Event-based computational pixel imagers

A computational pixel imaging apparatus, comprising:

• a plurality of pixels, each pixel comprising a detector configured to generate an analog signal when exposed to radiation and a pixel integrated circuit configured to convert the analog signal into at least one digital signal with at least one counter, wherein the pixel integrated circuit comprises a signal converter configured to convert the analog signal to a sequence of pulses, and a first counter configured to, in response to the sequence of pluses, accumulate a first digital number, and wherein the plurality of pixels are configured to:
• acquire a plurality of key frames at a first frequency in response to exposure of the detectors of the plurality of pixels for a first-type exposure, wherein when acquiring a key frame of the plurality of key frames, the first counter increments the first digital number for the first-type exposure;
• and
• acquire a plurality of delta frames at a second frequency in response to exposure of the detectors of the plurality of pixels for a second-type exposure, wherein when acquiring a delta frame of the plurality of delta frames, the first counter increments the first digital number for a first portion of the second-type exposure and decrements the first digital number for a second portion of the second-type exposure, and wherein the second frequency is higher than the first frequency.