| 摘要 |
PROBLEM TO BE SOLVED: To achieve a longer service life of a light-emitting element by minimizing a rise in temperature within a box part attributed to sun light and a higher measurement accuracy, by making the box part and a mounting member lighter in weight and compact. SOLUTION: In the light projector/receiver 14, a box part is divided vertically in two, to make the upper part as an upper lid part, while the lower part is made as body part 34 containing a light-projecting part and a light-receiving part. A rubber sheet 32 is arranged between both the parts as heat insulating member to cut the conduction of heat. When sunlight 12 radiates directly on the upper lid part 30, it rises to a high temperature, but rubber sheet 32 blocks the conduction of the heat to keep the side of the body part 34 from being heated. A radiation fin 36 is formed on the outer surface of the body part 34 of the light projector/receiver 14 to, radiate heat efficiently outside from the box part 34 in the body part 34, thereby achieving a linger service life of the light-emitting element.
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