Non-contact passive ranging system

• US RE45,122 E1
• Filed: 08/15/2013
• Issued: 09/09/2014
• 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
• Primary Examiner(s): CONWAY, THOMAS A
• Application Number:
  US13/987,621
• Time in Patent Office: 390 Days
• Field of Search: None
• 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 optical motion sensor on a platform focused on a first object;

a second optical motion sensor on the platform also focused on the first object;

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

processing circuitry responsive to an output of the first optical motion sensor and an output of the second optical motion sensor as relative motion is provided between the platform and the first object and configured to calculate the distance from the platform to the object based on a slower velocity different velocity output by the first optical motion sensor than the second optical motion sensor and based on the different optical path lengths of the first and second optical motion sensors.

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

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

4. The system of claim 1 in which the distance between the first and second optical motion sensors is predetermined.

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

6. The system of claim 5 in which the processing circuitry is responsive to an output of the third optical motion sensor and an output of the fourth optical motion sensor 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 optical motion sensor and a sixth optical motion sensor both focused on a third object, the optical path from the third object to the fifth optical motion sensor shorter than the optical path from the third object to the sixth optical motion sensor.

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

11. The system of claim 9 in which the processing circuitry is responsive to an output of the fifth optical motion sensor and an output of the sixth optical motion sensor 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.

12. The system of claim 11 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.

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

focusing a first optical motion sensor on the platform at the object;

focusing a second optical motion sensor on the platform at the same object;

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

providing relative motion between the platform and the object; and

calculating the distance from the platform to the object based on a slower velocity different velocity output by the first optical motion sensor than the second optical motion sensor and based on the different optical path lengths of the first and second optical motion sensors.

14. The method of claim 13 in which the distance between the first and second optical motion sensors is predetermined.

15. The method of claim 13 in which providing relative motion includes moving the platform.

16. The method of claim 15 in which the first optical motion sensor outputs a first velocity x_A of the platform and the second optical motion sensor 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 optical motion sensors on the platform.