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.
Dark Current Accumulation
Thermal Noise
Charge carriers generated within the substrate of an image sensor through thermal excitation in the absence of light represent a fundamental limit on low light performance. This dark current accumulation happens continuously while the sensor is powered and occurs even in total darkness. Silicon impurities or crystal defects provide the energy states necessary for electrons to jump into the conduction band.
Exposure Impact
Integration time determines how much noise builds up before the signal is read out from the pixel. Longer exposures result in higher levels of dark current accumulation which reduces the dynamic range available for the actual image. Cooling the sensor substrate is the most effective way to manage this effect.
Correction Method
Black level subtraction uses shielded pixels at the edge of the array to measure the current baseline and remove it from the final value. This subtraction addresses the average level but cannot remove the shot noise associated with dark current accumulation itself. Fixed pattern noise arises when specific pixels exhibit higher leakage than their neighbors.
Temperature Sensitivity
Leakage rates typically double for every six to eight degrees Celsius increase in the operating temperature. High precision applications require active thermal stabilization or thermoelectric coolers to maintain a predictable noise floor.