JPH0833357B2 - Method and apparatus for detecting defects in sheet-shaped test material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a sheet shape having a plurality of colors that are the same color in the width direction and periodically repeated in the longitudinal direction, that is, pinholes and black dots. The present invention relates to a method and apparatus for detecting dirt, foreign matter attached, streaks and the like.

[Conventional technology]

A thermal copying paper for color printing, for example, has recently been developed as a sheet-like material having a plurality of colors having the same color in the width direction and cyclically repeated in the length direction. This copy paper is a translucent PE with a thickness of several microns as shown in FIG.
T film 1, yellow Y, magenta M, cyan C,
It is made by coating several color inks such as black BL in stripes by printing so as to appear repeatedly in the longitudinal direction. The coating width for each color is 10
The length is about 0 to 1500 mm and is printed over substantially the entire width of the film 1, and the length of each color along the longitudinal direction of the film 1 is about 60 to 600 mm. The respective color inks of the thermal copying paper A are mixed by being sequentially transferred to the same pixel portion of the image receiving paper via a thermal head whose heat generation amount is controlled according to the density of the image. Then, a color print image is formed on the image receiving paper.

By the way, in the production of such a thermal copying paper, pinholes, black spots, stains, adhesion of foreign matter, uneven printing,
Defects such as streaks may occur, and it is necessary to detect such defects and take appropriate measures such as removal.

Therefore, conventionally, when determining the operating conditions at the time of starting the operation of the ink coating machine or during the operation, and further when rewinding after printing, the above-mentioned drawbacks can be seen by seeing through the thermal copying paper on the light board. Although visual inspection is generally performed, automatic detection of defects has not been performed in the past.

[Problems to be solved by the invention]

Therefore, in the conventional defect detection by visual inspection, there is a great possibility that the defect is overlooked, the fatigue of the operator is great, and skill is required.

By the way, in the defect detection of sheet-shaped test materials other than the thermal copying paper as described above, the test material is detected by a photoelectric conversion camera using a CCD image sensor or the like as an inspection method instead of visual inspection. It is known that scanning is performed and an image pickup signal from this camera is processed by an electronic circuit to detect a defect.

The sheet-shaped test material that is the target of such known defect automatic detection has a single background color. That is, the above-mentioned known defect automatic detection is possible under the condition that the amount of light incident on the camera is constant.

However, in the sheet-shaped test material in which a plurality of colors appear repeatedly in the longitudinal direction as the object of the present invention, the amount of light transmitted or reflected by each color is different. Therefore, if the above-mentioned known defect automatic detection is applied as it is, even if the same defect is present, the amount of incident light to the camera varies for each color, which causes overdetection and oversight of the defect. From
There is a problem that the accuracy of defect detection is significantly impaired and it cannot be used very much.

Therefore, the present invention, regardless of the variation of the incident light amount to the camera different for each color of the sheet-shaped test material, it is possible to automatically detect the defects included in each color, the detection speed is fast, and It is an object of the present invention to provide a method and apparatus for detecting a defect in a sheet-shaped test material that does not generate a defect undetectable region.

[Means for solving problems]

In order to achieve the above object, a method of detecting a defect of a sheet-shaped test material according to the present invention is a sheet-shaped test material having a plurality of colors that are the same color in the width direction and periodically repeated in the longitudinal direction. In the method of detecting a defect of a material, a part of the traveling sheet-shaped inspection material is illuminated with a constant amount of light, and the sheet-shaped inspection material is widthwise in this illumination position by a photoelectric conversion type camera. A plurality of preset threshold levels according to the light transmittance or the light reflectance of each color, which are provided corresponding to each of the above colors after scanning along the line and differentiating the image pickup signal of this camera. In the comparison means, the threshold level and the imaging differential signal for each color are compared and binarized, and the binarized comparison output is determined by the defect determination means provided for each color. Process and above It is characterized by performing the fault detection of the color in the viewing position of the camera.

Further, in order to achieve the same object, the defect detecting device for a sheet-shaped test material according to the present invention has a plurality of colors having the same color in the width direction and periodically repeated in the longitudinal direction. A light projector for illuminating a part of the sheet-shaped test material with a constant light amount, a photoelectric conversion type camera for scanning the sheet-shaped test material along its width direction at an illumination position of the light projector, and Differentiating processing means to which an image pickup signal from the camera is supplied and corresponding to each of the plurality of colors are provided, and the image pickup differential signals obtained by the differentiating processing means are separately supplied, and for each color. Threshold levels corresponding to the light transmittance or light reflectance of the color are individually set in advance, and a plurality of comparing means for comparing the supplied imaging differential signal with the threshold level and binarizing the plurality of comparing means are provided. Corresponding to each color And a plurality of selection means to which the comparison outputs of the respective comparison means are separately supplied, and a selection operation control means for selecting one of the selection means corresponding to the color of the visual field position of the camera, It is provided with a plurality of defect determining means which are provided corresponding to each of the plurality of colors and to which the comparison outputs passed through the selecting means are individually supplied.

[Action]

In the method of the present invention, the image pickup signal obtained by scanning the illumination position of the traveling sheet-shaped test material with the photoelectric conversion type camera along its width direction is differentiated. By this differentiation processing, a steep change point in the image pickup signal, in other words, defect information is found. Next, this differential signal is binarized. This binarization is performed by setting a plurality of comparison means, which are provided for each color of the material to be inspected, individually in advance in accordance with the light transmittance or the light reflectance of each color, and the threshold levels having different levels from each other. , And the image pickup differential signals for each color are compared and compared. As a result, the amount of light transmitted or reflected by each color of the material to be inspected is different, and the influence of the incident light on the camera is eliminated, even though the amount of light incident on the camera changes cyclically as the material to be inspected travels. At the same time, the defect information about the color scanned by the camera is detected without resetting the threshold level in the comparison means. Regarding the binarized comparison output (defect information) in this way, it is judged whether or not there is a defect in the judgment processing by the defect judgment means corresponding to the color scanned by the camera.

Based on the above, visual inspection for defects such as pinholes and stains contained in each color of the running sheet-shaped test material that has the same color in the width direction and multiple colors that appear repeatedly in the longitudinal direction periodically It can be detected automatically regardless of

According to this detection method, since the imaging differential signals are compared and binarized at the threshold level determined exclusively for each color as described above, each color reaches the field of view of the camera and is scanned. Since it is not necessary to reset the threshold level, and only the comparison output corresponding to the color of the camera visual field position is selected and processed by the defect determining means, the defect can be detected at high speed. Moreover, since it is equivalent to resetting the threshold level by selecting the comparison output as described above, the time required to reset the threshold level is not required in the defect detection at the adjacent color boundary part. is there. Therefore, in the defect detection at the color boundary portion, the threshold level is not set, or the defect detection for the color on the rear side in the traveling direction is not performed at the threshold level corresponding to the color on the front side in the traveling direction, and thus the defect There is no over-detection or oversight, and defects can be detected over the entire length in the traveling direction.

In the device of the present invention, the projector, the photoelectric conversion type camera, the differentiating means, the plurality of comparing means dedicated for each color, and the dedicated corresponding for each color are provided. Since a plurality of selection means, a selection operation control means, and a plurality of defect determination means provided corresponding to each color are provided, the above defect detection method can be implemented by the processing operation of these means. Therefore, according to the device of the present invention, regardless of the variation in the amount of incident light on the camera that differs for each color of the sheet-shaped test material, the defect automatically included in each color is not overdetected or overlooked, and high speed is achieved. It is possible to detect with, and not to generate the undetectable area of the defect.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 1 is a light-emitting PE which is a base paper for a sheet-shaped test material A (that is, a thermal copying paper for color printing in this embodiment).
In the coil of the T film, several kinds of color inks are coated on the feeding portion by a printing operation of the ink coating machine 2, for example, every 1 meter. A stripe pattern as shown in FIG. 2 is obtained by this coating, and as described above with reference to FIG. 2, yellow Y, magenta M, cyan C, and black BL color inks are cyclically distributed in the longitudinal direction of the RET film 1. Appearing in the image. In addition, each color Y,
M, C, and BL are provided in substantially the same width direction of the PET film 1 as the same color in the width direction.

Printed PET film 1, that is, the material A to be tested
Is a dancer roll 3 or guide roll 4 for absorbing shock
It is supplied to the cutting unit 5 via the above, and is cut here and then supplied to the small winding processing unit 6. The cutting unit 5 cuts the test material A into a length including the above-described stripe pattern of each color, for example, for several tens of pitches, and the small winding processing unit 6 automatically performs a winding process on a ribbon spool (not shown). is there.

Then, in the processing system of the PET film 1 as outlined above, it may be anywhere as long as the material A to be tested travels. For example, in the case of this embodiment, before the cutting portion 5. At, a projector 7 and a photoelectric conversion camera 8 are provided.

The projector 7 is arranged on the side of the PET film 1 to be printed and is composed of, for example, a high-frequency fluorescent lamp. As the photoelectric conversion type camera 8, for example, a line type CCD image sensor of 2592 bits is used as a photoelectric conversion element, and the camera 8 is arranged so as to face the printing surface of the test material A. There is. The camera 8 receives the light projected from the projector 7 and transmitted through the material A to be tested. Camera 8
The CCD image sensor included in the device scans the material A to be scanned in the width direction, and when the single camera 8 cannot cover the entire width of the material A in the field of view, the material A
A plurality of cameras are arranged in a row in the width direction of.

The operations of the projector 7 and the camera 8 are controlled by a control signal from the processing device 9. The processing device 9 is provided with a differentiation processing means 10, a comparison means 11, a threshold level setting means 12, a selection means 13, a selection operation control means 14, a defect determination means 15 and the like.

An image pickup signal from the camera 8 is supplied to the differential processing means 10. This processing means 10 comprises a differential processing circuit,
The image pickup signal is differentiated and output as an image pickup differential signal.

In the case of the present embodiment, the comparison means 11 are each formed of a comparator provided for each color of the material A to be tested. The setting inputs from the threshold level setting means 12 are supplied to the inverting input terminals of each of the comparing means 11, and the imaging differential signals are supplied simultaneously to the non-inverting input terminals of the comparing means 11. Has become.

The setting means 12 is composed of a digital trimmer or the like provided on the operation panel surface of the processing device 9, and the threshold level (threshold value) for binarization is set in advance in each of the comparing means 11 by the operation thereof. In addition, the levels set in the respective comparison means 11 provided exclusively for each color are not the same, and each level corresponds to that color (more precisely, in the case of the present embodiment, the camera 8 Since the transmitted light is received, an appropriate threshold level is set in advance (according to the transmittance of the light, which is different for each color). The threshold level for each of these colors is
Prior to defect detection, using a gauge sheet test material with pseudo defects on good samples for each color, adjust the digital trimmer while operating the detection device to change the threshold level, It is obtained by confirming in advance the level at which a defect can be detected.

The selection means 13 is supplied with the comparison output from the comparison means 11. In the case of the present embodiment, the selection means 13 is formed by a plurality of AND gates to which the comparison outputs of the comparison means 11 are supplied separately. The selection operation control means is provided in each of the selection means 13.
The selection signals output from 14 are separately supplied.

The selection operation control means 14 sequentially switches and outputs a selection signal for selecting one selection means corresponding to the color of the visual field position of the camera 8. That is, in the case of the present embodiment, for example, when the camera 8 scans a portion printed in the color of yellow Y, the selection signal y is output only to the selection unit 13 for the same color Y in accordance with the scanning. When the camera 8 scans the portion printed in the color of magenta M, the selection signal m is output only to the selection means 13 for the same color M accordingly. Similarly, when the camera 8 scans a portion printed in cyan C, the camera 8 outputs the selection signal c only to the selection unit 13 for the same color C, and the camera 8 prints in black BL. When the scanned portion is scanned, the selection means 13 for the same color BL is correspondingly scanned.
The selection signal bl is output only to.

The defect determining means 15 are connected to the output terminals of the selecting means 13, respectively, and the comparison outputs that have passed through the selecting means 13 are individually supplied to these. Each defect determination means 15
Is for determining the width and length of the binarized defect information (comparative output), and determining the defect information equal to or greater than the set value as the defect signal. In this determination, the defect width is determined based on the binarized waveform counted by the clock, and the defect length is determined based on the output time of the defect information described above. It is a thing.

In the case of the present embodiment, the processing system including the above-mentioned means 10 to 15 causes the camera 8 to receive transmitted light.
Since defects are classified into bright defects (pinholes, etc.) and dark defects (black spots, stains, etc.), two systems are actually provided according to the defects, but for the sake of simplicity the first
Only one line is shown in the figure.

An external output device 16 such as a printer is installed outside the processing device 9, and the detection output from the defect detecting means 15 is supplied to the external output device 16. It should be noted that the lamp and the alarm buzzer provided on the operation panel surface are individually informed based on the detection output determined as a defect.

In the above configuration, the photoelectric conversion camera 8 monitors the printing surface of the sheet-shaped test material A that is running, and the photoelectric conversion element of the camera 8 causes the photoelectric conversion element to move the test material A along the width direction. To scan. The image pickup signal from the camera 8 is differentiated by the differential processing means 10.
Is supplied to and is differentiated here. By this processing, a steep change point in the image pickup signal, that is, defect information is found. Then, the imaging differential signals are simultaneously supplied to the dedicated comparing means 11 for each color. Then, in each comparison means 11, the preset threshold level and the imaging differential signal are separately compared, and the signal is binarized. The binarized signal, that is, the comparison output from the comparison means 11 is separately input to the selection means 13. In this input state, the selection operation control means 14
The selection signal from is supplied to one selection means 13. One selection unit to which the selection signal is supplied corresponds to the color of the sheet-shaped test material A monitored by the camera 8, and for example, the camera 8 monitors the yellow print area indicated by Y in FIG. When the comparison output at that time is supplied to the selecting means 13, the selecting means 13 for yellow connected to the comparing means 11 having a threshold level set in advance according to yellow
Only, the selection signal y is synchronously supplied to the other selection means.
No selection signal is supplied to 13. In the supply of such a selection signal, the color monitored by the camera 8 periodically changes as the material A to be inspected travels, and accordingly, the selection operation control means.
14 automatically takes the cycle and switches. Therefore, only the defect information binarized at the appropriate threshold level set individually according to the light transmittance different for each color can be supplied to the next defect determination means 15. Then, the judging means 15 judges the width and length of the defect information and judges the defect.

That is, as described above, the amount of incident light is adjusted by the light projector 7 or the like each time according to a change in color, regardless of visual observation and the sensitivity of the photoelectric conversion element of the camera 8 is constant. There is no trouble, and defect detection is automatically performed at high speed with high reliability. The detection result is supplied to the external output device 16 and the notification device.

Then, in the defect detecting apparatus of the present embodiment, for each color of the test material A, a plurality of comparison means 11 in which the threshold level corresponding to the color is preset is used and simultaneously processed in parallel, By using the selection means 13 for inputting the respective comparison outputs individually, the selection means 13 are sequentially and automatically selected in synchronization with each monitored color, and the comparison output is configured to pass therethrough. The processing speed can be further increased. That is, since the imaging differential signals are compared and binarized at the threshold level determined exclusively for each color, it is necessary to reset the threshold level each time each color reaches the field of view of the camera 8 and is scanned. In addition, since only the comparison output corresponding to the color of the camera visual field position is selected and the determination processing is performed by the defect determination means 15, the defect can be detected at high speed. The selection operation control means 14
Since the required selection of the selection means 13 by means of is like switching by switching, the selection operation is instantaneous, and its negligible time loss is negligibly small.

Moreover, since it is equivalent to resetting the threshold level by selecting the comparison output as described above, the time required to reset the threshold level is not required in the defect detection at the adjacent color boundary part. is there. Therefore, in the defect detection at the color boundary portion, the threshold level is not set, or the defect detection for the color on the rear side in the traveling direction is not performed at the threshold level corresponding to the color on the front side in the traveling direction, and thus the defect There is no over-detection or oversight, and defects can be detected over the entire length in the traveling direction.

Although the above-described one embodiment is configured as described above, in the present invention, the color of the sheet-shaped test material includes the color of the unprinted background. Further, the sheet-shaped test material A may be a non-transparent material, and its thickness does not matter. When the camera receives the reflected light, the reflectance of the light differs depending on the color, so that the threshold level corresponding to the reflectance is set in the comparison means in advance. In addition, when setting the threshold level, you may perform the setting operation individually for each color, but determine the ratio of the reflectance or transmittance of light for each color and set it so that the ratio is interlocked. The operation may be simplified. Further, the comparing means, the selecting means, etc. may be formed by one, respectively, or may be formed by a microcomputer.

In addition, in carrying out the present invention, a concrete structure such as a projector, an opto-electric conversion type camera, a differential processing means, a comparison means, a selection means, a selection operation control means, a defect determination means, etc. It is needless to say that the above can be configured and implemented in various modes without being limited to the above one example.

〔The invention's effect〕

According to the method and apparatus of the present invention having the structure described in the above claims, a plurality of colors having the same color in the width direction and cyclically appearing in the longitudinal direction without visual observation are provided. For a camera that monitors the illuminated area where a certain amount of light is applied to the sheet-shaped test material, despite the fact that the amount of incident light varies for each color, overdetection and oversight of defects caused by this variation can be avoided. It is possible to automatically detect defects such as pinholes, black spots, stains, adhered foreign substances, and streaks contained in each color. In addition, the defect detection speed can be increased and the defect detection can be performed without generating the defect undetectable region for each color.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a defect detection system according to an embodiment of the present invention, and FIG. 2 is a plan view of a part of a sheet-shaped test material. A ... Sheet-shaped test material, 7 ... Projector, 8 ... Photoelectric conversion camera, 10 ... Differentiation processing circuit, 11 ... Comparison means, 12
...... Threshold level setting means, 13 …… Selection means,
14 …… Selection operation control means, 15 …… Defect determination means.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-60-142237 (JP, A) JP-A-61-12345 (JP, A) JP-A-58-81165 (JP, A) JP-A-57- 133342 (JP, A) JP 61-126455 (JP, A) JP 59-154346 (JP, A)

Claims (2)

[Claims] 1. A method for detecting a defect of a sheet-shaped test material having a plurality of colors which are the same color in the width direction and periodically repeated in the longitudinal direction, wherein the sheet-shaped test material is run. Part of the sheet-shaped test material is illuminated with a constant amount of light, and the sheet-shaped test material is illuminated at this illumination position
Scanning is carried out in the width direction by an electric conversion type camera, the image pickup signal from this camera is differentiated, and then provided corresponding to each of the above-mentioned colors, and according to the light transmittance or light reflectance of each of the above-mentioned colors. In a plurality of comparing means having threshold levels individually set in advance, the threshold level and the imaging differential signal for each color are compared and binarized, and the binarized comparison output is corresponded to each color. A defect detection method for a sheet-shaped material to be inspected, characterized in that the defect detection is performed by the defect determination means provided to detect a defect for a color in the visual field position of the camera. 2. A light projector for illuminating a part of a running sheet-shaped test material with a constant light amount, which has a plurality of colors which are the same color in the width direction and which appear repeatedly in the longitudinal direction periodically. A photoelectric conversion camera that scans the sheet-shaped test material in the illumination position of the projector along its width direction, a differential processing unit to which an image pickup signal from the camera is supplied, and a plurality of colors corresponding to each of the plurality of colors. And the imaging differential signals obtained by the differential processing means are separately supplied,
A threshold level corresponding to the light transmittance or the light reflectance of each color is preset for each color, and a plurality of comparisons are performed in which the supplied imaging differential signal is compared with the threshold level and binarized. Means and a plurality of selection means provided corresponding to each of the plurality of colors and supplied with the comparison outputs of the respective comparison means, respectively, and one of the selection means corresponding to the color of the visual field position of the camera. Selection operation control means for selecting one of the selection means, and a plurality of defect determination means provided corresponding to each of the plurality of colors and separately supplied with the comparison outputs passed through the selection means. Defect detection device for sheet-shaped test material.