Patents, so detailed and yet so vague
From "US Patent 6943820 - Systems and methods to reversibly convert a film-based camera into a digital camera"
Here www.patentstorm.us/patents/6943820/claims.html
This one was doing the rounds in the 1990s. It's vapourware, it was always going to come out "next year" and it never did. My guess is the drop in price of digital cameras killed it.