Pixel array and image sensor including the same

1. A pixel array, comprising:

a plurality of sub-pixels adjacent to each other and a readout circuit connected to the plurality of sub-pixels through a floating diffusion node, wherein:

each of the plurality of sub-pixels includes:

a photoelectric conversion element configured to accumulate photocharges generated due to reflected light that is incident thereto;

an overflow transistor connected to the photoelectric conversion element;

a phototransistor connected to the photoelectric conversion element and the overflow transistor; and

a storage element connected to the phototransistor wherein the phototransistor is configured to provide the photocharges accumulated in the photoelectric conversion element to the storage element, and

the readout circuit includes:

a reset transistor connected to the floating diffusion node;

a driver transistor including a gate electrode connected to the floating diffusion node; and

a selection transistor connected to the driver transistor.

2. The pixel array as claimed in claim 1 , wherein:

the plurality of sub-pixels include a first sub-pixel and a second sub-pixel adjacent to the first sub-pixel in a same row or column as the first sub-pixel, and

the first sub-pixel and the second sub-pixel are connected to the floating diffusion node.

3. The pixel array as claimed in claim 2 , wherein:

the plurality of sub-pixels further include a third sub-pixel adjacent to the first sub-pixel and a fourth sub-pixel adjacent to the second sub-pixel and the third sub-pixel, and

the first sub-pixel, the second sub-pixel, the third sub-pixel, and the fourth sub-pixel are connected to the floating diffusion node.

4. The pixel array as claimed in claim 1 , wherein a first end of the photoelectric conversion element is connected to the phototransistor and the overflow transistor, and a second end of the photoelectric conversion element is connected to a ground voltage.

5. The pixel array as claimed in claim 1 , wherein each of the plurality of sub-pixels further includes a shutter transistor connected between the phototransistor and the storage element.

6. The pixel array as claimed in claim 1 , wherein the storage element includes at least one of:

a storage transistor connected between the phototransistor and the floating diffusion node, or

a storage diode electrically connected to the phototransistor between the phototransistor and the floating diffusion node.

7. The pixel array as claimed in claim 1 , wherein the readout circuit further includes:

a capacitor; and

a control transistor electrically connected to the floating diffusion node, the control transistor being configured to electrically connect the floating diffusion node to the capacitor in response to a gain control signal.

8. An image sensor, comprising:

a row decoder configured to generate an overflow gate signal;

a pixel array including first to fourth sub-pixels; and

a photogate controller configured to provide a plurality of photogate signals to the first to fourth sub-pixels, wherein:

each of the first to fourth sub-pixels includes:

a photoelectric conversion element configured to accumulate photocharges generated due to reflected light that is reflected by an object;

a storage element configured to accumulate the photocharges accumulated in the photoelectric conversion element;

an overflow transistor configured to provide a power supply voltage to the photoelectric conversion element in response to the overflow gate signal; and

a phototransistor configured to electrically connect the photoelectric conversion element to the storage element in response to a photogate signal that is previously determined according to a position of a sub-pixel, from among the plurality of photogate signals, and

the photogate controller provides first to fourth photogate signals having respectively different phase differences of 0°, 90°, 180°, and 270° with respect to modulated light incident to the object to the first to fourth sub-pixels, respectively, during an integration period.

9. The image sensor as claimed in claim 8 , wherein:

the overflow gate signal toggles between a turn-on level and a turn-off level during the integration period, and

the photogate signal that is previously determined according to the position of the sub-pixel toggles with a phase difference of 180° with respect to the overflow gate signal, during the integration period.

10. The image sensor as claimed in claim 9 , wherein:

each of the first to fourth sub-pixels further includes a shutter transistor configured to electrically connect the phototransistor to the storage element in response to a shutter control signal, and

the shutter control signal is at a turn-on level during the integration period.

11. The image sensor as claimed in claim 8 , wherein the overflow gate signal is at a turn-on level during the integration period.

12. The image sensor as claimed in claim 8 , wherein:

the storage element includes a storage transistor configured to accumulate the photocharges accumulated in the photoelectric conversion element, in response to a storage control signal, and

the storage control signal is at a turn-on level during the integration period.

13. An image sensor, comprising:

a row decoder configured to generate an overflow gate signal and a shutter control signal;

a photogate controller configured to generate a photogate signal;

a pixel array including first sub-pixels connected to a first floating diffusion node, a first readout circuit connected to the first floating diffusion node, second sub-pixels connected to a second floating diffusion node, and a second readout circuit connected to the second floating diffusion node; and

a signal processor configured to generate a color image and a depth image of an object, based on a plurality of pixel signals output by the pixel array, wherein:

at least one of the first sub-pixels includes a color pixel configured to generate a pixel signal for the color image, and

at least one of the second sub-pixels includes a distance pixel configured to generate a pixel signal for the depth image,

each of the color pixel and the distance pixel includes:

a photoelectric conversion element configured to accumulate photocharges generated due to reflected light reflected from the object;

a storage element configured to accumulate photocharges accumulated in the photoelectric conversion element;

an overflow transistor configured to provide a power supply voltage to the photoelectric conversion element in response to the overflow gate signal;

a phototransistor configured to provide the photocharges accumulated in the photoelectric conversion element, to the storage element, in response to the photogate signal; and

a shutter transistor configured to electrically connect the phototransistor to the storage element in response to the shutter control signal, and

the photogate signal is at a turn-on level during an integration period.

14. The image sensor as claimed in claim 13 , wherein the first sub-pixels include first to third color pixels of different colors and a distance pixel, and the second sub-pixels include first to third color pixels of different colors and a distance pixel.

15. The image sensor as claimed in claim 13 , wherein:

the first sub-pixels include color pixels,

at least two of the color pixels include color pixels of a same color, and

the second sub-pixels include distance pixels.

16. The image sensor as claimed in claim 15 , wherein:

the row decoder is configured to simultaneously provide first to fourth shutter control signals having respectively different phase differences of 0°, 90°, 180°, and 270° with respect to modulated light, which is incident to the object, to the second sub-pixels, respectively, during the integration period, and

the second sub-pixels include a first distance pixel configured to receive the first shutter control signal, a second distance pixel configured to receive the second shutter control signal, a third distance pixel configured to receive the third shutter control signal, and a fourth distance pixel configured to receive the fourth shutter control signal.

17. The image sensor as claimed in claim 13 , wherein:

the overflow gate signal toggles between a turn-on level and a turn-off level during the integration period, and

the shutter control signal toggles with a phase difference of 180° with respect to the overflow gate signal during the integration period.

18. The image sensor as claimed in claim 13 , wherein:

the overflow gate signal is at a turn-on level during the integration period, and

the shutter control signal toggles between a turn-on level and a turn-off level during the integration period.

19. The image sensor as claimed in claim 13 , wherein the shutter control signal is at a turn-on level during the integration period.

20. The image sensor as claimed in claim 19 , wherein the overflow gate signal maintains a turn-off level during the integration period.