CN104776825A - Limited distance isoplanatie angle real-time measurement apparatus and method thereof - Google Patents

Abstract

The invention discloses a limited distance isoplanatie angle real-time measurement apparatus and a method thereof, and relates to the field of light wave atmosphere transmission. The method comprises the following steps: three circular sub-pupils (arranged on a three-hole surface cover) arranged at the front end of a telescope system receive dot signal light intensity, wedge mirrors are arranged on any two sub-pupils to divide incident light into three light beams corresponding to the three sub-pupils, and the three light beams pass through some optical elements and are finally received by a photoelectric detector; and received light spot intensity and mass center are obtained through computer processing, and statistics of the relative light intensity fluctuating covariance and the differential image motion variance of the two sub-holes is carried out to respectively obtain the limited distance isoplanatie angle and the spherical wave atmospheric coherence length. The method has the advantages of simplicity, easy implementation, real-time continuous measurement of the limited distance isoplanatie angle, and obtaining of the atmospheric coherence length, and is of great significance in the fields of adaptive optics, high resolution imaging, laser atmospheric transmission and the like.

Description

Dizzy angle real-time measurement apparatus and the methods such as a kind of limited distance

Technical field

The invention belongs to light wave propagation in atmosphere field, relate to the measurement of atmospheric optical turbulence parameter, be specially dizzy angle real-time measurement apparatus and the methods such as a kind of limited distance.

Background technology

When light wave transmits in an atmosphere, due to the impact of atmospheric optical turbulence (random fluctuation of air index), can distort in the corrugated of light wave, intensity can produce fluctuating.Angle anisoplanatism refers to the difference between the two-beam corrugated phase place of certain angle, and this phase difference is owing to producing through different atmospheric turbulence paths.Etc. dizzy angle, characterize the size of angle anisoplanatism, the phase distortion that atmospheric turbulence causes in this angular range can think substantially identical, surpass and go beyond the scope, angle anisoplanatic error is comparatively large, and adaptive optics corrects seriously influenced, and then affects laser engineering and high-resolution imaging.Etc. thus the Performance Evaluation of dizzy angle to ADAPTIVE OPTICS SYSTEMS is significant.

Etc. dizzy angle θ ₀expression formula:

${\mathrm{\θ}}_0{\left[2.91k^2{\∫}_0^L{C}_n^2\left(z\right)z^{5/3}\mathrm{dz}\right]}^{-3/5}$

Equation Chapter(Next)Section 1Equation Section 2(1)

The all square front phase error caused by angle anisoplanatism can be expressed as

${\mathrm{\σ}}_{\mathrm{\θ}}^2={\left(\frac{\mathrm{\θ}}{{\mathrm{\θ}}_0}\right)}^{5/3}---\left(2\right)$

For dizzy angles such as whole atmospheres, G.C.Loos in 1979, with C.B.Hogge (" Turbulence ofthe upper atmosphere and isoplanatism ", Appl.Opt.18,2654-2661 (1979)). find based on aperture is level and smooth theoretical, the dizzy angle such as the aperture of suitable size utilizes fixed star glimmer can to measure.It is theoretical that the method utilizes plane wave (star aberration can regard plane wave as) to glimmer, but the method applies on the dizzy angles such as limited distance and can produce gross error, main cause is that the beacon beam of limited distance is generally spherical wave, and can not regard plane wave as.

For dizzy angles such as limited distances, easy easy-to-use and measurement mechanism that is that can measure in real time have not been reported.Method feasible reluctantly utilizes turbulent flow Vertical Profile measuring instrument to obtain atmospheric turbulence profile at present, then draw according to above formula (1) integration.But as everyone knows, high-spatial and temporal resolution and high-precision turbulent flow profile measuring instrument are focus and the difficulties of research in atmospheric turbulence field always; Current turbulent flow profile measuring instrument complex structure, not easy to operate, and also spatial and temporal resolution is not high, and measuring accuracy is difficult to assessment.

Summary of the invention

The object of this invention is to provide a kind of device and method can measuring the dizzy angle such as limited distance in turbulent atmosphere in real time, deepen the understanding to atmospheric turbulence characteristic, thus necessary contribution is made to the engineer applied of Laser Atmospheric Transmission.

In order to achieve the above object, the technical solution adopted in the present invention is:

The dizzy angle such as limited distance real-time measurement apparatus, comprise receiving telescope, photoelectric detector and computing machine, attenuator, optical filter, imaging len, it is characterized in that: described receiving telescope front end is provided with three hole face shields, described three hole face shields are provided with three sub-pupils of circle, any two sub-pupils of circle are equipped with a point wedge mirror, the rear light path of described receiving telescope is provided with attenuator successively, optical filter, optical imaging lens, described imaging len be placed with photoelectric detector as in plane, the output terminal of described photoelectric detector is connected to computing machine.

The diameter of described three sub-pupils of circle is D, and the center distance between any one circular sub-pupil and two other circular sub-pupil is d ₁, d ₂, wherein meet d ₁=1.2D, d ₂=2.3D.

The span of the equal D of diameter of the sub-pupil of described circle is [0.8 (λ ₀l) ^0.5, 1.2 (λ ₀l) ^0.5], wherein λ ₀for a beacon beam effective wavelength, determined by the spectral characteristic of beacon used, optical filter, photodetector, L is surveyed turbulent flow limited distance, namely puts the distance between beacon and receiving telescope

Described attenuator is neutral filter, and described neutral filter should according to actual beacon brightness adjustment attenuation rate.Described attenuator is neutral filter, and described neutral filter should according to actual beacon brightness adjustment attenuation rate.Described optical filter should select filter range according to actual beacon beam spectral property, for laser beacon, should select the narrow band pass filter of corresponding optical maser wavelength.Described optical imaging lens should according to actual light battery detector needs, the selected focal length of lens.Described photodetector is ccd detector.

The dizzy angle method for real-time measurement such as a kind of limited distance, utilize three circle sub-pupil acceptance point beacon light intensity, and add up that spacing is respectively 0, d ₁, d ₂the relative light intensity fluctuating covariance C that receives of the sub-pupil of circle _r(0), C _r(d ₁), C _r(d ₂), three covariances to such as to be converted at the dizzy angle by recycling computing formula, it is characterized in that, comprise the following steps:

(1), calculate that spacing is respectively 0, d ₁, d ₂relative light intensity fluctuating covariance C _r(0), C _r(d ₁), C _r(d ₂).Relative light intensity fluctuating covariance C _rd the account form of () is:

$C_R\left(d\right)=\frac{C_I\left(d\right)}{<I_1><I_2>}=\frac{<[I_1-<I_1>][I_2-<I_2>]>}{<I_1><I_2>}---\left(3\right)$

Wherein, <> represents statistical average, I ₁, I ₂represent the light intensity gray-scale value that spacing is two sub-pupils of circle of d; (2), by C _rd () is converted to log-amplitude fluctuation covariance C _χ(d):

$C_{\mathrm{\&chi;}}\left(d\right)=\frac{\mathrm{In}(C_R\left(d\right)+1)}{4}---\left(4\right)$

(3), by corresponding C _χd () substitutes into following computing formula and draws the dizzy angles such as limited distance,

${\mathrm{\&theta;}}_0=L^{-1}{\left[2.233{\left(\frac{{\mathrm{\&lambda;}}_0}{\mathrm{\&lambda;}}\right)}^2\frac{29.88C_{\mathrm{\&chi;A}}\left(0\right)+81.66C_{\mathrm{\&chi;A}}\left(1.2D\right)+76.71C_{\mathrm{\&chi;A}}\left(2.3D\right)}{D^{5/3}}\right]}^{-3/5}---\left(5\right)$

Wherein L is the atmospheric turbulence limited distance measured, λ ₀for a beacon beam effective wavelength, for laser beacon, λ ₀for optical maser wavelength.

The present invention operationally, due to any two sub-pupils of circle being provided with a point wedge mirror light splitting, will inject the light beam in three holes separately; Utilize attenuator to regulate the light intensity injecting detector; Utilize optical filter to carry out Background suppression light, improve signal to noise ratio (S/N ratio); Utilize imaging len in the spacing regulating light spot received and size photodetector, most photodetector obtains three some source images (hot spot) be separated, photodetector is by access computing machine, and the data that computing machine is transmitted by correlation computations routine processes photodetector finally draw the dizzy angles such as limited distance.

Principle of the present invention and foundation are: the log-amplitude fluctuation covariance C of the limited distance point beacon that any two circular sub-pupil sub-aperture receive _χ(d) with etc. dizzy angle θ ₀the same, be the integration amount of hydraulic flow path; Etc. 5/3rds power z that the hydraulic flow path integration weight at dizzy angle is path ^5/3, and C _χd the path weight value of () is relevant with spacing d with the diameter D of two circular sub-pupils, and single C _χd the path weight value of () is without appointing how can not mate z ^5/3.(D ≈ (λ when experiment discovery meets certain condition ₀l) ^0.5, d ₁=1.2D, d ₂=2.3D), the C of three different spacing _χthe path weight value z at the dizzy angles such as the path weight value linear superposition energy energy approximate match of (d) ^5/3, thus the dizzy angles such as indirect inspection can be come by measuring three circle sub-pupil relative light intensity fluctuating covariances.In addition, we utilize in two sub-aperture, add the just in time contrary wedge mirror in angle of wedge direction, will inject the light beam in three holes separately, to form the hot spot of the separation of three on CCD target surface, are finally convenient to calculate relative light intensity fluctuating covariance.

Advantage of the present invention is:

The real-time measurement apparatus at the dizzy angle such as a kind of limited distance proposed by the invention and method, utilize the sub-pupils of three circles to receive measurement point beacons flicker associations to be correlated with the dizzy angles such as indirect inspection, open the new way of the dizzy angular measurements such as finite path, solve the dizzy angles such as limited distance can not real-time continuous measure a difficult problem.In addition, utilize two sub-aperture that this device space is 2.3D, according to DIMM principle, we can also obtain the spherical wave atmospheric coherence length r in limited distance ₀.

Structure of the present invention is simple, practical and convenient; As long as there is appropriate point beacon in the air, just can measure the dizzy angle such as grade in desired path section and spherical wave atmospheric coherence length simultaneously, enrich the understanding to atmospheric turbulence characteristic in limited distance, significant in fields such as adaptive optics, high-resolution imaging, Laser Atmospheric Transmission.

Accompanying drawing explanation

Fig. 1 is apparatus of the present invention structural representation;

Fig. 2 is the structural representation of an example of three hole face shields in apparatus of the present invention;

Fig. 3 is the structural representation of another example of three hole face shields in apparatus of the present invention;

The frame pseudo-colours ccd image that Fig. 4 obtains when being apparatus of the present invention actual measurement.

Embodiment

The present invention is introduced in detail below in conjunction with the drawings and the specific embodiments.

As shown in Figure 1, the dizzy angle such as limited distance real-time measurement apparatus, comprise receiving telescope, photoelectric detector and computing machine, attenuator, optical filter, imaging len, it is characterized in that: described receiving telescope front end is provided with three hole face shields, described three hole face shields are provided with three sub-pupils of circle, any two sub-pupils of circle are equipped with a point wedge mirror, the rear light path of described receiving telescope is provided with attenuator successively, optical filter, optical imaging lens, described imaging len be placed with photoelectric detector as in plane, the output terminal of described photoelectric detector is by being connected to computing machine.

The diameter of described three sub-pupils of circle is D, and the center distance between any one circular sub-pupil and two other circular sub-pupil is d ₁, d ₂, wherein meet d ₁=1.2D, d ₂=2.3D.

The span of the equal D of diameter of the sub-pupil of described circle is [0.8 (λ ₀l) ^0.5, 1.2 (λ ₀l) ^0.5], wherein λ ₀for a beacon beam effective wavelength, determined by the spectral characteristic of beacon used, optical filter, photodetector, L is surveyed turbulent flow limited distance, namely puts the distance between beacon and receiving telescope

The span of the equal D of diameter of the sub-pupil of described circle is [0.8 (λ ₀l) ^0.5, 1.2 (λ ₀l) ^0.5], wherein λ ₀for a beacon beam effective wavelength, determined by the spectral characteristic of beacon used, optical filter, photodetector, L is surveyed turbulent flow limited distance, namely puts the distance between beacon and receiving telescope

Described attenuator is neutral filter, and described neutral filter should according to actual beacon brightness adjustment attenuation rate.Described attenuator is neutral filter, and described neutral filter should according to actual beacon brightness adjustment attenuation rate.Described optical filter should select filter range according to actual beacon beam spectral property, for laser beacon, should select the narrow band pass filter of corresponding optical maser wavelength.Described optical imaging lens should according to actual light battery detector needs, the selected focal length of lens.Described photodetector is ccd detector.

Wherein, three hole face shields need be determined according to actual measurement Distance geometry beacon effective wavelength, after determining three hole face shields, choose telescope considering in device lighting and feasibility, generally choose Cassegrain's formula telescope and (be called for short cassette telescope, in Fig. 1, three hole face shield centre circle represent the telescopical secondary mirror of cassette and block, and be obstructed smooth position, thus sub-aperture need be avoided); Attenuator, optical filter, imaging len are optional components, can choose according to actual conditions; CCD chooses the GC1290 of ALLIED company.

The dizzy angle method for real-time measurement such as a kind of limited distance, utilize three circle sub-pupil acceptance point beacon light intensity, and add up that spacing is respectively 0, d ₁, d ₂the relative light intensity fluctuating covariance C that receives of the sub-pupil of circle _r(0), C _r(d ₁), C _r(d ₂), three covariances to such as to be converted at the dizzy angle by recycling computing formula, it is characterized in that, comprise the following steps:

(1), calculate that spacing is respectively 0, d ₁, d ₂relative light intensity fluctuating covariance C _r(0), C _r(d ₁), C _r(d ₂).Relative light intensity fluctuating covariance C _rd the account form of () is:

$C_R\left(d\right)=\frac{C_I\left(d\right)}{<I_1><I_2>}=\frac{<[I_1-<I_1>][I_2-<I_2>]>}{<I_1><I_2>}---\left(6\right)$

Wherein, <> represents statistical average, I ₁, I ₂represent the light intensity gray-scale value that spacing is two sub-pupils of circle of d; (2), by C _rd () is converted to log-amplitude fluctuation covariance C _χ(d):

$C_{\mathrm{\&chi;}}\left(d\right)=\frac{\mathrm{In}(C_R\left(d\right)+1)}{4}---\left(7\right)$

(3), by corresponding C _χd () substitutes into following computing formula and draws the dizzy angles such as limited distance,

${\mathrm{\&theta;}}_0=L^{-1}{\left[2.233{\left(\frac{{\mathrm{\&lambda;}}_0}{\mathrm{\&lambda;}}\right)}^2\frac{29.88C_{\mathrm{\&chi;A}}\left(0\right)+81.66C_{\mathrm{\&chi;A}}\left(1.2D\right)+76.71C_{\mathrm{\&chi;A}}\left(2.3D\right)}{D^{5/3}}\right]}^{-3/5}---\left(8\right)$

Wherein L is the atmospheric turbulence limited distance measured, λ ₀for a beacon beam effective wavelength, for laser beacon, λ ₀for optical maser wavelength.

Specific embodiment 1:

Suppose that the turbulent flow limited distance that will measure is L=15km, used some beacon is wavelength X ₀the laser of=532nm.

1., measurement mechanism design.According to condition D ≈ (λ ₀l) ^0.5, substitute into L=15km, λ ₀=532nm, first selected sub-aperture diameter D is 9cm.By condition d ₁=1.2D, d ₂=2.3D can spacing be d ₂holes lateral dimension be at least 3.3D=29.7cm, thus the clear aperture of receiving telescope can not lower than this value, telescope under this bore is cassette telescope substantially, the center secondary mirror of considering blocks, another one sub-aperture can be led to light position in annular and placed arbitrarily, only the center distance in this hole and other arbitrary holes need be made to meet d ₁=1.2D.Fig. 2 is an exemplary plot of the three hole face shields satisfied the demands.Consider the logical light of sub-aperture and the light of instrument, choose Meade company model 12 " Shi Mite-Cassegrain's formula telescope of LX200, its clear aperture 30.5cm, central obscuration 10.1cm, coke ratio f/10, focal length 3.05m.Beacon beam moderate strength, without the need to attenuator; In order to suppress sky background, add the narrow band pass filter of 532nm; Hot spot fractional dose is moderate, without the need to imaging len.Computing machine is connected with CCD by netting twine, can arrange CCD parameter, as target surface size, time shutter etc.; Computing machine is connected with telescope by Serial Port Line, can control telescope and aim at beacon in real time, prevent beacon from departing from visual field.

2., measurement mechanism calculates the method at the dizzy angles such as limited distance.In a timing statistics, a statistics frame number is interior as 1000 frames in other words, computing machine draws the gray-scale value (representing light intensity) of the every frame of CCD three hot spots through image procossing, and according to three hot spot light intensity gray-scale values of this 1000 frame, statistics show that spacing is respectively 0, d ₁, d ₂relative light intensity fluctuating covariance C _r(0), C _r(d ₁), C _r(d ₂).Relative light intensity fluctuating covariance C _rd the account form of () is:

$C_R\left(d\right)=\frac{C_I\left(d\right)}{<I_1><I_2>}=\frac{<[I_1-<I_1>][I_2-<I_2>]>}{<I_1><I_2>}$

Equation Section(Next)(1)

Its bracket <> represents statistical average, I ₁, I ₂represent the light intensity gray-scale value that spacing is two reception sub-aperture of d.

By C _rd () is converted to log-amplitude fluctuation covariance C _χ(d):

$C_{\mathrm{\&chi;}}\left(d\right)=\frac{\mathrm{In}(C_R\left(d\right)+1)}{4}---\left(2\right)$

By corresponding C _χd () substitutes into following computing formula and draws the dizzy angles such as limited distance,

${\mathrm{\&theta;}}_0=L^{-1}{\left[2.233{\left(\frac{{\mathrm{\&lambda;}}_0}{\mathrm{\&lambda;}}\right)}^2\frac{29.88C_{\mathrm{\&chi;A}}\left(0\right)+81.66C_{\mathrm{\&chi;A}}\left(1.2D\right)+76.71C_{\mathrm{\&chi;A}}\left(2.3D\right)}{D^{5/3}}\right]}^{-3/5}---\left(3\right)$

Substitute into L=15km, λ ₀the C that=532nm, λ=500nm, D=9cm and formula (2) draw _χd () can obtain the dizzy angle θ such as grade of limited distance ₀.

Specific embodiment 2:

Suppose that the turbulent flow limited distance that we will measure is L=4km, used some beacon is wavelength X ₀the laser of=630nm.

1., measurement mechanism design.With embodiment 1, measurement mechanism is except three hole face shields changes, and other are constant.According to condition D ≈ (λ ₀l) ^0.5, substitute into L=4km, λ ₀=632nm, selected sub-aperture diameter D is 5cm.For telescope 12 " sub-aperture of LX200, three diameter 5cm satisfies condition d ₁=1.2D, d ₂the sub-aperture of=2.3D is arranged with a lot, and Fig. 3 gives an example of the three hole face shields satisfied condition.Note: the central obscuration in Fig. 3 is used to illustrate telescopical secondary mirror, the structure that not three hole face shields are own.

2., computing method.With embodiment 1, in the formula (3) just at dizzy angles such as calculating, the parameter of substitution does corresponding change according to actual conditions, (range line finally calculated from dizzy angle θ such as grade ₀.

Fig. 4 gives frame pseudo-colours ccd image during apparatus of the present invention actual measurement.Can find out from this figure, three hot spots are separated good, can the light intensity of each hot spot of independent statistics and centroid position, utilize DIMM principle can also draw atmospheric coherence length value in limited distance.

The content be not described in detail in instructions of the present invention belongs to the known prior art of professional and technical personnel in the field.

Claims (6)

1. the dizzy angle real-time measurement apparatus such as limited distance, comprise receiving telescope, photoelectric detector and computing machine, attenuator, optical filter, imaging len, it is characterized in that: described receiving telescope front end is provided with three hole face shields, described three hole face shields are provided with three sub-pupils of circle, any two sub-pupils of circle are equipped with a point wedge mirror, the rear light path of described receiving telescope is provided with attenuator successively, optical filter, optical imaging lens, described imaging len be placed with photoelectric detector as in plane, the output terminal of described photoelectric detector is connected to computing machine.

2. the dizzy angle such as limited distance according to claim 1 real-time measurement apparatus, is characterized in that: the diameter of described three sub-pupils of circle is D, and the center distance between any one circular sub-pupil and two other circular sub-pupil is d ₁, d ₂, wherein meet d ₁=1.2D, d ₂=2.3D.

3. the dizzy angle such as limited distance according to claim 2 real-time measurement apparatus, is characterized in that: the span of the equal D of diameter of the sub-pupil of described circle is [0.8 (λ ₀l) ^0.5, 1.2 (λ ₀l) ^0.5], wherein λ ₀for a beacon beam effective wavelength, determined by the spectral characteristic of beacon used, optical filter, photodetector, L is surveyed turbulent flow limited distance, namely puts the distance between beacon and receiving telescope.

4. the dizzy angle such as limited distance according to claim 1 real-time measurement apparatus, is characterized in that: described attenuator is neutral filter.

5. the dizzy angle such as limited distance according to claim 1 real-time measurement apparatus, is characterized in that: described photodetector is ccd detector.

6. the dizzy angle such as a limited distance method for real-time measurement, utilizes three circle sub-pupil acceptance point beacon light intensity, and adds up that spacing is respectively 0, d ₁, d ₂the relative light intensity fluctuating covariance C that receives of the sub-pupil of circle _r(0), C _r(d ₁), C _r(d ₂), three covariances to such as to be converted at the dizzy angle by recycling computing formula, it is characterized in that, comprise the following steps:

(1), calculate that spacing is respectively 0, d ₁, d ₂relative light intensity fluctuating covariance C _r(0), C _r(d ₁), C _r(d ₂).Relative light intensity fluctuating covariance C _rd the account form of () is:

Wherein, <> represents statistical average, I ₁, I ₂represent the light intensity gray-scale value that spacing is two sub-pupils of circle of d;

(2), by C _rd () is converted to log-amplitude fluctuation covariance C _χ(d):

(3), by corresponding C _χd () substitutes into following computing formula and draws the dizzy angles such as limited distance,

Wherein L is the atmospheric turbulence limited distance measured, λ ₀for a beacon beam effective wavelength, for laser beacon, λ ₀for optical maser wavelength.