CN101470066A

CN101470066A - Optical sensor for high-flux dust particle counter

Info

Publication number: CN101470066A
Application number: CNA2007101923856A
Authority: CN
Inventors: 卞保民; 彭刚; 王春勇; 贺安之
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2007-12-26
Filing date: 2007-12-26
Publication date: 2009-07-01

Abstract

The invention relates to an optical sensor for a large-flow dust particle counter. It includes a laser light source. In the forward direction of the light source beam, an aspheric mirror, an entrance aperture, an exit aperture and a light trap are arranged in sequence; between the entrance aperture and the exit aperture, an optical path reflector, The position of the field diaphragm and photodetector, the photosensitive area and the photosensitive surface of the photodetector are respectively on both sides near the spherical center of the spherical mirror, and the long rectangular field of view is placed in front of the photodetector and matches the shape of the photosensitive area aperture. The illumination light path and scattered light collection light path of the present invention are simple in design and easy to adjust. A diaphragm is set in front of the photosensitive area to reduce stray light entering the cavity. A diaphragm is set between the photosensitive area and the light trap to prevent light from entering the cavity. The beam of the trap is reflected back into the cavity, which can greatly improve the signal-to-noise ratio of the sensor. The field of view diaphragm adopts a bell mouth type blocking diaphragm to prevent stray light on the optical path from directly entering the detector.

Description

The optical sensor of high-flux dust particle counter

Technical field

The present invention relates to a kind of optical sensor of cleanliness factor checkout equipment, particularly a kind of high-flux dust particle counter.

Background technology

Formerly in the technology, the technical scheme that optical sensor adopted of laser dust particle counter, as the utility model patent " optical sensor of laser dust particle counter " (patent No. be CN2480832Y) of people such as the yellow Hui Jie of Shanghai Optics and Precision Mechanics institute, Chinese Academy of Sciences in application on March 6th, 2002, it adopts right angle diffuse optical system architecture, its lamp optical system optical axis, scattered light collection system axle and air-channel system axle are vertically intersected on the center, photosensitive area in twos, lamp optical system wherein adopts halogen tungsten lamp, be disposed with the illuminating lens group on the light beam working direction that light source sends and place the first interior spherical reflector of light trapping, scattered light is collected the optical axis of light path and the point of illumination path optical axis intersection is the center of photosensitive area, collect on the light path at scattered light, one side is provided with second spherical reflector in the photosensitive area, be provided with receiver lens successively at opposite side, field stop and photodetector.Wherein, be provided with first aplantic lens between light source and the illuminating lens group, between illuminating lens group and photosensitive area, be provided with second aplantic lens, between photosensitive area and receiver lens group, be provided with the 3rd aplantic lens.The problem that prior art exists is: 1, light source adopts halogen tungsten lamp, and thermal value is big, nonmonochromatic source, and light energy use efficiency is low; 2, illumination path and scattered light are collected light path and are provided with a plurality of combination of lensess, and light path is very complicated, and the loss ratio of luminous energy is bigger; 3, adopt retroreflector, make system produce two bundles illuminating bundle in opposite directions, sampling air flow is adopted accurate symmetric illumination, though can improve the photosensitive area luminous energy, improve measurement range, make system regulate difficulty, veiling glare increases, and is unfavorable for the raising of signal to noise ratio (S/N ratio).

Summary of the invention

The object of the present invention is to provide a kind of optical sensor of simple in structure, signal to noise ratio (S/N ratio) is high, particle size resolution is high, sampling flow is big high-flux dust particle counter.

The technology of the present invention solution is: a kind of optical sensor of high-flux dust particle counter, it is characterized in that: it comprises a semiconductor laser light resource that sends divergent laser beam, on the direction that the light beam that this LASER Light Source is sent advances, be provided with aspheric mirror, the first incident diaphragm, the second incident diaphragm, outgoing diaphragm and light trapping successively; Between the second incident diaphragm, outgoing diaphragm, with light path face catoptron, field stop and photodetector are set on the light path vertical direction, the position of photosensitive area and photodetector photosurface is near the both sides the spherical reflector centre of sphere respectively, and the object-image relation of meeting geometric optics; The long rectangular field diaphragm that places the photodetector front and be complementary with the light sensitive area shape; Photodetector adopts highly sensitive photomultiplier; The sampling gas circuit is made up of admission piece, outlet nozzle, and both are relative, and the photosensitive area is symmetrical arranged.

The present invention compared with prior art its significant advantage is: 1, illuminator is a semiconductor laser, the power density height, and it is little, low in energy consumption to generate heat; 2, illumination path and scattered light collection light path design are simple, regulate easily, reduce the loss 3 of luminous energy, on illumination path, two diaphragms are set before the photosensitive area, reduced the parasitic light that enters cavity, between photosensitive area and light trapping, be provided with two diaphragms, prevent that the beam reflection that enters light trapping from returning cavity, can improve the signal to noise ratio (S/N ratio) 4 of sensor greatly, field stop, have special hydraucone formula to block diaphragm, prevent that the parasitic light on the light path from directly entering detector, field stop matches with the photosensitive area size in addition, reduced the reflect stray light 5 that enters detector, the design's flow is 28.3L/min, and is simple in structure.The result that p-poly-phenyl ethene standard particle of the present invention is demarcated shows: the sampling flow of optical sensor of the present invention can be accomplished 28.3L/min, minimum detection particle diameter is 0.3 μ m, can accomplish more than 75% the resolution of 0.38 μ m and 0.54 μ m standard particle.

Description of drawings

Fig. 1 is the structural representation of the optical sensor of high-flux dust particle counter of the present invention.

Fig. 2 is the cut-open view of the optical sensor of high-flux dust particle counter of the present invention.

Fig. 3 is the synoptic diagram of the sampling valve that adopts of the present invention.

Embodiment

In conjunction with Fig. 1, Fig. 2, high-flux dust particle counter optical sensor of the present invention is a right angle scatter-type optical system, comprises illuminator, scattered light collection system, air-channel system.Illuminator is made up of semiconductor laser 1, aspheric mirror 2, the first incident diaphragm 3, the second incident diaphragm 4, outgoing diaphragm 7, light trapping 8, semiconductor laser 1 power is 5mW wavelength 650nm, it sends divergent beams through too short focal length aspheric mirror 2 two-dimension focusings, convergent point is in the back of photosensitive area, with this guarantee photosensitive area 5 vertically light intensity evenly, the width of photosensitive area 5 place's light beams is twices of valve 9 width.Laser beam passes that light sensitive area 5 is laggard goes into light trapping 8, and is sponged by light trapping 8.Wherein, the illumination path diaphragm is all tubaeform, keeps sharp angles, both can prevent the generation of parasitic light, can eliminate the parasitic light on the light path again, can improve the signal to noise ratio (S/N ratio) of sensor greatly.The scattered light collection system mainly is made up of spherical reflector 6, field stop 11 and photomultiplier 12.When tested air communication is crossed light sensitive area 5, the part of the scattered light that dust particle wherein produces directly enters photomultiplier 12, another part reflects post-concentrations on the photosurface of photomultiplier 12 through spherical reflector 6, wherein field stop 11 has special hydraucone formula to block diaphragm, its size and angle are according to the second incident diaphragm 4, the scattered light angle calculation of the position of outgoing diaphragm 7 and spherical reflector 6 reflections is come out, to guarantee that the parasitic light in the light path can not directly enter detector, and the scattered light signal that particle produces is not blocked, and so also can improve the signal to noise ratio (S/N ratio) of sensor greatly.Air-channel system mainly is made of admission piece 9, exhaust nozzle 10.Aspiration pump sucks the tested air in the external world in the optical sensor by admission piece 9, makes the sampling air flow that has tested dust particle by light sensitive area 5, to obtain the scattered light signal of particle.As Fig. 3, admission piece 9, exhaust nozzle 10 are identical, it all is the flat valve that horizontal transition is arranged, its outside dimension is 7*0.6mm, can satisfy the requirement of the big traffic sampling of 28.3L/min, and two relative photosensitive areas 5 of valve are symmetrically distributed, at a distance of 5mm, 5 the diffusion of flat valve design can minimizing air-flow in the photosensitive area, thus the probability that particle appears at low light level district reduced, can improve the particle resolution of sensor greatly.

The result that this most preferred embodiment p-poly-phenyl ethene standard particle is demarcated shows: the sampling flow of optical sensor of the present invention can be accomplished 28.3L/min, minimum detection particle diameter is 0.3 μ m, can accomplish more than 75% the resolution of 0.38 μ m and 0.54 μ m standard particle.

Claims

1. An optical sensor for a large-flow dust particle counter is characterized in that: it includes a semiconductor laser light source [1] that emits a divergent laser beam, and in the direction of the light beam that the laser light source [1] sends out, successively set Aspherical mirror [2], the first entrance aperture [3], the second entrance aperture [4], the exit aperture [7] and the light trap [8]; in the second entrance aperture [4], exit aperture [ 7], set the optical path reflector [6], field diaphragm [11] and photodetector [12] on the vertical direction with the optical path, and the position of the photosensitive area [5] and the photosensitive surface of the photodetector [12] Respectively on both sides near the spherical center of the spherical mirror [6], and satisfy the object-image relationship of geometric optics; the long rectangular field diaphragm [11] placed in front of the photodetector [12] and matching the shape of the photosensitive area ]; the photodetector [12] adopts a high-sensitivity photomultiplier tube; the sampling gas route consists of an air inlet nozzle [9] and an air outlet nozzle [10], both of which are symmetrically arranged relative to the photosensitive area [5].

2. The optical sensor of the laser particle counter according to claim 1, characterized in that an aspheric mirror [2] with short focal length and large numerical aperture is arranged on the optical path, and the laser beam is focused by the aspheric mirror [2], and the focus is in the photosensitive area After [5], it is the side near the light trap.

3. The optical sensor of the laser particle counter according to claim 1 or 2, characterized in that the gas inlet nozzle [9] and the gas outlet nozzle [10] in the gas path adopt flat gas nozzles with horizontal transitions.

4. The optical sensor of the laser particle counter according to claim 1, characterized in that the aperture is trumpet-shaped and maintains a sharp angle, and the surface of the aperture close to the photosensitive area is matte treated.

5. The optical sensor of the laser particle counter according to claim 1, characterized in that a bell mouth is set on the field diaphragm [11].