JPS6027064B2 - Label front and back inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a label inspection method in which a label is inspected with the label upside down, that is, with the front side reversed, in an appearance inspection that inspects the state of attachment of a label attached to a product. It is related to the device.

Such labels do not necessarily have a large difference in reflectance between the front and the back, and many have fine patterns such as letters on the front, but not on the back. Reversing the front and back sides is a serious defect among label attachment defects, and therefore, it is required to stably and reliably inspect even items where there is not much difference in reflectance between the front and back sides. Conventionally, reverse label inspection has been performed by using a reflective photoelectric sensor to detect the large difference in reflectance between the front and back sides of the label as a difference in the amount of light reflected from the label.

Even if there is not much difference in overall reflectance between the front and the back, if there is a relatively large mark on the front and the reflectance there is significantly different from the back, attach a photoelectric sensor to the mark. I have tested the same. However, with these methods, it is difficult to inspect items where there is not much difference in reflectance between the front and back sides and there are no large marks. Furthermore, if a part of the mark is to be focused on, a photoelectric sensor must be attached to the mark at the optimum position, and the positioning of the sensor has a subtle effect on the inspection. Furthermore, it has the disadvantage that it is greatly affected by the positional shift of the label itself. This invention is capable of stably detecting whether the front and back sides are reversed without being affected by misalignment of the label itself, for labels where there is not much difference in reflectance between the front and back sides, and which only have small patterns such as letters on the front surface. The purpose of this invention is to provide a highly efficient inspection device.

A feature of the present invention is a label front and back inspection device that determines the front and back sides of a label by processing one screen worth of image signals obtained by photographing a label to be inspected, the apparatus comprising: one horizontal scanning of the image signal; binarization means for binarizing the signal obtained by the above at a first set level for detecting the presence or absence of a label and a second set level for detecting a pattern inside the label; and pattern detection means for detecting whether or not a predetermined pattern exists in the label based on each output from the two 200 million conversion means,
The main feature is that the front and back sides of a label can be determined based on the number of output signals for one screen of the detection means.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the invention.

In the figure, 1 is a television camera, 2 and 3 are binarization circuits, and 4 is a pattern detection circuit. 2 and 3 are binarized at two different levels, and these two binarized signals are compared in a pattern detection circuit 4 to detect whether or not a predetermined pattern or pattern exists within the label. , distinguish between front and back.

FIG. 2 is an explanatory diagram showing an example of a label to be inspected, and FIG. 3 shows a signal waveform per horizontal scanning line of a signal obtained by photographing the label, and a binarization circuit 2, FIG. 3 is a waveform diagram showing the signal waveform when binarized at 3, where A shows the case where the surface of the label is photographed, and B shows the case where the surface of the label is photographed.

In FIG. 2, L is the label, S indicates the scan line (raster) position, and P represents the pattern within the label L. In FIG.

If you photograph a label with this kind of pattern with a TV camera,
The video waveform at the scanning line position S is a waveform that changes according to the pattern, as shown by V in FIG. 3A.

When this video waveform V is binarized at set levels LL and HL, signal waveforms as shown by DL and DH in FIG. 2A are obtained. Here, the setting levels LL and HL are selected to be low level and high level, respectively, so that the background and pattern of the label can be extracted stably, for example. Therefore, a single pulse DL corresponding to the background of the label appears from the binarization circuit 2, and a plurality of pulse signals DH appear from the binarization circuit 3 according to the pattern inside the label. On the other hand, if the label is pasted with the front side and diamonds reversed, there is no pattern within the label, so the video waveform V and the binarized signal waveform DH as shown in Figure 3B. becomes flat and is output as a single pulse signal.

FIG. 4 is a schematic diagram showing the detailed configuration of the pattern detection circuit, and FIG. 5 is a waveform diagram showing the signal waveforms of each part in FIG.
In case the label is pasted in the correct position, in case B, the label is pasted upside down, and in case C, the label pasted position is slightly shifted from the normal position.

In FIG. 4, 41 and 42 are JK flip-flops,
43 is a counter, the clock terminal CK of the JK flip-flop 41 is given the output signal DH of the binarization circuit 3 shown in FIG. 1, and the output signal DL of the binarization circuit 2 is also given to the clear terminal CR. It is given.

Therefore, if the labels are correctly pasted at the proper positions, the binary signals will have waveforms as shown by DL and DH in FIG. 5A, and the outputs of the JK flip-flops 41 and 42 will be Q, Q2 Thus, one pulse signal Q2 appears at the output of the flip-flop 42.

On the other hand, if the front and back of the label are reversed, the binary signal will have a waveform as shown by DL and DH in Figure B,
Flip-flop 41 outputs Q. is obtained, but the output Q2 of the flip-flop 42 is not obtained. Therefore, the flip-flop 4 appearing as Q2
If the number of pulses from 2 is counted by the counter 43 in an area that includes the entire label, when it is normal, it will be the number of scanning lines (raster) that cross the pattern in the label, and when the front and back are reversed, it will be the number of scanning lines (raster) that cross the pattern inside the label. Since there is no, the count value is 0
'Konaru.

By comparing this count value with a certain set value and determining whether it is greater than or less than the set value, it is possible to determine whether the label is front or back. In other words, at one level LL, a binary signal DL according to the background of the label is output, and that signal is a logic "
During the period of 1'', the presence or absence of a pattern is checked depending on whether the number of pulses of the binary signal DH due to the pattern of the label is 2 or more, and an inside-out inspection is performed.

The waveform shown in Figure 5C is the case where the label is shifted to the right by a predetermined distance △, and is exactly the same as the waveform shown in Figure 5A, except for the overall shift to the right. be.

Furthermore, even if the label attachment position shifts upward or downward, in the case of this invention, the label is in a two-dimensional area, so as long as there is a label within the area, the DL will be applied where the label exists.
Since the DH signal appears, it is possible to inspect the front and back sides.

The same applies to rotation. In short, it is possible to inspect the front and back sides of the label irrespective of the positional deviation of the label. Furthermore, as can be easily seen from the timing chart of FIG. 5, in order for the pulse signal Q2 to appear at the output of the flip-flop 42, during the period of logic "1" of the binary signal DL,
It is sufficient that the binary signal DH has two or more pulses, and is not related to the number of pulses or the width of the pulses, that is, the number or size of patterns within the label.

The sixth is a waveform diagram showing a case where a bright portion such as that indicated by N near the label exists as noise due to disturbance light.

The figure shows that in the noise N portion, the output Q2 of the flip-flop 42 remains at logic "0", and only in the portion with the label L there is a pulse output Q2. For this reason,
It cannot be affected by noise that exists outside the label. Note that even if there is dirt on the back side of the label, the output pulses of the flip-flop 42 are counted and inspected for the two-dimensional area including the label, so if the counted value during normal operation is sufficiently large, the set constant can be used as a reference for comparison. By setting a large value, it is possible to ignore counts due to some degree of dirt. As described above, this invention focuses not only on the difference in reflectance (difference between brightness and darkness) between the front and back sides of a label, but also on the pattern inside the label. It is possible to stably inspect the front and back sides.

Furthermore, since the correspondence between the binarized data at two levels is checked in a two-dimensional area that includes the label, that is, where the label exists, it is not affected by the positional shift of the label or the state of the pattern within the label. Therefore, it can be applied to various label inspections. Furthermore, even if there is noise due to ambient light, it will not be affected much because the relative relationship between two signals in the same area is checked. In addition, since this invention examines the presence or absence of a pattern within a label, in addition to inspecting the front and back sides of a label, it is also possible to inspect whether a pattern within a label has come off.

Further, defects such as scratches and dirt can be detected by considering scratches and dirt on the surface of an object having uniform brightness in the same way as a pattern.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of a label, and FIG. 3 shows the signal waveform of a label imaging signal during one horizontal scanning period and the corresponding FIG. 4 is a circuit diagram showing the pattern detection circuit of FIG. 1, and FIG. 5 is a waveform diagram showing signal waveforms of each part of FIG. 4. 6 is a waveform diagram showing the case where noise is included. Explanation of symbols 1... Television camera, 2, 3... Binarization circuit, 4... Pattern detection circuit, 41, 42... JK flip-flop, 43... Counter, L... Label, S...
Scanning line (raster), P...pattern, V...
・Video signal, DL, DH...Binarized signal, LL, H
L...Setting level. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. A label front and back inspection device that determines the front and back sides of a label by processing one screen worth of imaging signals obtained by photographing a label to be inspected, the apparatus comprising: Binarization means that binarizes the obtained signal at a first setting level for detecting the presence or absence of a label and a second setting level for detecting a pattern within the label;
pattern detection means for detecting whether or not a predetermined pattern exists in the label based on each output from the two binarization means for each horizontal scan; 1. A front-back inspection device for a label, characterized in that the front and back sides of a label are determined based on the number of output signals from a pattern detection means.