# Changes between Version 43 and Version 44 of Tutorial/GeometricCalibration

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Timestamp:
Jan 26, 2015, 2:24:25 PM (6 years ago)
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• ## Tutorial/GeometricCalibration

 v43 This 3D calibration relies on the [https://servforge.legi.grenoble-inp.fr/projects/soft-uvmat/search?q=attachment%3A3D_view.pdf pinhole camera model] (see [https://servforge.legi.grenoble-inp.fr/projects/soft-uvmat/search?q=wiki%3AUvmatHelp%23GeometryCalib UvmatHelp#GeometryCalib] section 8.1). It involves ''intrinsic parameters'' which characterize the optical system (camera and objective lens) and ''extrinsic parameters'' which describe the translation and rotation of the camera with respect to the physical coordinates. detailler sur le GUI. The intrinsic parameters are shown in the frame '''[Intrinsic Parameters] '''in the GUI '''geometry_calib'''. These are the focal lenghts (in pixel size on the sensor) '''[fx]''' and '''[fy]''',  the quadratic radial distortion coefficient '''[kc]''' and the coordinates '''[Cx]''' and '''[Cy]''' of the optical centre for this distortion (expressed in pixels on the image). The extrinsic parameters are shown in the frame  '''[Extrinsic Parameters]. '''It indicates in particular the translation T_z which represents the distance from the camera to the origin of the phys coordinates. Note that the calibration grid has been assumed by default to be at z=0, but this can be changed by selecting '''[!Tools/Translate points]''' in '''geometry_calib''' and entering a translation in ''z'' for the grid point coordinates. A last''' '''item needed to define calibration in a 3D context is the determination of the plane of the object in the phys coordinates. It is assumed by default to be the plane z=0, but this can be changed by the menu bar option '''[!Tools/Set slice] '''of uvmat. It is then possible to change the assumed z position, keeping the same calibration. Observe the corresponding change in the grid scale, since the same grid is then assumed to be at a different distance. A last''' '''item needed to define calibration in a 3D context is the determination of the plane of the object in the phys coordinates. It is assumed by default to be the plane z=0, but this can be changed by the menu bar option '''[!Tools/Set slice] '''of uvmat. It is then possible to change the assumed z position, keeping the same calibration. Observe the corresponding change in the grid scale, since the same grid is then assumed to be at a different distance. == 3D calibration improved by multiple planes: == For the next calibration, to avoid any change on the intrinsic parameters, select the option '''3D_extrinsic'''. It applies a 3D projection and quadratic correction according to the intrinsic parameters. '''Note:''' if the serie is missing some images (ie the increment from one image to another is not steady), '''uvmat''' will not allow you to use the arrow '''[->]'''  to move from an image to another if the increment is set. To avoid this  delete the number in [increment], you will then be able to go from an  image to another. '''Note:''' if the serie is missing some images (ie the increment from one image to another is not steady), '''uvmat''' will not allow you to use the arrow '''[->]'''  to move from an image to another if the increment is set. To avoid this  delete the number in '''[increment]''', you will then be able to go from an  image to another. == '''Merging the images of several cameras:''' == z position}} == '''Setting laser slices: ''' ==