| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for installing a shutter that can secure the display function of a traffic signal even in its failure mode to prevent a case where the signal is mistaken to be lighted due to a reflector contained in the signal even when the light source of the signal is not actually lit in the case the sunlight is made incident on the signal in its front. SOLUTION: A straight line that is orthogonal to an optical axis is used as a border line and the front of a reflector 2 of a traffic signal is divided into two parts. A shutter 11 is prepared only at one of both front parts of the reflector 2 with no shutter prepared at the other front part of the reflector 2. As a result, the sunlight never reaches the reflector 2 at the part covered with the shutter 11. Meanwhile, the sunlight made incident on the other part having no shutter is reflected twice at the inside of the reflector 2, cut off by the shutter 11 and never leaks to the outside even though the sunlight is changed toward the outside. Even in a failure mode of the traffic signal, the light of a light source 1 goes to the outside through the part having no shutter and thereby the display function of the signal is secured although its illuminance is lowered a little in its lighting mode.
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