Does anyone know when Canon's optical ink detection system patent ends

[mikling]

Epson looks to be using the optical system with prism on some of their dye based printers. XP600.
This was Canon's patent I thought. Maybe the patent has run its course.

 

[ThrillaMozilla]

They got a patent for that?! It has been in use for at least 40 or 50 years that I know of. It used to be used on car batteries, for example, and very likely before that.

I just saw a key chain with a compass and thermometer on it. You guessed it. Patented.