Image sensor with charge transfer between pixels
Image sensor systems are disclosed that allow for charge transfer between pixels of a group included in a pixel array with a single digital readout of the accumulated charge from the group. Each of the pixels within a given group includes a photodetector. One or more pump gates are arranged between adjacent pixels of the given group to allow charge to be pumped from one pixel to the next in a serial fashion within the group. A readout circuit that includes at least a transfer gate and a capacitor may be coupled to a final pixel of the group to receive the accumulated charge and generate a photodetector signal (based on the accumulated charge) that can be amplified via a source follower component and ultimately read out to a column amplifier.
1. A charge coupled device (CCD), comprising:
a first pixel comprising a first photodetector;
a second pixel comprising a second photodetector;
a first pump gate and a second pump gate coupled in series between the first pixel and the second pixel;
a transfer gate having an input coupled to the second photodetector of the second pixel; and
a capacitor coupled to an output of the transfer gate.
2. The CCD of claim 1 , further comprising a reset switch coupled to the output of the transfer gate.
3. The CCD of claim 1 , wherein the output of the transfer gate is coupled to a gate of a FET.
4. The CCD of claim 1 , wherein each of the first pump gate and the second pump gate includes a FET and a potential barrier.
5. The CCD of claim 4 , wherein the potential barrier is a PN diode or a PIN diode.
6. The CCD of claim 1 , further comprising a third pixel comprising a third photodetector and a third pump gate and a fourth pump gate coupled in series between the third pixel and the first pixel.
7. The CCD of claim 6 , further comprising a first reset switch coupled to the first photodetector, a second reset switch coupled to the second photodetector, and a third reset switch coupled to the third photodetector.
8. An image sensor, comprising:
a pixel array having at least one column of addressable pixels, wherein the at least one column of addressable pixels includes at least a first pixel having a first photodetector and a second pixel having a second photodetector;
a first pump gate and a second pump gate coupled in series between the first pixel and the second pixel; and
a readout circuit including a transfer gate having an input coupled to the second photodetector of the second pixel, and a capacitor coupled to an output of the transfer gate.
9. The image sensor of claim 8 , further comprising:
a column amplifier coupled to the readout circuit;
an analog-to-digital converter (ADC) coupled to the column amplifier; and
a processor coupled to the ADC.
10. The image sensor of claim 8 , wherein the readout circuit further comprises a reset switch coupled to the output of the transfer gate.
11. The image sensor of claim 8 , wherein the output of the transfer gate is coupled to a gate of a FET.
12. The image sensor of claim 8 , wherein each of the first pump gate and the second pump gate includes a FET and a potential barrier.
13. The image sensor of claim 12 , wherein the potential barrier is a PN diode or a PIN diode.
14. The image sensor of claim 8 , wherein the pixel array further comprises a third pixel comprising a third photodetector, and the image sensor further comprises a third pump gate and a fourth pump gate coupled in series between the third pixel and the first pixel.
15. The image sensor of claim 14 , further comprising a first reset switch coupled to the first photodetector, a second reset switch coupled to the second photodetector, and a third reset switch coupled to the third photodetector.
16. A charge coupled device (CCD), comprising:
a plurality of pixels each having a photodetector;
a plurality of pump gate blocks, each pump gate block being between a pair of pixels of the plurality of pixels, each pump gate block comprising a first pump gate coupled in series with a second pump gate;
a transfer gate having an input coupled to the photodetector of one pixel of the plurality of pixels; and
a capacitor coupled to an output of the transfer gate.
17. The CCD of claim 16 , wherein the output of the transfer gate is coupled to a gate of a FET.
18. The CCD of claim 16 , wherein each of the first pump gate and the second pump gate includes a FET and a potential barrier.
19. The CCD of claim 18 , wherein the potential barrier is a PN diode or a PIN diode.
20. The CCD of claim 16 , further comprising a plurality of reset switches with each reset switch coupled to a corresponding photodetector of the plurality of pixels.