JPH0560041B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) This invention aims to prevent defects such as ink scattering, doctor streaks, and dust adhesion during printing on packaging materials such as paper, aluminum, and plastic. The present invention relates to a printed matter defect detection device that detects defects at high speed.

(Technical background of the invention and its problems) Generally, it is difficult to detect defects that appear in spots during high-speed printing. For this reason, the machine must be stopped at the beginning or end of winding.
Only a limited number of visual inspections have been performed. However, because they were not 100% inspected, problems often occurred because defective products could get mixed in inside. For this reason, there has been a need for a high-speed defect detection system that can be used during operation. Before explaining the present invention, the following method has been realized and will be explained. In other words, two sets of detection units each consisting of a plurality of light-receiving surfaces of color sensor elements that receive visible light and separate it into red, green, and blue and generate the corresponding output voltages are arranged in a horizontal row. one of the detection units is arranged in the width direction perpendicular to the flow direction of the sheet before the printed matter is rolled up, and the other of the detection units is shifted by one pitch to several pitches in the flow direction of the sheet,
The color sensor elements are arranged so as to correspond to each other in the sheet flow direction, and the reflected light from the printed matter is received by two sets of detection units, and the red and green of the corresponding color sensor elements between the two sets of detection units are detected. , a difference voltage for blue is calculated, and this difference voltage is compared with a preset voltage to detect defects in printed matter. That is, FIGS. 1A to 1C show color sensor elements used in this device, in which a color filter 11 is placed over an amorphous optical sensor (glass substrate) 10, and visible light is divided into red, green, and blue (hereinafter referred to as R).
(abbreviated as "G" and "B"), so that individual light outputs can be obtained from each. Note that a transparent cover glass 12 is attached on top of the color filter 11. Figure 1A shows an element in RGB1 unit, with common terminal CT and RGB output terminal RT~
BT is provided, and Figure B shows its cross section, and Figure C shows n elements of RGB 1 unit arranged in a horizontal row.
It consists of

Figure 2A shows the relationship between the printed matter and the detection unit.The sheet 2 of the printed matter before being rolled up and the detection unit 1 are placed in a box, and the light-receiving surface is placed on the sheet 2.
Detection unit boxes 3A and 3 facing
B, and a control box 4 having a function of receiving and controlling detection signals from the detection unit boxes 3A and 3B. FIG. 2B shows that the same pattern is printed continuously on the sheet 2, and is outputted flowing in the direction indicated by the arrow. That is, 2A and 2B are printed with the same pattern. This sheet 2
In contrast, the detection unit boxes 3A and 3B are arranged with appropriate spacing, and the two detection unit boxes 3A and 3B are placed at positions shifted by one pitch. Therefore, the color sensor elements in these two detection unit boxes 3A and 3B are placed directly above the same pattern. That is, Figure 2B
In this case, color sensor elements 5A and 5B correspond to each other and are located directly above the same patterns 2A and 2B.

Under such an arrangement, the printed matter, ie, the sheet 2, is irradiated with light using a light source containing visible light, and the reflected light is detected by a color sensor element. To explain this situation with reference to FIG. 3A, the output signals from the color sensor elements 5A and 5B are appropriately gain-adjusted by the amplifier 6 for each color, and their output voltages are
The signals are input to the subtracter 7 as RA, GA, BA, RB, GB and BB. Here, the color sensor element 5
Since A and 5B are located on the same pattern, if the pattern is normal, their outputs are all equal and are the subtractor outputs (RA-RB), (GA-GB) and (BA-BB). should all be zero. However, it is physically impossible for them to be exactly equal, so the amount is set in advance within an allowable range, and in Figure 3A, the upper limit is RCmax,
In addition to setting GCmax and BCmax, the lower limit is RCmin,
GCmin and BCmin are input to the comparator 8 along with the output of the subtracter 7. If ink is scattered on one of the patterns and this is detected by the color sensor element 5B, of course 5A and 5B will detect this.
If the output voltage of B becomes different and the degree of ink scattering exceeds the set tolerance range, the output of comparator 8 becomes "NO",
For example, it will output a "1" signal to indicate an error. If it is within the range of the upper and lower limits, it will be a "GO" of a good product and a "0" signal will be output. Similarly, determination of whether or not these errors occur is made for all color sensor elements. That is, the first
The n output voltages shown in FIG. 3C are input to each of the n control circuits shown in FIG. 3A, and a determination is made as to whether or not there is an error. Figure 3B shows the criteria for determining whether the product is good or an error based on the output of the comparator 8, and the allowable values of RGB are RC,
This is an example set to GC and BC. Also, Figure 2A
The control box 4 controls these amplifiers 6 and subtracters 7.
It is composed of n control circuits including a comparator 8 and a comparator 8.

The two detection unit boxes mentioned above are 1
Although I placed it in a position shifted by a pitch, the same result can be obtained even if it is placed in a position shifted by several pitches.

As described above, according to this detection device, if a printed matter that is running at high speed has some kind of defect,
Since it can be detected immediately, it becomes possible to inspect all printed matter.

However, in the above-described defect detection device for printed matter, it is difficult to achieve dimensional accuracy because the size of the color sensor elements varies, and two corresponding color sensor elements of two sets of units do not necessarily match the exact pattern of the image. Not only will they not receive reflected light from the same area, but if the size is the same as a color sensor element, the element itself may detect its own shadow on the printed matter due to the light from the light source. This has the disadvantage that errors tend to occur when detecting reflected light.

(Objective of the Invention) The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a highly accurate printed matter defect detection device by reducing errors during detection.

(Summary of the invention) This invention detects two sets of light-receiving surfaces of color sensor elements that receive visible light, separate it into red, green, and blue, and generate the corresponding output voltages. unit and one of the detection units is arranged in the width direction perpendicular to the flow direction of the sheet before the printed material is rolled up, and the other detection unit is shifted by one pitch to several pitches in the flow direction of the sheet, so that the color sensor element is The reflected light from the printed matter is received by two sets of detection units, and the red, green,
Regarding a printed matter defect detection device that detects defects in printed matter by calculating the differential voltage for blue and comparing the differential voltage with a preset voltage, the device uses a plurality of optical fibers for visible light in a horizontal row. By using a light guide arranged in rows, the color sensor element receives reflected light from the printed matter.

(Embodiment of the invention) FIG. 4 is an overall view showing an embodiment of the invention. In order to receive light directly from the printed matter, the detection unit box 3 as described above is not installed on the printing surface, and the flow direction image sensor 2
2. A detection unit box 31 equipped with a widthwise image sensor 23 and a light source 24 and installed in a remote location with sufficient space via an optical fiber 9;
Light guide unit 21 designed to guide light to
Use two sets of. This light guide unit 21
In this case, one unit 21A is arranged in the width direction perpendicular to the flow direction of the sheet 2 before the printed matter is rolled up, and the other unit 21B is shifted by one pitch to several pitches in the flow direction of the sheet 2, so that each light guide unit Arranged in a coincident and corresponding manner with respect to the sheet flow direction. In this case, one light guide unit 21A is fixed and the other light guide unit 21A is fixed.
B is movable in position using a drive mechanism 25. Under such an arrangement, the printed sheet 2 is irradiated with light using a light source 24 containing visible light, and the reflected light is taken into the color sensor element 5 via the optical fiber 9 used as a light guide. .

FIG. 5 is a sectional view of the light guide unit 21, and FIGS. 6A and C are two types of optical fibers 9.
Figures B and D are diagrams showing an example of the arrangement. As shown in the figure, the light guide has a plurality of optical fibers 9 for visible light arranged horizontally with high precision, and after fixing, the surfaces are polished. The optical fiber 9 is formed by arranging R, G, and B in three rows as shown in FIGS. As shown in C and D, three RGB lines can be arranged in two rows with the directions alternately reversed to form a triangular system. In this case, the optical fiber 9 will be bent, so the optical fiber 9 is straightened out using a shaft 26 with a pole or resin at the center of RGB to cast a shadow on the sheet 2, as shown in FIG. Make sure not to create or obstruct the flow of sheet 2. Further, the optical fibers 9 are guided to the optical sensor 10 as shown in FIG. 8, and each optical fiber is made to correspond one-to-one to a sensor element.

(Effects of the Invention) As described above, according to the present invention, by arranging optical fibers as a light guide with precision,
Since the positional accuracy is improved and the width of the unit is reduced, there is no need to detect its own shadow formed on the sheet, and there is an advantage that printed matter can be detected reliably.

[Brief explanation of drawings]

1A to 1C are structural diagrams of the color sensor element used in this invention, 2A and 2B are diagrams showing the relationship between the printed matter and the detection unit, and 3A is a diagram showing the error by controlling the output signal from the detection unit. A wiring diagram showing an example of a circuit for detecting whether or not a D is a diagram showing an example of the arrangement of optical fibers in the light guide unit, FIG. 7 is a diagram showing how the optical fibers are fixed using a shaft, and FIG. 8 is a diagram showing how the color sensor and the optical fibers are connected. be. 1...Detection unit, 2...Seat, 3...Detection unit box, 4...Control box, 5...
...Color sensor element, 6...Amplifier, 7...Subtractor, 8...Comparator, 9...Optical fiber, 1
0... Amorphous optical sensor, 11... Color filter, 12... Cover glass, 21... Light guide unit, 22... Flow direction image sensor, 23... Width direction image sensor, 24... Light source, 25... Drive mechanism, 26...axis.

Claims (1)

[Claims] 1 It has a light guide in which multiple optical fibers for visible light are lined up, and it receives visible light from printed matter and produces red,
two sets of detection units that guide light through the light guide to the light receiving surface of a color sensor element that separates the colors into green and blue and generates the corresponding output power; and a sheet of the printed material before being rolled up. One end of the light guide and the sheet are arranged at an appropriate distance in a direction perpendicular to the flow direction of the sheet, and one end of the other light guide is shifted by one pitch to several pitches in the flow direction of the sheet. , the light guides are arranged to correspond to each other with respect to the flow direction, the light from the printed matter is received by the light receiving surface of the color sensor element via the light guide, and the light is transmitted between the two detection units. A defect in the printed matter is detected by calculating the differential voltage for red, green, and blue of each of the corresponding color sensor elements, and comparing the differential voltage with a preset voltage. Features: Print defect detection device.