Methods and apparatus for a multiple storage pixel imaging system

1. A pixel array responsive to a processing circuit for transmitting control signals, comprising:

a plurality of pixels, wherein each pixel comprises:

a photosensitive element responsive to light;

a first transfer gate coupled to the photosensitive element, wherein the first transfer gate selectively couples the photosensitive element to a floating diffusion region during an integration period, and transfers a first charge, after a first exposure period, from the photosensitive element to the floating diffusion region in response to a first control signal; wherein the floating diffusion region stores the first charge during the integration period; and

a second transfer gate coupled to the photosensitive element, wherein the second transfer gate selectively couples the photosensitive element to a storage region during the integration period, and transfers a second charge, after a second exposure period, from the photosensitive element to the storage region in response to a second control signal; wherein the storage region stores the second charge during the integration period.

2. The pixel array of claim 1 , wherein the floating diffusion region comprises a diode.

3. The pixel array of claim 1 , wherein the floating diffusion region comprises a capacitor.

4. The pixel array of claim 1 , wherein the storage region comprises a diode.

5. The pixel array of claim 1 , further comprising a third transfer gate coupling the storage region to the floating diffusion region for transferring the second charge from the storage region to the floating diffusion region.

6. The pixel array of claim 5 , further comprising a reset gate coupling the floating diffusion region to a voltage source.

7. The pixel array of claim 1 , wherein the floating diffusion region and the storage region each store multiple charges with corresponding exposure periods resulting in the storage region storing charge with a second total exposure period and the floating diffusion region storing charge with a first total exposure period; wherein the second total exposure period is greater than the first total exposure period.

8. The pixel array of claim 1 , wherein, during a readout period, the first charge is read out from the floating diffusion region, the floating diffusion region is reset via a reset signal, and the second charge is read out from the storage region after reset of the floating diffusion region.

9. A method for storing charge in an imaging device, comprising:

during an integration period:

generating a first charge portion with a photosensitive element during a first exposure period;

transferring the first charge portion from the photosensitive element to a floating diffusion region via a first transfer gate;

generating a second charge portion with the photosensitive element during a second exposure period; and

transferring the second charge portion from the photosensitive element to a storage node via a second transfer gate.

10. The method of claim 9 , wherein the second exposure period is greater than the first exposure period.

11. The method of claim 9 , wherein the first and second exposure periods are synchronized to a pulsing light source.

12. The method of claim 9 , further comprising cyclically generating and transferring the first and second charge portions, wherein the first charge portions accumulate and are summed to form a first accumulated charge, and the second charge portions accumulate and are summed to form a second accumulated charge.

13. The method of claim 12 , further comprising computing a ratio of the second accumulated charge to the first accumulated charge.

14. The method of claim 13 , wherein the first and second exposure periods are extended based on the computed ratio.

15. The method of claim 12 , further comprising reading out the first accumulated charge from the floating diffusion region via a row select gate.

16. The method of claim 15 , further comprising resetting the floating diffusion region by applying a reset signal via a reset gate.

17. The method of claim 16 , further comprising reading out the second accumulated charge from the storage node via a third transfer gate, wherein the charge moves through the floating diffusion region.

18. An imaging system, comprising:

a control unit, wherein the control unit transmits a control signal; and

a pixel array, communicatively coupled to the control unit, comprising a plurality of pixels arranged in rows and columns, wherein each pixel comprises:

a photosensitive element responsive to light;

a first transfer gate, coupled to the photosensitive element and responsive to a first control signal, wherein the first transfer gate transfers a first charge from the photosensitive element to a floating diffusion region after a first exposure period during an integration period;

a second transfer gate, coupled to the photosensitive element and responsive to a second control signal, wherein the second transfer gate transfers a second charge from the photosensitive element to a storage region after a second exposure period during the integration period;

a reset gate, responsive to a third control signal, wherein the reset gate resets the floating diffusion region prior to transfer of the second charge; and

a third transfer gate, coupled between the storage region and the floating diffusion region and responsive to a fourth control signal, wherein the third transfer gate transfers the second charge from the storage region to the floating diffusion region.

19. The system of claim 18 , wherein the control unit coordinates the plurality of pixels to integrate simultaneously.

20. The system of claim 18 , wherein:

the floating diffusion region and the storage region each store multiple charges with corresponding exposure periods resulting in the storage region storing charge with a second total exposure period and the floating diffusion region storing charge with a first total exposure period; and

the second total exposure period is greater than the first total exposure period.