Method and device for improving spectrum detection sensitivity

A spectral detection and sensitivity technology, applied in measurement devices, color/spectral characteristic measurement, material analysis by optical means, etc., can solve the problems of reduced signal-to-noise ratio of detection signals, increased optical transmission loss, and inability to meet detection sensitivity. , to achieve the effect of increasing the detection signal amplitude, improving the detection sensitivity, and reducing the limit

Inactive Publication Date: 2015-09-23
TIANJIN UNIV
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Problems solved by technology

[0004] For trace gas detection, sometimes the concentration of the gas to be measured is very low, such as ppbv (parts per billion by volume, 10 -9 ) or pptv (parts per trillion by volume, 10 -12 ) level, the commercial hollow optical waveguide cannot provide the required measurement optical path, and the too long measurement optical path leads to increased optical transmission loss and reduced signal-to-noise ratio of the detection signal
Therefore, the demand for higher detection sensitivity cannot be met

Method used

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  • Method and device for improving spectrum detection sensitivity
  • Method and device for improving spectrum detection sensitivity

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Embodiment 1

[0032] Such as image 3 As shown, the present embodiment 1 applies the present invention to improve the detection gas concentration sensitivity of the tunable laser absorption spectrum direct absorption method. , a preamplifier 12 and a signal processing unit, the signal processing unit includes a signal generator 6 , an A / D sampling chip 14 and a processor 15 . This embodiment 1 uses the direct absorption method of tuned laser absorption spectrum to detect the gas concentration, and its working principle is: the signal generator 6 outputs a sawtooth voltage signal to the laser driver 7, and the laser driver 7 modulates the laser 8 to send out laser light which is collimated by the collimating lens 9 , The off-axis parabolic mirror 10 is focused and coupled into the gas cell of the hollow optical waveguide 1, after the laser is absorbed by the hollow optical waveguide 1, it is incident on the photodetector 11, and the output signal of the photodetector 11 outputs an electrical...

Embodiment 2

[0036] Such as Figure 4 As shown, the present embodiment 2 applies the present invention to improve the sensitivity of the gas concentration detection method of the tunable laser absorption spectrum harmonic detection method, and the measuring device used includes such as figure 1 with figure 2 The shown device for improving spectral detection sensitivity, laser driver 7, detector 11, preamplifier 12 and signal processing unit, said signal processing unit includes signal generator 6, lock-in amplifier 13, A / D sampling chip 14 and Processor 15. In this embodiment, the working principle of using the tuned laser absorption spectrum harmonic detection method to detect the gas concentration is: the signal generator 6 outputs a superimposed sinusoidal sawtooth voltage signal to the laser driver 7, and the laser driver 7 modulates the laser 8 to emit laser light through the collimator lens 9. The straight and off-axis parabolic mirrors 10 are focused and coupled into the gas cell...

Embodiment 3

[0039] Such as Figure 5 As shown, the present embodiment 3 uses the method of the present invention to improve the Raman spectrum detection gas concentration sensitivity, and the measuring device used includes such as figure 1 with figure 2 The device for improving spectral detection sensitivity, laser driver 7 , spectrometer 20 and processor 15 are shown. The working principle of this embodiment 3 using Raman spectroscopy to detect the gas concentration is: the laser driver 7 drives the laser 8 to emit laser light, which is collimated by the collimator lens 9, and the off-axis parabolic mirror 10 is focused and coupled into the hollow optical waveguide 1 gas pool, and the laser light passes through the hollow After the measured gas is scattered in the optical waveguide 1, it enters the spectrometer 20, and the output spectrum signal of the spectrometer 20 is sent to the processor 15 for processing to obtain the concentration.

[0040] The detection steps of the Raman spec...

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Abstract

The invention discloses a method and device for improving spectrum detection sensitivity. According to the method, the capillary feature of a hollow optical waveguide is used, through active temperature cycle control over the hollow optical waveguide, gas quick gathering and desorption processes are generated in the hollow optical waveguide, and accordingly spectrum detection sensitivity is improved. The device comprises the hollow optical waveguide, a heating/cooling mechanism, a temperature sensor and a temperature controller. The working steps of the device are that gas to be detected goes into the hollow optical waveguide, the hollow optical waveguide is cooled, low temperature is maintained for a while, then, hollow optical waveguide cooling is stopped, quick heating is carried out, high temperature is maintained for a while, during the process, spectral signals with the maximum spectrum detection output amplitude are enhanced spectral signals of gas to be detected, and the concentration of trace gas can be computed according to the enhanced spectral signals.

Description

technical field [0001] The invention belongs to the field of trace gas detection, relates to a method for spectral detection of gas concentration, and is particularly suitable for a spectral measurement method using a hollow optical waveguide as a gas cell. Specifically, it relates to a method and a device for improving the sensitivity of spectral detection. Background technique [0002] Spectral analysis is a common method for online detection of trace gases. This method does not require gas sample preparation or pretreatment. It has fast response, good specificity (strong anti-interference ability), good repeatability, high sensitivity, and no damage to the measured gas. / pollution and other advantages. Mainly used in environmental monitoring, industrial process monitoring, respiratory gas analysis, combustion diagnosis, etc. There are two working methods for spectroscopic detection of trace gases, the first is extraction detection, and the second is open optical path d...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/01G01N21/39
Inventor 杜振辉张哲远李金义
Owner TIANJIN UNIV
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