Aptina: DR-Pix

Aptina DR-Pix: 2 mode in pixel

Low conversion gain(LCG): in bright light

High conversion gain(HCG): in low light

Aptina releases this high dynamic range technique for camera application.

Original inter-scene DR is limited to 69dB, but can be equal to 82.9dB at HCG mode.

Basic CMOS image sensor operation
Active pixel is the major structure in CMOS image sensor.(Active Pixel)
4T structure is the most used in pixel design.
Photodiode converts the photon into electron after Reset gate clear all integrated charge. Electron is transfer to the floating diffusion node, then turn on the gate. Source follower severed as amplifier change the current into voltage. Finally, Select Gate will be triggered to output signal.
Dilemma
At Floating Diffusion Node, there is a capacitor. This capacitor can increase the charge handling ability of pixel. The charge converted from photon by photodiode need to be accumulated in container to enough voltage, then trigger the source follower gate.
The bigger the capacitor, the better charge handling ability.
But capacitor would decrease the sensitivity and increase the read noise: it need more accumulated charge to get the voltage to turn on the gate of source follower.

Aptina DR-Pix

Aptina comes up with a method to solve the issue of capacitor--DCG(Dual Conversion Gain) gate is to control the link with capacitor at the floating diffusion node, depending on different light mode.

Bright light scene:

More photon is converted into electron, need a big container to storage electron.

DCG is turned on to connect the capacitor, which decrease the sensitivity.

Low light scene

Less photon, less electron

DCG is off to disconnect the capacitor, increase the sensitivity.

~ form (Aptina Whitepaper)

Brilliant idea! DR-Pix solve the dynamic range problem from electric, more basic view from source, not like frame multi exposure by software.

Issue

But it seems that DCG is controlled manually on all pixels.

I think that if each pixel can control independently on input light, the output voltage needs a conversion differently on LCG/HCG mode.