JPS62214334A - Surface flaw detector - Google Patents

Abstract

PURPOSE:To eliminate a secular change in the infrared detection sensitivity of a detector from affecting inspection and decision making even in case the secular change by comparing the detection signal of an infrared detector with a predetermined reference level and calibrating the gain of an amplifier according to the comparison result. CONSTITUTION:The detection signal of the infrared detector 1 composed of an infrared detecting element 2 and a lens 3 is amplified by am amplifier 4 whose gain is varied with an external signal and then the amplified signal is processed by a signal processor 5 to perform defect detection. A divider 6, on the other hand, receives the detection signal of the detector 1 and the preset reference level e0 is divided by its detection signal er. Then, the rate e0/er of the calibration of the initial gain G0 of the amplifier G0 based upon the division result is sent to a sensitivity setter 7. The gain Gr after the calibration which is obtained through the arithmetic operation of the setter 7 based upon a specific expression is sent to the amplifier 4, whose gain is calibrated. Thus, the gain of the amplifier 4 is controlled to obtain the same signal as that in case the infrared detection sensitivity is constant by the signal processor 5 even if the infrared detection sensitivity varies.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a surface defect detection device for detecting defects existing on the surface of steel products, such as billets, slabs, pipes, etc., on a production line for those products. It is.

[Conventional technology]

FIG. 4(a) is a diagram showing a conventional surface defect detection device disclosed in, for example, Japanese Unexamined Patent Publication No. 57-111437.
In the figure, αe is the material to be inspected, such as a slab.

(Iυ is a surface heater for heating the surface of the inspected material 4, and αη is an infrared scanner that scans and detects infrared rays emitted from the surface of the inspected material US.

Alternatively, it is a video processor that processes video signals from an infrared scanner.

The conventional surface defect detection device is constructed as described above.9 For example, when the surface of the inspected material 4 is heated with a surface heater I such as an induction heating device, concave flaws (cracks Ir5) existing on the surface of the inspected material αQ are detected. It is known that the temperature of a defective portion such as a convex portion or a convex portion (hege vlJ) is higher than that of the surrounding area because the thermal conduction state and thermal radiation state are different from those of a region where no defect exists. Therefore, defects are detected by scanning and imaging the surface of the inspected material (II) after surface heating with an infrared scanner, and processing the signal in the image processing unit 6 to detect areas with high signals, that is, areas with high temperature. It can be done.

Further, FIG. 4(b) is a diagram for explaining an infrared detector that is used in the infrared scanner η and detects infrared rays. In the figure, the infrared detector (1) has an infrared detection element (2) and a lens (3) that receives infrared rays, and the infrared rays radiated from the surface of the material to be inspected tte pass through the lens (3). It passes through and the above infrared detection element (2
) is detected.

Therefore, the video processing unit 6 or the infrared detector (1)
A defective portion has been detected by amplifying the detection signal obtained by the method and comparing it with, for example, a certain determination level.

[Problem that the invention seeks to solve]

FIG. 5 is an example of data detected by the infrared detector (1) on surface defects of the inspected material.

In the figure (a), P is a surface defect of the inspected material αQ.

The graph in (b) is an infrared detection signal when the surface of the material to be inspected +II is scanned in its longitudinal direction, that is, across the arrow direction, with the infrared detector (1), and the vertical axis of the graph is the received voltage; The horizontal axis is the signal detection position in the longitudinal direction of the roofing material ueO to be tested.

Signals r1 and r2 are both detected by the infrared detector (1).
This is an example of a detection signal obtained by

As mentioned above, the principle of surface defect detection is to utilize the fact that as a result of heating the surface of the material to be inspected, the temperature of the defective area becomes higher than that of the surrounding area due to differences in heat conduction and heat radiation conditions at the defective area. Therefore, the sensitivity of infrared rays in the defective part is higher than that in the surrounding part. Therefore, for example, when scanning the inspected material ae as shown in Fig. 5 (ta), the signal r1 as shown in (b)
Alternatively, the signal r2 has the highest received voltage at the defective part, and decreases as the distance from the defective part increases, and the received voltage is the lowest and flat in the part that is sufficiently removed from the defective part.

As shown in the same figure (C1), data, that is, signal r1 or signal r2, is amplified to a certain signal level, and the amplified signal, that is, signal rt/or signal r〆 is compared with a preset judgment level h, and a 1 judgment is made. A portion exceeding level h is determined to be defective.

On the other hand, in conventional surface defect detection equipment, sensitivity fluctuations may occur due to aging of the infrared detection element (2) itself inside the infrared detector (1) or changes in ambient temperature. Optical components such as the lens (3) installed in the light receiving port (1) are prone to various deposits, especially on the surface facing the outside world, and the scattering and absorption of light by these deposits can cause problems. 1) Because the sensitivity as an infrared detector + 1) may decrease,
The following problems were encountered.

That is, in FIG. 1(1)), the signals r1 and r2 are as follows.

and a detection signal corresponding to the first and second states.

Here, the second and second states are as described above.

Factors that affect the infrared detection sensitivity of the infrared detector (1+), that is, the ambient temperature of the infrared detection element (2),
Alternatively, it refers to a state in which the infrared detection sensitivities differ from each other due to things such as deposits on the surface of the optical components of the light receiving port.

Therefore, as shown in the figure, the signals r1 and r2 corresponding to the second and second state groups have totally different values from each other. Therefore, the signals r1 and r2 are amplified with a constant gain, resulting in signals rt/ and r2/.

If the judgment is made at the judgment level h, as shown in Figure 2.

From the signal r1/ corresponding to the first state, the defective part has a width d
, but the signal r2' corresponding to the second state is detected as
No defective parts are detected.

That is, because the infrared detection sensitivity of the infrared detector (1) has changed over time as described above, even though the same inclination of the material to be inspected is being inspected. However, the defect detection results differ from time to time, resulting in low reproducibility and reliability of inspection judgments or defect detection.

This invention was made in order to solve the above-mentioned problems, and even if the infrared detection sensitivity of the infrared detector (1) changes over time, the infrared detection sensitivity remains the same as when the infrared detection sensitivity is constant. The object of the present invention is to obtain a surface defect detection device in which a signal is obtained as an amplified signal of the detection signal of the infrared detector (11), and the inspection judgment is not affected by the infrared detection sensitivity of the infrared detector (1).

[Means for solving problems]

The surface defect detection device according to the present invention includes an amplifier that amplifies the detection signal of the infrared detector and whose gain can be changed by an external signal, and a device that allows the infrared detector to receive light when the material to be inspected is not being inspected. a reference infrared light emitter installed in the reference infrared light emitter, and the result of dividing the detection signal of the infrared rays of the reference infrared light emitter by the infrared detector by a predetermined reference level.

The sensitivity calibrator has a function of setting the gain after calibration of the amplifier based on the gain determined at the initial stage of the amplifier.

Or amplify the detection signal of the infrared detector.

In addition, an amplifier whose gain can be changed by an external signal is used, and when the material to be inspected is not being inspected, a sensitivity calibration test material having an artificial defect of a predetermined size is heated, and radiation from the sensitivity calibration test material is heated. Find the peak value of the infrared rays of the artificial defect, and divide the predetermined reference level by that peak value.
The apparatus further includes a sensitivity calibrator having a function of setting the calibrated gain of the amplifier based on the result and the initially determined gain of the amplifier.

Note that the means for causing the infrared detector to receive the infrared rays emitted by the reference infrared emitter is to transmit the infrared rays emitted by the reference infrared emitter either directly or by reflecting them on a reflector to propagate through the air.

Connecting an optical fiber to the reference infrared emitter.

Means is used to guide infrared rays to the light receiving aperture of the infrared detector using the optical fiber.

[Effect]

The surface defect detection device according to the present invention includes a reference infrared light emitter provided outside the front MD infrared detector.

By calibrating the gain of the amplifier based on the comparison result between the detection signal of the infrared radiation detector by the infrared detector and a predetermined reference level, infrared detection can be performed regardless of fluctuations in the infrared detection sensitivity of the infrared detector. A signal similar to that when the sensitivity is constant is sent as an output signal of the amplifier to a signal processor that processes the output signal and makes a test determination.

Alternatively, the surface defect detection device according to another invention includes a sensitivity calibration test material having an artificial defect of a predetermined size, and the infrared rays emitted from the artificial defect portion of the sensitivity calibration test material after heating are provided. By calibrating the gain of the amplifier based on the comparison result between the peak value of the detection signal by the detector and a predetermined reference level, infrared detection can be performed regardless of fluctuations in the infrared detection sensitivity of the infrared detector. A signal similar to that in the case of constant sensitivity is sent to the signal processor as the output signal of the amplifier.

〔Example〕

FIG. 1 shows an embodiment of a surface defect detection device which is a feature of the present invention. has been done. Further, (4) is an amplifier.

The detection signal of the infrared detector (11) is amplified, and the gain is changed depending on an external signal. (5) is a signal processor that processes the amplified signal of the amplifier (4),
Perform defect detection. On the other hand, (6) is a divider which receives the detection signal of the infrared detector +11 and divides a preset reference level by the detection signal, and (7)
is a sensitivity setting device, which sets an initial gain to the amplifier (4), calibrates the initial gain using the output signal of the divider (6), and applies the calibrated gain to the amplifier (4). Set. And (8) is a sensitivity calibrator, which is composed of the divider (6) and the sensitivity setter (7). (9
) is a controller that switches the operations of the sensitivity calibrator (8) and the signal processor (5) depending on whether the material to be inspected is being inspected or not. Note that qQ is a reference infrared light emitter (hereinafter simply referred to as a light emitter), υ is a surface heater, and a is a sensitivity calibration test material having an artificial defect of a predetermined size. Further, during the inspection, the gradient of the material to be inspected exists in place of the sensitivity calibration test material.

Therefore, by controlling the gain of the amplifier (4) according to the present invention), even if the infrared detection sensitivity fluctuates, the signal processor (5) can obtain the same signal as when the infrared detection sensitivity is constant. The method used will be described in detail below.

That is, let the detection signal at any time by the infrared detector (11) of the infrared rays emitted by the light emitter tIQ be er.

If the calibrated gain of the amplifier (4) is or, the sensitivity calibrator (8) sets the gain Gr so that the signal erGr resulting from the amplification of the detection signal er has a constant value.

Incidentally, the constant value is 9, for example, the following value is used. That is, the infrared detector (11) is in a predetermined controlled state, in other words, the ambient temperature of the infrared detecting element (2) is set to a certain temperature.

Let eO be the detection signal of the infrared rays emitted by the light emitter Q1 by the infrared detector (1) when the surface of the optical component such as the lens (3) of the light receiving port is in a predetermined initial state such that there is no deposit on the surface; Further, in this state, if the gain preset by the sensitivity calibrator (8) is GQ as the initial gain,
an initial gain G of the detection signal eo;

The amplified signal eOGO is set to the above-mentioned constant value.

That is, setting the amplified signal erGr of the infrared detection signal of the light emitter ill at any time to a constant value e OGG is expressed as follows.

θrGr ”” eOGO・・・・・・・・・・・・・
...fl) Therefore, based on equation (1), the gain or after calibration is expressed by the following equation.

Gr! GQ-・・・・・・・・・・・・・・・・・・
+21r In other words, the post-calibration gain Gr is obtained by multiplying the initial gain og by the ratio of the initial detection signal of the infrared rays emitted by the light emitter ul, that is, the reference level eo, and the detection signal er at any time. .

Therefore, when the gain calibration described above is applied to the operation of each part in FIG. 1, the reference level 6Q is preset as the dividend in the divider (6). Furthermore, with the detection signal er, the divider (6) outputs the reference level 1.
In equation (2), by dividing i1Q. The ratio (eo/er) to be calibrated to the initial gain Go is determined by the divider (6
) is sent to the sensitivity setting device (7). Then, the calculation of equation (2) is performed in the sensitivity setter (7) in which the initial gain GQ is set, and the gain or after calibration is determined by the sensitivity setter (7) and the amplifier (4). ) is set.

Note that the controller (9) does not operate the sensitivity calibrator (8) during the inspection of the material to be inspected, maintains the gain after previous calibration, and operates the signal processor (5); Conversely, when the material to be inspected is not being inspected, the sensitivity calibrator (8) is operated, and the signal processor (5) is not operated.

Note that the initial gain GQ is determined to be 1, for example, as follows. That is, after surface-heating the sensitivity calibration test material Ua having an artificial defect of a predetermined depth and width in advance, the detection signal of infrared rays radiated from the sensitivity calibration test material Ua by the infrared detector (1) is detected. After being amplified by the amplifier (4), the signal is amplified by the signal processor (5).

the gain of the amplifier (4) at the time when a certain determination level at which the predetermined width of the artificial defect is detected is determined in the signal processor (5) according to the depth of the artificial defect; Let be 0(,.

According to this embodiment, the sensitivity calibration test material α is used only when determining the initial gain GQ, and the sensitivity calibration test material α is used only when determining the initial gain GQ.
Since the infrared detection signal emitted by the light emitter (11) is used to calibrate the gain, the sensitivity calibration test material (ls5) is not necessary.

In this embodiment, a sensitivity calibrator (8) serving as a means for calibrating the gain of the amplifier (4) is used to calibrate the infrared detection signal er emitted by the light emitter a and a preset reference level eQ. A divider (6) for calculating the ratio and the initial gain G
Q and a sensitivity setting device (7) that calibrates and resets the gain from the output of the divider (6), that is, calculates the equation (2), is used, but the calibration that satisfies the equation (1) is used. Other circuit configurations that can determine the gain Gr for the detection signal er may also be used, and the same effects as in the ninth embodiment can be achieved.

Further, FIG. 2 shows another embodiment having the same effects as the above embodiment. That is, instead of the infrared rays emitted by the light emitter a, the surface heater Qυ was heated at any time not during the inspection. It uses a detection signal from the infrared detector (1) of the infrared rays of the artificial defect portion radiated from the sensitivity calibration test material a having an artificial defect of a predetermined size. Then, the divider (6) uses the peak value e detected by the peak hold circuit α in the divider (6).
), and the sensitivity setter (7) uses the output of the divider (6) to calculate the reference level eQ set to (2).
) is calculated to obtain the calibrated gain Gr of the amplifier (4).
Even if it is calculated, the same effect as in the embodiment described above can be obtained. In this case, first the infrared detector (1)
is maintained at the predetermined initial state described above, the initial gain GQ of the amplifier (4) is determined by the sensitivity calibration test material (2) at the same time as determining the judgment level of the signal processor (5). At the appointed time, at the same time.

In this state, the peak value of the infrared rays of the artificial defect part of the Sense 7JI calibration test material az is detected by the peak hold circuit αj, and the peak value is set as the reference level eo, and the divider (6) Set it as the dividend.

In this embodiment, the light emitter a0 used in the previous embodiment is not needed.

In addition, in the second embodiment, the lens (
3), but another optical component is provided in place of the lens (3) to allow the infrared detection element (2) installed inside the infrared detector (1) to receive light. Even in the case where there is an object, the same effects as in this embodiment can be obtained.

In addition, in the two embodiments, the position of the light emitter α1 is
G is on the opposite side from the infrared detector t1), but as shown in FIG. 3(a), the light emitter u
0 is outside the infrared detector (11), and.

Even in other positions, the emitted light from the light emitter H may be reflected using the reflecting mirror I and received by the infrared detector (1), and the same effects as in the two embodiments can be achieved.

In this case, there is an advantage that the light emitting device α can be installed in a position with favorable installation conditions such as easy maintenance, rather than being placed below the object to be inspected US as in the present embodiment.

In addition, in this embodiment, as a means for causing the infrared detector (1) to receive light from the light emitter Q(I), the emitted light from the light emitter α propagates through the air and is directly transmitted to the infrared detector (1).
2. For example, as shown in FIG. 3(b), the light emitter σ1 is installed at an arbitrary location and the optical fiber (15 is connected to the light emitting device σ1). Vessel 01
Even if the optical fiber is connected to the infrared detector (1) and the light from the light emitter Ql is guided through the optical fiber <15, the same effect as in the embodiment described above can be obtained.

In this case, there is an advantage that the light emitting device can be installed in a position with good installation conditions such as easier maintenance than in the above two embodiments.

It goes without saying that the reflection m (141) is unnecessary.

〔Effect of the invention〕

As described above, according to the present invention, the detection signal by the infrared detector of the infrared rays emitted by the reference infrared emitter or the infrared rays radiated after heating the sensitivity calibration test material having an artificial defect of a predetermined size is used. Since the gain of the amplifier is calibrated based on the comparison result with a preset reference level, the same signal as when the infrared detection sensitivity of the infrared detector is constant is generated regardless of fluctuations in the infrared detection sensitivity of the infrared detector. Since it is sent to the signal processor as an output signal, it has the effect of improving the reliability of inspection judgment or defect detection.

[Brief explanation of drawings]

FIG. 1 shows a surface defect detection device according to one embodiment of the present invention, FIGS. 2 and 3 show surface defect detection devices according to other embodiments of the invention, and FIG. 4 shows a conventional surface defect detection device. FIG. 5 is a diagram showing a defect detection device, and is a diagram for explaining problems in the conventional surface defect detection device. In the figure, (1) is an infrared detector, and (4) is an amplifier. (5) is a signal processor, (8) is a sensitivity calibrator, and (9) is a controller. +1 (I is the reference infrared light emitter, aυ is the surface heater, Sumino is the sensitivity calibration test material, Q41 is the reflector, and Kasumi is the optical fiber. In Figure 1, the same symbols indicate the same or equivalent parts.

Claims (5)

[Claims] (1) A surface heater that heats the inspected material, an infrared detector that receives infrared rays emitted from the heated surface of the inspected material and converts it into an electrical signal, and amplifies the electrical signal of the infrared detector. , and an amplifier whose gain can be changed by an external signal, and connected to the output of the amplifier,
a signal processor that processes the amplified signal of the infrared detector detected by the amplifier to make an inspection determination; and a reference infrared light emitter installed so that the infrared detector can receive the light when the material to be inspected is not being inspected. , setting an initial gain in the amplifier, and calculating a calibrated gain of the amplifier using a comparison between a detection signal of the infrared rays from the reference infrared light emitter by the infrared detector and a predetermined reference level; The sensitivity calibrator is reset to the amplifier, the sensitivity calibrator is not operated during inspection of the material to be inspected to maintain the previously calibrated gain, and the signal processor is operated, while the inspection target is not being inspected. and a controller having a function of switching the sensitivity calibrator to operate and the signal processor to disable the operation. (2) As a method for causing the infrared detector to receive light from the reference infrared light emitter, the reference infrared light emitter is placed on an optical path where the infrared detector can receive light and at a position where light can be received when there is no material to be inspected. claim 1, in which the radiation light of the reference infrared emitter is propagated through the air and reaches the light receiving port of the infrared detector when there is no material to be inspected.
) The surface defect detection device described in item 2. (3) As a method for causing the infrared detector to receive the reference infrared emitter, in addition to the reference infrared emitter, one or more reflecting mirrors are provided outside the infrared detector;
The surface defect detection device according to claim 1, wherein the light emitted from the reference infrared light emitter is reflected by the reflector once or multiple times and reaches the light receiving port of the infrared detector. (4) As a method for causing the infrared detector to receive light from the reference infrared emitter, an optical fiber is connected to the reference infrared emitter, and the optical fiber is connected from the reference infrared emitter to the light receiving port of the infrared detector. A surface defect detection device according to claim 1, which guides light. (5) A surface heater that heats the inspected material, an infrared detector that receives infrared rays radiated from the heated surface of the inspected material and converts it into an electrical signal, and amplifies the electrical signal of the infrared detector. , and an amplifier whose gain can be changed by an external signal, and connected to the output of the amplifier,
a signal processor that processes an amplified signal of the detection signal of the infrared detector by the amplifier to make an inspection determination; a sensitivity calibration test material having an artificial defect of a predetermined size; and setting an initial gain to the amplifier; The peak value of infrared rays radiated from the sensitivity calibration test material heated by the surface heater is detected, and the calibrated gain of the amplifier is determined by comparing the peak value with a predetermined reference level. a sensitivity calibrator for calculating and resetting in the amplifier; and a sensitivity calibrator for not operating the sensitivity calibrator during inspection of a material to be inspected to maintain the previously calibrated gain of the amplifier; and a controller having a function of operating the sensitivity calibrator and disabling the signal processor when a material to be inspected is not being inspected.