Device for controlling visibility

A method for controlling visibility by using a visibility control device, the 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 at a first side of the device, and a second viewing region 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 viewing region to the first viewing region, wherein the device at the same time allows a first observer located in the first viewing region to view from the first viewing region to the second viewing region through the device,
• wherein the device comprises a first sensor for measuring illumination level in the first viewing region,
• wherein the device comprises a second sensor for measuring illumination level in the second viewing region,
• and wherein the device is arranged to control the intensity of the deflected light according to the measured illumination level in the first viewing region and according to the measured illumination level in the second viewing region,
• the method comprising:
• placing an auxiliary sensor to a measurement position in the second viewing region,
• selecting one or more parameters of a control system of the device by using the auxiliary sensor at said measurement position for detecting an intensity of object light transmitted from the first viewing region to the second viewing region through the substrate, and
• using the visibility control device to project the deflected light to the second viewing region,
• wherein the object light is received from an object located in the first viewing region, and
• wherein the intensity of the projected deflected light is selected to be greater than or equal to the intensity of the object light transmitted from the first viewing region to the second viewing region through the substrate.