SU1226195A1 - Arrangement for measuring gradient for refractive index - Google Patents

Description

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The invention relates to the field of refractometry1) and can be used in aero and hydrodynamics.

The aim of the invention is to reduce the time and increase the accuracy of measurements.

The drawing shows a diagram of the device.

The device contains a laser 1, a baffle 2, a dividing unit consisting of a dividing cube 3 and a turning prism 4, a forming optical system 5 and a receiving 6 optical system, two connected photoreceiver 7, a point source 8 of radiation transmitting optical system 9 to form a wide parallel beam, two large semitransparent plates 10 and 11, an optical system 12 for converting a parallel beam into a convergent, Foucault 13 knife from a 14 ° screen

The device works as follows.

The test medium 15 is placed between the semitransparent plates 10 and 11, which contains a non-uniform region 16. A wide parallel beam of light formed by the point source 8, the optical system 9 and the semitransparent plate 10 falls on the test medium. After passing through the test medium a wide beam , reflecting from a plane-parallel plate 11, pops onto the optical system 12, at the focus of which Foucault's knife is located .13, and then falls on the screen 14, Part of the world, passing through an optically inhomogeneous medium, off it is from the original direction and is delayed by Foucault's knife, which will lead to a redistribution of the screen illumination. Thus, a picture appears on the screen that allows us to determine the exact location of the heterogeneous area in the medium under study or to determine the presence and location of microstructures. After that, using the deflector 2, the parallel beams of the refractometer are moved in such a way that one of the beams (measuring) closely approaches the non-uniform area or microstructure, which is supposed to be investigated, and the additional beam goes. outside of this area. If the extra beam hits also

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in a non-uniform area, then it is necessary to change the distance between the measuring and additional beams by moving the turning prism. In addition to the shadow pattern, two bright points are observed on the screen, one of them is located close to the area under study, and the other lies at a certain distance from it. When moving the prism, it is necessary to change the distance between the photodetectors, which is done during the alignment of the system.

When measuring, the measuring beam moves parallel to itself with a step that is chosen based on a qualitative pattern of heterogeneity.

When the deflector operates, the measuring beam moves, and therefore the photodetector moves as well, which reduces the measurement accuracy. In order that the movement does not affect the accuracy, an additional beam is introduced, which, moving together with the measuring beam, goes all the time outside the heterogeneity.

The measurement of the deflection angle of the measuring beam is performed as follows. Additional coordinate-sensitive sensors: the photodetector moves in such a way that the output current of the photodetector is zero when an additional one hits it. This means that the additional beam falls symmetrically with respect to the measuring areas of the photodetector (the beam deflection angle is 0). The main photodetector is rigidly connected in the process of measurement with the additional one and is at a distance from it that is equal to the distance between the measuring and additional beams to non-uniformity. Therefore, the output signal of the measuring coordinate-sensitive photodetector is caused by the deviation of the measuring beam only due to the presence of a gradient of the refractive index in a non-uniform region. This eliminated the effect of any random variables leading to beam deflection.

The photodetector used is a position-sensitive photodetector, which consists of two rectangular areas, the signal from the latter is subtracted. If, the beam falls symmetrically with respect to

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plo: adok, then the output is 0. When the Jiyia is shifted, an output signal appears, the value of which in the working area can be considered to be proportional to the displacement in the first approximation.

If there is a microstructure in the studied medium, the position of which is not changing, the initial shadow pattern is determined by the location of such a structure at a given point in time, and then when scanning the microstructure, the measuring beam determines the distribution of the refractive index gradient „

The measurement accuracy is due to the fact that the magnitude of the deflection angle (or displacement) of the beam going through the inhomogeneity is affected, besides the heterogeneity itself.

Editor L.Gratillo

Compiled by V.Varnavsky

Tehred n.Bonkapo Proofreader E.Sirohman

Order 2117/35 Circulation 778 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Design, And

1954

extraneous factors, such as care of the radiation pattern of the laser radiation. Moreover, the effect of the departure of the radiation pattern is so great that it is this factor that limits the accuracy and sensitivity of measurements with a refractometer. The use of an additional beam going out of non-uniformity eliminates the influence of these extraneous factors, since the additional photodetector is set before each measurement in such a way that its output signal is equal to 0. Since the main photodetector is rigidly connected with the additional photodetector, then its signal is due only to the deviation of the measuring beam due to the presence of a gradient of the refractive index in an inhomogeneous medium.

Claims (1)

DEVICE FOR MEASURING THE REFRACTOR INDEX GRADIENT, containing a laser, an optical forming system, an optical receiving system, a coordinate-sensitive photodetector, characterized in that, in order to reduce time and improve measurement accuracy, two translucent plates, a point light source, an optical one are additionally introduced into it transmission system, additional receiving optical system, Foucault knife, screen, deflector, beam splitter, consisting of a dividing cube and a rotary prism, and additional coor the sensitive-sensitive photodetector, with the deflector and the dividing cube located sequentially on the optical axis of the device between the laser and the optical forming system, the point light source and the optical transmitting system are located perpendicular to the optical axis of the device and are optically connected to the first translucent plate, and the additional receiving optical the system, the Foucault knife and the screen are optically coupled to a second translucent plate and mounted on an axis perpendicular to cal axis of the device, both translucent plate disposed at an angle of 45 ° to the optic axes and perpendikulyarny'odna other, and an additional rotating prism of coordinate-sensitive photodetector are optically coupled and are arranged to 'axis parallel to the axis of the device, and mechanically connected with the main photodetector. "SU„ „1226195> I 12