I would say it's also about blade geometry and heat treat with regard to a knife, so not sure just determining edge thickness will "cut it".
My understanding and I'm by no means an expert is that they typically use a gaussian beam to get a true edge thickness determination. There may be other means, but that's what I've read to be the true test.
Since you didn't mention the purpose behind your question I may be completely off base, but I think what you may want is a Catra test. I believe if you go to their website they will rent the testing machine or perform tests for you. I have no idea what it costs, or whether what you're trying to do really gets to that level, but catra is the yard stick most use to truly measure how sharp a blade is. For whatever that's worth.
