Systems and methods for operating image sensor pixels having different sensitivities and shared charge storage regions

Abstract

An image sensor may have control circuitry and an array of pixels having corresponding photodiodes. The pixels may be arranged into groups. Photodiodes in each of the groups may share a common charge storage region. Each photodiode has an associated sensitivity provided by a corresponding color filter element. The control circuitry may perform multiple charge transfer operations to transfer charge accumulated in high sensitivity photodiodes in the group to the shared charge storage region, may readout image signals corresponding to the transferred charge, and may combine the image signals to generate final image signals for the photodiodes. The control circuitry may transfer charge accumulated in low sensitivity photodiodes in the group to the shared charge storage region after the image signals generated by the high sensitivity photodiodes have been read out, thereby increasing the maximum signal to noise ratio of the low sensitivity photodiodes without causing charge blooming.