CN100561181C - A kind of fire smoke particle stokes scattering matrix measuring method and device - Google Patents

Abstract

Fire smoke particle stokes scattering matrix measuring method of the present invention and device, feature be by the laser of laser emitting through polaroid and electrooptic modulator after, be incident to smoke particle generation light scattering, adjusting by three-dimensional regulating mechanism, make smoke particle be positioned at the center of circle that pivoted arm rotates, pivoted arm is fixed on the rotating disk, rotate around smoke particle by computer control motor driven pivoted arm, on pivoted arm, collimating eyelet is installed successively, quarter wave plate, polaroid and photomultiplier, on a certain fixedly scattering angle, collimating eyelet and photomultiplier are installed, two measured signals of photomultiplier are gathered by computing machine by lock-in amplifier, and are synchronous by signal generator between electrooptic modulator and the lock-in amplifier; The present invention can promote the excavation of smoke particle light scattering information greatly with the angular distribution of all elements in the stokes scattering matrix of higher angular resolution and precision measure fire grain optical scattering.

Description

A kind of fire smoke particle stokes scattering matrix measuring method and device

Technical field:

The invention belongs to the fire detection technology field, particularly the measuring method and the device of the stokes scattering matrix of fire smoke particle light scattering.

Background technology:

" fire safety evaluating periodical " (Fire Safety Journal of Britain issuing, 1997, the 29th volume, the 77-85 page or leaf) points out, smoke particle is one of early stage key character parameter of fire, and the measurement of smoke particle light scattering feature has important effect with the development of excavating for the photoelectric smoke Detection Techniques.And " fire safety evaluating periodical " (Fire Safety Journal, 1997, the 29th volume, the 185-194 page or leaf) a kind of fire smoke particle light scattering experimental provision of mentioning, the light scattering feature of multichannel photomultiplier measurement smoke particle is installed on semicircular ring, this device is merely able to measure the light intensity and the linear polarization degree of scattered light, these 2 parameters only are 2 elements describing in detail in the stokes scattering matrix of smoke particle light scattering information, can't measure and have lost a large amount of smoke particle light scattering informations all 16 elements in the stokes scattering matrix; In addition, the photomultiplier number of installing on the annulus of this device is limited, can only measure the scattered light on the corresponding discrete angle, the angular distribution trend of coarse analysis scattered signal, and can't measure the angular distribution feature of scattered light signal meticulously with less angle step, promptly the angular resolution of the scattered light signal of this measurement device is lower, and precision is relatively poor.

Summary of the invention:

The objective of the invention is to propose a kind of fire smoke particle stokes scattering matrix measuring method and device, can be with all 16 elements in the stokes scattering matrix of higher precision and angular resolution measurement smoke particle.

Fire smoke particle stokes scattering matrix measurement mechanism of the present invention is included in that laser instrument 1 emitting laser bundle is incident to the smoke particle 6 of aerosol spraying head 7 ejection and first photomultiplier 16 of receiving scattered light signal is installed around the scattering luminous point that forms; It is characterized in that: by laser instrument 1 emitting laser bundle before being incident to smoke particle 6 earlier through first polaroid 2, and modulate via electrooptic modulator 3; The center that is used to install the optical table 22 of optics and mechanical devices has hole 5, rotating disk 4 with perforate places the positive center of optical table 22, aerosol spraying head 7 is fixed on the center of optical table 22 by three-dimensional regulation parts 8, pivoted arm 17 is fixed on the rotating disk 4, motor 18 drives pivoted arm 17 and rotates around smoke particle 6, on the light path in first photomultiplier, 16 the place aheads, be provided with second polaroid 15 successively, quarter wave plate 14 and collimating eyelet 13, these four device package are installed on the pivoted arm 17 in 12 li in box and by three-dimensional regulation parts 11, on a certain fixedly scattering angle of second half circumference of smoke particle light scattering, along the light path of scattered light the collimating eyelet 9 and second photomultiplier 10 are installed successively, the signal output part of described second photomultiplier 10 and first photomultiplier 16 connects the signal input part of lock-in amplifier 21, the parallel port output signal end of computing machine 20 is connected with the signal output part of motor 18, the serial ports of computing machine 20 is connected with the serial ports of lock-in amplifier 21, and the signal output part of signal generator 19 connects the signal input part of electrooptic modulator 3 and lock-in amplifier 21.

Fire smoke particle stokes scattering matrix measuring method of the present invention comprises that the scattered light that laser beam incident is formed to smoke particle carries out photomultiplier transit and measures; It is characterized in that: laser beam is modulated with electrooptic modulator after through first polaroid, be incident to smoke particle generation light scattering then, photomultiplier transit measuring element front end is equipped with the quarter wave plate and second polaroid, the optical axis direction of first polaroid, electrooptic modulator, quarter wave plate and second polaroid is respectively: (a) " 0 ° ;-45 °;--,--"; (b) " 0 ° ,-45 °,--, 0 ° "; (c) " 0 ° ,-45 °,--, 45 ° "; (d) " 0 ° ,-45 °, 0 °, 45 ° "; (e) " 45 °, 0 °,--,--"; (f) " 45 °, 0 °,--, 0 ° "; (g) " 45 °, 0 °,--, 45 ° "; (h) " 45 °, 0 °, 0 °, 45 ° ", wherein symbol "--" represent this device need not, under above-mentioned 8 combination conditions, measure direct current, an order harmonics and the distribution of the second harmonic component on semi-circumference of scattered light signal respectively; On a certain fixedly scattering angle, measure scattered light intensity curve over time, will fixedly record each rank scattered light signal component that the corresponding light intensity value constantly of curve obtains correcting on the scattering angle divided by this at each rank scattered light signal of measuring on the semi-circumference; Direct current, an order harmonics and the second harmonic signal after the correcting that directly record under (a) and (e) combination condition obtain 4 matrix element F ₁₁(θ), F ₁₂(θ), F ₁₃(θ) and F ₁₄(θ), with (b), (c) and (d) combination condition measure down after correcting each rank signal deduct respective measurement values under (a) combination condition, and with (f), (g) and (h) combination condition measure down after correcting each rank signal deduct respective measurement values under (e) combination condition, thereby obtain the angular distribution feature of all the other 12 elements in the smoke particle stokes scattering matrix; The smoke particle stokes scattering matrix of described measurement is meant the matrix F (θ) of 4 * 4 shown in the following formula:

$\left[\begin{array}{c}{I}^{\mathrm{sca}}\left(\mathrm{\&theta;}\right)\\ Q^{\mathrm{sca}}\left(\mathrm{\&theta;}\right)\\ U^{\mathrm{sca}}\left(\mathrm{\&theta;}\right)\\ V^{\mathrm{sca}}\left(\mathrm{\&theta;}\right)\end{array}\right]=\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C2006100881880010H1.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="C2006100881880010H1.png"\; state="\{\{state\}\}">k</figure-callout>}}^2}\&CenterDot;\left[\begin{array}{cccc}{F}_{11}\left(\mathrm{\&theta;}\right)& F_{12}\left(\mathrm{\&theta;}\right)& F_{13}\left(\mathrm{\&theta;}\right)& F_{14}\left(\mathrm{\&theta;}\right)\\ F_{21}\left(\mathrm{\&theta;}\right)& F_{22}\left(\mathrm{\&theta;}\right)& F_{23}\left(\mathrm{\&theta;}\right)& F_{24}\left(\mathrm{\&theta;}\right)\\ F_{31}\left(\mathrm{\&theta;}\right)& F_{32}\left(\mathrm{\&theta;}\right)& F_{33}\left(\mathrm{\&theta;}\right)& F_{34}\left(\mathrm{\&theta;}\right)\\ F_{41}\left(\mathrm{\&theta;}\right)& F_{42}\left(\mathrm{\&theta;}\right)& F_{43}\left(\mathrm{\&theta;}\right)& F_{44}\left(\mathrm{\&theta;}\right)\end{array}\right]\&CenterDot;\left[\begin{array}{c}{I}^{\mathrm{inc}}\\ Q^{\mathrm{inc}}\\ U^{\mathrm{inc}}\\ V^{\mathrm{inc}}\end{array}\right].$

Existing apparatus is merely able to measure the light intensity and the linear polarization degree of scattered light, and the present invention is owing to adopt polaroid and electrooptic modulator to modulate to incident laser, and the quarter wave plate and second polaroid are installed at the first photomultiplier front end of receiving scattered light signal, utilize the direct current signal and the harmonic signal of lock-in amplifier collection of scattered light, rotate around smoke particle scattering luminous point by pivoted arm, thereby can measure the angular distribution curve of all elements in the smoke particle stokes scattering matrix, therefore, the present invention can measure much abundant smoke particle light scattering information, for more new criterions are excavated in the design of photoelectric smoke detector.

The angular resolution that the existing apparatus scattered light signal is measured is lower, this device is on 0.3 meter the semi-circumference 14 photomultipliers to be installed at a diameter, whole device is quite full, this moment, corresponding angular resolution only was 12 °, promptly every 12 ° of scattered light signals of measuring on the angle, can only be by the angular distribution trend of measured value coarse analysis scattered signal on these several discrete angles.And the present invention rotates around smoke particle scattering luminous point by motor control pivoted arm, by the angular distribution that is installed on the first photomultiplier measurement scattered light of aiming at the scattering luminous point on the pivoted arm all the time, rotation by motor control pivoted arm can reach very high precision, for example the motor pivoted arm that whenever makes a move only rotates 0.0045 °, so the present invention can be with the angular distribution feature of very little angle step detailed measurements scattered light.

Smoke particle concentration at actual measurement slightly changes, and a certain fixedly scattering angle on the scattered light intensity value determine by smoke particle concentration, the present invention takes to adopt second photomultiplier measurement scattered light intensity curve over time on a certain fixedly scattering angle on the circumference, the scattered light signal that first multiplier tube is recorded divided by second multiplier tube record corresponding the time scattered light intensity that engraves, thereby eliminated the influence that the smoke particle concentration change is brought, improved measuring accuracy.

Compare with the device of linear polarization degree by the light intensity that a plurality of photomultiplier measurement smoke particle scattered lights are installed on semi-circumference with existing, the present invention can be with the angular distribution of all elements in the stokes scattering matrix of higher angular resolution and precision measure smoke particle, thereby excavates more information for the design of photoelectric smoke detector.

Description of drawings:

Fig. 1 is the structural principle synoptic diagram of fire smoke particle stokes scattering matrix measuring method of the present invention and device.

Embodiment:

Below in conjunction with description of drawings the specific embodiment of the present invention.

Embodiment 1:

On the optical table 22 that each optics in the present embodiment smoke particle stokes scattering matrix measurement mechanism and mechanical part are installed on 1.4 * 1.6 meters, it is 0.1 meter circular hole 5 that the center of this optical table has a diameter.Cross sectional dimensions be 0.25 * 0.25 meter, center to have diameter be the positive center that the square universal stage 4 of 0.08 meter perforate is installed on optical table, the perforate of universal stage is overlapped at the center each other with the perforate of optical table.Aerosol spraying head 7 passes the perforate of optical table and rotation platform from bottom to top, and be installed on the optical table by three-dimensional regulation parts 8, smoke particle that the aerosol spraying head ejects stream directly enters the smoke discharging pipe that is positioned at directly over it, the vertical column of smoke 6 that only exposes one section about 3 centimeter length between aerosol spraying head and the smoke exhaust pipe carries out light scattering measurement, thereby guaranteeing that smoke particle can not overflow fills the air in measuring chamber.As shown in Figure 1, after laser instrument 1 shoot laser is modulated through first polaroid 2 and through electrooptic modulator 3, be incident to smoke particle stream 6 light scattering takes place, one has rail plate, length is that 1 meter pivoted arm 17 1 ends are fixed on the rotation platform 4, rotate by computing machine 20 control motors 18 driven in rotation platforms 4, rotate around smoke particle scattering luminous point thereby drive this pivoted arm.Along the scattering light path, successively collimating eyelet 13, quarter wave plate 14, second polaroid 15 and first photomultiplier 16 are packaged in 12 li in a box, this box is installed on the pivoted arm 17 by three-dimensional regulation parts 11, this box can be along slippage before and after the guide rail of pivoted arm, thereby adjusts the distance between first photomultiplier and the smoke particle scattering luminous point.With the incoming laser beam is the boundary, and the rotational plane of whole rotation platform can be divided into upper half and lower half, and wherein pivoted arm 17 rotates in the lower half scope, in a certain fixedly scattering angle position of upper half the collimating eyelet 9 and second photomultiplier 10 is installed.The scattered light signal that photomultiplier 10 and 16 records inserts lock-in amplifier 21 and carries out data acquisition by computing machine 20, is undertaken synchronously by signal generator 19 between electrooptic modulator 3 and the lock-in amplifier 21.

The described smoke particle stokes scattering matrix that needs to measure is the matrix F (θ) of 4 * 4 shown in the following formula (1):

$\left[\begin{array}{c}{I}^{\mathrm{sca}}\left(\mathrm{\&theta;}\right)\\ Q^{\mathrm{sca}}\left(\mathrm{\&theta;}\right)\\ U^{\mathrm{sca}}\left(\mathrm{\&theta;}\right)\\ V^{\mathrm{sca}}\left(\mathrm{\&theta;}\right)\end{array}\right]=\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C2006100881880010H1.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="C2006100881880010H1.png"\; state="\{\{state\}\}">k</figure-callout>}}^2}\&CenterDot;\left[\begin{array}{cccc}{F}_{11}\left(\mathrm{\&theta;}\right)& F_{12}\left(\mathrm{\&theta;}\right)& F_{13}\left(\mathrm{\&theta;}\right)& F_{14}\left(\mathrm{\&theta;}\right)\\ F_{21}\left(\mathrm{\&theta;}\right)& F_{22}\left(\mathrm{\&theta;}\right)& F_{23}\left(\mathrm{\&theta;}\right)& F_{24}\left(\mathrm{\&theta;}\right)\\ F_{31}\left(\mathrm{\&theta;}\right)& F_{32}\left(\mathrm{\&theta;}\right)& F_{33}\left(\mathrm{\&theta;}\right)& F_{34}\left(\mathrm{\&theta;}\right)\\ F_{41}\left(\mathrm{\&theta;}\right)& F_{42}\left(\mathrm{\&theta;}\right)& F_{43}\left(\mathrm{\&theta;}\right)& F_{44}\left(\mathrm{\&theta;}\right)\end{array}\right]\&CenterDot;\left[\begin{array}{c}{I}^{\mathrm{inc}}\\ Q^{\mathrm{inc}}\\ U^{\mathrm{inc}}\\ V^{\mathrm{inc}}\end{array}\right]---\left(1\right)$

What the laser instrument 1 in the present embodiment adopted is the ruddiness DD-635-5-N-type semiconductor N laser instrument that Xi produces; What electrooptic modulator 3 adopted is the 350-50 type product that U.S. Conoptics company produces; What photomultiplier 10 and 16 adopted is the H5784-20 type product that the loose company in Japanese shore produces; What lock-in amplifier 21 adopted is the 7265 type products that U.S. Signal Recovery company produces.

Described motor 18 whenever walked for 200 steps, 0.9 ° of pivoted arm 16 corresponding rotation, and promptly motor 18 walked for 1 step, and dress arm 17 only rotates 0.0045 °, and visible motor can accurately be controlled the rotation of pivoted arm, and computing machine is every to send a pulse to motor, and motor is corresponding walked for 1 step.

Described collimating eyelet 9 and 13 all has former and later two apertures, and the distance between two apertures is 80 millimeters, and the aperture is 1 millimeter, and near 80 centimetres of the aperture distance centers of smoke particle scattering center, promptly hole diameter length is 0.225 ° with respect to the angle of scattering center.

Before the experiment beginning, by two three-dimensional regulation parts 8 in the device and 11, adjust the locus of aerosol spraying head 7, and the spatial orientation of the box 12 of adjusting encapsulation collimating eyelet 13 and photomultiplier 16 etc., rotating disk 4 is driven in pivoted arm 17 rotation processes, and collimating eyelet 13 is aimed at the smoke particle scattering center all the time.Like this, when the angular distribution of carrying out the smoke particle scattered light is measured, just can guarantee with the scattered light signal on the higher precision measure different angles.

In order to measure the whole stokes scattering matrix of smoke particle light scattering, in apparatus of the present invention, incident light adopts electrooptic modulator 3 to modulate through first polaroid, 2 backs earlier, and then be incident to smoke particle 6 generation light scattering, and the quarter wave plate 14 and second polaroid 15 are installed at first photomultiplier, 16 front ends of receiving scattered light.

Below this light path in the device is carried out the analysis of optical delivery equation:

With plane, optical table place is reference planes, incident light and scattered light all adopt corresponding Stokes vector description, and the available corresponding Muller matrix description of effect of each optical device in the device, wherein the Muller matrix of each optical device is main relevant with respect to the angle of reference planes with its optical axis direction.With interior harmonic component, then the scattered light signal that receives of photomultiplier 16 is for as shown in the formula shown in (2) at the DC component of scattered light signal and 2 rank:

I ^sca(θ)＝c ₂[DC(θ)+2J ₁(φ ₀)S(θ)sinωt+2J ₂(φ ₀)C(θ)cos2ωt] (2)

During measurement, be added in modulation voltage amplitude on the electrooptic modulator 3, make J by adjusting ₁(φ ₀)=0, i.e. φ ₀=2.40483, thereby 2J is arranged ₁(φ ₀)=1.03830,2J ₂(φ ₀)=0.86350.By formula (2) as seen, comprise 3 components in the scattered light signal that first photomultiplier 16 is received, i.e. DC component DC (θ), 1 order harmonic component S (θ) and 2 order harmonic component C (θ).In smoke particle scattering light path under the different direction of optic axis corner conditions of first polaroid 2, electrooptic modulator 3, quarter wave plate 14 and second polaroid 15, has different corresponding relations between each element in measured 3 component of signals of scattered light of first photomultiplier 16 and the stokes scattering matrix.

Table 1 has provided different direction of optic axis angle when combination of first polaroid 2, electrooptic modulator 3, quarter wave plate 14 and second polaroid 15, the corresponding relation of each element in direct current, 1 order harmonics and 2 order harmonic component that first photomultiplier 16 is measured and the stokes scattering matrix:

Table 1

In the table 1, γ ₂The optical axis direction of first polaroid 2 is with respect to the orientation angles of reference planes, γ in the indication device ₃The direction of optic axis angle of expression electrooptic modulator 3, γ ₉The direction of optic axis angle of expression quarter wave plate 14, γ ₁₀The direction of optic axis angle of representing second polaroid 15; The optical axis direction of first polaroid, electrooptic modulator, quarter wave plate and second polaroid is respectively: (a) " 0 ° ,-45 °,--,--"; (b) " 0 ° ,-45 °,--, 0 ° "; (c) " 0 ° ,-45 °,--, 45 ° "; (d) " 0 ° ,-45 °, 0 °, 45 ° "; (e) " 45 °, 0 °,--,--"; (f) " 45 °, 0 °,--, 0 ° "; (g) " 45 °, 0 °,--, 45 ° "; (h) " 45 °, 0 °, 0 °, 45 ° ", wherein symbol "--" represent this device need not, under above-mentioned these 8 combination conditions, measure direct current, an order harmonics and the distribution of the second harmonic component on semi-circumference of scattered light signal respectively; Thereby all 16 elements in the stokes scattering matrix of acquisition smoke particle light scattering.

Directly gather with the harmonic component of pivoted arm 17 in the scattered light signal that first photomultiplier 16 that smoke particle scattering luminous point rotates is measured, and its DC component can connect the ADC input end of lock-in amplifier and gathers by lock-in amplifier 21.In addition, owing to can't guarantee in the smoke particle light scattering measurement process that smoke particle stream is invariable fully, here adopt second photomultiplier 10 real-time follow-up on a certain fixedly scattering angle to gather scattered light intensity on this angle, this intensity variations has promptly reflected the variation of smoke particle stream, thereby the signal that available this light intensity curve is measured for first photomultiplier 16 carries out normalizing, thereby eliminate the unstable influence that brings of smoke particle stream, improve the precision of measuring.Scattered light signal for second photomultiplier 10 receives only needs to measure its light intensity, i.e. DC component, and the ADC input end that therefore also this DC component is connect lock-in amplifier carries out synchronous acquisition.

In order to realize 8 combinations shown in the table 1, the direction of optic axis angle of respective optical device must be able to be regulated in the device.Wherein, first polaroid 2 is relative constant with the direction of optic axis angle of electrooptic modulator 3, switch to combination 5～8 o'clock by combination 1～4, their direction of optic axis angle need be changed simultaneously 45 °, therefore, in apparatus of the present invention, first polaroid 2 is positioned in the cylinder with electrooptic modulator 3, this cylinder can be axle rotation with the center line of himself, by rotating this cylinder, thereby regulates the optical axis direction of first polaroid 2 and electrooptic modulator 3.By table 1 as seen, for the quarter wave plate 14 and second polaroid 15, must be the state of " sky " in some combination, need this moment the respective optical device is removed.Wherein, quarter wave plate 14 need switch between the state of " 0 ° " and " sky ".As shown in Figure 1, in apparatus of the present invention, realize that by moving of pull bar quarter wave plate switches between these 2 states, being about to terminal back that quarter wave plate is installed on pull bar, to regulate its optical axis direction be 0 °, when quarter wave plate being moved to collimating eyelet 13 aligned positions by pull bar, be 0 ° of state promptly to optical axis direction that should quarter wave plate, and when quarter wave plate removed, scattered light is without quarter wave plate at this moment, and promptly corresponding quarter wave plate is the state of " sky ".Similarly, second polaroid 15 need be at " 45 ° ", " 0 ° " reaches between the state of " sky " and switches, also adopt the mode of pull bar to realize, here adopt 2 identical polaroids, it is installed on the pull bar, has a determining deviation between two polaroids, their direction of optic axis angle is transferred to " 45 ° " and " 0 ° " respectively, when a certain polaroid being pushed into the position of collimating eyelet 13 alignings by pull bar, promptly corresponding to the direction of optic axis angle state of this polaroid, and when 2 polaroids of collimating eyelet 13 alignings were middle, the scattered light that photomultiplier receives was without any polaroid, and this moment, corresponding polaroid was the state of " sky ".

In sum, whole measuring process is: under each combination condition of 4 optical device shown in the table 1, driving pivoted arm 17 by computing machine 20 control motors 18 rotates around smoke particle light scattering point 6, this pivoted arm suspends every certain angle step, direct current, 1 order harmonics and 2 order harmonic component that gather the smoke particle scattered light signal that by first photomultiplier 16 received by lock-in amplifier 21 this moment, the DC component of gathering the scattered light of second photomultiplier, 10 receptions simultaneously is a light intensity.For example, if the angle step that pivoted arm rotates is 0.9 °, be motor whenever walk 200 the step stop once, being 5 ° from initial angle begins to measure, then correspondingly, at 5.0 °, 5.9 °, 6.8 °, 7.7 ° ... gather each order component of the scattered light signal that receives by first photomultiplier 16 on these discrete angles, thereby obtain the angular distribution trend of smoke particle scattered light, simultaneously, utilize scattered light intensity that second photomultiplier 10 gathered receives variation tendency in time accordingly, the component of signal that is received by first photomultiplier 16 is carried out normalizing, the influence that the instability of elimination smoke particle stream is brought.Under 8 combination conditions as shown in table 1, the measurement on identical discrete angle can finally record in the stokes scattering matrix of smoke particle light scattering all 16 elements with the angular distribution curve.

Compare with the device that has the angular distribution curve of a plurality of photomultiplier measurement smoke particle scattered light signals of installation on semi-circumference now, apparatus of the present invention utilize electrooptic modulator that incident light is modulated, rotate around smoke particle scattering luminous point with pivoted arm by the single channel photomultiplier, utilize lock-in amplifier to measure the multistage component of scattered light signal, thereby record the angular distribution of all elements in the stokes scattering matrix of smoke particle with higher angular resolution, promoted the excavation of smoke particle light scattering information greatly.

Adopt the polarization direction level that is respectively to restraint the measurement that incident lasers carry out the smoke particle light scattering in the existing apparatus with vertical two, incident light is not modulated, and directly use the DC component of photomultiplier measurement scattered light signal, this device is merely able to measure the light intensity of scattered light and the angular distribution curve of linear polarization degree.And in apparatus of the present invention, incident laser is through after first polaroid 2, adopt electrooptic modulator 3 that it is modulated into the frequency with 1KHz, and quarter wave plate and polaroid are installed at first photomultiplier, 16 front ends of receiving scattered light, gather direct current, 1 order harmonics and 2 order harmonic component of the scattered light signal that photomultipliers receive by lock-in amplifier 21; During measurement, under each combination condition shown in the table 1, driving pivoted arm 17 by motor 18 rotates around the smoke particle scattering center, thereby measure the distribution of smoke particle scattered light signal on circumference, and can't guarantee invariable fully at actual smoke particle, thereby adopt on a certain fixedly scattering angle, measure on these fixed angles scattered light intensity variation tendency in time by second photomultiplier 10, be used for the normalizing of first photomultiplier, 16 measuring-signals is handled, thereby eliminate the unsettled influence of smoke particle.Like this, by the measurement under 8 combination conditions shown in the table 1, according to the relation between each element in 3 components of the smoke particle scattered light signal that provides in the table 1 and the stokes scattering matrix, can obtain 16 elements in the stokes scattering matrix of smoke particle light scattering, each element has all been described an information characteristics in the smoke particle light scattering process.Existing apparatus the light intensity of the smoke particle scattered light that can measure and linear polarization degree only be in 16 matrix elements wherein 2, i.e. F ₁₁(θ) and F ₂₁(θ).As seen, information characteristics abundant more in the smoke particle light scattering process can be measured and excavate to apparatus of the present invention, thereby for the design of novel photoelectric smoke fire detector provides more criterion, promote the fast development of photoelectric smoke Detection Techniques.The principle that photoelectric smoke is surveyed is to reach the purpose of the fire smoke particle being carried out early detection by the scattered light information that receives smoke particle, yet, because interference source particles such as dust, oil smoke and water vapor also can produce similar light scattering, thereby if only make the judgement of whether breaking out of fire simply by the intensity signal of measuring scattered light, false alarm takes place easily then.The existence of these interference source particles has also limited the further raising of photoelectric smoke detector response sensitivity to a great extent.In order to reduce the false alarm of the optical detector of fire smoke that various interference source particles cause, improve its response sensitivity simultaneously, must analyze the natural fire smoke particle and be different from the light scattering feature of various interference source particles, and only be difficult to accurately according to the light intensity of smoke particle scattered light and these 2 information of linear polarization degree and search out corresponding criterion reliably, thereby the necessary more information of further excavating in the smoke particle light scattering process, the active demand that apparatus of the present invention are tackled key problems at the fire hazard aerosol fog Detection Techniques just, all elements in the stokes scattering matrix of measurement smoke particle light scattering correspondence.

In the existing apparatus, by the angular distribution feature of a plurality of photomultiplier measurement smoke particle scattered lights is installed on semi-circumference, thereby although can be at the scattered light signal of installing compactly on the circumference on the photomultiplier measurement more perspective as much as possible, but these photoelectric devices have certain volume after all, thereby can only be with the angular distribution of scattered light signal on the bigger angle intervals measurement circumference, promptly the angular resolution of Ce Lianging is lower.For example, existing apparatus is that 14 photomultipliers are installed on 0.3 meter the semi-circumference at diameter, this moment, device was crowded, on semi-circumference, can only measure the scattered light signal of 14 discrete angle correspondences, the angular resolution of measuring only is 12 °, can only obtain the angular distribution feature of scattered light so roughly.And in apparatus of the present invention, rotate around smoke particle scattering luminous point by the motor driven pivoted arm, by the angular distribution of the photomultiplier measurement scattered light on the pivoted arm.Thereby this mode of rotating measurement scattered light angular distribution by the single channel photomultiplier around the smoke particle scattering center, can realize very high angular resolution, the rotation of pivoted arm is passed through motor driven by computer program, motor is whenever walked corresponding pivoted arm of 200 steps and is rotated 0.9 °, computing machine sends a pulse to motor, then motor makes a move, and promptly pivoted arm rotates 0.0045 °; In addition, the diameter length of collimating eyelet 13 has only 1 millimeter, only is 0.225 ° with respect to the angle of smoke particle scattering center.As seen, apparatus of the present invention can be with very little angle intervals, measure the angle character of smoke particle scattered light meticulously, for example, this angle intervals can be made as 0.45 °, be that motor whenever walked for 100 steps, the data that first photomultiplier 16 is measured on the scattering angle, the angular resolution of measurement is higher than existing apparatus far away.Therefore, can measure the detailed angular distribution curve of each parameter of smoke particle light scattering by apparatus of the present invention, this curve has reflected the distribution characteristics of scattering parameters on different angles more concrete, full and accurately, more help seeking the light scattering feature that smoke particle is different from all the other interference source particles, for the false alarm that reduces photoelectric smoke detector provides criterion, and further improve the response sensitivity of detector, promote the development of photoelectric smoke Detection Techniques.

For the angular distribution pattern measurement of smoke particle scattered light, directly influence its measuring accuracy for the collimation of scattering center at the photomultiplier of all angles.In the existing apparatus, preamble is mentioned, for the scattered light signal on the discrete angle that records on the circumference as much as possible, on circumference, adorn photomultiplier as much as possible, thereby crowded each other between each photomultiplier, can't the three-dimensional regulation parts be installed on each photomultiplier, like this, each photomultiplier can't carry out fine adjustments with respect to the collimation of smoke particle scattering center, and the precision of the scattered light signal angular distribution curve of this measurement device is relatively poor.And in apparatus of the present invention, utilize the rigidity pivoted arm to rotate around the smoke particle scattering center, angular distribution feature by the single channel photomultiplier measurement smoke particle scattered light on the pivoted arm, by on aerosol spraying head 7 with collimating eyelet 13 is housed, on the box 12 of first photomultiplier, 16 grades three- dimensional regulation parts 8 and 11 are installed respectively, thereby guarantee in the pivoted arm rotation process, collimating eyelet 13 is aimed at smoke particle scattering luminous point all the time, so promptly guaranteed on different scattering angles, photomultiplier has been guaranteed the precision of experiment measuring all the time with the scattered light of higher precision measure smoke particle.

In apparatus of the present invention, the adjusting of 1/4 slide 14 of described first photomultiplier, 16 front ends and the direction of optic axis angle of second polaroid 15, according to the various combination shown in the table 1, it is characterized in that earlier it being installed on the pull bar, and with its direction of optic axis angular adjustment to analog value, the mode of passing then by pull bar, thus every combination in the table 1 formed.

In apparatus of the present invention, adopting on collimating eyelet 9 and second photomultiplier, 10 these angles of measurement smoke particle scattered light intensity change curve in time on a certain fixedly scattering angle, be used to monitor whether smoke particle stream is stable, measured scattered light intensity curve over time is used for the scattered light signal that first photomultiplier 16 is measured is carried out normalized, thereby eliminate the instable influence of smoke particle stream, further improve measuring accuracy.

Claims (1)

1, a kind of fire smoke particle stokes scattering matrix measurement mechanism is included in that laser instrument (1) emitting laser bundle is incident to the smoke particle (6) of aerosol spraying head (7) ejection and first photomultiplier (16) of receiving scattered light signal is installed around the scattering luminous point that forms; It is characterized in that: be incident to smoke particle (6) before earlier through first polaroid (2) by laser instrument (1) emitting laser bundle, and modulating via electrooptic modulator (3); The center that is used to install the optical table (22) of optics and mechanical devices has hole (5), rotating disk (4) with perforate places the positive center of optical table (22), aerosol spraying head (7) is fixed on the center of optical table (22) by three-dimensional regulation parts (8), pivoted arm (17) is fixed on the rotating disk (4), motor (18) drives pivoted arm (17) and rotates around smoke particle (6), on the light path in first photomultiplier (16) the place ahead, be provided with second polaroid (15) successively, a quarter wave plate (14) and a collimating eyelet (13), these four device package also are installed on the pivoted arm (17) by another three-dimensional regulation parts (11) in box (12) lining, on a certain fixedly scattering angle of a semi-circumference of smoke particle light scattering, along the light path of scattered light another collimating eyelet (9) and second photomultiplier (10) are installed successively, the signal output part of described second photomultiplier (10) and first photomultiplier (16) connects the signal input part of lock-in amplifier (21), the parallel port output signal end of computing machine (20) is connected with the signal input part of motor (18), the serial ports of computing machine (20) is connected with the serial ports of lock-in amplifier (21), and the signal output part of signal generator (19) connects the signal input part of electrooptic modulator (3) and lock-in amplifier (21).

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