Device for determining the optical properties of samples which are arranged in a matrix arrangement in wells of a microtiter plate, comprising: a light source arrangement having at least two light sources (LQ1, LQ2) controllable by a control device, which light sources are disposed spaced from each other and configured for emission of light with different properties; an excitation optical path including devices for transmission of light of the light sources as an excitation light from a light inlet side to a measurement position located in a sample plane, in which a sample received in a well of a microtiter plate is arranged or arrangeable; a photosensitive detector; a detector optical path for transmission of light influenced by the sample from the sample to the detector; a coupling device for selective coupling of light of at least one selected light source of the light source arrangement for irradiation into the measurement position, wherein the light sources (LQ1, LQ2) of the light source arrangement are mounted stationary on different source locations, and wherein on the light inlet side of the sample plane a parabolic mirror for collecting emitted light is disposed, characterized in that the coupling device includes coupling optics embodied in a conical mirror, facetted mirror, grating or prism, which is disposed on the light inlet side of the sample plane and configured as a beam deflection device for deflecting of excitation light from different irradiation directions towards the measurement position such that excitation light deflected by the coupling optics can be irradiated from each of the light sources from the light inlet side into the measurement position, wherein the coupling optics are arranged on an optical axis of the parabolic mirror. a light source arrangement having at least two light sources (LQ1, LQ2) controllable by a control device, which light sources are disposed spaced from each other and configured for emission of light with different properties; an excitation optical path including devices for transmission of light of the light sources as an excitation light from a light inlet side to a measurement position located in a sample plane, in which a sample received in a well of a microtiter plate is arranged or arrangeable; a photosensitive detector; a detector optical path for transmission of light influenced by the sample from the sample to the detector; a coupling device for selective coupling of light of at least one selected light source of the light source arrangement for irradiation into the measurement position, wherein the light sources (LQ1, LQ2) of the light source arrangement are mounted stationary on different source locations, and wherein on the light inlet side of the sample plane a parabolic mirror for collecting emitted light is disposed, characterized in that the coupling device includes coupling optics embodied in a conical mirror, facetted mirror, grating or prism, which is disposed on the light inlet side of the sample plane and configured as a beam deflection device for deflecting of excitation light from different irradiation directions towards the measurement position such that excitation light deflected by the coupling optics can be irradiated from each of the light sources from the light inlet side into the measurement position, wherein the coupling optics are arranged on an optical axis of the parabolic mirror.