Eliminate duplicate photos

I have more than 30,000 photos in Lightroom, including lots of duplicates. I would like to weed them out.

I assumed that Lightroom would have a function for this but I can't find it. I heard that Photoshop Elements has that capability but I haven't tried it. In any case, I would hate to have to leave Lightroom to do this simple task.

I assume that there might be a 3rd party plug-in that eliminates duplicates, but I'm worried about using software if I don't know the developer.

Any advice?