Where Everybody Knows Your Name

I don't know how to tell my professor that my name isn't Richard. It's a plausible mistake because that's my middle name and I use the whole thing in papers and academic writing, but I just noticed that most of her emails to me are addressed to Richard. I might want to correct this before exams or other things where people check my identity or grade my papers, especially in a class where there's actually a living, breathing Richard who sits across from me. Unfortunately, there's absolutely no polite way to do this after being in the class for four months, so I'm just going to not say anything and maybe speak in the third person as much as possible.