U.S. patent application number 11/091035 was filed with the patent office on 2005-08-04 for optical probe with sampling window cleaning configuration.
Invention is credited to Slater, Joseph B..
Application Number | 20050168736 11/091035 |
Document ID | / |
Family ID | 34315896 |
Filed Date | 2005-08-04 |
United States Patent
Application |
20050168736 |
Kind Code |
A1 |
Slater, Joseph B. |
August 4, 2005 |
Optical probe with sampling window cleaning configuration
Abstract
A self-cleaning optical probe includes a probe body having a
window with a surface oriented toward a sample under investigation.
A sampling beam carrying wavelengths representative of the sample
passes into the probe body through the window for analysis. A
conduit, preferably forming part of the probe body, is used to
carry a fluid to the surface of the window oriented toward the
sample, and a partition proximate to the window is used to direct
the fluid across the window as a laminar flow. The partition
further includes an aperture through which the sampling wavelengths
pass. This partition also permits a portion of the fluid to pass
though the aperture to ensure that the sample under investigation
does not reach the window. The fluid may be a liquid or gas, and is
preferably a solvent to maximize window cleaning. Although the
fluid may be discharged without entering into the environment being
sampled, the fluid may also be discharged into the sample,
depending upon the application, volume of the respective
fluid/sample flows, and other such factors.
Inventors: |
Slater, Joseph B.; (Dexter,
MI) |
Correspondence
Address: |
GIFFORD, KRASS, GROH, SPRINKLE & CITKOWSKI, P.C
PO BOX 7021
TROY
MI
48007-7021
US
|
Family ID: |
34315896 |
Appl. No.: |
11/091035 |
Filed: |
March 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11091035 |
Mar 28, 2005 |
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09441683 |
Nov 16, 1999 |
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6873409 |
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60108720 |
Nov 17, 1998 |
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Current U.S.
Class: |
356/301 ;
359/509 |
Current CPC
Class: |
G01J 3/02 20130101; G01N
2021/151 20130101; B08B 17/06 20130101; G01N 21/15 20130101; G01J
3/0256 20130101 |
Class at
Publication: |
356/301 ;
359/509 |
International
Class: |
G01J 003/44; G02B
001/00 |
Claims
I claim:
1-7. (canceled)
8. An optical probe, comprising: a probe body having a window with
a surface oriented toward a sample under investigation; an
excitation beam following an excitation optical path through the
probe body and the window to the sample under investigation; a
sampling beam carrying Raman or fluorescence wavelengths
representative of the sample into the probe body through the window
along a path generally counter-propagational to the excitation
optical path; and a structure operative to flood the window with
fluid to keep it clean.
9. The optical probe of claim 8, wherein the fluid is a
solvent.
10. The optical probe of claim 8, wherein the fluid is a
liquid.
11. The optical probe of claim 8, wherein the fluid is a gas.
12. The optical probe of claim 8, wherein the fluid enters into the
sample under investigation after flooding the window.
13. The optical probe of claim 8, further including an optic
operative to focus the excitation beam and collimate the sampling
beam.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. provisional
application Ser. No. 60/108,720, filed Nov. 17, 1998, the entire
contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates generally to optical probes and, in
particular, to a probe having a self-cleaning capability for use in
on-line process control and other applications.
BACKGROUND OF THE INVENTION
[0003] Optical probes such as those used for Raman detection are
increasingly being employed in on-line process-control
applications. In a typical configuration, this requires that at
least the sampling optic be immersed directly into a process
stream. In many cases, the process stream contains materials which
tend to coat the optic, thereby reducing or completely eliminating
the ability to collect data.
[0004] Many solutions have been tried to compensate for, or to
remove, such coatings, including ultrasonic cleaners, spray jets,
mechanical "windshield" wipers, and even arrangements which
automatically retract, clean and reinsert the probe. Each of these
approaches has distinct disadvantages. Ultrasonic cleaners have
difficulty maintaining sufficient energy density at the optic, and
do not operate well in viscous fluids. Spray jets are affected by
process flows, and require large volumes of solvent. Mechanical
approaches introduce unwanted sealing requirements into the
process, and may pose safety and/or reliability problems.
SUMMARY OF THE INVENTION
[0005] This invention resides in an optical probe with a
self-cleaning sampling window, a feature which is particularly
useful in on-line process-control environments. The concepts are
ideally suited to Raman and fluorescence detection, through the
apparatus and methods are not limited in this regard.
[0006] In terms of hardware, the apparatus includes a probe body
having a window with a surface oriented toward a sample under
investigation. A sampling beam carrying wavelengths representative
of the sample passes into the probe body through the window for
analysis. A conduit, preferably forming part of the probe body, is
used to carry a fluid to the surface of the window oriented toward
the sample, and a partition proximate to the window is used to
direct the fluid across the window as a laminar or turbulent
flow.
[0007] In a preferred configuration, the partition further includes
an aperture through which the sampling wavelengths pass. This
partition also permits a portion of the fluid to pass though the
aperture to ensure that the sample under investigation does not
reach the window. The fluid may be a liquid or gas, depending upon
the nature of the sample, and is preferably a solvent to maximize
window cleaning. Although the fluid may be discharged without
entering into the environment being sampled, the fluid may also be
discharged into the sample, depending upon the application, volume
of the respective fluid/sample flows, and other such factors.
BRIEF DESCRIPTION OF THE DRAWING
[0008] FIG. 1 is a drawing in cross-section illustrating a
preferred embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0009] Broadly, and in general terms, this invention utilizes a
flowing solvent as opposed to a jet-spray to keep clean a window
used in conjunction with a sampling beam of a spectroscopic system.
The approach is applicable to any form of optical sampling,
including Raman detection, fluorescence, and so forth. In the
preferred embodiment, the solvent used for cleaning is supplied as
a laminar sheet over and past the surface of the window exposed to
the process flow. Alternatively, other "fluids" may be used in lieu
of solvents, including gases, particularly if applied in sheet
form, depending upon the type of process flow involved.
[0010] The invention will be better understood with reference to
FIG. 1, which illustrates a preferred embodiment in cross-section
generally at 100. Within a probe body 102, there is housed an
optical channel 104 containing a sampling beam 106. A sampling lens
106 is used to focus the beam to a localized sampling zone 114
through a sampling port 116. In this example, it is assumed that
the beam 106 includes both excitation (i.e., laser) and collected
wavelengths in a counter-propagating beam, though the invention is
applicable to a collection-only path, assuming no requirement for
excitation, or excitation originating from a different
direction.
[0011] Also contained within the probe body 102 are one or more
delivery tubes 120, delivering the cleaning fluid into a gap 122 on
the process side of window 112. A partition 113 or other structure
is provided to flood a small portion of the window actually used by
the sampling beam, as shown, thereby protecting the window from
contamination. It is also assumed that the solvent is substantially
transparent to the wavelengths being collected through the window,
such that the solvent itself will not contaminate or appreciably
modify the sample spectra.
[0012] The solvent flow may be laminar or turbulent, and may be
aspirated through the sample port and entrained through an output
port 124 into the solvent flow. This ensures that a representative
sample is always available to the sampling zone. Since there is a
danger that materials within the process flow may clog the sample
port, a second sample delivery tube 121 is positioned "downstream"
of the window. Solvent introduced into the tube 121 would serve to
increase the back pressure and drive the solvent forceably out the
sample port, thereby cleaning the entire sampling area.
[0013] It will appreciated to those of skill that the system just
described may be operated continuously during data collection, or
only on occasion to clean the window in between data collection
events.
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