Imager pixel

Abstract

An imager pixel comprising a forward-biased photo-detector with readout transistor for light-to-current conversion, and a ratiometric readout system comprising a current to pulse width converter. The readout system operates in a light mode to: generate a first current proportional to a photodetector current and a leakage current, on exposure to a photodetector voltage; and convert the first current to a first pulse width; and operates in a least significant bit (LSB) mode to: generate a second current proportional to a least significant bit (LSB) current and the leakage current, on exposure to a gate-source voltage; and convert the second current to a second pulse width. The system includes a converter circuit for converting the first pulse width to a count (CNTB) and the second pulse width to a count (CNTA), and a counting circuit for providing a radiometric readout based on a ratio of CNTB to CNTA.

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