by lowering his eyes the screens 13 14 are positioned in relation to the mirrors 15 16 so that when the user looks straight ahead the upper boundary 17 of this vertical field is practically tangential to the lower edges of these screens and to the upper edges of the mirrors 15 16 see fig3 the devices 6 7 are devices of a type known per se with lenses enabling the projection on the mirrors 11 12 of the images conveyed by the fibers 3 4 when as shown in the drawings the devices 8 and 9 are two channel devices the fibers 3 and 4 are doubled as are the devices 6 and 7 and the mirrors 11 12 the images formed by the devices 6 7 on the mirrors 11 12 are sent on by these mirrors 11 12 to the screens 13 14 thus in looking at the mirrors 15 16 the user 5 may see the images formed on the screens 13 14 naturally the image generator and the projectors are made so as to provide for the perfect superimposition of the images seen by the right eye and the left eye in the zone where the visual fields of these two eyes overlap the mirrors 15 and 16 are semi reflective to enable the user to see the instruments of the instrument panel 18 through them the device 10 in sensing the motions of the user 39 s head sends information to the image generator 1 this information can be used in a manner known per se to.