Method and device for measuring electromagnetic waves emanating from a melt

In a method for determining electromagnetic waves originating from the interior of a melt (3), in particular a metal melt, a gas-filled hollow space (26) is formed within the melt (3) by blowing in gas and electromagnetic waves emitting from the melt (3) are observed through the blown-in gas and evaluated by feeding the electromagnetic waves via an optical system (20) to a detector (22) for determining the temperature and/or chemical composition.In order to avoid falsifications of the measured values, the emitting electromagnetic waves are cleared from electromagnetic waves (36, 37, 39, 40) directed obliquely to the optical axis (38) of the optical system (20) and present beyond a limit radius (41) drawn from the optical axis (38) of the optical system (20), by refracting said electromagnetic waves (36, 37, 39, 40) away from the optical axis (38) of the optical system (20) in a wave dispersion means (42) of the optical system (20) and only electromagnetic waves directed approximately parallel to the optical axis (38) of the optical system (20) arrive at a detector (22) arranged to follow the optical system (20), and/or the optical system (20) is moved relative to the hollow space (26) while adjusting its optical axis (38), until the intensity of the emitting electromagnetic waves yields a maximum during evaluation of the same (FIG. 2).