Braille preservation service

The American Printing House for the Blind has an electronic braille preservation service which will scan braille books, metal plates, etc., and convert it to electronic format
https://www.aph.org/custom/braille-preservation/

Also, here is a Windows optical braille scanning program that works with a flatbed scanner, although I have no experience with it so cannot say how well it works
http://www.karishmaenterprises.com/OBR.htm