Apparatus and method for transient thermal infrared spectrometry

• US 5,070,242 A
• Filed: 07/02/1990
• Issued: 12/03/1991
• Est. Priority Date: 01/13/1989
• Status: Expired due to Term

• Current Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Original Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Inventors: McClelland, John F., Jones, Roger W.
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US07/546,738
• Time in Patent Office: 519 Days
• Field of Search: 250/340, 250/339, 374/5, 356/311
• US Class Current: 250/339.03
• CPC Class Codes: G01N 2021/1714 Photothermal radiometry with measurement of emission
• CPC Class Codes: G01N 2021/1782 In-depth resolution
• CPC Class Codes: G01N 21/71 thermally excited
• CPC Class Codes: G01N 21/85 Investigating moving fluids or granular solids
• CPC Class Codes: G01N 25/72 Investigating presence of flaws

Abstract

A method and apparatus for enabling analysis of a material (16, 42) by applying a cooling medium (20, 54) to cool a thin surface layer portion of the material and to transiently generate a temperature differential between the thin surface layer portion and the lower portion of the material sufficient to alter the thermal infrared emission spectrum of the material from the black-body thermal infrared emission spectrum of the material. The altered thermal infrared emission spectrum of the material is detected by a spectrometer/detector (28, 50) while the altered thermal infrared emission spectrum is sufficiently free of self-absorption by the material of the emitted infrared radiation. The detection is effected prior to the temperature differential propagating into the lower portion of the material to an extent such that the altered thermal infrared emission spectrum is no longer sufficiently free of self-absorption by the material of emitted infrared radiation, so that the detected altered thermal infrared emission spectrum is indicative of the characteristics relating to the molecular composition of the material.

Claims

1. A method for enabling analysis of a material comprising the steps of:

cooling a thin surface layer portion of the material to transiently generate a temperature differential between the thin surface layer portion and a lower portion of the material sufficient to alter the thermal infrared emission spectrum of the material from the black-body thermal infrared emission spectrum of the material; and

detecting the altered thermal infrared emission spectrum of the material while the altered thermal infrared emission spectrum is sufficiently free of self-absorption by the material of emitted infrared radiation, prior to the temperature differential propagating into the lower portion of the material to an extent such that the altered thermal infrared emission spectrum is no longer sufficiently free of self-absorption by the material of emitted infrared radiation, so that the detected altered thermal infrared emission spectrum is indicative of characteristics relating to molecular composition of the material.

4. A method according to claim 1, further comprising a step of determining characteristics relating to the molecular composition of the material in accordance with the detected altered thermal infrared emission.

5. A method according to claim 1, wherein the material is one of a solid material and a liquid material.

6. A method according to claim 5, wherein the solid material is one of a non-flexible material, a flexible material and a rubber-like material and the liquid material is a molten material.

7. A method according to claim 1, wherein the material is one of a stationary material and a moving material.

8. A method according to claim 7, wherein the step of detecting includes detecting the altered thermal infrared emission for a predetermined period of time upon cooling of the surface region.

9. A method according to claim 7, wherein the material is a moving material, the step of detecting includes setting the field of view of detection, and further comprising the step of moving the material into the field of view upon cooling of the surface of the material so as to enable detection of the altered thermal infrared emission, and then moving the material emitting the thermal altered infrared emission out of the field of view of detection.

10. A method according to claim 9, wherein the step of detecting includes utilizing a spectrometer and controlling the field of view thereof, and the step of moving includes utilizing conveyor means for transporting the material relative to the field of view of the spectrometer.

2. A method according to claim I, wherein the step of cooling the surface layer portion of the material includes applying a cooling source to a part of the surface of the material to cause transient cooling of the thin surface layer portion and superposition of the transmission spectrum of the cooled layer on the emission of infrared radiation from the lower portion of the material below the cooled layer and being at a higher temperature than the cooled layer.

3. A method according to claim 2, wherein the step of cooling the thin surface layer portion includes applying a jet of cooling gas at a temperature lower than the temperature of the material being analyzed

11. Apparatus for enabling analysis of a material comprising the steps of:

means for cooling a thin surface layer portion of the material to transiently generate a temperature differential between the thin surface layer portion and a lower portion of the material sufficient to alter the thermal infrared emission spectrum of the material from the black-body thermal infrared emission spectrum of the material; and

means for detecting the altered thermal infrared emission spectrum of the material while the altered thermal infrared emission spectrum is sufficiently free of self-absorption by the material of emitted infrared radiation, prior to the temperature differential propagating into the lower portion of the material to an extent such that the altered thermal infrared emission spectrum is no longer sufficiently free of self-absorption by the material of emitted infrared radiation, so that the detected altered thermal infrared emission spectrum is indicative of characteristics relating to molecular composition of the solid material.

12. Apparatus according to claim 11, wherein the means for cooling the surface layer of the material includes means for applying a cooling source to the surface of the material to cause transient cooling of the thin surface layer portion and superposition of the transmission spectrum of the cooled layer on the emission of infrared radiation from the lower portion of the material below the cooled layer and being at a higher temperature than the cooled layer.

13. Apparatus according to claim 12, wherein the means for cooling the thin surface layer portion includes means for applying a jet of cooling gas at a temperature lower than the temperature of the material being analyzed.

14. Apparatus according to claim 11, further comprising a means for determining characteristics relating to the molecular composition of the material in accordance with the detected altered thermal infrared emission.

15. Apparatus according to claim 11, wherein the material is one of a solid material and a liquid material.

16. Apparatus according to claim 15, wherein the solid material is one of a non-flexible material, a flexible material and a rubber-like material, and the liquid material is a molten material.

17. Apparatus according to claim 11, wherein the material is one of a stationary material and a moving material.

18. Apparatus according to claim 17, wherein the means for detecting includes control means for detecting the altered thermal infrared emission for a predetermined period of time upon cooling of the surface region.

19. Apparatus according to claim 17, wherein the material is a moving material, the means for detecting includes means for setting the field of view for detection, and further comprising means for moving the material into the field of view upon cooling of the surface of the material so as to enable detection of the altered thermal emission, the moving means moving the material emitting the altered infrared emission out of the field of view.

20. Apparatus according to claim 19, wherein the means for detecting includes a spectrometer having a field of view, and the moving means includes conveying means for transporting the material relative to the field of view of the spectrometer

21. Apparatus according to claim 20, wherein the spectrometer provides an output indicative of the detected altered thermal infrared emission, and further comprising means for processing the output of the spectrometer to determine characteristics relating to the molecular composition of the material.