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Introduction to mrFindBorders
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4.9.2.3 Matching
Different parameters can be defined for the different stages of the multi-resolution matching
process. For each resolution, it is possible to specify the optimization (energy minimization)
method from a list box. If the user wants to match only phase-wedge images, then the method
called “Grad. (Angular Dir.)” is recommended. If the user also wants to match the phase-ring
images, the method called “Grad. (2 Directions)” should be used. The reasons for this are ex-
plained later. The method “LM-Gradient “ (a variant of the Levenberg-Marquardt minimiza-
tion technique) was tested but is currently not working reliably.
Number of Iterations
The number of iterations can be specified. Usually, 2 to 3 iterations for each resolution are
sufficient. The user can specify more iterations. Then, the graph of the energy components and
the total energy can be viewed. Based on the graphs, it is possible to determine how many it-
erations are needed until the energy has decreased to a level where it does not change much
any more. Since the very-low and low-resolution steps are done pretty quickly, the number of
iterations can be increased without increasing the overall time needed for matching dramati-
cally.
Energy Weights
The parameters denoted by “Weight for Wedge”, “Weight for Deform.”, “Weight for Points”,
and “Weight for Ring” specify the weights for the four different energy components. Detailed
explanations on how these energy components are defined and computed can be found in the
following chapters. Here, only basic explanations as well as rules on how to set the weights
are presented. If a weight is set to zero, the corresponding energy component will not be used
during the matching process.
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The first parameter specifies the weight for the energy that is calculated based on the
difference between the measured phase-wedge image and the corresponding atlas im-
age.
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