An optical device for enlarging an eye box, the optical device comprising: a first optical expander being carried by, or formed in, a first light-transmissive substrate engaging a first plane; and a second optical expander being carried by, or formed in, a second light-transmissive substrate engaging a second plane being spaced apart from the first plane. An electromagnetic emitter and an electromagnetic detector are positioned on opposite sides of the heat sink. If a controller serving the user terminal is faulty, a home database, which stores a plurality of identities of other controllers, is able to route the connection to the user terminal by selecting one of the other controllers that is valid. The free beam path couples light beams from a second group of optical fibers to the first lens element such that the light beams are coupled to the first group of optical fibers in a first coupling arrangement. The first one-shot circuit is capable of providing a pulse. Such devices can display images to several people simultaneously in a manner that is more convenient than the use of miniature onboard displays.