Calculating Global Overlap Windows in Sequential Row Readout Image Sensors
Calculate global overlap by subtracting array readout time from total exposure; fire external illumination within this window to emulate global shuttering.
Floating Diffusion Node
Readout Component
Capacitive elements located at the heart of a pixel structure transform collected charge into a measurable voltage signal during the sensing cycle. The floating diffusion node acts as the final storage site for electrons transferred from the photodiode before they reach the amplifier. Its capacity determines the maximum signal level the pixel can handle before saturation occurs.
Conversion Gain
Sensitivity is defined by the relationship between the number of electrons and the resulting voltage swing at the output. A small floating diffusion node produces a higher voltage for each electron which improves the signal to noise ratio in low light conditions. Large capacity nodes are used when high full well capacity is required for bright environments.
Reset Action
Clearing the charge from previous frames is necessary to prepare the sensor for a new measurement. A reset transistor pulls the floating diffusion node to a reference voltage to ensure a clean starting point. Any kTC noise generated during this reset must be removed using correlated double sampling.
Transfer Efficiency
Potential barriers between the photodiode and the storage area must be carefully managed to ensure all electrons move across the junction. Incomplete transfer leaves residual charge that appears as lag or ghosting in subsequent frames.