Camera - Probe Calibration step-by-step guide

Steps of the camera-probe calibration are presented here. The tutorial starts by pressing the Camera-Probe button in the main GUI, as it was presented in the parent RobotCalibrationManual tutorial.

1. Camera - Probe GUI and calibration start

First a new window with all the controls and a section for the calibration results will open.

  • The first thing to check are the values in the red box (number 1).
    • First we determine the Scan size, which determines how far from the current calibration the robot will scan. The scanning will begin (scan size)/2 away from the current calibration. If this is the first time performing this calibration, we should enter 6 mm, however if we are just recalibrating, 4 mm should be fine, to save some time.
    • Step size determines the scanning accuracy. For best results we should select 10 μm, however do not exceed 20 μm, otherwise probing will be inaccurate.
    • Distance from lens Cal point determines the calibration PCB height in mm. Zero is calibrated to vacuum chuck height for bare tapes and core height for core tapes. If the PCB is higher, negative value is expected, if it is lower, positive value is expected. Default values is -1.59, which is the thickness of the calibration PCB when placed on the vacuum chuck.
  • Next we select the robot stage we want to calibrate (number 2).
  • Pressing the Position other stage button will start the other stage placement process. A pop-up window will open, asking if we want to automatically place the other stage.

    If vacuum chuck is in its normal place and the PCB is placed to the labeled spot, we can press Yes. This will automatically position the other stage to the calibration PCB, as shown in the bottom image.

    If we are unsure if this position is correct, or if the calibration PCB is located in a different place, press No. This will open the Camera DIsplay and the Manual Control GUI.

    • To manually position the other stage to the arrow on the PCB, first select the correct Stage (number 1). This is the stage not selected in the main Camera - Probe GUI, under number 2.
    • Select the step size (number 2), for the initial movements, input 100, for more precise movements, input 20, 10 or any smaller number, depending on the desired move accuracy.
    • Each time step size is changed, press the Acquire Control button (number 3), to start controlling the stage.
    • Move around using WASD keys, until the probe is positioned above the arrow. The camera view should look like this in this position.
    • After pressing DONE, the probe will lower to the PCB. The setup should look like in the image about automatic stage placement.
  • The Find Cross and Start Scan button will now enable. Press it.
    • Camera display and Manual Control will open in the same way as in the manual other stage positioning.
    • This time select the stage we want to calibrate and move it until it is positioned directly over the small circle on the calibrating side of the PCB. The view of the camera should be the same as in the bottom picture.

      The cross should be roughly in the center of the circle, but no more than 1 mm off (in real units on the PCB).
    • Press DONE to start the calibration procedure.

2. Calibration process

The calibration process now starts and takes from around 20 min to 120 min to complete, depending on the scanning area and step size.

  • First, the robot will make a couple of small movements and try to move directly over the center of the previously targeted circle. This should take less than a minute.
  • Then the robot will start probing the cross on the PCB by stepping otrhogonaly towards the reference line. We can monitor the progress by using the side cameras, their use is roughly described in Side Cameras. The view of the GUI during calibration is shown on the bottom picture.

    Progress is monitored using a progress bar in the GUI (1). When the center of the line is found in one direction, the knob (2) will turn green for the respective axis. Robot will continue to do a maximum of 50 steps or continue to the end of scanning area, whichever comes first. The resulting offset value is also displayed next to the progress bar.
  • When centers of both lines are found, both knobs will light in green, the robot will finish probing and return to the origin postion.
  • Calibration results will appear in the GUI.

    Values ΔX/m (1) and ΔY/m (2) are the calibration results. These results should be used to update the values in Constants.xml file under StXShiftX and StXShiftY for core tapes and under StXCoShiftX and StXCoShiftY for core tapes. The first X represents the stage number.

3. Starting a new calibration / finishing

Another calibration can be started after the previous has finished by going back to Calibration start. Select the calibration stage and change the parameters as desired and just retake the steps without the need to restart the GUI. After the new calibration is finished, the results will appear in a new row under the results of the first calibration. Number of calibrations is not limited.


Before exiting the calibration GUI, make sure to write down the calibration results. The results are also stored in cameraProbeCalibration in TapeTesterResources/, but will be wiped when the main Tape Tester program is restarted. To exit the calibration simply close the calibration GUI. For the calibration to take effect, write the new values to Constants.xml file and restart the main Tape Tester program. You can also continue to use the Tape Tester program without restarting, however old calibration will be in use in such case.

-- MihaMali - 2020-12-28

This topic: Sandbox > TWikiUsers > MihaMali > MihaMaliSandbox > PetalBustapeTestingRobot > RobotCalibrationManual > CameraProbeCalibration
Topic revision: r4 - 2020-12-28 - MihaMali
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