ExifTool: Can I De-Duplicate A Lot of DNG/JPG Files?

[SprocketCM]

Lightroom singularly failed to recognise duplicates on successive import sessions and I now have several large catalogues with a lot of DNG files that are the same image but carry different names.  As many were taken in burst mode at 12 frames a second even the task of comparing them visually is mammoth and what I'd like to do is to isolate identical images and re-name them or perhaps restore them to the original name given by the cameras (mostly Canon CR2 files shot on EOS 1 and 5D cameras).  We are talking about around 6Tb of data and 500,000 files.

I hoped in vain, it seems, that Lightroom had sufficient brains to keep a record of the name as it was imported but this doesn't appear to be the case.  I've only had a quick look at the data that ExifTool can access but it looks as if there are several fields that could help.  Beyond that I have no idea how to start so any suggestions would be very welcome. 

[HaNu]

Dupehunter can do this job.
regards HaNu