Optical measurement probe with leak minimization features...

Details Optical measurement probe with leak minimization features... Optical measurement probe with leak minimization features...

2001-05-31

2003-08-05

Robinson, Mark A. (Department: 2872)

Optics: measuring and testing

By dispersed light spectroscopy

With raman type light scattering

C356S432000, C250S461200

Reexamination Certificate

active

06603545

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to optical measurement probes and, in particular, to a probe having leak-minimization features suited to on-line process control and other applications.
BACKGROUND OF THE INVENTION
Induced radiative effects such as Raman scattering and fluorescence have become extremely valuable tools associated with the non-destructive determination of molecular constituents. Optical probes for such purposes are being employed in on-line process control in increasing numbers. These probes are often installed directly into the process stream or reactor, thus posing a potential safety hazard.
Probes which are based on free-space optics are of particular concern. As seen in
FIG. 1
, the probe body
102
extends through the wall of process containment vessel
104
. An optical beam
110
follows a direct path through a transparent medium such as window
112
to the sampling optics
114
immersed in the process. A failure of the window
112
at the immersed probe end allows a direct leak path to the outside.
The need remains, therefore, for an optical measurement probe with leak minimization and/or sampling suitable to process monitoring and other applications.
SUMMARY OF THE INVENTION
This invention resides in optical probe configurations particularly suited to the monitoring of a process flow through the wall of a containment vessel. All embodiments include a probe body which extends through, and is sealed to, the wall of the containment vessel. The probe body has an inner wall terminating in a distal end with a window, enabling light from the process flow to pass therethrough and into the probe body.
Although the probe body is presumed to carry light in both directions for excitation and collection, invention is not limited in this regard or the way in which light is carried to, or from, the body itself. That is, a probe according to the invention may be used only for excitation or collection, and optical fibers may, or may not, be used between the body and a source or radiation and/or analysis means.
In the preferred embodiment, the elements disposed within the probe body used to minimize and/or detect leaks of the process flow include one or more lenses operative to focus the light into a focal point, and a restriction of the inner wall of the probe body creating a narrow aperture at the focal point. In an alternative embodiment, a plug transparent to the light of interest is sealed to the inner wall of the probe body. As a further alternative, the elements include a second window creating a cavity with the distal window, and a port into the cavity accessible from outside the window for sampling purposes.
Although these embodiments are referred to as ‘alternative,’ they may be used in combination as well as separately. Indeed, all three embodiments may be used simultaneously for increased integrity.


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