CN202734971U - Optical measuring instrument for measuring atmospheric coherent length - Google Patents

Abstract

The utility model discloses an optical measuring instrument for measuring atmospheric coherent lengths, which comprises a helium neon laser emission unit (1), a laser receiving and photoelectric converting unit (2), a data acquiring unit (3) and a data processing and analyzing unit (4). The laser emission unit (1) comprises a helium neon laser (11) emitting laser beams and a beam expanding device (12). Laser beams emitted by the helium neon laser (11) are expanded by the beam expanding device (12). The laser beams are then transmitted by atmospheric turbulent flows before vertically entering the laser receiving and photoelectric converting unit (2). The optical measuring instrument can well overcome the influence of the atmospheric turbulent flow internal and external dimensions on the measuring methods and make the measuring result more reasonable. An applied position sensing detector can make position signals and relative light intensity signals directly shown. The internal memory is saved. Meanwhile, the requirements for a computer are lowered.

Description

A kind of optical gauge of atmospheric coherence length

Technical field

The utility model belongs to a kind of optical gauge, specifically a kind of instrument of measuring atmospheric coherence length on the light transmission path near the ground.It is applicable to atmospheric science research, and the field such as uranology, atmospheric optics, military affairs.

Background technology

Because the impact of atmospheric turbulence when light is propagated, can produce light intensity fluctuation and phase fluctuation in atmosphere.For imaging system, this can cause image blur, rises and falls before the light wave that atmospheric turbulence causes in uranology to make the true resolution and the atmospheric coherence length that receive optical telescope closely related.Along with extraterrestrial target monitoring, adaptive optics, the development of the Modern Optics Technology such as laser communication, the requirement that has proposed to obtain atmospheric coherence length on the light transmission path.Mainly contain at present two kinds of methods of measuring atmospheric coherence length, a kind of is to utilize merely arrival angle fluctuation to measure the instrument of atmospheric coherence length on the transmission path, this instrument is subjected to the impact of environment for use larger, relevant with the turbulent characteristics yardstick of environment of living in, require ambient stable (as indoor), the own non-jitters of transmitting illuminant etc., this will inevitably limit its usable range.The method that the second is measured atmospheric coherence length is DIMM (different image motion monitor), also is the measuring method of current comparatively main flow.The method is to utilize the distance variance of light source imaging facula barycenter on two positions not far from one another to come the value of inverting atmospheric coherence length, it is advantageous that and avoided the measuring error that factors such as utilizing only to become mechanical vibration when one arrival angle fluctuation of its barycenter of picture measurement comes inverting atmospheric coherence length value separately, light source shake itself causes, but when practical application, image device is often selected the photovoltaic such as CCD or ICCD, the use of these devices has increased cost, simultaneously also so that measure and be restricted.Lower such as sampling rate, as must to cause having lost atmospheric turbulence high frequency characteristics has also lengthened the sampling time, has reduced real-time requiring hits to satisfy under the prerequisite of statistical law.And this class device normally processes whole imaging picture, need to take a large amount of memory sources, is unfavorable for the integrated and real-time measurement of engineering.

The utility model content

The purpose of this utility model is that a kind of horizontal atmospheric coherence length measuring instrument and measuring method that adopts Position-Sensitive Detector is provided.This measuring instrument adopts helium-neon laser as transmitting illuminant, the corrugated that pinhole diaphragm is chosen distortion is imaged on the Position-Sensitive Detector, its position coordinates signal and relative light intensity signal are converted to digital signal by A/D converter, through acquisition process and analysis, obtain the value of atmospheric coherence length.This atmospheric coherence length measuring instrument not only can obtain the value of atmospheric coherence length in real time, and it is high to have measuring accuracy, and the advantage that uncertainty of measurement is little has also reduced the method error that brings under the different turbulent characteristics yardstick conditions simultaneously.

In order to achieve the above object, the utility model adopts following technical scheme:

A kind of optical gauge of atmospheric coherence length comprises He-Ne Lasers transmitter unit (1), laser pick-off and photoelectric conversion unit (2), data acquisition unit (3), and data are processed and analytic unit (4);

Laser emission element (1) comprises helium-neon laser (11) and the parallel beam expand device (12) of Emission Lasers, the laser beam of helium-neon laser (11) emission after parallel beam expand device (12) expands by the atmospheric turbulence transmission vertical incidence to laser pick-off and photoelectric conversion unit (2);

Laser pick-off and photoelectric conversion unit (2) comprise attenuator (21), aperture (22), optical filter (23) successively along light path, the first catoptron (24), the second catoptron (25) and Position-Sensitive Detector (27); The light beam that is incident to laser pick-off and photoelectric conversion unit (2) passes through attenuator (21), aperture (22), optical filter (23), the first catoptron (24), the rear in-position sensing detector (27) of the second catoptron (25) successively; Wherein fix from aperture (22) to the position of the first catoptron (24), fix from the first catoptron (24) to the second catoptron (25) position, distance from the second catoptron (25) to Position-Sensitive Detector (27) is provided by scale (26), Position-Sensitive Detector (27) carries out relative light intensity signal, position signalling that opto-electronic conversion obtains light beam totally 3 tunnel simulating signals, and with this 3 road analog signal output to data acquisition unit (3);

Data acquisition unit (3) comprises A/D converter (31) and data collecting card (32), A/D converter (31) is that digital signal is sent to data collecting card (32) with 3 tunnel analog signal conversion, and data collecting card (32) exports data to and processes and analytic unit (4);

Provide the atmospheric coherence length on the light transmission path behind the Data Management Analysis that data are processed and analytic unit (4) will obtain from data collecting card.

The optical gauge of described atmospheric coherence length, described attenuator (21) adopts the absorption-type neutral filter.

The optical gauge of described atmospheric coherence length, described aperture (22) adopts circular pin hole.

The optical gauge of described atmospheric coherence length, described optical filter (23) adopts spike interference filter.

The optical gauge of described atmospheric coherence length, described the first catoptron (24), the second catoptron (25) are the completely reflecting mirror of plated film.

The optical gauge of described atmospheric coherence length, described scale (26) is precision displacement table.

The optical gauge of described atmospheric coherence length, described Position-Sensitive Detector (27) adopts position sensitive photomultiplier tube.

Measure atmospheric coherence length r ₀Method, when a branch of plane wave after local uniformity isotropy atmospheric turbulence transmission, in the geometric approximation condition Lower, there is following relational expression to set up

$<{\mathrm{\&alpha;}}^2>=3.28{\mathrm{<figure-callout\; id="2"\; label="C\; n"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">C</figure-callout>}}_n^{}{\mathrm{Ll}}_0^{-1/3}---\left(1\right)$

${\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">I</figure-callout>}}^2=12.8C_n^2{L}^3{l}_0^{-7/3}---\left(2\right)$

Wherein L is beam Propagation path, l ₀Be yardstick, C in the atmospheric turbulence _n ²For the air index textural constant,＜α ²Be arrival angle fluctuation all the side, Be the light intensity scintillation index, it is defined as

$\mathrm{\&alpha;}=\frac{\sqrt{{(x-x_0)}^2+{(y-y_0)}^2}}{d}---\left(3\right)$

${\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">I</figure-callout>}}^2=\frac{<{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">I</figure-callout>}}^2>-{<I>}^2}{{<I>}^2}---\left(4\right)$

Wherein d be pin hole to the distance of Position-Sensitive Detector,＜... expression statistical average.

When measuring the atmospheric coherence length of light transmission path, it is generally acknowledged along the atmospheric turbulence on the beam Propagation path it is uniformly approximate, according to the integral relation of atmospheric coherence length and air index textural constant, to being L at horizontal light path, wavelength is the plane wave of λ, r ₀With the air index textural constant

The pass be:

$r_0{=\left\{\frac{2.91}{6.88}{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">k</figure-callout>}}^2{\&Integral;}_0^L{C_n}^2\left(L\right)\mathrm{dL}\right\}}^{-3/5}---\left(5\right)$

K=2 π/λ wherein.

The value that can provide atmospheric coherence length is

$r_0=0.3287{\mathrm{\&lambda;}}^{6/5}{L}^{-1/5}{<{\mathrm{\&alpha;}}^2>}^{-7/10}{\left({\mathrm{\&sigma;}}_I^2\right)}^{1/10}---\left(6\right)$

Can find out from above-mentioned relation, arrival angle fluctuation and light intensity flicker by measuring light beam after the atmospheric turbulence transmission can obtain atmospheric coherence length r ₀Value.

Advantage of the present utility model and effect are:

1 the multiplex CCD of instrument or ICCD owing to existing measurement, this method needs a large amount of reading images gray-scale values, will inevitably affect computing velocity.And the Position-Sensitive Detector that uses in the utility model can directly provide position signalling and relative light intensity signal, has saved internal memory, has reduced simultaneously the requirement to computing machine.

2 use the utility model can well overcome the interior external measurement of atmospheric turbulence to the impact of measuring method, make measurement result more reasonable.

Description of drawings

Fig. 1 is the structural representation of the atmospheric coherence length measuring instrument of employing Position-Sensitive Detector.

Wherein: 1 is that laser emission element, 2 is that laser pick-off and photoelectric conversion unit, 3 are that data acquisition unit, 4 is that data are processed and analytic unit;

11 is helium-neon laser, and 12 is parallel beam expand device; 21 is attenuator, and 22 is aperture, and 23 is optical filter, 24 first catoptrons, 25 second catoptrons, and 26 is scale, 27 is Position-Sensitive Detector; 31 is A/D converter, and 32 is data collecting card; 41 is PC.

Fig. 2 is that data are processed and the analytic unit workflow diagram.

Fig. 3 is the situation of change of the utility model atmospheric coherence length under different wind speed condition of different temperatures.

Embodiment

Below in conjunction with specific embodiment, the utility model is elaborated.

With reference to figure 1, the atmospheric coherence length measuring instrument comprises laser emission element 1, laser pick-off and photoelectric conversion unit 2, data acquisition unit 3, data processing and analytic unit 4; Laser emission element 1 comprises helium-neon laser 11 and the parallel beam expand device 12 of Emission Lasers, the laser beam of helium-neon laser 11 emission after parallel beam expand device 12 expands by the turbulent atmosphere transmission vertical incidence to laser pick-off and photoelectric conversion unit 2; Laser pick-off and photoelectric conversion unit 2 comprise attenuator 21, aperture 22, optical filter 23, the first catoptron 24, the second catoptron 25 and Position-Sensitive Detector 27 successively along light path; The light beam that is incident to laser pick-off and photoelectric conversion unit 2 passes through attenuator 21, aperture 22, optical filter 23, the first catoptrons 24, the second catoptron 25 rear in-position sensing detectors 27 successively.

Set up rectangular coordinate, the position of aperture 22 is (0,0), the position of optical filter 23 is (5,0), the position of the first catoptron 24 is (30,0), the position of the second catoptron 25 is (0,-25), the center position coordinates (31 of scale 26,-25), position (the x of Position-Sensitive Detector 27,-25), wherein, x is the displacement at relative scale 26 centers, fix from the position of aperture 22 to first catoptrons 24 wherein that (aperture 22 is 5cm apart from the position of optical filter 23, position apart from the first catoptron 24 is 30cm, the distance of the first catoptron 24 to second catoptrons 25 is 39cm, the second catoptron 25 is 31cm apart from scale centre distance, so total distance is 100cm, so, distance from aperture 22 to position sensing detector 27 is exactly 100 ± x, generally make x be in 0 state), from optical filter 23 to first catoptrons 24, the second mirror reflects mirror 25 omnidistance light paths are " Z " font, omnidistance optical path distance is 100cm, the first catoptron 24, the second catoptron 25 positions are fixed, and the distance from the second catoptron 25 to Position-Sensitive Detector 27 is provided by scale 26, Position-Sensitive Detector 27 carries out the relative light intensity signal that opto-electronic conversion obtains light beam, position signalling (x, the y both direction) totally 3 tunnel simulating signals, and with this 3 road analog signal output to data acquisition unit 3; Data acquisition unit 3 comprises four-way A/D converter 31 and data collecting card 32.A/D converter 31 is that digital signal is sent to data collecting card 32 with this 3 tunnel analog signal conversion, data collecting card 32 exports data to and processes and analytic unit 4, process and analytic unit 4 processing and analysis (seeing measuring principle and method) through data, obtain the value of atmospheric coherence length.

Wherein, the centre wavelength of helium-neon laser 11 outputs in the laser emission element is 632.8nm, output power 30mw, beam diameter 0.65mm, has volume little, lightweight, be convenient to integrated advantage, it is 10 that the parallel beam expand device 12 that configures expands multiple, and the light beam after this parallel beam expand device expands can be considered plane wave.

Helium neon laser beam is after atmospheric turbulence transfers to receive window, and through neutral filter 21 decay once, energy greatly reduces, and this has just been avoided damaging the possibility of Position-Sensitive Detector 27.By imaging in behind the aperture 22 on the photosurface of Position-Sensitive Detector, wherein spike interference filter 23 can reduce parasitic light to the impact of measured value, the ratio thereby raising property is made an uproar, and the effect of two catoptrons is to increase reduced volume on the basis of light path.The number reading method of scale is: aperture 22 to first catoptrons 24 apart from d ₁The+the first catoptron 24 to second catoptrons 25 apart from d ₂The distance of the+the second catoptron 25 to Position-Sensitive Detector apart from d ₃The reading d of ± scale indication ₀

For ease of calculating, first three items distance and can be designed to 1m, namely the value d that provides of scale is: d=1 ± d ₀

When measuring, sampling rate is set at first, sample number, transmission range L, and the parameter such as image-forming range d.Triggering collection signal immediately after setting completed, with sampling rate 300Hz, sample number 3000 is example, calculates the value of an air index textural constant in namely per 10 seconds.Behind the triggering collection signal, begin to gather the relative light intensity signal of hot spot, position signalling (x, y both direction) totally 3 tunnel.Every collection one frame is converted into digital signal and is saved in the internal memory, does statistical calculation one time after gathering full 3000 sample numbers, provides the value of an atmospheric coherence length of the light intensity fluctuation of these 3000 sample values and arrival angle fluctuation and these group data.

Measuring principle and method:

When a branch of plane wave after local uniformity isotropy atmospheric turbulence transmission, the geometric approximation condition (L＜＜l ₀ ²/ λ) under, have following relational expression to set up

$<{\mathrm{\&alpha;}}^2>=3.28C_n^{2}L{l}_0^{-1/3}---\left(1\right)$

${\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">I</figure-callout>}}^2=12.8C_n^2{L}^3{l}_0^{-7/3}---\left(2\right)$

Wherein L is beam Propagation path, l ₀Be yardstick, C in the atmospheric turbulence _n ²For the air index textural constant,＜α ²Be all side, σ of arrival angle fluctuation _I ²Be the light intensity fluctuation index, it is defined as

$\mathrm{\&alpha;}=\frac{\sqrt{{(x-x_0)}^2+{(y-y_0)}^2}}{d}---\left(3\right)$

${\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">I</figure-callout>}}^2=\frac{<{\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">I</figure-callout>}}^2>-{<I>}^2}{{<I>}^2}---\left(4\right)$

Wherein d be aperture 22 to the distance of Position-Sensitive Detector 27,＜... expression statistical average.

When measuring the atmospheric coherence length of light transmission path, it is generally acknowledged along the atmospheric turbulence on the beam Propagation path it is uniformly approximate, according to the integral relation of atmospheric coherence length and air index textural constant, to being L at horizontal light path, wavelength is the plane wave of λ, r ₀With the air index textural constant

The pass be:

$r_0={\left\{\frac{2.91}{6.88}{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="HSA00000697154900031.png"\; state="\{\{state\}\}">k</figure-callout>}}^2{\&Integral;}_0^L{C_n}^2\left(L\right)\mathrm{dL}\right\}}^{-3/5}---\left(5\right)$

K=2 π/λ wherein.

The value that can provide atmospheric coherence length is

$r_0=0.3287{\mathrm{\&lambda;}}^{6/5}{L}^{-1/5}{<{\mathrm{\&alpha;}}^2>}^{-7/10}{\left({\mathrm{\&sigma;}}_I^2\right)}^{1/10}---\left(6\right)$

Can find out from above-mentioned relation, by measuring arrival angle fluctuation and the light intensity fluctuation of light beam after the atmospheric turbulence transmission, can obtain atmospheric coherence length r ₀Value.

The model experiment result:

Fig. 3 is the situation of change of the air index textural constant of the utility model under the given different wind speed condition of different temperatures in laboratory, along the longitudinal axis from top to bottom wind speed be followed successively by 1.04m/s, 0.78m/s, 0.66m/s, 0.56m/s, 0.48m/s.

Should be understood that, for those of ordinary skills, can be improved according to the above description or conversion, and all these improvement and conversion all should belong to the protection domain of the utility model claims.

Claims (7)

1. the optical gauge of an atmospheric coherence length is characterized in that, comprises He-Ne Lasers transmitter unit (1), laser pick-off and photoelectric conversion unit (2), data acquisition unit (3), and data are processed and analytic unit (4);

Laser emission element (1) comprises helium-neon laser (11) and the parallel beam expand device (12) of Emission Lasers, the laser beam of helium-neon laser (11) emission after parallel beam expand device (12) expands by the atmospheric turbulence transmission vertical incidence to laser pick-off and photoelectric conversion unit (2);

Laser pick-off and photoelectric conversion unit (2) comprise attenuator (21), aperture (22), optical filter (23) successively along light path, the first catoptron (24), the second catoptron (25) and Position-Sensitive Detector (27); The light beam that is incident to laser pick-off and photoelectric conversion unit (2) passes through attenuator (21), aperture (22), optical filter (23), the first catoptron (24), the rear in-position sensing detector (27) of the second catoptron (25) successively; Wherein fix from aperture (22) to the position of the first catoptron (24), fix from the first catoptron (24) to the second catoptron (25) position, distance from the second catoptron (25) to Position-Sensitive Detector (27) is provided by scale (26), Position-Sensitive Detector (27) carries out relative light intensity signal, position signalling that opto-electronic conversion obtains light beam totally 3 tunnel simulating signals, and with this 3 road analog signal output to data acquisition unit (3);

Data acquisition unit (3) comprises A/D converter (31) and data collecting card (32), A/D converter (31) is that digital signal is sent to data collecting card (32) with 3 tunnel analog signal conversion, and data collecting card (32) exports data to and processes and analytic unit (4);

Provide the atmospheric coherence length on the light transmission path behind the Data Management Analysis that data are processed and analytic unit (4) will obtain from data collecting card.

2. the optical gauge of atmospheric coherence length according to claim 1 is characterized in that, described attenuator (21) adopts the absorption-type neutral filter.

3. the optical gauge of atmospheric coherence length according to claim 1 is characterized in that, described aperture (22) adopts circular pin hole.

4. the optical gauge of atmospheric coherence length according to claim 1 is characterized in that, described optical filter (23) adopts spike interference filter.

5. the optical gauge of atmospheric coherence length according to claim 1 is characterized in that, described the first catoptron (24), the second catoptron (25) are the completely reflecting mirror of plated film.

6. the optical gauge of atmospheric coherence length according to claim 1 is characterized in that, described scale (26) is precision displacement table.

7. the optical gauge of atmospheric coherence length according to claim 1 is characterized in that, described Position-Sensitive Detector (27) adopts position sensitive detector.

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