SU1587330A1 - Interference device for measuring angles of slope of object - Google Patents

Abstract

The invention makes it possible to measure the angles of inclination of the device relative to the local horizon. The aim of the invention is to increase sensitivity by increasing the difference in travel between the interfering beams when the object is tilted. A collimated monochromatic radiation beam at an acute angle is directed at a plane-parallel plate 3 with a otrodiruyuschim coating 4 on its outer side. The plate 3 is divided into two parts, one of which is reflected from its entrance face, and the other from the reflecting coating 4 on its output face. Both parts of the split beam are sent at an acute angle to a flat mirror 5 connected to an artificial horizon 6 node made of a cell that is partially filled with mercury. Reflect with a flat mirror 5 both parts of the beam onto a plane-parallel plate 3. Re-divide each part into two. Spatially, they combine parts of the beams with equal intensity, establish their resulting field and, based on the formed interference pattern on the position-sensitive photodetector 8, judge the position of the device relative to the local horizon and the angle of inclination of the device. Il. 1.

Description

The invention relates to measuring technique and can be used to measure the orientation of geodetic instruments and take into account the error of the tilt of the vertical axis and determine the elevation angles.

The purpose of the invention is to increase the sensitivity by increasing the path difference between the interfering beams when the object is tilted.

The drawing shows a schematic diagram of a device.

The device comprises a monochromatic radiation source 1, for example a laser, a telescopic optical system 2, a plane-parallel plate 3 with a reflective coating 4 on its output surface, a flat mirror 5, an artificial horizon assembly 6 made of a cell partially filled with mercury, a receiving lens 7, coordinate a sensitive photodetector 8, for example, a CCD, a housing 9 and a processing unit (not shown). The drawing also shows the damping fluid 10, for example, oil, on the surface of the mercury, polaroid 11, used to increase the contrast of the interference pattern when using a linearly polarized source, and windows 12, which provide sealing of part of the device,. The source and the photodetector are installed at an acute angle to the plane-parallel plate 3 and the mirror 5, which are parallel to each other in the initial position. All elements of the device are rigidly fixed in the housing 9 with the exception of a flat mirror 5, the housing is designed to be installed on a controlled object.

The drawing also indicates the angles h. i2 primary and secondary incidence of radiation on a plane-parallel plate, angles Θί, the refraction of the corresponding beams in a plane-parallel plate.

The device operates as follows.

The light beam from the source 1 is collimated by a telescopic system 2 and directed at a fixed angle C through the optical window 12 of the cuvette to the front surface of the plane-parallel plate 3. The beam is partially reflected from the front surface and partially refracted at an angle of 01, after which it is reflected from the reflective coating 4 and having refracted a second time on the front surface, it leaves plate 3 parallel to the primary beam with some displacement. Next, both beams are sent to the horizontal surface of the mirror 5, connected to the node 6 of the artificial horizon. Reflected from the mirror, the beams are again sent to a plane-parallel plate 3, on the surfaces of which the sequential division, reflection and refraction of the beams is repeated. As a result, four light beams emerge from the plate 3, the two central of which have the same intensity due to the equal number of reflections and refractions. These beams pass through the second optical window 12 of the cuvette, superimpose and form an interference pattern formed by the lens 7 on the photosensitive surface of the photodetector 8.

The path difference of these beams is determined by the well-known expression describing the path difference in the Jamen interferometer

Δ = 2 P h (COS Oi - cos 0i) ~ 2 nh sin θόθ, where h is the thickness of the plate 3;

η is the refractive index of the plate material;

01, ft - angles of primary and secondary refraction of rays on the front surface of the plate 3.

With strict parallelism, the surfaces of the plate 3 and the mirror 5. obtained by preliminary alignment of the plate 3, the condition is met: ii = i 2; 01 = ft; (50 = 0; Δ = 0.

In this case, the field of view of the lens 7 is uniformly illuminated and an interference band of infinite width is formed on the surface of the photodetector 8, so that light fluxes of equal intensity fall on all photosensitive areas of the photodetector 8.

In the case of the tilt of the controlled object (not shown), the housing 9 and all elements of the device are tilted relative to the horizontal reflective surface of the mirror 5, which remains unchanged due to the node 6 of the artificial horizon, which leads to the appearance of a mismatch angle a between the horizontal surface of the mirror 5 and surfaces of a plane-parallel plate 3 and the formation of interference fringes on the photodetector 8. Moreover, taking into account that 1r = h ± 2a, where C and i2 are the primary and secondary angles of incidence at dnyuyu surface of the plate 3, at small angles "get used 0 = ft - 0! = arcsin ^Sln Q- ¹ _n ⁺ - ² -g) 5 sin h _ /. sin in 1

- arcsln -----— 2 a iarcsin ---- = n \ n / = 2acos and (n ² - sin ² li) ^{1 // 2} .

Then the expression for the difference in the path of the interfering beams will be transformed, ⁵ , l sin h given that sin ¹ , to the form η

Δ = 2 ha sin 2 and (η ² - sin ² n) ^1/2 .

Based on the condition of the maxima of the interference pattern K Δ = 2 ltp, where m = ± 1; ± 2, ± 3 K = 2 l / λ, where λ is the radiation wavelength, the angle of inclination of the device, and when the interference pattern is shifted by an integer number of bands, the following dependence is determined 15 as follows: _a _ GPLUp ² ~ sin ² And h sin ² ii

The above dependence allows 20 to obtain a calculation formula for determining the thickness h of a plane-parallel plate 3 for a given angular sensitivity of the device, corresponding to one interference band, i.e. 25 h _D ² ~ sin ² I az · sin 2 1 '

For a fixed angle of incidence of light on the surface of the plate 1 = 45 °, the expression is simplified to the form. _ZV _n ² -0.5

2az

The device allows you to snap angular deviations of the object to the local horizon.

Claims (1)

Claim An interference device for measuring the tilt angles of an object, comprising a plane-parallel plate, a housing, optically coupled radiation source mounted therein, oriented at an acute angle to the plane-parallel plate, a telescopic system, a mirror located parallel to the plane-parallel plate, and a photodetector with a processing unit, characterized in that, in order to increase the sensitivity by increasing the path difference between the interfering beams when the object is tilted, it is equipped with an art unit A horizontal plane connected to a mirror, a plane-parallel plate is connected to a housing intended for installation on a controlled object, and the mirror is located in the reverse direction of radiation from a plane-parallel plate, the output surface of which is made with a reflective coating. Compiled by N. Soloukhin Editor V. Danko Tehred M. Morgenthal. Proofreader I. Muska • Order 2412. Circulation 495 Subscription VNIIIPI of the State Committee for Inventions and Discoveries at the State Committee for Science and Technology 113035, Moscow, Zh-35, Raushskaya nab., 4/5 Production and Publishing Plant Patent, Uzhgorod. Ud.Gagarina, 101