Optoelectronic sensor for measuring direct solar radiation in e.g. parabolic trough solar power plant in roof of building, has protection window, case and housing that are arranged in optical path immediately in front of sensing element

The sensor has a collimator pipe (14) for adjusting an acceptance angle (theta) to a circular entry aperture (26). A protection window (11), a case and a metallic housing protect a sensing element (16) against environmental influences e.g. rain and moisture, and are arranged within the pipe in an optical path immediately in front of or in the sensing element. The sensing element is arranged on a sensor carrier (20) that functions as a heat sink. Two collimator diaphragms (13, 30) and a sensor diaphragm (5) are arranged in regions of the pipe and the sensing element, respectively.