SU1218292A1 - Device for measuring coat thickness - Google Patents

Abstract

The invention relates to a measuring technique and is intended to measure the thickness of external polymer coatings on pipes in a process stream. The purpose of the invention is to improve the measurement accuracy. One beam of light after the beam splitter through the mirror and the modulator, which divides the stream into two, each of which is directed to the corresponding mirror, goes to one of the optical systems, made in the form of a housing with a hole in the side wall and end face, in which are placed sequentially one after another along the optical axis of the system a mirror located at an angle to the optical axis with a reflective coating to the hole in the side wall of the housing, screen, diffuse reflector, spherical mirror with a hole in its center, conical light a gadfly mounted with a large diameter end in the direction of a spherical mirror, a radiation receiver and a lens installed in a hole in the end wall of the housing and optically coupled to a diffuse reflector. The second beam is directed to the second modulator, dividing the beam into two beams coming through the mirror into the second optical system, similar to the first one. Both optical systems are installed above the object one before, and the other after the area of the object to be coated, which allows to take into account the optical characteristics of the pipe sections caught in the field of sight of both systems. The signal processing unit processes information from both optical systems and reports the thickness of the coating in digital form on the display. 2 Il. 1 to

Description

one

The invention relates to a measurement and control technique and is intended to measure the thickness of external polymer coatings on pipes in a process stream.

The purpose of the invention is to improve the measurement accuracy of the coating.

FIG. 1 shows a block diagram of the device; in fig. 2 - optical system design.

The device for measuring the coating thickness contains a monochromatic radiation source 1, two optical systems 2 and 3 installed respectively before and after the coating area 4 on the pipe 5, the beam splitter 6, the modulators 7 and 8, a set of mirrors 9-13 that serve to input the radiation into optical systems 2 and 3 and block 14 of signal processing.

In turn, each of systems 2 and 3 contains a cylindrical body 15 (Fig. 2) with a mirror 16 installed inside it along the optical axis, a screen .17, a diffuse reflector 18, a spherical mirror 19 with a hole in its center, a conical light guide 20 and receiver - -21 radiation. To enter the radiation, the housing 15 has openings 22 and 23.:

The source 1 is an IR laser, the radiation of which is partially transmitted by the material of the coating;

The modulators 7 and 8 are rotating disks with alternating apertures and reflective surfaces in the form of sectors (not yet, channels) and serve to receive two bunches of pulsed radiation.

The screen 17 in the optical system serves to suppress the radiation mirrored by the surface of the coating 4, whereby only light is received by the receiver 21, which does not contain information about the thickness of the coating. The screen 17 has the shape of a circle with a diameter that is calculated from the geometry of the optical scheme.

The surfaces of screen 17 are blackened to eliminate multiple reflections of light ..

The spherical mirror 10, the diffuse reflector 18 and the conical light guide 20 form a collecting system that is little sensitive to changes in the parameters of the input light beam (scattered by the surface of the tube 5 and

fallen in the field of system sighting), caused by changing the position of the pipe 5 relative to the system.

Diffuse reflector 18 is a roughened metal plate. The height h of the protrusions (roughness) is determined from the well-known Relay criteria for obtaining diffuse reflection with a spherical scattering indication.

A conical light guide 20 serves to collect and transmit light from a large area of a hole in a spherical mirror 19 to a receiver 21 with a small area.

15 photosensitive element. The maximum diameter of the aperture of the spherical mirror 19 and, respectively, of the entrance-end of the light guide 20 are limited to the limits of the solid angle formed by the screen 17. The choice of the diameter of the input (larger) end is closest to the maximum. In this case, a greater luminous flux enters the receiver 21.

The geometrical parameters of the light guide 20 are also selected from the condition of providing full internal reflection.

The light guide 20 is made of a material that is transparent in the wavelength region of the radiation source 1.

A lens 24 is placed in an opening 22, which serves to direct a beam of light onto a diffuse reflector 18. Hole 23 and the lower part of the housing. 15 are covered with glasses or plates (not shown) that are transparent for a given radiation wavelength. The holes 22 and 23 and the lower part of the housing 15 are blown with a stream of air or nitrogen when the sensor is operated directly in the coating chamber.

The mirror 13, which directs the radiation part directly to the diffuse reflector 18, serves to take into account the fluctuations of the power of the source 1 and the sensitivity of the receiver 21.

This device implements an amplitude measurement method based on the dependence of the intensity of light transmitted through the coating layer 4 on the coating thickness.

The device works as follows.

The light from source 1 is divided by beam splitter 6 into two beams, one of which is directed by mirror 9

3

on the modulator 7 of the optical system 2, the other on the modulator 8 system 3.

The modulator 8 also creates two, radiation beams modulated in antiphase relative to each other. The first beam with the help of mirrors 12 and 16 through the opening 23 is directed to the pipe 5 with the coating 4.

A part of the light is mirrored from the outer surface of the coating 4, another passes through it, is reflected with the scattering of the rough surface of the pipe 5, and then the coating layer again passes and comes out.

The light beam reflected by the coating 4 overlaps with the screen 17. Scattered light passes the screen 17 and hits a spherical mirror 19, which directs it to the diffuse reflector 18. From the reflector 18, the light enters the conical light guide 20 and

to receiver 21. I

With a possible displacement of the pipe 5 (for example, due to the waviness of its surface) along the X axis relative to the neutral position, the distribution of the intensity of light falling from the mirror 19 onto the surface of the reflector 18 changes: the light ring on the surface of the reflector expands, not changing its position. When the tube 5 is displaced along the axis H and when it is turned through an angle, the intensity inside the light ring also redistributes: the ring becomes asymmetric in intensity. But due to the fact that the reflector 18 is diffuse with a spherical scattering indicatrix, the intensity distribution of the additional scattered radiation does not change in the plane of the larger end of the light guide 20. Accordingly, the intensity of the light falling on the receiver 21 does not change. Thus, for a given measurement error of the thickness of the coating 4, the effect of different displacements of the pipe 5, its curvilinearity and waviness within certain limits is offset.

The second beam from the modulator 8 is directed to the mirror 13, and by using it through an opening 22 with a lens 24, directly to the reflector 18, which scatters the radiation, part of which enters the superconductor

Product 20 is registered by receiver 21.

The electrical signals from the receiver 21 enter the electronic processing unit 14, which normalizes the signals from the first (measuring) pulsed radiation beam with respect to the signals from the second (reference) beam. As a result of this, the influence of the instability of the power of the source 1 and the sensitivity of the receiver 21 is eliminated.

The optical system 2 is mounted to the coating site -4,

15 works in a similar way with the only difference that the light beam from the mirror 16. immediately falls on the rough surface of the pipe 5. The light scattered by the surface of the pipe 4 is detected by the receiver 21 of the sensor 2, which is also connected to block 14.

In this case, the optical system 3 endorses the same section of pipe 5, which was previously in the field of system 2, i.e.

25, system 2 is a reference with respect to system 3. The presence of two optical systems 2 and 3 makes it possible to take into account the optical characteristics of the sections of pipe 5 trapped in the field of view

neither of systems 2 and 3.

Unit 14 performs the full processing of signals coming from the receivers 21 of the two sensors. It stores in its memory the value of the normalized signal J. from the receiver of system 2 all the time it takes to move the pipe section from system 2 to system 3.

After the arrival of the corresponding signal from system 3 and after its normalization, block 14 logorizes the ratio of the normalized signals and from the calibration graphs determine the thickness of the coating.

Pre-calibration of the device is carried out on samples with reference coating thicknesses and includes determining the degree of influence on the signal value of the receiver 21 of different displacements of the pipe 5.

The information about the thickness of the coating is displayed in digital form on the display of unit 14 and in analog form on the recorder.

The device for measuring the thickness of the coating allows to spend an unlimited

tact control of the coating thickness immediately after its application, i.e. still in the molten state with an accuracy consistent with the requirements of the control coatings on the pipes in the process stream.

An increase in measurement accuracy is achieved by increasing the signal-to-noise ratio, eliminating the effect of changing the position of the tube relative to optical systems, and taking into account the optical characteristics of the tube surface, the instability of the power of the radiation source and the sensitivity of the receiver.

Claims (1)

Invention Formula An apparatus for measuring coating thickness, comprising a radiation source, an optical system, including a radiation receiver, and a signal processing unit, different. In order to improve the measurement accuracy, it is equipped with a beam splitter installed at the radiation output from a source made of monochromatic, five mirrors, two of which are installed one after another, during one) of the radiation fluxes the splitter and the second of them in the course of radiation optically coupled to the optical system, the second optical system, optical. connected to the beam splitter through the third mirror, and two modulators, one of which is mounted between the first and second mirrors and through the fourth mirror is optically connected to the first optical system, the second between the beam splitter and the third mirror and through the fifth the mirror is optically coupled to the second optical system, and each of the optical systems is made in 15 types of housing with an opening in the side wall and in the end, in which a mirror is placed sequentially one after the other along the optical axis of the system, located under glom to optical axis with a reflective coating to a hole in the side wall of the housing, a screen, a diffuse reflector, a spherical mirror with a hole in its center, a conical light guide mounted with an end face with a large diameter in the direction of the spherical mirror, a radiation receiver and a lens, installed in the hole in the end wall of the housing and optically coupled to the diffuse reflector, both optical systems are installed above the measurement object one before and the other after the area of the object on which the coating is applied. K block ffy FIG. 2 Editor I. Segl nick Compiled by V. Klimov Tehred M. Nadi Corrector I. Muska Order 11: 27/52. Circulation 671 Subscription VNISHI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, 4/5 Raushska nab. Branch PPP Patent, Uzhgorod, st. Project, 4