JPS6349180B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface defect inspection device for inspecting slab cracks occurring on the surface of, for example, red-hot slab steel materials, and particularly relates to a surface defect inspection device that has an improved pattern recognition and discrimination method for vertical cracks and horizontal cracks. Related to defect inspection equipment.

Hot detection of surface defects on slabs has become very important from the viewpoint of energy saving and quality assurance of slabs. Although various surface defect inspection apparatuses have been implemented so far, many of them employ optical means in particular. One of these optical inspection means is to display an image of the slab surface on a television monitor using reflected light from the slab surface, and visually inspect the image. Another method uses a general-purpose computer to analyze an image of the slab surface and extract defects from the image instead of recognizing defects with the naked eye. The former is impossible to visually inspect for defects and difficult to quantify when the material to be inspected (slab material) moves at high speed, and requires a high degree of skill, so it is recommended to automate it from an early stage. A request was made. On the other hand, the latter method digitizes the video output from the ITV camera, stores it in the computer's memory, and then processes it with a computer program to bring it closer to the visual discrimination ability. Not only does this require a very large memory capacity, but it also requires a considerable amount of time for image processing, so it is far from being realized. Furthermore, there are other problems that make inspection for defects on the surface of the inspected material difficult. This is a problem of misjudgment due to the scale of the surface of the inspected material. Conventionally, to solve this problem, in both visual and automatic inspections, the inspection is carried out after using high-pressure water to blow away scale flaws, etc., but this is not considered to be a complete solution. .

The present invention has been made in view of the above circumstances, and its purpose is to focus on the defect patterns of vertical cracks and horizontal cracks, which are serious defects on the surface of the inspected material, and to eliminate the need for a large amount of image memory. The present invention provides a surface defect inspection device that performs pattern recognition without fail and thereby inspects vertical cracks and horizontal cracks on a material to be inspected in real time at low cost and at high speed.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Note that FIG. 1 shows the overall configuration of the apparatus, and FIG. 2 is a diagram showing the configuration of the crack detection circuit of FIG. 1. In Fig. 1, reference numeral 11 indicates a material to be inspected that moves in the direction of arrow A, and vertical cracks 12 and horizontal cracks 13 are shown as defects on its surface, and images of the defects are further emphasized in the width direction of the material to be inspected 11. In order to do this, a light source 14 such as a rod-shaped mercury lamp is arranged to illuminate the surface of the material to be inspected. 15 is the material to be inspected 1 while scanning in the surface width direction of the material to be inspected 11;
This is an imaging camera that captures a reflected light image of one surface and then outputs it as a video signal, using a one-dimensional image sensor camera. Reference numeral 16 denotes a synchronization signal generating section that generates a synchronization signal at predetermined intervals according to the moving speed of the inspection object 11 in order to eliminate overlapping scanning and intermittent scanning in the moving direction of the inspection object 11. 17 is a synchronization circuit that synchronizes the video signal of the imaging camera 15 and sends it to the crack detection circuit 18 to discriminate between vertical and horizontal cracks.

19 is a display section.

The crack detection circuit 18 is composed of a vertical crack detection system 20 and a horizontal crack detection system 30, as shown in FIG. The vertical crack detection system 20 includes an analog shift register 21 having a number of bits equal to one scan of the imaging camera 15, a delay circuit 22,
An analog shift register 23 stores the output of the delay circuit 22 in the same number of bits as the register 21.
, a differential amplifier 24 that takes the difference between the outputs of both shift registers 21 and 23, an adder 25, a shift register 26, and a vertical flaw discrimination circuit 27. Note that the output of the synchronization circuit 17 is branched into two, one of which is input directly to the shift register 21, the other is delayed and input to the shift register 23, and the outputs of the respective shift registers 21 and 23 are input to the differential amplifier 24. By performing differential output at , horizontal cracks are removed and vertical cracks are output. The adder 25 and the shift register 26 constitute a ring analog adder, which has the function of integrating each bit of the video signal in the line moving direction, emphasizing vertical defects, and averaging other defects such as scale defects. There is. Vertical flaw discrimination circuit 2
7 has a function of detecting vertical cracks by comparing with the integral output at a predetermined discrimination level.

On the other hand, the horizontal crack detection system 30 detects vertical cracks by extracting the output difference between shift registers 31 and 32 that are serially connected and store data for two columns in the line movement direction, and these shift registers 31 and 32. Differential amplifier 3 removes horizontal cracks and outputs
3, an integrating circuit 34 that integrates this output difference in the width direction of the material to be inspected, and a reset control circuit 35 that resets the integrated value of this integrating circuit every time the one scan ends.
and a horizontal flaw discrimination circuit 36. This horizontal flaw discrimination circuit 36 has a function of comparing the integral output at a predetermined discrimination level and detecting horizontal flaws.

Next, the operation of the apparatus configured as above will be explained. For example, as shown in FIG. 3, it is assumed that a material to be inspected 11 having vertical cracks 12, horizontal cracks 13, and other defects 40 such as scale defects, scab marks, etc. is moving in the direction of the arrow A in the figure. At this time, a reflected light image is obtained from the material to be inspected 11 by irradiation with the light source 14, and this image is scanned in the width direction of the material to be inspected by the imaging camera 15 and is imaged as a video signal. 16 and a synchronization circuit 17, the signal is supplied as a synchronized video signal to a crack detection circuit 18.

This crack detection circuit 18 converts the synchronized video signal for one scan in the width direction into a shift clock signal.
Based on the SC, the signals are delayed by the shift registers 21 and 31 and the delay circuit 22, and then sequentially stored in the shift register 23. And the shift register 21,
A differential amplifier 24 extracts the difference between the two outputs of 23 to obtain a signal differentiated in the scanning direction. Next, this differential output is sent to the adder 25 and the shift register 26.
The signal SI as shown in Fig. 3b is inputted to a ring analog adder consisting of
This is input to the subsequent vertical flaw discrimination circuit 27 and compared with the discrimination level VL to determine the signal 12 of the vertical crack flaw 12.
Detect S.

On the other hand, in the horizontal crack detection system 30, the synchronized video signals are accumulated as data for two columns in the line movement direction by shift registers 31 and 32 that are connected in cascade, and then these shift registers 3
1 and 32 is taken out by a differential amplifier 33, and the image of the surface of the inspected material is differentiated in the moving direction of the inspected material. Then, this differential output is integrated in the width direction of the inspected material by the integrating circuit 34 and the reset signal control circuit 35, and a signal 13 of the horizontal crack 13 as shown in FIG.
A signal S2 is extracted by emphasizing S and averaging the vertical flaws 12 and other flaws 40. Thereafter, the subsequent horizontal flaw discrimination circuit 36 compares the integral output S2 at a predetermined discrimination level VL to detect a horizontal crack 13.

Note that the present invention is not limited to the above embodiments. Although the above embodiment has a memory configuration using an analog shift register, the video signal is
- If you digitize using a D converter, you can perform digital processing instead of analog processing. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

As described in detail above, according to the present invention, differentiation is taken with respect to the space of the video image signal, so changes in the video output of low frequency components caused by reflectance changes due to uneven reflection on the surface of the inspected material or scale are reduced compared to the conventional method. can be removed to a large extent compared to moreover,
After this differentiation, integration is performed in the longitudinal direction of the defect, so other minute scale defects and sagging defects are averaged out, and only cracks can be detected with a high signal-to-noise ratio. Additionally, vertical and horizontal pattern discrimination can be performed with a small memory capacity, thereby significantly reducing system costs and providing a surface defect inspection device with high practical value.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention apparatus, FIG. 2 is a diagram showing a specific configuration of the crack detection circuit shown in FIG. 1, and FIGS. It is a figure which shows the detection signal of. DESCRIPTION OF SYMBOLS 11... Material to be inspected, 15... Imaging camera, 16... Synchronization signal generation section, 17... Synchronization circuit, 18... Crack detection circuit, 20... Vertical crack detection system, 21, 23,
26...Shift register, 22...Delay circuit, 24...
Differential amplifier, 25... Adder, 27... Vertical flaw discrimination circuit, 30... Horizontal crack detection system, 31, 32... Shift register, 33... Differential amplifier, 34... Integrating circuit,
36... Horizontal flaw discrimination circuit.

Claims (1)

[Scope of Claims] 1. An optical image of the surface of the inspected material is captured by an imaging device while scanning in the width direction, and a video signal output from the imaging device is synchronized in the direction of movement of the inspected material using a synchronization circuit while being vertically scanned. In a surface defect inspection device that supplies a crack detection system and a horizontal crack detection system to discriminate between vertical cracks and horizontal cracks, the vertical crack detection system transmits a video signal output from the synchronization circuit to the imaging device. a first shift register that stores a number of bits corresponding to one scan, and a second shift register that has an equal number of bits as the first shift register that sequentially stores the video signal output from the synchronization circuit via a delay circuit. 2 shift registers, a first differential amplifier that differentially outputs the outputs of both shift registers, an adder that adds the outputs of the first differential amplifier, and a system that sequentially stores the outputs of this adder. A ring analog adder includes a third shift register that supplies this stored output to the input side of the adder, and integrates flaws in the moving direction of the inspected material; and a vertical flaw discriminating circuit that detects a vertical crack flaw when it exceeds the discrimination level No. 1. On the other hand, the horizontal flaw detection system includes two rows in the moving direction of the inspected material outputted from the synchronization circuit. A fourth serially connected video signal that sequentially stores video signals of
and a fifth shift register, a second differential amplifier that differentially outputs the outputs of the fourth and fifth shift registers, and integrates the output of the second differential amplifier in the width direction of the material to be inspected. a horizontal flaw discriminating circuit that detects a horizontal flaw when the output level of the integrator circuit exceeds a second discrimination level; and a reset circuit that resets the output of the integrator circuit every time one scan is completed. A surface defect inspection device characterized by comprising a control circuit.