Canon Patent Applications: Stacked Sensor Developments

There were quite a few stacked sensor patents in this week's haul, so I decided it best to categorize them all here. 

Patent Application 2021-166345

This is a Dual Pixel AF stacked sensor and Canon is looking to patent a method of reducing the amount of AD circuits per dual pixel pair.  If I'm reading this correctly, this method has a high number of ADC's per sensor.  Loosely described in the patent (810a/b and 1110a/b) is "read out circuit" which I'm going to assume is the analog to digital readout. Since that is what they are looking to improve in this patent application.

What makes me intrigued is that this patent application describes a "near" global shutter sensor, without the charge-hold circuity.  The idea is that the more readout ADC's you have the more simultaneously you can read the sensor.  it looks like in this case Canon is reading 3 pixels with 2 ADC's.

Patent Application 2021-166369

This next patent is a global shutter sensor.  Each pixel is split into two with a high sensitivity pixel and a low sensitivity pixel.  While no mention of a higher dynamic range is mentioned, I would think that would be a happy by-product of such a sensor.  As it is, Canon is looking to improve the image capture by reducing variations caused by the charge transfer (when a global shutter moves the charge from the photodiode to storage).

Patent Application 2021-166395

This patent application describes a stacked sensor, with pads at each pixel to handle transfer of the analog information from the photodiode layer to the processing layer.  Canon shows embodiments of 2 layers and up to 3 layers but little detail as to why they would choose a third layer (additional AF processing and/or memory would be the normal reasons).

The general idea of this patent application is to provide a high-performance sensor with as low a cost as possible. For a stacked sensor and its related applications (cameras and video cameras) this is something we can certainly get behind.

Patent Application 2021-166242

This patent application discusses a sensor using quantum dots and an organic film for light capture.  Let's just roll things forward 2 decades with this patent application ;)  Quantum dots are looking to replace CMOS "photodiodes" as the light capture.    There's a great general write-up on the technology here at IEEE.   Canon is looking at suppressing afterimages from the conversion, and also increasing the sensor's heat resistance.