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.
Coincident Exposure
Integration Mode
Simultaneous photon collection across an entire detector surface ensures that every pixel records light from the same temporal window. Use of coincident exposure eliminates the spatial distortion seen when different rows are captured at different times. This approach is standard in global shutter sensors used for high speed machine vision applications.
Timing Accuracy
Precise synchronization signals trigger the start and stop of light gathering for all photosites at once. Within a system utilizing coincident exposure the jitter between the first and last pixel must be kept to a few nanoseconds to maintain data validity.
Charge Storage
Pixels must hold the accumulated signal in a shielded area until the readout process begins. The design of coincident exposure circuitry requires additional transistors in each pixel to facilitate this intermediate storage which reduces the overall light sensitive area. This extra hardware introduces dark current noise because the storage node is susceptible to thermal charge generation while waiting for the scan pulse.
Image Fidelity
Motion blur remains uniform across the frame when objects move during the capture interval. Because coincident exposure captures a single instant, the relative position of moving parts in a scene remains geometrically accurate for metrological analysis.