| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of drastic brightness lowering even in the case the reproduced wavelength of a hologram is varied due to manufacturing variation and temperature fluctuation by making the angle of light made incident on a hologram nearly equal to the angle of light diffracted by the hologram and also specifying the distance between a virtual image and the hologram. SOLUTION: An information display source for emitting light 3 including information is constituted of a fluorescent display tube 21. The light 3 including the information is diffracted by a combiner 20 so as to be viewed as the displayed virtual image 10 by an observer 1. The combiner 20 is obtained by arranging the hologram on a base material such as a glass substrate and a transparent resin substrate, etc. The angleθ1 of light made incident on the combiner 20 from the fluorescent display tube 21 is nearly equal to the angleθd diffracted from the combiner 20 to the observer 1. And also, a distance (rd) from the combiner 20 to the displayed image 10 is less than three times a distance (r1) from the fluorescent display tube 21 to the combiner 20.
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