| 摘要 |
PROBLEM TO BE SOLVED: To improve an S/N ratio by reducing an amount of stray light for reflecting a shading wall, or the like. SOLUTION: A photoelectric smoke sensor includes a light-emitting element 22 for emitting light to an inside of a smoke detecting part 1; and a light-receiving element 23 for receiving light emitted from the light-emitting element 22 and scattered by smoke particles of the smoke detecting part 1; and an aperture 30, near a light-emitting part of the light-emitting element 22, having a longitudinal slit 30a being smaller in width than an external diameter of the light-emitting part of the light-emitting element 22 and limiting an irradiating light amount to the side. The amount of stray light for reflecting a shading wall or the like is reduced by eliminating irradiating light to the left and right directions of the light-emitting element 22 by the longitudinal slit 30a. COPYRIGHT: (C)2011,JPO&INPIT
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