Optics: measuring and testing – By dispersed light spectroscopy – With sample excitation
Patent
1991-12-31
1993-06-22
Evans, F. L.
Optics: measuring and testing
By dispersed light spectroscopy
With sample excitation
2504581, 356417, G01J 3443, G01N 2164
Patent
active
052219585
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a reflection fluorometer having a cylindrical measuring fiber-optical waveguide.
When a light wave impinges on the interface of two media with different refractive indices at a certain angle, it can be totally reflected if the angle of incidence .THETA. is larger than the critical angle .THETA..sub.c. This angle is calculated from the equation n2<n1. At the site of the reflection, a wave is generated in the optically thinner medium which builds up an energy field close to the interface. The use of this energy field (evanescent wave) for optical analyses has been known for a long time: the absorption effects in the case of total reflection on the interface of two optical media are even the classical method for the proof of these energy fields (C. Schaefer, Zeitschrift fur Physik (Journal for Physics), 75 [1932] 687-694).
The use of this energy field for analytical measurements has several advantages in comparison to conventional excitation. A stronger energy coupling may occur within the thin film which, as a rule, leads to a reduction of the background signal and therefore to a better signal
oise ratio.
STATE OF THE ART
Devices for measuring fluorescence, which is excited by total reflection, use fibers, cells or capillaries (EP-A 0202021, EP-A 0205236, EP-A 0245206, EP-A 0209489, EP-A 0239382, EP-A 0075353, DE-A 3605518, U.S.-A Pat. No. 4654532 and U.S.-A Pat. No. 4716121). In the DE-A 3605518, a tube-shaped measuring an optical waveguide for a fluorometer is described. The ends of the measuring fiber-optical waveguide are constructed as spherical or conical windows for the enlargement of the entrance cross-section for the exciting light. For the observation of fluorescence radiation, it is provided that the light is examined which emerges essentially perpendicularly to the axis of the measuring fiber-optical waveguide. For this purpose, for example, the axis of the measuring fiber-optical waveguide is imaged on the entrance slit of the fluorescence spectrometer.
From E. Reichstein, et al., Anal. Chem. 60 [1988] 1069-1074, it is known to measure the fluorescence, excited by pulsed laser light, of the fluorescence-marked antibodies fixed in the recesses of a microtitration plate in a time window which is adapted to the relatively long die-away time of the fluorescence of the marker and the rapidly dying-away background fluorescence of the test solution.
DESCRIPTION OF THE INVENTION
It is the task of the present invention to improve the reflection fluorometers having a cylindrical measuring fiber-optical waveguide according to the state of the art with respect to the sensitivity, the signal
oise ratio, the required test volume and the obtainable quantity and quality of information. According to the invention, this task is achieved by the objects defined in the patent claims.
The object of the invention is a reflection fluorometer having a cylindrical measuring fiber-optical waveguide characterized by a capillary-shaped measuring fiber-optical waveguide, a conical-envelope-shaped beaming of pulsed light onto a front face of the measuring fiber-optical waveguide, and a device for the time-resolved measurement of the emission light which emerges essentially radially from the measuring fiber-optical waveguide.
A preferred reflection fluorometer is distinguished by a device for wavelength-resolved measurements.
Furthermore, a reflection fluorometer is preferred in which the measuring fiber-optical waveguide has a mirror on the end which is opposite the beaming-in of the light.
A particularly preferred reflection fluorometer has an auxiliary sensor for the measuring of a part of the reflected light and/or of the emission light for the compensation and correction of the measured values.
Another embodiment is distinguished by the fact that the measuring fiber-optical waveguide is situated on a focal line of a reflector which has an elliptic and/or paraboloidal cross-section. The reflector is preferably followed by a focus adapter.
For introducing the ligh
REFERENCES:
patent: 4708941 (1987-11-01), Giuliani
patent: 4867559 (1989-09-01), Bach
patent: 4880752 (1989-11-01), Keck et al.
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