RU1145760C - Method of remote measuring of focus distance of refraction channels - Google Patents

Abstract

METHOD OF REMOTE MEASUREMENT OF FOCAL DISTANCE OF REFRACTION CHANNELS, which consists in sending a laser probe into the channel, receiving it and measuring the average refractive shift of the energy center of the probe beam from which the focal distance is measured, characterized in that, with the aim of increasing the focal distance, the measurement accuracy channel, the probing radiation is sent to the channel parallel to its optical axis at a distance from neero equal to 0.11 a ohm / 0 o ohm, and about the focal length F refractive Channel One is judged by the formula Fl chi (-) po. where aom is the initial width of the refraction} k “th channel; and, the track length of the sounding probe; with R is the average refractive displacement of the energy center of the probe beam.

Description

The invention relates to the field of measuring parameters of optical radiation, in particular refractive channels, and can be used to remotely determine the focal length of a refractive channel formed in the atmosphere when high-power laser radiation propagates through it.

An object of the invention is to increase the accuracy of measuring the focal length of a refractive channel.

The goal is achieved in that in a method consisting in sending laser probe radiation into a channel, receiving it and measuring the average refractive index.

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of the energy center of the probe beam, according to which the focal length is judged, the probing radiation is sent to the channel parallel to its optical axis, at a distance of 0.1 aohm from it, and the focal length F of the refractive channel is judged by the formula

R chi (- | -) p,

where Eom is the initial width of the channel;

L is the path length of the probe radiation;

R is the average refractive displacement of the energy center.

By measuring R at L / F, one can judge the focal length of the refractive channel. The sending of probe radiation inside the channel parallel to its optical axis at a distance of 0.1 Oehm completely avoids the distortions caused by aberrations, while at r0 0.1 x x the average refractive deviation R becomes already significant and provides; ; . provides a high accuracy of changing the focal length of the refractive channel. At the edge, the refractive channel has large aberrations that make it impossible to see the focal length (anal, since G1 beams with different distance from the optical axis are focused in different places. The only exception is the axial region of the refractive channel ( -6 0.1 Vom), where aberrations can still be neglected. Aberrations are maximally occurring at the edges of the refractive channel, therefore, the known method based on the through gap of the 8 / -M refractive channel will be effective. re lnoss m ;; y. oassto audio (y izmerenfioro (eFfektizislo) in this manner can

ACHIEVED, P ;; RANGE 5.

/; Image 8 -: as illustrated in the drawing.

Laser and puigee from source 1: the distant oggichich axis 2 of the refraction channel 3 at a distance of p o, the B channel is sent parallel to its axis and after its passage; O1, when the LB is refractory, the refractive quiap 3 hits screen 4 with a measuring scale. The light (for example, NGS screen 4 is photographed with a movie camera 5, by the spot position on the screen) - (e determine the average refractive shift of the energy center of the probe beam, and from it the focal distance of the refractive channel,

As a source 1, an LG-38 He-Me laser can be used,

As specific examples of the implementation of the method, three cases can be considered: 1) PO 0; 2) /) o -0.1 a ohm; 3) ro a ohm.

In the case when the probe radiation propagates along the axis of the refraction channel, the average value of the refractive index 11 of the energy center of the probe beam is zero (R 0) and, therefore, the measurement is not possible.

In the second case, when pc 0.1 eohm. the average value of refractive bias with the focal length of the channel

 F - d-ii (-L in Q ..

When r o-. 0.1aom can still be completely neglected by the distorting effect of aberrations. On the other hand, at pc = 0.1 Aom, the magnitude of the average refractive bias becomes already significant. For example, if L-- F. and aom 1 m, then po 10 cm and R 15 cm,

In the third case. r about aom. although the amount of displacement calculated by the formula

Th ch ((-p-)) Zone becomes even more

significant (in our case, R - 1.5 m), strong aberration distortions of the probe beam reduce the measurement accuracy to the accuracy of the prototype,

In the known method, the effective focal length of the refractive channel F is measured, which is related to the true value of this value F by the ratio

F Fi (R - / TOM - L f /) n) a ohm

-2

Even the 8th most advantageous case, when tp 2, r о.m - а ohm, R О, then F 3 F,

This calculation was carried out under the condition that the screen is Majia probe beam compared to the initial channel width. If the channel width is commensurate with the width of the probe beam, then this interconnection becomes more complicated, and the effective focal length becomes even larger. At L j F, the ratio between the effective and real focal lengths is not known, namely, under such conditions, the average refractive shift of the energy center becomes such that it can be used to judge the focal length of the channel with an error of less than 10%. In the proposed method, the magnitude of the refractive bias depends on the real focal length

() o.

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At F 10 m (the usual value for atmospheric optical refraction channels) and L F ch (- | r) i; 1.5, i.e. R 1,5x

) o, if p o 0.1m. . 15cm, which is quite measurable. If L 2F, and ro 0.1 m, then R cm.

An additional advantage of the method is the ability to study the dynamics of changes in refractive channels generated by high-power pulsed radiation.

The time of occurrence of the refractive channel in the atmosphere is 10 s, and the time of its resorption can vary from 1 to 10 s. EFFECT: invention enables effective registration of the channel resorption process.

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