Spectroscopic system and method using a ceramic optical reference
View Patent ↗A ceramic reference in conjunction with a spectrometer, a metallized ceramic material, and a method of utilizing a ceramic material as a reference in the ultraviolet, visible, near-infrared, or infrared spectral regions are presented. The preferred embodiments utilize a ceramic reference material to diffusely reflect incident source light toward a detector element for quantification in a reproducible fashion. Alternative embodiments metallize either the incident surface or back surface of to form a surface diffuse reflectance standard. Optional wavelength reference layers or protective layers may be added to the ceramic or to the metallized layer. The reference ceramic is used to provide a measure of optical signal of an analyzer as a function of the analyzers spatial, temporal, and environmental state.
1. A method of generating a reference signal, comprising steps of:
providing a spectrometer having a source that emits incident photons;
providing an optically rough ceramic element having an incident surface and an internal scattering body;
directing at least a portion of said incident photons toward said incident surface;
scattering said at least said portion of said incident photons by said ceramic; and
detecting at least a portion of said scattered photons, wherein said reference signal is generated.
2. The method of claim 1 , wherein said scattered photons result from physical interaction with at least one of:
said incident surface; and
said internal scattering body.
3. The method of claim 2 , wherein said incident surface of said ceramic diffusely reflects said incident photons.
4. The method of claim 1 , wherein said spectrometer comprises either a single beam analyzer or a dual beam analyzer.
5. The method of claim 1 , further comprising a step of:
operating said spectrometer in diffuse reflectance mode or in transflectance mode.
6. The method of claim 1 , wherein said spectrometer further comprises at least one of:
a coupling optic;
a sample interface optic, separated by a distance from said ceramic; and
a wavelength separation device.
7. The method of claim 6 , wherein said coupling optic is positioned after said ceramic element.
8. The method of claim 6 , further comprising:
a step of varying said distance between said ceramic and said interface optic in order to increase or decrease said signal.
9. The method of claim 6 , wherein said wavelength selection device comprises any of:
a prism;
a grating; and
a Michelson interferometer.
10. The method of claim 1 , wherein said reference signal comprises a reference spectrum.
11. The method of claim 1 , wherein said spectrometer comprises a noninvasive glucose analyzer.
12. The method of claim 2 , further comprising a step of:
coating said incident surface of said ceramic with a first layer contacting and completely covering said incident surface of said ceramic.
13. The method of claim 12 , wherein said first layer comprises at least one of:
a wavelength reference layer; and
a protective coating.
14. The method of claim 13 , wherein said wavelength reference layer comprises at least one of:
polystyrene;
polyethylene;
polypropylene;
epoxy;
plastic;
erbium oxide;
holmium oxide; end
dysprosium oxide.
15. The method of claim 13 , wherein said incident photons and said scattered photons are at least partially absorbed by said wavelength reference layer.
16. The method of claim 15 , further comprising a step of:
utilizing said signal to generate at least one of a transmittance value and an absorbance value.
17. The method of claim 13 , wherein said protective coating comprises any of:
sapphire;
aluminum oxide;
an optically clear epoxy; and
plastic.
18. The method of claim 12 , wherein said first layer comprises:
a first metallized coating,
wherein said first metallized coating scatters said at least a portion of said incident light, preventing said at least a portion of said incident light from penetrating into said internal scattering body of said ceramic.
19. The method of claim 18 , wherein said first metallized coating comprises at least one of:
gold;
silver;
aluminum;
platinum;
chromium;
lead; and
copper.
20. The method of claim 18 , further comprising a step of:
coating said first layer with a second layer in continual contact with and coated over entire said first layer.
21. The method of claim 20 , wherein said second layer comprises at least one of:
a standard wavelength material; and
a protective coating.
22. The method of claim 21 , wherein said standard wavelength material comprises any of:
polystyrene;
polyethylene;
polypropylene;
epoxy;
plastic;
dysprosium oxide;
erbium oxide; and
holmium oxide.
23. The method of claim 21 , further comprising a step of:
utilizing said signal to generate at least one of a transmittance value and an absorbance value.
24. The method of claim 21 , wherein said protective coating comprises any of:
sapphire;
aluminum oxide;
an optically clear epoxy; and
plastic.
25. The method of claim 20 , wherein said second layer comprises:
a second metallized coating.
26. The method of claim 25 , wherein said second metallized coating is any of:
gold;
silver;
aluminum;
platinum;
chromium;
lead; and
copper.
27. The method of claim 25 , further comprising a step of:
applying a third layer in contact with and completely covering said second layer, wherein said third layer is at least one of:
a standard wavelength material; and
a protective coating.
28. The method of claim 27 , wherein said standard wavelength material comprises any of:
polystyrene;
polyethylene;
polypropylene;
epoxy;
plastic;
dysprosium oxide;
erbium oxide; and
holmium oxide.
29. The method of claim 28 , further comprising a step of:
utilizing said signal to generate either a transmittance value or an absorbance value.
30. The method of claim 27 , wherein said protective coating comprises any of:
sapphire;
aluminum oxide;
an optically clear epoxy; and
plastic.
31. An apparatus for generating a reference signal, comprising:
a ceramic having an incident surface and a back surface;
a first layer in continual contact with end coated over at least one of either said incident surface or said back surface, wherein said first layer comprises at least one of:
a first standard wavelength material;
a first protective coating; and
a first metallized coating;
wherein at least one of said incident surface and said back surface is optically rough.
32. The apparatus of claim 31 , wherein said incident surface is flat.
33. The apparatus of claim 31 , wherein said first standard wavelength material comprises at least one of:
polystyrene;
polyethylene;
polypropylene;
epoxy;
plastic;
dysprosium oxide;
erbium oxide; and
holmium oxide.
34. The apparatus of claim 31 , wherein said first protective coating comprises any of:
sapphire;
aluminum oxide; and
plastic.
35. The apparatus of claim 31 , wherein said first metallized coating comprises at least one of:
gold;
silver;
aluminum;
platinum;
chromium;
lead; and
copper.
36. The apparatus of claim 31 , further comprising:.
a second layer in continual contact with and coated over said first layer.
37. The apparatus of claim 36 , wherein said second layer comprises at least one of:
a secondary wavelength material;
a secondary protective coating; and
a secondary metallized coating.
38. The apparatus of claim 37 , wherein said secondary standard wavelength material comprises at least one of:
polystyrene;
polyethylene;
polypropylene;
epoxy;
plastic;
dysprosium oxide;
erbium oxide; and
holmium oxide.
39. The apparatus of claim 37 , wherein said secondary protective coating comprises any of:
sapphire;
aluminum oxide; and
plastic.
40. The apparatus of claim 37 , wherein said secondary metallized coating comprises any of:
gold;
silver;
aluminum;
platinum;
chromium;
lead; and
copper.
41. The apparatus of claim 36 , further comprising:
a third layer in continual contact with and coated over entire said second layer.
42. The apparatus of claim 41 , wherein said second layer comprises:
an outer protective coating.
43. The apparatus of claim 42 , wherein said outer protective coating comprises any of:
sapphire;
aluminum oxide; and
plastic.
44. A method of generating a reference signal, comprising steps of:
providing a spectrometer having a source that emits incident photons;
providing a ceramic material having an incident surface and a metallized back surface;
directing said incident photons through said incident surface, wherein at least a portion of said incident photons traverse said ceramic material and are diffusely reflected by said metallized back surface and subsequently emitted from said incident surface; and
detecting said emitted photons, wherein a reference signal is generated.
45. The method of claim 44 , wherein said metallized back surface of said ceramic is optically rough, such that light hitting said metallized back surface is either reflected or scattered.