JPH0545127B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) This invention uses optical fibers to illuminate and measure the printing surface, and prevents ink from scattering when printing on packaging materials such as paper, aluminum, and plastic. The present invention relates to a sensor head for detecting print defects, which detects defects such as doctor streaks and adhesion of dust by color photometry.

(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 is stopped at the beginning and end of winding, and only a small portion of the winding is visually inspected. However, since it was not possible to inspect all the products, problems often occurred as defective products could get mixed in inside. Therefore, high-speed defect detection systems that can be used during operation have recently emerged.

Figures 6A and 6B show an example of such a printing defect detection device, which receives visible light, separates it into red (R), green (G), and blue (B), and outputs the corresponding output. Color sensor element 60 that generates voltage
Two sets of sensor heads 6A and 6B each having a plurality of light-receiving surfaces A and 60B arranged horizontally in one row are used. One side of the same head 6A, 6B is pattern 9A, 9
A printed matter 9 on which B... is continuously printed is placed in the width direction perpendicular to the flow direction of the sheet before being rolled up, and the other detection unit is placed in the direction of flow of the sheet one pitch or a number of printing pitches of the above-mentioned pattern. The color sensor elements 60A and 60B are arranged so that they correspond to each other in the sheet flow direction, and the reflected light from the printed matter is received by two sets of sensor heads 6A and 6B, and the two sets of sensor heads are matched. The controller 8 calculates the differential voltage for red (R), green (G), and blue (B) of the color sensor element, and compares this differential voltage with a preset voltage to detect defects in printed matter. It is designed to detect.

When detecting printing defects by converting the content of printed matter into electrical signals, in principle, a photo sensor such as an amorphous optical sensor is used as the color sensor element of this sensor head, facing the printed matter. The shading of the surface can be converted into electrical signals, making it possible to detect printing defects. In practice, when reading printed matter with high resolution, it is not only structurally impossible to install many photo sensors near the printed material, but also because the resolution is limited by the external dimensions of the photo sensors. Recently, the sensor head uses an optical fiber such as a glass fiber to transfer the amount of light detected from the printed matter to a distant location, and then connects a photo sensor to the end of the optical fiber at that remote location. The method described above has been implemented. In this case, a common method is to place the light-receiving optical fiber of the sensor head facing the printing surface and guide the reflected light obtained by shining light from a light source onto the printing surface through the light-receiving optical fiber. The light-receiving optical fiber itself casts a shadow, making it difficult to maintain a constant luminous intensity on printed matter, especially when multiple light-receiving optical fibers are used, such as in color photometry. In some cases, measures such as separating the light-receiving optical fiber from the printing surface are used, but this results in problems such as a corresponding decrease in resolution.
Therefore, as shown in FIG. 7, one light-receiving optical fiber J1 and a plurality of light-emitting optical fibers T1 to T6 are provided, and the light-receiving optical fiber J1 is surrounded by a plurality of light-emitting optical fibers. There is a method of integrating the light emitting/receiving section 100 by arranging it regularly and surrounding it. However, when multiple light-receiving optical fibers are required, such as in the case of color photometry, the number of optical fibers increases, making it difficult to downsize due to the structure, and furthermore, it leads to increased costs. There is.

Therefore, the present applicant has provided a light projecting/receiving device using optical fibers (Japanese Patent Application No. 59-268109) which corrects the above-mentioned drawbacks and can be constructed using a minimum number of optical fibers. As shown in FIG. 8A, the sensor head 6 of this optical fiber light emitting/receiving device consists of one light receiving optical fiber and six light receiving optical fibers surrounding the light receiving fiber and regularly disposed in close contact with each other. A plurality of sets of light emitting/receiving optical fibers 100 each having the same diameter as the light emitting/receiving optical fibers T are arranged in parallel. Optical fiber T for optical use is
It is composed of a plurality of sets of light emitting/receiving optical fibers 101 arranged regularly in this way, with at least one remaining and the others omitted. In this sensor head 6, light is irradiated onto the printed matter 9 by the light emitting optical fiber T, and the reflected light is guided by the light receiving optical fibers R1 to RN, G1 to GN and B1 to BN. Figure B shows the relationship between the light emitting area and the light receiving area, and shows the light emitting area TT1 formed on the printed matter 9 by irradiation by six of the above-mentioned light emitting optical fibers T1 to T6 and their reflections. There is a light receiving area JJ1 of the light receiving optical fiber J1 that receives light. Here, the light-receiving area JJ1 on the printed material and the light-receiving area shared by all the other light-receiving optical fibers exist within the light-emitting area created by irradiating the printed material 9 from all the light-emitting optical fibers T. It's getting old. now,
Regarding figure C showing the EE-EE cross-sectional view, if the distance DD between the light emitting optical fiber 101 and the printed matter 9 and the diameter of one optical fiber are approximately equal, the light emitting area of one light emitting optical fiber is It has been found to span a diameter range of about twice the diameter of the optical fiber or more.
Similarly, regarding the light-receiving region, it is known that the light-receiving optical fiber can detect the amount of light in a range of diameters that are approximately twice or more the diameter of the optical fiber. Here, in FIG. 8A, the light-receiving optical fiber J1 is placed in the center, and the light-receiving optical fiber J2 is placed next to a set of light-emitting and receiving optical fibers consisting of six light-emitting optical fibers T1 to T6. Looking at the transmitting optical fibers of a pair of transmitting and receiving optical fibers centered on It is being understood. In other words, it is sufficient to have at least one light emitting optical fiber between two adjacent sets of light emitting and receiving optical fibers, and the light emitting area TT1,
TT2, TT3...are light receiving areas JJ1, JJ2,...one by one
They are not irradiated singly for the purpose of irradiation, but are omitted so that they can be used for both purposes.

However, when using a sensor head consisting of the light emitting and receiving optical fiber 101, as shown in FIGS. 9A and 9B, the light receiving optical fibers R1, G1, B1,
As shown in Figure B, the light amount Q of the reflected light from the printed matter corresponding to the positions of R2, G2, and B2 is the lowest in the middle of each light-receiving optical fiber, and the light amount Q is the lowest across the entire surface of the printed material. Because it is not constant, defects on the entire printed surface cannot be detected, and the
Using a method of detecting printing defects by comparing the amount of light received by a set of sensor heads has the disadvantage that errors occur and defects cannot be detected accurately.

In addition, a plurality of sets of light emitting and receiving optical fibers, each consisting of one light receiving optical fiber and six light emitting optical fibers surrounding the light receiving fiber and regularly arranged in close contact with each other, are used. The disposed sensor unit has the disadvantage that if the number of optical fibers is large, it becomes very complicated to separately form the light emitting optical fiber and the light receiving optical fiber, and it is difficult to manufacture.

(Object of the Invention) This invention was made in view of the above-mentioned circumstances, and an object of the invention is to detect printed matter in a sensor head consisting of a plurality of light-receiving optical fibers used in color photometry for detecting printing defects. It is an object of the present invention to provide a sensor head for detecting print defects that can perform photometry with constant characteristics using a continuous constant amount of light in the width direction perpendicular to the flow direction of the print head, and can be manufactured extremely easily.

(Summary of the Invention) The present invention relates to a sensor head for detecting printing defects that detects defects in printed matter by performing color photometry. and a plurality of sets of light-receiving optical fiber layers formed in layers using a plurality of glass fibers and arranged alternately so as to be adjacent to each of the light-emitting optical fiber layers; A strip-shaped spacer is sandwiched between the optical fiber layer for light and each of the optical fiber layers for light reception, so that the light emitting and receiving portions are integrated.

(Embodiment of the Invention) FIG. 1 shows an embodiment of the sensor head 1 of the present invention, and as shown in the end face view of _FIG . Light-emitting optical fibers 14A, 14B, 14C, and 14D made of 50-μm glass fibers are closely attached to each other to form a long layer with a width of 250 μm in the width direction perpendicular to the flow direction of the sheet, and the light-receiving optical fiber layer J _R , J _G , and J _B are light receiving optical fibers 11, 12, and 13, respectively, made of glass fibers with the same diameter.
are formed in a layered manner with a width of 785 μm as described above, and there are respective thicknesses between the light emitting optical fiber layer T _T and the light receiving optical fiber layers J _R , J _G , and J _B.
Spacers 15A, 15 are 20 μm ultra-thin strips made of metal such as stainless steel or titanium or synthetic resin.
B, . The length of the sensor head 1 in the width direction perpendicular to the sheet flow direction can be arbitrarily determined according to the dimensions of the printed material. Now, in Figure B showing the AA-AA cross-sectional view, the distance between the sensor head 1 and the printed matter 9 is
If LL is set to about 1mm, it will turn green (G) as shown in the figure.
The G light-receiving area JJ _G of the light-receiving optical fiber layer _JG for the light-receiving optical fiber layer JG has spacers 15C,
Optical fiber layers for light projection on both sides adjacent to each other through 15D
It can be seen that it exists within the light projection area TT _G of T _T and can be photometered. At this time, since the spacer is extremely thin, it has almost no effect on photometry. Similarly, the light-receiving areas of the light-receiving optical fiber layers J _R and J _B for each of the other colors (R, B) are also within the light-emitting areas of the adjacent light-emitting optical fiber layers T _T that are in contact with each other through spacers. It has come to exist and can be photometered.

A method of manufacturing the sensor head 1 having such a structure will be explained with reference to FIGS. 4A to 4E and 5A to 5D.

First, as shown in FIG. 5B, a plurality of light emitting optical fibers 14A are layered to a predetermined thickness in a forming jig 7A having a groove width corresponding to a predetermined length of the sensor head 1 as shown in FIG. 5A. After this arrangement, while injecting adhesive into the gaps between each of the light emitting optical fiber layers _TT , as shown in FIG. Form the gap so that it is completely filled with adhesive.
However, in this case, as shown in FIG.
A problem may arise in that the ends of the T _T are lifted up while being attached to the pressing mold 7B by the adhesive, and this layer is peeled off and cannot be formed.

Therefore, as shown in FIGS. 4A to 4E, a plurality of light emitting optical fibers 14A are first arranged in layers to a predetermined thickness in the groove of the forming jig 7A in FIG. 4A, as shown in FIG. Then, adhesive is injected into the gap between the light emitting optical fiber layers _T and the spacer 15A formed to have the same length as the width of the groove is placed thereon as shown in FIG. Form while applying pressing force. If formed in this way, there will be no adhesive between the press mold and the spacer 15A, as shown in FIG.
As shown in FIG. 3, even when the pressing mold 7B is removed, the above-mentioned layer separation does not occur and the desired formation can be performed. Then, as shown in FIG.
_JR and spacer 15B are formed as described above,
After that, the optical fiber layer for light projection T _T and the spacer 15 are sequentially formed.
By repeating the steps C, light-receiving optical fiber layer J _B , . . . , light-emitting optical fiber layer T _T , a predetermined sensor head 1 can be obtained. Here, the end faces of the sensor head 1 facing the printed surface must be aligned so that the end faces of the optical fiber layers are uniformly lined up on a plane, and during manufacturing, although not shown, the end faces are aligned. It is manufactured by contacting a jig, or by cutting and polishing the end surface after the formation.

The sensor head 1 manufactured in this way is
As shown in FIG. 3A, the two sets of sensor heads 1A and 1B of the above-mentioned printing defect detection device have end faces on the printing surface side formed as shown in the BB-BB sectional view in FIG. The sensor head is used with its longitudinal direction oriented in the width direction, and the terminal end of the light emitting optical fiber layer _T
6 is formed. This light condensing section 16 is shown in FIG.
As shown in the CC-CC cross-sectional view, the light emitting optical fibers are bundled in a circular shape so that they are in close contact with each other. It's getting old. A halogen lamp 17, which is a light emitting source, is provided opposite the end face of the light condensing section 16 through a heat ray shielding plate 18, and only the light rays whose heat rays are blocked by the heat ray shielding plate 18 are transmitted to the light condensing section 16. The light enters from the end face of the sensor head and is irradiated onto a printed matter (not shown) by the light emitting optical fiber of each sensor head. Here, in this invention, since glass fiber is used for each optical fiber, it has good heat resistance, and the halogen lamp 17, which is a powerful light source, can be used, and a sufficient amount of light can be sent to the printing surface. This means that even minute printing defects can be accurately identified.

On the other hand, the optical fiber layers J R , J G , J _B for receiving each color ( _R , _G , B) of the two sets of sensor heads 1A and 1B are
The terminal end of each sensor head is divided into measurement areas for each color, and two sets of sensor heads are made the same and combined into multiple sets, and each color (R, G, , B) This light receiving optical fiber layer is connected to the light receiving elements 10A, 10B, and 10C for each of the measurement areas.
The optical signals of each color received by J _R , J _G , and J _B are transmitted to the paired color sensor elements 10A, 10B, and 1, respectively.
A controller (not shown) calculates the differential voltage between the two sets of light-receiving elements for each color, and by comparing this differential voltage with a preset voltage, printing defects can be detected. Here, since the light-receiving optical fiber is formed so as to be in close contact with the sheet in the width direction perpendicular to the flow direction of the sheet, the photometric characteristics of this light-receiving optical fiber layer are different for each color ( A uniform amount of light Q can be measured continuously in the width direction perpendicular to the flow direction of the sheet for each R, G, B), and printing can be performed continuously and uniformly over the entire printing surface of the printed material as the sheet flows. Defects can be detected.

(Modification of the invention) In the above embodiment, each color (R, G, B)
In this example, the elements are arranged in any order, and the same effect can be obtained by arranging them in any order. It goes without saying that the method can also be applied to monochrome.

(Effects of the Invention) As described above, according to the present invention, the sensor head 1 has a light emitting optical fiber and a light receiving optical fiber formed in layers so as to be in close contact with each other, and a spacer is sandwiched between each layer. In addition, since the light-receiving optical fibers are formed in close contact with each other in a layered manner, a continuous and constant amount of light is produced in the width direction perpendicular to the sheet flow direction on the printing surface. It is possible to provide a printing defect detection sensor head that can perform photometry based on characteristics, can accurately detect even minute printing defects, is easy to manufacture, and has good performance.

[Brief explanation of drawings]

FIGS. 1A and 1B are diagrams showing an embodiment of the present invention,
Figures 2A and B are diagrams explaining this invention, Figure 3A
〜C is a diagram showing an example of application of this invention, FIG. 4A〜
E and FIGS. 5A to 5D are diagrams for explaining the manufacturing method of the present invention, FIGS. 6A and B are diagrams for explaining the printing defect detection device, FIGS. 7, 8A to C, and 9A ,B
1 is a diagram showing a conventional sensor head. 1...sensor head, 9...printed matter, 10...
Pair type color sensor elements, 11, 12, 13...
Optical fiber for light reception, 14A, 14B, 14C, 1
4D... Optical fiber for light projection, 15A, 15B, 1
5C, 15E, 15F... Spacer, 17... Halogen lamp, 18... Heat ray shielding plate.

Claims (1)

[Claims] 1 In a print defect detection sensor head that detects defects in printed matter by performing color photometry, there are multiple sets of light emitting fiber layers formed in layers using multiple glass fibers, and layered fiber layers using multiple glass fibers. and a plurality of sets of light-receiving optical fiber layers arranged alternately adjacent to each of the light-emitting fiber layers, each of the light-emitting fiber layers and each of the light-receiving optical fiber layers. A sensor head for detecting printing defects, characterized in that a band-shaped spacer is sandwiched between the two and the light emitting and receiving parts are integrated.