Pixel structure, image sensor device and system with pixel structure, and method of operating the pixel structure
A photodetector in semiconductor material is provided with a first transfer gate between the photodetector and a first diffusion region in the semiconductor material, a second transfer gate between the photodetector and a second diffusion region in the semiconductor material, a capacitor connected between the first diffusion region and the second diffusion region, a first switch connected between the first diffusion region and a first reference voltage, and a second switch connected between the second diffusion region and a second reference voltage.
1. A pixel structure for a semiconductor imaging device, comprising:
a photodetector in a semiconductor material;
a first transfer gate between the photodetector and a first diffusion region in the semiconductor material;
a second transfer gate between the photodetector and a second diffusion region in the semiconductor material;
a capacitor connected between the first diffusion region and the second diffusion region;
a first switch connected between the first diffusion region and a first reference voltage;
a second switch connected between the second diffusion region and a second reference voltage; and
a select transistor connected to a column bus.
2. The pixel structure according to claim 1 , wherein
the photodetector is a pinned photodiode in a substrate comprising the semiconductor material.
3. The pixel structure according to claim 1 , further comprising:
buffer amplifiers connected to the first diffusion region and the second diffusion region.
4. The pixel structure according to claim 1 , wherein the first reference voltage and the second reference voltage are equal.
5. The pixel structure according to claim 4 , wherein the first reference voltage and the second reference voltage are equal to a supply voltage.
6. The pixel structure according to claim 1 , wherein the first reference voltage or the second reference voltage is connected to a supply voltage.
7. The pixel structure according to claim 1 , further comprising:
a source follower formed by a field-effect transistor, which is connected to the select transistor, a gate of the source follower connected to the first diffusion region.
8. An image sensor device comprising a two-dimensional array of pixel structures according to claim 1 .
9. An imaging system including an image sensor device according to claim 8 , further comprising:
a light source synchronized to the image sensor device, wherein the light source is configured to be active when the signal is acquired on the first diffusion region and not active when the signal is acquired on the second diffusion region, or vice versa.
10. The imaging system according to claim 9 , wherein
the light source is configured to project a pattern or sequence of patterns on a scene to be imaged.
11. A method of operating the pixel structure according to claim 1 , comprising:
discharging the capacitor by closing both the first switch and the second switch into a connecting state,
acquiring a first signal on the photodetector and transferring the first signal to the first diffusion region by a charge transfer pulse on the first transfer gate, while the second switch is closed in a connecting state,
acquiring a second signal on the photodetector and transferring the second signal to the second diffusion region by a charge transfer pulse on the second transfer gate, while the first switch is closed in a connecting state, and
after acquisition of the signals, reading the pixel signal out from the first diffusion region while the second diffusion region is connected to the second reference voltage via the second switch.
12. The method according to claim 11 , wherein
the second transfer gate is at a higher electric potential than the first transfer gate during readout of the pixel signal.
13. The method according to claim 11 , wherein
first and second signals are repeatedly acquired and accumulated on the capacitor.
14. The method according to claim 11 , wherein
at least one of the charge transfer pulse on the first transfer gate and the charge transfer pulse on the second transfer gate is a multiple pulse.
15. The method according to claim 11 , wherein the operation of the pixel structure is synchronously performed with the operation of a structured-light projector.
16. A pixel structure for a semiconductor imaging device, comprising:
a photodetector in a semiconductor material;
a first transfer gate between the photodetector and a first diffusion region in the semiconductor material;
a second transfer gate between the photodetector and a second diffusion region in the semiconductor material;
a capacitor connected between the first diffusion region and the second diffusion region;
a first switch connected between the first diffusion region and a first reference voltage; and
a second switch connected between the second diffusion region and a second reference voltage,
wherein the first reference voltage is different than the second reference voltage.
17. A pixel structure for a semiconductor imaging device, comprising:
a photodetector in a semiconductor material;
a first transfer gate between the photodetector and a first diffusion region in the semiconductor material;
a second transfer gate between the photodetector and a second diffusion region in the semiconductor material;
a capacitor connected between the first diffusion region and the second diffusion region;
a first switch connected between the first diffusion region and a first reference voltage;
a second switch connected between the second diffusion region and a second reference voltage; and
a light source synchronized to the image sensor device, wherein the light source is configured to be active when the signal is acquired on the first diffusion region and not active when the signal is acquired on the second diffusion region, or vice versa.