Device for measuring radiation absorption or emission. [external radiation source for calibration]

A device for correcting measuring values of a group of radiation detectors for measuring the intensity or distribution of radiation, comprising an additional radiation source for direct irradiation of the detectors is described. The radiation of the said additional radiation source can be switched on each time when the radiation to be measured is not incident on the radiation detectors. The device furthermore comprises a calculating device which forms for each radiation detector the quotient of the measuring value (M1(x)) and the reference measuring value (M2(x)) of the radiation detectors when exposed to the radiation of the additional radiation source.