1. Field of the Invention
The invention is directed to both a system and a technique for remote chemical analysis. More particularly, the invention provides for the use of a solid-state acousto-optic device in combination with fiber optic technology in order to provide a system for the remote chemical analysis of a species of interest.
2. Description of the Prior Art
It is the conventional practice in the petrochemical industry, to utilize "in-line" sensors to affect chemical analysis. However, in such configurations, the presence of electrical or chemical sensors poses a significant threat to the safety of the area, from either explosions or from chemical contamination. As a result, such "in-line" sensors must be contained in approved explosion-proof enclosures. These enclosures represent an obvious significant cost to the petrochemical industry.
It has been suggested by G. Schmidtke, et al. VDI-Berichte 509,293 (1984) that a fiber optic system can be utilized to provide remote chemical analysis. This prior art system utilizes a diffraction grating and an array of detectors in a location remote from a sampling area.
Acousto-optic tunable filters (AOTF) have previously been used in spectral analysis as an effective device to measure dilute gas mixtures. An example of an automated AOTF infrared analyzer system which is unsable in a variety of industrial and commercial control applications is disclosed in U.S. Pat. No. 4,490,845 to Steinbruegge et al., which patent is assigned to the assignee of the present invention and incorporated herein by reference as if fully set forth.
Concentrated mixtures of gases and especially liquids often have strong, nearly total absorption bands. To analyze these mixtures, one must utilize the weaker overtone absorptions. These overtone bands lie in the near-to-intermediate infrared, where quartz fiber optic attenuation is not prohibitive to the use of such fibers. Using optical fibers eliminates one of the constraints with present detection systems.
It is an object of the present invention to provide a remote system for chemical analysis which utilizes optical fibers to convey an infrared source to a sample and then from the sample toward a detector array. This configuration would allow the use of such a remote chemical analysis system in applications where the presence of electrical or chemical sensors pose a significant threat from, for example, either explosions or from chemical contamination.
It is yet another object of this invention to provide an improved remote chemical analyzer which incorporates an automated acousto-optic infrared analyzer system remotely disposed from the sample site.