Method and system for correcting incident light fluctuations in absorption spectroscopy

A technology of absorption spectroscopy and incident light, applied in the field of absorption spectroscopy, which can solve problems such as low frequency modulation sensitivity

Active Publication Date: 2015-09-30
SERVOMEX GRP LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

For example, distributed feedback (DFB) structured laser diodes have fairly low frequency modulation sensitivity, typically less than 0.1 cm per mA of bias current -1 , leading to large RAMs, whi...

Method used

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  • Method and system for correcting incident light fluctuations in absorption spectroscopy
  • Method and system for correcting incident light fluctuations in absorption spectroscopy
  • Method and system for correcting incident light fluctuations in absorption spectroscopy

Examples

Experimental program
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Embodiment 1

[0127] Embodiment 1: A method for correcting the intensity fluctuation effect of incident light in an absorption spectrum system, comprising steps:

[0128] Controlling the light source to emit wavelength-modulated beams;

[0129] applying at least one modulation burst signal to modulate the wavelength modulated beam and / or to modulate a separate beam synchronized with the wavelength modulated beam, the at least one modulated burst signal being a cone signal modulation;

[0130] detecting the one or more modulated light beams after transmission through the sample medium;

[0131] processing the one or more detected beams to obtain at least one detected burst signal and measuring the absorption effect of the one or more measured objects, wherein the processing comprises combining the at least one detected burst signal with an applied at least one A modulated burst signal is compared to determine incident light intensity fluctuations separated from the absorption effect of one ...

Embodiment 2

[0132] Embodiment 2: The method of embodiment 1, comprising selecting at least one wavelength region location and / or duration for at least one burst signal to isolate the burst signal from the measured absorption lines of the one or more measured objects.

Embodiment 3

[0133] Embodiment 3: The method of Embodiment 1 or 2, wherein the light source is a tunable diode laser, and the laser's beam is repeatedly scanned at a scan rate with a period T across a range of values ​​for wavelength modulation of the laser's beam bias current, and wherein the duration of the burst signal is less than period T.

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Abstract

A method and system for correcting the effect of intensity fluctuations of the transmitted light in an absorption spectroscopy system used for the detection or measurement of chemical species in a medium, whereby one or more modulation bursts are imposed onto a light beam that passes through the medium. This burst signal may be obtained by modulating the bias current of a tunable diode laser, and the modulation burst signal may be optimally at the second harmonic of the modulation frequency of a wavelength modulated beam to allow usage of the same signal path processing used for the spectroscopic detection of the measurand for a second harmonic detection system. The burst signal can be controlled using a smooth window function to minimise the effects of non-linear perturbations that are inherent in tunable diode laser wavelength modulation spectroscopy systems, of optical interference fringes (etalons) and of the residual light absorption by background chemical species or the measurand at the wavelength coinciding with the modulation burst.

Description

technical field [0001] The present invention relates generally to absorption spectroscopy and in particular to tunable diode laser absorption spectroscopy. In particular, the invention applies to the detection and measurement of one or more species in gases produced by artificial or natural processes, such as industrial, medical or physiological processes. Background technique [0002] Tunable laser wavelength modulation spectroscopy is widely used in various applications. One such application is the quantification of the amount of a chemical species (analyte) in a substance, especially in man-made or natural processes where conventional techniques are inadequate or ineffective, such as industrial, medical or physiological process gas analysis. [0003] A typical system includes a tunable laser source, such as a tunable diode laser (TDL), which emits a beam focused on a detector. The substance to be analyzed is placed between the tunable laser source and the detector such ...

Claims

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Application Information

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IPC IPC(8): G01N21/31
CPCG01J3/433G01N2021/399G01N21/39G01J3/10G01J3/0297G01J3/027G01N2201/0612G01N21/3504G01J2003/423G01N21/274G01N2201/121G01N2201/1215
Inventor 理查德·P·科瓦契奇巴赫拉姆·阿里扎德伊恩·C·加斯金詹姆斯·D·霍比马丁·洛佩斯
Owner SERVOMEX GRP LTD
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