Looped fiber-optic sensor for the detection of substances
First Claim
1. A sensor for detecting the presence or absence of a particular substance, comprising:
- a light source;
a photodetector;
a fiber optic guide with a diameter D at some point along its length, an input portion and an output portion, the fiber optic guide characterized by a shortest distance ED between the input and output portions measured in a plane, the input portion coupled to the light source, the output portion coupled to the photodetector, the fiber optic guide between the two portions forming a loop characterized by having at least two tangent lines along the loop and between the input and output portions such that there exists a distance TD, which is the shortest distance between the tangent lines that can be measured by a straight line segment perpendicular to each of the tangent lines, that exceeds ED, TD being measured in the same plane as ED;
wherein the maximum value of TD (W) divided by D is less than 30;
whereby light propagates from the light source to the detector through the loop.
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Accused Products
Abstract
The present invention provides methods and apparatus for inexpensively and accurately sensing with the use of a fiber optic guide the presence or absence of a particular substance ("analyte"). The preferred embodiment of the sensor of the present invention comprises a light source, a photodetector, and a loop shaped plastic fiber that is exposed to the environment and that acts as a sensing element. In the preferred embodiment, the loop comprises a partial ellipse and the angles at which the light enters and exits a sensing zone is defined by the tangents to the elliptical arc. In the preferred embodiment, the fiber optic guide comprises a core and a cladding, either of which are coated with a coating that is selected to decompose in the presence of the analyte. The coating is selected to have an index of refraction just above or greater than the core, causing an increase in the amount of light that is detected when the analyte is present.
52 Citations
33 Claims
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1. A sensor for detecting the presence or absence of a particular substance, comprising:
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a light source; a photodetector; a fiber optic guide with a diameter D at some point along its length, an input portion and an output portion, the fiber optic guide characterized by a shortest distance ED between the input and output portions measured in a plane, the input portion coupled to the light source, the output portion coupled to the photodetector, the fiber optic guide between the two portions forming a loop characterized by having at least two tangent lines along the loop and between the input and output portions such that there exists a distance TD, which is the shortest distance between the tangent lines that can be measured by a straight line segment perpendicular to each of the tangent lines, that exceeds ED, TD being measured in the same plane as ED; wherein the maximum value of TD (W) divided by D is less than 30; whereby light propagates from the light source to the detector through the loop. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A sensor for detecting the presence or absence of a particular substance, comprising:
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a light source; a photodetector; a fiber optic guide with two ends and having a diameter D, one end coupled to the light source, the other end coupled to the photodetector, the fiber optic guide between the two ends forming a loop characterized by having at least at one segment along its length with a minimum radius of curvature less than 8 times D;
whereinthe loop comprises an input portion and an output portion and the loop is characterized by a shortest distance ED between the input and output portions measured in a plane, the loop further characterized by having at least two tangent lines along the loop and between the input and output portions such that there exists a distance TD, which is the shortest distance between the tangent lines that can be measured by a line segment perpendicular to each of the tangent lines, that exceeds ED, TD being measured in the same plane as ED. - View Dependent Claims (20, 21, 22)
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23. A sensor for detecting the presence or absence of a particular substance, comprising:
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a light source; a photodetector; a fiber optic guide with an input portion and an output portion characterized by a shortest distance ED between the input and output portions measured in a plane by a first line segment, the input portion coupled to the light source, the output portion coupled to the photodetector, the fiber optic guide between the two portions forming a loop such that a shortest distance TD between a first point and a second point along the loop, as measured in the plane by a second line segment that is parallel to the first line segment, exceeds ED; and
whereinthe shortest distance between the first point and the output portion measured in the plane is greater than the shortest distance between the first point and the input portion measured in the plane; the shortest distance between the second point and the input portion measured in the plane is greater than the shortest distance between the second point and the output portion measured in the plane; and the maximum value of TD is less than one meter. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification