AUTOMATED LOCAL POSITIONING SYSTEM CALIBRATION USING OPTICALLY READABLE MARKERS

• US 20180160050A1
• Filed: 02/06/2018
• Published: 06/07/2018
• Est. Priority Date: 04/09/2015
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Fetzer, Barry A., Troy, James J., Georgeson, Gary E.
• Granted Patent: US 10,791,276 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G06T 2207/10152 Varying illumination
• CPC Class Codes: G06T 2207/20224 Image subtraction
• CPC Class Codes: G06T 2207/30204 Marker
• CPC Class Codes: G06T 7/174 involving the use of two or more images
• CPC Class Codes: G06T 7/73 using feature-based methods
• CPC Class Codes: G06V 10/245 by locating a pattern; Special marks for positioning
• CPC Class Codes: G06V 20/10 Terrestrial scenes scenes under surveillance with static cameras G06V20/52; scenes perceived from the exterior of a vehicle G06V20/56; scenes perceived from the interior of a vehicle G06V20/59
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming

Abstract

An improved mechanism for calibrating a local positioning system through the use of passive or retro-reflective markers is described herein. A plurality of imaging targets with the passive or retro-reflective markers may be attached or affixed on a surface of an object. The local positioning system may then capture a first image of the imaging targets in a non-illuminated state and further capture a second image of the imaging targets in an illuminated state. A difference image between the first and second captured images may be computed and then segmented. The local positioning system may then identify the plurality of imaging targets based on the segmented difference image and position itself to extract information. The extracted information may then be used to help calibrate the local positioning system.

Claims

1. A method of controlling a mobile platform having a local positioning system, comprising:

capturing a first image of a plurality of imaging targets (130-132) in a first state of illumination from a location, wherein the imaging targets are on a surface of an object;

capturing, from the location, a second image of the plurality of imaging targets (130-132) in a second state of illumination;

locating a center point of each of the plurality of imaging targets based on a difference image (300) generated using the captured first image and the captured second image;

acquiring a distance reading based on a distance measurement from the center point of each of the plurality of imaging targets (130-132) and a local positioning system (120) of the mobile platform; and

controlling movement of the mobile platform at least in part based upon the acquired distance reading.

2. The method of claim 1, wherein controlling the movement of the mobile platform at least in part based upon the acquired distance reading comprises controlling a direction of the mobile platform at least in part based upon the acquired distance reading.

3. The method of claim 2, wherein controlling the direction of the mobile platform at least in part based upon the acquired distance reading comprises controlling the direction of the mobile platform to aim at an object of interest based at least in part upon the acquired distance reading.

4. The method of claim 3, wherein:

the method further comprises extracting information (500) from each of the plurality of imaging targets; and

controlling a movement of the mobile platform at least in part based upon the acquired distance reading comprises controlling a movement of the mobile platform at least in part based upon the extracted information and acquired distance reading.

5. The method of claim 4, wherein controlling the movement of the mobile platform at last in part based upon the extracted information and the acquired distance reading comprises calibrating the local positioning system (120) based on the extracted information and the acquired distance reading.

6. The method of claim 1, further comprising:

extracting information (500) from each of the plurality of imaging targets, the information related to a position of the center point on the surface of each of the plurality of the imaging targets.

7. The method of claim 6, wherein the information related to the position of the center point is represented in three dimensional coordinates.

8. The method of claim 6, wherein the information is stored in a machine-readable code.

9. The method of claim 6, wherein the information from each of the plurality of imaging targets is extracted by adjusting a field of view of the local positioning system to zoom into a center region of each of the plurality of imaging targets.

10. The method of claim 9, wherein adjusting the field of view of the local positioning system to zoom into the center region of each of the plurality of imaging targets further comprises:

acquiring a close-up image of the center region of each of the plurality of imaging targets;

reading a machine-readable label from the close-up image; and

in response to reading the machine-readable label and not being able to decode the machine-readable label into a usable format, capturing an additional first image of a plurality of imaging targets in a non-illuminated state and an additional second image of the plurality of imaging targets in an illuminated state to generate an additional difference image.

11. The method of claim 1, wherein capturing the first image of the plurality of imaging targets in a first state of illumination from the location comprises capturing the first image while under no illumination, and wherein capturing, from the location, the second image of the plurality of imaging targets in the second state of illumination comprises illuminating at least a portion of a surface of the imaging targets and capturing the second image under the illumination.

12. The method of claim 1, further comprising calibrating the local positioning system at least in part by computing a relative position and orientation offset between the local positioning system and the plurality of imaging targets.

13. The method of claim 1, further comprising generating a difference image (300) using the captured first image and the captured second image, comprising:

determining whether a sufficient number of imaging targets are captured; and

in response to determining that a sufficient number of imagining targets are not found, aiming the local positioning system to a new region to acquire an additional first image of a plurality of imaging targets in the first state of illumination, and an additional second image of the plurality of imaging targets in the second state of illumination different from the first state of illumination to generate an additional difference image.

14. A system, comprising:

a processor;

a memory, communicatively coupled to the processor, the memory storing processor instructions comprising instructions for;

capturing a first image of a plurality of imaging targets (130-132) in a first state of illumination from a location, wherein the imaging targets are on a surface of an object;

capturing from the location, a second image of the plurality of imaging targets (130-132) in a second state of illumination;

locating a center point of each of the plurality of imaging targets based on a difference image (300) generated using the captured first image and the captured second image;

acquiring a distance reading based on a distance measurement from the center point of each of the plurality of imaging targets (130-132) and a local positioning system (120) of the mobile platform; and

controlling movement of the mobile platform at least in part based upon the acquired distance reading.

15. The system of claim 14, wherein the processor instructions for controlling the movement of the mobile platform at least in part based upon the acquired distance reading comprise processor instructions for controlling a direction of the mobile platform at least in part based upon the acquired distance reading.

16. The system of claim 15, wherein the processor instructions for controlling the direction of the mobile platform at least in part based upon the acquired distance reading comprise processor instructions for controlling the direction of the mobile platform to aim at an object of interest based at least in part upon the acquired distance reading.

17. The system of claim 16, wherein:

the processor instructions further comprise processor instructions for extracting information (500) from each of the plurality of imaging targets; and

the processor instructions for controlling a movement of the mobile platform at least in part based upon the acquired distance reading comprise processor instructions for controlling a movement of the mobile platform at least in part based upon the extracted information and acquired distance reading.

18. The system of claim 14, wherein the processor instructions further comprise processor instructions for:

extracting information (500) from each of the plurality of imaging targets, the information related to a position of the center point on the surface of each of the plurality of the imaging targets.

19. The system of claim 18, wherein the information related to the position of the center point is represented in three dimensional coordinates.

20. The system of claim 18, wherein the information is stored in a machine-readable code.

21. The system of claim 18, wherein the information from each of the plurality of imaging targets is extracted by adjusting a field of view of the local positioning system to zoom into a center region of each of the plurality of imaging targets.

22. The system of claim 21, wherein the processor instructions for adjusting the field of view of the local positioning system to zoom into the center region of each of the plurality of imaging targets further comprise processor instructions for:

acquiring a close-up image of the center region of each of the plurality of imaging targets;

reading a machine-readable label from the close-up image; and

in response to reading the machine-readable label and not being able to decode the machine-readable label into a usable format, capturing an additional first image of a plurality of imaging targets in a non-illuminated state and an additional second image of the plurality of imaging targets in an illuminated state to generate an additional difference image.

23. The system of claim 14, wherein:

the processor instructions for capturing the first image of the plurality of imaging targets in a first state of illumination from the location comprise processor instructions for capturing the first image while under no illumination, and

the processor instructions for capturing, from the location, the second image of the plurality of imaging targets in the second state of illumination comprise processor instructions for illuminating at least a portion of a surface of the imaging targets and capturing the second image under the illumination.

24. The system of claim 14, wherein the processor instructions further comprise processor instructions for calibrating the local positioning system at least in part by computing a relative position and orientation offset between the local positioning system and the plurality of imaging targets.

25. The system of claim 14, wherein the processor instructions further comprise processor instructions for generating a difference image (300) using the captured first image and the captured second image, comprising processor instructions for:

determining whether a sufficient number of imaging targets are captured; and

in response to determining that a sufficient number of imagining targets are not found, aiming the local positioning system to a new region to acquire an additional first image of a plurality of imaging targets in the first state of illumination, and an additional second image of the plurality of imaging targets in the second state of illumination different from the first state of illumination to generate an additional difference image.

26. A system, comprising:

one or more memories having stored thereon computer-readable instructions that, upon execution by a computing device, cause the system to;

capture a first image of a plurality of imaging targets (130-132) in a first state of illumination from a location, wherein the imaging targets are on a surface of an object;

capture from the location, a second image of the plurality of imaging targets (130-132) in a second state of illumination;

locate a center point of each of the plurality of imaging targets based on a difference image (300) generated using the captured first image and the captured second image;

acquire a distance reading based on a distance measurement from the center point of each of the plurality of imaging targets (130-132) and a local positioning system (120) of the mobile platform; and

control movement of the mobile platform at least in part based upon the acquired distance reading.