RU2740489C1 - Laser inclinometer for long-term recording of earth surface angles - Google Patents

Abstract

FIELD: monitoring and measuring equipment.

SUBSTANCE: invention relates to test and measurement equipment. It can be used for precision measurement of angular inclination of earth surface in conditions of external temperature instability of environment. Device consists of fixed platform fixed on rocky soil, on which movable platform is installed on three identical positioners. Mobile and fixed platforms are arranged at equal distance from each other. A laser, a cell with a liquid, a focusing lens and a position-sensitive photodetector (PSPD) with a processing unit are mounted on the movable platform (MP). When the earth surface is inclined, the laser beam reflected from the liquid changes its angular position, which is recorded and processed by the PSPD and the processing unit. At change of external temperature there are undesirable shifts of laser beam. When using thermoresistive elements: a lens which focuses the laser beam on the PSPD, the parallel displacement of the laser beam does not affect the focus position, while changing its angular inclination is maintained, which eliminates the effect of parallel displacement of the laser beam on the measurement results of the same positioners, which set MP surface in parallel position with fixed platform surface, temperature changes of environment do not incline MP, which makes measurement of inclination angles of Earth's surface less temperature-dependent.

EFFECT: high temperature resistance of measuring angular inclination of the earth's surface, which makes it possible to use the device in conditions of considerable temperature changes of the surrounding medium.

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Description

The invention relates to instrumentation, namely to inclinometers.

It can be used to register the angular position of the Earth's surface in order to accurately study microseismic phenomena in the low-frequency region of the spectrum, as well as to study the slow change in the landscape of the Earth's surface, to predict earthquakes under conditions corresponding to a temperature-stabilized research laboratory using an air conditioner.

In the field of creating scientific equipment for observing the tilts of the earth's surface, methods have been developed for recording the angular tilt of the earth's surface relative to the earth's gravity vector. Known: Patent SU 1451541 A1, 01/02/1987, Zhmud AF. Thyssen V.M. "Device for measuring the angle of inclination", Patent SU 1059425 A from 07.12.1982, Grinevich FB, Novik AN, Labuzov AE, "Device for measuring small angles of inclination".

As a prototype of the invention, RF Patent No. 2510488, dated 05/30/2012, Joint Institute for Nuclear Research, Budagov Yu.A., Lyablin MV, "A device for measuring the angle of inclination" is chosen, containing a base on which are fixed: single-mode stabilized laser , a cuvette with a viscous dielectric liquid and a position-sensitive photodetector (PCHFU) with a registration unit. When the base is tilted, the laser beam reflected from the surface of the liquid changes its angular position, which is recorded by the PFC. This device uses a thin layer of liquid to increase the sensitivity of measuring the angle of inclination of the Earth's surface to reduce unwanted distortion of its surface.

Also known is the publication "A laser sensor of a seismic slope of the Earth surface" Physics of Particles & Nuclei Letters; Jan2013, Vol. 10 Issue 1, p 43-48, 6p. Batusov, V. Budagov, J. Lyablin, M, which describes a movable inclinometer platform for aligning the laser beam reflected from the liquid surface. The platform contains a direct adjustment device that allows you to change the angle of inclination of all elements of the inclinometer. This leads to a change in the position of the laser beam reflected from the liquid surface in the cell on the position-sensitive photodetector.

In the cited devices and prototype, there is a strong dependence of the inclinometer readings on changes in the ambient temperature. This interferes with high-precision measurement of the angle of inclination of the Earth's surface in the low-frequency region (within one day). Even a slight change in temperature will cause the inclinometer to tilt unwantedly.

Known methods of creating temperature stability of research equipment (Patent RU 2630948 C1 from 06.03.2016., "Method of thermal stabilization of electronic equipment", Patent RU 2240606 C2, from 2002.10.10, "Device for thermal stabilization of electronic equipment"). As a rule, thermostats operating according to the feedback principle are used for temperature stabilization (the cooling or heating system of a temperature-stable volume is switched on to change the temperature). There are also passive temperature stabilization methods that use material melting. It is known that during the melting of a substance its temperature does not change and this property is used as a temperature-stabilizing factor.

All the cited methods of temperature stabilization of the volume of the installation are limited by the fact that their use requires an increase in the dimensions of the device, which is an additional, not always feasible condition.

The invention is aimed at eliminating the disadvantage present in the analogs and the prototype (the presence of a strong dependence of the magnitude of the signal of the earth's surface tilt on the ambient temperature), and therefore at improving the accuracy of recording long-term angular tilts of the earth's surface. For this, the methods of temperature resistivity are used in the design of the inclinometer:

- temperature change does not change the tilt angle of the inclinometer.

The invention solves a technical problem, namely, increasing the resistance of the device measurements to changes in the ambient temperature.

The device contains a fixed platform rigidly fixed to rocky ground and a movable platform. The movable platform is mounted on a fixed platform using three positioners. Fixed on a movable platform: a single-mode stabilized laser, a cuvette with a viscous dielectric liquid, a focusing lens, and a position-sensitive photodetector with a registration unit. The used positioners are made of the same material and have the same geometric dimensions.

Distinctive features of the device are: the presence of a focusing lens mounted on a movable platform, which serves to focus the laser beam, after its reflection from the liquid on a position-sensitive photodetector, and three positioners having equal geometric dimensions, made of the same material, which provide a parallel position of the movable platforms relative to a fixed platform.

List of illustrations and drawings

1. Diagram of the laser inclinometer (Fig. 1, Appendix 1)

2. Displacement of the laser beam on the position-sensitive photodetector when the ambient temperature changes (Fig. 2, Appendix 2)

3. The invariable position of the laser beam on the position-sensitive photodetector when the temperature changes using a lens for the example of using a prism (Fig. 3, Appendix 2)

4. Location of the inclinometer on a complex with movable and fixed platforms with supports of different materials (Fig. 4, Appendix 3)

FIG. 1 appendix 1 shows a device in which

1. Rocky ground

2. Fixed platform

3. Movable platform

4. Positioners

5. Cuvette

6. Liquid in the cuvette

7. Laser

8. Lens

9. Position-sensitive device

10. Processing unit

The device works as follows: a laser beam from a single-mode laser source 7 is directed to a cuvette 5 with a viscous dielectric liquid and is reflected from the surface of the liquid 6. After reflection, the laser beam through lens 8 is focused on a position-sensitive photodetector 9. Results of measuring the position of the laser beam spot on PChFU 9 enter the processing unit 10. When the movable platform 3 is tilted, which is installed on a fixed platform 2, which has a rigid attachment to the rocky ground 1, using three identical positioners 4, the laser beam spot is adjusted at the center of the PChFU 9. Immediately before starting work inclinometer positioners 4 are installed in a position that ensures the parallelism of the movable 3 and the fixed platform 2. When the earth's surface is tilted, the laser beam reflected from the liquid surface changes its angular position, which leads to its displacement to the FPCHU 9. On the FPCHU 9, a signal of proportional mismatch appears the ionic angle of inclination of the Earth's surface, which is registered and analyzed in the processing unit 10. The registered signal makes it possible to judge the inclination of the Earth's surface.

The change in ambient temperature, as a rule, occurs over a long period of time day-night.

The use of thermoresistive elements, namely, a lens fixed on a movable platform and serving to focus the laser beam on a position-sensitive photodetector, positioners made of the same material and having the same geometric dimensions, ensuring the parallelism of the movable platform relative to the fixed platform, allow long-term operation inclinometer when the ambient temperature changes.

Explanation of the operation of thermoresistive elements

1 Focusing lens

1.1 Operation of the device without using a focusing lens

FIG. 2 appendix 2 identifies new elements:

11 - glass prism,

12 designation of the prism, the laser beam of the support under the PChFU, PCHFU at the initial temperature

13 designation of a prism, a laser beam, a support for a PChFU, a PChFU with temperature changes

14 steel support for PChFU

15 displacement of the laser beam due to temperature changes.

Using the example of using a prism in the device as an element for inputting and outputting a laser beam into a cuvette, we will illustrate the stability of the inclinometer with a lens when the ambient temperature changes. FIG. 2 Appendix 2 shows the movement of the laser beam in the inclinometer before the temperature change in the environment 12 and after the temperature change in the environment 13 without using a lens. As can be seen due to the different focus of the ambient temperature. Such displacement of the laser beam can be interpreted as inadmissible tilt of the inclinometer for accurate measurements.

1.2 Operation of the device using a focusing lens

FIG. 3 appendix 2 indicates new elements

6 - Focusing lens

16 support for focusing lens

Due to the property of the focusing lens - the invariability of the position of the focal spot with a parallel displacement of the laser beam 13 on the lens 6 relative to the previous position 13. Parallel displacement of the laser beam in front of the lens does not lead to a displacement of its focus Parallel displacement of the laser beam arises from the difference in the change in the height of the same supports under the photodetector 14 and the lens 16 and the change in the height of the laser beam after reflection from the prism with the change in temperature.

2. Positioners made of the same material and having the same geometric dimensions.

2.1 Operation of the device with different types of positioners.

FIG. 4 appendix 3 marked new elements

16 and 17 Positioner supports made of different materials

Positioners 4 with supports 16 and 17, which are made of different materials, have different coefficients of thermal expansion. When the ambient temperature changes, different-scale changes in the dimensions of the supports 16 and 17 of the positioners 4 occur. This leads to a tilt of the movable platform 3 and, accordingly, to undesirable noise in the inclinometer.

The use of thermoresistive elements working simultaneously: a focusing lens and positioners made of the same material and having the same geometric dimensions allows measurements with a reduced influence of the ambient temperature measurement on the results of changes.

The device can be made as follows.

All metal elements of the inclinometer (movable and fixed platforms of the support for the laser source, FPCH and lenses) are made of stainless steel. A laser source with a wavelength of 0.65 μm and a power of 5 mW is used. We use vacuum oil as a viscous dielectric fluid. A quadrant photodetector is used as a PFC. An ADC and a computer are used as a processing unit.

Claims (1)

A laser inclinometer for long-term recording of the angular inclinations of the earth's surface, including a fixed platform rigidly fixed on rocky ground, a movable platform placed on a fixed platform using three positioners and which contains equipment fixed on it in the form of a single-mode stabilized laser, cuvette with a viscous dielectric a liquid located in the path of the laser beam, and a position-sensitive photodetector with a registration unit, serving to measure the angular position of the laser beam reflected from the liquid surface, characterized in that a focusing lens is included in the device to increase the device measurement resistance to changes in ambient temperature , fixed on a movable platform and serving to focus the laser beam on a position-sensitive photodetector, while the used positioners are made of the same material and have the same geometrical different sizes.

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