JPS5918409A - Device for inspecting surface of red hot material - Google Patents

Abstract

PURPOSE:To detect the presence of flaws positively and readily, by utilizing regular reflected light which is sufficiently higher than the light reflected by the surface of a body to be inspected, and detecting the edge part of the flaw. CONSTITUTION:When parallel light is made to radiate on a body to be inspected 3 from a lighting device 1, the incident light is reflected by the surface of the body to be inspected 3. Said reflected light is inputted to a one dimensional image pickup device 2, and the surface image of the body to be inspected 3 is formed by a lens system. The reflected light, which is higher than the reflection by the surface of the body to be inspected 3, is detected based on the photoelectric output from the one dimensional image pickup device 2 by an edge detecting part 4. A flaw detecting part 5 detects the reflected light, which is lower than the level of the light reflected by the surface of the body to be inspected 3 and appears following the level of the high reflected light in a time series, based on the output of the edge detecting part 4.

Description

[Detailed description of the invention] 2,,,,.

INDUSTRIAL APPLICATION FIELD The present invention relates to a surface inspection device for detecting cracks in a red-hot object that does not have metallic luster and has a rough surface.

Conventional configuration and its problems Conventionally, the surface inspection method for a red-hot object (for example, a hot steel slab) with mutually compatible planes was to irradiate the red-hot object with light and convert the reflected light into an electrical signal at the light receiving part. However, a method of level detection is generally used. In this method, in order to remove specular reflection components from the illumination device, it is common to make a certain angle between the direction of light irradiation and the optical axis of the detector installed in the light receiving section. However, the photoelectric signal changes greatly depending on the surface condition of a red-hot object (hereinafter referred to as a test object) having a rough surface, and a difference occurs in the photoelectric signal level depending on the position on the test object. That is, a in Figure 1
An object to be inspected with a surface as shown in (with cracks C)
When detected, a photoelectric signal as shown in FIG. 1 is obtained. Figure 1: If the object to be tested has large irregularities, the signal level will change significantly.3 If the surface is not flat, the signal level will decrease. As a result, the flaws existing on the surface of the object to be inspected (Fig. 1a)
I may fall within the above-mentioned fluctuation of the photoelectric signal level, making it impossible to detect flaws. For example, in Fig. 1b, if the photoelectric signal of b is binarized at the threshold level of ■1, a signal like C is obtained, and the part other than the flaw (1v part in Fig. 1) (11 or C in Fig. 1) is obtained. 1110) will also be detected as a flaw, and if it is still detected at the threshold level of v2, the flaw cannot be detected.

OBJECTS OF THE INVENTION The present invention takes into consideration the above-mentioned drawbacks of the conventional techniques, and aims to provide an apparatus that accurately detects surface flaws on an object to be inspected.

Structure of the Invention In order to achieve the above object, the present invention provides a unidirectional illumination device that illuminates a red-hot object from one direction, and a unidirectional illumination device that illuminates a red-hot object from one direction, and a unidirectional illumination device that illuminates the illumination device so as not to receive specularly reflected light from the illumination device. A one-dimensional imaging device that images the surface of a red-hot object and starts scanning from the side opposite to the irradiation direction of the illumination device, which is arranged with the direction and detection optical axis shifted; There is an edge detection section that detects reflected light that is higher than that reflected from the object, and the level of reflected light from the surface of a red-hot object, which continuously increases in time series based on the output of the edge detection section. This is a red-hot object surface inspection device consisting of a flaw inspection section that detects low reflected light.

DESCRIPTION OF EXAMPLES Hereinafter, the present invention will be explained based on examples. However, in the following description, it is assumed that the center of the irradiation optical axis from the illumination device and the scanning line of the one-dimensional imaging device are on the same plane, and the irradiation light is parallel light.

The configuration of the present invention is shown in FIG. The present invention includes a lighting device 1;
It consists of an object to be inspected 3, a one-dimensional imaging device 2, an edge detection section 4, and a flaw inspection section 5. Here, the -dimensional imaging device has a scanning function, and a combination of a linear image sensor and a lens system can be used.
In other words, the order of detection on the object to be detected is such that it starts from the side opposite to the illumination device 1. (The direction shown by the arrow in FIG. 2) Next, the detection operation will be explained. From illumination device 1 to test object 3
When parallel light is irradiated onto the object at an angle of incidence θ, the incident light is
reflected from the surface of Incident angle: 0, generally 30° to 60°
This reflected light having a range of 2 is incident on a one-dimensional imaging device 3 installed in a direction perpendicular to the plane of the object 3 to be inspected, and a surface image of the object 2 is formed by a lens system. If the surface of the object 3 to be inspected is rough, the light is diffusely reflected on the surface of the object 30 to be inspected, and the photoelectric signal from the one-dimensional imaging device 3 fluctuates irregularly as shown in FIG. 3a. The fluctuation state of this signal depends on the surface condition of the object being tested, but for example, in the case of a hot iron-steel slab, +
It shows a fluctuation range of about 30%.

Therefore, if there is a crack on the surface of the object to be inspected 3 as shown in 1 in Fig. 1a, the photoelectric signal detected by the -dimensional imaging device 2 is a result of the reflected light from the surface as shown in Fig. 3. The flaw signal is superimposed on the photoelectric signal. Further, to explain in detail the reflected light from the flawed part, the light incident on the surface of the object to be inspected is diffusely reflected as shown by the cross-section ho in Fig. 4, whereas the light reflected from the flawed part is diffusely reflected.

The light incident on the concave portion of the flaw (shown as C in FIG. 4) is diffusely reflected inside the flaw, and a portion of the light is incident on the one-dimensional imaging device 2. As a result, the signal level of the flawed portion becomes slightly lower than that of the light reflected from the surface, as shown in FIG.

On the other hand, in the present invention, as described above, light is irradiated from the opposite direction to the scanning direction of the one-dimensional imaging device.

As a result, as shown in Fig. 4, among the edges of the flaw, the light from the edge part on the irradiation direction side (shown as the mouth in Fig. 4) is reflected by the surface of the object to be inspected 3, and its specular reflection component is primary It does not enter the original imaging device 2. However, on the edge surface on the opposite side to the irradiation direction, a condition is established for specularly reflected light to enter the -dimensional imaging device 2.

This specular reflection light level (shown in Figure 4-2) is
shows a larger value than the level of diffuse reflection from the surface. Therefore, as shown in FIG. 3, in the photoelectric signal obtained from the -dimensional imaging device 2, a flaw signal appears following an edge signal in a specular reflection state in the scanning direction.

Next, a method for detecting and processing flaws from the photoelectric signals detected by the one-dimensional imaging device 2 will be described. A specific example of the edge detection section 4 and width detection section 5 is shown in FIG.

The edge detection section 4 includes a comparator 4a and a reference voltage v3 generation section 4b. Here, the reference voltage v3 generating section 4
The reference voltage 3 of b is set to be sufficiently high compared to the level of diffusely reflected light from the surface of the object to be inspected 3 so as to detect only the flaw edge signal. Binarize the signal using the reference voltage ■3, and as a result, the third
As shown in Figure C, only the edge signal in front of the flaw is detected on the object to be inspected in the scanning direction.

The defect detection section 6 includes a comparator 6a, a reference voltage 4 generation section 5b, an R-S flip-flop 5C, and an oscillation section 5.
θ, an AND gate 5d, a counter 6f, a criterion section 6q, and a comparator 6h. Here R-
The S Philip flop is set manually by S priority type, and the reference voltage v4 of the reference voltage v4 generating section 6b is set to a voltage that can sufficiently separate the level of reflected light from the surface of the object to be inspected and the level of reflected light from the flawed portion. -1, the oscillation frequency of the oscillation unit 6q is selected to a value that can sufficiently open the minimum width of the flaw to be detected, and is generally set to a frequency equivalent to the scanning frequency of a one-dimensional imaging device. In the defect detection section 6, the photoelectric signal from the -dimensional imaging device 2 is first binarized using a reference voltage 4 to obtain the signal shown in FIG. 3d. As mentioned above, since the photoelectric signal level changes depending on the surface condition of the object to be inspected, signals other than flaws (dV in FIG. 3) are also detected here. Next, R-S Philip 7
The 0-tube 5c receives a signal from the edge detection section 4, and if there is an edge signal, sets the R-S Philip at the falling edge of the signal, and resets it at the rising edge of the output from the comparator 5a. As a result, as shown in FIG. 3e, the output Q of the R-S flip-flop 5C is detected as a signal below the reference voltage v4 that follows the flaw edge signal, that is, only a flaw signal, which indicates the surface condition of the object to be inspected. Signals other than flaws such as fluctuations (shown as dV in Figure 3) caused by -) 6d, and a signal as shown in FIG. 3q is obtained.

The output from the anti-game) 5d is sent to a counter 5f that counts the width of the flaw, and the width of the flaw is determined. Then, the reference value set in advance in the judgment reference section 6q and the comparator 5h
A flaw judgment signal (Fig. 3h) is obtained. Furthermore, by outputting the contents of the counter 5f, the width of the flaw can be measured.

Note that the parts after Antogame 6d can be provided with various functions by changing them depending on the purpose of flaw treatment.

Although the above explanation took cracks as an example, depressions such as pinholes can also be detected in the same way.

Furthermore, if the reference voltage in the defect detection section 5 is changed according to the state of the reflected signal from the surface of the object to be inspected as shown in FIG. As shown in the figure, the rate at which signals other than flaws are mixed becomes small.

This can be done by installing a low-pass filter on the photoelectric signal from the -dimensional imaging device and using this output as the reference voltage v5 10.2. .

It is.

Furthermore, if the irradiation light of the illumination device 1 and the scanning line of the one-dimensional imaging device 2 form a constant angle ψ as shown in FIG. can do. The same applies when the irradiated light can be regarded as parallel light rays. Furthermore, a configuration in which the optical axis of incidence on the -dimensional imaging device does not coincide with the irradiation optical axis of the illumination device will exhibit the same function.

Effects of the Invention (1) The edge portion of a flaw can be easily detected because the configuration detects the edge portion of a flaw by using specularly reflected light that is sufficiently higher than the light reflected from the surface of the object to be inspected. Presence can be easily detected.

(2) Since the flaw detection process is performed based on the connectivity between the edge signal and the flaw signal, flaws can be detected accurately even if the surface condition of the object to be inspected changes.

(3) Since the signal from the flaw area is temporally followed by the edge signal, there is no need to temporarily store the photoelectric signal from the object to be inspected, and only the flaw area can be detected, and furthermore, it is possible to detect the flaw area in chronological order. Signal Processing Page 11 is easy.

[Brief explanation of drawings]

Figure 1 is a diagram showing the signal state obtained by the conventional detection power formula,
Fig. 2 is a basic configuration diagram of the present invention, Fig. 3 is a diagram showing the operation of the present invention, Fig. 4 is a diagram showing the state of light reflection in a crack, and Fig. 6 is a diagram showing an example of signal processing. block tire duram,
FIG. 6 is a signal state diagram showing another embodiment of signal processing, and FIG. 7 is a configuration diagram of another embodiment of the illumination method. DESCRIPTION OF SYMBOLS 1... Illumination device, 2... -dimensional imaging device, 3... Test object, 4... Edge detection section, 6...・Paper detection department 0 Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure---------Vz -〉; L warehouse direction Figure 2/4 Figure 3

Claims (1)

[Claims] (1) A unidirectional illumination device that illuminates a red-hot object from an oblique direction, and the illumination direction of the illumination device and the detection optical axis are normally arranged so as not to receive specularly reflected light from the illumination device. a one-dimensional imaging device that images the surface of a red-hot object and starts scanning from the side opposite to the irradiation direction of the illumination device; and a one-dimensional imaging device that captures reflected light higher than the reflection from the surface of the red-hot object from the photoelectric output of the -dimensional imaging device. A flaw detection method that detects reflected light that is lower than the level of reflected light from the surface of a red-hot object that continuously reaches high reflected light levels in chronological order based on the edge detection unit that detects the edge detection unit and the output of the edge detection unit. A red-hot object surface inspection device consisting of two parts. (2. A red-hot object surface inspection device according to claim 1, in which the irradiation light from the illumination device and the scanning line of the -dimensional imaging device are arranged on the same plane.