A rain sensor system (1) for detecting rain on a window (101) of a vehicle (100), comprising: a camera device (2) configured to capture images (14) of an area surrounding the vehicle (100) which is located in a field of view (103) of the camera device (2); and multiple rain sensors (5) which are arranged on the window (101) and at least partially in the field of view (103) of the camera device (2), each rain sensor (5) comprising: a light guide (7) which is configured to guide light from a light source (6) to a 10 light injection point (8) at which the light is injected into the window (101), and a receiver (9) configured to receive the light injected into the window (101) and guided to the receiver (9) through the window (101), and to guide the received light to the camera device (2).