Method, apparatus and system providing a storage gate pixel with high dynamic range
A method, apparatus and system are described providing a high dynamic range pixel. An integration period has multiple sub-integration periods during which charges are accumulated in a photosensor and repeatedly transferred to a storage node, where the charges are accumulated for later transfer to another storage node for output.
1. A pixel circuit comprising:
a photosensor having a first charge storage capacity, the photosensor configured to accumulate charge;
a storage node having a second charge storage capacity that is greater than the first charge storage capacity;
a first transistor between the photosensor and the storage node, configured to transfer change from the photosensor to the storage node;
a floating diffusion region;
a second transistor between the photosensor and the floating diffusion region, configured to transfer charge from the photosensor to the floating diffusion region; and
a third transistor between the photosensor and an anti-blooming voltage node, configured to transfer charge from the photosensor to the anti-blooming voltage node,
wherein
the photosensor is configured to accumulate a sum amount of charge during an integration period,
the pixel circuit is configured to reset the photosensor during a portion of the integration period by pulsing an anti-blooming signal applied to a gate of the third transistor,
after resetting the photosensor, the pixel circuit is further configured to hold the anti-blooming signal at a constant voltage during a remainder of the integration period,
the integration period includes a plurality of sub-integration periods,
at least two sub-integration periods in the plurality of sub-integration periods have differing durations,
the sum amount of charge includes a plurality of portions, and
individual portions of the plurality of portions are transferred from the photosensor at different times during the integration period corresponding to ends of sub-integration periods in the plurality of sub-integration periods.
2. The pixel circuit of claim 1 , wherein the floating diffusion region is configured to receive the plurality of portions transferred from the photosensor and accumulated over the integration period.
3. The pixel circuit of claim 1 , wherein the storage node includes a capacitor.
4. The pixel circuit of claim 1 , wherein the photosensor is a first photosensor, and wherein the pixel circuit further comprises a second photosensor configured to accumulate charge and having a third storage capacity.
5. The pixel circuit of claim 4 further comprising a fourth transistor between the second photosensor and the floating diffusion region, configured to transfer charge from the second photosensor to the floating diffusion region.
6. The pixel circuit of claim 5 further comprising a fifth transistor between the second photosensor and the storage node, configured to transfer charge from the second photosensor to the storage node.
7. The pixel circuit of claim 6 further comprising
a fourth photosensor configured to accumulate charge and having a fourth storage capacity;
a fifth photosensor configured to accumulate charge and having a fifth storage capacity;
a sixth transistor between the third photosensor and the floating diffusion region, configured to transfer charge from the third photosensor to the floating diffusion region; and
a seventh transistor between the fourth photosensor and the floating diffusion region, configured to transfer charge from the fourth photosensor to the floating diffusion region.
8. The pixel circuit of claim 1 , wherein the second charge storage capacity is at least twice the first storage capacity.
9. The pixel circuit of claim 1 , wherein a voltage of the pulsed anti-blooming signal during the portion of the integration period is greater than the constant voltage.
10. An imager circuit comprising:
at least one pixel circuit, the at least one pixel circuit comprising
a photosensor having a first charge storage capacity, the photosensor configured to accumulate charge,
a storage node having a second charge storage capacity that is greater than the first charge storage capacity,
a first transistor between the photosensor and the storage node, configured to transfer charge from the photosensor to the storage node,
a floating diffusion region,
a second transistor between the photosensor and the floating diffusion region, configured to transfer charge from the photo sensor to the floating diffusion region, and
a third transistor between the photosensor and an anti-blooming voltage node, configured to transfer charge from the photosensor to the anti-blooming voltage node; and
a control circuit operably coupled to the at least one pixel circuit, the control circuit configured to
define a plurality of integration periods during an image capture in which charge produced by the photosensor in each of the integration periods is transferred from the photosensor and successively accumulated, wherein at least two integration periods in the plurality of integration periods have differing durations,
reset the photosensor during a portion of at least one integration period by pulsing an anti-blooming signal applied to a gate of the third transistor,
after resetting the photosensor, hold the anti-blooming signal at a constant voltage during a remainder of the at least one integration period, and
operate at least one of the first transistor and the second transistor to transfer charge produced by the photosensor during the integration periods to the floating diffusion region.
11. The imager circuit of claim 10 , wherein the floating diffusion region is configured to receive charge transferred from the photosensor and accumulated over multiple integration periods.
12. The imager circuit of claim 10 , wherein the photosensor is a first photosensor, and wherein the pixel circuit further comprises a second photosensor configured to accumulate charge and having a third storage capacity.
13. The imager circuit of claim 12 further comprising a fourth transistor between the second photosensor and the floating diffusion region, configured to transfer charge from the second photosensor to the floating diffusion region.
14. The imager circuit of claim 13 further comprising a fifth transistor between the second photosensor and the storage node, configured to transfer charge from the second photosensor to the storage node.
15. An imaging device comprising:
a pixel array comprising a plurality of pixels, wherein each of the pixels comprises
a photosensor having a first charge storage capacity, the photosensor configured to accumulate charge,
a storage node having a second charge capacity that is greater than the first charge capacity,
a first transistor between the photosensor and the storage node, configured to transfer charge from the photosensor to the storage node,
a floating diffusion region,
a second transistor between the photosensor and the floating diffusion region, configured to transfer charge from the photo sensor to the floating diffusion region, and
a third transistor between the photosensor and an anti-blooming voltage node, configured to transfer charge from the photosensor to the anti-blooming voltage node; and
a control circuit operably coupled to the plurality of pixels, the control circuit configured to
define a plurality of successive integration periods during an image capture in which charge produced by the photosensor in each of the integration periods is transferred from photosensor and successively accumulated, wherein at least two integration periods in the plurality of successive integration periods have differing durations,
reset the photosensor during a portion of at least one integration period by pulsing an anti-blooming signal applied to a gate of the third transistor,
after resetting the photosensor, hold the anti-blooming signal at a constant voltage during a remainder of the at least one integration period, and
transfer charge accumulated during the integration periods to the floating diffusion region.
16. The imaging device of claim 15 , wherein the floating diffusion region is configured to receive charge transferred from the photosensor and accumulated over multiple integration periods.
17. The imaging device of claim 15 , wherein the photosensor is a first photosensor, and wherein the pixel circuit further comprises a second photosensor configured to accumulate charge and having a third storage capacity.
18. The imaging device of claim 17 further comprising a fourth transistor between the second photosensor and the floating diffusion region, configured to transfer charge from the second photosensor to the floating diffusion region.
19. The imaging device of claim 18 further comprising a fifth transistor between the second photosensor and the storage node, configured to transfer charge from the second photosensor to the storage node.