The operation microscope (100), has an illumination device (101) for providing illumination light in an operation area. An intensity adjustment device for adjusting the intensity of the illumination light (116), is directed to the operation area, between a maximum value and a minimum value. A control device (170) is provided for the illumination device that has an activating module (172). A signal generator (175) emits a warning signal, when an intensity of the illumination light is adjusted over the activating module, which exceeds the safe threshold value stored in memory.
