each of said three dimensional models; and

(f) said digital processor matching the X,Y,Z coordinate for said three dimensional points on the surface of said target to the modeled X,Y,Z coordinate for said three dimensional points on the surface of one of said three dimensional models wherein a match of said target to one of said three dimensional models allows for an identification of said target.

13. The three dimensional shape correlator apparatus of claim 12 further comprising a ladar transmitter for generating said laser beam which is used to scan the surface of said target and providing a plurality of pixels points on the surface of said target, wherein each pixel point represents one three dimensional point on the surface of said target.

14. The three dimensional shape correlator apparatus of claim 12 wherein said navigation unit computes the X,Y,Z coordinates for each of said three dimensional points on the surface of said target in accordance with the following equation:

$\lfloor <br><br>\begin{array}{c}X\\ Y\\ Z\end{array}\rfloor <br><br>=\lfloor <br><br>\begin{array}{ccc}T<br><br><br><br>11& T<br><br><br><br>12& T<br><br><br><br>13\\ T<br><br><br><br>21& T<br><br><br><br>22& T<br><br><br><br>23\\ T<br><br><br><br>31& T<br><br><br><br>32& T<br><br><br><br>33\end{array}\rfloor <br><br>\times <br><br>\lfloor <br><br>\begin{array}{c}x\\ y\\ z\end{array}\rfloor <br><br>\times <br><br>\mathrm{Range}+\lfloor <br><br>\begin{array}{c}\mathrm{PositionX}\\ \mathrm{PositionY}\\ \mathrm{PositionZ}\end{array}\rfloor <br><br>$

wherein X,Y,Z are coordinates for each of said pixel points on the surface of said target as measured by said ladar sensor;

the matrix which contains elements T11, T12, T13, T21, T22, T23, T31, T32 and T33, is a three dimensional rotation matrix;

the matrix which contains vector elements x,y,z represents the x,y,z components of a direction vector for each of said pixel points on the surface;

Range is measured by said ladar sensor; and

the matrix containing elements PositionX, PositionY, PositionZ defines a location for said ladar sensor.

15. The three dimensional shape correlator apparatus of claim 12 wherein the ladar data generated by said ladar sensor is used by said three dimensional shape correlator apparatus to calculate an actual distance measurement between said ladar sensor and each of said three dimensional points scanned on the surface of said target, and said digital processor generates a synthesized distance measurement between a computer modeled sensor means and each of said three dimensional points on the surface of each of said three dimensional models.

16. The three dimensional shape correlator apparatus of claim 15 wherein said digital processor compares the actual distance measurement for each of said three dimensional points to the synthesized distance measurement for each of said three dimensional points on the surface of each of said three dimensional models to confirm a positive identification for said target.

17. The three dimensional shape correlator apparatus of claim 15 further comprising a monitor connected to said digital processor for viewing a graphical plot which has a Y-axis illustrating the actual distance measurement between said ladar sensor and each of said three dimensional points scanned on the surface of said target and an X-axis illustrating the synthesized distance measurement between a computer modeled ladar sensor and each of said three dimensional points on the surface of each of said three dimensional models.

18. The three dimensional shape correlator apparatus of claim 17 further comprising a diagonal line generated on said graphical plot which indicates a target match whenever the modeled X,Y,Z coordinate for said three dimensional points on the surface of one of said three dimensional models lie on said diagonal line.

19. The three dimensional shape correlator apparatus of claim 12 wherein said apparatus accurately identifies a target type at least ninety five out of one hundred times said sensor means detects the target.

20. The apparatus of claim 12 wherein said ladar sensor measures said X,Y,Z coordinate for each of said three dimensional points on the surface of said target within a one meter standard deviation range noise to less than 0.5 degrees for roll, pitch and yaw, and a position error to less than 20 centimeters.