Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1993-06-02
1995-08-15
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25022718, H01J 516
Patent
active
054421691
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for determining the value of one or more variables to be measured.
BACKGROUND OF THE INVENTION
An optical sensor for the selective detection of substances and for detecting changes in the refractive index in measurement substances is known from International Patent Application WO 86/07,149. Very high measuring sensitivities can be attained with such an arrangement.
German Patent 3,723,159 discloses a chemical sensor that by means of a selective matrix on a waveguide film induces interactions between the selective matrix and the medium containing the substance and brings about measurable physical changes.
International Patent Application WO 89/07756 discloses an integrated optical interference method for the selective detection of substances and liquid and gaseous samples that achieves high sensitivity with a single film- or strip-type waveguide.
It is a failing of these various arrangements that the waveguide, at best provided with a grating and a sensor layer, is used only as a single component; in other words, the functional sensor comprises a combination of components of the integrated optics (such as waveguides) and discrete optics (such as lasers, lenses, photodetectors, mechanical parts and measuring means). The attendant disadvantages are that it is difficult to adjust, is insufficiently stable, and is highly susceptible to external parasitic induction. Moreover, for many applications, the sensor arrangements take up too much space. Complete systems constructed in this way are also very expensive.
OBJECT AND SUMMARY OF THE INVENTION
An object of the invention is to provide a method and an apparatus for achieving genuinely integrated optical sensor modules in which the aforementioned deficiencies are eliminated.
Exemplary embodiments of the invention are described in detail below, in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of a sensor module;
FIG. 2 is a more-detailed schematic illustration of a sensor module;
FIG. 3a shows a sensor module with a uniform Bragg grating on a planar waveguide with a thickness gradient, in a plan view;
FIG. 3b is a section along the line A-A' of FIG. 3a;
FIG. 3c is a section along the line B-B' of FIG. 3a;
FIG. 4a shows a sensor module with a uniform Bragg grating on a planar waveguide with a refractive index gradient, in a plan view;
FIG. 4b is a section along the line A-A' of FIG. 4a;
FIG. 4c is a section along the line B-B' of FIG. 4a;
FIG. 5a shows a sensor module with a Bragg grating, with a space frequency varying transversely to the beam 5, on a uniform planar waveguide in a transmission arrangement, in a plan view;
FIG. 5b is a section along the line A-A' of FIG. 5a;
FIG. 5c is a section along the line B-B' of FIG. 5a;
FIG. 6a shows a sensor module with a Bragg grating, with a space frequency varying longitudinally to the beam 5, on a uniform planar waveguide in a reflection and transmission arrangement, in a plan view;
FIG. 6b shows a sensor module with a Bragg grating, with a space frequency varying longitudinally to the beam 5, on a uniform planar waveguide in a reflection arrangement, in a plan view;
FIG. 7a shows a sensor module with a Bragg grating, with a space frequency varying longitudinally to the beam 5, on a strip waveguide in a reflection arrangement, in a plan view;
FIG. 7b shows a sensor module with a Bragg grating, with a space frequency varying longitudinally to the beam 5, on a strip waveguide, and with a strip waveguide array;
FIG. 8a shows a sensor module with a nonuniform Bragg grating and an angle-dependent resonance condition in a transmission arrangement;
FIG. 8b shows a sensor module with a uniform Bragg grating and an angle-dependent resonance condition in a transmission arrangement;
FIG. 8c shows a sensor module with a uniform Bragg grating and an angle-dependent resonance condition in a reflection arrangement;
FIG. 9a shows a sensor module with a novel integrated optical filter, tunable
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R. E. Kunz, "Gradient Effective Index Waveguide Sensors", Paul Scherrer Institute Zurich, Switzerland, paper submitted to Sensors & Actuators, part B (Elsevier, 1992), Abstract, pp. 1-15, 1 p. references, 1 p. Figure captions, 6 p. drawings.
R. E. Kunz, "Gradient Effective Index Waveguide Sensors" Sensors and Actuators B, 11 (1993) pp. 167-176.
R. E. Kunz, "Totally Integrated Optical Measuring Sensors" Chemical, Biochemical, and Environmental Fiber sensors III, SPIE vol. 1587 (1991), pp. 98-113.
Nelms David C.
Paul Scherrer Institut
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