Abstract: The daylight enters the room through at least one inner light port which is limited at the top by a flat upper reflector and at the bottom by a parabolic lower reflector. A diagonal beam having a diagonal angle passes through the upper edge of the inlet window and through the lower edge of the inner window. All of the light entering through the light port is emitted into the room above the diagonal beam. To accomplish this, the lower reflector represents, in cross-section, part of a parabola whose main axis passes through the upper edge of the inlet window, and which forms with the vertical an upwardly directed main axis angle. Also, the angle of inclination measured from the main axis of the upper reflector is equal to half the diagonal angle measured in relation to the main axis. By superimposing an outer light port, a given window surface can be better exploited and can be protected from interference light entering from below.