JPH0430529Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) This invention relates to a printing defect detection device for printed matter continuously printed on roll paper.

(Technical background of the invention and its problems) In general, printing defects such as ink scattering and doctor streaks that appear in spots during high-speed continuous printing, and defects such as dust adhesion cannot be detected. difficult. For this reason, methods have been adopted, such as stopping the machine at the beginning or end of winding and visually inspecting only a small part of the machine, or lighting a strobe in synchronization with the feed speed of the roll paper to conduct a visual inspection. There is. However, problems often occurred because defective products sometimes got mixed in due to not being fully inspected or oversight by inspectors. For this reason, there is a demand for the development of a high-speed defect detection system that can be used during operation. It is becoming more and more common.

6A to 6C show a color sensor element used for detecting printing defects in the above-mentioned printed matter. A color filter 11 is placed over an amorphous optical sensor (glass substrate) 10, and visible light is transmitted to red, green, blue ( (hereinafter abbreviated as R, G, and B), so that individual light outputs can be obtained from each. Note that a transparent cover glass 1 is placed on top of the color filter 11.
2 is installed. Figure 6A shows an element of 1 RGB unit, which is provided with a common terminal CT and RGB output terminals RT to BT, Figure 6B shows its cross section, and Figure C shows an element of 1 RGB unit. The detection unit 1 is composed of n pieces arranged in a horizontal row.

FIG. 7A shows the relationship between the printed matter and the detection unit, in which 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. 7B shows that the same pattern is printed continuously on the sheet 2 and is outputted 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 proper spacing, and the two detection unit boxes 3A and 3B are placed at positions shifted by one pitch or several pitches. Therefore,
These two detection unit boxes 3A and 3B
The color sensor elements inside are placed directly above the parts with the same picture. That is, in FIG. 7B, 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. 5, 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,
The signals are input to the differential amplifier 7 as GA, BA, RB, GB, and BB. Here, color sensor element 5A
and 5B are located on the same pattern, so if the pattern is normal, their outputs are all equal and are differential amplifier 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 a permissible range, and in Figure 5, the upper limit is RCmax,
GCmax and BCmax, the lower limits are set as RCmin, GCmin and BCmin, and are input to the comparator 8 together with the output of the differential amplifier 7. If ink is scattered on one of the patterns and this is detected by, for example, color sensor element 5B, then naturally 5A and 5B
If the output voltage of the ink becomes different and the degree of ink scattering exceeds the set tolerance range, the output of the comparator 8 becomes "NO" and, for example, it outputs a "1" signal to indicate an error. become. 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 there is an error is made for all color sensor elements. That is, the sixth
The n output voltages shown in FIG. C are input to each of the n control circuits shown in FIG. 5, and it is determined whether or not there is an error. FIG. 4 shows the criteria for determining whether a product is good or an error based on the output of the comparator 8, and is an example in which the RGB tolerance values are set to RC, GC, and BC. The control box 4 in FIG. 7A also controls the amplifier 6 and the differential amplifier 7.
and n control circuits including a comparator 8.

However, in this case, even though the output signals from the color sensor elements 5A and 5B are properly gain-adjusted by the amplifier 6 for each color in the initial state, the gain deteriorates due to temperature drift and aging of the operational amplifier of the amplifier. There are things to do,
If both of the color sensor elements 5A and 5B deteriorate to the same extent at the same time, the function will be satisfied, but in the detection method of subtracting the difference between the output voltages of both using the differential amplifier 7, errors may occur due to such gain deterioration. However, there is a problem in that printing defects cannot be detected accurately. Therefore, in order to prevent this gain deterioration, it is possible to use a load-lift and low-offset operational amplifier or an automatic gain adjustment circuit, but both are expensive and, if used for all color sensor elements, at least
There is a problem in that more than 1000 pieces are required, leading to an increase in costs.

Therefore, in order to solve the above problem, as shown in FIG.
Insert CG and CB to cut out the DC components of the above differential amplifier outputs (RA-RB), (GA-GB), and (BA-BB), and extract only the AC components, that is, the amount of change. For example, malfunctions due to gain deterioration as described above can be prevented at low cost.

However, in this case, although it is good at the time of measurement, in the initial state when this printing defect detection device is initialized,
Gain adjustment is not possible unless the pattern detected by the two color sensor elements is changed and the amount of change detected. Therefore, as shown in Figure 3, each capacitor
Switches SR, SG and
A setting/detection switching circuit 9 with an SB inserted is provided, and in the initial state, these switches SR, SG and
Turn on SB to adjust the gain, and after adjustment, open this switch SR, SG, and SB, and connect the above capacitor.
By detecting the amount of change through CR, CG, and CB, a printing defect detection device with stable performance that is not affected by aging can be obtained.

However, when used for all color sensor elements as described above, the number of switches SR, SG, and SB in the setting/detection switching circuit 9 becomes enormous, and these switches SR, SG, and SB are required each time the initial state is adjusted.
There is a problem in that operating the SG and SB places a great burden on the worker.

(Purpose of the invention) This invention was made from the above-mentioned circumstances, and is intended to have stable printing defect detection characteristics without being affected by temperature drift or aging of the amplifier in the printing defect detection device described above. Another object of the present invention is to provide a printing defect detection device in which the initial state can be easily set.

(Summary of the invention) This invention consists of a plurality of light-receiving surfaces of sensor elements that receive visible light and generate a corresponding output voltage arranged horizontally in one row, and are arranged one pitch to several pitches in the flow direction of a printed sheet. Two detection units arranged so as to correspond to each other with respect to the flow direction, and a difference between the reflected light from the printed matter and the difference voltage of the corresponding sensor element between the two detection units is calculated. In the printing defect detection device comprising a dynamic amplifier and a comparator that detects a defect in the printed matter by comparing the differential voltage with a preset voltage, the differential amplifier is connected to the comparator. The photocoupler includes a pair of capacitors and a photocoupler connected in parallel to each other, and one switch means for simultaneously switching the operations of the plurality of photocouplers.

(Embodiment of the invention) FIG. 1 is a wiring diagram showing an example of a printing defect detection circuit used in this invention, in which the color sensor elements 5A and 5B, the amplifier circuit 6, and the differential amplifier 7 are connected to each other. , the comparator 8, and a setting/detection switching circuit 90 inserted between the differential amplifier and the comparator 8. This setting/detection switching circuit 90, as shown in FIG. Photocouplers 91A, 91B, and 91C make the switching circuit 90 conductive during initial setting, and connect the capacitors CR, CG, and CB during detection, and a direct current switch simultaneously switches and activates the photocouplers 91A, 91B, and 91C. It consists of a power supply B, a switch SW, and a circuit resistance R. Here, the fluorocouplers 91A, 91B and 91C
As is well known, the light emitting diodes DR, DG and DB and the phototransistors TR, TG and TB
When the light-emitting diodes DR, DG, and DB are energized, the phototransistors TR, TG, and TB become conductive, and when the energization is removed, the conductive state is canceled and the phototransistors become non-conductive. It has a switching function so that Therefore, first, the switch SW is made conductive, and the photo couplers 91A, 91B and 9
The setting/detection switching circuits for each color of R, G, and B are made conductive at the same time via 1C, and the initial setting (gain adjustment) of each of the R, G, and B detection circuits is performed as described above, and then the switch SW is turned on. If the conductive state is canceled by opening , and the capacitors CR, CG, and CB are connected to the R, G, and B color detection circuits, printing defect detection can be executed from now on.

Here, all of the plurality of photocouplers used in the printing defect detection device are connected in parallel as described above (not shown),
All the photo couplers can be simultaneously switched by simply operating a set of DC power supplies and switches connected to operate the plurality of photo couplers, and the initial setting state and operating state of this printing defect detection device can be changed. become.

(Effects of the invention) As described above, by using the printing defect detection device of this invention, the initial state can be set with a simple operation of switching one switch, and after adjusting the gain and setting the initial state, By simply switching the above-mentioned switch, printing defects in continuous printing can be detected accurately and inexpensively with stable characteristics without being affected by temperature drift or aging of the amplifier.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the detection circuit of the printing defect detection device of this invention, Fig. 2 is a diagram showing the setting/detection switching circuit of the detection circuit, and Figs. 3 and 5 are the outputs from the detection unit. A wiring diagram showing an example of a circuit that controls signals to detect whether or not an error has been detected, FIG. 4 is a diagram for explaining the judgment criteria,
6A to 6C are structural diagrams of the color sensor element;
Figures A and B are diagrams showing the relationship between the printed matter and the detection unit. 1...Detection unit, 2...Seat, 3...Detection unit box, 4...Control box, 5...
...Color sensor element.

Claims (1)

[Scope of utility model registration request] A plurality of light-receiving surfaces of sensor elements that receive visible light and generate a corresponding output voltage are arranged in a horizontal row, and are shifted by one pitch to several pitches in the flow direction of the sheet of printed material so that they coincide with each other in the flow direction. two detection units arranged so as to correspond to each other; a differential amplifier that calculates the difference voltage between the sensor elements corresponding to the two detection units based on the reflected light from the printed matter; A printing defect detection device comprising a comparator that detects a defect in the printed matter by comparing it with a set voltage, wherein a pair of differential amplifiers and a pair of comparators are connected in parallel between each of the differential amplifiers and each of the comparators. A printing defect detection device comprising a capacitor, a photocoupler, and one switch means for simultaneously switching the operations of the plurality of photocouplers.