Solid state sunlight readable illuminated display device

Abstract

A solid state sunlight readable, night vision compatible display device in which a legend, of which at least a portion is translucent, is back lit by a fluorescent coating on an electroluminescent light source. Under high ambient light conditions the fluorescent coating is energized primarily by ambient light transmitted through the legend. Under low ambient light conditions the fluorescent coating is energized primarily by light from the electroluminescent light source. A solid state shutter whose operation is coordinated with that of the light source is provided in front of the legent to prevent undesired message displays when the display device is "off".

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows: 
     
       1. A display device for displaying a message readable under both high and low ambient light conditions, comprising: a message carrying member of which is at least a portion is translucent, said message carrying member having a first side from which the message is to be read and a second side opposite the first side;   an artificial light source located on the second side of said message carrying member; and   a fluorescent film positioned on the second side of said message carrying member, said fluorescent film being positioned to receive both ambient light through the translucent portion of said message carrying member and light from said artificial light source, said fluorescent film being operable to emit light and illuminate said message carrying member when receiving the ambient light or light from said artificial light source.   
     
     
       2. The display device of claim 1 wherein said artificial light source is an electroluminescent panel. 
     
     
       3. The display device of claim 2 wherein said fluorescent film is carried on a surface of said electroluminescent panel facing said message carrying member. 
     
     
       4. The display device of claim 3 wherein: said artificial light source is selectably energizable;   a shutter is provided on the first side of said message carrying member; and   control means connected to said artificial light source and said shutter is provided for coordinately energizing said artificial light source and opening said shutter.   
     
     
       5. The display device of claim 4 wherein said shutter comprises a twisted nematic liquid crystal solid state shutter with crossed polarizers. 
     
     
       6. The display device of claim 5 wherein said message carrying member is a film strip. 
     
     
       7. The display device of claim 6 further including a lens with an antireflective coating positioned on the side of said shutter opposite said message carrying member. 
     
     
       8. The display device of claim 7 wherein said control means is energized by an electrical switch actuatable by operator contact with said lens. 
     
     
       9. The display device of claim 8 wherein said electrical switch is a solid state Hall effect switch. 
     
     
       10. A method of producing a visual message readable under both low and high ambient light conditions, comprising the steps of: providing a message carrying member of which at least a portion is translucent, said message carrying member having a first side from which the message is to be read and a second side opposite the first side;   providing an artificial light source on the second side of said message carrying member; and providing a fluorescent film on the second side of said message carrying member, said fluorescent film being operable to emit light in response to either ambient light or light received from the artificial light source, whereby under high ambient light conditions the message carrying member is illuminated by said fluorescent film primarily in response to ambient light received through the translucent portion of said message carrying member, and under low ambient light conditions the message carrying member is illuminated by said fluorescent film primarily in response to light received from the artificial light source.   
     
     
       11. The method of claim 10 comprising the further steps of: positioning a shutter on the first side of the message carrying member; and coordinately controlling the artificial light source and the shutter so that the shutter is open when the artificial light source is energized and the shutter is closed when the artificial light source is not energized.