Better would be fixed transparency's with trop that lay over the klaf. Would work on shabbos also.
-1. Some have an issue with that halachically. It is not reading off the klaf. It differs from glasses as glasses are batul to your eyes, while this is batul to the sefer Torah, which is a halachic problem.
My proposed invention does not put any hefsek between your eyes and the klaf. It only projects symbols on the blank parts.