Inkjet ink level sensing?
Yep, any (prism) level measurement in the visible spectrum would need clear
cartriges! Nearly all modern OEM carts. are black or an opaque colour! C+
Or a vertical light path from the led chip on the bottom of the cartridge, up
through the (now) empty cartridge, reflecting off of a prism inside the top
of the cartridge back to a receiver on the same chip as the LED is mounted.
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