A method is disclosed for contactless determination of product characteristics, particularly in continuous or discontinuous fabrication of layer systems formed of a plurality of layers with different optical characteristics. The measuring apparatus and measurement methods for determining the characteristics of one of the respective layers are predetermined depending on the optical characteristics of this layer and depending on the optical characteristics of layers situated above it in the measuring direction. In a measuring device for this purpose, a plurality of detectors are provided for wavelength regions directly adjoining one another. The detectors and the signal processing device are constructed such that the light coming from the measurement surface with wavelengths of 200 nm to more than 2400 nm is evaluated in its entirety.