Refractive Index Matching in Capillary Illumination
System and method for fluorescent light excitation and detection from samples to enhance the numerical aperture and/or reduce the cross-talk of the fluorescent light.
1 . An excitation system for analyzing samples comprising:
a light source;
a housing, wherein the housing transports samples and propagates light from the light source by total internal reflection;
a coupling optical element configured to introduce light from the light source into the housing through a wall of the housing; and
an index matching compound disposed in such a manner so as to optically couple the housing and the coupling optical element.
2 . The system of claim 1 , wherein at least a portion of the index matching compound is disposed in a region between the housing and the coupling optical element.
3 . The system of claim 1 , wherein the composition of the index matching compound is selected from the group consisting of: a solid material, a semisolid material, a liquid material, a viscous material, and a gel material.
4 . The system of claim 1 , wherein the housing, the coupling optical element and the index matching compound have respective refractive indices and the refractive index of the index matching compound is configured to provide a selected degree of coupling efficiency between the housing and the coupling optical element.
5 . The system of claim 4 , wherein the refractive index of the index matching compound is similar to the refractive index for the housing.
6 . The system of claim 4 , wherein the refractive index of the index matching compound is similar to the refractive index for the coupling optical element.
7 . The system of claim 4 , wherein the refractive index of the index matching compound is less than refractive index than the coupling optical element.
8 . The system of claim 7 , wherein the refractive index of the index matching compound is in the range from approximately 1.4 to approximately the refractive index of the coupling optical element.
9 . The system of claim 1 , wherein an index of refraction of the coupling optical element is greater than an index of refraction of the housing.
10 . The system of claim 1 , wherein an index of refraction of a material comprising the housing is greater than an index of refraction of a fluid sample transported within the housing.
11 . The system of claim 1 , wherein the light source is selected from the group consisting of: a coherent light source, a non-coherent light source, and a combination coherent/non-coherent light source.
12 . The system of claim 1 , wherein the housing comprises a plurality of capillaries.
13 . The system of claim 1 , wherein the coupling optical element has a shape selected from the group consisting of: a truncated sphere, a hemisphere, a cone, a hyperhemisphere, a spherical surface combined with a cylindrical surface, a spherical surface combined with a planar surface, and a meniscus lens.
14 . The system of claim 13 , wherein the truncated sphere further comprises;
a coupling section joined to a portion of the housing;
a lens section joined to a first portion of the coupling section; and
a second lens section joined to a second portion of the coupling section.
15 . The system of claim 1 , wherein the coupling optical element is constructed to permit light to enter the housing and propagate by total internal reflection.
16 . A method for exciting fluorescence of samples comprising:
transporting a plurality of samples through a detection zone with a capillary;
directing a non-coherent light into the capillary with a coupling optical element and an index matching compound that optically couples the coupling optical element and the capillary.
17 . The method of claim 16 , wherein at least a portion of the index matching compound is disposed in a region between the capillary and the coupling optical element.
18 . The method of claim 16 , wherein the composition of the index matching compound is selected from the group consisting of: a solid material, a semisolid material, a liquid material, a viscous material, and a gel material.
19 . The method of claim 16 , wherein the capillary, the coupling optical element and the index matching compound have respective refractive indices and the refractive index of the index matching compound is configured to provide a selected degree of coupling efficiency between the capillary and the coupling optical element.
20 . The method of claim 19 , wherein the refractive index of the index matching compound is similar to the refractive index for the capillary.
21 . The method of claim 19 , wherein the refractive index of the index matching compound is similar to the refractive index for the coupling optical element.
22 . The method of claim 16 , wherein the refractive index of the index matching compound is less than refractive index than the coupling optical element.
23 . The method of claim 22 , wherein the refractive index of the index matching compound is in the range from approximately 1.4 to approximately the refractive index of the coupling optical element.
24 . The method of claim 16 , wherein an index of refraction of the coupling optical element is greater than an index of refraction of the capillary.
25 . The method of claim 16 , wherein an index of refraction of a material comprising the capillary is greater than an index of refraction of the sample transported within the capillary.
26 . The method of claim 16 , further comprising directing the non-coherent light into the capillary with a second coupling optical element.
27 . The method of claim 16 , further comprising removing the non-coherent light from the housing after the non-coherent light passes through the detection zone.
28 . The method of claim 16 , wherein the samples are transported through the detection zone by a fluid having an index of refraction lower than an index of refraction of a material comprising the capillary.