Image sensor simultaneously generating image and proximity signals
An image sensor for simultaneously obtaining an image and a proximity is provided. The image sensor includes a proximity signal generating circuit configured to generate a proximity signal of a target based on a pixel signal of a pixel array. The proximity signal generating circuit generates the proximity signal based on an average of pixel signals output from a plurality of pixels included in the pixel array.
1. An image sensor, comprising:
a pixel array configured to generate a pixel signal based on light reflected from a target;
a voltage processing circuit configured to generate a reduced voltage pixel signal based on a difference between a voltage of the pixel signal and a reset voltage of a floating diffusion (FD) node of the pixel array and a photodiode of the pixel array;
an analog-to-digital converter (ADC) configured to generate an image signal of the target based on the pixel signal; and
a proximity signal generating circuit configured to generate a proximity signal of the target based on an average of pixel signals output from a row of pixels included in the pixel array.
2. The image sensor of claim 1 , wherein the proximity signal generating circuit is further configured to generate a proximity signal of the row of pixels included in the pixel array and a proximity signal of another row of pixels included in the pixel array by accumulating the average of the pixel signals output from the row of pixels included the pixel array and an average of pixel signals output from the another row of pixels included in the pixel array, respectively.
3. The image sensor of claim 1 , further comprising a low-voltage processing circuit configured to generate a reduced voltage pixel signal based on a difference between a voltage of the pixel signal and a reset voltage of a floating diffusion (FD) node of the pixel array and a photodiode of the pixel array.
4. The image sensor of claim 3 , wherein the voltage of the pixel signal is detected at the FD node when a shutter between the FD node and the photodiode is closed after the FD node and the photodiode are exposed for a period of time with the shutter open.
5. The image sensor of claim 1 , further comprising an averaging circuit comprising capacitors and switches, and configured to generate the average of the pixel signals.
6. The image sensor of claim 5 , wherein the average of the pixel signals is generated by closing capacitors.
7. The image sensor of claim 5 , wherein the average of the pixel signals is further generated by an averaged voltage being read out to a PX line through an analog buffer, and sampled to the ADC.
8. A method of sensing an image, the method comprising:
generating, by a pixel array, a pixel signal based on light reflected by a target, wherein the generating of the pixel signal comprises generating a reduced voltage pixel signal based on a difference between a voltage of the pixel signal and a reset voltage of a floating diffusion (FD) node of a pixel array and a photodiode of the pixel array;
generating an image signal of the target based on the pixel signal; and
generating a proximity signal of the target based on an average of pixel signals output from a row of pixels included in the pixel array.
9. The method of claim 8 , wherein the generating of the proximity signal comprises generating a proximity signal of the row of pixels included in the pixel array and another row of pixels included in the pixel array by accumulating the average of the pixel signals output from the row of pixels included in the pixel array and an average of pixel signals output from the another row of pixels included in the pixel array, respectively.
10. The method of claim 8 , further comprising determining a depth of the target based on an intensity of the proximity signal.