Optics: measuring and testing – For optical fiber or waveguide inspection
Patent
1990-05-25
1994-04-19
Evans, F. L.
Optics: measuring and testing
For optical fiber or waveguide inspection
356128, 356130, 356343, G01N 2141, G01N 2149
Patent
active
053050711
DESCRIPTION:
BRIEF SUMMARY
tted through the fluid strikes the rods at approximately the critical angle of the fluid. As the refractive index of the fluid changes, the amount of light reaching the detector will change, permitting thereby the deduction of said fluid refractive index change.
DISCLOSURE SUMMARY OF THE INVENTION
It is the major objective of my invention to monitor the refractive index of a fluid stationary within or flowing through a capillary channel surrounded by a transparent medium. This is accomplished by detecting the deviation of a fine beam of light after it has passed through the capillary, said displacement from the incident beam being due to the difference between the refractive index of the fluid and the transparent medium surrounding it. The transparent medium surrounding the capillary is of a refractive index higher than that of the fluid and the passage of the light beam is from said transparent medium into the capillary at angle obtuse to the capillary axis and then exiting the capillary back into said transparent medium. The deviation of the light beam from its straight line path is due to the differences of the corresponding refractive indices of the fluid and surrounding medium. The deviation will be greatest as the incident beam impinges on the capillary at an angle (measured with respect to the normal to the capillary axis) slightly less than the critical angle.
It is a further objective of my invention to provide a means for measuring the change of refractive index of a fluid at essentially the same physical position from which the fluid's light scattering properties are measured. This spatially coincident measurement is particularly important in the field of liquid chromatography, especially when applied to the technique of size exclusion or gel permeation chromatography.
Another objective of my invention is the deduction of the concentration of dissolved substances in the fluid, since a changing concentration of a dissolved solute will cause corresponding changes in the refractive index of the resulting solution. Such changes in concentration can be quantitated by converting said beam deviation into corresponding changes in concentration.
My invention will be particularly useful when applied to a light scattering cell similar to those described in the above referenced U.S. Pat. No. 4,616,927 of which I am a co-inventor. Said patent, hereinafter called the "927" patent, describes an important type of light scattering cell permitting measurement of the light scattering properties of solutions with minimal interference from light scattered at the cell interfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates Snell's Law for the refraction and reflection of a ray of light.
FIG. 2 shows the structure of a standard split prism cell used to measure the refractive index difference of two fluids.
FIG. 3 shows the refractions of a ray traversing a liquid capillary travel within a transparent medium.
FIG. 4 shows a detail of the refractions responsible for the beam deviations arising from positive and negative refractive index increments of the fluid within a capillary.
FIG. 5 shows a top view of the capillary-refracted rays' passage through the curved surface of a refraction cell described in "927" patent.
FIG. 6 shows the liquid capillary acting as a diverging cylindrical cell with respect to the incident light beam of finite cross section.
FIG. 7 shows a refraction cell of "927" patent.
FIG. 8 shows a spherical refraction cell permitting light beam incidence normal to curved surfaces outside of a plane containing a set of detectors for the measurement of scattered light for the same illuminated volume element.
FIG. 9 shows the results of an early experimental measurement confirming the sensitivity of the present invention.
MODES FOR CARRYING OUT THE INVENTION
FIG. 1 presents a diagram of the refraction and reflection of a light ray 1 in a transparent medium of refractive index n.sub.1, striking the plane interface 4--4 at an angle .theta..sub.1, and entering a medium of refractive index n.
REFERENCES:
patent: 3619068 (1971-11-01), Broerman
patent: 3636360 (1972-01-01), Oishi
patent: 4229105 (1980-10-01), Silverbage
patent: 4448691 (1984-05-01), Davis
patent: 4616927 (1986-10-01), Philips et al.
patent: 4660974 (1987-04-01), Machler et al.
patent: 4710643 (1987-12-01), Schukler et al.
patent: 4952055 (1990-08-01), Wyatt
Evans F. L.
Wyatt Philip J.
Wyatt Technology Corporation
LandOfFree
Differential refractometer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Differential refractometer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Differential refractometer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-24184