OPTICAL GAS DETECTOR

• US 20090086191A1
• Filed: 09/27/2007
• Published: 04/02/2009
• Est. Priority Date: 09/27/2007
• Status: Active Grant

• Current Assignee: Teledyne Detcon, Inc. (Teledyne Technologies Incorporated)
• Original Assignee: Scott Technologies, Inc. (3M Company)
• Inventors: Bristol, L. Rodney
• Granted Patent: US 8,253,942 B2
• Time in Patent Office: Days
• US Class Current: 356/73
• CPC Class Codes: G01N 21/0303 Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment G01N21/031 - G01N21/15 take precedence
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G02B 27/1073 characterized by manufacturing or alignment methods
• CPC Class Codes: G02B 27/144 using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence

Abstract

A gas detector is provided. The gas detector includes a measurement source of optical radiation, a reference source of optical radiation, a measurement detector configured to provide an output signal indicative of a gas of interest, a reference detector configured to provide an output signal at least partially independent of the gas of interest, a measurement optical path extending from the measurement source to the reference and measurement detectors, and a sample region for receiving a gaseous sample. The sample region is located along the measurement optical path. A window is positioned in the measurement optical path downstream from the measurement source and upstream from the reference and measurement detectors. The window is partially transparent to optical radiation and partially reflective to optical radiation. The window is positioned to either reflect a portion of the optical radiation emitted by the reference source into the measurement optical path or to allow a portion of the optical radiation emitted by the reference source to pass through the window into the measurement optical path.

Claims

1. A gas detector comprising:

a measurement source of optical radiation;

a reference source of optical radiation;

a measurement detector configured to provide an output signal indicative of a gas of interest;

a reference detector configured to provide an output signal at least partially independent of the gas of interest;

a measurement optical path extending from the measurement source to the reference and measurement detectors;

a sample region for receiving a gaseous sample, the sample region located along the measurement optical path; and

a window positioned in the measurement optical path downstream from the measurement source and upstream from the reference and measurement detectors, the window being partially transparent to optical radiation and partially reflective to optical radiation, the window being positioned to either reflect a portion of the optical radiation emitted by the reference source into the measurement optical path or to allow a portion of the optical radiation emitted by the reference source to pass through the window into the measurement optical path.

2. The gas detector according to claim 1, wherein if the window is positioned to reflect a portion of the optical radiation emitted by the reference source into the measurement optical path, the window is positioned to allow a portion of the optical radiation emitted by the measurement source to pass through the window along the measurement optical path, and wherein if the window is positioned to allow a portion of the optical radiation emitted by the reference source to pass through the window into the measurement optical path, the window is positioned to reflect a portion of the optical radiation emitted by the measurement source along the measurement optical path.

3. The gas detector according to claim 1, further comprising a beam splitter positioned in the measurement optical path downstream from the window and upstream from the reference and measurement detectors, wherein a first plane extending through the reference source and the window is oriented approximately 45°

to a second plane extending through the beam splitter and whichever of the reference and measurement detectors that receives reflected optical radiation from the beam splitter.

4. The gas detector according to claim 1, wherein the window directs less than approximately 25% of optical radiation emitted from the reference detector into the measurement optical path.

5. The gas detector according to claim 1, wherein the window is angled at approximately 45°

with respect to an emission axis of at least one of the reference source and the measurement source.

6. The gas detector according to claim 1, wherein the window is a first window, the gas detector further comprising a second window positioned in the measurement optical path downstream from the measurement source and upstream from the sample region.

7. The gas detector according to claim 1, further comprising a beam splitter positioned in the measurement optical path downstream from the window and upstream from the measurement and reference detectors, the beam splitter configured to direct a portion of the optical radiation emitted from the measurement source to the measurement detector and another portion of the optical radiation emitted from the measurement source to the reference detector, the beam splitter being configured to direct a portion of the optical radiation emitted from the reference source to the measurement detector and another portion of the optical radiation emitted from the reference source to the reference detector.

8. The gas detector according to claim 1, further comprising a collimating lens positioned in the measurement optical path downstream from the window and upstream from the reference and measurement detectors.

9. The gas detector according to claim 1, wherein a portion of the measurement optical path extending through the sample region is approximately straight.

10. A gas detector comprising:

a measurement source of optical radiation;

a reference source of optical radiation; and

a beam splitter partially transparent to optical radiation and partially reflective to optical radiation, the beam splitter having a first side and an opposite second side, the first side being positioned to receive optical radiation from both the measurement source and the reference source.

11. The gas detector according to claim 10, wherein the beam splitter is configured to split the optical radiation from the measurement source and the reference source in substantially equal ratios.

12. The gas detector according to claim 10, further comprising a detector, the beam splitter directing at least a portion of the optical radiation emitted by the measurement source to the detector, the beam splitter directing at least a portion of the optical radiation emitted by the reference source to the detector.

13. A gas detector comprising:

a measurement source of optical radiation;

a reference source of optical radiation;

a measurement detector configured to provide an output signal indicative of a gas of interest;

a reference detector configured to provide an output signal at least partially independent of the gas of interest; and

a beam splitter partially transparent to optical radiation and partially reflective to optical radiation, the beam splitter being configured to allow a portion of the optical radiation emitted by both the reference and measurement sources to pass therethrough to one of the measurement detector and the reference detector, the beam splitter being configured to reflect a portion of the optical radiation emitted by both the reference and measurement sources to the other of the measurement and reference detectors.

14. The gas detector according to claim 13, wherein the beam splitter is configured to allow approximately the same amount of optical radiation from the measurement source and the reference source to pass therethrough, and the beam splitter is configured to reflect approximately the same amount of optical radiation from the measurement source and the reference source.

15. A method for detecting a gas of interest using a sample region having a gaseous sample therein, said method comprising:

transmitting optical radiation from a measurement source along a measurement optical path extending from the measurement source, through the sample region, and to a measurement detector and a reference detector; and

transmitting optical radiation from a reference source to a window that either reflects a portion of the optical radiation emitted by the reference source into the measurement optical path or allows a portion of the optical radiation emitted by the reference source to pass through the window into the measurement optical path.

16. The method according to claim 15, wherein transmitting optical radiation from the measurement source and transmitting optical radiation from reference source are performed alternatingly.

17. The method according to claim 15, wherein transmitting optical radiation from the measurement source and transmitting optical radiation from reference source are performed simultaneously.

18. The method according to claim 15, wherein transmitting optical radiation from the measurement source comprises transmitting optical radiation from the measurement source through the sample region and the window, and to a beam splitter that directs a portion of the optical radiation to the measurement detector and directs another portion of the optical radiation to the reference detector.

19. The method according to claim 15, wherein transmitting optical radiation from the measurement source comprises reflecting optical radiation emitted from the measurement source off of the window and to a beam splitter that directs a portion of the optical radiation to the measurement detector and directs another portion of the optical radiation to the reference detector.

20. The method according to claim 15, wherein transmitting optical radiation from the reference source comprises reflecting optical radiation emitted from the reference source off of the window and to a beam splitter that directs a portion of the optical radiation to the measurement detector and directs another portion of the optical radiation to the reference detector.

21. The method according to claim 15, wherein transmitting optical radiation from the reference source comprises transmitting optical radiation from the reference source through the window and to a beam splitter that directs a portion of the optical radiation to the measurement detector and directs another portion of the optical radiation to the reference detector.

22. The method according to claim 15, wherein transmitting optical radiation from the measurement source and transmitting optical radiation from the reference source comprises transmitting optical radiation from the measurement source and optical radiation from the reference source to the same side of a beam splitter.