Abstract: The system comprises a main body unit 4 which has a first terminal 7 and a head unit 6 which has a second terminal 9 attachable to and detachable from the first terminal 7 and which is attachable to and detachable from the main body unit 4. The head unit 6 has a photosensor 18 connected to the second terminal 9 and adapted to generate photocurrent according to incident optical power, and a capacitor 20 connected to the photosensor 18. The main body unit 4 has a charging circuit 31 connected to the first terminal 7 and being capable of charging the capacitor 20 while the first terminal 7 is coupled to the second terminal 9, and a reading circuit 31 capable of reading a voltage of the capacitor 20 while the first terminal 7 is coupled to the second terminal 9. The capacitor 20 is discharged as the photocurrent is generated.

Abstract: A photodetector comprising a photoemissive surface capable of liberating photoelectrons. Photoelectrons are detected by a MOSFET having a floating gate, which is suitably charged before measurement in such a way that photoelectrons can cause a change in charge of the floating gate. The detected change indicates the amount of light received by the detector.

Abstract: A method for detecting ionizing radiation by allowing the radiation to affect the surface of the floating gate of a MOSFET transistor through an air or gas space. For this purpose, an uncovered area is formed on the surface of the floating gate of the MOSFET transistor forming the detector. The MOSFET transistor is used so that a charge is formed on its floating gate, the charge changing as a result of the ionizing radiation the transistor is exposed to. The radiation dose is determined by the change which takes place in the charge on the gate.