System and method for determination of object volume with multiple three-dimensional sensors

{
  "publication_number": "US10074191B1",
  "country": "US",
  "kind": "B1",
  "title": "System and method for determination of object volume with multiple three-dimensional sensors",
  "abstract": "A system and method for determining volume of a runtime object with a vision system is provided. A plurality of vision sensors are arranged so that the fields of view (FOVs) of the plurality of vision sensors collectively view features associated with volume determination of a runtime object. Each of the displacement sensors generates range images from sequences of analyzed images, each producing a single row of the range image. An ignoring volume is subtracted from the measured range image based upon one or more dividing planes as they appear in the viewing/imaging perspective of each displacement sensor. Negative subtraction results are substantially nulled. The resulting representative range images are used to calculate the volume of a portion of the object, as sectioned by the diving planes. Each volume result is summed/added to derive the overall summed volume of the runtime object.",
  "claims": [
    "1. A method for determining volume of a runtime object with a vision system comprising the steps of: arranging a plurality of vision sensors so that fields of view (FOVs) of the plurality of vision sensors collectively view features associated with volume determination of the object; acquiring with each of the displacement sensors a respective runtime image and deriving therefrom a respective measured range image; subtracting an ignoring volume based upon one or more dividing planes associated with each of the displacement sensors from the respective measured range images, with negative subtraction results being substantially nulled, to derive a respective volume result for each of the displacement sensors; and adding each volume result to derive the overall summed volume of the runtime object.",
    "2. The method as set forth in claim 1 wherein at least one of the dividing planes is established based upon a calibration process in which a range image is acquired by each of the displacement sensors and geometric features of a calibration object are used to define the at least one of the dividing planes.",
    "3. The method as set forth in claim 2 wherein the displacement sensors are laser displacement sensors.",
    "4. The method as set forth in claim 3 wherein the runtime object and the displacement sensors are in relative motion with respect to each other and motion information is transmitted to the displacement sensors related to the relative motion.",
    "5. The method as set forth in claim 1 wherein the step of arranging includes locating at least one of the displacement sensors to image a top side of the object and locating at least one of the vision sensors to image an opposing bottom side of the object, including providing a region with respect to the bottom side through which light passes.",
    "6. The method as set forth in claim 1 wherein the runtime object is located on a supporting operating surface that defines one of the dividing planes that is established based upon a calibration process in which a range image is acquired by each of the displacement sensors and geometric features of the operating surface are used to define the at least one of the dividing planes.",
    "7. The method as set forth in claim 1 wherein the dividing planes are oriented, and intersect, such that they divide the physical space into a predetermined number of partitions, wherein within any non-enclosed partition containing a portion of the runtime object a sensor positioned so that a predetermined portion of a surface of the runtime object is visible to the sensor and partitions that are free of a portion of the runtime object are thereby free of coverage by one of the displacement sensors and contribute no value to the overall summed volume.",
    "8. The method as set forth in claim 7 wherein the dividing planes are oriented and intersect such that one or more enclosed partitions are created which lie entirely within the runtime object and the overall summed volume is calculated as a sum of the volumes calculated by the each of the displacement sensors and geometrically calculated volumes of the enclosed partitions.",
    "9. The method as set forth in claim 1 wherein the runtime object includes undercut surfaces not visible to the FOV of a single displacement sensor.",
    "10. The method as set forth in claim 1 further comprising transmitting the overall summed volume to a monitoring or utilization system.",
    "11. The method as set forth in claim 10 wherein the monitoring or utilization system receiving the overall summed volume continually based on a specified scan distance, the scan distance being based on at least one of physical distance, time and relative motion information between the runtime object and the displacement sensors.",
    "12. The method as set forth in claim 10 wherein the monitoring or utilization system receives the overall summed volume as successive volume measurements.",
    "13. The method as set forth in claim 10 wherein the monitoring or utilization system compares volume measurements based on the transmitted overall summed volume to predetermined expected values and signals when a compared volume measurement is at least one of within, inside or outside a predetermined tolerance.",
    "14. The method as set forth in claim 10 wherein the monitoring or utilization system receives the overall summed volume continually based on a specified scan distance, the scan distance being based on at least one of physical distance, time and relative motion information between the runtime object and the displacement sensors, the received overall summed volume providing an indication of a portion on the runtime object.",
    "15. The method as set forth in claim 14 wherein the monitoring or utilization system physically or virtually slices the object at a location relative to the portion.",
    "16. The method as set forth in claim 10 wherein the monitoring or utilization system receives the overall summed volume based on a scan of the object by the plurality of displacement sensors that is mapped to a coordinate system with respect to geometry of the object.",
    "17. The method as set forth in claim 16 wherein the monitoring or utilization system physically or virtually slices the object at a location relative to the coordinate system with respect to the geometry of the object.",
    "18. A system for determining volume of a runtime object with a vision system comprising: a plurality of vision sensors arranged so that fields of view (FOVs) of the plurality of vision sensors collectively view features associated with volume determination of the object and acquire a respective runtime image, used to derive therefrom a respective measured range image; and a vision processor that subtracts an ignoring volume based upon one or more dividing planes associated with each of the displacement sensors from the respective measured range images, with negative subtraction results being substantially nulled, to derive a respective volume result for each of the displacement sensors and that adds each volume result to derive the overall summed volume of the runtime object.",
    "19. The system as set forth in claim 18 wherein at least one of the dividing planes is established based upon a calibration process in which a range image is acquired by each of the displacement sensors and geometric features of a calibration object are used to define the at least one of the dividing planes.",
    "20. The system as set forth in claim 19 wherein the displacement sensors are laser displacement sensors.",
    "21. The system as set forth in claim 18 wherein the runtime object is in relative motion with respect to the displacement sensors on an operating surface comprising a conveyor.",
    "22. The system as set forth in claim 18 wherein the runtime object is located on a supporting operating surface that defines one of the dividing planes that is established based upon a calibration process in which a range image is acquired by each of the displacement sensors and geometric features of the operating surface are used to define the at least one of the dividing planes."
  ],
  "description_excerpt": "This invention relates to machine vision systems used in determining the volume of an imaged object surface using a three-dimensional (3D) sensor.\n\nIn manufacturing and assembly processes, it is often desirable to analyze an object surface to determine the nature of features and/or irregularities. The displacement (or “profile”) of the object surface can be determined using a machine vision system (also termed herein “vision system”) in the form of a laser displacement sensor (also termed a laser beam “profiler”). A laser displacement sensor captures and determines the (three dimensional) profile of a scanned object surface using a planar curtain or “fan” of a laser beam at a particular plane transverse to the beam propagation path. In a conventional arrangement, a vision system camera assembly is oriented to view the plane of the beam from outside the plane. This arrangement captures the profile of the projected line (e.g. extending along the physical x-axis) on the object surface, which, due to the baseline (i.e. the relative spacing along the y-axis) between the beam (fan) plane and the camera causes the imaged line to appear as varying in the image y-axis direction as a function of the physical z-axis height of the imaged point (along the image x-axis). This deviation represents the profile of the surface. Laser displacement sensors are useful in a wide range of inspection and manufacturing operations where the user desires to measure and characterize surface details of a scanned object via triangulation.",
  "cpc": [
    "G06T 7/62",
    "G01B 11/00",
    "G01B 11/245",
    "G01B 11/25",
    "G01B 11/2518",
    "G01B 2210/52",
    "G01S 17/87",
    "G01S 17/89",
    "G06T 2207/10012",
    "G06T 2207/10028",
    "G06T 2207/20224",
    "G06T 2207/30164",
    "G06T 7/0004",
    "G06T 7/0081",
    "G06T 7/194",
    "G06T 7/602"
  ],
  "ipc": [
    "G01B 11/25",
    "G01S 17/87",
    "G01S 17/89",
    "G06K 9/32",
    "G06T 7/00",
    "G06T 7/60",
    "G06T 7/62"
  ],
  "assignees": [
    "Cognex Corp"
  ],
  "inventors": [
    "Matthew R. Reome",
    "Mark D. Johnson",
    "Mikhail Akopyan"
  ],
  "filing_date": "2016-06-27",
  "publication_date": "2018-09-11",
  "grant_date": "2018-09-11",
  "priority_date": "2015-07-05",
  "application_number": "US-201615193665-A",
  "family_id": "63406482",
  "cited_by_count": 25,
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}