Patent ID: 8586930

Claim:
A non-dispersive single beam detection assembly in an infrared gas analyzer, the assembly comprising: one wide-band radiation source providing infrared radiation as a beam; a measuring chamber for a gas mixture with a gas component to be measured; a physical beam splitter for dividing said radiation beam transmitted through the measuring chamber into a reflected beam portion and a transmitted beam portion; a measuring detector positioned to receive the reflected beam portion, and a reference detector positioned to receive the transmitted beam portion; wherein the detection assembly comprises: a pair of dielectric optical pass-band filters having the same peak wavelength and the same half-bandwidth when perpendicular to the radiation direction, one of the dielectric optical filters positioned to be the physical beam splitter dividing the infrared radiation as a beam, and another of the dielectric optical filters positioned to be an analyzing filter between the physical beam splitter and the measurement detector, wherein said transmitted beam portion has a first spectral intensity peak at shorter wavelengths with a first peak wavelength and a first half-bandwidth, and said reflected beam portion after the analyzing filter has a second spectral intensity peak at longer wavelengths with a second peak wavelength and a second half-bandwidth; and there is a wavelength gap between said second peak wavelength and said first peak wavelength, which wavelength gap corresponds to one wide-band to a wavelength shift of an optical interference filter with said second peak wavelength as tilted from its perpendicular position to an angled position between 30° and 60° in respect to radiation direction; and said wavelength gap is at maximum 10% of the second peak wavelength, and at minimum 0.5% of the second peak wavelength.