Event detection for digital radiography detector

A wireless, independent digital imaging sensor utilizes an external charge balance capacitor to establish a sense voltage at a common node between the charge capacitor and the pixel intrinsic capacitors in the sensor panel. A variable width pulse train responds to the sense voltage to control injection of charge to the external capacitor to maintain a constant voltage at the common equal to a reference voltage. An increase in pulse width above a threshold level representative of the onset of X-ray exposure is detected to generate an output control signal used to control subsequent image acquisition functions of the imaging sensor.