The present invention provides a radiation sensor (104) that has a plurality of sensor elements, wherein each sensor element has a photoelectric detection portion and an integrated current to frequency converter for a built-in analog digital conversion of an acquired analog signal being indicative of an intensity of electromagnetic radiation impinging on the photoelectric detection part. Typically, the detector element corresponds to a pixel of a light detector, such as a photodiode. Preferably, the current to frequency converter as well as the photoelectric conversion portion are arranged besides one another on a common substrate and are implemented on the basis of CMOS technology allowing for a costs efficient mass production of the radiation sensor.