JPH0465660A - Automatic flaw detecting device - Google Patents

Abstract

PURPOSE:To accurately detect a surface image even when a body to be detected is transported at a high speed and to improve the flaw detection accuracy by projecting a surface image of the body to be detected which travels on a rotatable scanning mirror and detecting the image by a telecamera. CONSTITUTION:The automatic flaw detecting device 10 consists of the scanning mirror 18 which is provided rotatably within a specific angle range opposite the surface of the body 11 to be detected such as a steel piece, a control means 20 which controls the rotating speed of the scanning mirror 18 corresponding to the transporting speed of the body 11 to be detected, and the telecamera 16 which has an image receiving lens 16a for detecting the surface state of the body 11 to be detected with the reflected light from the scanning mirror. This automatic flaw detecting device 10 rotates the scanning mirror 18 following up the body 11 to be detected according to the transporting speed and detects the surface image projected on the scanning mirror 18 by the telecamera 16, so the surface image of the body to be detected can be captured as a still image and the surface state of the body 11 to be detected can accurately be inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic flaw detection device that detects surface flaws by projecting the surface condition of a steel piece or the like on an image in a fluorescent magnetic particle flaw detection method.

(Prior Art) Conventionally, an automatic steel billet flaw detection device using a magnetic particle detection method scatters fluorescent magnetic particles on the surface of a magnetized steel billet 1, as shown in FIG. While transporting at high speed, the pattern of the magnetic particles excited by the irradiation of the ultraviolet lamp 2 is observed on the steel piece l.
Surface flaws are detected by detecting an image with a television camera 3 fixed at a predetermined nearby position and processing this image. In this case, the image detection by the television camera 3 is based on the steel piece l.
The inspection is carried out periodically during the traveling of the steel billet 1, and each time the steel billet 1 travels a certain distance, it is sequentially inspected, for example, within the illustrated area als a 2.

(Problem to be Solved by the Invention) However, according to the conventional automatic flaw detection equipment, the image of the surface of the moving steel billet is detected using a television camera fixed opposite to the surface of the steel billet, so the transfer of the steel billet is difficult. As the speed increases, the amount of light accumulated in the television camera decreases, and the brightness corresponding to surface flaws decreases, for example, as shown in FIG.
The detection performance of surface flaws deteriorates.

Furthermore, as shown in Fig. 8, for example, as the transfer speed of the steel billet increases, it becomes difficult to detect surface flaws due to the scanning principle of the camera. Although surface flaws Kt that are long in the transfer direction can be detected, surface flaws Ks that are short in the transfer direction may disappear and are difficult to detect.

The present invention was made in order to solve the above problems, and provides an automatic flaw detection device that can reliably detect the surface image of a steel billet traveling at high speed and can detect minute defects with high detection performance. The purpose is to

(Means for Solving the Problems) To achieve this, the automatic flaw detection apparatus of the present invention includes: - a scanning mirror that is rotatably provided within a predetermined angle range facing the surface of an object to be detected, such as a piece; Consisting of a control means for controlling the rotating speed of the scanning mirror according to the transport speed of the object to be detected, and a television camera having an image receiving lens for detecting the surface condition of the object to be detected by the light reflected from the scanning mirror. It is characterized by being

(Function) According to the automatic flaw detection device of the present invention, the scanning mirror is rotated so that the surface image of the object to be detected follows the object according to the transport speed, and the surface image reflected on the scanning mirror is captured by the television camera. Since the image is detected by , the surface image of the object to be detected can be captured as a still image, and the surface condition of the object to be detected can be inspected with high accuracy.

(Example) Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 1, a detection object 11 made of a long piece of steel with a rectangular cross section is transported in the direction of arrow C by a driving means (not shown). And the driven roller 1 of the automatic flaw detection device IO
2 rotates around a shaft 14, and the number of rotations thereof is detected by an encoder 13.

Further, on the rear side in the traveling direction of the detected object 11, the detected object 1
A magnetization device (not shown) that magnetizes the surface of the object 11 with a coil or the like, and a magnetic powder scattering device (not shown) that spreads magnetic powder onto the magnetized surface of the detected object 11 are provided. Then, the magnetization device and the magnetic powder scattering device are activated to
When the test surface 11a is transferred, an inspection surface 11a having a magnetic particle pattern is sent to the surface of the object 11 to be detected.

A flat scanning mirror 18 and a television camera 16 are provided on the forward side of the magnetization device and magnetic powder dispersion device in the direction of movement of the detected object 11 = The scanning mirror 18 reflects the image of the inspection surface 11a on a mirror surface 18a. It is attached to the support shaft 17 so that it can rotate within a predetermined angular range around a position where the angle between the inspection surface 11a and its mirror surface 18a is 45 degrees. Further, the television camera 16 directs the inspection surface 16 while directing its image receiving lens 16a toward the mirror surface 18a so as to capture the surface image of the object 11 to be detected reflected on the mirror surface 18a.
It is fixed substantially parallel to 1a. At this time, the optical axis of the television camera 16 is made to intersect with the support axis 17.

Therefore, as shown in FIG. 2, the inspection surface 11a and the mirror surface 1
When the scanning mirror 18 is located at the reference position M0 where the angle with the mirror surface 8a is 45°, the optical axis of the television camera 16 that is reflected from the inspection surface 11a to the mirror surface 18a and reaches the image receiving lens 16a is the angle of incidence and angle of reflection. Both form an angle of 45'', which corresponds to the starting point N where the distance from the inspection surface 11a to the mirror surface 18a is the shortest distance.Then, the scanning mirror 18 moves within the range of angle θ/2 around the reference position M0 as shown in FIG. When the optical axis reaches the positions M+ and M2 by rotating counterclockwise and clockwise, respectively, as shown in FIG. and N2
Move to.

Further, a servo motor 19 is attached to the support shaft 17 that supports the scanning mirror 18, so that the scanning mirror 18 is repeatedly rotated within the above-mentioned predetermined rotation angle range. The servo motor 19 is connected to a driver unit 20 by a cable 21 and electrically connected to a frame memory 15 and an encoder 13 by a cable 22 and a cable 23, respectively, and repeats the scanning mirror 18 according to the transport speed of the detected object 11. The speed is controlled. In other words, the detected object 11 while the encoder 13
An electrical signal with a rotational speed corresponding to the transfer speed of the object 11 is sent to the driver unit 20 through the frame memory 15, and a control signal sent from the driver unit 20 to the servo motor 19 causes the repetition speed of the scanning mirror 18 to match the transfer speed of the object 11. adjusted accordingly.

The repetition rate of scanning mirror 18, controlled by servo motor 19, is adjusted as shown in FIG. In other words, control is performed so that the starting point where the optical axis of the television camera 16 contacts the inspection surface 11a is equal to the speed of the detected object 11. Therefore, when the detected object 11 moves in the direction of the arrow C, for example, the starting point of the scanning mirror 18 is moved from the position N shown in FIG.
When moving to the position, the distance X1 between N1 and No and the distance X2 that the detected object 11 moves becomes approximately equal.

Here, V is the transport speed of the detected object 11, the distance between the support shaft 17 of the scanning mirror 18 and the inspection surface 11a, and the scanning mirror 1
If the rotating speed of 8 is ω (rad/5ec), then the transfer speed is expressed by the following equation.

V=Ltan [(360/2π) ω] The frame memory 15 is connected to the television camera 16 by a cable 24 and electrically connected to a monitor or printer (not shown) by a cable 25. Then, the position of the mirror where the angle between the inspection surface 11a and the mirror surface 18a is 45 degrees is determined from the control position of the servo motor by the driver unit 20, and the image signal at this time is displayed on a monitor or printer.

Next, the inspection surface 11a of the detected object 11 and the television camera 16
FIG. 4 shows the relationship between the image processing range and the image processing range.

As shown in FIG. 4(a), during detection, the image processing range moves in the same direction as the transport direction C of the inspection surface 11a. During this time, the inspection surface 11a surrounded by the image processing range is captured as a still image. Next, when the scanning mirror 18 starts returning, the image processing range starts moving in the direction of the arrow d, as shown in (b). During the return operation, the image processing range moves as shown in (C), and the right end position above the image processing range is the inspection surface 1 of the image processing range at the time of inspection (a).
When it reaches the left end position of 1a, the return of the scanning mirror 18 is completed, as shown in (d). Next, the process shifts to the detection operation shown in (a) again. The surface image of lla captured within the image processing range by such repeated operations of the scanning mirror is (a
) and (b), since the surface flaw 1 is captured as a still image existing at a substantially constant position within the image processing range, the inspection surface 11a of the object 11 to be detected can be accurately detected and the transport direction Even short surface flaws can be reliably detected.

By repeating such image detection, the detected object 11
Even when the television camera 16 is traveling at high speed, the inspection surface 11a follows the surface image due to the rotation of the scanning mirror 18.
A still image can be accurately inspected without reducing the amount of light from the surface image of the object 11. Therefore, even short flaws in the direction of movement of the object 11 can be reliably detected.

In this embodiment, a case has been described in which one side of the object to be detected 11 is inspected, but as shown in FIG. and the scanning mirror 33 to the detected object 29.
The television camera 34 and the scanning mirror 35 may be installed at a corner of the detected object 29. In this case, two planes and corners can be inspected at the same time.

In this case, the optical axis of the television camera is parallel to the direction of transport of the detected object.

(Effects of the Invention) As explained above, according to the automatic flaw detection apparatus of the present invention, the surface image of the moving object to be detected is reflected on the rotatable scanning mirror and the image is detected by the television camera. Since the surface image can be captured as a still image, the surface image can be accurately detected even when the object to be detected is transported at high speed, and the flaw detection accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an automatic flaw detection apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the relationship between the rotation angle of the scanning mirror and the surface image of the object to be detected, and FIG. An explanatory diagram for explaining the relationship between the moving speed of the optical axis due to the rotation of the scanning mirror and the moving speed of the steel piece, FIG. 4 is an explanatory diagram for explaining the effect when detecting surface flaws as an image, FIG. 5 is a schematic configuration diagram showing another embodiment of the present invention, FIG. 6 is a schematic perspective view showing a conventional automatic flaw detection device, and FIG. A characteristic diagram showing the relationship and FIG. 8 is a characteristic diagram showing the relationship between the detected image and the flaw detection speed. 10 ... 1 l ... 16 ... 16a ... 18 ... 19 ... 20 ... automatic flaw detection device, object to be detected, television camera, image receiving lens, scanning mirror servo motor (control means ), driver unit (control means). Applicant 2: Daido Steel Co., Ltd.

Claims (1)

[Claims] (1) A scanning mirror that is rotatably provided within a predetermined angle range facing the surface of an object to be detected such as a piece of steel, and the rotational speed of the scanning mirror is controlled according to the transport speed of the object to be detected. and a television camera having an image receiving lens that detects the surface condition of the object to be detected using the reflected light from the scanning mirror.