A cathodoluminescence microscope and method are used to identify and classify dislocations within a semiconductor sample. At least two CL polarized images are concurrently obtained from the sample. The images are added together to obtain a total intensity image. A normalized difference of the images is taken to obtain a degree of polarization (DOP) image. The total intensity and DOP images are compared to differentiate between edge dislocations and screw dislocations within the sample. Edge dislocation density and screw dislocation density may then be calculated.