Emissivity enhanced mid IR source

• US 8,975,604 B2
• Filed: 09/18/2009
• Issued: 03/10/2015
• Est. Priority Date: 09/18/2009
• Status: Active Grant

• Current Assignee: Thermo Electron Scientific Instruments LLC (Thermo Fisher Scientific Incorporated)
• Original Assignee: Thermo Electron Scientific Instruments LLC (Thermo Fisher Scientific Incorporated)
• Inventors: Iverson, John R., Coffin, John Magie
• Primary Examiner(s): Ippolito, Nicole
• Assistant Examiner(s): MCCORMACK, JASON L
• Application Number:
  US12/562,688
• Publication Number:
  US 20110068271A1
• Time in Patent Office: 1,999 Days
• Field of Search: 250/504.R, 250/495.1, 250/503.1, 219/553
• US Class Current: 250/504.R
• CPC Class Codes: G01J 3/108 for measurement in the infrared range

Abstract

An infrared (IR) source apparatus that includes a desired infrared source element coupled to an insulating housing so to minimize overall source inefficiency at desired optical bandwidths is introduced. The insulation itself is machined or configured in a way so that the infrared source element is in contact with a designed cavity in the insulation so that the IR source image becomes the average of the insulation material and the infrared element. Such an arrangement of the present invention increases the emissivity of the IR source below about 1500 wave numbers, more often, below about 1100 wave numbers, and even more particularly, at about 1079 wave numbers. Accordingly, the combined emissivity of the infrared source and the insulation substantially enhances spectral emission and eliminates or reduces spectral artifacts from the formation of oxides on the infrared source surfaces.

Claims

1. An infrared source, comprising:

a silicon nitride infrared element configured to be exposed to the ambient atmosphere, wherein said silicon nitride infrared element provides infrared radiation at desired wavelengths when heated to a predetermined temperature range; and

an insulator coupled with said silicon nitride infrared element, the insulator configured so as to reach a collaborative temperature range provided by the generated heat from said silicon nitride infrared element, wherein said insulator at said collaborative temperature range provides for one or more desired infrared emission spectral bands that co-add with the output emission of said silicon nitride infrared element so as to eliminate spectral deficiencies resulting from said silicon nitride infrared element reaching said collaborative temperature range,

wherein one or more walls of said insulator are configured as a conical interior that converges towards an opening formed by said walls that defines an optical aperture of said source so as to enhance co-added emission of said insulator and said silicon nitride infrared element optical spectral output and additionally match a field of view of a coupled spectrometer imaging element,

wherein the surface of said walls which form said conical interior are exposed such that said desired infrared emission spectral bands are emitted from said surface and co-add with the output emission of said silicon nitride infrared element,

and further wherein said conical interior is characterized by an outside diameter at one end and a smaller, inside diameter at an opposing end and wherein said walls which form said conical interior are further configured to provide an elongated channel which extends from said opposing end of said conical interior and terminates at said opening which defines said optical aperture, said elongated channel characterized by a length defined from said opposing end to said opening, and further wherein said silicon nitride infrared element is nested within said elongated channel and positioned at said opening such that within said elongated channel said insulator contacts all sides of said silicon nitride infrared element except for an exposed surface at said opening.

2. The infrared source of claim 1, wherein said co-added one or more desired infrared emission spectral bands provided by said heated insulator comprise optical radiation of less than about 1500 cm⁻

1.

3. The infrared source of claim 1, wherein said co-added one or more desired infrared emission spectral bands provided by said heated insulator comprise optical radiation of at about 1079 cm⁻

1.

4. The infrared source of claim 1, wherein said insulator heats up to a desired temperature range with said infrared element that increases the co-added emissivity by up to about 50%.

5. The infrared source of claim 1, wherein said insulator comprises a porous ceramic material configured to withstand the operating temperatures.

6. The infrared source of claim 1, wherein said insulator comprises at least one insulator selected from:

an aluminum oxide or a zirconium insulator.

7. The infrared source of claim 1, wherein said predetermined temperature range comprises a range from about 700 degrees C. up to about 1400 degrees C.

8. The infrared source of claim 1, wherein collaborative temperature range comprises a range from about 700 degrees C. up to about 1400 degrees C.

9. The infrared source of claim 1, wherein said silicon nitride infrared element is heated by an electrical source or an optical source.

10. The infrared source of claim 9, wherein said optical source includes a laser diode.

11. The infrared source of claim 1, wherein said walls of said insulator are configured as conical interior surfaces converging to a circular opening which defines said optical aperture of said source.

12. The infrared source of claim 11, wherein said coupled spectrometer imaging element comprises f-numbers from about f/4 to about f/1 so as to have said field of view optimized with said optical aperture.

13. The infrared source of claim 1, wherein said outside diameter is about 0.210 inches or less, said inside diameter is about 0.180 inches or less and said length is about 0.020 inches or less.

14. The infrared source of claim 1, wherein said silicon nitride infrared element is a glow plug comprising a plug of silicon nitride configured as a sleeve about a tungsten element.

15. The infrared source of claim 14, wherein said glow plug is characterized by a diameter in the range of from about 0.125 inches to about 0.185 inches.

16. The infrared source of claim 1, wherein said silicon nitride infrared element, said conical interior and said elongated channel are exposed to the ambient atmosphere surrounding said infrared source when heated.

17. The infrared source of claim 16, wherein said predetermined temperature range is from about 1100 degrees C. up to about 1400 degrees C.

18. The infrared source of claim 1, wherein said infrared source does not comprise a window through which said co-added emission of said insulator and said silicon nitride infrared element is emitted.

19. The infrared source of claim 18, wherein said predetermined temperature range is from about 1100 degrees C. up to about 1400 degrees C.