The invention relates to a device for the IR-spectrometric analysis of a solid, liquid or gaseous medium. The device includes a process probe, which has a reflection element. The device additionally includes a linear variable filter, at least one detector element, and a control/evaluation unit. At least one light source is also provided, the light of which is coupled into the reflection element via a collimating optics. At least one optical waveguide having a light input section and a light output section is provided. The light is guided via the light output section of the optical waveguide into a defined region of the linear variable filter. The detector element and the linear variable filter are arranged movably relative to one another over approximately the length of the linear variable filter. The control/evaluation unit determines the spectrum of the medium on the basis of the measured values delivered from the detector element.