Changes between Version 15 and Version 16 of Tutorial/GeometricCalibration


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Timestamp:
Dec 9, 2014, 11:41:11 PM (6 years ago)
Author:
sommeria
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  • Tutorial/GeometricCalibration

    v15 v16  
    1717To perform the calibration, press '''APPLY''', first with the default option 'rescale' in '''calib_type'''.  The image is now displayed in phys coordinates. A xml file 'images.xml', containing the calibration parameters and reference point coordinates, has been created in the folder 'UVMAT_DEMO01_pair' (it should be identical with the file 'images.ref.xml' put for reference). [[BR]]Note that the xml file name reproduces the name of the folder containing the images, so that images from different cameras should not be
    1818
    19 [[Image(Calib.jpg)]]
     19[[Image(Calib.JPG)]]
    2020
    2121== Translating the coordinates ==
     
    5656
    5757== Calibration with a target grid ==
    58 Most precise and general calibration relies on the use of a target grid. As an example, open in uvmat the image ima_6 in 'UVMAT_DEMO07_GeometryCalibration/Dalsa1' (accessible on http://servforge.legi.grenoble-inp.fr/pub/soft-uvmat/). Open the menu bar '''Tools/geometric calibration '''and''' '''pick four corner points ABCD with the mouse define the periphery of the phys grid selected for calibration. The first point A will define the phys axis origin while AB defines the x axis and AD the y axis. AB and DC should be parallel on the phys grid (see fig). Then select''' Tools/Detect grid '''on the upper menu bar of''' geometry_calib: '''you get a new GUI '''detect_grid''' in which you define (in phys units) the grid mesh and the positions of the  first and last points on each axis. A z position can be defiend as well, do not fill it in this example. The option white markers is selected (by default) indicating that the grid is white (the opposite option would be needed for a grid made of black crosses on a white background). After validation by '''OK''', the detected grid appears on uvmat (see fig).
     58Most precise and general calibration relies on the use of a target grid. As an example, open in uvmat the image ima_6 in 'UVMAT_DEMO07_GeometryCalibration/Dalsa1' (accessible on http://servforge.legi.grenoble-inp.fr/pub/soft-uvmat/). Open the menu bar '''Tools/geometric calibration '''and''' '''pick four corner points ABCD with the mouse define the periphery of the phys grid selected for calibration. The first point A will define the phys axis origin while AB defines the x axis and AD the y axis. AB and DC should be parallel on the phys grid (see fig). Then select''' !Tools/Detect grid '''on the upper menu bar of''' geometry_calib: '''you get a new GUI '''detect_grid''' in which you define (in phys units) the grid mesh and the positions of the  first and last points on each axis. A z position can be defiend as well, do not fill it in this example. The option white markers is selected (by default) indicating that the grid is white (the opposite option would be needed for a grid made of black crosses on a white background). After validation by '''OK''', the detected grid appears on uvmat (see fig).
    5959
    6060If a  point is not correct, select the option '''[!CheckEnableMouse]''' in '''geometry_calib'''. Then you can adjust the point marker by selecting it with the (left button) mouse and moving it while keeping the mouse pressed (when adjustement is finished, nselected the option  '''[!CheckEnableMouse]''' to avoid spurious point creation with the mouse).
    6161
    62 If the grid image is of poor quality, it is alternatively possble to mark all the points by the mouse, using the '''Tools/Create''' grid instead of '''Tools/Detect grid''' in geometry_calib (not convenient in general).
     62If the grid image is of poor quality, it is alternatively possble to mark all the points by the mouse, using the '''!Tools/Create''' grid instead of '''!Tools/Detect grid''' in geometry_calib (not convenient in general).
    6363
    6464Once the grid has been marked, the calibration can be performed by the press button '''APPLY'''. We observe that the simple option 'rescale' is not appropriate in this case: a perspective effect is clearly visible, together with a non-linear deformation (grid lines are curved on the image). Therefore select the option '3D_quadr' which applies a 3D projection and quadratic correction. The grid image now appears of good quality in phys coordinates.