An assembly for an optical read out device for biochips, in which in a manner known per se an optical path of light that is emitted from the samples is evaluated by a CCD camera. For this purpose, the samples are illuminated by a light source, which e.g. stimulates fluorescence in the samples. According to the invention, the light source consists of luminescent, porous silicon. The latter can constitute the surface of a luminous disc, which extends parallel to an analysis plane that is formed by the sample carrier. This allows the light source to be directly connected to the sample carrier, obviating the need for complex optical systems for distributing the light evenly from a punctiform or linear light source to the samples. The light source is particularly cost-effective and the required light intensity is low. The luminous disc can be simply produced by the etching of a silicon substrate.