JP2005010039A - Visual examination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect flaws generated in the end part in the axial center direction of a developed outer peripheral surface, even on the basis of the end part in the axial center direction. <P>SOLUTION: This visual examination device 1 is constituted so as to inspect the appearance of a columnar object W to be inspected and to be fed while rotated around the axis of a feed direction A, and equipped with: an imaging part 2 for imaging the outer peripheral surface of the rotating object W, to obtain the image of a developed outer peripheral surface 20 of the object W; and a processing part 4 for scanning a constant range, based on a predetermined reference position to perform visual inspection processing. In the processing part 4, the proximate line f(yn) in an axial center direction, wherein the local fluctuations of an end part 25a in the axial center direction of the developed outer peripheral surface 20 are relaxed, is set as a reference position. In this constitution, even if there are flaws in the end part in the axial center direction of the object, and even if there are local fluctuations at the position of the end part in the axial center direction of the developed outer peripheral surface, since an approximate line, wherein the local fluctuations are relaxed, is set as the reference position to perform the scanning of the developed outer peripheral surface, the flaws generated in the end part in the axial center direction is surely detected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an appearance inspection apparatus.
[0002]
[Prior art]
As an appearance inspection apparatus, there is an apparatus that images a peripheral surface with a camera while rotating a cylindrical inspection object at a predetermined position, processes the captured image, and inspects a scratch on the inspection object. It is described in Document 1.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-335150
[Problems to be solved by the invention]
When inspecting an inspection object at a predetermined position, when inspecting many inspection objects, the inspection takes time. Therefore, the applicants of the present application (Japanese Patent Application No. 2002-51778) have proposed that the inspection object is conveyed while being rotated to shorten the inspection time.
[0005]
When the outer peripheral surface of the inspection object being conveyed while rotating is imaged, the outer peripheral surface of the inspection object in the image becomes a developed image, and both ends in the axial direction have inclinations. In order to determine the range of the developed outer peripheral surface to be inspected from such an image, one end of both axial ends of the developed outer peripheral surface is used as a reference, and a predetermined axial direction from the end in the axial direction. The width can be considered as the inspection target range.
[0006]
However, if one axial center end is used as a reference, even if this one axial end itself has a defect, the defective shape is used as a reference as it is. Even if there is a defect in the direction end, it is not detected.
Moreover, even if there is a defect at one axial end, the inspection target range is disturbed to inspect the predetermined axial width on the basis of the defect, and there is no defect at the other axial end. There is a risk of determining that it is a defect. That is, it becomes difficult to investigate the cause of a defect because a position different from the original defect location is determined as a defect.
Therefore, an object of the present invention is to enable detection of a defect at an end portion in the axial direction even when the end portion in the axial direction of the developed outer peripheral surface is used as a reference.
[0007]
[Means for Solving the Problems]
The present invention is an appearance inspection device for a cylindrical inspection object that is conveyed while rotating around an axis in the conveyance direction, and images the outer peripheral surface of the rotating inspection object, and the inspection object An imaging unit that obtains an image of the developed outer peripheral surface, a processing unit that performs a visual inspection process by scanning a developed outer peripheral surface in the image obtained by the imaging unit with a predetermined range based on a predetermined reference position; The processing unit can set an approximate line of an axial end portion in which local variation of the axial end portion of the development outer peripheral surface is reduced as the reference position.
[0008]
According to the present invention, even if there is a defect in the axial end of the inspection object and there is a local variation in the position of the axial end of the development outer peripheral surface, the approximation in which the local variation is reduced Since the developed outer peripheral surface is scanned using the line as a reference position, it is possible to reliably detect a defect at the axial end.
[0009]
The approximate line is preferably calculated as a linear straight line that approximates the end in the axial direction. In this case, the approximate line can be easily calculated.
[0010]
Further, when an error between the axial end and the approximate line calculated based on the axial end is larger than an allowable value, the position of the axial end is set as the reference position. Preferably it is done. When the error between the axial direction end and the approximate line becomes large, it is possible to prevent the inspection range from being greatly disturbed by using the position of the axial direction end without using the approximate line.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the appearance inspection apparatus 1 irradiates light to the imaging unit 2 that images the inspection object (hereinafter referred to as “work”) W being conveyed, and the workpiece W in the imaging range by the imaging unit 2. And an illuminating unit 3 that performs image capturing from the image capturing unit 2 and a processing unit 4 that performs image processing and the like.
[0012]
In addition, the appearance inspection apparatus 1 includes a transport unit 5 that sends the workpiece W to the imaging range by the imaging unit 2 and a rotating unit 6 that rotates the workpiece W in the imaging range. The workpiece W is rotated about the axis while being conveyed in the conveying direction A parallel to the axial direction X in a state where a plurality of workpieces W are aligned in the axial direction X by the conveying unit 5 and the rotating unit 6.
[0013]
The conveyance unit 5 is located on the upstream side of the rotation unit 6 and sends the workpiece W to the rotation unit 6 side on the downstream side. The transport unit 5 includes a work transport belt 8 and a work extrusion roller 9, and includes a transport belt 8 disposed below the aligned works W and an extrusion disposed above the work W. The roller 9 is disposed so as to sandwich the workpiece W. Due to the rotation of both 8 and 9, the workpiece W aligned in the axial direction X is sent toward the conveyance direction A toward the imaging range by the imaging unit 2 and passes through the imaging range. That is, the appearance inspection apparatus 1 is a through-feed method. In addition, the conveyance part 5 may send out the workpiece | work W by pinching and rotating the workpiece | work W from right and left, and the specific structure is not limited.
[0014]
The transport unit 5 continuously feeds the work W at a substantially constant speed without stopping. Therefore, even if the workpiece W comes into the imaging range of the imaging unit 2, the workpiece W does not stop but always moves and passes through the imaging range. For this reason, the workpiece | work W can pass the imaging range one after another, and can test | inspect efficiently.
[0015]
The rotation unit 6 rotates the workpiece W sent from the conveyance unit 5 around the axis X, and a pair of workpiece rotation rollers 10 whose axis is directed in the same direction as the axis X of the workpiece W. , 10 are provided. The pair of rotating rollers 10 and 10 are juxtaposed in the horizontal direction and are driven to rotate in the same direction. The workpiece W is pushed onto the pair of rotating rollers 10 and 10 by the transport unit 5 and rotates in a predetermined direction by the rotation of the rotating rollers 10 and 10. Further, the workpiece W pushed out onto the rotating rollers 10 and 10 is moved in the conveying direction A by the rear workpiece W, and thus moves on the rotating rollers 10 and 10 in the conveying direction A. That is, the workpiece W moves in the transport direction A while rotating around the axis in the rotating unit 6.
In the present embodiment, the transport unit 5 and the rotating unit are configured by separate mechanisms, but may be configured by a single mechanism in which the transport function and the rotating function of the workpiece W are integrated.
[0016]
The imaging unit 2 is disposed above the rotating unit 6 so that the workpiece W being conveyed while rotating can be imaged. The imaging unit 2 is configured by a line sensor camera, is provided so that the camera scanning direction at the time of imaging coincides with the X direction, and performs scanning to acquire a line image in the X direction near the top of the workpiece W. Since scanning in the X direction is repeated, the imaging unit 2 scans different positions in the circumferential direction of the workpiece W as the workpiece W rotates. Therefore, when the work W rotates once, a two-dimensional image in which the outer peripheral surface of the work W is developed is obtained. When the workpiece W is rotated without moving in the X direction, the deployed outer peripheral surface is rectangular. However, when the workpiece W is moved in the X direction with rotation, the deployed outer peripheral surface is in the X direction. It will be inclined.
[0017]
The appearance inspection apparatus 1 includes an inter-work detection unit 12 as a timing acquisition unit for acquiring an imaging timing by the imaging unit 2. The inter-work detection unit 12 is disposed on the rear side in the transport direction A with respect to the imaging unit 2 and includes a contact sensor, an optical sensor, and the like for detecting a work gap portion passing through the detection position 13. When the workpiece gap portion passes through the detection position 13, the workpiece detection unit 12 outputs a detection signal indicating that the workpiece interval has been detected to the processing unit 4. By detecting the interval between the workpieces, the timing for each movement time for one workpiece can be obtained, and even when the movement speed of the workpiece W changes, the timing corresponding to the movement time for one workpiece is always obtained. Note that the timing may be acquired by detecting the inter-work position based on the image obtained by the imaging unit 2.
[0018]
FIG. 2 shows an image captured during the appearance inspection process. At the time of imaging, a plurality of workpieces W are continuously conveyed side by side in the conveyance direction, and are rotated around the axis. The image obtained by imaging is an image for approximately one rotation of the workpiece W. In FIG. 2, a white range 20 is a developed outer peripheral surface of the workpiece W, and a range 21 on both the left and right sides of the central white range 20 is a workpiece gap portion between the workpieces W. In this image, not only the workpiece W to be inspected but also a part of the developed outer peripheral surfaces 20 and 20 of other workpieces W adjacent to the front and rear in the transport direction are shown.
[0019]
In the image, the developed outer peripheral surface 20 appears bright, but the work gap portion 21 appears darker. Due to the difference in brightness, the axial direction end of the developed outer peripheral surface 20 (the boundary between the developed outer peripheral surface and the gap portion 21). ) 25a can be detected. Since the image in FIG. 2 is taken while the work is being conveyed, the axial end 25a is inclined. That is, in FIG. 2, the direction from right to left is the conveyance direction, the upper side is a position earlier in time, and the position of the outer peripheral surface is shifted in the conveyance direction (leftward) as it goes downward. The axial direction both ends 25a and 25b are inclined by the amount of this deviation, and become inclined end portions. Note that the x and y coordinates in FIG. 2 coincide with the X and Y directions in FIG.
[0020]
3 to 5 show processing for setting a scanning reference position for appearance inspection processing. Since the appearance inspection process is performed by scanning a certain range of the image with the scanning reference position as a reference, it is necessary to set the scanning reference position as an initial process. Although the scanning reference position substantially coincides with the position of the inclined end portion 25a, an approximate line of the axial end portion 25a is used as the scanning reference position in order to detect defects in the axial end portion 25a itself.
[0021]
Here, the inclination of the inclined end portion 25a changes as the conveyance speed of the workpiece W changes. The position of the inclined end portion 25a varies in the x direction depending on the timing at which the workpiece W is imaged. When the inclined end portion 25a changes, the position / shape of the development outer peripheral surface 20 to be inspected also changes. As described above, even on the development outer peripheral surface 20 whose position and shape may change, the scanning reference position is determined based on the inclined end portion 25a, and the development is performed by scanning a certain range from the scanning reference position. The range of the outer peripheral surface 20 can be reliably inspected.
[0022]
As shown in FIG. 3, in order to set the scanning reference position, first, the position of the inclined end portion 25a is stored in the scanning reference array arr_x [yn] (step S1). The scanning reference array arr_x [yn] is a one-dimensional array, yn indicates the y coordinate in FIG. 2, and the x coordinate when the y coordinate is yn is stored as the array value arr_x [yn]. As shown in FIG. 4, the coordinates of the inclined end portion 25a reflect the defect shape as it is if there is a defect 30 such as a defect in the inclined end portion 25a, and local fluctuation due to the defect occurs at the position of the inclined end portion 25a. Has occurred. In FIGS. 4 and 5, the work gap 21 is omitted for simplification.
[0023]
Subsequently, on the basis of the position of the inclined end portion 25a stored in the scanning reference array arr_x [yn], an approximate line (primary line) f (yn) in which local fluctuation due to a defect in the inclined end portion 25a is reduced is calculated. Performed (step S2). The approximate line f (yn) indicates the x coordinate value. For example, the approximate line f (yn) is calculated as a straight line passing through two arbitrary points of the inclined end portion 25a. More specifically, it is calculated as a straight line passing through the point indicated by the first value arr_x [0] and the point indicated by the last value arr_x [ymax] of the scanning reference array.
Further, instead of the first value arr_x [0], the minimum value, the maximum value, or the average value of the first to twentieth values arr_x [0] to arr_x [19] may be employed. Furthermore, instead of the last value arr_x [ymax], a minimum value, a maximum value, or an average value of the last 20th values arr_x [ymax-19] to arr_x [ymax] may be employed. By doing so, the accuracy of the approximate line is further improved.
[0024]
Next, the scanning reference array arr_x [yn] is compared with the approximate line f (yn) (step S3). This comparison is performed for each point (pixel) of yn: 0 to ymax. If a difference (in the x direction) between the scanning reference array value arr_x [yn] and the approximate line f (yn) is equal to or less than e pixels for a certain value yn, the count number C increases. In addition, the value of e is about 2-3, for example.
The more the scanning reference array arr_x [yn] and the approximate line f (yn) match, the larger the count number C, and the smaller the count number C, the smaller.
[0025]
Further, based on the count number C, it is determined whether or not the difference between the scanning reference array arr_x [yn] and the approximate line f (yn) exceeds a threshold value (step S4). That is, when the portion where the difference between the scanning reference array arr_x [yn] and the approximate line f (yn) is within e pixels is equal to or greater than T [%], the two are substantially coincident with each other, and the axial direction end portion It can be determined that 25a (scanning reference array value arr_x [yn]) has good linearity. The value of T is, for example, about 97 to 98. Note that the mismatch between the scanning reference array arr_x [yn] and the approximate line f (yn) caused by the defective portion occurs only in a small range, and therefore hardly affects the determinations in steps S3 and S4.
[0026]
When the axial direction end 25a (scanning reference array value arr_x [yn]) has good linearity, the approximate line f (yn) approximated by a straight line is relative to the axial direction end 25a. Therefore, it can be evaluated that the local fluctuation is relaxed and has excellent closeness, and the value of the straight line f (yn) is substituted into the scanning reference array arr_x [yn] (step S5).
The axial direction end portion 25a is substantially linear if the conveyance speed is constant without fluctuation. Therefore, in the normal case, since the work conveyance speed is constant, in most cases, the approximate line f (yn) is substituted into the scanning reference array arr_x [yn].
[0027]
On the other hand, when the portion where the difference between the scanning reference array arr_x [yn] and the approximate line f (yn) is within e pixels is less than T [%], the approximate line f (yn) is the end in the axial direction. It can be evaluated that the error with respect to the portion 25a is larger than the allowable value and the closeness to the axial direction end portion 25a is low. In this case, the substitution of the straight line f (yn) into the scanning reference array arr_x [yn] is not performed. In other words, the position of the axial end portion 25a remains stored in the scanning reference array arr_x [yn]. Such a case is, for example, a case where the axial end portion 25a is a curved line due to a change in the conveyance speed, as shown in FIG. 6, and in this case, an approximate line f (yn) calculated as a straight line. Since the closeness with the axial direction end portion 25a is low, the axial direction end portion 25a is used as a reference instead of being used as a reference.
[0028]
The appearance inspection processing for the developed outer peripheral surface 20 is performed by scanning a predetermined range W1 (= length in the axial direction of the workpiece W) in the x direction with reference to the scanning reference array arr_x [yn]. As shown in FIG. 5, when the value of the scanning reference array arr_x [yn] is the value of the approximate line f (yn), the defect 30 at the axial end 25a is at the axial end 25a. It can be detected as a defect. Therefore, the defective part can be detected accurately.
On the other hand, when the value of the scanning reference array arr_x [yn] indicates the position of the axial end 25a, the position including the defect 30 at the axial end 25a is the scanning reference. It is not determined that the axial end portion 25a has the defect 30. In addition, since the position away from the scanning range W1 from the position of the defect 30 does not coincide with the position of the other axial end 25b, it is determined that there is a defect in the other axial end 25b that is not originally defective. Will result in. In order to deal with such a problem, in the present embodiment, the approximate line f (yn) is used as a reference, so that the position of the defect 30 can be accurately detected.
[0029]
As shown in FIG. 6, when the axial direction end portion 25a is a curve, the approximate line f (yn) does not approximate the axial direction end portion 25a well if the approximate line f (yn) is used as a reference. Even if there is no defect in the axial direction end portion 25a, it is determined that there is a defect. In this way, when the linearity of the axial end 25a is low, the axial end 25a itself is used as a reference to prevent erroneous detection that there is no defect. If the axial end 25a itself is used as a reference as described above, the position of the defect cannot be accurately determined. However, if there is a defect, the defect can be detected regardless of the accuracy of the position. ing.
[0030]
The present invention is not limited to the above embodiment. For example, in the above embodiment, the approximate line is determined based on the axial end portion 25a, but may be based on the other axial end portion 25b. In addition, the approximate line may be not only a straight line but also a curve, and in particular, when the axial direction end is a curve, by setting the approximate line of the curve in which local variation is relaxed as a reference position, More accuracy is improved.
Further, the scanning range in the appearance inspection process may be the entire range from the reference position to the developed outer peripheral surface, or may be only a partial range of the developed outer peripheral surface based on the reference position.
[0031]
【The invention's effect】
According to the present invention, even if there is a defect in the axial end of the inspection object and there is a local variation in the position of the axial end of the development outer peripheral surface, the approximation in which the local variation is reduced Since the developed outer peripheral surface is scanned using the line as a reference position, it is possible to reliably detect a defect at the axial end.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an appearance inspection apparatus.
FIG. 2 is a work image at the time of appearance inspection.
FIG. 3 is a flowchart of a scanning reference array setting process.
FIG. 4 is a workpiece image having a defect at an axial end.
FIG. 5 is a diagram showing an approximate straight line at an end portion in the axial center direction;
FIG. 6 is a diagram showing an approximate straight line when the end in the axial direction is a curve.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Appearance inspection apparatus 2 Image pick-up part 4 Processing part 20 Deployment outer peripheral surface 25a Axial direction edge part f (yn) Approximate line

Claims (3)

An appearance inspection device for a cylindrical inspection object conveyed while rotating around an axis in a conveyance direction,
An imaging unit that images the outer peripheral surface of the rotating inspection object and obtains an image of the developed outer peripheral surface of the inspection object;
A processing unit that scans a certain range with reference to a predetermined reference position on the developed outer peripheral surface in the image obtained by the imaging unit, and performs an appearance inspection process;
With
The visual inspection apparatus, wherein the processing unit is capable of setting an approximate line of an end portion in the axial direction in which local variation of the end portion in the axial direction of the developed outer peripheral surface is reduced as the reference position. The appearance inspection apparatus according to claim 1, wherein the approximate line is calculated as a linear straight line that approximates an end portion in an axial direction. When an error between the axial end and the approximate line calculated based on the axial end is larger than an allowable value, the position of the axial end is set as the reference position. The appearance inspection apparatus according to claim 1 or 2, wherein

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