The present invention relates to a device for the detection of a fluorescent dye in samples, comprising a device for exciting the fluorescent dye to be detected, said device comprising a surface provided for the application of samples and an excitation light coupling device by means of which excitation light from a predefined direction of impingement can be coupled into the device in such a way that, by means of an evanescent field of the coupled light, the fluorescent dye to be detected can be excited in the samples applied, and further comprising a means for the detection of the fluorescent light emitted by the fluorescent dye to be detected. The present invention is characterized in that the device for exciting the fluorescent dye to be detected is provided in such a way that the surface to which the samples are to be applied is movable relative to the direction of impingement so as to excite the fluorescent dye to be detected in different subsections of said surface.