An optical sensor apparatus to detect objects within a monitored region includes a housing having a window. A sensor includes a transmitting/receiving unit arranged inside the housing and rotatable around an axis. The transmitting/receiving unit includes a transmitter to emit light rays and a receiver to receive light rays. The transmitted light rays and the received light rays are conducted through the window in the housing. The window is optically adapted to shape the transmitted light rays and the received light rays into beams.