JPH03120406A - Optical tube internal diameter measuring instrument - Google Patents

Abstract

PURPOSE:To easily perform inspection in a tube and measure its internal diame ter by irradiating the internal wall of the tube with a light beam, guiding the scattered light into a photodetector which has plural photodetecting elements through a condenser lens, and specifying the generation position of the scattered light according to light intensity values detected by the respective elements. CONSTITUTION:Laser light emitted by a semiconductor laser 11 is bent by 90 deg. through a reflecting mirror 21 to irradiate the wall surface in the tube 10 almost perpendicularly. The laser light irradiating the inside of the tube 10 is reflected by its wall surface and part of the scattered light is reaches a two-divided concentric photodetecting element 27 through the condenser lens 25. The outputs of the respective detecting elements of the element 27 are sent out to a condenser lens movement quantity detection part 29. The detection part 29 detects the quantity of vertical movement of the condenser lens when the difference between the two light intensity values becomes zero and feeds a corresponding control signal back to a driving part 31. The driving part 31 moves the condenser lens 25 to a position corresponding to the control signal. The internal diameter of the tube 10 can be found from the control signal sent out of the detection part 29 to the driving part 31.

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.

Pipes installed underground in cities or inside buildings are
It was customary not to inspect the internal situation unless there was some kind of problem. This is because there was no testing method,
Another reason for this was that the inspection itself was not cost-effective, and in-service inspections were carried out only when a failure occurred to investigate the cause and determine whether repairs were possible.

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 would be large-scale and the processing time would be long. Therefore, inspectors must monitor the monitor screen directly and identify the type of defect and the degree of need for repair each time. 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.

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 parallel light beam; the parallel light beam is focused through an objective lens; and further reflected by a rotating reflecting mirror. A light beam irradiation unit that irradiates a focused light beam onto the inner wall of the tube at a predetermined angle, and a movable condensing lens that directs light scattered on the inner wall of the tube according to the irradiation of the focused light beam. The light is captured in a photodetector having a plurality of photodetecting elements, and a condensing lens is moved to a predetermined position according to the intensity of light detected by each photodetecting element, and the amount of this movement is adjusted according to the amount of variation in the inner diameter of the tube. and an inner diameter variation detection section that detects the variation amount as a value.

[For production]

In the present invention, the inner wall of a tube is irradiated with a light beam focused at a predetermined angle, and the light scattered on the inner wall is taken into a photodetector having a plurality of photodetecting elements via a condensing lens. The inner diameter variation detecting section including this photodetector specifies the ordered position of scattered light according to the light intensity detected by each photodetector element.

That is, the generation position of the scattered light changes according to the change in the inner diameter of the tube, but the light intensity detected by each photodetection element of the photodetector also changes accordingly. In the present invention, the amount of movement of the condensing lens that condenses scattered light is controlled so that the light intensity detected by each photodetecting element has a predetermined distribution. therefore,
The amount of movement of the condensing lens corresponds to the position where the scattered light is generated, and the inner diameter of the tube can be measured using the amount of movement of the condensing lens.

〔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 objective lens 17
The light is condensed by a reflecting mirror 21 attached to a mirror rotation motor 19 and bent in a 90 degree direction, and is irradiated almost perpendicularly to the wall surface inside the tube 10 .

The laser light irradiated into the tube 10 is reflected by its wall surface, and most of the light is reflected from the reflecting mirror 21 in the opposite direction.

- A part of the scattered light is reflected by a reflection mirror 23 attached to a mirror rotation motor 19 and rotated in synchronization with the reflection mirror 21, and is transmitted through a condensing lens 25 into two concentric circular cane beams. It reaches the detection element 27.

The output of each detection element of the two-divided concentric photodetection element 27 is
It is sent to the condensing lens movement amount detection section 29. The condensing lens movement amount detection unit 29 detects the vertical movement amount of the condensing lens 25 at which the difference between the two light intensities becomes zero, and feeds back a corresponding control signal to the driving unit 31. The drive unit 31 moves the condensing lens 25 to a position according to the control signal.

Here, since the two-split concentric photodetecting element 27 is constituted by each concentric photodetecting element, the dividing point (
There are two border points in the direction of movement of the condensing lens 25, and the detection results of both the light detection elements at each dividing point are opposite to the direction of movement of the condensing lens 25.

Therefore, the scattered light incident on the 22-divided concentric light detection element 27 via the condensing lens 25 is detected only at one of the dividing points, so that the movement control direction of the condensing lens 25 is not confused. A shielding plate 33 that rotates in synchronization with the reflecting mirror 23 is provided between the reflecting mirror 23 and the condensing lens 25. In this embodiment, the shielding plate 33 is provided so that the detection position of the scattered light is on the opposite side of the rotation axis of the reflection mirror 23 from the wall surface onto which the light beam is irradiated.

Further, the numerical aperture NA of the objective lens 17 (Numeri
calAperture, 1/F) is 0.
By setting the depth of focus to be as low as about 1 to 0.3 and widening the depth of focus as much as possible, it is possible to expand the detection range of inner diameter fluctuations.

Note that the diameter and NA of the objective lens 17 are selected depending on the inner diameter of the tube to be measured.

Generally, the inner diameter of the tube 10 is normally narrower than the original inner diameter, and if the position of the condenser lens 25 is set according to the original inner diameter of the tube 10, in the configuration of this embodiment, Where the inner diameter is narrow, most of the scattered light is detected by the outer photodetector of the two-split concentric photodetector 27,
The condensing lens movement amount detection unit 29 can determine that the scattered light is shifted downward according to each detection signal. Therefore, the condensing lens movement amount detecting section 29 moves the condensing lens 25 upward relative to the driving section 31, and performs control so that the difference between the light intensities detected by each photodetecting element becomes zero. do.

The amount of movement of the condensing lens 25 corresponds to the amount of variation in the position where the scattered light is generated, that is, the inner diameter of the tube lO, and there is a predetermined linear relationship between the amount of movement of the condensing lens 25 and the amount of variation in the inner diameter of the tube. The inner diameter of the tube 10 can be determined from the control signal (the amount of movement of the condenser lens 25) sent from the condenser lens movement amount detection section 29 to the drive section 31.

The inner diameter of the tube 10 can be measured by inserting the measuring device into the tube, driving the motor 19 to rotate the reflecting mirrors 21 and 23, and scanning the emitted light beam along the inner wall of the tube 10. The inner diameter of the tube IO is determined from the amount of movement of the condenser lens 25, which is controlled in accordance with variations in the inner diameter of the tube 10.

FIG. 2 is a diagram showing the results of actually measuring the inner diameter of the pipe IO using the apparatus of the present invention.

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

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 detects scattered light of a light beam irradiated on the inner wall of a tube with a photodetector having a plurality of photodetecting elements through a condensing lens, and detects the detection results of each photodetecting element. The position of the scattered light is determined according to the amount of movement of the condensing lens used.
That is, since the amount of variation in the inner wall of the tube can be specified, data on the inner diameter of the tube can be efficiently collected.

In addition, the device of the present invention can be easily made smaller and lighter, has low power consumption, and is excellent in repeatability, so it can easily and easily measure the inner diameter of a pipe with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main configuration of an embodiment of the present invention. FIG. 2 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...Objective lens, 19...Motor, 21.23.
...Reflection mirror, 25...Condensing lens, 27...2
Divided concentric light detection element, 29... Condensing lens movement amount detection section, 31... Drive section, 33... Shielding plate. −～

Claims (1)

[Claims] (1) a light source unit that beam-shapes the laser light output from the semiconductor laser and further emits it as a parallel light beam; a light source unit that focuses the parallel light beam through an objective lens and further reflects it on a rotating reflecting mirror; A light beam irradiation unit that irradiates a focused light beam onto the inner wall of the tube at a predetermined angle, and a movable condenser lens that directs light scattered on the inner wall of the tube according to the irradiation of the focused light beam. The condenser lens is moved to a predetermined position according to the intensity of light detected by each photodetection element, and the amount of movement is calculated as the amount of variation in the inner diameter of the tube. 1. An optical pipe inner diameter measuring device comprising: an inner diameter variation detecting section that detects a value according to the inner diameter.