Imaging method and system

An example imaging system including a detector, a transconductance amplifier, a charge integrator, and a current mirror is disclosed. The detector is coupled to a first current and configured to accumulate charges in response to light or radiation. The transconductance amplifier is configured to receive a pixel voltage of the detector and generate a second current according to the pixel voltage, wherein the pixel voltage is associated with the accumulated charges and the first current. The charge integrator is configured to generate an output signal according to a third current. The current mirror is configured to generate the first current and the third current according to the second current so that the first current gradually decreases as the pixel voltage approaches a reference voltage.