| 摘要 |
PROBLEM TO BE SOLVED: To provide a panel-like illumination device having an independent power source. SOLUTION: Light emitting diodes 13 are arranged on the end surface of a light transmission plate 11 consisting of a transparent plate formed by dotting recessed shapes 12 on the surface thereof on an observer side. The power source is constituted of a solar battery 14 and a secondary battery 15. Then, a photovoltaic current generated by the solar battery 14 is detected by a photovoltaic current detection circuit 18. Based on the magnitude of the photovolataic current, the brightness of a periphery is judged by a brightness discrimination circuit 19. When the periphery is dark, a turning-on circuit 16 is turned on so as to turn on the diodes 13. Light made incident from the end surface of the plate 11 is totally reflected by the recessed shapes 12 and transmitted through the plate 11 downward so as to illuminate a liquid crystal display device 21 being an object to be illuminated. |
