JPH03115912A - Optically measuring instrument for internal diameter of tube - Google Patents

Abstract

PURPOSE:To easily measure the internal diameter of a tube with high accuracy by detecting a focus position according to the shape of a light beam being received, and finding the controlled variable of a driving means, and detecting the quantity of variation in the internal diameter of the tube. CONSTITUTION:This instrument is equipped with a light source part 11 which emits a circular polarized parallel light beam, a light beam scanning part which scans the internal wall of the tube 10, and a focus position detection part 37 which finds the controlled variable of the driving means 39 and detects the extent of variation in the internal diameter of the tube 10. The light beam scanning part converts a parallel light beam into a divergent light beam, which is converged on the internal wall of the tube 10 through an objective 23 at a focus position set by the driving means 39 and a reflecting mirror 25. Therefore, when the focus position of the objective 23 is shifted as the internal wall of the tube 10 varies, the divergent light beam is used, so the detection range of the focus position can easily be expanded greatly. Consequently, inspection in the tube 10 is easily performed and the internal diameter of the tube can be measured effectively.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an optical pipe inner diameter measurement method used to measure the inner diameter of small diameter pipes or steel pipes that cannot be inspected by humans, and to inspect the inner wall condition of the pipes. Regarding equipment.

Underneath cities or inside buildings, there are numerous pipes for transmitting gas, water, electricity, or communications. Once these piping installations were completed, it was customary not to inspect their internal conditions unless there was some kind of failure. This is because there was no inspection method available, and the inspection itself was not cost-effective.When a failure occurs, an in-service inspection is conducted to investigate the cause and determine whether repairs are possible. Ta.

The optical pipe inner diameter measuring device of the present invention is used, for example, for constructing a life database of installed pipes.

[Conventional technology]

Conventional pipe inspection equipment uses a small television camera, which is inserted into the pipe, and an inspector observes the condition of the pipe's inner wall surface as an image. this is,
This is because the image data obtained is image information, and the amount of information is enormous. In other words, in order to detect the presence or absence of a fault through data processing, the processing equipment is large-scale and the processing time is long. This is because it is easier to judge the possibility and take appropriate measures.

[Problem to be solved by the invention]

On the other hand, there has been a conventional method of irradiating a flat object with laser light and measuring distance using the reflected light.
The light source and its detection system had to be fixed for wiring reasons. Therefore, it was not suitable as a device that rotates by itself and measures the inner diameter from the inside of the tube.

Furthermore, although the optical head used in the optical disk has a highly accurate self-focus detection control mechanism, it is configured to move the lens itself by the same amount as the amount of change in the focal position. this is,
Since the laser beam was first converted into parallel light and focused using an objective lens, the focus positioning performance reached the micrometer order range, but it was not able to cover a relatively wide area. Ta. That is,
This self-focus detection control mechanism has an excellent ability to detect a focus position, but its detection range is several mm at most.

On the other hand, in order to inspect the inside of pipes installed underground or in buildings, there is a need for a pipe inner diameter measurement mechanism that is capable of detecting variations in the pipe inner diameter of several centimeters and has high workability. There is. In the optical head's self-focus detection control mechanism,
It was impossible to follow the large amount of variation in the inner diameter inside the pipe.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pipe inner diameter measuring device that can easily and easily inspect the inside of a pipe and effectively measure the pipe inner diameter.

[Means to solve the problem]

The present invention includes a light source unit that beam-shapes laser light output from a semiconductor laser and emits it as a circularly polarized parallel light beam, and a focal point that converts the parallel light beam into a spread light beam and that is set by a driving means. A light beam scanning section that scans the inner wall of the tube by reflecting the light beam emitted through the objective lens on a rotating reflecting mirror, and a light beam scanning section that captures the light beam reflected on the inner wall of the tube and receives it through a cylindrical lens. The focus position detecting section detects the focal position according to the shape of the light beam, determines the control amount of the driving means, and detects the amount of change in the inner diameter of the tube.

[For production]

The present invention converts a parallel light beam into a spread light beam in a light beam scanning section, and focuses the light beam on the inner wall of a tube via an objective lens and a reflection mirror located at a focal position set by a driving means. let Therefore, when changing the focal position of the objective lens in accordance with changes in the inner diameter of the tube, since a spread light beam is used, the amount of movement of the objective lens is reduced relative to the amount of change in the inner diameter of the tube. can do. That is, it is easy to greatly expand the detection range of the focal position.

Although it is inevitable that the focus positioning accuracy will decrease as the detection range of the focus position expands, a measurement accuracy of about 0.1 mm is sufficient for the purpose of internal inspection of the tube, and this can be easily achieved with the configuration of the present invention. This is possible.

Furthermore, the focal position detection section of the present invention is configured to detect the focal position of the objective lens and perform feedback control according to the shape of the light beam received through the cylindrical lens, and the amount of movement of the objective lens is The inner diameter of the tube is measured by utilizing the fact that the value corresponds to the amount of variation in the inner diameter of the tube.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing the main configuration of an embodiment of the present invention.

In the figure, reference numeral 10 indicates a partial cross section of the tube. The laser beam emitted from the semiconductor laser 11 is shaped by a beam shaping prism 13 from an ellipse to a circle.
The collimator lens 15 converts the light into parallel light, and the light is incident on the quarter-wave plate 19 via the polarizing beam splitter 17 . 1
The /4 wavelength plate 19 converts the laser beam, which has been beam-shaped into parallel light, from linearly polarized light to circularly polarized light. The emitted light is condensed by a condenser lens 21, further reflected by a reflection mirror 25 via an objective lens 23, and condensed onto a wall surface inside the tube 10.

Note that the reflecting mirror 25 has a structure in which it is rotated by being held on the rotating shaft of a rotating motor 27, and the reflected light is transmitted to the tube 10.
The light is irradiated along the inner circumference of the Therefore, by converting the laser beam into circularly polarized light using the quarter-wave plate 19,
The amount of light beam irradiated along the inner periphery of the tube 10 can be made constant in the circumferential direction, and data correction depending on the orientation can be made unnecessary.

The light reflected by the wall surface of the tube 10 enters the quarter-wave plate 19 again via the reflection mirror 25, objective lens 23, and condensing lens 21. The quarter-wave plate 19 converts the circularly polarized light into linearly polarized light, and the emitted light is reflected by the polarizing beam splitter 17 and reaches the light receiving system 29 .

The light receiving system 29 is composed of a cylindrical lens 3, a condensing lens 33, and a four-part light detection element 35. Each detection element of the four-divided light detection element 35 detects a light intensity according to the focal position of the objective lens 23, and each detection output is sent to the focal position deviation amount detection section 37. The focal position deviation amount detection unit 37 detects the deviation amount of the focal position of the objective lens 23 from the difference in light intensity in four directions, feeds back a corresponding control signal to the drive system 39 of the objective lens 23, and to the corresponding focal position. The drive system 39 is
It is composed of a magnetic coil 41, a magnet 43, and a spring 45 that holds the objective lens 23.

FIG. 2 is a diagram illustrating the principle of detecting the amount of shift in the focal position of the objective lens 23 from the difference in light intensity in four directions in the four-division light detection element 35.

The light reflected on the wall of the tube 10 passes through the cylindrical lens 31
By receiving light through the

The focal position of the objective lens 23 changes depending on each direction in the y direction. The shape of the light beam detected by the 4-split photodetecting element 35 is an ellipse whose long sleeve direction differs by 90 degrees at each focal position corresponding to each direction (Fig. 2 (1), (3)).
), and the center of each focal position (hereinafter referred to as "automatically controlled focal position") forms a circle (FIG. 2 (2)).

Here, as shown in FIG. 2, by tilting the installation position of the 4-split photodetecting element 35 by 45 degrees, the objective lens 23 for the automatically controlled focal position can obtain a circular beam shape.
The amount of deviation can be detected. That is, the 4-split photodetecting element 3
As shown in Figure 2, the detection elements of 5 are A, B, C, and D, and the respective detected light intensities are a, b, c, and d, then s = (a + c) - (b + d) The difference signal S defined by is zero when the objective lens 23 is at the automatically controlled focal position, so the difference signal S when an elliptical beam shape is obtained is the amount of deviation from the automatically controlled focal position. (focal position shift amount).

In the case of FIG. 2(a), s>0, and it can be said that the position of the objective lens 23 is on the tube 10 side (closer to) the automatically controlled focal position. In addition, in the case of Fig. 2 (C), s
<O, and it can be said that the position of the objective lens 23 is on the opposite side (far away) from the tube 10 with respect to the automatically controlled focal position.

FIG. 3 is a diagram showing the measurement results of the difference signal S with respect to the position of the objective lens 23. The horizontal axis shows the position of the objective lens 23, and the vertical axis shows the difference signal S.

The positions of the objective lens 23 corresponding to each peak of the difference signal S are respective focal positions corresponding to the x and y directions of the cylindrical lens 31, and an automatic control focal position M at which the difference signal S becomes zero is located at the center thereof. be.

The focus position deviation amount detection unit 37 detects the difference in light intensity (difference signal S) of each detection element of the four-divided light detection element 35, and moves the objective lens until the automatically controlled focus position M at which the difference signal S becomes zero. 23 is determined, and a control signal corresponding to the value is fed back to the drive system 39.

Although there is no linear relationship as a whole between the difference signal S and the position of the objective lens 23, it can be seen that there is a nearly linear relationship within a minute section between the automatically controlled focal position M, as shown in FIG. It is possible. Therefore, the servo mechanism composed of the light receiving system 29, the focal position shift amount detection section 37, and the drive system 39 is not affected at all.

With this configuration, the position of the objective lens 23 is adjusted to the automatically controlled focal position M in accordance with changes in the inner diameter of the tube 10. That is, if the position of the objective lens 23 is set in advance to the automatically controlled focal position (point N in FIG. 3) that matches the original inner diameter of the tube 10, the change (decrease) in the inner diameter will be reflected by the difference signal S,
The amount of movement Δd of the objective lens 23 to the automatic control focus position M that makes the difference signal SI zero is determined, and feedback is applied to the drive system 39 accordingly.

The present invention utilizes the fact that the amount of movement Δd of the objective lens 23 corresponds to the amount of change in the inner diameter, and uses a control signal fed back from the focus position deviation amount detection unit 37 to the drive system 39 to Detects the amount of deformation with respect to the original inner diameter.

The inner diameter of the tube 10 can be measured by inserting this measuring device into the tube, driving the motor 27 to rotate the reflecting mirror 25, and
This is done by scanning the emitted light beam along the inner wall of the tube 10. That is, the objective lens 23 automatically moves to the automatically controlled focal position, but as shown above, the position of the objective lens 23 can be determined from the amount of movement, and since the position of the reflecting mirror 25 is constant, it can be moved from its rotation axis. The focal distance of the inner wall is calculated and the inner diameter of the tube IO can be determined.

FIG. 4 is a diagram showing the results of actually measuring the inner diameter of the tube 10 using the apparatus of the present invention.

The thin line shows the original inner diameter of the tube IO, and the thick line shows the measured inner diameter of the tube 10.

In addition, the device of the present invention can sequentially (in a spiral) detect changes in the inner diameter of a tube in the longitudinal direction by being mounted on a robot or other device that can self-propel inside the tube, or by inserting the device into the tube. By synchronizing the movement of the tube with the scan period inside the tube, the position of the wall surface that has been deformed due to corrosion or other causes can be easily determined.

Further, since the device of the present invention can be operated with small electric power, electric power from a battery or the like is sufficient.

Information regarding the inner diameter of the pipe is transmitted using spatial propagation using radio waves or light, received by a receiver installed at a predetermined position of the pipe (for example, a manhole), and then sent to a microcomputer or other device connected to the receiver. By processing the information using , it is possible to display it on a display as visible information.

〔Effect of the invention〕

As described above, the present invention makes it possible to reduce the amount of variation in the focal position, that is, the amount of movement of the objective lens, compared to the amount of variation in the inner diameter of the tube, so that high-speed scanning of the light beam against the inner wall of the tube is possible. Therefore, it is possible to efficiently collect data on the inner diameter of the tube, which is measured in accordance with the amount of movement of the objective lens. Furthermore, by reducing the weight of the objective lens, dynamic followability can be improved.

Furthermore, the device of the present invention is easy to downsize and lightweight, and has excellent operability, making it possible to easily and easily measure the inner diameter of a pipe with high precision.

By installing the device of the present invention, for example, at the tip of a pipe repair robot, it becomes easy to determine the method and time for repair, and it is possible to carry out effective and systematic repair work.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main configuration of an embodiment of the present invention. FIG. 2 is a diagram illustrating the principle of detecting the amount of focal position shift of an objective lens. FIG. 3 is a diagram showing the measurement results of the difference signal S with respect to the position of the objective lens. FIG. 4 is a diagram showing the results of actually measuring the inner diameter of a tube using the apparatus of the present invention. DESCRIPTION OF SYMBOLS 10... Tube, 11... Semiconductor laser, 13... Beam shaping prism, 15... Collimator lens, 1
7... Polarizing beam splitter, 19... 1/4 wavelength plate, 21... Condensing lens, 23... Objective lens, 2
5... Reflection mirror, 27... Motor, 29... Light receiving system, 31... Cylindrical lens, 33... Condenser lens, 35... 4-split light detection element, 37... Focal point Positional deviation amount detection unit, 39... Drive system, 41... Magnetic coil, 43... Magnet, 45... Spring.

Claims (1)

[Claims] (1) A light source unit that beam-shapes the laser light output from the semiconductor laser and emits it as a circularly polarized parallel light beam, and a focal point that converts the parallel light beam into a spread light beam and is set by a driving means. a light beam scanning section that scans the inner wall of the tube by reflecting the light beam emitted through the objective lens on a rotating reflecting mirror; An optical system comprising: a focal position detection section that detects the focal position according to the shape of the received light beam, determines the control amount of the driving means, and detects the amount of change in the inner diameter of the tube. Type pipe inner diameter measuring device.