Device for sensing the presence of a flame in a region

Claim 1

An arrangement for sensing for the presence of a flame in a region of an engine comprising: an optical focusing device for concentrating electromagnetic radiation emanating from the region of an engine; means for effecting a frequency selective separation of electromagnetic radiation into at least a lower frequency component and a higher frequency component, the means for effecting a frequency selective separation comprising first and second optical filters having non-overlapping passbands; an optical pathway for receiving the concentrated electromagnetic radiation from the optical focusing device and conveying that radiation to the means for effecting a frequency selective separation, the optical pathway including a bifurcation defining two branches with one optical filter located in one branch between the bifurcation and a first means and the other optical filter located in the other branch between the bifurcation and a second means; said first means responsive to the means for effecting a frequency selective separation for providing a first electrical signal indicative of the magnitude of the lower frequency component; said second means responsive to the means for effecting a frequency selective separation for providing a second electrical signal indicative of the magnitude of the higher frequency component; and means responsive to the first and second electrical signals for providing a first indication if the first and second electrical signals are within predetermined limits indicative of the presence of a flame, and a second no flame indication otherwise.