| abstract |
The beam detector 10 includes a light source 32, a receiver 34, and a target 36 that cooperatively operate to detect particles in the monitored area 38. The target 36 reflects the incident light 40 and causes the reflected light 32 to return to the receiver 34. The receiver 34 may record and report the light intensity at multiple points across the view field. In a preferred form, the detector 10 emits a first light beam 3614 in the first wavelength band, a second light beam 3618 in the second wavelength band, and a first light beam 3616 in the third wavelength band, 1 and the second wavelength band are substantially the same and different from the third wavelength band. |