CN101526475B - Transmission-type visibility measuring device and measuring method - Google Patents

Abstract

The invention provides a transmission-type atmospheric visibility measuring device which has long-term reliability and can accurately measure visibility, and a measuring method. The transmission-type atmospheric visibility measuring device comprises a transmission part and a detection part, wherein the detection part comprises a receiving unit, a photoelectric signal processing unit, a data collecting unit and a computer control unit; the receiving unit adopts four-quadrant photodetectors; the light beam of each photodetector is provided with a photoelectric signal processing unit; signals output by the photoelectric processing unit is transmitted to the computer control unit through the data collecting unit; and the center coordinate of the four-quadrant photodetectors is controlled by a computer.

Description

Transmission-type visibility measuring device and measuring method

One, technical field

The present invention designs a kind of optical radiation reception and measurement mechanism, particularly a kind of transmission-type atmospheric visibility measurement mechanism, measurement of extinction coefficient and autotracker when belonging to optical radiation energy and propagating in atmosphere.

Two, background technology

Atmospheric visibility is producing important influence in lasercom, picture transmission and Modern Transportation Technology.Visibility measurement also is subjected to people's attention always, along with the development of Modern Traffic networks development, particularly highway, water transport and aircraft industry, need monitor in real time atmospheric visibility, and it is important that the measurement of visibility also more shows.The measurement of visibility depends on the measurement of light beam extinction coefficient.Typical measuring method has forward scattering method and transmission beam method two classes.The forward scattering method is selected the faint near infrared light of Atmospheric Absorption, becoming 35 ° of directions with the detecting light beam direction of propagation, the measured angular scattering coefficient, again by certain atmospheric optics mode computation total scattering coefficient, and determine visibility according to the Koschmieder law, the measuring error of this method is decided by the measurement of total scattering coefficient.In existing forward scattering subtraction unit, as follows: the background interference that the influence of the influence of optical mode, scatter sounding beam divergence angle, background radiation interference and scattered radiation produce and the influence of proving installation structure thermal deformation etc. to the main determining factor of total scattering coefficient measuring error.These devices are when measuring the scattering coefficient at 35 ° of scattering angle places, the incident beam that light-receiving member is collected not is the parallel beam under the strict difinition, but being distributed in the interior light beam of big cone angle, the scattering coefficient that obtains thus is bigger than the scattering coefficient of this actual direction.Though transmission beam method is the most a kind of method, but different place because the emission of light beam and measurement are separated by, and it is far away at interval, because of reasons such as the vibration of atmospheric disturbance or measurement mechanism, landform variation cause hot spot to drift about on the photodetector receiving plane, it is inaccurate to make the attenuation coefficient of detecting light beam on travel path measure, even causes measuring failure.

Three, summary of the invention

The object of the present invention is to provide a kind of long-term reliability height, can accurately measure the transmission-type atmospheric visibility measurement mechanism of visibility.

Another object of the present invention is to provide transmission-type atmospheric visibility measuring method, the luminous power sum that this method detects with the every quadrant of four-quadrant photo detector is represented the transmitted optical power of transmission-type atmospheric visibility detecting light beam, and measurement result is accurate.

The objective of the invention is to be achieved through the following technical solutions:

A kind of transmission-type atmospheric visibility measurement mechanism, it comprises radiating portion and probe portion, probe portion comprises receiving element, Photoelectric Signal Processing unit, data acquisition unit and computer control unit, described receiving element adopts four-quadrant photo detector, the light beam that each quadrant is surveyed is equipped with the Photoelectric Signal Processing unit, and the signal of each Photoelectric Signal Processing unit output is sent into computer control unit through data acquisition unit; Centre coordinate by computer control unit control 4 quadrant detector.

Four-quadrant photo detector is provided with and keeps its characterisitic parameter not with the conductor temperature control circuit of variation of ambient temperature.

The mounting seat of described four-quadrant photo detector is provided with X-axis and Y-axis translation stage, and X-axis is connected a stepper motor respectively with the Y-axis translation stage, and two stepper motors connect computer control unit respectively.

The Photoelectric Signal Processing unit comprises: prime amplifier, bandwidth-limited circuit and accurate effective value change-over circuit.Data acquisition unit adopts the multichannel synchronous sampling circuit.The light beam of four quadrants is sent into computer control unit by the multichannel synchronous sampling circuit again after Photoelectric Signal Processing cell processing separately.

Transmission-type atmospheric visibility measuring method, it is characterized in that: measuring process comprises:

(1) by semiconductor laser emission light pulse sequence, behind collimation, becomes directional light and send;

(2) convex lens through light receiving unit converge to the four-quadrant photo detector surface;

(3) signal of every quadrant detection is sent into computer control unit respectively by after the Photoelectric Signal Processing cell processing through data acquisition unit;

(4) computer control unit calculates the luminous power sum that every quadrant detects and obtains transmitted optical power; The simultaneous computer control module calculates the centre coordinate of hot spot on four-quadrant photo detector, and the X-axis and the Y-axis orientation of control step motor adjustment four-quadrant photo detector, and hot spot is carried out tracking Control.

Stepper motor comprises X-axis translation stepper motor and Y-axis translation stepper motor, and X-axis translation stage and Y-axis translation stage that two stepper motors are controlled four-quadrant photo detector respectively move.X-axis and Y-axis translation stage are arranged on the mounting seat of four-quadrant photo detector.

The present invention has following advantage compared to existing technology:

The present invention adopts the automatic tracking technique of four-quadrant detecting light beam, follows the tracks of detecting light beam and measurement detecting light beam power or intensity and uses same detector, and the assurance detector is accurately aimed at detecting light beam, can effectively suppress the influence that the detecting light beam drift produces.Guarantee that the position of hot spot on the detector receiving plane is constant substantially, solved the influence problem of the spot drift of existence for many years, can measure described attenuation coefficient comparatively exactly visibility measurement.Another remarkable advantage is, detector is taked the temperature control measure, suppressed the influence of environment temperature, improved long-term reliability.Laser instrument is adopted temperature control technology, make the output wavelength stabilized laser, avoid surveying of the influence of optical wavelength shakiness measuring.

The luminous power sum that method of the present invention detects with the every quadrant of four-quadrant photo detector is represented the transmitted optical power of transmission-type atmospheric visibility detecting light beam, advantage is to utilize the monochromatic light road to realize simultaneously measuring and following the tracks of, thereby light path system is simple, test macro long-term reliability height.

Four, description of drawings

Fig. 1 is the structured flowchart of transmission-type visibility measuring instrument;

Fig. 2 is the radiating portion assembly structure synoptic diagram of embodiment;

Fig. 3 is the probe portion assembly structure synoptic diagram of embodiment;

Fig. 4 four-quadrant optical signal processing system of the present invention schematic diagram;

The theory diagram that Fig. 5 surveys for four-quadrant of the present invention.

Among the figure: the a-mounting base; The b-pillar; C-launches assembly; The d-laser beam; The e-detection assembly; The f-pillar; The g-controller case; The h-mounting base.

The 1-laser drive power; The 2-semiconductor laser; The 3-collimating apparatus; The 4-detecting light beam; The 5-convex lens; The 6-four-quadrant photo detector; 7-is the metallic cylinder of convex lens fixedly; The 8-installation base plate; 9-X axle translation stage; 10-X axle translation stepper motor; 11-Y axle translation stage; 12-Y axle translation stepper motor; The 13-data acquisition unit; The 14-stepper motor driving circuit; The 15-stepper motor driving circuit; The 16-computer control unit; The 17-data transmission interface; 18-conductor temperature control circuit.

The 21-24 prime amplifier; The 31-34 bandpass filter; 41-44 multiplier and π type filtering combination.

Five, embodiment

As Fig. 1, Fig. 2, shown in Figure 3, transmission-type atmospheric visibility measurement mechanism of the present invention, it comprises radiating portion and probe portion, probe portion comprises receiving element, the Photoelectric Signal Processing unit, data acquisition unit 13 and computer control unit 16, receiving element adopts four-quadrant photo detector 6, promptly divide four the tunnel to sample to the light beam after assembling, divide from the orientation by four quadrants, and divide four tunnel outputs with the light beam of surveying, the light beam of each road output is imported Photoelectric Signal Processing unit separately respectively, sends into computer control unit 16 through the signal of each Photoelectric Signal Processing unit output through data acquisition unit and handles; Centre coordinate by four quadrant photodetectors 6 of computer control unit 16 controls.

The Photoelectric Signal Processing unit comprises: prime amplifier 21,22,23,24, bandwidth-limited circuit 31,32,33,34 and accurate multiplier and π type filtering combination 41,42,43,44.Data acquisition unit 13 comprises multichannel synchronous sampling circuit and A/D converter.

Radiating portion comprises semiconductor laser 2, laser drive power 1.Laser drive power 1 is provided with laser temperature control circuit, luminous power modulation circuit and light power stabilising circuit, guarantees that laser instrument sends optical wavelength and power does not change with the variation of environment, and effectively suppresses the influence of surround lighting variation to measuring.

Receiving element comprises laser beam datum system, laser pick-off probe.Wherein semiconductor laser 2 is connected with laser drive power 1, laser beam datum device 3 is made of the anaberration optical lens group, collimating apparatus 3 places laser output, propagate certain distance through collimation back laser beam and arrive the laser pick-off probe, receiving transducer is by the fixedly metallic cylinder 7 and convex lens 5 of convex lens, the installation base plate 8 of four-quadrant photo detector 6 and band conductor temperature control circuit is formed, convex lens 5 are positioned at the front end of receiving transducer, laser beam is focused on the four-quadrant photo detector 6 through convex lens 5, and four-quadrant photo detector 6 is positioned at the receiving transducer rear end; Four-quadrant photo detector 6 is installed on the substrate 8 that is provided with the conductor temperature controller, and the light transfer characteristic parameter that guarantees four-quadrant photo detector 6 is not with variation of ambient temperature.The conductor temperature control circuit 18 of four-quadrant photo detector is connected with computer control unit 16.

Four-quadrant photo detector 6 is divided into four probe units with detecting light beam, and each probe unit is connected with the prime amplifier 21,22,23,24 of separately Photoelectric Signal Processing unit respectively.

The installation base plate 8 of four-quadrant photo detector 6 is arranged on X-axis and the Y-axis translation stage, be that X-axis translation stage 9 and Y-axis translation stage 11 are as tracking unit, X-axis is connected a stepper motor respectively with the Y-axis translation stage, i.e. X-axis translation stepper motor 10 and Y-axis translation stepper motor 12.Two stepper motors are respectively equipped with stepper motor driving circuit, and control moving along X-axis and Y-axis of two stepper motors by computer control unit 16, thereby the tracking Control to hot spot is finished in the adjustment of the centre coordinate of control four-quadrant photo detector 6.

The course of work of the present invention:

As Fig. 4, shown in Figure 5, semiconductor laser 2 of the present invention is launched frequency 1.0kHz light pulse sequence under the driving of driving power, behind beam collimation device 3, become parallel beam, after propagating the distance of regulation, arrive the convex lens 5 that the light-receiving list does not have, converge to the surface of four-quadrant photo detector 6, four-quadrant photo detector 6 is divided into four parts with light beam, an i.e. quadrant, two quadrant, three quadrants, four-quadrant.Each quadrant is a photodetection unit, the light signal that receives is converted to electric signal, the photosignal of all quadrants probe unit output is through separately prime amplifier 21,22,23,24, bandpass filter 31,32,33,34 and multiplier and the filtering of π type combination 41,42,43,44 are converted into d. c. voltage signal, its size is directly proportional with the luminous power that probe unit separately receives, computer control unit 12 obtains the average power of each road light signal of four-quadrant photo detector respectively by multichannel synchronous sampling circuit 11 and A/D converter, according to the emission luminous power, by following formula (7), (4) and (1) or (2) or (3) calculate visibility; Calculate the coordinate of spot center on four-quadrant photo detector 6 by formula (8) and formula (9), 13,14 work of control step motor driver, X-axis translation stepper motor 7 and Y-axis translation stepper motor 9, X-axis translation stage 8 and Y-axis translation stage 10 are moved, adjust the orientation of four-quadrant photo detector 6, realize two dimension control.

Principle of work of the present invention:

Represent visibility with meteorological range, press the regulation of ground observation standard, when distant object thing-background contrasts drop to contrast nearby 0.02 the time, pairing distance definition is a visibility, it is provided by the Koschmieder law

$R_m=\frac{3.912}{{\mathrm{\κ}}_{\mathrm{ex}}}---\left(1\right)$

κ wherein _ExBe that atmosphere is the monochromatic extinction coefficient of 550nm to wavelength.With the monochromatic light of other wavelength X as surveying the light time, formula (1) should be rewritten as

$R_m=\frac{3.912}{{\mathrm{\&kappa;}}_{\mathrm{ex}}}{\left(\frac{0.55}{\mathrm{\&lambda;}}\right)}^{0.583{\mathrm{<figure-callout\; id="1"\; label="R\; m"\; filenames="H2009100293586E00021.png"\; state="\{\{state\}\}">R</figure-callout>}}_m^{}}---\left(2\right)$

Formula (2) is a transcendental equation, can only obtain numerical solution.The measuring accuracy of visibility depends on κ _ExWith the measuring accuracy of wavelength, high many of the measuring accuracy of the measuring accuracy specific extinction coefficient of actual measurement medium wavelength.

At aviation field, in order to guarantee the safety of aircraft, objective definition thing-background contrasts drops to 0.05 o'clock of contrast nearby, and pairing distance is a visibility

$R_m=\frac{2.996}{{\mathrm{\&kappa;}}_{\mathrm{ex}}}---\left(3\right)$

The collimated laser beam of determining with wavelength is as detecting light beam, measures the transmitance τ behind its transmission certain distance, determines that according to Lambert-Beer's law detecting light beam passes the extinction coefficient κ of regional atmospheric _ExThe laser power of surveying optical transmitting set output is I ₀, the luminous power that optical receiver receives is I _R, extinction coefficient to be measured is

${\mathrm{\&kappa;}}_{\mathrm{ex}}=\ln \left(\frac{I_0}{I_R}\right)---\left(4\right)$

Receive detecting light beam with four-quadrant photo detector in the present invention, detecting light beam is about 1/2nd of diameter detector through the spot diameter that is incident upon on the four-quadrant photo detector face behind the collector lens, corresponding each quadrant is provided with a Photoelectric Signal Processing unit channel, the preposition amplification that each quadrant connected, the performance parameter of Photoelectric Signal Processing unit are the same, as shown in Figure 4.Four d. c. voltage signal u that passage is exported separately _iWith this passage respective quadrants luminous power I _RiBe directly proportional,

u _i＝ξ _iI _Ri (5)

Because each electronic circuit channel performance parameter is identical, i.e. ξ ₁=ξ ₂=ξ ₃=ξ ₄=ξ, computer system is sampled to four tunnel signal Synchronization, and the gained voltage signal sued for peace

$u=\mathrm{\&xi;}\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{I}_{\mathrm{Ri}},---\left(6\right)$

The total optical power that arrives optical receiver is

$I_R=\frac{1}{{\mathrm{\&tau;}}_1\&CenterDot;\mathrm{\&zeta;}}\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{I}_{\mathrm{Ri}}=\frac{u}{{\mathrm{\&tau;}}_1\&CenterDot;\mathrm{\&zeta;}\&CenterDot;\mathrm{\&xi;}}---\left(7\right)$

τ wherein ₁The transmitance of optical receiver collector lens, ζ is that the four-quadrant photo detector division line is to being transmitted to four-quadrant photo detector surface facula area efficiency factor.Measure emission luminous power and received optical power, utilize formula (7), (4) and (1) or (2) or (3) to calculate visibility.

The luminous power of four passages of four-quadrant photo detector that another importance of the present invention is a computer control unit to be obtained according to the multichannel synchronized sampling is calculated as follows the position coordinates of spot center on detector

$X=\frac{\mathrm{\&alpha;}[({\mathrm{<figure-callout\; id="1"\; label="I\; R"\; filenames="H2009100293586E00021.png"\; state="\{\{state\}\}">I</figure-callout>}}_R+I_{R4})-({\mathrm{<figure-callout\; id="2"\; label="I\; R"\; filenames="H2009100293586E00012.png"\; state="\{\{state\}\}">I</figure-callout>}}_R+I_{R3})]}{I_{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009100293586E00021.png"\; state="\{\{state\}\}">R</figure-callout>}1}+I_{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009100293586E00012.png"\; state="\{\{state\}\}">R</figure-callout>}2}+I_{R3}+I_{R4}}---\left(8\right)$

$Y=\frac{\mathrm{\&alpha;}[({\mathrm{<figure-callout\; id="1"\; label="I\; R"\; filenames="H2009100293586E00021.png"\; state="\{\{state\}\}">I</figure-callout>}}_R+I_{R2})-(I_{R3}+I_{R4})]}{I_{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009100293586E00021.png"\; state="\{\{state\}\}">R</figure-callout>}1}+I_{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009100293586E00012.png"\; state="\{\{state\}\}">R</figure-callout>}2}+I_{R3}+I_{R4}}---\left(9\right)$

Wherein α is the luminous power of detector reception and the conversion coefficient between the spot center coordinate.Computer control unit moves the two-dimension translational platform according to the work of coordinate figure size control step motor driver, almost overlaps with four-quadrant photo detector division line intersection point until spot center, realizes the automatic aligning tracking of detector to light beam.

Claims (8)

1. transmission-type atmospheric visibility measurement mechanism, it comprises radiating portion and probe portion, probe portion comprises receiving element, Photoelectric Signal Processing unit, data acquisition unit and computer control unit, it is characterized in that: described receiving element adopts four-quadrant photo detector, the light beam that each quadrant is surveyed is equipped with the Photoelectric Signal Processing unit, the signal of each Photoelectric Signal Processing unit output is sent into computer control unit through data acquisition unit, by the centre coordinate of computer control unit control hot spot on four-quadrant photo detector.

2. transmission-type atmospheric visibility measurement mechanism according to claim 1 is characterized in that: four-quadrant photo detector is provided with and keeps its light transfer characteristic parameter not with the conductor temperature control circuit of variation of ambient temperature.

3. transmission-type atmospheric visibility measurement mechanism according to claim 1, it is characterized in that: the mounting seat of described four-quadrant photo detector is provided with X-axis and Y-axis translation stage, X-axis is connected a stepper motor respectively with the Y-axis translation stage, and two stepper motors connect computer control unit respectively.

4. transmission-type atmospheric visibility measurement mechanism according to claim 1 is characterized in that: described Photoelectric Signal Processing unit comprises: prime amplifier, bandwidth-limited circuit and effective value change-over circuit.

5. transmission-type atmospheric visibility measurement mechanism according to claim 1 is characterized in that: data acquisition unit adopts the multichannel synchronous sampling circuit.

6. transmission-type atmospheric visibility measuring method, it is characterized in that: measuring process comprises:

(1) by semiconductor laser emission light pulse sequence, behind collimation, becomes directional light and send;

(2) convex lens through light receiving unit converge to the four-quadrant photo detector surface;

(3) signal of every quadrant detection is sent into computer control unit respectively by after the Photoelectric Signal Processing cell processing through data acquisition unit;

(4) computer control unit calculates the luminous power sum that every quadrant detects and obtains transmitted optical power; The simultaneous computer control module calculates the centre coordinate of hot spot on four-quadrant photo detector, and the X-axis and the Y-axis orientation of control step motor adjustment four-quadrant photo detector, and hot spot is carried out tracking Control.

7. transmission-type atmospheric visibility measuring method according to claim 6, it is characterized in that: described stepper motor comprises X-axis translation stepper motor and Y-axis translation stepper motor, and X-axis translation stage and Y-axis translation stage that two stepper motors are controlled four-quadrant photo detector respectively move.

8. transmission-type atmospheric visibility measuring method according to claim 7 is characterized in that: described X-axis and Y-axis translation stage are arranged on the mounting seat of four-quadrant photo detector.

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