Changes between Version 172 and Version 173 of UvmatHelp


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Timestamp:
Jan 23, 2015, 10:08:26 AM (6 years ago)
Author:
vaillant1p
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  • UvmatHelp

    v172 v173  
    583583
    584584=== 8.2 The GUI geometry_calib.fig ===
    585 [[Image(geometry_calib.jpg)]] -''' Opening the GUI: ''' it is made visible  from the GUI '''uvmat.fig''' by  the menu bar command '''[!Tools/Geometric calibration] '''.  If calibration data already exist in the current file <!ImaDoc>, the corresponding parameters and the list of reference points are displayed in the table '''[!ListCoord]'''. The three first columns indicate the physical coordinates and the two last ones the corresponding image coordinates (in pixels). The physical unit is imposed as centimeter by the menu '''[!CoordUnit]''' to avoid mistakes. Calibration points can be alternatively introduced by opening any XML file <!ImaDoc> with the menu bar command '''[Import]''' of '''geometry_calib.fig'''. It is possible to import the whole information, option 'All', the calibration point coordinates only, or the calibration parameters only.
     585[[Image(geometry_calib.jpg)]]
     586
     587-''' Opening the GUI: ''' it is made visible  from the GUI '''uvmat.fig''' by  the menu bar command '''[!Tools/Geometric calibration] '''.  If calibration data already exist in the current file <!ImaDoc>, the corresponding parameters and the list of reference points are displayed in the table '''[!ListCoord]'''. The three first columns indicate the physical coordinates and the two last ones the corresponding image coordinates (in pixels). The physical unit is imposed as centimeter by the menu '''[!CoordUnit]''' to avoid mistakes. Calibration points can be alternatively introduced by opening any XML file <!ImaDoc> with the menu bar command '''[Import]''' of '''geometry_calib.fig'''. It is possible to import the whole information, option 'All', the calibration point coordinates only, or the calibration parameters only.
    586588
    587589-''' Plotting calibration points: ''' press the button '''[PLOT PTS] ''' to visualise the current list of calibration points. The physical or image coordinates will be used in the list '''[!ListCoord]''', depending on the option blank or 'phys' in the menu '''[transform_fct]''' of ''' uvmat.fig''' .
    588590
    589 -'''Simple scaling''': a simple scaling, in pixels/cm, can be introduced by the menubar command '''[Tools/Set scale]''', which displays a set of four reference points in the table '''[!!ListCoord]'''. The tool 'ruler', from the menu bar command '''[Tools/ruler]''' of '''uvmat.fig''', can be useful to get the scaling. The origin of the physical coordinates  is set by default to the lower left image corner. Use the tool 'translate points', described below, to change the origin.
     591-'''Simple scaling''': a simple scaling, in pixels/cm, can be introduced by the menu bar command '''[!Tools/Set scale]''', which displays a set of four reference points in the table '''[!ListCoord]'''. The tool 'ruler', from the menu bar command '''[Tools/ruler]''' of '''uvmat.fig''', can be useful to get the scaling. The origin of the physical coordinates  is set by default to the lower left image corner. Use the tool 'translate points', described below, to change the origin.
    590592
    591593-''' Appending  calibration points with the mouse: ''' Calibration points can be manually picked out by the mouse on the current image displayed by '''UVMAT''' (left button click). This requires the activation of the check box '''[enable mouse]'''. The image coordinates (in pixels) are picked by the mouse (the option 'blank' in the popup menu '''[transform_fct]''' is automatically selected when the mouse button is pressed). Zoom can be used to improve the precision, but must be desactivated for mouse selection (then move across the image by the key board directional arrows). Points can be accumulated from several images, using the key board short cuts 'p' and 'm' to move in the image series without the mouse.  A calibration point can be adjusted by selecting it with the mouse and moving it while pressing the left mouse button. The coordinates in pixel of the selected points get listed in the table '''[!ListCoord]''' of '''geometry_calib.fig'''.
     
    603605To reproduce the same calibrationn for image series, open one of the image in the series, and apply again the calibration with the same points, keeping the GUI geometry_calib opened.
    604606
    605 To calibrate at once a set of experiments, a better alternative is the command '''[REPLICATE]'''. Open a folder  '''Campaign''', parent of the folders '''Experiment''' to treat. The GUI '''data_browser.fig''', also described in [#a3.7Dataorganisationinaproject section 3.7], then pops up. A two-column display appears, with the list of '''Experiments''' on the left and the list of corresponding '''[wiki:DataSeries !DataSeries]''' on the right. Select the list of experiments to calibrate, and a single camera name in '''[wiki:DataSeries !DataSeries]''', then validate by pressing '''OK'''.
    606 
    607 -'''3D calibration''': 3D projection is handled by the options in '''[calib_type]''' '3D_lin' or '3D_quad' (if non-linear distortion is significant). By default, the set of calibration points is assumed to be contained in a single plane ''z''=0. For a correct determination of the 3D features, the normal to this plane must be tilted with respect to the line of view. Otherwise this problem of indetermination can be resolved by using a set of (typically 5-10) calibrations images using a plane grid with different tilting angles (for precision the grid must cover a large area of the view field). On each image, get calibration points with the tool '''[!Tools/Detect grid]''', introducing the appropriate grid mesh. Do not fill info on ''z'' coordinates. Store the points each time (without applying calibration at this stage), which fills the list [! ListCoordFiles] of file names. Then introduce a last grid image which will be considered as defining the orientation of the ''z'' axis, perpendicular to the grid. Detect points on this last image, but instead of storing them, apply the calibration with the option 3D_linear or 3D_quadr. A non-zero ''z'' position of this grid can be introduced by a z translation performed with '''!Tools/Translate points'''.
     607To calibrate at once a set of experiments, a better alternative is the command '''[REPLICATE]'''. Open a folder  '''Campaign''', parent of the folders '''Experiment''' to treat. The GUI '''data_browser.fig''', also described in [#a3.7Dataorganisationinaproject section 3.7], then pops up. A two-column display appears, with the list of '''Experiments''' on the left and the list of corresponding '''[!DataSeries]''' on the right. Select the list of experiments to calibrate, and a single camera name in '''[!DataSeries]''', then validate by pressing '''OK'''.
     608
     609-'''3D calibration''': 3D projection is handled by the options in '''[calib_type]''' '3D_lin' or '3D_quad' (if non-linear distortion is significant). By default, the set of calibration points is assumed to be contained in a single plane ''z''=0. For a correct determination of the 3D features, the normal to this plane must be tilted with respect to the line of view. Otherwise this problem of indetermination can be resolved by using a set of (typically 5-10) calibrations images using a plane grid with different tilting angles (for precision the grid must cover a large area of the view field). On each image, get calibration points with the tool '''[!Tools/Detect grid]''', introducing the appropriate grid mesh. Do not fill info on ''z'' coordinates. Store the points each time (without applying calibration at this stage), which fills the list [!ListCoordFiles] of file names. Then introduce a last grid image which will be considered as defining the orientation of the ''z'' axis, perpendicular to the grid. Detect points on this last image, but instead of storing them, apply the calibration with the option 3D_linear or 3D_quadr. A non-zero ''z'' position of this grid can be introduced by a z translation performed with '''!Tools/Translate points'''.
    608610
    609611-'''Intrinsic parameters''': the previous procedure first determines the extrinsic parameters which characterize the camera optics (focal lengths and nonlinear deformation parameter). Then the extrinsic parameters, translation and rotation of the camera with respect to the reference grid, are determined on the last grid image. If the same optics is used in a new experiment, it is possible to skip the multiplane detection, importing the intrinsic parameters from a previous <!ImaDoc> file by the menu bar tool '''[!Import/Intrinsic]''' parameters, then applying the calibration with the option '3D_extrinsic' with the reference grid image only.
    610612
    611 -'''Section planes:''' deducing the physical coordinates from image coordinates requires information on the section plane. The default assumption is that the objects in the image are in the plane used for calibration, but uvmat can handle volume scanning by a laser plane. A set of section planes can be defined by their origin positions and rotation angle vectors. Theses planes are labelled by a ''z index'', assumed to be the frame index j (case of volume scan), or the index i modulo the number of slices !NbSlice (case of 'multilevel' scan). These settings are stored in the xml file <!ImaDoc> as part of the section <!GeometryCalib> and can be edited from '''uvmat.fig''' with the menu bar command '''[Tools/set slice]'''. A dialog box '''set_slices''' appears for entering the first and last section plane positions ''z'', as well as the number of slices and the option 'volume_scan' ('multilevel' otherwise). In the absence of 3D scan put twice the same value for first and last z.  Finally a tilt angle of the laser sheet, around the ''x'' and ''y'' axis, can be introduced, with a possible angular scanning from first to last section planes. After introduction of the plane position information, the z-index is displayed in the frame '''[[wiki:FileIndices !FileIndices]]''' of '''uvmat.fig'''. The local ''z'' position of the mouse pointer, assumed to lay on the current section plane, is then displayed in '''[text_display]'''.
     613-'''Section planes:''' deducing the physical coordinates from image coordinates requires information on the section plane. The default assumption is that the objects in the image are in the plane used for calibration, but uvmat can handle volume scanning by a laser plane. A set of section planes can be defined by their origin positions and rotation angle vectors. Theses planes are labelled by a ''z index'', assumed to be the frame index j (case of volume scan), or the index i modulo the number of slices !NbSlice (case of 'multilevel' scan). These settings are stored in the xml file <!ImaDoc> as part of the section <!GeometryCalib> and can be edited from '''uvmat.fig''' with the menu bar command '''[Tools/set slice]'''. A dialog box '''set_slices''' appears for entering the first and last section plane positions ''z'', as well as the number of slices and the option 'volume_scan' ('multilevel' otherwise). In the absence of 3D scan put twice the same value for first and last z.  Finally a tilt angle of the laser sheet, around the ''x'' and ''y'' axis, can be introduced, with a possible angular scanning from first to last section planes. After introduction of the plane position information, the z-index is displayed in the frame '''[!FileIndices]''' of '''uvmat.fig'''. The local ''z'' position of the mouse pointer, assumed to lay on the current section plane, is then displayed in '''[text_display]'''.
    612614
    613615-'''Refraction effect:''' refraction effect can be accounted for if calibration was done in air by selecting the check box refraction, and introducing the water height (assumed at ''z''=cte) and refraction index. The apparent distance reduction for objects below the water height will be then taken into account.
     
    856858Install two cameras viewing a common field with angle about 45 ° on each side. A system of titled objective lenses (Sheimpflug) allows to optimize the focus in the whole image.
    857859
    858 Make a careful geometric calibration, by taking the images of a grid positioned in the plane of the laser sheet used for particle illumination, as described in section #GeometryCalib.
     860Make a careful geometric calibration, by taking the images of a grid positioned in the plane of the laser sheet used for particle illumination, as described in section [#GeometryCalib section 6].
    859861This calibration model is valid in air or with an interface air-water perpendicular to the line of sight for each camera. Otherwise, the calibration problem is more complex.
    860862