SU591047A1

SU591047A1 - Aerosol spectrometer

Info

Publication number: SU591047A1
Application number: SU752191141A
Authority: SU
Inventors: Ю.А. Быковский; В.И. Калечиц; Э.А. Маныкин; И.Е. Нахутин; П.П. Полуэктов; Ю.Г. Рубежный; И.П. Сипайло
Original assignee: Предприятие П/Я Р-6575; Московский Инженерно-Физический Институт
Priority date: 1975-12-01
Filing date: 1975-12-01
Publication date: 1982-01-07

Description

(54) СПЕКТРОМЕТР ДЛЯ АЭРОЗОЛЕЙ(54) SPECTROMETER FOR AEROSOLS

Изобретение относитс к оптическим устройствам дл исследовани рассе ни света на малые углы и может .быть использовано в лазерных спектрометрах аэрозолей .The invention relates to optical devices for studying light scattering at small angles and can be used in aerosol laser spectrometers.

Известен аэрозольный спектрометр, содержащий камеру, щели дл поступлени анализируемой среды, источник оптического излучени , линзу, фотодетектор, пол ризаторы и поглотитель света 1.An aerosol spectrometer is known that includes a camera, slits for the entry of the analyzed medium, an optical radiation source, a lens, a photodetector, polarizers, and a light absorber 1.

Недостатком его вл етс пониженна точность измерений.Its disadvantage is reduced measurement accuracy.

Известен спектрометр аэрозолей, pai6oтающий на принципе регистрации рассе нного света под малыми углами 2.The aerosol spectrometer is known, which is based on the principle of recording scattered light at low angles 2.

Недостатком его вл етс повышенна погрешность измерений, обусловленна наличием паразитного фона рассе нного излучени . Its disadvantage is the increased measurement error due to the presence of spurious background scattered radiation.

Наиболее близким техническим решением к изобретению вл етс лазерный спек1рометр аэрозолей, использующий оптическое устройство дл исследовани рассе ни света на малые углы 3.The closest technical solution to the invention is an aerosol laser spectrometer using an optical device for studying light scattering at small angles 3.

Это устройство состоит из Не-Ne лазера , инжекционного сопла дл ввода аэрозолей в лазерный луч, световой ловушки, фотоприемника, зеркала с отверстием, расположенного под углом 45° к главной оптической оси системы, линз и диафрагм.This device consists of a He-Ne laser, an injection nozzle for injecting aerosols into a laser beam, a light trap, a photodetector, a mirror with a hole at an angle of 45 ° to the main optical axis of the system, lenses and apertures.

Недостатком этого спектрометра вл етс отсутствие системы дл эффективного устранени паразитного рассе ни на оптических элементах и стенках устройства.The disadvantage of this spectrometer is the lack of a system for effectively eliminating parasitic scattering on the optical elements and the walls of the device.

Целью изобретени вл етс повышение точности и чувствительности измерений малых импульсов света, рассе нного на малые углы относительно главной оптической оси системы, путем исключени фона паразитного рассе ни на элементах оптической схемы.The aim of the invention is to improve the accuracy and sensitivity of measurements of small pulses of light scattered at small angles relative to the main optical axis of the system, by eliminating the background of parasitic scattering on the elements of the optical circuit.

Claims

This is achieved by the fact that behind the device for dividing the light beam passing through the measuring volume into the primary and diffused lens installed, the focus of which is the measuring volume that forms the light scattered in the measuring volume from the parasitic scattering on different elements of the optical circuit, and behind it is installed at least one screen, made in the form of a transparent plate with an opaque circle in the center. The diameter of the circle is smaller than the diameter of the beam of directional radiation. The central part of the screens is designed to absorb parasitic scatter. Each of the screens is in the following interval of distances from the forming lens: ", - {9, -1) TG-;) (9, -1) () the distance from the / -th element, where ui is the source of the parasitic scattering before forming lens; The f-ro parameter of the system element, equal to, / the parameter of the device for dividing the light beam, is equal to d d-ang; the coefficient taking into account the scattering of the edges of the screens (found experimentally), equal to 0.88-0.92; d is the diameter of the hole in the device for separating the light beam; D is the maximum diameter of the scattered light beam incident on the device for separating the light beam; F is the focal length of the forming lens. The drawing shows a schematic diagram of the proposed spectrometer. The spectrometer contains He-Ne daser 1, lenses 2-5, diaphragms 6 and 7, injection nozzle 8, a device 9 for dividing a light beam passing through the measuring volume into the main and diffuse light trap 10, transparent plastics with an opaque circle in the center for the delay of parasitic scattering and the photomultiplier 14. The spectrometer operates as follows. The radiation of a non-iNe laser is focused by a lens 2 onto a pinhole 6 (40 µm in diameter), which cuts off the light scattered on the laser elements, and hits the lens 3, which focuses it on the measuring volume, after which the light beam enters the device for separating the light beam on the main and scattered in the direction of small angles. The latter hits the forming lens 4, which converts the light scattered on the aerosol particle, into a parallel beam, which passes through a system of glass plates 11-.13 with an opaque circle in the center and is focused by the lens 5 to the entrance of the photomultiplier. The parasitic light is absorbed by the plates II -13, and the main laser beam through the hole in the device 9 for separating the light beam enters the light trap 10. In the process of working with the spectrum, its efficiency in eliminating background illumination from the parasitic scattering has been reduced, which was reduced to self-noise level of PMT. Detection of scattered light pulses, made with a spectrometer, reduced the lower limit of the measured particles to 0.09 µm and increased the resolution to 12 Ad The invention The spectrometer for aerosols, containing a source of directional radiation, a system of focusing lenses and diaphragms, an injection nozzle, a device for dividing the light beam, which passed the measuring volume, into the main and diffuse light trap, a scattered light beam shaper and a photodetector, characterized in that switching off the background of parasitic scattering, the shaper of the scattered beam of rays is made in the form of a forming lens, the focus of which is the measuring volume, and behind the forming lens in the direction of propagation of the scattered light BQiro flow at least one screen, made in the form of a transparent plate with an opaque circle on a center whose diameter is smaller than the diameter of the beam of directional radiation, and the transparent plates are installed in the following interval of distances from the forming lens: (b, - 19, -1) / G – S where ui is: gnie hundred of the i-th element is yuschegos pa.razitio source of audio .rasse before imaging lens; the t-ro parameter of the element is 1. the parameter of the device for dividing the light beam, equal to the diameter of the hole in the device for dividing the light beam; a maximum diameter of the light beam incident on the device for separating the light beam; focal length of the forming lens. experimental coefficient equal to 0.88-0.92. Sources of information taken into account in the examination: 1. US Patent No. 3564263, cl. 1973.

2. US patent number 3835.15, cl. 250-218,1974.

3. “Staub Reintalt Luft, V, 30, No. 6, p. 1970 (prototype). .-ff y |. ucHcbriii laser paccefhhf ju cfsin apJ.sum ny szet lich