A mask can be applied to the phase image to facilitate phase unwrapping and wave inversion algorithms. 

mag threshold: The threshold value with which to create a mask from the input magnitude data.

smooth: Checking this box smoothes the mask with a 9x9 median filter.

limit regions: Check this box to restrict the number of connected regions in the mask.

limit voids: Check this box to restrict the number of connected "voids" in the mask.