Active pixel intraoral radiological image sensor and associated image capture method

Abstract

The subject matter of the invention is an active pixel dental radiological image sensor, with integrated X-ray occurrence detection, which uses the pixels of the matrix to detect the start of an X-ray flash, by detecting the current produced by all the photodiodes in the matrix. A switching circuit MUXthus allows, in a first phase of detecting the start of an X-ray flash, a common connection node NC to be connected that corresponds to the drain of a photodiode initialisation transistor Mat the input of a current-voltage conversion detection circuit DTX, which provides as output a signal for detecting the start of an X-ray flash when the current produced by all the photodiodes of the matrix exceeds a predetermined threshold. The switching circuit MUXis then controlled to connect the common connection node NC of the pixels to a photodiode re-initialisation voltage source, VRS. In an alternative embodiment, some pixels of the matrix can be used to detect the end of an X-ray flash using the same principle, by injecting the current produced by the photodiodes of these pixels that is collected on a different common connection node, electrically isolated from the first, with the end of flash signal corresponding to a variation in this current, which falls below a predetermined threshold. The active pixels can be of the three or more transistor type, in particular with five and more transistors.