Smoke detector

A smoke detector, comprising:

• a housing defining a chamber receptive of ambient materials;
• first and second receivers disposed to receive light reflected from the chamber along first and second receiving axes, respectively;
• first and second emitters disposed to emit light of first and second wavelengths, respectively, into the chamber at first and second and third and four angles relative to each of the first and second receiving axes, respectively, and at a same 0° angle relative to a common plane;
• and
• a controller configured to determine whether a current condition of the chamber should trigger an alarm based on output signals generated by the first and second receivers resulting from light emitted into the chamber by the first and second emitters being reflected toward the first and second receivers by the ambient materials,
• wherein:
• the first and second angles are measured in opposite directions from a same emission axis along which the first emitter emits the light of the first wavelengths and the first angle is greater than the second angle in absolute magnitude,
• the third and fourth angles are measured in opposite directions from a same emission axis along which the second emitter emits the light of the second wavelengths and the third angle is greater than the fourth angle in absolute magnitude,
• the first and third angles are obtuse,
• the second and fourth angles are acute, and
• the light of the first and second wavelengths comprises long and short wavelength light, respectively.

A method of operating a smoke detector comprising a housing defining a chamber, one or more receivers disposed to receive light reflected from the chamber along one or more receiving axes, respectively, and multiple emitters disposed to emit light of multiple wavelengths, respectively, into the chamber at multiple angles relative to each of the one or more receiving axes, respectively, the method comprising:

• receiving, from the one or more receivers, output signals resulting from light emitted into the chamber by the multiple emitters being reflected toward the one or more receivers by ambient materials in the chamber;
• and
• determining whether a current condition of the chamber should trigger an alarm based on output signal ratios calculated from the output signals and output signal durations, wherein the determining comprises:
• activating one of the one or more receivers;
• causing a first one of the multiple emitters to emit light into the chamber for reception by the one of the one or more receivers whereupon the one of the one or more receivers generates a first output signal;
• receiving and filtering the first output signal from the one of the one or more receivers and determining whether the received and filtered first output signal is above a trigger level;
• causing second and third ones of the multiple emitters to emit light into the chamber for reception by the one of the one or more receivers whereupon the one of the one or more receivers generates second and third output signals, respectively;
• calculating first, second and third output signal ratios based on the first, second and third output signals, and
• determining whether the current condition should trigger the alarm based on respective durations of the first, second and third output signal ratios.