The Polar Image option allows the user to create a false color image in polar, rather than Cartesian coordinates.
In such an image the horizontal axis represents chi (the azimuthal angle) and the vertical axis shows either q or 2-theta.
Like the original false color image, a box at the bottom shows the position of the cursor in polar units.
In Batch mode see MAKEPOLARIMAGE.
Use: To create a polar image, after reading in the data the user selects the desired radial variable, optionally sets the values of Radial-Min, Radial-Max, and Left-hand Chi, then clicks the Create Image button. Afterwards, the user can adjust the brightness scale with Display-Min and Display-Max. Radial Variable: The radial variable can be either the momentum transfer q or the scattering angle 2-theta, selected by a drop-down menu. Radial-Min and Radial-Max: The user has the option of selecting the lowest and highest values of the radial variable; the defaults are smallest and largest values in the underlying data set (the lowest value is usually zero). Left-Hand Chi: By default, the value of chi at the left-hand edge of the image is zero. The user can set this to anything between 0 and 360, effectively setting the position of the branch cut. Display-Min and Display-Max: After the image has been made, the user can adjust the color scale by changing the values associated with "black" (Display-Min) and "white" (Display-Max). In Batch mode see POLARMAXVALUE and POLARMINVALUE. Polar Image and Calibration: The polar image will be properly calculated only if the data have been properly calibrated, and in fact the image can be used as a way to cross-check the calibration. In particular, the appearance of the polar image depends sensitively on the choice of image center. If the X-center and Y-center are approximately correct, then Bragg rings, which are circular in the original image, should be straight lines in a polar image, but one or both of the center positions are off by even a few pixels then the Bragg rings will form wavy lines. |