Image sensor pixel with gain control
View Patent ↗A method for reading out an image signal, the method comprising: providing at least two photosensitive regions; providing at least two transfer gates respectively associated with each photosensitive region; providing a common charge-to-voltage conversion region electrically connected to the transfer gates; providing a reset mechanism that resets the common charge-to-voltage conversion region; after transferring charge from at least one of the photo-sensitive regions, disabling all transfer gates at a first time; enabling at least one transfer gate at a subsequent second time; and transferring charge from at least one of the photosensitive regions at a subsequent third time while the at least one transfer gate from the second time remains enabled.
1. A method for reading out a photo-sensitive region, the method comprising:
providing at least one photo-sensitive region;
providing at least one transfer gate associated with the photo-sensitive region;
providing a charge-to-voltage conversion region electrically connected to the transfer gate;
providing a reset mechanism that resets the charge-to-voltage conversion region;
resetting the charge-to-voltage conversion region with the transfer gate off;
after resetting the charge-to-voltage conversion region, measuring a first sample of the charge-to-voltage conversion region;
after measuring the first sample, turning on the transfer gate to transfer charge from the photo-sensitive region to the charge-to-voltage conversion region;
after transferring the charge from the photo-sensitive region, measuring two samples V TGon1 and V TGoff1 charge-to voltage conversion region, wherein V TGon1 is measured with the transfer gate on and V TGoff1 is measured with the transfer gate off;
after measuring the two samples V TGon1 and V TGoff1 , resetting the charge-to-voltage conversion region a second time;
after resetting the charge-to-voltage conversion region the second time, measuring two samples V TGon2 and V TGoff2 of the charge-to-voltage conversion region, wherein V TGon2 is measured with the transfer gate on and V TGoff2 is measured with the transfer gate off;
determining a high conversion gain measurement using an equation (V TGoff1 −the first sample); and
determining a low conversion gain measurement using an equation (V TGon1 −the first sample)−(V TGon2 −V TGoff2 ).
2. The method as in claim 1 further comprising storing a difference of the V TGon2 and V TGoff2 samples.
3. A method for reading out a photo-sensitive region, the method comprising:
providing at least one photo-sensitive region;
providing at least one transfer gate associated with the photo-sensitive region;
providing a charge-to-voltage conversion region electrically connected to the transfer gate;
providing a reset mechanism that resets the charge-to-voltage conversion region;
resetting the charge-to-voltage conversion region with the transfer gate turned off;
after resetting the charge-to-voltage conversion region, measuring a first sample of the charge-to-voltage conversion region;
after measuring the first sample, turning on the transfer gate to transfer charge from the photo-sensitive region to the charge-to-voltage conversion region;
after transferring the charge from the photo-sensitive region, measuring a second sample of the charge-to voltage conversion region with the transfer gate on;
after measuring the second sample, measuring a third sample of the charge-to voltage conversion region with the transfer gate off;
after measuring the third sample, resetting the charge-to-voltage conversion region with the transfer gate off a second time;
after resetting the charge-to-voltage conversion region the second time, measuring a fourth sample of the charge-to-voltage conversion region with the transfer gate off;
after measuring the fourth sample, measuring a fifth sample of the charge-to-voltage conversion region with the transfer gate on;
determining a high conversion gain measurement using an equation (the third sample−the first sample); and
determining a low conversion gain measurement using an equation (the second sample−the first sample)−(the fifth sample−the fourth sample).