A visibility control device, comprising: - one or more light sources to provide input light, and - a waveguiding substrate, which has a first major surface and a second major surface, wherein an out-coupling region of the substrate comprises a plurality of grooves implemented on the first major surface and/or on the second major surface, wherein the device is arranged to form guided light by coupling the input light into the substrate, wherein the grooves are arranged to form deflected light by coupling the guided light out of the substrate through the second major surface of the substrate, wherein the device has a first viewing region (ZONE1) at a first side of the device, and a second viewing region (ZONE2) at a second side of the device, wherein the device is arranged to provide the deflected light such that the deflected light prevents a second observer from viewing from the second region (ZONE2) to the first region (ZONE1), wherein the device at the same time allows a first observer located in the first region to view from the first region (ZONE1) to the second region (ZONE2) through the device, wherein the device comprises a sensor for measuring illumination level (E 22) in the second region (ZONE2), and wherein the device is arranged to control the intensity of the deflected light according to the measured illumination level (E 22) in the second region (ZONE2), characterized in that the device comprises a different sensor for measuring illumination level (E 11) in the first region (ZONE1), wherein the device is arranged to control the intensity of the deflected light according to the measured illumination level (E 11) in the first region (ZONE1) and according to the measured illumination level (E 22) in the second region (ZONE2). - one or more light sources to provide input light, and - a waveguiding substrate, which has a first major surface and a second major surface, wherein an out-coupling region of the substrate comprises a plurality of grooves implemented on the first major surface and/or on the second major surface, wherein the device is arranged to form guided light by coupling the input light into the substrate, wherein the grooves are arranged to form deflected light by coupling the guided light out of the substrate through the second major surface of the substrate, wherein the device has a first viewing region (ZONE1) at a first side of the device, and a second viewing region (ZONE2) at a second side of the device, wherein the device is arranged to provide the deflected light such that the deflected light prevents a second observer from viewing from the second region (ZONE2) to the first region (ZONE1), wherein the device at the same time allows a first observer located in the first region to view from the first region (ZONE1) to the second region (ZONE2) through the device, wherein the device comprises a sensor for measuring illumination level (E 22) in the second region (ZONE2), and wherein the device is arranged to control the intensity of the deflected light according to the measured illumination level (E 22) in the second region (ZONE2), characterized in that the device comprises a different sensor for measuring illumination level (E 11) in the first region (ZONE1), wherein the device is arranged to control the intensity of the deflected light according to the measured illumination level (E 11) in the first region (ZONE1) and according to the measured illumination level (E 22) in the second region (ZONE2). wherein an out-coupling region of the substrate comprises a plurality of grooves implemented on the first major surface and/or on the second major surface, wherein the device is arranged to form guided light by coupling the input light into the substrate, wherein the grooves are arranged to form deflected light by coupling the guided light out of the substrate through the second major surface of the substrate, wherein the device has a first viewing region (ZONE1) at a first side of the device, and a second viewing region (ZONE2) at a second side of the device, wherein the device is arranged to provide the deflected light such that the deflected light prevents a second observer from viewing from the second region (ZONE2) to the first region (ZONE1), wherein the device at the same time allows a first observer located in the first region to view from the first region (ZONE1) to the second region (ZONE2) through the device, wherein the device comprises a sensor for measuring illumination level (E 22) in the second region (ZONE2), and wherein the device is arranged to control the intensity of the deflected light according to the measured illumination level (E 22) in the second region (ZONE2), characterized in that the device comprises a different sensor for measuring illumination level (E 11) in the first region (ZONE1), wherein the device is arranged to control the intensity of the deflected light according to the measured illumination level (E 11) in the first region (ZONE1) and according to the measured illumination level (E 22) in the second region (ZONE2).