| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To obtain a projected beam type smoke detector capable of specifying occurrence of optical axis shift when the optical axis shift occurs. <P>SOLUTION: A projected beam type smoke detector comprises: a light-emitting element that consists of one main light-emitting element (11), and two or more slave light-emitting elements (12) arranged around the main light-emitting element; a light-receiving element (21) for receiving a light beam emitted from the light-emitting element; and controllers (15 and 23) for monitoring the presence or absence of smoke emission based on a change in an amount of light received by the light-receiving element. The controllers turn on the main light-emitting element when monitoring the presence or absence of smoke emission. And when a light extinction rate of the amount of light received from the main light-emitting element becomes equal to or greater than an acceptable light extinction rate, the controllers sequentially turn on the two or more slave light-emitting elements after turning off the main light-emitting element, obtain the light extinction rate of the amount of light received from each of all slave light-emitting elements, and determine whether a decrease in the amount of light received from the main light-emitting element is caused by the smoke emission or by an optical axis shift, based on the light extinction rate obtained for each. <P>COPYRIGHT: (C)2012,JPO&INPIT</p> |
