RU2488095C1 - Method of determining parameters of turbulent atmosphere - Google Patents

Method of determining parameters of turbulent atmosphere Download PDF

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RU2488095C1
RU2488095C1 RU2011144051/28A RU2011144051A RU2488095C1 RU 2488095 C1 RU2488095 C1 RU 2488095C1 RU 2011144051/28 A RU2011144051/28 A RU 2011144051/28A RU 2011144051 A RU2011144051 A RU 2011144051A RU 2488095 C1 RU2488095 C1 RU 2488095C1
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atmosphere
image
turbulent atmosphere
turbulent
optical system
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RU2011144051A (en
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Анатолий Петрович Аверин
Юрий Борисович Морозов
Виктор Серафимович Пряничников
Вячеслав Васильевич Тяпин
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Федеральное казенное предприятие "Государственный лазерный полигон "Радуга"
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10Information and communication technologies [ICT] supporting adaptation to climate change.
    • Y02A90/12Specially adapted for meteorology, e.g. weather forecasting, climate modelling
    • Y02A90/14Real-time meteorological measuring

Abstract

FIELD: physics.
SUBSTANCE: rapid analysis is carried out using an optical system having a telescope, a video camera interfaced with said telescope and a computer. Images of a point object (for the given aperture) are processed; vibrations of the image relative its middle position caused by large turbulent irregularities of air density are measured at each moment in time. Further, said measurements are used to calculate the structural characteristic of the refraction index, the Fried radius and the optical transfer function of the atmosphere, and then based on the obtained data, the undistorted image is reconstructed and the Strehl parameter is calculated as the ratio of corresponding intensities in centres of the distorted and undistorted images of the point object.
EFFECT: invention enables to conduct rapid analysis of the state of a turbulent atmosphere in real time.
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Description

The invention relates to atmospheric physics and can be used to determine its parameters such as the structural characteristic of the refractive index, Strehl parameter and Fried radius.

A known method for determining the internal scale of atmospheric turbulence (Fried radius) [1], which consists in recording the intensity of the radiation transmitted through the turbulent atmosphere, determining the dispersion of its fluctuations, and after determining the dispersion of the intensity fluctuation, determining the internal scale of atmospheric turbulence.

The disadvantages of this method include the significant remoteness in the space of the receiving and transmitting radiation equipment (over a distance of the order of several kilometers), which significantly limits the ability to quickly change both the direction in which measurements are taken and the length of the atmosphere under study.

There is also a method [2], according to which pulsed laser radiation is transmitted through a turbulent atmosphere, the backscattering radiation is filtered on small-scale inhomogeneities, the backscattering amplification coefficient of single pulses is measured with a repetition rate not exceeding the fluctuation frequency of the turbulent atmosphere. Then, the backscattering gain of the pulsed radiation is determined by averaging the backscattering coefficients of single pulses and the profile of the structural characteristic of the refractive index of the turbulent atmosphere is restored by the inverse transformation of the backscattering gain of the pulsed radiation.

This known method requires the use of a powerful laser radiation source (due to the small value of the backscattering value), which significantly limits the possibility of its widespread use, especially at large distances (exceeding 1000 m).

The technical result of the proposed invention is to conduct a rapid analysis of the state of the turbulent atmosphere in real time while simultaneously including the structure of the determined parameters of the turbulent atmosphere in addition to the structural characteristics of the refractive index of the Fried radius and Strehl parameter.

The indicated technical result is achieved by using an adaptive optical system consisting of a telescope, a video camera coupled to it and a computer processing images of a point (for a given aperture) object received from the video camera, the intensity distribution of the image distorted by the turbulent atmosphere is recorded, and the structural characteristic is determined using it the refractive index, the Fried radius, and the hardware function of the atmosphere between the object and the input aperture of the optical system, were restored ayut turbulent atmosphere distorted image recorded intensity distribution of the reconstructed image and from this determine the Strehl ratio parameter as a ratio of intensities in the respective centers of the distorted and undistorted image of a point object.

The ability to achieve a technical result is based on the following. Atmospheric inhomogeneities of the refractive index can be divided into two parts according to the degree of their influence on the image [3]. Large-scale inhomogeneities (whose characteristic size is larger than the diameter of the input aperture of the optical system) lead to random displacements of the image as a whole (jitter). Small-scale inhomogeneities cause blurring of fine details of the image and deterioration of resolution due to this. The resolution of the optical system due to the influence of atmospheric distortions does not exceed the resolution of the optical system with an aperture equal to the Fried radius, the value of which near the underlying surface is of the order of several centimeters.

As is known [4-6], the structural characteristic of the refractive index C n 2 is expressed through the dispersion of jitter (the average square of the angular displacement of the center of gravity of the image of a point object) σ 2 as follows:

C n 2 = σ 2 / 5.68 ( 2 R ) - one / 3 L (2)

Figure 00000001

where 2R is the diameter of the receiving aperture;

L is the length of the observation path.

The Fried radius (r 0 ) is expressed in terms of C n 2 according to [5, 6] as:

r 0 = 1.68 ( k 2 C n 2 L ) - 3 / 5 , (3)

Figure 00000002

where k = 2π / λ is the wave vector;

λ is the radiation wavelength;

The small-scale spreading of the averaged image, provided that the jitter is eliminated, is determined by the optical transfer function, which depends on the Fried radius and the diameter of the input aperture of the optical system [7, 8]:

H ( Ω ) = exp { - 3.44 ( λ Ω / r 0 ) 5 / 3 [ one - α ( Ω / Ω 0 ) one / 3 ] } . (four)

Figure 00000003

Here Ω is the angular spatial frequency,

Ω 0 = D / λ is the cutoff frequency of the spatial frequency spectrum of the optical system, D is the diameter of the aperture. The parameter α takes the value 1 for the “near field” (when only phase effects are significant) and the value 0.5 for the “far field” (applicable when the amplitude and phase distortions are equally significant).

The drawing shows a diagram of a system of rapid analysis of the state of the atmosphere, explaining the invention.

Using a computer program, image jitter is first recorded, its variance is calculated, parameters C n 2 and r 0 , as well as the function H (Ω), then jitter is corrected, averaging and digital filtering are performed using expression (4), which eliminates small-scale blurring. As a result of such processing, a corrected (undistorted) diffraction image is obtained [9], and, comparing it with the original, the Strehl parameter is determined.

Literature

1. A.S. 1840633 USSR, MKI 4 G01W 1/00. A method of measuring the internal scale of atmospheric turbulence / P.A. Bakut, I.V. Beznezhennykh, K.N. Sviridov, Yu.P. Shumilov (USSR) - No. 3183005/28; claimed 10/28/1987; publ. 06/27/2007.

2. A.S. No. 1840481 USSR, MKI 3 G01S 17/95. A method of measuring the structural characteristics of the refractive index of a turbulent atmosphere / P.A. Bakut A. B. Aleksandrov, V. A. Loginov, V. P. Loginov, I. N. Matveev, Yu. P. Shumilov (USSR) - No. 2220623 / 09; claimed 06/08/1977; publ. 03/27/2007.

3. Candidov V. P., Chesnokov S. S., Shlenov S. A. // Optics of the atmosphere and the ocean. - 11, 522 (1998).

4. Scheglov P.V. Problems of Optical Astronomy - Moscow: Nauka, 1980.

5. Tatarsky V.I. Wave propagation in a turbulent atmosphere - M., Nauka, 1967.

6. Gurvich A.S., Kon A.I., Mironov V.L., Khmelevtsov S.S. Laser radiation in a turbulent atmosphere - M .: Nauka, 1976.

7. Goodman J. Statistical Optics - M .: Mir, 1988.

8. Fried D.L. J. Opt. Soc. Am. // 56, 1372 (1966).

9. Averin A.P., Gingerbread B.C., Tyapin V.V. Quantum Electronics // No. 40, 5 (2010), S.418-420.

Claims (1)

  1. A method for determining the parameters of a turbulent atmosphere, which includes determining the structural characteristics of the refractive index, Fried radius, and Strehl parameter and consisting in the use of an adaptive optical system coupled to a computer that restores an image distorted by the turbulent atmosphere, records the intensity distribution of the image distorted by the turbulent atmosphere, s it is used to determine the structural characteristic of the refractive index, the Fried radius, and the atmospheric hardware function EASURES between the object and the input aperture of the optical system is reduced turbulent atmosphere distorted image recorded intensity distribution of the reconstructed image and from this determine the Strehl parameter.
RU2011144051/28A 2011-10-31 2011-10-31 Method of determining parameters of turbulent atmosphere RU2488095C1 (en)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU1497520A1 (en) * 1987-07-13 1989-07-30 Центральная аэрологическая обсерватория Method of determining structural characteristic of atmosphereъs refraction index
SU1448908A1 (en) * 1986-07-17 1992-10-07 Институт Оптики Атмосферы Со Ан Ссср Method of determining optic atmosphere characteristics
SU1840481A1 (en) * 1977-06-08 2007-03-27 Научно-производственное объединение "Астрофизика" Method for changing structural characteristic of deflection coefficient of turbulent atmosphere
SU1840633A1 (en) * 1987-10-28 2007-06-27 Научно-производственное объединение "Астрофизика" Method for determining internal scale of atmospheric turbulence
RU2405172C2 (en) * 2005-07-21 2010-11-27 Эрбус Оперейшнс Гмбх Method and lidar system for measuring atmospheric turbulence on-board aircraft, as well as in airports and on wind power plants
US7872603B2 (en) * 2008-09-04 2011-01-18 The Boeing Company Method and apparatus for making airborne radar horizon measurements to measure atmospheric refractivity profiles
GB2472311A (en) * 2009-07-31 2011-02-02 Boeing Co Measuring atmospheric refractivity profile

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU1840481A1 (en) * 1977-06-08 2007-03-27 Научно-производственное объединение "Астрофизика" Method for changing structural characteristic of deflection coefficient of turbulent atmosphere
SU1448908A1 (en) * 1986-07-17 1992-10-07 Институт Оптики Атмосферы Со Ан Ссср Method of determining optic atmosphere characteristics
SU1497520A1 (en) * 1987-07-13 1989-07-30 Центральная аэрологическая обсерватория Method of determining structural characteristic of atmosphereъs refraction index
SU1840633A1 (en) * 1987-10-28 2007-06-27 Научно-производственное объединение "Астрофизика" Method for determining internal scale of atmospheric turbulence
RU2405172C2 (en) * 2005-07-21 2010-11-27 Эрбус Оперейшнс Гмбх Method and lidar system for measuring atmospheric turbulence on-board aircraft, as well as in airports and on wind power plants
US7872603B2 (en) * 2008-09-04 2011-01-18 The Boeing Company Method and apparatus for making airborne radar horizon measurements to measure atmospheric refractivity profiles
GB2472311A (en) * 2009-07-31 2011-02-02 Boeing Co Measuring atmospheric refractivity profile

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