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FPN correction for a linear-logarithmic CMOS image sensor with a tunable linear range using two-step charge transfer

This paper presents a fixed pattern noise (FPN) correction method for a linear-logarithmic CMOS image sensor (CIS) with a tunable linear response range. The proposed method is based on a two-step charge transfer operation to calibrate the offset FPN caused by the threshold voltage variation of the transfer gate under various linear ranges. The prototype image sensor consisting of a 320 × 240 pixel array with a 2.25 μm pixel pitch is fabricated with a 0.13 μm CIS process. It is found that the offset FPN is reduced by 90 % while the linear range is tuned by 20 % of the full output range.