Draw wire encoder based homography

Patent metadata

Field	Value
Publication number	US-11023741-B1
Application number	US-202017104430-A
Country	US
Kind code	B1
Filing date	Nov 25, 2020
Priority date	Oct 25, 2019
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

A sensor calibration system configured to receive a first frame of one or more markers on a repositionable platform at a first location within a space from a sensor. The system is further configured to determine pixel locations in the first frame for a first marker and a second marker from among the one or more markers. The system is further configured to receive distance information that corresponds with a distance between the platform and distance measuring devices. The system is further configured to determine (x,y) coordinates for the first marker and the second marker based on the distance information. The system is further configured to generate a homography based on the (x,y) coordinates and pixel locations of the first marker and the second marker. The homography includes coefficients that translate between pixel locations in the first frame of the sensor and (x,y) coordinates in the global plane.

First claim

The invention claimed is:

1. A sensor calibration system, comprising:
a platform, wherein:
the platform is repositionable within a space; and
the platform comprises one or more markers;

a first distance measuring device operably coupled to the platform, wherein:
the first distance measuring device is configured to output a first distance; and
the first distance corresponds with a distance between the platform and the first distance measuring device;

a second distance measuring device operably coupled to the platform, wherein:
the second distance measuring device is configured to output a second distance; and
the second distance corresponds with a distance between the platform and the second distance measuring device;

a sensor configured to capture frames of a global plane in the space, wherein:
the global plane represents (x,y) coordinates for the at least a portion of the space;
each frame comprises a plurality of pixels; and
each pixel from the plurality of pixels is associated with a pixel location comprising a pixel row and a pixel column; and

a tracking system operably coupled to the sensor, the first distance measuring device, and the second distance measuring device, comprising:
one or more memories operable to store a homography associated with the sensor, wherein:
the homography comprises coefficients that translate between pixel locations in the first frame and (x,y) coordinates in the global plane; and

one or more processors operably coupled to the one or more memories, configured to:
receive a first frame of the one or more markers at a first location within the space from the sensor;
determine a first pixel location in the first frame for a first marker from among the one or more markers, wherein the first pixel location comprises a first pixel row and a first pixel column of the first frame;
determine a first (x,y) coordinate for the first marker at the first location within the space based on the first distance and the second distance, wherein the first (x,y) coordinate identifies a first x-value and a first y-value in the global plane corresponding with the first location;
determine a second pixel location in the first frame for a second marker from among the one or more markers, wherein the second pixel location comprises a second pixel row and a second pixel column of the first frame;
determine a second (x,y) coordinate for the second marker at the first location within the space based on the first distance and the second distance, wherein the second (x,y) coordinate identifies a second x-value and a second y-value in the global corresponding with the second location; and
generate the homography based on the first (x,y) coordinate, the second (x,y) coordinate, the first pixel location, and the second pixel location.

2. The system of claim 1 , wherein:
the first distance measuring device is a first draw wire encoder comprising:
a first housing;
a first retractable wire disposed within the first housing; and
a first encoder configured to determine the first distance corresponding with an amount of the first retractable wire that extends outside of the first housing;

the second distance measuring device is a second draw wire encoder comprising:
a second housing;
a second retractable wire disposed within the second housing; and
a second encoder configured to determine a second distance corresponding with an amount of the second retractable wire that extends outside of the second housing.

3. The system of claim 1 , wherein the platform is configured to adjust a height of the one or more markers within the space.

4. The system of claim 1 , wherein the platform further comprises a plurality of wheels configured to reposition the platform within the space.

5. The system of claim 1 , wherein determining the first (x,y) coordinate for the first marker at the first location comprises:
sending a first data request to the first distance measuring device;
receiving the first distance from the first distance measuring device when the first marker is located at the first location in response to sending the first data request;
sending a second data request to the second distance measuring device; and
receiving the second distance from the second distance measuring device when the first marker is located at the first location in response to sending the second data request.

6. The system of claim 1 , wherein the first (x,y) coordinate for the first marker at the first location is a function of the first distance and the second distance.

7. The system of claim 1 , wherein the global plane is parallel with a floor of the space.

8. The system of claim 1 , wherein the one or more processors are further configured to store an association between the sensor and the homography.

9. A sensor calibration method, comprising:
positioning a platform within a space, wherein:
the platform is repositionable within the space; and
the platform comprises one or more markers;

receiving a first frame of the one or more markers at a first location within the space from a sensor, wherein the sensor is configured to capture frames of a global plane in the space, wherein:
the global plane represents (x,y) coordinates for the at least a portion of the space;
each frame comprises a plurality of pixels; and
each pixel from the plurality of pixels is associated with a pixel location comprising a pixel row and a pixel column;

determining a first pixel location in the first frame for a first marker from among the one or more markers, wherein the first pixel location comprises a first pixel row and a first pixel column of the first frame;
receiving a first distance from a first distance measuring device, wherein the first distance corresponds with a distance between the platform and the first distance measuring device;
receiving a second distance from a second distance measuring device, wherein the second distance corresponds with a distance between the platform and the second distance measuring device;
determining a first (x,y) coordinate for the first marker at the first location within the space based on the first distance and the second distance, wherein the first (x,y) coordinate identifies a first x-value and a first y-value in the global plane corresponding with the first location;
determining a second pixel location in the first frame for a second marker from among the one or more markers, wherein the second pixel location comprises a second pixel row and a second pixel column of the first frame;
determining a second (x,y) coordinate for the second marker at the first location within the space based on the first distance and the second distance, wherein the second (x,y) coordinate identifies a second x-value and a second y-value in the global corresponding with the second location; and
generating a homography based on the first (x,y) coordinate, the second (x,y) coordinate, the first pixel location, and the second pixel location, wherein the homography comprises coefficients that translate between pixel locations in the first frame and (x,y) coordinates in the global plane.

10. The method of claim 9 , wherein:
the first distance measurement device is a first draw wire encoder comprising:
a first housing;
a first retractable wire disposed within the first housing; and
a first encoder configured to determine the first distance corresponding with an amount of the first retractable wire that extends outside of the first housing;

the second distance measurement device is a second draw wire encoder comprising:
a second housing;
a second retractable wire disposed within the second housing; and
a second encoder configured to determine a second distance corr

Assignees

• 7 Eleven Inc

Inventors

• Dalal Kyle
• Krishnamurthy Sailesh Bharathwaaj
• Mirza Shahmeer Ali

Classifications

• G06V20/653

  by matching three-dimensional models, e.g. conformal mapping of Riemann surfaces · CPC title

• G06V10/457

  by analysing connectivity, e.g. edge linking, connected component analysis or slices · CPC title

• G06T7/246 Primary

  using feature-based methods, e.g. the tracking of corners or segments · CPC title

• G06V10/25

  Determination of region of interest [ROI] or a volume of interest [VOI] · CPC title

• G06V10/147

  Details of sensors, e.g. sensor lenses (fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19) · CPC title