JPH04166749A - Defect inspecting method - Google Patents

Abstract

PURPOSE:To improve the reliability and the efficiency of defect detection in movement by obtaining the automatic detection of the defect of a material to be inspected and the still image containing the defect by using the image signal of the same TV camera. CONSTITUTION:A material to be inspected 31 such as paper in movement is illuminated with lighting devices 32 and 33. The image of the material to be inspected 31 in the entire width direction is picked up with a defect detecting TV camera 2 wherein a linear image sensor is a light receiving part under the illumination. The image signal is recorded in a frame memory 43 in synchronization with the moving speed of the material to be inspected 31. At the same time, the presence or absence of the defect is judged in first and second defect judging circuits 10 and 12. At every time the defect is detected, the detected defect signal is imparted into the frame memory 43. Writing is stopped with a specified delay time being provided. At this time, the image including the defects accumulated in the memory 43 is displayed on a monitor 46 as the still image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Fields] The present invention is applicable to test materials whose inspection surfaces are plain, such as paper, films, metal foils, and nonwoven fabrics, or to materials whose inspection surfaces are plain, such as gravure printed materials. The present invention relates to a defect inspection method for inspecting defects on printed materials.

[Prior Art] Instead of a defect inspection performed by a skilled worker by directly visualizing a material to be inspected, a technique is known in which, for example, the quality of printing is determined by pattern matching. This technique was implemented as follows.

First, a printed material determined to be good by visual inspection or the like is prepared, and a monochrome image of the printed material is captured using a television camera. Next, the camera's video signal is processed to extract the print outline pattern. Then, the enlarged outline pattern obtained by subjecting this outline pattern to vertical and horizontal enlarging processing is stored in a memory as a mask pattern. This enlargement process allows some errors based on printing variations and movement accuracy of printed matter to be tolerated. Thereafter, the printed matter to be inspected is imaged by the television camera. Then, a contour pattern extracted by a contour extraction means that processes the video signal of this camera,
The readout of the mask patterns stored in the memory is synchronized, and pattern matching is performed by comparing them by a pattern matching means.

In other words, by such a pattern matching method,
Information for determining the quality of printing can be obtained.

Furthermore, color still image display devices that display part of a printed surface as a color still image on a television monitor are also known. In this device, a color television camera is movably attached to a traverse rail that is installed opposite the printing surface of a moving printed material and extends in the width direction of the printed material, and the camera is moved to an arbitrary position to position the printed surface at a predetermined position. The area is imaged under hotpot emission, and a color still image is displayed on a television monitor connected to the camera. Therefore, when using this color still image display device, arbitrary positions on the printed matter can be sampled and monitored as still images without stopping the movement of the printed matter.

[Issue 8 to be solved by the invention] In the defect detection using pattern matching described above, defects are detected by comparison with a mask pattern, so it is difficult to detect the type or shape of the detected defect. Can not. Therefore, there is a problem in that it is not possible to infer the cause of a defect from the inspection results using the defect detection technique described above and take appropriate measures to avoid the defect.

In addition, with the above-mentioned color still image display device, only a part of the printed surface is visible as a color still image, but since printing defects occur randomly, it is possible that the screen of the TV monitor contains some defects. There is no guarantee. therefore,
Even if such a color still image display device is used, it cannot be expected to save much labor in defect inspection, and it is only used for checking printing register. Note that if this color still image display device is used to continuously obtain still images in the width direction of the printed surface, it is possible to monitor the entire width of the printed surface. There is a problem in that the inspection speed becomes slow without increasing the moving speed of the robot.

An object of the present invention is to provide a defect inspection method that can improve the reliability and efficiency of defect inspection.

[Means for Solving the Problems] In order to achieve the above object, in the defect inspection method of the present invention, the inspected material to be moved is illuminated at the inspection position, and under this illumination, the inspected material is A television camera for defect detection uses a linear array image sensor as a light receiving section to capture images in all directions, and the video signal from this television camera is scroll-recorded in a frame memory in synchronization with the moving speed of the material to be inspected. In parallel, the video signal from the television camera is processed to determine the presence or absence of a defect in the material to be inspected, and each time a defect is detected by this defect determination, a defect detection signal is given to the frame memory to detect the defect. Writing to the frame memory is stopped with a predetermined delay from the point in time, and the image information including defects stored in the frame memory at this point is displayed as a static TF-image on the television monitor. It is something.

C Effect: The inspection surface of the moved specimen is illuminated at the inspection position. This illumination is performed to highlight defects on the inspection surface. Under this illumination, a defect detection television camera images the entire width of the inspection surface. This imaging enables photo-electrical conversion of information on the inspection surface as luminance information.

A defect detection device to which the output (video signal) of the defect detection television camera is supplied processes the video signal and determines whether or not there is a defect on the inspection surface. When it is determined that there is a defect, a defect detection signal is sent to the frame memory.

On the other hand, in parallel with the defect detection as described above, video signals from the camera are sequentially written into the frame memory. This writing is performed in synchronization with the moving speed of the test material. By such writing, video signals corresponding to an area of the inspection surface occupying a predetermined area in the moving direction of the inspected material are stored in the frame memory. The image information for one screen stored in this frame memory is scrolled every time the video signal is written.

When a defect detection signal is input to the frame memory based on the above-described defect detection, predetermined image information is frozen from that point on. Due to the above time delay, defective image information is stored in the frame memory. The still image information for one screen thus stored in the frame memory, including the defects, is displayed as a still image on the television monitor.

That is, information for automatically detecting defects on the inspection surface of the specimen being moved as described above, and information for displaying a still image of a predetermined area including the detected defects on a television monitor. Since the images are obtained using the same lighting and the same video signal from the same defect detection television camera, it is possible to reliably view the automatically detected defects as still images. By monitoring the detected defects, the type and shape of the defects can be known.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Reference numeral 31 in FIG. 1 denotes a printed sheet or continuous long object material printed by, for example, a gravure stamping device, which is moved from front to back on the paper surface on which FIG. 1 is drawn. Reference numeral 1 in FIG. 1 is a camera unit equipped with, for example, four television cameras 2 for detecting defects.
It is placed at an arbitrarily determined inspection position with respect to 1, facing the printed surface of the printed material 31 as the inspection surface.

At the inspection position, a first lighting device 32 facing the front surface (printing surface) of the printed material 31 and a second lighting device 33 facing the back surface of the printed material 31 are arranged. These lighting devices 32,33 are used to highlight imperfections and are
Depending on the material, one or both may be used simultaneously to illuminate the field of view of the camera unit 1.

Reference numeral 34 in FIG. 1 is a pulse generator provided so as to be in contact with the edge of the printed material 31 being moved, and this pulse generator detects movement information of the printed material 31.

Each defect detection TV camera 2 is arranged along the width direction (direction perpendicular to the moving direction) of the marking object 31, and each camera 2 uses a CCD linear array image sensor as a light receiving part. has been done. Each of these television cameras 2 can scan the entire print surface of the printed matter 31 in the width direction. The video signal output from each television camera 2 is subjected to pattern matching processing by the defect detection device 5 shown in FIG. 1, thereby determining the presence or absence of a defect.

The defect detection device 5 is provided individually for each television camera 2, and includes an AGC device 6, an amplifier 7, a contour extraction circuit 8, a first defect recognition section 9, a first defect determination circuit 10, and a second defect detection device. It is formed to include a recognition section 11 and a second defect determination circuit 12. Next, these will be explained.

The AGC device 6 is connected to the output end of the television camera 2, and is used to stabilize the transmission output against gain fluctuations of the defect detection device 5 as a whole. An amplifier 7 is connected to the output end of the AGC device 6 and is used to amplify the video signal from the television camera 2 that has passed through this device 6.

A contour extraction circuit 8 serving as contour extraction means is connected to the output terminal of the amplifier 7. This circuit 8 consists of a differential circuit,
Capturing all the signals output from TV camera 2,
Changes in this signal are emphasized to extract the contour pattern of the image.

The first defect detection section 9 includes a first pattern enlargement processing circuit 15 as a pattern enlargement processing means, a first mask pattern memory 16 as a first storage means, and a first pattern matching circuit 17 as a pattern matching means. It is formed from.

The first pattern enlargement processing circuit 15 is connected to the output end of the contour extraction circuit 17. This circuit 15 is a circuit for enlarging the signal related to the outline in the vertical and horizontal directions in order to allow for variations in printing of the stamp object 31 and errors due to feeding accuracy. Some errors based on expected variations and feeding accuracy of the printed matter 31 can be tolerated. This enlarged dimension is specified during initial setup. Then, this circuit 15 performs pattern enlargement processing on the outline pattern to form a pattern to be inspected.

The first mask pattern memory 16 is connected to the output end of the contour extraction circuit 8. This memory 16 is capable of being written to and read from, and stores mask contour patterns extracted by the contour extraction circuit 8 from printed matter determined to be good by visual inspection or other appropriate inspection. The memory 16 retains the mask outline pattern stored therein so as not to be changed while the same type of printed matter 31 is being inspected.

The first pattern matching circuit 17 connects the output terminal of the first pattern enlargement processing circuit 15 and the first mask pattern memory 16.
are connected to the output ends of the respective output terminals. This matching circuit 17 compares and matches the mask outline pattern read out from the first mask pattern memory 16 with the pattern to be inspected obtained by the first pattern enlargement processing circuit 15, and matches these patterns. This is a comparison to see if they match.

The first defect determination circuit 10 is connected to the output terminal of the first pattern matching circuit 17. This circuit 1
1, the first defect recognition section ascertains the size of the recognized defect information and determines whether or not it is a sexual defect. Furthermore, here, the term ``missing defect'' refers to a defect in which a part of the seal is missing or is blurred. The criterion size for determining this defect is designated to the determination circuit 10 at the time of initial setting.

The second defect recognition unit 11 includes a second pattern enlargement processing circuit 21 as a pattern enlargement processing means, a second mask pattern memory 22 as a second storage means, and a second pattern matching circuit as a second pattern matching means. It is formed from the circuit 23.

The second pattern enlargement processing circuit 21 is connected to the output end of the contour extraction circuit 8. This circuit 21 has the same W4 configuration as the first pattern enlargement processing circuit 15, and performs pattern enlargement processing on the outline pattern to form a mask enlargement pattern.

The second mask pattern memory 22 is connected to the output end of the second pattern enlargement processing circuit 21. This memory 22 is also capable of writing and reading,
This stores the mask enlarged pattern processed by the processing circuit 21 for printed matter that is determined to be good by visual inspection or other appropriate inspection. The enlarged mask pattern stored in the memory 22 is also held unchanged while the same type of printed matter is being inspected.

The second pattern matching circuit 23 is connected to the output end of the contour extraction circuit 8 and the output end of the second mask pattern memory 22, respectively. This matching circuit 23 is
The mask enlarged pattern read from the second mask pattern memory 22 and the printed matter 31 obtained by the contour extraction circuit 8
This method compares and matches the outline patterns of the stamps to determine whether these patterns match.

The second defect determination circuit 12 is connected to the output terminal of the second pattern matching circuit 23. This circuit 2
3 determines the size of the defect information recognized by the second defect recognition unit 11 and determines whether it is a flying defect or not. Note that the term "flying defects" here refers to defects caused by scattered ink, dirt, foreign matter, etc. adhering to areas other than predetermined printing areas. The determination standard size for this defect is determined by the determination circuit 12 at the time of initial setting.
specified.

The pulse output from the pulse generator 34 is supplied to each mask pattern memory 16, 22 and each defect determination circuit 10, 12 of the defect detection device 5 having the above configuration, and in response to this output, the defect detection device 5 is operated in synchronization with the moving speed of the printed matter 31.

Further, numeral 41 in FIG. 1 is an image forming means that processes the video signal from the television camera 2 in parallel with the defect detection device 5. This means 41 includes an A/D converter 42, a frame memory 43, a CPU 44, and a D/A converter 45. This image forming means 41 receives the pulse output from the pulse generator 34 to form a printed matter 3.
An image is formed from the video signal in synchronization with the moving speed of 1.

An A/D converter 41 is connected to the output terminal of the amplifier 7, and a frame memory 43 is connected to the converter 41. This memory 43 records the above video information and
It stores image information for a screen. That is, the frame memory 43 operates using the pulse output from the pulse generator 34 as a trigger signal, and each time this trigger signal is input, the frame memory 43 writes the video signal related to one scan of the television camera 2 while moving memory addresses one after another. Then, the video signals for a predetermined area along the moving direction of the printed matter 31 are accumulated. After the monochrome image information equivalent to one screen is stored, a write operation is performed to again store the video signal related to one scan of the television camera 2 in the storage element located at the first memory address. This is a configuration that performs so-called scroll recording.

This frame memory 43 and each of the above defect determination circuits 10.1
When the defect detection signal output from the defect detection circuit 10.12 is supplied to the frame memory 43, this memory 43 writes data with a predetermined delay from the input point of the defect detection signal. Configured to stop working. Note that the A/D converter 42 and the frame memory 43 are provided individually for each television camera 2.

The above writing stop control is performed by a CPU (central processing unit) 44 connected to each of the frame memories 43. The CPU 44 has a display buffer memory, and is configured to transfer the image information stored in the frame memory 43 at the time of stopping the writing from this memory 43 and store it in the display buffer memory. Furthermore, since the field of view of each television camera 2 may include different defects at the same time, the CPU 44 determines the timing of receiving the defect detection signal from the defect detection device 5 and outputs the defect detection signal at the earliest timing. The received image information in the frame memory 43 is transferred to the display buffer memory. A D/A converter 45 is connected to this C, PU 44.

A television monitor 46 is connected to the output end of the D/A converter 45 of the image forming means 41 having the above configuration. This monitor 46 displays the image information transferred to the display buffer 7 memory. This image display is performed with the defect positioned at the center of the monitor screen. For this reason, although not shown, the system path line connected to the CPU 44 has
A defect position X coordinate counter and a defect position Y coordinate counter are connected. The defect position X coordinate counter is reset by the start signal of the television camera 2, and the CPU 44
The defect position Y coordinate counter counts according to the pulse output of the pulse generator 34, and both of these counts are stopped by the CPU 44 based on the input of the defect detection signal. Thereafter, the CPU 44 reads the X and Y coordinate values to determine the position of the defect in the memory space, and based on this determines the position of the defect in the display memory buffer so that the defect is displayed in the center of the screen. It controls the transfer. Further, the television monitor 46 has a function of zooming up a part of the image, and the zooming is performed by specifying the X and Y coordinates of the defect position by the operator.

The CPU 44 has a notification device 4 such as a buzzer or a chime.
7 is connected, and is operated simultaneously with the above transfer.

Next, a case will be described in which the printed surface of the printed matter 31 is inspected using the defect inspection apparatus having the above configuration.

First, after performing the necessary initial setting operations, prints that have been determined to be good by visual inspection or other appropriate inspection are placed on the illumination device.
132 or 33 with the defect detection television camera 2, and the contour extraction circuit 8 extracts the contour pattern from the image of the good product (mask). 1 defect recognition section 9 and second defect recognition section 11, respectively.

In the first defect recognition unit 9, the contour pattern of the mask image output from the contour extraction circuit 8 is stored as a mask contour pattern in the first mask pattern memory 16,
It is recorded in this memory 16. In addition, the second defect recognition unit 1
1, the contour pattern of the mask image output from the contour extraction circuit 8 is enlarged by the second pattern processing circuit 21, and the resulting mask enlarged pattern is stored in the second mask pattern memory 22. , are recorded in this memory 22.

After setting the pattern related to such a mask image, the printed surface of the moving printed matter 31 is sent one after another into the field of view of the defect detection television camera 2 under illumination by at least one of the illumination devices 32 and 33, An image is taken by this camera 2. The video signal output from the television camera 2 passes through the AGC device 6 and the amplifier 7 and then passes through the contour extraction circuit 8. In this circuit 8, the contour pattern to be inspected is extracted, and this pattern is identified as the first defect. Recognition part 9
and the second defect recognition unit 11, respectively.

In the first defect recognition section 9, the contour pattern to be inspected outputted from the contour extraction circuit 8 is enlarged by a first pattern enlargement processing circuit 15. The resulting pattern to be inspected is supplied to a first pattern matching circuit 17.

The inputting of the pattern to this circuit 17 and the reading of the mask contour pattern related to the mask image from the first mask pattern memory 16 to the first pattern matching circuit 17 are performed at the same timing, so that both Compare and match patterns.

Then, if the pattern to be inspected has a defect, the enlarged pattern to be inspected will be
A part of the outline pattern related to the mask image protrudes. This protruding part is recognized as information about sexual flaws.

Next, this defect information is supplied to the first defect determination circuit 10, so that this circuit 10 determines whether or not the defect information is a defect.

Further, the contour pattern to be inspected of the video signal from the camera 2 supplied to the second defect recognition section 11 is supplied as it is to the second pattern matching circuit 23 without being subjected to enlargement processing. The input of the contour pattern to be inspected to this circuit 23 and the readout of the mask enlarged pattern related to the mask image from the second mask pattern memory 22 to the second pattern matching circuit 23 are performed at the same timing. is executed, thereby comparing and matching both patterns.

Therefore, if the pattern to be inspected has a defect, part of the contour pattern to be inspected protrudes from the mask enlarged pattern. This protruding part is treated as 4E, including information on flight defects. Since this defect information is supplied to the second defect determination circuit 12, this circuit 12
A determination is made as to whether the above defect information is a defect.

When determining that there is a defect, each defect determination circuit 10.12 sends a defect detection signal to the image forming means 41.

On the other hand, the video signal from the television camera 2 is simultaneously supplied to the image forming means 41 via the AGC device 6 and the amplifier 7, and this means 41 performs the defect pressure detection operation of the defect detection device 5 in parallel. Signal processed.

That is, the amplified video signal is A/D converted by the A/D converter 42 and then written to the frame memory 43. This writing to the memory 42 is executed one after another each time this signal is input to the image forming means 41 using the pulse output from the pulse generator 34 as a trigger signal. By scrolling recording to the frame memory 43 in synchronization with the moving speed of the printed matter, this memory 43
Since the video signal of the printing surface is accumulated in the moving direction, the video signal is converted into a monochrome image.

Then, when a defect detection signal is input to the image forming means 41 based on the defect detection described above, it is output at that point. A video signal containing defects due to such a time delay is recorded in the frame memory 43. Then, one screen worth of still image information, including defects, stored in the frame memory 43 due to the writing stop is transferred by the CPU 44 to the display buffer memory. This transferred image information is
Since the signal is D/A converted by the converter 45 and sent to the television monitor 46 as a video signal, the monoter 46 displays a still image including defects.

Further, since the CPU 44 operates the notification device 47 at the same time as the above transfer, the image display of the detected defect is notified.

By monitoring the defects displayed as still images on the monitor screen, it is possible to know the shape and symptoms of the defects, such as the type of the defect. Therefore, the operator can take appropriate measures to avoid the defects. It should be noted that by performing a zoom-up operation instructed as necessary during the above-mentioned monitoring, defects can be enlarged and displayed on the monitor screen for detailed viewing. In addition, in the above defect inspection, the operator, each time the notification device 47 makes a notification,
Since it is only necessary to monitor the television monitor 46, there is no need to continuously watch the television monitor 46, which reduces the workload.

Information for automatically detecting defects on the print surface of the printed matter 31 being moved as described above, and information for displaying a still image of a predetermined area including the detected defects on the television monitor 46. are obtained using the same illumination and the same video signal from the same defect detection television camera (therefore, the resolution of the sensor is the same) 2, so consistency between the defect and its still image can be ensured.

Therefore, automatically detected defects can be reliably viewed as still images.

Note that the illumination devices 32 and 33 for detecting defects are used to emphasize defects as much as possible, but if the illumination is even slightly different, it may become difficult to emphasize the defects and it may become impossible to detect the defects. It is known that even when displaying defects in images, the defects will not be displayed in the image unless the defects are emphasized as much as possible. Therefore, if a lighting device is not shared for defect detection and image display, the defects detected by the defect detection device may not be clearly displayed on the image. In addition, even if the lighting device is shared, the defect detection camera and the image capture camera are separate and their sensor resolutions are different, the defects will be clearly displayed on the image as well. It may not be done. However, since this detection device ensures consistency between the defect and its still image as described above, the detected defect is always displayed on the TV monitor 46 without causing the above problem.
It can be displayed stationary.

[Effects of the Invention] According to the defect inspection method of the present invention configured as described above, it is not possible to automatically detect defects in moving specimens, but to detect the defects each time they are detected. Since it is possible to reliably monitor the shape and symptoms of detected defects using still images, it is possible to improve the reliability and efficiency of defect inspection for the above-mentioned materials.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the configuration of a defect inspection device that implements the method of the present invention. 2. Television camera for defect detection, 5. Defect detection device, 3
1 Printed matter (test material), 32.33...Lighting device, 41
・Image forming means, 43・Frame memory, 46...Takehiko Suzue, patent attorney and representative for TV monitor applicant

Claims (1)

[Claims] A moving object to be inspected is illuminated at an inspection position, and under this illumination, an image of the object to be inspected is imaged over the entire width thereof with a defect detection television camera having a linear array image sensor as a light receiving section. , The video signal from this TV camera is scroll-recorded in the frame memory in synchronization with the moving speed of the material to be inspected, and in parallel with this recording, the video signal from the TV camera is processed to identify the defects of the material to be inspected. Determining the presence or absence of the defect, and providing a defect detection signal to the frame memory each time a defect is detected by this defect determination, and stopping writing to the frame memory with a predetermined delay from the time of detection of the defect, A defect inspection method characterized in that image information including defects stored in the frame memory at this point is displayed as a still image on a television monitor.