PD-storage dual-capture variable wide dynamic range CMOS image sensor

Proposed is a wide dynamic range CMOS image sensor (CIS) using the PD-storage dual capture (PDS-DC) method that can be applied to a 4-T active pixel sensor without any pixel modification. Dynamic range is increased by controlling the transfer gate during the integration time that is divided into two phases: long-exposure and short-exposure. The photon generated charges for both phases are stored in the photodiode (PD) while the excess charge is drained to VDD during the long-exposure. This feature allows variable dynamic range adjustment by controlling the exposure time ratio and bias voltage that determines the well-capacity during the long-exposure. The prototype sensor is fabricated using 0.13 µm CIS process. The major advantage of the proposed PDS-DC is that it provides complete correlated double sampling. Measurement results demonstrate variable wide dynamic range feature. The effects of process variation are also presented.