JPH11101750A - Detection of foreign matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foreign matter detecting method not detecting an uneven shape present on a normal surface as a normal shape as foreign matter by mistake and capable of detecting only foreign matter with high accuracy. SOLUTION: Offset quantity for aligning the focus of the lens part 7a of an imaging camera 7 is set at the point above the upper surface of an article 1 to be inspected and a control part 12 controls the lens part 7a through a control circuit 11 so as to align the focus with the position determined based on the offset quantity. A timing circuit 9 is controlled to allow a stroboscopic light source 8 to emit light to perform oblique illumination and the image of the whole upper surface of the article 1 to be inspected is imaged under this oblique illumination by the imaging camera 7. An image conforming part 10 converts the taken-in image to a variable density image and scans the interior of the inspection region for inspecting foreign matter set to the variable density image to calculate a differential value which is, in turn, compared with a threshold value to detect a region where the differential value exceeds the threshold value as foreign matter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter detection method.

[0002]

2. Description of the Related Art Conventional object detection methods are disclosed in
No. 204 is disclosed. In this method, as shown in FIG. 14, two illuminating devices 2 and 2 placed across the inspection object 1 emit light one by one to produce shadows A and B on the inspection object 1, and the imaging camera 3 and the image A luminance histogram of shadows A and B is obtained by the recognition device 4. Then, the presence or absence of the inspection object 1 is accurately detected by comparing the luminance histograms when the two illumination devices 2 and 2 irradiate.

[0003]

In the object detection method described above, when the flat portion 6 on which the inspection object 1 is placed has an uneven shape, the unevenness is detected even though the inspection object 1 does not exist. There is a possibility that shading occurs and this shading is erroneously detected as the inspection object 1. In other words, when foreign matter detection is performed using such a conventional object detection method, it is not possible to discriminate the irregular shape existing as a normal shape on the normal surface from the irregular shape due to the foreign matter, and all of them are erroneously detected as foreign matter. There is a possibility that it cannot be adopted as a foreign matter detection method.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to prevent an irregular shape existing as a normal shape on a normal surface from being erroneously detected as a foreign substance. Another object of the present invention is to provide a foreign matter detection method capable of detecting only a foreign matter with high accuracy. A second object of the present invention is to provide, in addition to the object of the first invention, a foreign matter detection method capable of always imaging an object under the same conditions even when the thickness of the object changes. is there.

A third object of the present invention is to provide, in addition to the objects of the first and second aspects, a foreign matter detection method capable of distinguishing foreign matter even if a glossy surface exists on the surface of the inspection object. Is to provide. A fourth object of the present invention is to provide a foreign object detection method capable of recognizing the size and shape of a foreign object and grasping the surface state of the foreign object, in addition to the objects of the first and second embodiments.

A fifth object of the present invention is to provide, in addition to the objects of the first and second aspects of the present invention, a foreign object detecting method capable of distinguishing the state of the shape and material and type of the foreign object with high accuracy. It is in. The object of the invention of claim 6 is that
In addition to the objects of the first and second aspects of the present invention, it is another object of the present invention to provide a foreign matter detection method capable of determining an appropriate offset distance only by the thickness of a loaded inspection object.

[0007] The object of the invention of claim 7 is, in addition to the object of the invention of claim 2, in the case where the thickness of the inspection object is not constant, or when the loading height is changed due to foreign matter mixing or the like. An object of the present invention is to provide a foreign matter detection method capable of calculating an appropriate offset distance by a calculation formula. The object of the invention of claim 8 is that, in addition to the objects of the inventions of claims 1 and 2, even when the size of the inspection object changes due to loading, the inspection area can always cover the entire inspection object. An object of the present invention is to provide a foreign matter detection method.

The object of the ninth aspect of the present invention is to provide, in addition to the object of the eighth aspect, a foreign matter detection method capable of detecting a stacking deviation from an image of a preceding inspection object. It is in. According to a tenth aspect of the present invention, in addition to the object of the eighth aspect, in the image for foreign matter detection, the edge detection for determining the position of the detection target is performed by setting the edge detection area. An object of the present invention is to provide a foreign matter detection method capable of detecting a foreign matter based on the position of the immediately preceding inspection object even when foreign matter cannot be present due to the presence of the foreign matter.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, an imaging camera with a focus lens is arranged so as to face the upper surface of an object to be inspected.
A light source is installed diagonally above the object to be inspected which has an uneven shape on the upper surface, and the imaging camera is focused on a point offset by a certain distance upward with respect to the upper surface of the object to be inspected. On the other hand, oblique illumination is performed to image the upper surface of the object to be inspected with an imaging camera, a grayscale image is obtained from the captured image, a differential value of the grayscale image is obtained, and the obtained differential value and a preset threshold are obtained. It is characterized in that a foreign substance which is not the above-mentioned uneven shape is detected by comparing the value with a value.

According to a second aspect of the present invention, in the first aspect of the present invention, the upper surface of the inspection object is imaged by an imaging camera in a state where the focus is set on the upper surface of the inspection object and oblique illumination is performed by a light source. The distance between the upper surface of the object to be inspected and the imaging camera is obtained by obtaining the grayscale image from and calculating the grayscale image, and the distance to be offset upward with respect to the upper surface of the object is determined based on the distance. It is characterized by doing.

According to a third aspect of the present invention, in the first or second aspect of the present invention, another light source is disposed so as to face the upper surface of the inspection object, and oblique illumination is applied to the inspection object to detect a foreign substance. Before or after performing the imaging of the upper surface of the inspection object with the imaging camera, the upper surface of the inspection object is imaged under illumination by the another light source to obtain a gray image of the inspection object, and the differential value of the gray image is obtained. Is subtracted from the differential value of the grayscale image obtained by imaging under the oblique illumination, and the foreign matter surface and the glossy surface on the upper surface of the inspection object are selected from the subtraction result.

According to a fourth aspect of the present invention, in the first or second aspect of the invention, when the thickness of the foreign matter on the surface of the inspection object is limited, after detecting the foreign matter, the imaging camera is focused on the upper surface of the foreign matter and again. It is characterized by imaging. According to a fifth aspect of the present invention, in the invention of the first or second aspect, a focus lens having a zoom function is used, and after detecting the foreign matter, the imaging camera is moved so as to be positioned above the foreign matter, thereby processing the grayscale image. By calculating the size of the foreign matter, the zoom function of the focus lens is operated so as to obtain an angle of view corresponding to the size of the foreign matter, and the foreign matter is imaged after focusing on the foreign matter.

According to a sixth aspect of the present invention, in the first aspect of the invention, when one or a plurality of inspection objects are stacked and the inspection of the inspection object facing the imaging camera is performed, the inspection object has a constant thickness. In this case, the offset distance is obtained based on a function of the thickness of the inspection object. According to a seventh aspect of the present invention, in the second aspect of the present invention, when one or a plurality of inspection objects are stacked and the inspection of the inspection object facing the imaging camera is performed, the loading height differs depending on each inspection object. In the case, after imaging for obtaining a distance between the upper surface of the inspection object and the imaging camera, a length of a shadow extending from an outer edge of the inspection object is obtained from a grayscale image obtained from the captured image, and the length of the shadow is determined. After calculating the height of the object from the angle of oblique illumination, the height, the distance, the focal length and the effective diameter of the focus lens are offset upward with respect to the upper surface of the object as a function. It is characterized in that the distance is determined.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, the edge inspection area set for confirming the current position of the inspection object is replaced with an outer edge of the inspection object imaged in the previous inspection. It is characterized by setting based on the detection position. According to a tenth aspect of the present invention, in the invention of the eighth aspect, when the edge for position recognition of the inspection object to be inspected this time cannot be detected, the outer edge detection position of the inspection object captured in the previous inspection. Based on
It is characterized in that an inspection area for detecting a foreign substance is set.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below with reference to embodiments. (Embodiment 1) FIG. 1 is a schematic configuration diagram of an inspection apparatus using the present embodiment. For example, an inspection object 1 having a concave and convex shape such as a groove pattern on an upper surface such as a tile is mounted on an inspection table (not shown). Z)
The inspection camera 7 includes a CCD camera arranged to face the upper surface of the inspection object 1 and is inclined at a predetermined angle with respect to the upper surface of the inspection object 1. A strobe light source 8 that is disposed above and illuminates the upper surface of the inspection object 1 with oblique light, a timing circuit 9 that drives the strobe light source 8, and an image recognition unit 10 that processes an image captured by the imaging camera 7. , Lens unit 7 of imaging camera 7
The camera includes a focus mechanism provided in a, a lens control circuit 11 for controlling an electric drive unit of the zoom mechanism, and a control unit 12 for integrally controlling the image recognition unit 10, the lens control circuit 11, and the timing circuit 9. The imaging camera 7 is provided with a drive unit (not shown) that is movable in the X and Y directions, and can move in position under the control of the control unit 12.

In this embodiment, the offset amount (a) for adjusting the focus of the lens unit 7a of the imaging camera 7 to a point above the upper surface of the inspection object 1 in order to remove the influence of the uneven shape. And the offset amount (a)
The control unit 12 controls the lens unit 7a through the lens control circuit 11 so that the focus is set at the position determined by. Next, the timing circuit 9 is controlled to perform oblique illumination by the strobe light source 8, and an image of the entire upper surface of the inspection object 1 is captured by the imaging camera 7 under the oblique illumination.

Here, since the focus is adjusted to the position determined by the offset amount (a), the groove pattern which is a normal uneven shape is out of focus, so that the image is blurred and the foreign matter X is conversely imaged. Foreign matter X if present
Will be clearly focused. This image signal is taken into the image recognition unit 10. Image recognition unit 10
Converts the captured image into a gray-scale image, sets a predetermined inspection area (window) for detecting foreign matter in the gray-scale image, scans the inspection area to obtain a differential value, and compares the differential value with the obtained differential value in advance. By comparing the threshold value with a predetermined threshold value, a part whose differential value exceeds the threshold value is detected as a foreign substance.

As described above, according to the present embodiment, even if the upper surface of the inspection object 1 has an irregular shape such as a normal groove pattern,
Only the foreign matter X can be detected with high accuracy.
Next, an example for setting the offset amount a in the present embodiment will be described below. First, the inspection object 1 is loaded on the inspection table, and detection of foreign matter of the inspection object 1 facing the imaging camera 7 is performed. When the thickness of the inspection object 1 is constant (T1), The following control is performed.

The imaging camera 7 through the lens control circuit 11
Of the inspection object 1 as shown in FIG.
Focus on the upper surface of
The focus is shifted upward by the offset amount a calculated by the function of (T1), and the above-described imaging for detecting a foreign substance is performed. When the distance L between the imaging camera 7 and the inspection object 1 is changed by repeating the lamination, the offset amount is determined by a = f (T1).

Here, the equation for determining the offset amount a is shown in detail as follows: a = {[Lf (nA + 1)] / (nfa + L)} − T1 (1) (L: distance T1: thickness of inspection object 1)
f: focal length A: effective diameter of the lens) The example of FIG. 2 is a case where the camera position is constant and the thickness of the inspection object 1 is always constant, but the camera position is fixed and the thickness T
If 1 is not constant, the distance between the inspection object 1 and the imaging camera 7 changes. Therefore, as shown in FIG. 2, simply moving the focus upward by a certain distance does not make the offset amount a constant.

Therefore, as shown in FIG. 3, before imaging for detecting foreign matter, the lens unit 7a of the imaging camera 7 is controlled through the lens control circuit 11 under the control of the control unit 12 to obtain the image shown in FIG. As shown in (2), the upper surface of the object 1 is imaged by the imaging camera 7 while the focus is set on the surface of the object 1 and obliquely illuminated by the strobe light source 8, and the image recognition unit 10 obtains a grayscale image from the imaged image. Then, a distance L between the upper surface of the inspection object 1 and the imaging camera 7 is obtained by arithmetically processing the grayscale image. Thereafter, the focus is moved upward by a predetermined offset amount a from the distance L.

The principle in this case will be described in detail. First, from the above equation (1), the offset amount a is set to 0 (indicating a state where the inspection object 1 is in focus), and the equation for calculating the distance L is as follows. L = (nfA.T1) / [f (nA + 1) -T1] (2) Here, T1 is obtained by the following method.

First, before imaging for performing a foreign substance inspection, oblique illumination is performed by a strobe light source 8 as shown in FIG. 4A, and the length s of the shadow of the inspection object 1 formed by the illumination is imaged. The length and strobe light source 8
Is obtained from the inclination angle θ of the following equation: T1 = s · tan θ. By substituting the obtained T1 into equation (2), L is obtained,
The focus is moved upward from this L by a predetermined offset amount a.

As a result, a constant offset amount a can be ensured even for the test object 1 shown in FIG. 3B whose thickness is smaller than that of the test object 1 of FIG. 3A. According to the method shown in FIG. 3, even if the thickness T1 of the inspection object 1 changes as shown in FIG. for,
It is possible to capture an image out of focus in a normal uneven shape (groove pattern). By the way, even when the loading height is not constant due to not only a change in the thickness of the inspection object 1 but also foreign matter contamination, the thickness (height) T1 of the inspection object 1 and the inspection object 1 and the imaging camera 7 are determined by the above-described method. Is calculated, and the distance L between the imaging camera 7 and the object 1 is calculated.
Using the thickness T1, the focal length f of the lens portion 7a, and the effective diameter A as a function f (T1, L, f, A), the offset amount a is obtained by the above equation, and the focus is moved upward by the obtained offset amount a. You may make it do.

According to the above-described method, even when the height of the inspection object 1 is not constant, or when the loading height changes due to a foreign substance or the like, an appropriate offset amount a can be obtained by the calculation formula.
Can be requested. On the other hand, when the thickness of the foreign matter X of the inspection object 1 is limited, after detecting the foreign object, the inspection object is used to identify the shape such as the size, outer shape, and height of the foreign object X and the state of the material and the type. After detecting the foreign matter X on the surface 1, the focus is set on the upper surface of the foreign matter X from the state where the focus is set corresponding to the offset amount a of the imaging camera 7 as shown in FIG. In this case, the focus setting distance La is obtained from the offset amount a, the thickness of the foreign matter X, and the distance L to the inspection object 1.

By imaging the foreign matter X in focus, the size and shape of the foreign matter X can be recognized, the surface state of the foreign matter X can be grasped, and the analysis of the cause of the foreign matter X can be performed. Note that if the foreign substance X is magnified and imaged, it is possible to identify the shape of the foreign substance X, such as the size, outer shape, and height, and the state of the type of the material with high accuracy. Then, based on the detection information of the image recognition unit 10 after foreign matter detection, the imaging camera 7 is moved from the position of FIG. 6A (the center of the imaging screen) under the control of the control unit 12 as shown in FIG. The foreign matter X is moved upward, and the zoom mechanism of the lens unit 7a is operated to move the foreign matter X.
Should be magnified.

A foreign substance inspection area (window) is set in an image captured by the imaging camera 7 for detecting the foreign substance X. When sequentially inspecting the loaded inspection objects 1, depending on the loading position. When the distance between the imaging camera 7 and the inspection object 1 changes and the inspection object 1 is imaged at the same angle of view, the size of the image captured by the imaging camera 7 is
Will change depending on the position of.

Therefore, an area setting is performed in advance, and a foreign substance inspection area for the inspection object 1 to be actually inspected is secured by using the area setting.
Even if the size of the image of the inspection object 1 changes depending on the loading position, the foreign object inspection area can always cover the entire inspection object 1. That is, as shown in FIG. 7, when setting the area, the image of the inspection object 1 at the loading position closest to the imaging camera 7 is captured.
The outer edge of the density image obtained from this image is detected from the differentiation processing, and the X and Y coordinates for determining the inspection area are calculated. Here, the inspection area is divided into four so that the maximum image is divided into four equal parts.
One area W ₁ to _W-4 as it is set, the outer edge (X1 , Y1 , X2 , Y2 ), X1
, Y1 The inspection areas W ₁ and W ₂ are determined by
2 , Y2 To set inspection areas W ₃ and W ₄ .

After this setting, at the time of actual inspection, the image obtained by imaging the inspected object 1 is converted into a grayscale image by the image recognition unit 10, and the grayscale image is differentiated to obtain the image of the inspected object 1. (X1 , Y1 , X2
, Y2 ) Is calculated and set in the object to be inspected 1 in the image in the form that along the two sides of the outside contour edges examination region W ₁ to _W-4, which is the set on the basis of the calculated coordinate.

Here, the method of calculating the coordinates of the outer edge will be described in detail. First, for example, in the captured image as shown in FIG. 8A, the upper left coordinate is (0, 0), and the lower right coordinate is (255, 232). ), The coordinates of the outer edge can be obtained in this range. The inspection area for recognizing the coordinates of the outer edge is detected as (X1, X2) and (X2, Y2) by providing an edge detection area for X coordinate detection and Y coordinate detection by specifying an absolute position. Then, from the detected coordinates, the lower right coordinate point A and the upper left coordinate point B can be determined, and by this determination, the inspection areas W _{1 to} W ₄ of the inspection object 1 are set as described above as illustrated. You can do it.

In this case, the inspection areas W _{1 to} W ₄ overlap as shown in FIG. 8A or 8B depending on the size of the captured image, and the size of the overlapping portion changes. The inspection area for detecting the foreign substance can cover the entire upper surface of the inspection object 1 even if the size of the image of the inspection object 1 is reduced as shown in FIG. Incidentally, since the inspection object 1 is loaded, the loading may be shifted. Therefore, in order to detect a stacking deviation, in the present embodiment, an edge detection area of the current inspection object 1 is set based on an edge detection position set for an image of the inspection object 1 immediately before. It is determined whether or not the edge can be detected to detect a stacking deviation.

That is, as shown in FIG.
Is performed, and the outer shape of the image of another inspection object 1 taken immediately before
The edge detection position is indicated by reference coordinates, for example, as shown in FIG.
X1 Inspection area with a width of ± M pixels with reference to
Wa is set for the current image as shown in FIG.
Set. The grayscale image in the edge inspection area Wa is differentiated.
It is determined whether or not the contour edge can be detected. FIG.
In 0 (b), this time X2 The coordinates of the outer edge are
Because it is within the inspection area Wa, the
It is not determined that the inspection is impossible and the next edge inspection area W of the inspection object 1 is not detected.
X2 is used as a reference coordinate for setting a. Register the different
After the object detection processing is completed, the inspection of all the inspection objects 1 is completed.
If not, the above processing is performed again. Also above
When the outer edge cannot be detected in the edge inspection area Wa
In this case, it is determined that the displacement amount of the inspection object 1 is M pixels or more.
You.

9 and 10, the edge detection area Wa is set based on the coordinates of the edge detection of the immediately preceding inspection object 1 in the edge detection area Wa. As shown in FIG. 12A, the area Wa is fixed, an edge detection area Wa is set and an edge detection is performed after the imaging of the object 1 to be inspected, and if the edge detection is successful, the next inspection is performed. The position coordinates Xn and Yn of the outer edge are registered for foreign object detection of the object 1. If the edge cannot be detected, the position coordinates Xn-1 of the outer edge registered at the time of the previous inspection of the inspected object 1 are registered. Based on Yn-1,
As shown in FIG. 12B, foreign matter detection is performed using the inspection area for foreign matter detection, and the position coordinates Xn−
1, Yn-1 are registered.

By using such a method, even if the edge detection for determining the position of the inspection object 1 in the inspection image cannot be performed due to the presence of the foreign matter X in the edge detection area Wa, etc. By setting an inspection area for foreign substance inspection using the data of the edge detection position of one image, foreign substance detection can be performed. By the way, in the above method, the outer edge detection position and the position coordinates after the second time are used, but for the first time, the processing is performed by setting the edge detection area by the absolute position.

(Embodiment 2) In the case of Embodiment 1 described above, if the surface of the inspection object 1 has a glossy surface made of water or oil, it cannot be distinguished from the surface on which the foreign matter X exists. In some cases, only foreign matter cannot be detected. Therefore, in the present embodiment, as shown in FIG. 13, a light source (of course, a strobe light source) 1 that emits light continuously and directly facing the upper surface of the inspection object 1.
3 was installed, and only the foreign matter X was extracted by the following method.

Next, this embodiment will be described. First, in this embodiment, the lens unit 7a of the imaging camera 7 is controlled through the timing circuit 9 under the control of the control unit 12 so as to focus on the surface of the inspection object 1 before performing imaging for detecting foreign matter. The upper surface of the inspected object 1 is imaged by the imaging camera 7 in a state where the object 1 is obliquely illuminated by the strobe light source 8, and the image recognizing unit 10 obtains a grayscale image from the captured image, and performs arithmetic processing on the grayscale image to thereby obtain an The distance L between the upper surface and the imaging camera 7 is obtained. Thereafter, the focus is moved upward by a predetermined offset amount a from the distance La.

Thereafter, the timing circuit 9 is controlled to perform oblique illumination by the strobe light source 8, and an image of the entire upper surface of the inspection object 1 is captured by the imaging camera 7 under the oblique illumination. In this case, the brightness of the surface when the foreign matter X exists on the upper surface of the inspection object 1 becomes dark. Also, when the glossy surface Y exists as shown in FIG. 13, the brightness becomes dark. Therefore, when foreign matter detection is performed using this image, it cannot be distinguished from the glossy surface Y.

Then, the illumination of the strobe light source 8 is stopped, the illumination of the light source 13 is performed, and an image is taken by the imaging camera 7. In this case, the brightness of the surface where the foreign matter X exists does not change,
The brightness of the glossy surface Y becomes bright. Therefore, the surface on which the foreign matter X is present and the glossy surface Y are identified from the image data obtained by capturing the image under the oblique illumination first and the image data obtained by capturing the image under the illumination facing the current time, As a result, it is possible to detect the foreign matter X with high accuracy without erroneously detecting the glossy surface Y as the foreign matter X when comparing the differential value of the grayscale image with the threshold value.

In this embodiment, the first embodiment is also used.
It is needless to say that the method of determining the offset amount a, the method of recognizing foreign matter, the method of setting the detection area, the method of setting the edge detection area, and the like can be used.

[0040]

According to the first aspect of the present invention, an imaging camera with a focus lens is arranged so as to directly face an upper surface of an object to be inspected, and a light source is installed obliquely upward with respect to the object having an uneven shape on the upper surface. The imaging camera is focused on a point offset by a certain distance upward with respect to the upper surface of the inspection object, and the light source illuminates the inspection object with oblique light to image the upper surface of the inspection object with the imaging camera. Since a grayscale image is obtained from the captured image, a differential value of the grayscale image is obtained, and the obtained differential value is compared with a preset threshold to detect a foreign substance that is not the above-mentioned uneven shape. Even if there are irregularities such as patterns on the normal surface of the object to be inspected, there is an effect that only foreign matter can be detected with high accuracy without being erroneously detected as foreign matter.

According to a second aspect of the present invention, in accordance with the first aspect of the present invention, the upper surface of the inspection object is imaged by an imaging camera in a state where the focus is set on the upper surface of the inspection object and oblique illumination is performed by a light source. The distance between the upper surface of the object to be inspected and the imaging camera is obtained by obtaining the grayscale image from and calculating the grayscale image, and the distance to be offset upward with respect to the upper surface of the object to be inspected is determined based on the distance. Therefore, even if the thickness of the object to be inspected changes, the offset distance can be kept constant, and the object to be inspected can always be imaged under the same conditions.

According to a third aspect of the present invention, in the first or second aspect of the present invention, another light source is disposed so as to face the upper surface of the inspection object, and oblique illumination is applied to the inspection object to detect a foreign substance. Before or after performing the imaging of the upper surface of the inspection object with the imaging camera, the upper surface of the inspection object is imaged under illumination by the another light source to obtain a gray image of the inspection object, and the differential value of the gray image is obtained. Is subtracted from the differential value of the grayscale image obtained by imaging under the oblique illumination, and the foreign matter surface and the glossy surface on the upper surface of the inspection object are selected based on the subtraction result. Even if there is a glossy surface due to the adhesion of oil or the like, there is an effect that foreign matter can be identified and the accuracy of foreign matter detection can be improved.

According to a fourth aspect of the present invention, in the first or second aspect of the invention, when the thickness of the foreign matter on the surface of the inspection object is limited, after detecting the foreign matter, the imaging camera is focused on the upper surface of the foreign matter and again. Since the image is taken, the size and shape of the foreign matter can be recognized, the surface state of the foreign matter can be grasped, and the effect of pursuing the cause of the foreign matter can be analyzed. Claim 5
The invention according to claim 1 or 2, wherein the focus lens having a zoom function is used, and after detecting the foreign matter, the imaging camera is moved so as to be positioned above the foreign matter,
Since the size of the foreign matter is calculated by processing the grayscale image, the zoom function of the focus lens is operated so as to have an angle of view corresponding to the size of the foreign matter, and the foreign matter is imaged after focusing on the foreign matter. There is an effect that the shape such as the size, outer shape, and height of the foreign matter and the state such as the material and the type can be identified with high accuracy.

According to a sixth aspect of the present invention, in the first aspect of the present invention, when one or more inspection objects are stacked and the inspection of the inspection object facing the imaging camera is performed, the inspection object has a constant thickness. In the case of having an object, since the offset distance is obtained based on the function of the thickness of the inspection object, an appropriate offset distance can be obtained only by the thickness of the inspection object to be loaded. Has the effect that the offset distance can be determined.

According to a seventh aspect of the present invention, in the second aspect of the present invention, when one or a plurality of inspected objects are stacked and the inspection of the inspected object facing the imaging camera is performed, the height of each of the inspected objects is changed. If it differs depending on the object, after imaging for obtaining the distance between the upper surface of the inspection object and the imaging camera, the length of the shadow extending from the outer edge of the inspection object is obtained from the grayscale image obtained from the captured image, and the shadow is obtained. After calculating the height of the test object from the length and the angle of the oblique illumination, the height, the distance, the focal length and the effective diameter of the focus lens as a function of the upper side with respect to the upper surface of the test object. Since the offset distance is determined, it is possible to calculate an appropriate offset distance by using a calculation formula even when the thickness of the inspection object is not constant or when the load height changes due to the inclusion of foreign matter. effective.

According to an eighth aspect of the present invention, in the first or second aspect of the present invention, when one or more inspection objects are stacked and the inspection of the inspection object facing the imaging camera is performed, the inspection object to be inspected this time is performed. Since the inspection area set for the image of the inspection object is set so as to include the entire upper surface of the inspection object even if the position of the inspection object changes, the size of the inspection object may change due to loading. This has the effect that the inspection area can always cover the entire inspection object.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, the edge inspection area set for confirming the current position of the inspection object is replaced with the outer edge of the inspection object imaged in the previous inspection. Since the setting is made with reference to the detection position, there is an effect that the stacking deviation can be detected from the image of the immediately preceding inspection object. According to a tenth aspect of the present invention, in the invention of the eighth aspect, when an edge for position recognition of the inspection object to be inspected this time cannot be detected, an outer edge detection position of the inspection object captured in the previous inspection. The inspection area for detecting foreign matter is set based on the reference, so that in the image for foreign matter detection, the edge detection for determining the position of the object to be detected is performed at the position where the edge detection area is set. Even if it is not possible, foreign matter can be detected based on the position of the previous inspection object.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus using a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an offset amount determining method according to the first embodiment;

FIG. 3 is an explanatory diagram of a focus distance setting method according to the first embodiment;

FIG. 4 is an explanatory diagram of another offset amount determination method according to the first embodiment;

FIG. 5 is an explanatory diagram of focus control for foreign matter recognition according to the first embodiment;

FIG. 6 is an explanatory diagram of a foreign matter enlargement recognition method according to the embodiment.

FIG. 7 is a flowchart of an inspection area setting method according to the embodiment.

FIG. 8 is an explanatory diagram of an inspection area setting method according to the embodiment.

FIG. 9 is a flowchart of an edge inspection area setting method of the above.

FIG. 10 is an explanatory diagram of an edge inspection area setting method according to the embodiment.

FIG. 11 is a flowchart of a foreign matter inspection area setting method according to the first embodiment;

FIG. 12 is an explanatory diagram of a foreign matter inspection area setting method according to the embodiment.

FIG. 13 is a schematic configuration diagram of an apparatus using Embodiment 2 of the present invention.

FIG. 14 is a schematic configuration diagram of an apparatus using a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection object 7 Imaging camera 7a Lens part 8 Strobe light source 9 Timing circuit 10 Image recognition part 11 Lens control circuit 12 Control part X Foreign matter

Claims (10)

[Claims] An imaging camera with a focus lens is arranged so as to face the upper surface of an object to be inspected, and a light source is installed obliquely upward with respect to the object having an uneven shape on the upper surface. The focus of the imaging camera is adjusted to a point offset by a certain distance upward with respect to and the oblique illumination is performed on the inspection object by the light source, and the imaging camera captures the upper surface of the inspection object. A foreign matter detection method comprising: obtaining a shaded image, determining a differential value of the shaded image, and comparing the determined differential value with a preset threshold to detect a foreign matter having no irregularities. 2. An image pickup camera captures an image of an upper surface of an inspection object under a condition in which the upper surface of the inspection object is focused and is obliquely illuminated by a light source, obtains a gray image from the captured image, and processes the gray image. 2. The foreign matter according to claim 1, wherein a distance between the upper surface of the object to be inspected and the imaging camera is obtained, and a distance to be offset upward with respect to the upper surface of the object to be inspected is determined based on the distance. Detection method. 3. A method in which another light source is disposed so as to face the upper surface of the inspection object, oblique illumination is performed on the inspection object for foreign substance detection, and the upper surface of the inspection object is imaged by an imaging camera. Or later, the upper surface of the inspection object is imaged under illumination by the different light source to obtain a gray image of the inspection object, and the differential value of the gray image is obtained by imaging under the oblique illumination. 3. The foreign matter detection method according to claim 1, wherein the foreign matter surface and the glossy surface on the upper surface of the inspection object are selected from the result of subtraction from the differential value of the image. 4. The method according to claim 1, wherein when the thickness of the foreign matter on the surface of the inspection object is limited, after detecting the foreign matter, the upper surface of the foreign matter is focused on by the imaging camera and the image is taken again.
Or the foreign matter detection method according to 2. 5. Using a focusing lens having a zoom function, moving the imaging camera so as to be positioned above the foreign matter after detecting the foreign matter, calculating the size of the foreign matter by processing a grayscale image, and 3. The foreign matter detection method according to claim 1, wherein the zoom function of the focus lens is operated so as to have an angle of view corresponding to the size of the foreign matter, and the foreign matter is imaged after focusing on the foreign matter. 6. When the inspection object has a constant thickness when one or more inspection objects are loaded and the inspection object facing the imaging camera is inspected, the thickness of the inspection object is determined. 2. The foreign matter detection method according to claim 1, wherein the offset distance is obtained based on the function of: 7. An inspection apparatus according to claim 1, wherein when one or a plurality of inspection objects are loaded and an inspection of the inspection object facing the imaging camera is performed, if the loading height is different for each inspection object, the upper surface of the inspection object and the imaging camera After the imaging for obtaining the distance between the object, the length of the shadow extending from the outer edge of the inspection object is obtained from the grayscale image obtained from the captured image, and the inspection object is obtained from the length of the shadow and the angle of the oblique illumination. After calculating the height, the distance to be offset upward with respect to the upper surface of the inspection object is determined as a function of the height, the distance, the focal length of the focus lens, and the effective diameter. The method for detecting foreign matter according to claim 2. 8. When one or more inspection objects are loaded and an inspection is performed on the inspection object facing the imaging camera, an inspection area set for an image of the inspection object to be inspected this time is covered. 3. The foreign matter detection method according to claim 1, wherein the setting is performed so as to include the entire upper surface of the inspection object even when the position of the inspection object changes. 9. An edge inspection area set for confirming the current position of the object to be inspected is set with reference to an outer edge detection position of the object to be inspected imaged in the previous inspection. The foreign matter detection method according to claim 8, wherein 10. A foreign object is detected on the basis of a contour edge detection position of an object imaged in a previous inspection, when an edge for position recognition of the object inspected this time cannot be detected. 9. The foreign matter detection method according to claim 8, wherein an inspection area for setting is set.