JPS63290947A - Instrument for measuring air pollution - Google Patents

Abstract

PURPOSE:To measure the concns. of the hydrocarbons in the atm. by an IR absorption measurement by using a semiconductor laser element which oscillates laser light at the temp. of liquid nitrogen as a light source and forming a multireflection length optical path cell to be introduced with this laser light into a type open to the atm. CONSTITUTION:Pb1-xCdxS1-ySey is disposed in a liquid nitrogen vessel 1 in which the semiconductor laser element is disposed, then the laser light is oscillated. Methane, ethane, and butane are diluted with gaseous nitrogen and are sealed respectively at 100ppm into a gas cell 2 for calibration. The laser light is multiple-reflected by concave mirrors 3'-3'''. Between the concave mirrors 3 and 3'' are opened to the atm. An InSb IR detectors 4, 4' cooled by liquid nitrogen are mounded on the rear side of the respective cell in order to measure the absorption intensity of the laser light. X is determined from Ig/Ic=X/100 where the intensity obtd. from the gas cell 2 for calibration is designated as Ic and the intensity obtd. from the multireflection length optical path cell 3 as Ig. The concnsn. of the respective hydrocarbons in the atm. are thus measured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an air pollution measuring device. More specifically, the present invention relates to a small and lightweight air pollution measurement device that detects photochemical smog by rapidly and accurately measuring the concentration of various hydrocarbon pollution gases in the atmosphere that cause photochemical smog in the field.

PRIOR ART Conventionally, photochemical smog in the atmosphere was measured by prior determination.

However, all of these methods are expensive because they require large equipment, and in order to measure the #gold production of the above gases, it is necessary to take the collected air samples to a laboratory or the like and use RF
) Not only is it necessary to measure the method, but it also has the drawback that it takes time.

Furthermore, a measuring device using infrared absorption spectroscopy using a semiconductor laser element as a light source is also known.

In other words, since the semiconductor laser that emits in the infrared region with a wavelength of 2 to 4 μm, which is suitable for measuring hydrocarbon contamination gases, could only operate at extremely low temperatures, this device was able to maintain its operating state by lowering the temperature to extremely low temperatures using a large refrigerator. Infrared absorption spectroscopy was measured by introducing atmospheric gas into a vacuum-evacuated, sealed, multiple-reflection, long-path cell.

Therefore, this device requires a refrigerator and a vacuum device, making it large in size, and it is also cumbersome to operate, as it is necessary to evacuate the long optical path cell before introducing atmospheric air.
It has been difficult to measure the concentration of air pollutants in a short time while moving in the field.

Additionally, devices are known that measure methane concentration in the atmosphere using short-path absorption spectroscopy using a wavelength tunable semiconductor laser as a light source at a wavelength of 7 to 8 μm, or infrared absorption spectroscopy using reflection from a mirror fixed at a distance. It is being

However, the measurement of hydrocarbons with this device.

In this wavelength region, resonance absorption lines exist only for methane, which is a part of hydrocarbon gases, and this has the disadvantage that it is not suitable as an air pollution measuring device for photochemical smog.

Purpose of the Invention The present invention has been made to eliminate the drawbacks of conventional air pollution measuring devices, and is capable of changing the wavelength range from 2 to 4 μm, does not require a refrigerator or vacuum device, is compact, and can be used outdoors. In order to provide an air pollution measuring device that can quickly and accurately measure air pollution at wavelengths of 2 to 4 μm →j.

A semiconductor laser whose length is variable and which can be obtained by oscillating laser light at liquid nitrogen temperature, that is, the general formula pb1゜cdxS□-yS
eyl and Pb! yMnzs, ySey (however, X
%)'ijo, hx>1, o=y≦1) has been developed. (Unexamined Japanese Patent Publication No. 61-17479
(No. 2, JP-A No. 61-174793) When this is used as a light source for an air pollution measuring device, it can oscillate laser light at the temperature of liquid nitrogen. Concentrations such as these can also be easily obtained on one side. In addition, by making the multiple reflection long-path cell open to the atmosphere, it is no longer necessary to put the atmosphere in a sealed container and take it back to the laboratory for measurements, making it possible to perform measurements quickly in the field. I was able to find out. The present invention was completed based on this knowledge.

The gist of the present invention is to provide an apparatus that uses a semiconductor laser element as a light source and measures hydrocarbon concentration in the atmosphere by performing infrared absorption measurements using absorption of laser light, which is wavelength tunable between 2 and 4 μm. , an air pollution measuring device characterized in that the light source is a semiconductor laser element that oscillates laser light at liquid nitrogen temperature, and the multiple reflection long optical path cell into which the laser light is introduced is open to the atmosphere.

The air pollution gas system # of the present invention will be explained based on the drawings. The drawings show a schematic view of the device of the present invention, and FIG. 1 is a plan view thereof, and FIG. 2 is a side view thereof.

In the figure, 1 is a liquid nitrogen container in which a semiconductor laser element is placed;
2 is a gas cell for calibration, 3 is a multiple reflection long optical path cell open to the atmosphere, 3', 3'', and 3'' are concave mirrors, 4 and 4' are infrared detectors, and 5 is a condensing optical system.

K Pb1 zCdz 5l-ySey in liquid nitrogen container
1 or Pb□) (Mnz s, y Sey (X
s'! is the same as above) and oscillates a laser beam. To calibrate the concentration of the measurement gas, dilute methane, ethane, and butane with nitrogen gas and add them to the calibration gas cell.
Enclose as 100pp. Multiple reflections are performed with 3/, P, and 3" concave mirrors, and the space between the 3/ and 3/f concave mirrors is open to the atmosphere. The number of multiple reflections can be regulated by the inclination angle of the concave mirror. Measure the absorption intensity of the laser beam. The values measured using liquid nitrogen equipment at the back of each cell were the same as those measured after the atmospheric chamber was sealed and taken back to the laboratory.

Effects of the Invention According to the device of the present invention, the concentration of various hydrocarbons that cause photochemical smog can be quickly determined in the field, without the need for a large refrigerator, and by opening the extended multi-reflection long optical path cell to the atmosphere. Because it is a mold, there is no need for a vacuum exhaust system. Therefore, it is lightweight and compact and can be easily carried around in the field while making measurements.

[Brief explanation of the drawing]

The drawings are schematic diagrams of the apparatus of the present invention, with FIG. 1 being a plan view thereof and FIG. 2 being a side view thereof. 1: Liquid nitrogen container in which a semiconductor laser element is placed 2: Calibration gas cell 3: Open to atmosphere multiple reflection long optical path cell 3', 3', 3
M: Concave mirror 4.4': Infrared detector 5: Condensing optical system Patent applicant Ryu Kawa, Director, Institute of Materials Technology, Science and Technology Agency -

Claims (1)

[Scope of Claims] 1) In an apparatus that uses a semiconductor laser element as a light source and measures hydrocarbon concentration in the atmosphere by performing infrared absorption measurement using absorption of laser light, the wavelength can be varied between 2 and 4 μm. An air pollution measuring device characterized in that the light source is a semiconductor laser element that oscillates laser light at liquid nitrogen temperature, and the multiple reflection long optical path cell into which the laser light is introduced is open to the atmosphere. 2) The semiconductor laser element has the general formula Pb_1_−_xCd_
xS_1_-_ySe_y or Pb_1_-_xMn
_xS_1_−_ySe_y (however, x, y are 0≦x
1. The measuring device according to claim 1, which is a semiconductor laser element represented by ≦1, 0≦y≦1.