Method of operating image sensor and image sensor performing the same

An image sensor comprising:

• a pixel array including a plurality of first pixels, a plurality of second pixels, a plurality of third pixels and a plurality of floating diffusions, the pixel array configured to output a plurality of first reset signals by resetting the plurality of floating diffusions in a first reset period, to output a plurality of first analog pixel signals in a first signal period, to output a plurality of second reset signals by resetting the plurality of floating diffusions in a second reset period, to output a plurality of second analog pixel signals in a second signal period, and to output a plurality of third analog pixel signals in a third signal period, the plurality of first analog pixel signals being outputted from the plurality of first pixels, the plurality of second analog pixel signals being outputted from the plurality of second pixels, the plurality of third analog pixel signals being outputted from the plurality of second pixels and the plurality of third pixels;
• an analog-to-digital converter configured to output a plurality of first digital signals based on the plurality of first analog reset signals and the plurality of first analog pixel signals, to output a plurality of second digital signals based on the plurality of second analog reset signals and the plurality of second analog pixel signals, and to output a plurality of third digital signals based on the plurality of second analog reset signals and the plurality of third analog pixel signals;
• an auto focus (AF) circuit configured to perform an AF operation based on the plurality of first digital signals and the plurality of second digital signals;
• and
• a high dynamic range (HDR) circuit configured to perform an HDR merging operation based on the plurality of first digital signals, the plurality of second digital signals, and the plurality of third digital signals, and
• wherein at least one of the plurality of first pixels, at least one of the plurality of second pixels, and at least one of the plurality of third pixels are configured to share one of the plurality of floating diffusions.