JPS60220809A - How to detect defects in printed matter - Google Patents

Abstract

PURPOSE:To detect a defect and stuck dust during printing operation at a high speed and to perform all-number inspection of printed matter by calculating difference voltages among color sensor elements as to red, green, and blue and comparing said difference voltages with a set value. CONSTITUTION:Photodetection surfaces of color sensor elements 5A and 5B use two detection units composed of one lateral array. Output signals of the color sensor elements 5A and 5B are gain-adjusted properly by an amplifier 6 for every color and output voltages are inputted to a subtracter 7. Then, the set value is inputted to a comparator 8 together with outputs of the subtracter 7. Then, the difference voltages are calculated and compared with the set value. Namely, it is judged from the output of the comparator 8 whether printed matter is conforming matter or not, thus detecting the sticking of defective dust during the printing operation. Thus, the all-number inspection of the printed matter is performed.

Description

[Detailed Description of the Invention] This invention is capable of high-speed detection of defects such as ink scattering, doctor streaks, and dirt accumulation during printing on packaging materials such as paper, aluminum, and plastic. Regarding the method.

In general, it is difficult to detect defects that appear in spots during high-speed printing, so the machine is stopped at the beginning or end of winding and visual inspection of only a small portion is 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 demand for the development of a high-speed defect detection system that can be used during operation. Therefore, an object of the present invention is to provide a defect detection method that can be used during high-speed operation.

This invention will be explained below.

This invention uses two sets of detection units each consisting of a plurality 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 in 4111 rows. It is something. One side of the same unit/ ) is placed in the width direction perpendicular to the sheet flow direction before the printed matter is rolled up, and the other of the detection unit I is shifted by one pitch or several pitches in the sheet flow direction, so that the color sensor element detects the sheet. arranged so as to correspond to each other with respect to the flow direction,
The reflected light from the printed matter is received by two sets of detection units, and the difference voltage for red, green, and blue of the corresponding color sensor element between the two sets of detection units is calculated, and this difference voltage is set in advance. Defects in printed matter are detected by comparing the voltage with a set voltage.

Figures 1 (A) to (C) show a color sensor element used in the present invention, in which a color filter 11 is placed over an amorphous optical sensor (glass substrate) lo, and visible light is transmitted to red, a, blue ( (Hereinafter abbreviated as R, G, 13)), and individual light outputs can be obtained from each. In addition,
Color filter! A transparent cover glass 12 is attached on top of the . Figure 1 (A) shows an element in RGB 1 unit, with a common terminal GT and an RGB output terminal RT.
-BT is provided, and the figure (B) shows its cross section, and the figure (C) shows n elements of RGB l unit arranged in a horizontal row, and this makes the detection unit l. It consists of

Figure 2 (A) shows the relationship between the printed matter and the detection unit, and shows the relationship between the sheet 2 of the printed matter before being rolled up and the above-mentioned detection unit).
Detection unit boxes 3A and 3B have a light receiving surface facing the sheet 2, and a control box 4 has a function of receiving and controlling detection signals from the detection unit boxes 3A and 3B. And, Figure 2 (B
) indicates 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.

For this sheet 2, the detection unit boxes 3A and 3
The detection unit boxes 3A and 3B are placed at appropriate intervals, and the two detection unit boxes 3A and 3 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, in FIG. 2(B), the color sensor elements 5A and 5B correspond to each other, and are positioned 1ξ directly above the rotating patterns 2A and 2B.

Under such an arrangement, the printed matter, ie, the sheet 2, is irradiated with light using a light source containing orthoscopic light, and the reflected light is detected by a color sensor element. To explain this situation with reference to FIG. 3(A), 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 RA, GA, BA, RB, CB and B
B and is manually input to the subtractor 7. Here, since the color sensor elements 5A and 5B are located on the same pattern,
If the picture is i1E, all its outputs are equal, and the subtractor outputs (RA-RB), (OA-GB), and (BA-BB) should all be zero. However, it is physically impossible for them to be exactly equal, so
The amount within the permissible range is set in advance, and in Fig. 3 (A), the upper limit of this set value is set as RG & lX * ccw and B.
C-, and the lower limits are RCHL, GCHI and BC,m
The output signal is then 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 color sensor element 5B, of course the output voltages of 5A and 5B will be different, and the degree of this ink scattering will be within the set tolerance range. If it exceeds 1, the output of the comparator 8 will be ``NO'', and for example, it will output a ``1'' signal to indicate an error.1
- If it is within the range of the lower limit and the lower limit, the product is “GO” and “
The θ′′ signal will be output. Similarly, determination of whether or not there is an error is made for all color sensor elements. That is, the n output voltages shown in FIG. 1(C) are respectively input to the n control circuits shown in FIG. 3(A), and it is determined whether there is an error or not. Figure 3 (B
) indicates the criteria for determining whether it is a good product or an error based on the output of the comparator 8, and the allowable values of RGB are Re,
This is an example where it is set to GC and BG. Also, Figure 2 (A)
The control box 4 of these amplifiers 6. It is composed of n control circuits including a subtracter 7 and a comparator 8. .

Although the two detection unit boxes described above were placed at positions shifted by one pitch, similar results can be obtained even if they are placed at positions shifted by several pitches.

As described below, according to the detection method of the present invention, if any defect occurs in a printed matter that is being operated at high speed, it can be detected immediately, which has the advantage of making it possible to inspect all printed matter. There is.

[Brief explanation of the drawing]

Figures 1 (^) to (C) are structural diagrams of the color sensor element used in this invention, tJS2 Figures (A) and (B) are diagrams showing the relationship between the printed matter and the detection unit, and Figure 3 (A) is a diagram showing the relationship between the printed matter and the detection unit. A wiring diagram showing an example of a circuit that controls an output signal from a detection unit to detect whether or not an error has been detected. FIG. ■...detection unit, 2...sheet, 3...detection unit box, 4...control box, 5...color sensor element. Application agent Yuzo Yasugata

Claims (1)

[Scope of Claims] Two elements each consisting of a plurality of light-receiving surfaces of color SE/S elements arranged in a horizontal row, each of which receives visual light, decomposes it into red, green, and blue, and generates the corresponding output voltages. 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, The color sensor elements are arranged so as to correspond to each other with respect to the flow direction, the reflected light from the printed matter is received by the two detection units, and the color sensor elements corresponding to each other between the two detection units are arranged so as to correspond to each other in the flow direction. Motoko's red. A method for detecting defects in printed matter, characterized in that defects in the printed matter are detected by calculating a differential voltage between green and blue, and comparing the differential voltage with a preset voltage.