SU1436631A1 - Method of measuring curvature radius of laser beam wave front - Google Patents

Abstract

The invention relates to the field of measuring the parameters of laser radiation and can be used in adaptive optics. The purpose of the invention is to reduce energy losses and simplify measurements for high-energy laser radiation. The goal is achieved by determining the size of the laser beam per dag of the small nonlinearity length by the size of the backscattered signal. The radius of curvature of the wave front is determined by the ratio of the size of the radiating aperture to the angular increment between the size of the radiating aperture and the size of the beam section. 2 Il. at

Description

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05 05 SAE

The invention relates to the field of measuring the parameters of laser radiation and can be used in adaptive optical systems focusing pulsed laser radiation on remote objects for measuring the increase in the curvature of the wave front of the initial field of radiation of a laser generator.

The circuit is the reduction of energy losses and simplification of measurements of the radius of curvature of the wave front of laser radiation with increased energy; 15

In Fig, 1 gfeivedena block diagram of the device DP implementation of the method; Fig. 2 is a beam forming circuit.

The device comprises a synchronizer 1, a laser generator 2 an adaptive 20 optical system 3, a receiving optical system 4, a matrix of 5 optical radiation receivers, a time selector 6, a meter 7 of the image dimensions of the received signal and 25 a meter 8 of the radius of curvature of the wave front.

The principle of the operation of the device is explained in FIG. 2, where, in the approximation of geo-metric propagation of direct, direct-intense laser radiation, thermal self-action and turbulence have an effect, and the low-intensity backscatter signal influences the low-intensity signal. Therefore, the effect of thermal self-action and turbulence was assessed. The calculations were carried out on the most typical characteristics of a beam with a high radiation energy and parameters of its transmitting / receiving path. Wavelength 8, the radius of curvature of the wavefront F from 10 m to infinity, the nonlinearity parameter varied from 10 to 10, the structural characteristic of the fluctuations of the dielectric constant of air was sequentially set from to the effective radii of the transmitting and receiving apertures of 0.5 m, the calculations were carried out for the sharp image plane As a result of the calculations, it was established that with a reception range shorter than the length R of nonlinearity (L-iRy), the maximum value of the intensity of the received signal decreases by 5% due to influenced

optical optics shows a scheme of the formation of thermal self-action and turbulence of the focused atmospheric luminosity with unfavorable

beam in the XQY plane, where M is the radiation of the luchagac aperture of the source, arc

propagation conditions At the same time, resizing the image of the received signal and shifting the coordinates of its energy center does not exceed 1%.

BD is the phase distribution of the initial field of the source with a radius of curvature of F BD B D on, CC is the linear size of the beam cross section at a distance of 00 L from the scale source. From simple geometric relations, the value of F for apertures used in practice (M 1 m) -, and

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distance L 1 km From this expression it follows that to determine the radius of curvature of the initial front of the source field, it is necessary to measure the linear dimensions of the radiating aperture and the cross section of the laser beam at a distance L,

The linear dimensions of the radiating aperture can be measured by known methods and are the passport characteristic of a laser generator. In order to measure the linear dimensions of the beam cross section at a certain distance from the source (), the shape of the scatter signal is used in the invention.

Beside the propagation of forward direct-intense laser radiation, thermal self-action and turbulence have an effect, and the low-intensity backscattered signal has turbulence. Therefore, the effect of thermal self-action and turbulence was assessed. The calculations were carried out on the most typical characteristics of a beam with a high radiation energy and parameters of its transmitting / receiving path. Wavelength 8, the radius of curvature of the wavefront F from 10 m to infinity, the nonlinearity parameter varied from 10 to 10, the structural characteristic of the fluctuations of the dielectric constant of air was sequentially set from to the effective radii of the transmitting and receiving apertures of 0.5 m, the calculations were carried out for the sharp image plane As a result of the calculations, it was established that with a reception range shorter than the length R of nonlinearity (L-iRy), the maximum value of the intensity of the received signal decreases by 5% due to influenced

0 thermal self-action and atmospheric turbulence with unfavorable

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propagation conditions At the same time, resizing the image of the received signal and shifting the coordinates of its energy center does not exceed 1%.

The device works as follows.

The laser generator 2 generates a sequence of optical radiation pulses that, having passed through the adaptive optical system 3 (beam beams, are directed to a remote object. The beam propagates in the atmosphere, scatters on its components, and the backscatter signal through the receiving optical system 4 enters To the matrix 5 of optical radiation receivers, the output of the latter with the help of a time selector 6, whose operation with the help of synchronizer 1 is associated with the repetition period of a pulse, is allocated a signal l sooteetstruyuschy trailing edge of each transmitted pulse. In this case the duration of each signal is a pulse duration cTjio- biruyuschego selected from conditions providing the minimum error

measurement, and the reception distance is set a priori not exceeding the length of the nonlinearity. In the meter 7, the size of the image of the received signal for each pulse coming from the time selector 6 is measured by the dimensions of the image, which in the meter 8 of the curvature radius of the wave front determines the desired radius of curvature of the wave front of each emitted pulse.

In contrast to this, this solution does not require the forced removal of a part of the radiated energy to the measuring device, since dp of measuring the radius of curvature of the wave front suggests using the informative properties of the backscatter signal. This makes it possible to reduce energy losses as well as simplify the implementation of the method for measuring the radius of curvature of a laser beam wavefront.

Claims (1)

Invention Formula A method for measuring the radius of curvature of a wavefront of a laser beam, which consists in forming 0 0 five laser beam and measured the cross-sections of the beam cross-section, which are used to calculate the radius of curvature of the wave front, which is shade, which, in order to reduce energy losses and simplify measurements for the laser beams with photo-wired energy, measure the scattered radiation before measurements. the atmosphere in the opposite direction from the distance LJ not exceeding the length of the nonlinearity, the dimensions of the beam cross section at the height L from the radiation of the aperture are measured according to the characteristics of the radiation, the angles are determined The second increment between the dimensions of the radiating aperture and the cross-sectional dimensions of the beam at a distance L, and the radius of curvature of the wave front of the laser beam F are calculated from the ratio of the dimensions of the radiating aperture to their angular increment by the formula F.L-S-, a - a where a, ip are the effective radii of the radiating aperture and the beam cross section and the distance L from it, respectively. 9g.1 at A X