Method to determine the identity of a material in an object

• US 6,366,353 B1
• Filed: 11/05/1999
• Issued: 04/02/2002
• Est. Priority Date: 11/05/1999
• Status: Expired due to Fees

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Quan, Frederic J-Y, Fu, Xiaodong, Brown, John T., Misra, Mahendra K.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US09/434,700
• Time in Patent Office: 879 Days
• Field of Search: 356/317, 356/318
• US Class Current: 356/318
• CPC Class Codes: C03B 2207/70 Control measures
• CPC Class Codes: C03B 37/014 made entirely or partially by chemical means , e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] C03C17/02 takes precedence
• CPC Class Codes: G01N 21/718 Laser microanalysis, i.e. with formation of sample plasma

Abstract

A method and apparatus for determining an identity of at least one constituent on a soot that is deposited on a substrate is disclosed. The method includes the steps of sending a pulse of energy toward the substrate, focusing the energy to a predetermined point on the substrate to thereby generate a plasma on the substrate and to create at least one photon, detecting the photon using an analysis element, and identifying the constituent in the soot. The method may also include the step of determining the concentration of the constituent. Furthermore, the method may be used to determine the identity and concentration of at least one reactant in a flame of a burner or a reactant stream.

Claims

1. A method of determining an identity and/or amount of at least one constituent in a soot on a soot coated substrate, the method comprising the steps of:

sending a pulse of energy toward the coated substrate;

focusing the energy to a predetermined point on the substrate to thereby generate a plasma on the substrate and to create at least one photon;

detecting the photon using an analysis element; and

determining the identity or amount of the constituent in the soot.

2. The method of claim 1, wherein said determining step is accomplished by laser induced breakdown spectroscopy.

3. The method of claim 1, further comprising the steps of comparing the identity or amount of the constituent to a predetermined set of parameters, and adjusting at least one reaction condition such that the identity or amount of the constituent will be altered to match at least one of the predetermined set of parameters.

4. The method of claim 1, wherein said step of sending a pulse of energy toward the substrate consists of sending the energy at a rate of a plurality of pulses per second.

5. The method of claim 1, wherein the analysis element is a spectrometer.

6. The method of claim 1, wherein said step of focusing the energy to a predetermined point is accomplished with a double convex lens.

7. The method of claim 1, wherein the substrate is an optical fiber precursor element.

8. A method of making an optical fiber soot precursor element in accordance with claim 3, wherein said parameters are selected to form a desired refractive index profile of a core region.

9. The method of claim 1, wherein said step of determining the identity and amount of a constituent in the soot includes identifying a plurality of constituents and the amount of each constituent.

10. The method as defined in claim 9, further comprising the step of determining a molecular composition of the constituents identified.

11. The method of claim 1 further comprising depositing soot on the substrate.

12. A method of determining an identity and/or amount of a at least one reactant in a flame of a chemical vapor deposition process for depositing a soot on a substrate, the method comprising the steps of:

sending a pulse of energy toward the flame; and

focusing the energy to a predetermined point in the flame to thereby generate a plasma in the flame and to create at least one photon;

detecting the photon using an analysis element; and

determining the identity and amount of at least one constituent in the flame.

13. The of method of claim 12, further comprising the steps of:

comparing the identity or amount of the constituent to a predetermined set of parameters; and

adjusting at least one reaction condition such that the identity or amount of the constituent will be altered to match the one of the predetermined set of parameters.

14. The method of claim 12, wherein said step of sending a pulse of energy toward the flame consists of sending the energy at a rate of a plurality of pulses per second.

15. The method of claim 12, wherein the analysis element is a spectrometer.

16. The method of claim 12, wherein said step of focusing the energy to a predetermined point is accomplished with a double convex lens.

17. The method of claim 12, wherein the identity of the constituent is accomplished by laser induced breakdown spectroscopy.

18. The method of claim 13, wherein the at least one reaction condition adjusted is selected from the group consisting of reaction temperature and flow rate of at least one reactant.

19. The method of claim 12, wherein said step of determining the identity and amount of the constituent in the flame includes identifying a plurality of constituents in the flame and the amount of each constituent.

20. The method of claim 19, further comprising determining a molecular composition of the constituents identified.

21. The method of claim 12 further comprising depositing soot on the substrate.

22. A method of determining an identity and/or amount of a at least one reactant in a reactant stream of a chemical vapor deposition process for depositing a soot on a substrate, the method comprising the steps of:

sending a pulse of energy toward the reactant stream;

focusing the energy to a predetermined point in the stream to thereby generate a plasma in the stream and to create at least one photon;

detecting the photon using an analysis element; and

determining the identity or amount of at least one constituent in the stream.

23. The of method of claim 22, further comprising the steps of:

comparing the identity and or amount of the constituent to a predetermined set of parameters; and

adjusting at least one reaction condition such that the identity of the constituent will be altered to match the one of the predetermined set of parameters.

24. The method of claim 22, wherein said determining the identity and/or amount of the constituent is accomplished by laser induced breakdown spectroscopy.

25. The method according to claim 22 further comprising depositing soot on the substrate.

26. A method of forming an optical fiber preform comprising:

depositing soot on to a substrate;

sending a pulse energy toward a target, wherein the target comprises at least one selected from soot deposited on the substrate, a flame of a chemical vapor deposition process for depositing the soot, a reactant stream, and combinations thereof;

focusing the energy to a predetermined point on the target to thereby generate a plasma on the target and to create at least one photon;

detecting the photon using an analysis element; and

determining the identity or amount of at least one constituent of the target.

27. The method of claim 26 wherein said determining step comprises laser induced breakdown spectroscopy.

28. The method of claim 26 further comprising the steps of comparing the identity or amount of the constituent to a predetermined set of parameters, and adjusting at least one reaction condition such that the identity or amount of the constituent will be altered to match at least one of the predetermined set of parameters.