JPH05273151A - Automatic flaw detecting device - Google Patents

Abstract

PURPOSE:To precisely and surely detect only surface flaws when irregularities other than the flaws exist on the surface of a specimen in an automatic flaw detecting device detecting the surface flaws based on the pickup image of the surface photographed while the device is moved relatively to the specimen. CONSTITUTION:A rotatable reflecting mirror 44 and a television camera 46 photographing a surface 18 via the reflecting mirror 44 are arranged on a bogie 28 moved in parallel with the surface 18 of a specimen 12. The reflecting mirror 44 is follow-rotated in response to the moving speed so that the surface 18 is photographed in nearly the static image state regardless of the movement of the bogie 28, the image pickup range is shifted by the preset drift quantity during the follow rotation period of the reflecting mirror 44, thus the image signal by irregularities is averaged to increase the S-N ratio, and the detection precision for small flaws is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic flaw detection apparatus for detecting surface flaws of a material to be inspected based on a picked-up image of the surface by using a magnetic particle flaw detection method, etc. The present invention relates to an improvement in a technique for capturing an image of the surface while moving relatively.

[0002]

2. Description of the Related Art Among the methods for detecting scratches on the surface of a material to be inspected, such as steel slabs, a magnetic particle flaw detection method or a flaw detection method for finally observing the surface after performing surface treatment for detection There is a penetrant inspection method. For example, in the fluorescent magnetic particle flaw detection method which is one example thereof, as shown in FIG. 8, the fluorescent magnetic powder is attached to the surface of the pre-magnetized steel piece 80 by spraying or dipping, and the magnetic powder excited by irradiation of the ultraviolet lamp 82 is excited. The pattern is captured by a television camera 84 arranged facing the surface of the steel piece 80 to capture it as an image, and means for detecting surface scratches on the steel piece 80 based on the image signal is used. ing. In this case, the TV camera 84
Has a large number of photoelectric conversion units and is fixedly arranged, and the light from the surface of the steel piece 80 is incident on these photoelectric conversion units to correspond to the amount of incident light for each photoelectric conversion unit. The image signal is a predetermined scan cycle, that is, the cycle time for capturing and processing one screen of image signal from all photoelectric conversion units, and for example, it is output at a 1/30 second cycle. There is. When the material to be inspected is a long piece such as the steel piece 80, the television camera 84 continuously moves the magnetic powder pattern while linearly moving either the steel piece 80 or the television camera 84 in the longitudinal direction by the moving device. The image is captured.

However, when the surface of the material to be inspected is imaged while being relatively moved in this way, when the relative movement speed becomes high, photoelectric conversion of light from the surface of the material to be inspected incident on an image pickup device such as a television camera is performed. Since the incident position with respect to the surface part is displaced, the amount of light accumulated in the photoelectric conversion part of the part corresponding to the surface scratch is reduced and the intensity of the image signal is lowered, and particularly the detection performance for the surface scratch having a short length in the moving direction is reduced. There was a problem of lowering. On the other hand, for example, in Japanese Patent Application No. 176893 filed by the present applicant earlier, a reflecting mirror which is rotatable around a rotating shaft perpendicular to the moving direction of the material to be inspected is provided and the reflecting mirror is provided. The surface of the material to be inspected is imaged by the imaging device via the, and the reflecting mirror is rotated in accordance with the movement of the material to be inspected so that the imaging range is maintained in substantially the same range as the surface of the material to be inspected. Due to
An automatic flaw detection device is disclosed in which the surface is imaged in a substantially static image state regardless of the movement of the material to be inspected, and the detection accuracy of surface flaws is improved.

[0004]

However, as described above, when the reflecting mirror is rotationally controlled so that the imaging range is maintained in the same range on the surface of the material to be inspected, and the surface is imaged in a completely static image state, For example, if there are fine irregularities over the entire surface of the inspected material, such as shot peening on the surface of the inspected material in order to remove the black skin due to quenching, etc. Since the light such as the magnetic powder pattern caused by it is also captured relatively clearly and output as an image signal, it is difficult to distinguish between an output signal based on the unevenness and an output signal based on a relatively small scratch in the signal processing. There is a problem. Specifically, when setting the threshold level to determine whether the output signal is due to surface scratches, if the threshold level is set to a small value, not only the scratch-based output signal but also the unevenness-based output signal will be detected. On the other hand, if it is set to a large value, the output signal based on the unevenness will not be detected, but the output signal will be missed due to a small flaw, so that it will be extremely difficult to properly set it.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reliably detect surface scratches even when relatively fine irregularities are present on the surface of a material to be inspected. Is to

[0006]

In order to achieve the above object, the gist of the present invention is (a) a machine frame,
(B) a moving device that relatively moves the machine frame and the material to be inspected in a straight line direction parallel to the surface of the inspected material; and (c) rotatably about an axis center perpendicular to the straight line direction. A reflecting mirror provided on the machine frame and having a mirror surface parallel to the one axis, and (d) a large number of photoelectric conversion units, which are fixedly arranged on the machine frame, Light is incident on the photoelectric conversion unit via the reflecting mirror to output an image signal corresponding to the amount of incident light for each photoelectric conversion unit, and (e) relative movement by the moving device. Regardless of the fact that the surface of the material to be inspected is imaged by the imaging device in a substantially still image state, a rotation control means for following and rotating the reflecting mirror around the uniaxial center according to the relative movement thereof. Image signal output from each photoelectric conversion unit of the imaging device In an automatic flaw detection device that automatically detects a scratch existing on the surface of the material to be inspected based on the captured image, the rotation control means, when the follow-up rotation of the reflecting mirror, It is configured to shift the image pickup range of the image pickup device by a predetermined shift amount so that the S / N (scratch signal to noise ratio) becomes large.

[0007]

In such an automatic flaw detector, the moving device relatively moves the machine frame and the material to be inspected in a straight line direction parallel to the surface of the material to be inspected, and is concerned with the relative movement. Instead, since the reflecting mirror is rotated by the rotation control means according to the relative movement so that the surface of the inspected material is imaged through the reflecting mirror by the image pickup device in a substantially still image state, the relative movement is performed. Regardless of this, the light from the surface of the material to be inspected is always incident on the photoelectric conversion unit at a fixed position in the image pickup device, and the same amount of light as when not moving is accumulated in each photoelectric conversion unit. .. As a result, even if the surface scratch is short in the moving direction, an image signal with an intensity corresponding to the scratch is output from the image pickup device, and even when the image is moved at a high speed by the moving device, even a small scratch on the surface of the material to be inspected. Can be reliably detected. The rotation control of the reflecting mirror is repeated along with the relative movement of the machine frame and the inspection material, so that the surface of the inspection material is sequentially divided by the imaging device in the relative movement direction. It is imaged.

Further, since the rotation control means is configured to shift the image pickup range of the image pickup device by a predetermined predetermined shift amount when the reflecting mirror is turned following, the surface of the material to be inspected. Even in the case where there are relatively fine irregularities, a relatively large S / N can be obtained. That is, the amount of incident light from the surface of the material to be inspected due to the unevenness in each photoelectric conversion unit of the imaging device is averaged by the deviation of the predetermined amount, and the photoelectric conversion unit outputs the average amount of incident light. While the signal strength of the image signal due to scratches becomes flat, the deterioration of the signal strength of the image signal due to scratches can be small if at least the length dimension of the scratches is longer than the deviation amount in the relative movement direction. ,
It is possible to improve the S / N ratio of the image picked up by the image pickup device, and this makes it possible to lower the threshold level for scratch determination and detect even small scratches satisfactorily.

As described above, the predetermined shift amount at which the S / N of the picked-up image is large is such that the noise caused by fine irregularities present on the surface of the material to be inspected is averaged and reduced, but it may cause scratches. The resulting image signal does not decrease so much,
As a result, the amount of deviation is such that the S / N becomes large, and is appropriately determined in consideration of the size of the scratch to be detected, the pitch of the surface irregularities, the imaging mode of the imaging device, and the like.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view of an automatic flaw detection apparatus 10 using a fluorescent magnetic particle flaw detection method according to an embodiment of the present invention. The material 12 to be inspected, which is a steel piece made of a ferromagnetic material, has an elongated shape with a rectangular cross section, and has a substantially horizontal posture in which ridge lines in the longitudinal direction are positioned vertically and horizontally by a plurality of inspection bases 14. It is fixedly supported by. Then, by the pair of inspection units 16 that are moved in the longitudinal direction of the inspected material 12,
The scratches present on the outer surface 18 (the upper two surfaces) are detected. In the magnetic particle flaw detection method, the magnetic flux, which is a powder of a ferromagnetic substance, is concentratedly attracted to the scratched portion by the leakage magnetic flux flowing around the flaw (defect) on the surface or in the vicinity of the surface, and the presence or absence of scratches from the magnetic powder pattern. 2 and the position of the material to be inspected. As shown in FIG. 2, the material 12 to be inspected is previously loaded into the magnetizing device 20 and magnetized by being exposed to a magnetic field, and is also loaded into the magnetic powder adhering device 22 to be attached to the magnet. The magneto-optical powder is attached to the surface 18 by being immersed in a liquid in which the magneto-optical powder is dispersed and suspended in oil or the like. As is apparent from FIG. 2, the magnetizing device 20 and the magnetic powder adhering device 22 are sequentially arranged in the direction perpendicular to the longitudinal direction of the material 12 to be inspected with respect to the automatic flaw detector 10, and a walking beam or the like (not shown) is provided. The material 12 to be inspected is conveyed by the conveying device, and is carried out in the same direction when the flaw detection work in the automatic flaw detector 10 is completed. The automatic flaw detection device 10 has a dark room structure in order to capture the magnetic powder pattern of the fluorescent magnetic powder as clearly as possible.

In FIG. 1, above the material 12 to be inspected,
A pair of guide rails 24 and 26 having a length longer than the entire length of the material 12 to be inspected by a predetermined amount in the longitudinal direction of the material 12 to be inspected, that is, a straight line direction parallel to the surface 18, are arranged via a frame member (not shown). There is. The inspection unit 16 is arranged on a carriage 28 that can be run on the pair of guide rails 24 and 26, so that flaw detection scanning is performed over the entire length of the inspection target material 12.
In this embodiment, the carriage 28 corresponds to the machine frame. Trolley 28
Is provided with a servo motor 30 that is rotationally driven in both forward and reverse directions by a drive signal SD1 supplied from a control device 56 (see FIG. 5).
Is transmitted to the drive wheels 34 and 36 via the timing belt 32, so that the carriage 28 travels on the guide rails 24 and 26 at a predetermined moving speed V. The servo motor 30 is provided with an encoder 38, and the drive wheel 3 is determined based on the rotation angle of the servo motor 30.
The rotation angle signal SA1 representing the rotation angle is supplied from the encoder 38 to the control device 56 so that the rotation angle of 4 and the moving speed V of the carriage 28 can be detected. A meshing tooth 40 is formed on the upper surface of one of the guide rails 24, and a meshing tooth 42 that meshes with the meshing tooth 40 is formed on the outer periphery of the one drive wheel 34 rolling on the guide rail 24. By the meshing of the meshing teeth 40 and 42, the carriage 28 moves on the guide rail 24 accurately in correspondence with the rotation angle of the drive wheel 34. In this embodiment, the guide rails 24,
26, the drive wheels 34, 36, the servomotor 30, and the like constitute a moving device.

The pair of inspection units 16 includes the carriage 28.
Each of them includes a reflecting mirror 44, a television camera 46, an ultraviolet lamp 48 and the like which are arranged in a predetermined positional relationship inside. A pair of inspection units 1
6 is a surface of the material 12 to be inspected 2
The surfaces are simultaneously flaw-detected, and the respective reflecting mirrors 44, television cameras 46, ultraviolet lamps 48 and the like are arranged symmetrically with respect to a vertical plane passing through the axis of the material 12 to be inspected. The reflecting mirror 44 is attached to the output shaft of the servomotor 50, and a mirror surface 52 formed in a plane including the axis O of the output shaft is adapted to be rotated around the axis O. The reference numeral 50 is fixed to the carriage 28 in such a manner that the axis O is perpendicular to the longitudinal direction of the material 12 to be inspected, that is, the moving direction of the carriage 28 and is parallel to the surface 18 of the material 12 to be inspected. Also, the TV camera 4
6 is attached such that the optical axis of the imaging lens is parallel to the moving direction of the carriage 28 and is orthogonal to the axis O.
Light from the surface 18 of the material 12 to be inspected is made incident through the reflecting mirror 44, so that the magnetic powder pattern on the surface 18 is imaged. The television camera 46 is a general image pickup device provided with a solid-state image pickup device (CCD), an image pickup tube, or the like. When light is made incident on each of a large number of photoelectric conversion units through an image pickup lens, the incident light enters the photoelectric conversion unit. The image signal SV corresponding to the amount of light is output to the control device 56 for each photoelectric conversion unit at a predetermined scanning cycle. The scanning cycle here means the image signal SV for one screen from all photoelectric conversion units.
The image signal SV output from each photoelectric conversion unit corresponds to the amount of light received during the scanning cycle.

FIG. 3 is a diagram showing a specific positional relationship as seen from a direction parallel to the axis O. The reflecting mirror 44 forms an angle of 45 ° between the mirror surface 52 and the surface 18 of the material 12 to be inspected. The position Mc can be rotated within an angle range Ms to Me of ± θ / 2. When the reflecting mirror 44 is at the position of Mc, the incident angle and the reflecting angle of the light from the point Pc, which is a perpendicular line from the axis O to the surface 18 of the material 12 to be inspected, onto the mirror surface 52 are 45 °, and the television Since the point Pc is located at the center of the image pickup range of the camera 46, that is, on the image pickup optical axis, when the reflecting mirror 44 is rotated from the position Ms to the position Me, the image pickup optical axis of the television camera 46 is changed to the surface 18. It moves from the upper point Ps to the point Pe. The servomotor 50 is provided with an encoder 54, and supplies a rotation angle signal SA2 indicating a rotation angle from the predetermined reference position around the axis O of the reflecting mirror 44 to the control device 56. The servo motor 5
0 indicates the control device 56 based on the rotation angle signal SA2.
Is feedback controlled by.

FIG. 4 shows the automatic flaw detector 10 with a material 12 to be inspected.
FIG. 4 is a cross-sectional view seen from the longitudinal direction of the ultraviolet lamp 4.
Reference numeral 8 is attached so that the actual image pickup range corresponding to the moving range from the point Ps to the point Pe of the image pickup optical axis of the television camera 46 by the rotation of the reflecting mirror 44 can be irradiated with an appropriate amount of ultraviolet rays. .. Further, of the four ridge lines extending in the longitudinal direction of the inspected material 12, a pair of ridge lines 58 located on the left and right sides.
Below 60 and 60, a pair of edge irradiation lamps 62 are arranged at substantially the same position as the reflecting mirror 44 in the moving direction of the carriage 28, and by irradiating the ridge lines 58 and 60 with visible light, respectively, an image is picked up. Edge 58 on the screen
And the edges of 60 are defined. In addition, a pair of light projector 64 and light receiver 66 are arranged on both sides of the material 12 to be inspected. The light projector 64 and the light receiver 66 function as a photoelectric switch, and after the carriage 28 starts moving from the initial position where the light emitted from the light emitter 64 toward the light receiver 66 is not blocked, the material to be inspected is started. It is detected that the light is blocked by passing through the terminal 68 on the flaw detection start side of 12 and the detection signal S
Based on P, the control device 5 determines the flaw detection start time of the material 12 to be inspected.
6 can be judged.

The control device 56 includes a CPU, a ROM and a RAM.
It is configured to include a microcomputer having, etc., as shown in FIG. 5, based on the input signal, according to the program stored in the ROM in advance, while performing the arithmetic processing while using the temporary storage function of the RAM, It is designed to output drive signals and the like. The control contents related to the rotation control of the reflecting mirror 44 will be described in detail.
Is the rotation angle signal S supplied from the encoder 38.
The moving speed V of the carriage 28 is calculated based on A1, and the drive signal SD1 is output so that the moving speed V matches a predetermined target speed, and the servomotor 30 is feedback-controlled, and the carriage 28 moves. Regardless of this, the rotation angular velocity ω of the reflecting mirror 44 is calculated according to the moving speed V so that the surface 18 of the material 12 to be inspected is imaged by the television camera 46 in a substantially still image state, and the reflecting mirror 44 then The servo motor 50 is read while reading the rotation angle signal SA2 from the encoder 54 so as to rotate at the rotation angular velocity ω.
The drive signal SD2 is output to the feedback control.

That is, in FIG. 3, the case where the reflecting mirror 44 and the television camera 46 move to the right side in FIG. 3 as the carriage 28 moves, that is, the material 12 to be inspected relatively moves to the left side in FIG. Considering this, when the reflecting mirror 44 is rotated from the position of Mc to the position of Me at the rotation angular velocity ω, the image pickup center of the television camera 46 is from the point Pc to the point P.
Since the carriage 28 is moved by the distance x to e, the moving speed V is set so that the carriage 28 moves by a distance substantially the same as the distance x.
And the angular velocity ω is defined. Here, when the angle formed by the straight line O-Pc and the straight line O-Ps is θ and the distance from the axis O to the point Pc is y, x = y tan θ
From the optical relationship in reflection, the rotation angle of the imaging optical axis of the television camera 46 is twice the rotation angle of the reflecting mirror 44, the angle θ corresponds to 2ω, and the distance x Corresponds to the moving speed V, the angular speed ω may be determined according to the actual moving speed V so that the moving speed V and the angular speed ω satisfy the following expression (1). When 2ω, that is, θ becomes 90 ° or more, the equation (1) is not satisfied. Therefore, as the moving speed V and the angular speed ω, for example, a moving amount per control cycle time of feedback control, a rotation angle, or the like should be used. Becomes

[0018]

[Formula 1] V = y tan (2ω) (1)

From this relationship, the turning angular velocity ω of the reflecting mirror 44 is determined according to the moving speed V of the carriage 28, and the turning control is performed so that the imaging optical axis of the reflecting mirror 44 follows one point on the surface 18. By doing so, substantially the same range of the surface 18 of the inspection target material 12 is imaged by the television camera 46 that moves together with the carriage 28. FIG. 6 is a time chart showing an example of changes in the angle (rotational position with respect to the central position of 45 °) of the reflecting mirror 44 which is rotationally controlled according to the above concept. The rotation control of the reflecting mirror 44 is started in synchronization with the time when the passage of the terminal 68 of the inspected material 12 is detected by the detection signal SP from the light receiver 66, and the angle of the reflecting mirror 44 is at the position of Ms. From -θ / 2 at the angular velocity ω
It is rotated to + θ / 2 at the position e. During this period, the inspection unit 16 actually moves to the right at the moving speed V by a distance 2x from the state where the reflecting mirror 44 is at the position of Ms at the position of the axis O in FIG. 3 to the reflecting mirror 44 shown by the chain double-dashed line. As the image pickup optical axis of the television camera 46 is made to follow the position of the point Ps on the stationary inspection target material 12, the point Ps is displayed on the surface 18 of the inspection target material 12 at the center of the screen. It is possible to capture in the still image state located at. As a result, the magnetic powder pattern caused by the scratch can be clearly captured by the television camera 46 regardless of the movement of the carriage 28, and the presence or absence of the scratch and the position can be determined with high accuracy from the signal intensity of the image signal SV.

On the other hand, if the surface 18 of the material 12 to be inspected is subjected to shot peening treatment in order to remove the black skin caused by the quenching treatment, etc. When the surface 18 is imaged in the still image state, the magnetic powder pattern caused by these irregularities is also seen in the TV camera 4.
It is captured relatively clearly by 6. Therefore, the image signal SV _N due to such unevenness and the image signal SV due to the scratch
The S / N (scratch signal-to-noise ratio) with _S is likely to decrease, the threshold level for scratch determination must be set relatively large, and the accuracy of detecting small scratches decreases.

On the other hand, in the present embodiment, the period of the follow-up rotation of the reflecting mirror 44 with respect to the surface 18, specifically, the surface 18
So that an image in a substantially stationary state can be captured for at least two screens, for example, within a time period of about three screen scanning periods, the image pickup range of the television camera 46 is shifted by a predetermined minute amount, The detection accuracy for small scratches is maintained. That is,
The amount of incident light from the magnetic powder pattern due the asperities in the photoelectric conversion unit of the television camera 46 is averaged by the deviation of the minute amount, the signal intensity of the image signal SV _N also flat output with it from the photoelectric conversion portion On the other hand, with respect to the image signal SV _S due to the scratch, if the scratch dimension is at least longer than the displacement amount of the image in the moving direction of the carriage 28, the decrease in the signal strength is small, so the total S of the image signal SV is small.
/ N can be improved, and the threshold level for scratch determination can be lowered so that even small scratches can be detected satisfactorily. The minute amount is, for example, the detectability of a flaw in a captured image (minimum detectable value) or the surface 1
It is determined in advance by experiments or the like based on the size of the unevenness existing in No. 8 and the like. Further, since the material 12 to be inspected has a long shape by rolling or the like, the flaw shape is generally long in the longitudinal direction of the material to be inspected 12 and can be satisfactorily detected regardless of the displacement of the image in the longitudinal direction. .. Therefore, the actual rotation angular velocity ω
₀ is the above (1) when capturing in a completely still image state.
In the formula, it is determined according to the following formula (2) in which the moving speed V, that is, the moving amount per predetermined unit time, is added with the adjustment value α corresponding to the minute amount. The adjustment value α is determined in consideration of the control cycle time of the servo motor 50 and the scanning cycle of the television camera 46. The adjustment value α may be subtracted from the moving speed V.

[0022]

(2) V + α = y tan (2ω ₀ ) ... (2)

Incidentally, when a depression due to shot peening is present on almost one surface 18 of the material to be inspected 12 and a flaw having a depth of about 0.4 mm and a length of about 20 mm exists in the longitudinal direction, When the reflection mirror 44 is rotationally controlled at an angular velocity ω ₀ at which the deviation amount of the imaging range during the follow-up rotation period of the reflection mirror 44 is 1 mm, the intensity of the image signal SV _S of the scratched portion is about 15 as shown in Table 1. Then, the intensity of the image signal SV _N of the other part was about 4.5, and the S / N was about 3.33. On the other hand, in a completely static image state, that is, when the shift of the image pickup range is zero, the intensity of the image signal SV _S is about 23, the intensity of the image signal SV _N is about 7.5, and the S / N is about 3. .07,
It can be seen that although the signal strength is high, the S / N is better when it is shifted by 1 mm. When the reflecting mirror 44 is rotationally controlled at the angular velocity ω ₀ at which the deviation amount of the imaging range during the follow-up rotation period of the reflecting mirror 44 is 2 mm, the intensity of the image signal SV _S is about 13, and the image signal SV _N Strength is about 4.2, S / N
Is about 3.12, and compared with the case of shifting by 1 mm, the image signal SV _N hardly changes, but the image signal SV _N
S decreases, and S / N becomes equivalent to that in the case of capturing an image in a still image state.

[0024]

[Table 1]

Then, the reflecting mirror 44 is made to follow the turning angular velocity ω ₀ determined as described above, and slightly while the reflecting mirror 44 is turning from the position Ms to the position Me in FIG. A predetermined range on the surface 18 of the material 12 to be inspected is imaged in a state where there is a shift, while the next block in the front direction of movement divided into a plurality of portions based on the terminal 68 of the material 12 to be inspected in the direction of movement of the carriage 28. To capture the (imaging range), for example, in the time chart of FIG.
Between e and Ts, the reflecting mirror 44 moves from the position of Me to Ms.
The position is swiftly returned and rotated, and then the position is again swung at the rotational angular velocity ω ₀ from the position of Ms to the position of Me, and imaging is similarly performed. By repeating such control, the flaw detection work is advanced over the entire length of the material 12 to be inspected. In the present embodiment, the control device 56 that performs the series of signal calculation processing described above is the reflection mirror 44.
The rotation control means is configured together with the servo motor 50 that actually rotates the.

FIG. 7 shows the inspection unit 16 as described above.
7 is an actual imaging situation when the angle of the reflecting mirror 44 is controlled in accordance with the movement of the image, which is partially developed so that the imaging range faces forward. In (a) of this figure, the reflecting mirror 44 is located at the position of Ms and starts imaging the surface 18 of the n-th block n from the terminal 68 of the inspected material 12. Then, with the movement of the carriage 28 that travels to the right in the figure at the speed V, the reflecting mirror 44 rotates the angular velocity ω.
It is made to follow and rotate at ₀ , and in FIG.
Then, in (c), the reflecting mirror 44 is moved to the position M.
When the position of e is reached and the imaging of the block n is finished, T of FIG.
This is the state at the time corresponding to e. From the state of (c), the reflecting mirror 44 is returned and rotated, and in (d), the reflecting mirror 44 returns to the position of Ms and the next block (n
Imaging of +1) is started. Therefore, the TV camera 46
In the image picked up by (1) to (c), the surface 18 of the block n is captured in a substantially still image state. In the return rotation, at least a predetermined number of rotations faster than the angular velocity ω ₀ according to the moving speed V of the carriage 28 is performed so that at least a portion not imaged at the boundary between the block n and the block (n + 1) does not occur. It is returned at a dynamic angular velocity.

When the image signal SV thus picked up is supplied from the television camera 46 to the control device 56, the edge lines of the front surface 18 on the picked up image by the light of the edge irradiation lamp 62 are used as a reference screen by screen. Screen correction is performed so as to match the position, and a scratch map indicating the presence / absence of a scratch and the scratch position is created for each block based on the corrected image.

As described above, in this embodiment, the carriage 28 is linearly moved by the moving device such as the servomotor 30 in the direction parallel to the surface 18 of the material 12 to be inspected, at a right angle to the moving direction of the carriage 28. A reflecting mirror 44 that is rotatable about an axis O parallel to the surface 18, and the reflecting mirror 4 thereof.
The inspection unit 16 including a television camera 46 that captures an image of the surface 18 of the material 12 to be inspected via the camera 4 is provided, and the television camera 46 is provided regardless of movement of the carriage 28.
The controller 56 determines the rotational angular velocity ω ₀ of the reflecting mirror 44 according to the moving speed V of the carriage 28 so that the surface 18 of the inspection object 12 is imaged in a substantially still image state by the controlling device 56. 44 is rotationally controlled. Therefore, irrespective of the movement of the carriage 28, the light from the fluorescent magnetic powder pattern on the surface 18 is always made incident on the photoelectric conversion portions of the television camera 46 at certain positions and is moved to each photoelectric conversion portion. The same amount of light as when there is no light will be accumulated. As a result, even if the surface damage is short in the moving direction of the carriage 28, the image signal SV having an intensity corresponding to the scratch is output from the television camera 46, and even if the carriage 28 is moved at high speed, the object to be inspected. It is possible to reliably detect a small scratch on the surface 18 of the material 12.

Further, in this embodiment, the rotational angular velocity ω ₀ for rotating the reflecting mirror 44 in a follow-up manner is a predetermined small amount (corresponding to the size of the irregularities present on the surface 18 and the detectability of scratches ( For example, it is calculated according to the above equation (2) so that the image pickup range of the television camera 46 is shifted by 1 mm in the following rotation period of the reflecting mirror 44. Therefore, the amount of incident light from the magnetic powder pattern due to the unevenness is averaged due to the deviation of the minute amount, and the signal intensity of the image signal SV _N output from each photoelectric conversion unit becomes flat, while the image in the moving direction of the carriage 28 is displayed. With respect to the image signal SV _S due to a scratch having a size longer than the deviation amount, the decrease in the signal strength is suppressed to a small level, so that the overall S / N of the image signal SV is improved. As a result, the threshold level for scratch determination can be set low, and even small scratches can be satisfactorily detected, and the occurrence of undetected scratches and erroneous detection of scratches due to unevenness can be favorably avoided.

On the other hand, as described above, since the inspection unit 16 is moved in parallel with the inspection target material 12 placed on the inspection table 14, the length dimension of the inspection target material 12 is increased. It is possible to perform the flaw detection work in substantially the same space as in the above, and the space required for the flaw detection work can be smaller than that in the case where the flaw detection work is performed while moving the material 12 to be inspected in the longitudinal direction. Moreover, in the present embodiment, since the material 12 to be inspected is carried into the automatic flaw detector 10 from a direction perpendicular to the moving direction of the carriage 28, and the carrying equipment and the like are constructed so as to be carried out in the same direction after the inspection. The equipment space in the moving direction of the carriage 28, that is, in the longitudinal direction of the material 12 to be inspected can be saved.

Further, since the carriage 28 and the inspection unit 16 such as the reflecting mirror 44 and the television camera 46 arranged on the carriage 28 are relatively lightweight, the speed is higher than that when the material 12 to be inspected is moved. It has the advantage that it can be moved and the inspection efficiency can be further improved.

Further, in the present embodiment, one guide rail 24 is provided with the meshing teeth 40 and is meshed with the meshing teeth 42 provided on the drive wheels 34 of the carriage 28 to form the carriage 28.
The rotation of the reflecting mirror 44 is controlled based on the rotation angle of the meshing tooth 42 that rotates with the movement of the reflecting mirror 44. Therefore, the reflecting mirror 44 is meshed with the meshing teeth 40 and 42 without slippage.
It is possible to accurately perform the follow-up rotation control in accordance with the movement of the trolley 28, the blurring of the captured image is prevented, and the surface scratch detection accuracy is further improved.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, in the above-described embodiment, the inspection unit 1 including the reflecting mirror 44, the television camera 46 and the like.
In the case where the carriage 28 on which 6 is arranged is moved on the guide rails 24 and 26 with respect to the material 12 to be inspected whose position is fixed to move them relative to each other, the inspection unit 16 is fixed to the machine. The present invention is similarly applied to the case where the inspection target material 12 is arranged in a frame and is moved relative to the machine frame by a moving device such as a conveyor device so as to move them relative to each other. can do.

In the above-described embodiment, the inspection material 12 which is a long steel slab having a rectangular cross section is automatically detected, but other inspection materials such as polygons and circles are used. The size and shape of 12 are arbitrary, and the inspection unit 16 can be appropriately configured with the carriage 28 by disposing the reflecting mirror 44, the television camera 46, and the like according to each size and shape. Further, it is not limited to the case where two surfaces 18 of the surface 18 are simultaneously inspected, but the case where only one surface is inspected or the case where three or more surfaces are inspected at the same time may of course be performed. This may be the case where the unit 16 is provided.

In the above-described embodiment, the magnetizing device 20 is magnetized in advance and the magnetic powder adhering device 22 is used.
In the case where the inspected material 12 on which the magnetic powder pattern is formed is carried into the automatic flaw detection device 10 for automatic flaw detection,
It may be a case where the material 12 to be inspected is magnetized on the inspection table 14 and automatic flaw detection is performed while the magnetic particles are attached.

Further, in the above-mentioned embodiment, the carriage 28 is used.
The reflecting mirror 44 having a mirror surface 52 which is rotatable about an axis O parallel to the surface 18 of the material 12 to be inspected at a right angle to the moving direction of The center O does not necessarily have to be parallel to the surface 18 of the inspected material 12, and the mirror surface 52 may be offset from the axis O as long as it is parallel to the axis O. Various forms of reflector can be used, provided that the light from surface 18 can be incident on television camera 46.

Further, in the above-mentioned embodiment, the carriage 28 is used.
The rotational angular velocity ω ₀ of the reflecting mirror 44 is determined according to the moving velocity V of the
Instead of this, the dolly 28 from the terminal 68 of the material 12 to be inspected
Of the moving distance from the predetermined reference position on which the material 12 to be inspected is positioned and placed, and is determined in advance according to the moving distance or the moving position. The turning position of the reflecting mirror 44 may be controlled electrically or mechanically so that the turning angle is obtained.

In the above-described embodiment, the guide rail 24 is provided with the meshing teeth 40 and the drive wheel 34 is provided.
Although the meshing teeth 42 are provided on the guide rail 24,
A rack and gears are provided separately from the drive wheels 34, and the moving speed V of the carriage 28 is detected based on the number of rotations of the gears, or the guide rails 24 are brought into rolling contact with a fixed member. A roller is provided and the moving speed V of the carriage 28 is detected based on the number of rotations of the roller.
A linear motor is provided for driving the carriage 28, and the moving speed V of the carriage 28 is determined based on an output signal to the linear motor.
It is also possible to configure to detect.

Further, in the above embodiment, the drive wheels 3
It was the case where the carriage 28 having 4, 36, etc. and moved on the guide rails 24, 26 by the drive of the servomotor 30 was used as a machine frame. However, the carriage 28 was arranged in parallel with the surface 18 of the material 12 to be inspected. It may be a case where a machine frame that is guided by an installed guide rod or the like and is moved by a high-speed cylinder or the like is used.

Further, in the above-mentioned embodiment, the reflecting mirror 4
4 is rotated in a follow-up manner to shift the image pickup range of the TV camera 46 by about 1 mm in a period in which one inspection range is picked up, so that the follow-up rotation period is about three scan cycles of the TV camera 46. For example, about 0.3 mm per screen
However, the image pickup range is shifted by the shift amount per scanning cycle of the television camera 46 in the follow-up rotation period of the reflecting mirror 44, which is about 0.3 mm in the above example, and within the period. You may make it perform the signal processing which adds or averages the signal strength in the corresponding part of the several captured image taken in, and may perform a flaw determination based on the captured image after the signal processing. Further, light is accumulated in each photoelectric conversion unit of the television camera 46 during the follow-up rotation period of the reflecting mirror 44, and the amount of light received is accumulated in the follow-up rotation period after the follow-up rotation is completed. It is also possible to take in the corresponding image signal SV and make a scratch determination based on the captured image represented by the image signal SV.

Further, in the above-mentioned embodiment, the automatic flaw detector 10 using the fluorescent magnetic particle flaw detection method has been described, but also in the case of other automatic flaw flaw detectors using the magnetic particle flaw detection method or the penetrant flaw detection method. The invention can be applied as well.

Although not illustrated one by one, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a main part of an automatic flaw detector according to an embodiment of the present invention.

FIG. 2 is a plan view illustrating a conveyance path of a material to be inspected which is flaw-detected by the automatic flaw-detection apparatus of FIG.

FIG. 3 is a diagram illustrating in detail a positional relationship between a material to be inspected and a reflecting mirror and an imaging device in the automatic flaw detection device of FIG.

FIG. 4 is a cross-sectional view of the automatic flaw detection apparatus of FIG. 1 viewed from the longitudinal direction of a material to be inspected.

5A and 5B are views for explaining the mechanical and electrical configurations of the automatic flaw detection device of FIG.

6 is a time chart showing an example of a change in the rotation angle of the reflecting mirror controlled by the control device of FIG.

FIG. 7 is a diagram illustrating an imaging situation when the reflecting mirror is rotationally controlled by the control device of FIG.

FIG. 8 is a diagram illustrating an example of a conventional automatic flaw detection device.

[Explanation of symbols]

 10: Automatic flaw detector 12: Inspected material 18: Surface 24, 26: Guide rail (moving device) 28: Cart (machine frame) 30: Servo motor (moving device) 34, 36: Drive wheel (moving device) 44: Reflector 46: TV camera (imaging device) 50: Servo motor (rotation control means) 52: Mirror surface 56: Control device (rotation control means) O: Shaft center (uniaxial center)

Claims (1)

[Claims] 1. A machine frame, a moving device for relatively moving the machine frame and a material to be inspected in a straight line direction parallel to the surface of the material to be inspected, and rotation about an axis perpendicular to the straight line direction. A reflecting mirror having a mirror surface parallel to the uniaxial center provided on the machine frame, and fixedly arranged on the machine frame with a large number of photoelectric conversion units, and from the surface of the inspected material. Light is incident on the photoelectric conversion unit via the reflecting mirror to output an image signal corresponding to the amount of incident light for each photoelectric conversion unit, and regardless of relative movement by the moving device, Rotation control means for following and rotating the reflecting mirror around the uniaxial center according to the relative movement so that the surface of the material to be inspected is imaged by the imaging device in a substantially still image state. The captured image represented by the image signal output from each photoelectric conversion unit of the imaging device In the automatic flaw detection device for automatically detecting a flaw existing on the surface of the material to be inspected based on the above, the rotation control means, when the reflecting mirror is rotated following, the S / N of the image picked up by the image pickup device. The automatic flaw detection apparatus is configured to shift the image pickup range of the image pickup apparatus by a predetermined shift amount so as to be large.