Digital pixel array with multi-stage readouts

An apparatus comprising:

• an array of digital pixel cells, each digital pixel cell including:
• a photodiode;
• and
• a memory device configured to store a digital output generated based on charge generated by the photodiode in an exposure period;
• and
• an image processor configured to:
• receive first digital outputs from the memory devices of a first set of digital pixel cells of the array of digital pixel cells;
• determine, from the first set of digital pixel cells, a second set of digital pixel cells of which the first digital outputs satisfy one or more first conditions;
• identify, based on the second set of digital pixel cells and one or more second conditions different from the one or more first conditions, a third set of digital pixel cells from which to receive second digital outputs generated based on charge generated by the photodiodes of the third set of digital pixel cells in the exposure period, the third set of digital pixel cells being part of the array of digital pixel cells, wherein the one or more second conditions comprise at least one of:
• the third set of digital pixel cells being at a pre-determined distance from the second set of digital pixel cells, or the third set of digital pixel cells forming a region of a pre-determined shape that encircles the second set of digital pixel cells;
• receive the second digital outputs generated by the third set of digital pixel cells;
• and
• perform one or more image processing operations based on at least the second digital outputs.