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I have a Keyence barcode scanner that can give me the coordinates of a detected barcode in pixels. I have a 6 DOF robot whose end effector pose I know at any given time. My ultimate goal is to place a new label on top of an existing label that is on a box. I am really looking for (x,y,z,theta) from the sensor and passing it on to the robot. I can work without having the Z values by incorporating sensor to know when to stop exploring in the Z.

I am figuring out how to calibrate this robot end effector to the barcode scanner. AFAIK, the scanner cannot detect a checkerboard pattern.

If I mount a barcode onto a sheet and attach it to the robot and note a set of (pixels,6D pose) readings, how would I figure out the 4x4 transform between the arm and the scanner?

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    $\begingroup$ Which pixel position is the scanner giving you? Center of barcode? Bounding box? $\endgroup$
    – FooTheBar
    Apr 26, 2019 at 8:04
  • $\begingroup$ It gives the center and the four vertices. $\endgroup$
    – trycatch22
    Apr 26, 2019 at 17:52
  • $\begingroup$ How many joints exist between the robot body and the end effector? What is the freedom of each joint? What is the freedom of the end effector? $\endgroup$
    – koverman47
    Apr 26, 2019 at 21:54
  • $\begingroup$ 6 DOF. I haven't decided on the robot yet, but it could be a UR5 or the Meca500 (mecademic.com/products/Meca500-small-robot-arm) The end effector is passive. It'll most probably be a vacuum cup. $\endgroup$
    – trycatch22
    Apr 26, 2019 at 22:50
  • $\begingroup$ are 500g and this tiny workspace enough for the scanner and you labelprinter? $\endgroup$
    – FooTheBar
    Apr 29, 2019 at 8:19

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As the scanner gives you the corner points of a the barcode, you can compute the pose of the scanner relative to the barcode (e.g. with OpenCV and solvePnP) and with that information, run most hand-eye calibration algorithms. The normal checkerboard pattern is also only a tool to easily locate known features on a planar surface so there is no big difference between using the corners of the checkerboard or the corners of you barcode.

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  • $\begingroup$ This is useful. Thanks. A couple of questions. The input parameters for it are: objectPoints – Array of object points in the object coordinate space, imagePoints – Array of corresponding image points, cameraMatrix - Input camera matrix Say, I collected a dozen points of the barcode center and the corresponding four vertices. I assume those would be the imagePoints (2x12). What would the objectPoints be? the corresponding translation of the robot's end effector pose? and how do I determine the cameraMatrix? Thanks once again for your response $\endgroup$
    – trycatch22
    Apr 29, 2019 at 18:48
  • $\begingroup$ You should put that in a separate question as it's no longer restricted to the barcode-camera calibration but is a general question of hand-eye calibration. $\endgroup$
    – FooTheBar
    Apr 30, 2019 at 7:15

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