Cavity ring-down spectrometer having mirror isolation

• US 7,656,532 B2
• Filed: 04/16/2007
• Issued: 02/02/2010
• Est. Priority Date: 04/18/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Cole, Barrett E.
• Primary Examiner(s): Toatley, Jr.; Gregory J
• Assistant Examiner(s): Underwood; Jarreas C
• Application Number:
  US11/735,689
• Publication Number:
  US 20070242266A1
• Time in Patent Office: 1,023 Days
• Field of Search: 356432-444
• US Class Current: 356/432
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 2021/151 Gas blown
• CPC Class Codes: G01N 2021/391 Intracavity sample
• CPC Class Codes: G01N 21/39 using tunable lasers

Abstract

A cavity ring-down spectrometer having a light-conveying structure, a mirror and an isolator. The structure may form a resonator cavity, and the resonator cavity may include a sample sub-cavity and a mirror sub-cavity. A preconcentrator medium may be within a sample sub-cavity, and the medium may adsorb a sample substance entering the sample sub-cavity. A heater may heat the medium to desorb the sample through which a light can propagate. The mirror may be within the mirror sub-cavity, and the mirror may direct light through the mirror sub-cavity and the sample sub-cavity. The isolator may reduce, inhibit or prevent the sample substance in the sample sub-cavity from entering the mirror sub-cavity and affecting the mirror in the mirror sub-cavity.

Claims

1. A cavity ring-down spectrometer comprising:

resonator cavity;

a first sub-cavity situated in the resonator cavity;

a second sub-cavity situated in the resonator cavity;

a mirror situated in the first sub-cavity;

a space for a sample substance situated in the second sub-cavity; and

an isolator situated in the resonator cavity to reduce movement of a substance from one sub-cavity to another sub-cavity.

2. The spectrometer claim 1, wherein:

the mirror is arranged to direct light through the first and second sub-cavities; and

the second sub-cavity is arrangeable for having a sample substance in a path of the light.

3. The spectrometer of claim 1, wherein the isolator provides for a flow of an isolation substance through the first sub-cavity.

4. The spectrometer of claim 1, wherein the isolator comprises a baffle between the first sub-cavity and the second sub-cavity.

5. The spectrometer of claim 4, wherein:

the first sub-cavity comprises an inlet port and an outlet port;

the inlet port is arranged to permit the isolation substance to flow into the first sub-cavity; and

the outlet port is arranged to permit the isolation substance to flow out of the first sub-cavity.

6. The spectrometer of claim 4, wherein the baffle includes a window to permit the light to propagate through the first and second sub-cavities.

7. The spectrometer of claim 1, wherein the second sub-cavity comprises a preconcentration medium and a heater.

8. The spectrometer of claim 2, wherein the second sub-cavity includes a permeable membrane to permit the sample substance to enter the second sub-cavity.

9. The spectrometer of claim 2, wherein the pressure in the first sub-cavity is greater than the pressure in the second sub-cavity.

10. A sensing method comprising:

propagating light through a mirror sub-cavity and a sample sub-cavity of a resonator cavity;

sensing a ring-down rate of the light in response to a sample substance entering the sample sub-cavity; and

reducing migration of the sample substance from the sample sub-cavity to the mirror sub-cavity.

11. The method of claim 10, wherein the reducing of migration of the sample substance from the sample sub-cavity to the mirror sub-cavity comprises a flowing an isolation substance through the mirror sub-cavity.

12. The method of claim 10, wherein the reducing of migration of the sample substance from the sample sub-cavity to the mirror sub-cavity comprises providing a pressure in the mirror sub-cavity that is greater than the pressure in the sample sub-cavity.

13. The method of claim 10, wherein:

the reducing of migration of the sample substance from the sample sub-cavity to the mirror sub-cavity is provided by a baffle that separates the sample sub-cavity and the mirror sub-cavity from each other; and

the baffle has a window for permitting propagation of the light between the sample sub-cavity and the mirror sub-cavity and for preventing a migration of the sample substance from the sample sub-cavity to the mirror sub-cavity.

14. The method of claim 10, wherein the sensing of a ring-down rate of the light in response to a sample substance entering the sample sub-cavity comprises sensing a ring-down rate of the light in response to a sample substance appearing in the sample sub-cavity by use of a preconcentration medium and a heater.

15. A spectrometer system comprising:

a structure forming a resonator cavity having at least first, seconds and third cavity legs; and

wherein;

the first cavity leg includes a first sample sub-cavity;

the second cavity leg includes a second sample sub-cavity;

the third cavity leg includes a third sample sub-cavity;

the resonator cavity further has at least a first mirror sub-cavity having a first mirror, a second mirror sub-cavity having a second mirror, and third mirror sub-cavity having a third mirror;

the first mirror sub-cavity is between the first and second sample sub-cavities;

the second mirror sub-cavity is between the second and third sample sub-cavities; and

the third mirror sub-cavity is between the third and first sample sub-cavities;

the first, second, and third sample sub-cavities are arranged to present corresponding first, second, and third substances;

the first, second, and third mirrors are arranged to direct light through the first, second, and third sample sub-cavities and the first, second, and third mirror sub-cavities; and

,

a first isolator is arranged to reduce movement of the first and/or second substances from the first and second sample sub-cavities to the first mirror sub-cavity;

a second isolator arranged to reduce movement of the second and/or third substances from the second and third sample sub-cavities to the second mirror sub-cavity; and

a third isolator arranged to reduce movement of the third and/or first substances from the third and first sample sub-cavities to the third mirror sub-cavity.

16. The system of claim 15, wherein:

the first isolator comprises first and second baffles isolating the first mirror sub-cavity from the first and sample sub-cavities;

the second isolator comprises third and fourth baffles isolating the second mirror sub-cavity from the second and third sample sub-cavities;

the third isolator comprises fifth and sixth baffles isolating the third mirror sub-cavity from the third and first sample sub-cavities; and

each baffle has a window for transmission of light and prevention of substance migration.

17. The system of claim 15, wherein:

the first mirror sub-cavity comprises at least one inlet port and at least one outlet port;

the inlet port of the first mirror sub-cavity is arranged to permit an inert gas to flow into the first mirror sub-cavity;

the outlet port of the first mirror sub-cavity is arranged to permit an inert gas to flow out of the first mirror sub-cavity;

the second mirror sub-cavity comprises at least one inlet port and at least one outlet port;

the inlet port of the second mirror sub-cavity is arranged to permit an inert gas to flow into the second mirror sub-cavity;

the outlet port of the second mirror sub-cavity is arranged to permit an inert gas to flow out of the second mirror sub-cavity;

the third mirror sub-cavity comprises at least one inlet port and at least one outlet port;

the inlet port of the third mirror sub-cavity is arranged to permit an inert gas to flow into the third mirror sub-cavity; and

the outlet port of the third mirror sub-cavity is arranged to permit an inert gas to flow out of the third mirror sub-cavity.

18. The system of claim 15, further comprising:

a light source; and

a light detector; and

wherein;

the first mirror comprises a partially transmissive mirror;

the light source is arranged to direct light through the partially transmissive mirror and into the resonator cavity; and

the light detector is arranged to detect light emerging from the resonator cavity through the partially transmissive mirror.

19. The system of claim 15, wherein each of the first, second, and third sample sub-cavities comprises a respective preconcentration medium and a respective heater.

20. The system of claim 15, wherein:

the first sample sub-cavity includes a permeable membrane to permit the first substance to enter the first sample sub-cavity;

the second sample sub-cavity includes a permeable membrane to permit the second substance to enter the second sample sub-cavity; and

the third sample sub-cavity includes a permeable membrane to permit the third substance to enter the third sample sub-cavity.