Mask to mark maps - has light projection of rays on to screen via perforated or transparent grille

摘要

The mask is for selective marking of maps and documents. It uses the projection of light rays on to a translucent screen. This is controlled by each ray passing through a fixture which can be moved. The relative position of screen and fixture determines which rays can pass. The fixture is a series of opaque grilles with transparent or perforated markings above the lamps. It has suspended, movable sheets with surfaces with the markings (transparent or perforated). The control consists of sliding scales on the frame of the equipment.