Patent ID: 8289178

Claim:
An optical unit for a smoke analyzer system which comprises: an optical emitter (E) for alternately directing a beam of horizontally polarized light (Î» H ), and a beam of vertically polarized light (Î» V ) along a beam path through a smoke cloud; a horizontally polarized detector (D H ) positioned at a scattering angle (Î¸) from the beam path for generating a signal S HH in response to Î» H , and for generating a signal S VH in response to Î» V ; a vertically polarized detector (D V ) positioned at the scattering angle (Î¸) opposite the beam path from D H for generating a signal S HV in response to Î» H , and for generating a signal S VV in response to Î» V ; an oscillator connected to the emitter to establish a blink rate for transmissions of Î» H and Î» V from the emitter; a pre-filter connected to the detector D V and to the detector D H to filter noise from outputs of the respective detectors D V and D H , wherein the pre-filter filters a substantially d.c. component (white noise) from the outputs of the respective detectors D V and D H ; a synchronous demodulator connected in series with the pre-filter and connected directly to the oscillator for tracking the blink rate of the emitter during generation of the signals S HH , S HV , S VH , and S VV ; and a computer for evaluating the signals S HH , S HV , S VH , and S VV for analysis of the smoke.