Global shutter imaging pixels
A global shutter imaging pixel may have a single source follower transistor. The source follower transistor may be coupled to a floating diffusion region and a charge storage region. In order to read out samples from the charge storage region without including a second source follower transistor in each pixel, the samples may be transferred to floating diffusion regions of adjacent pixels. Alternatively, a transistor may be configured to transfer charge from the charge storage region to the floating diffusion region of the same pixel, thus reusing a single source follower transistor. These types of pixels may be used for correlated double sampling, where a reset charge level and integration charge level are both sampled. These pixels may also operate in a global shutter mode where images are captured simultaneously by each pixel.
1. A global shutter imaging pixel comprising:
a photodiode;
a floating diffusion region;
a transfer transistor configured to transfer charge from the photodiode to the floating diffusion region;
a source follower transistor coupled to the floating diffusion region;
a charge storage region coupled to the source follower transistor; and
a first transistor, wherein the first transistor is configured to transfer charge from the charge storage region to the floating diffusion region.
2. The global shutter imaging pixel defined in claim 1 , further comprising:
a second transistor, wherein the second transistor is coupled between the source follower transistor and the charge storage region.
3. The global shutter imaging pixel defined in claim 2 , further comprising:
a third transistor, wherein the third transistor is coupled between the source follower transistor and a column line.
4. The global shutter imaging pixel defined in claim 3 , further comprising:
a reset transistor, wherein the reset transistor is coupled between the floating diffusion region and a bias voltage supply line.
5. The global shutter imaging pixel defined in claim 4 , wherein the charge storage region comprises first and second storage capacitors and a fourth transistor, wherein the fourth transistor is coupled between the first and second storage capacitors.
6. The global shutter imaging pixel defined in claim 4 , wherein the charge storage region comprises first and second storage capacitors that are coupled to a first node, wherein the first node is coupled to the second transistor, wherein the second storage capacitor is coupled between the first node and a second node, wherein the second node is coupled to the first transistor and a calibration transistor, and wherein the calibration transistor couples the second node to an additional bias voltage supply line.
7. The global shutter imaging pixel defined in claim 4 , wherein the charge storage region comprises at least one component selected from the group consisting of: a storage capacitor, a storage diode, and a storage gate.
8. A global shutter imaging pixel comprising:
a photodiode;
a floating diffusion region;
a transfer transistor configured to transfer charge from the photodiode to the floating diffusion region;
a source follower transistor coupled to the floating diffusion region;
a charge storage region coupled to the source follower transistor, wherein the charge storage region comprises first and second storage capacitors;
a first transistor, wherein the first transistor is configured to transfer charge from the charge storage region to the floating diffusion region when asserted; and
a second transistor that is coupled between the first and second storage capacitors.
9. The global shutter imaging pixel defined in claim 8 , further comprising:
a third transistor, wherein the third transistor is coupled in series between the source follower transistor and the charge storage region.
10. The global shutter imaging pixel defined in claim 8 , further comprising:
a third transistor, wherein the third transistor is coupled between the source follower transistor and a column line.
11. The global shutter imaging pixel defined in claim 8 , further comprising:
a reset transistor, wherein the reset transistor is coupled between the floating diffusion region and a bias voltage supply line.
12. A global shutter imaging pixel comprising:
a photodiode;
a floating diffusion region;
a transfer transistor configured to transfer charge from the photodiode to the floating diffusion region;
a source follower transistor coupled to the floating diffusion region;
a charge storage region coupled to the source follower transistor; and
a first transistor, wherein the first transistor is directly coupled to the floating diffusion region and wherein the first transistor is configured to transfer charge from the charge storage region to the floating diffusion region.
13. The global shutter imaging pixel defined in claim 12 , further comprising:
a second transistor, wherein the second transistor is coupled in series between the source follower transistor and the charge storage region.
14. The global shutter imaging pixel defined in claim 13 , further comprising:
a third transistor, wherein the third transistor is coupled between the source follower transistor and a column line.
15. The global shutter imaging pixel defined in claim 14 , further comprising:
a reset transistor, wherein the reset transistor is coupled between the floating diffusion region and a bias voltage supply line.
16. The global shutter imaging pixel defined in claim 15 , wherein the charge storage region comprises first and second storage capacitors and a fourth transistor and wherein the fourth transistor is coupled between the first and second storage capacitors.
17. The global shutter imaging pixel defined in claim 12 , wherein the first transistor is directly coupled to the charge storage region.