Abstract: A microscope with continuously or discontinuously variable objective magnification is provided with an autofocus system whose beam path passes through the objective and is directed out of the imaging beam path of the microscope between objective and eye piece to at least one photo-electric detector means. At least one optical system is located or locatable in the beam path of the autofocus system which allows or causes the at least one image formed on the detector means to be altered in scale when a change in the objective magnification occurs. The at least one optical system can be a zoom system or a series of lenses or fixed lens systems arranged to be inserted into the beam path of the focusing system. When the objective or objective magnification is changed, a coupling mechanism serves to appropriately vary the focal length of the at least one optical system located or locatable in the beam path of the autofocus system.