| 摘要 |
PURPOSE:To control a photodetection signal level according to a light emission signal level by providing a pin member which moves freely to and away from the intersection of the optical axis of a light emitting element and the optical axis of a light receiving element. CONSTITUTION:A smoke sensor 1 is constituted by arranging a light-source side optical system 18 which has the light emitting element 7 at the bottom part of a 1st long hole 5 and a light-reception side optical system 19 which has the light receiving element 8 at the bottom part of a 2nd long hole 6 so that the optical axis of the light emitting element 7 and the optical axis of the light receiving element 8 cross each other outside the 1st and 2nd long holes 5 and 6. further, the pin member 20 is provided to a smoke sensor main body 2 so that it moves freely to and away from the intersection of both optical paths. The quantity of light emission is varied by diffraction or reflection by this pin member 20 to vary the quantity of light reception. Consequently, the light emission signal level of the light emitting element 7 is controlled to control the light reception level of the light receiving element 8.
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