Patent ID: 7973841

Claim:
A imaging device comprising: a photo sensor for generating photoinduced charge carriers, wherein said photo sensor is implemented by one of the following: a pinned photo diode (PPD), a buried photo diode, and a charge-coupled device (CCD), at least one transfer gate to release said charge into at least one respective floating diffusion node, a sub-linear element connected to said at least one floating diffusion node, a sub-linear voltage source for which the voltage drop depends in a sub-linear fashion on a current through photo sensor, and a first transistor connected between said floating diffusion and a sense node, and a second transistor between said sense node and a reset voltage, a third transistor, a fourth transistor, a source follower and a select transistor for measuring a measured voltage indicative of a voltage at said floating diffusion node, a control circuitry adapted to run at least one measuring cycle, wherein each measuring cycle comprises the following three phases: a) in a first phase, said control circuit issues a first reset command to said second transistor and toggles a shutter signal high, and transfer gate between a spill-over voltage and a charge transfer voltage to completely empty the pinned photodiode storage node of the PPD, b) in a second phase, a select signal of a pixel is controlled to measure a pixel's first reset voltage, then puts the shutter signal high to measure a the pixel's sub-linear signal voltage, and issues a second reset command based on the measurement, and c) in a third phase, said control circuit controls the pixel select signal to measure the pixel's second reset voltage, then puts the shutter signal high and operates the transfer gate to generate the pixel's fourth linear signal voltage.