Non-contact passive ranging system

• US 20090141942A1
• Filed: 12/03/2007
• Published: 06/04/2009
• Est. Priority Date: 12/03/2007
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: DeBitetto, Paul, Zervoglos, Nicholas, Rasmussen, Scott
• Granted Patent: US 8,194,928 B2
• Time in Patent Office: Days
• US Class Current: 382/106
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves

Abstract

A non-contact passive ranging system wherein a first imager on a platform is focused on a first object and a second imager on the platform is also focused on the first object. The optical path from the first object to the first imager is configured to be shorter than the optical path from the object to the second imager. Processing circuitry is responsive to an output of the first imager and an output of the second imager as relative motion is provided between the platform and the first object and is configured to calculate the distance from the platform to the object.

Claims

1. A non-contact passive ranging system comprising:

a first imager on a platform focused on a first object;

a second imager on the platform also focused on the first object;

the optical path from the first object to the first imager shorter than the optical path from the object to the second imager; and

processing circuitry responsive to an output of the first imager and an output of the second imager as relative motion is provided between the platform and the first object and configured to calculate the distance from the platform to the object.

2. The system of claim 1 in which each imager is an optical motion sensor each outputting a velocity.

3. The system of claim 1 in which the platform is mobile.

4. The system of claim 1 in which there is a beam splitter in the optical path of both the first and second imagers.

5. The system of claim 1 in which there is a third imager and a fourth imager on the platform both focused on a second object, the optical path from the second object to the third imager shorter than the optical path from the second object to the fourth imager.

6. The system of claim 5 in which the processing circuitry is responsive to an output of the third imager and an output of the fourth imager as relative motion is provided between the platform and the second object and configured to calculate the distance from the platform to the second object.

7. The system of claim 6 in which the processing circuitry is further configured to calculate the linear velocity of the platform.

8. The system of claim 7 in which the processing circuitry is further configured to calculate the angular velocity of the platform.

9. The system of claim 5 in which there is a fifth imager and a sixth imager both focused on a third object, the optical path from the third object to the fifth imager shorter than the optical path from the third object to the sixth imager.

10. The system of claim 9 in which the processing circuitry is responsive to an output of the fifth imager and an output of the sixth imager as relative motion is provided between the platform and the third object and configured to calculate the distance from the platform to the third object.

11. The system of claim 10 in which the processing circuitry is further configured to calculate the velocity of the platform in more than one direction and the angular velocity of the platform about more than one axis.

12. The system of claim 9 in which the optical axes of the fifth and sixth imagers are orthogonal to the optical axes of the third and fourth imagers which are orthogonal to the optical axes of the first and second imagers.

13. A non-contact passive ranging system comprising:

a first optical motion sensor on a platform focused on an object;

a second optical motion sensor on the platform focused on the same object;

the optical path from the object to the first optical motion sensor shorter than the optical path from the object to the second optical motion sensor; and

processing circuitry responsive to outputs of the first and second optical motion sensors as relative motion is provided between the platform and the object configured to calculate the distance from the platform to the object.

14. A method of determining the distance between a platform and an object, the method comprising:

focusing a first imager on the platform at the object;

focusing a second imager on the platform at the same object;

arranging the optical path from the first object to the first imager to be shorter than the optical path from the object to the second imager;

providing relative motion between the platform and the object; and

calculating the distance from the platform to the object based on reference and sample frames imaged by the first and second imagers.

15. The method of claim 14 in which providing relative motion includes moving the platform.

16. The method of claim 15 in which the first imager outputs a first velocity x_A of the platform and the second imager outputs second velocity x_B of the platform.

17. The method of claim 16 in which calculating the distance h is a function of x_A, x_B and the position of the first and second imagers on the platform.