EP0059593A1
Expired / Lapsed
EP
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Method of and apparatus for monitoring gaseous pollutants
Assignee: Imperial Chemical Industries Ltd
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Filing: 1982-02-23
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Granted: —
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Expires: 2002-02-23
Abstract
Abstract Laser scanning apparatus for the monitoring of gaseous pollutants (e.g. on a chemical plant) in which two laser beams having different wavelengths (one corresponding to an absorption line of the gas to be monitored) and modulated at different frequencies are combined into a single scanning beam. A portion of the scattered radiation is collected, detected and measured to give, for each chosen beam direction, the amount of the gas being monitored. The amount of radiation reaching the detector from the laser source is varied according to a predetermined programme or in response to an external stimulus, and by this means the detector can be protected against severe overload when the beam scans over positions of abnormally high reflectivity.
Inventors
- 👤 John Harry William Cramp
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 09:37
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/31; G01N21/39
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
55 words
A method for the remote quantitive monitoring of one or more selected gases in a gaseous environment, which comprises the method herein specified characterised by the step of varying according to a predetermined programme or in response to an external stimulus, the amount of radiation from the laser source which is detected by the detector.
Claim 2
Independent Claim
55 words
A method for the remote quantitive monitoring of one or more selected gases in a gaseous environment, which comprises the method herein specified characterised by the step of varying according to a predetermined programme or in response to an external stimulus, the amount of radiation from the laser source which is detected by the detector.
Claim 3
Dependent Claim
36 words
A method as claimed in claim 1 in which the step comprises varying according to the predetermined programme or in response to the external stimulus, the amount of radiation reaching the detector from the laser source.
Claim 4
Dependent Claim
36 words
A method as claimed in claim 2, which comprises monitoring the amount of radiation collected and varying the amount of radiation reaching the detector from the laser source in response to the amount of radiation monitored.
Claim 5
Dependent Claim
50 words
A method as claimed in claim 3 in which, whenever the collected radiation exceeds a predetermined threshold, the amount of laser radiation reaching the detector is varied so as to remain within a predetermined range in excess of the threshold for so long as an excess of radiation is collected.
Claim 6
Independent Claim
40 words
A method as claimed in any one of claims 2 to 4, in which the amount of radiation reaching the detector from the laser source is varied by varying the amount of laser radiation which is directed at the locations.
Claim 7
Dependent Claim
35 words
A method as claimed in claim 1 in which the amount of radiation detected by the detector is varied by at least partially desensitising the detector in response to an- increase in its output signal.
Claim 8
Dependent Claim
56 words
Apparatus for the remote quantitative monitoring of one or more selected gases in a gaseous environment, which comprises the apparatus herein specified characterised by the provision of means for varying according to a predetermined programme or in response to an external stimulus, the amount of radiation from the laser source which is detected by the detector.
Claim 9
Dependent Claim
56 words
Apparatus for the remote quantitative monitoring of one or more selected gases in a gaseous environment, which comprises the apparatus herein specified characterised by the provision of means for varying according to a predetermined programme or in response to an external stimulus, the amount of radiation from the laser source which is detected by the detector.
Claim 10
Dependent Claim
23 words
Apparatus as claimed in claim 7, having means for varying the intensity of the combined beam which is directed at the various locations.
Claim 11
Dependent Claim
25 words
9 . Apparatus as claimed in claim 8 is one wherein the intensity varying means comprises means for varying the outputs of the laser sources.
Claim 12
Dependent Claim
86 words
1 0 . Apparatus as claimed in claim 9 comprising position indicating means having a parameter which varies according to the orientation of the scanning means, programme means for storing a predetermined programme correlating the variations of radiation intensity with specific positions of the scanning means, trigger means for comparing the programme and the position of the scanning means and for providing a signal wherever the scanning means positions and predetermined programme match, and a laser power control means responsive to signals from the trigger means.
Claim 13
Dependent Claim
62 words
Apparatus as claimed in any one of claims 7 to 9 comprising means for monitoring the electrical signals derived by the detector, reference means for providing a reference signal characteristic of a predetermined threshold level, a comparator for comparing the detector-derived signal with the reference signal, and a laser power control means connected to and responsive to the output from the comparator.
Claim 14
Dependent Claim
37 words
Apparatus as claimed in claim 11 which comprises means for activating the laser power control means in response to a predetermined programme in addition to that in response to the variations in the amount of radiation collected.
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