Chemically-selective detector and methods relating thereto
In accordance with certain embodiments of the present disclosure, a method for adjusting the spectral detectivity of a thermal detector is described. The method includes coating the light sensitive portion of a thermal detector with a first material to reduce the response of the detector. The first material is coated with a second material that is thermally thin and has spectral absorption characteristics. The second material is coated with a third material that is thermally thick, whereby the spectral absorbance of the second material as filtered by the third material primarily determines the thermal conversion of the thermal detector.
1. A method for adjusting the spectral detectivity of a detector, comprising:
coating the detector with a first material to reduce a response of the detector to light;
coating the first material with a second material that has a spectral absorbance; and
coating the second material with a third material, such that the spectral detectivity has a reduced contrast between a sample comprising a pure analyte and a sample comprising an interfering absorbance,
whereby the spectral absorbance of the second material combined with a spectral absorbance of the third material primarily determines a sensitivity of the detector; and
wherein the detector is configured to detect an energy from the second material and not from the third material.
2. The method of claim 1 , wherein the first material is a mirror coating material.
3. The method of claim 2 , wherein the mirror coating is a metal.
4. The method of claim 3 , wherein the metal is gold.
5. The method of claim 1 , wherein the second material is a polymer.
6. The method of claim 5 , wherein the polymer comprises a near infrared dye.
7. The method of claim 6 , wherein the dye absorbs light in the 860 nm spectral region.
8. The method of claim 5 , wherein the polymer comprises an acrylic resin.
9. The method of claim 8 , wherein the acrylic resin comprises an isobutyl methacrylate polymer.
10. The method of claim 1 , wherein the detector comprises a thermopile detector.
11. The method of claim 1 , wherein the third material is a polymer.
12. The method of claim 1 , further comprising:
providing an electrically insulating coating on a light sensitive portion of the detector prior to coating the detector with the first material.
13. The method of claim 12 , wherein the electrically insulating material is a SiO 2 film.
14. The method of claim 1 wherein the third material is optically thick for the interfering absorbance.
15. The method of claim 14 wherein the optically thick material comprises a sample thicker than an absorption depth of the material.
16. The method of claim 1 wherein the energy is a thermal energy.
17. The method of claim 16 wherein the third material is a thermally thick material when the detector is used with a light source that is modulated at a frequency.
18. The method of claim 17 wherein the thermally thick material comprises a sample thicker than a thermal diffusion length for the frequency.
19. The method of claim 17 wherein the frequency is chosen such that the second material is thermally thin and the third material is thermally thick.
20. The method of claim 17 wherein the light source is modulated at a frequency using an optical chopper.
21. The method of claim 1 wherein a pure analyte is selected from the group consisting of nylon, cotton, acrylic, and polyester.
22. The method of claim 1 wherein an interfering absorbance comprises a polymer stain.
23. A detector, comprising:
a layer of light reflecting material disposed on at least a portion of a light sensitive material;
a layer of spectral absorption material covering the light reflecting material; and
a layer of filter material covering the spectral absorption material such that the spectral detectivity has a reduced contrast between a sample comprising a pure analyte and a sample comprising an interfering absorbance, wherein the detector is coupled to detect an energy from the spectral absorption material and not from the filter material.
24. A detector as in claim 23 , further comprising:
a layer of insulating material between the detector and said light reflecting material.
25. A detector as in claim 23 , wherein the light reflecting material is a metal.
26. A detector as in claim 23 , wherein the filter material is a polymer.
27. A detector as in claim 26 , wherein the polymer comprises an acrylic resin.
28. A detector as in claim 26 , wherein the spectral absorption material is a polymer.
29. A method of detecting the presence of a fluid, comprising:
receiving light in a detector to detect a fluid, the light containing information about a fluid, the detector comprising a light sensitive detector material, a layer of light reflecting material covering at least a portion of the light sensitive material, a layer of spectral absorption material covering the light reflecting material, and a layer of filter material covering the spectral absorption material; wherein the layer of filter material has a thickness such that the spectral detectivity has a reduced contrast between a sample comprising a pure analyte and a sample comprising an interfering absorbance; and
the detector is configured to detect an energy from the second material and not from the
third material.