Canon Patent Application: Photon Counting sensor (Single Photon Avalanche Photodiode sensor)

We've discovered a few patents in the past where Canon goes on to attempt to patent various technologies around single photon avalanche photodiodes (SPAD).  These are pretty specialized sensors that actually count when a photon hits the photo diode.  

We talk about global shutters, and even organic sensors as being the "the next thing" but really, if Canon (or anyone) could get a SPAD sensor working as a photography imager - it would be the "last thing". Of course, all is not without its unique problems SPAD's do saturate - and the faster the photons hit the sensor, the less accurate the diode is because it will "miss" counting photons that hit the diode as it's still counting the one that hit prior. The photons can completely oversaturate the diode when they come in at an even faster rate and can be actually harmful to the diode.  So there are problems to be solved.  However, SPAD's would deliver the ultimate low light camera.

Currently, sensors do use SPAD's such as specialized scientific sensors, and the like.  Canon seems to be attempting to make SPAD sensors useful in photographic imagers.  This patent application deals with reducing the dark current and overall power consumption of the sensor using SPAD's.

Japan Patent Application 2019-115032