Sensor and method of operating the sensor

A method of operating a sensor having a plurality of sensor elements, each of which includes a radiation-sensitive conversion element which generates an electric signal in dependence on the incident radiation, a reset element which resets the conversion element to an initial state, and a source follower transistor whose source is connected to an active load and to one side of a sampling capacitor whose other side is connected, via a read-out switching element, to a read-out line for reading out the electric signal, wherein:

• during a measuring and read-out cycle in each sensor element the conversion element and the sampling capacitor are reset to an initial state during a first phase,
• a voltage difference which is representative of the conversion element in the initial state is adjusted across the sampling capacitor during a second phase,
• the voltage across the sampling capacitor is sustained during a third phase while the conversion element is irradiated by means of a radiation source, and during a fourth phase the voltage difference across the sampling capacitor is adjusted to a value which is representative of the conversion element after the irradiation, the variation of the potential at the side of the sampling capacitor which is connected to the read-out line being measured as a measure of the radiation incident on the conversion element.

A method of operating a sensor having a plurality of sensor elements arranged in rows and columns, each of which includes a radiation-sensitive conversion element which generates an electric signal in dependence on the incident radiation, a reset element which resets the conversion element to an initial state, and a source follower transistor whose source is connected to an active load and to one side of a sampling capacitor whose other side is connected, via a read-out switching element, to a read-out line for reading out the electric signal, the method comprising:

• exposing the sensor to radiation with the read-out switching elements closed, the radiation-sensitive conversion element causing a change in the voltage on the one side of the sampling capacitor and the read out line holding the other side of the sampling capacitor to a constant voltage;
• closing the reset elements to and opening the read out switching elements, thereby holding the conversion element to a constant state irrespective of the incident radiation;
• closing the read out switching elements of each row in turn and measuring the charge stored on the sampling capacitors for each row in turn.