| 摘要 |
A smoke detector is disclosed in which smoke particles are detected by the collection and detection of blue light and infra-red radiation which are emitted into a predetermined path through a scattering volume where the particles may be present. The scattered blue light and the scattered infra-red radiation are collected by an ellipsoidal mirror and focussed onto a suitable detector and then compared to produce an output which indicates either that the detected particles are smoke particles or that they are not smoke particles. The radiation collected by the mirror has been scattered through angles substantially less than 45° and preferably between about 10° and 35°. |
