APPARATUS AND METHOD FOR REMOTE SENSING OF GASES, VAPOURS OR AEROSOLS

摘要

A remote sensor for detecting gas, vapor or aerosol comprises means to measure the change in temporal coherence of light of a selected narrow waveband when it interacts with the gas etc. The light can be provided by a laser source or spectrally filtered sun light etc. Received radiation is split in to two beams by a Fresnel biprism and then detected by a detector sensitized by a modulating reticle to interference fringes. A glass delay plate of suitable thickness is placed in the path of one of the beams such that only received radiation having a temporal coherence greater than a minimum determined by the plate thickness produces an output signal from detector. The minimum temporal coherence is set higher than the temporal coherence of the illuminating radiation. In alternative arrangements a band-pass temporal coherence filter may be used and the sensor can be made to spectrally scan the field of view by using a tunable laser or a variable center frequency band-pass optical filter.