Apparatus for checking value documents , in particular bank notes, comprising - at least two radiation sources for emitting electromagnetic radiation by means of which a value document is irradiated, - at least one sensor (21-23) for detecting the electromagnetic radiation reflected and/or transmitted by the value document and generating corresponding sensor signals ( R ), with components ( R k ) assigned to the radiation sources , wherein the sensor signals are corresponding reflection and/or transmission signals, and - an evaluation device , which is designed to check the value documents on the basis of corrected sensor signals and to derive these corrected sensor signals ( BR ; r 1 ) from the sensor signals taking into account at least one spectral property ( S k ( λ ), S ki ; a k , a) of the electromagnetic radiation of the at least two radiation sources , wherein during the derivation of the corrected sensor signals ( BR ; r 1 ), at least one linear combination is formed from components of the sensor signals ( BR ; r 1 ) assigned to the different radiation sources (R k ), wherein the at least one spectral property (a k , a) of the electromagnetic radiation of the radiation source is given by at least one parameter ( a k , a) which characterizes one or more spectral parts of the electromagnetic radiation of the radiation source , and wherein at least one first parameter (a 1 ) characterizes the spectral part of a main emission of the electromagnetic radiation of the radiation sources and at least one second parameter (a 2 ) characterizes the spectral part of a secondary emission of the electromagnetic radiation of the radiation sources . - at least two radiation sources for emitting electromagnetic radiation by means of which a value document is irradiated, - at least one sensor (21-23) for detecting the electromagnetic radiation reflected and/or transmitted by the value document and generating corresponding sensor signals ( R ), with components ( R k ) assigned to the radiation sources , wherein the sensor signals are corresponding reflection and/or transmission signals, and - an evaluation device , which is designed to check the value documents on the basis of corrected sensor signals and to derive these corrected sensor signals ( BR ; r 1 ) from the sensor signals taking into account at least one spectral property ( S k ( λ ), S ki ; a k , a) of the electromagnetic radiation of the at least two radiation sources , wherein during the derivation of the corrected sensor signals ( BR ; r 1 ), at least one linear combination is formed from components of the sensor signals ( BR ; r 1 ) assigned to the different radiation sources (R k ), wherein the at least one spectral property (a k , a) of the electromagnetic radiation of the radiation source is given by at least one parameter ( a k , a) which characterizes one or more spectral parts of the electromagnetic radiation of the radiation source , and wherein at least one first parameter (a 1 ) characterizes the spectral part of a main emission of the electromagnetic radiation of the radiation sources and at least one second parameter (a 2 ) characterizes the spectral part of a secondary emission of the electromagnetic radiation of the radiation sources . wherein the at least one spectral property (a k , a) of the electromagnetic radiation of the radiation source is given by at least one parameter ( a k , a) which characterizes one or more spectral parts of the electromagnetic radiation of the radiation source , and wherein at least one first parameter (a 1 ) characterizes the spectral part of a main emission of the electromagnetic radiation of the radiation sources and at least one second parameter (a 2 ) characterizes the spectral part of a secondary emission of the electromagnetic radiation of the radiation sources . <EOS>