RU2545311C1 - Device for determination of location vertical - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device contains a sensitive element that is a ballistic gravity meter which measures acceleration of gravity by means of bunch of nonparallel laser beams.

EFFECT: high measurement accuracy.

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Description

The invention relates to devices for determining the vertical position of a place or a horizontal plane perpendicular to it.

Known devices [1], in which for the vertical exhibition using a combination of the incident and reflected from the surface of the oil or mercury light beam. The use of such devices is limited by surface rippling under the action of microseisms on a fixed base and surface oscillation on a moving one.

Known levels [2], intended mainly for work on a fixed base.

Accelerometers [3] adopted for the prototype have a sensitivity of the order of 1 angle. from. When working on moving objects, they are part of the gyro-vertical with an error of about 1 angle. min

The objective of the invention is to increase the accuracy of determining the vertical position.

The problem is solved in that a ballistic gravimeter is used as a sensitive element of the device, in which the acceleration of gravity is measured using a beam of non-parallel laser beams.

Fig. 1 shows a diagram of the device, which adopted the following notation:

1 - base, 2 - gravimeter, 3 - vacuum chamber, 4 - catapult, 5 - test body, 6 - laser, 7 - optical beam splitter, 8 - dividing optical element, 9, 10 - interference screens, 11, 12 - photodetectors , 13 - computer, 14 - optical window of the vacuum chamber.

The difference from the prototype is that the accelerometer measures the sine of the angle of deviation from the vertical, and the gravimeter has two cosines, the ratio of which contains the tangent of this angle.

. Рассмотрим одноосный вариант. Если произвести измерение вторым лучом, повернутым на известный угол β к первому, то получим $$g_2=\frac{g}{\cos \left(\beta -\alpha \right)}$$

. Взяв отношение измеренных величин можно вычислить угол наклонаIt is known from [1] that the value of the gravitational acceleration g ₁ measured by an absolute laser gravimeter depends on the cosine of the angle α of inclination to the vertical $$g_{\mathrm{one}}=\frac{g}{\cos \alpha }$$

. Let's consider a uniaxial option. If you measure with a second beam, rotated by a known angle β to the first, we get $$g_2=\frac{g}{\cos \left(\beta -\alpha \right)}$$

. Taking the ratio of the measured values, we can calculate the angle of inclination

$$\alpha ={\tan }^{-\mathrm{one}}\frac{\mathrm{one}}{\sin \beta }(\frac{g_{\mathrm{one}}}{g_2}-\cos \beta )$$

For small angles α and β, the expressions for the angle and its error will take the form:

, $$\Delta \alpha =(1-\frac{\alpha }{\beta })\Delta \beta$$

, $$\alpha =\frac{\delta g}{\beta }+\frac{\beta }{2}$$

, $$\Delta \alpha =(\mathrm{one}-\frac{\alpha }{\beta })\Delta \beta$$

,

, ∆β - погрешность определения угла β.Where $$\delta g=\frac{g_{\mathrm{one}}-g_2}{g}$$

, ∆β is the error in determining the angle β.

From these expressions it is clear that the angle β should be chosen so that its value is commensurate with the value of the expected error.

A ballistic laser gravimeter 2 is installed on the test base 1, containing a vacuum chamber 3, inside of which a test body 5 is thrown by the catapult 4. The laser 6 is placed outside the vacuum chamber. Inside the camera are fixed: an optical splitter 7, an optical dividing element (translucent mirror) 8 and screens 9 and 10. Photodetectors of interference signals 11 and 12 and a computer 13 are installed in the upper volume of the gravimeter, separated from the vacuum chamber by an optical window 14.

The beam emitted by the laser 6 enters the optical splitter 7, the reflective faces of which are made parallel to each other. From the bifurcator, a pair of converging or diverging rays enters the translucent mirror 8. On the mirror, the rays branch out, forming two pairs of rays. One of them falls on the corner reflector of the test body 5, and the other on the screens 9 and 10. After re-reflection on the corner reflector, the rays fall on the screens, forming interference patterns on them. The pictures are read by the photodetectors 11, 12 and converted into electrical signals flowing into the calculator 13. After processing the signals, the calculator gives the value of the angle of inclination of the base. The vacuum chamber is separated from the rest of the gravimeter, and in the upper part a plane-parallel plate 14 is used as a cover.

It can be seen from the description that the angle of divergence of rays and its stability depend only on the angle between the reflecting faces of the separator 7. The separator operates in vacuum, it can be made of highly stable material, for example, from an aged quartz single crystal, the chamber can be thermostated up to cryogenic temperatures. Under the above conditions, the error ∆β will be less than a tenth of a second of arc.

In real measurements, at least three beams are used.

On a moving base under the influence of portable accelerations, the test body will move in a horizontal plane relative to the rays, but this will not affect the angle β.

Information sources

1. A.P. Yuzefovich, L.V. Ogorodova. Gravimetry M .. Nedra, 1980.

2. Laser level. Pat. RF 2237825 C1, 08/12/2004.

3. Rivkin S.S., Berman Z.I., Okon I.M. “Determining the orientation parameters of an object by a strapdown inertial system.” St. Petersburg, Central Research Institute "Elektropribor", 1996

Claims (1)

A device for determining the vertical of a place containing a sensitive element, characterized in that a ballistic gravimeter is used as a sensitive element, in which the measurement of the acceleration of gravity is carried out using a beam of non-parallel laser beams.