JPH054333A - Method and device for register control for multicolor printer - Google Patents

Abstract

PURPOSE:To discriminate overprint part of black color and 3 colors without requiring a specific registering mark by a method wherein colors in colored image is separated, further black color image is deducted to convert into cyanogen, magenta and yellow images, and phases of each plate cylinder are adjusted based on each slippage calculated from the black, cyanogen, magenta, and yellow images. CONSTITUTION:An IR camera 28 comprises a filter 27 which permeates only infrared rays in a range of a wave length which is adsorbed by only element of black ink. An IR image signal is inputted to a register adjust circuit 20, binarized, and only a register of black color is detected. An output from a color camera 24 for visible rays is separated in color into image signals of R, G, B and inputted to the register adjust circuit 20, so that respective registers can be obtained. The black color register is deducted from the registers of R, G, and B so as to detect registers of cyanogen, magenta, and yellow. Boundaries of top and bottom, right and left are obtained from 4 images including the register of black color, so as to register by driving a plate cylinder phasing motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a register control method and apparatus for automatically registering each color of a printed matter of a multicolor printing machine.

[0002]

2. Description of the Related Art In ordinary multicolor printing, various colors are reproduced by printing four colors of black, indigo, red and yellow on paper. At this time, it is necessary to print each color so as to match the relative printing position between the colors on the paper surface as much as possible. The tolerance of the degree of coincidence is said to be ± 50 μm or less.

Conventionally, in the registration between colors in a multi-color printing machine, several test prints are first performed, and then the registration amount of those print samples is observed with a magnifying glass or the like. According to the above, the color register was manually adjusted by the register adjusting device of the printing machine. Therefore, the registration work imposes a heavy work burden on the operator of the printing press. For this reason, each company has developed and announced a device for automatically performing color registration in a multicolor printing machine.

As an example, the register adjusting device according to Japanese Patent Laid-Open No. 60-129261 attempts to register a color register before starting printing by putting a register mark on the printing plate to match the positional relationship of the plate materials. Is. However, in this apparatus, there is a problem that it is troublesome to put a mark on the plate material and the registration cannot be accurately performed due to the expansion and contraction of the printing paper, so that it is not used so much in practice. In addition to the above, there is a device that performs registration by reading a special mark printed on printing paper with an optical sensor, but this device also has problems such as the time and labor for inserting the special mark and waste of paper. ing.

[0005]

The above-mentioned prior art has the following problems. (1) In addition to requiring manual skill of a color registration operator, considerable labor and time are required. (2) It takes a lot of time and effort to put a register mark on the register adjustment printing plate disclosed in JP-A-60-129261. Even if the positional relationship of the plate materials is correct, the registration cannot be accurately performed due to the expansion and contraction of the printing paper. (3) How to read the special mark with the optical sensor It takes time and effort to put the special mark on the printing paper. In addition, there is room for marking on the printing paper.

The present invention provides a register control method and a controller for a multi-color printing machine which does not require a special register mark and is capable of distinguishing a black color which is difficult to separate from a color and an overprinted part of other three colors. It is intended to be provided.

[0007]

[Means for Solving the Problems] Means for inputting a magnified image of a cross mark, which is printed together with an actual pattern, as a visible image and an infrared image at the same place at the same time without inserting a special register mark, A means for detecting each color other than black from the visible image data, obtaining an image of only black from the infrared image as a reference position, and calculating the amount of misregistration between the reference position and the three colors other than black; And means for adjusting the register according to the calculated register shift amount.

[0008]

In the multi-color printing machine, the registration of each color is automatically performed by using the cross mark which is printed together with the actual picture at the time of plate making, without inserting a special registration mark. It is possible to distinguish the black color, which is difficult to separate from the color, and the overprinted portion of the other three process colors (indigo, crimson, yellow).

[0009]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the overall configuration of the present invention. Although an embodiment applied to an offset rotary printing press will be described here, the same applies when the target printing press is an offset sheet-fed printing press.

The printing paper 7 is supplied to the printing units 1a to 1d from a roll-shaped roll of paper, and the black ink is fed in each unit.
Indigo, crimson, and yellow patterns are printed in sequence. For example, the black unit 1a includes a front plate cylinder 3a, a front blanket cylinder 4a, a back blanket cylinder 5a, and a back plate cylinder 6a. When the printing paper 7 passes between the two blanket cylinders, the black ink cylinder 1a is used. The ink is pressure-transferred and printing is performed. This also applies to the other units 1b, 1c, 1d. here,
Only the registration of the front surface of the printing paper will be described, but the description can be omitted because the same can be done for the back surface. For registering each color, the register adjustment is performed by adjusting the phase of the plate cylinder 3 in the rotation direction and the rotation axis direction, but the adjustment is usually performed in JP-B-55-25.
As disclosed in Japanese Patent Laid-Open No. 062, etc., the phase matching motors 2a, 2b, 2c, 2d provided on the respective plate cylinders are driven, and since they are known, detailed description thereof will be omitted here.

The printing paper 7 which has completed printing of each color in each printing unit is dried with hot air in the drying section 8, cooled in the cooling section 9, passed through the web path section 15, folded in the folding section 14 and discharged. It Here, a free guide roller 10 (hereinafter referred to as a roller) is provided in a part of the web path unit 15, and an optical fiber is used for printing in order to input the cross mark of the printing paper 7 wrapped around the roller 10. The sensor unit 11 shown in FIG. 2 is provided with a strobe 13 capable of condensing light on the surface, a magnifying photographing device such as a microscope 22, and a half mirror 26 so that a color television camera and an infrared camera can pick up an image of a register mark at the same place. Is provided. The infrared camera of the sensor unit 11 is equipped with a filter 27 that transmits only infrared rays in a wavelength range that is absorbed only by the components of the black ink. The infrared image signal obtained through this filter 27 is registered. It is input to the circuit 20 and binarized at an appropriate binarization level to detect only the black mark. The output from the visible light color camera is color-separated into R, G, and B image signals,
The register marks are input to the register adjusting circuit 20 to obtain the respective register marks. By subtracting the black mark from the R, G, and B register marks obtained by the infrared camera through the filter, indigo, red, and yellow register marks can be detected from the respective R, G, B images. Therefore, four images are combined with the black mark in the infrared image by image processing such as edge detection to obtain the respective top and bottom, left and right boundary lines, and the deviation amount between each boundary line is calculated based on the black boundary line, for example. Then, the plate cylinder phase matching motors 2a, 2b, 2c, 2d of the respective printing units which are required accordingly are driven to complete the registration. Here, the registration may be adjusted according to the total number of continuous printed materials, or may be adjusted once for several sheets.

A reflection type beam sensor called a mark sensor 12 is attached immediately before the sensor unit 11 in the traveling direction of the printing paper 7, and this is a pattern sensor for continuously printing patterns on the printing paper 7. This is for reading the start mark 30 (see FIG. 22) provided at the print start position. The start mark 30 detected by the mark sensor 12 may be placed in the margin of the printing paper 7 as shown in FIG. 22, or if the start mark is not desired to be inserted, it may be the start 31 of the actual printed pattern itself. Further, a rotary encoder 21 is attached to the roller 10, and the register mark position can be treated as a measurement point by counting pulses in response to a start signal from the mark sensor. Further, as shown in FIG. 2, the sensor unit 11 can be freely moved in the left-right direction by a screw 33, and the registration mark at an arbitrary point can be set as the measurement area 32.

FIG. 2 shows the structure of the sensor unit 11. In FIG. 2, the patterns on the printing paper are loaded into the register adjusting device in the following order. The strobe 13 is caused to emit light at the timing of the rotary encoder 21 attached to the roller 10, and the light is applied to the printed printing paper 7 through the optical fiber 23. The reflected light is magnified through a microscope 22 to form an image until dragonfly can be observed, and a half mirror 26 transmits a color television camera head 24 and a filter 27 that transmits infrared rays in a wavelength range that is absorbed only by a component of black ink. An image is formed on each of the infrared cameras 28. The image of the color camera is converted into R, G, B image signals by the color camera controller 25 and sent to the register adjusting circuit 20.

Next, a processing method in the register adjusting circuit will be described. As an example of the method for measuring the register mark registration shown in FIG. 3, the image signals for each color of R, G, B from the color camera are first stored in each frame memory (image recording device). Then, the image signal is binarized with a preset fresh hold value (binarization level). However, this set value can be corrected depending on the operating conditions. The R, G, and B binarized images obtained in this way can be detected as indigo, red, and yellow dragonfly, which are in a color catching relationship. Regarding black ink, theoretically, it is possible to set a stricter threshold value for all of R, G, and B than that described above, and to determine that the common portion is black ink, but the register marks have overlapping colors. Therefore, it is difficult for a visible-light color camera to distinguish the portion where the three colors of indigo, red, and yellow are overlapped from the black ink. Therefore, comparing the infrared spectral reflectance characteristics of each ink as shown in FIGS.
There is a wavelength range in which the reflectance is low only for black ink at a wavelength of 0 nm or 1800 to 2000 nm. Note that FIG.
Shows the spectral reflectance characteristics of white paper, FIG. 5 is black, FIG. 6 is indigo, FIG. 7 is yellow, and FIG. 8 is red. The numbers in the figure show the spectral reflectance at a wavelength of 1900 nm. The image of the infrared camera 28, through which the filter 27 that transmits either wavelength band is watermarked, is stored in the frame memory. Since only the black portion of the image signal has a low reflectance, it can be detected by binarizing with a preset threshold value. As shown in FIG. 9, the black ink portion obtained by this infrared image is used as a mask image of the image of the visible light color camera, and R,
Subtract from G and B images. When the subtracted R, G, and B images are binarized according to the color-capturing relationship, each of FIGS.
You can get indigo, crimson, and yellow dragonflies like 2. However, if the registration is correct and it overlaps with the black registration mark, there will be no binarization result, but it is good because it does not need to be adjusted. In the case where there is a binarization result, in the case of indigo in FIG. 13, for example, the logical product of the image (FIG. 14) shifted in the left-right direction and the self when calculating the up-and-down direction is calculated for each image. As a result, an image having only horizontal components (FIG. 15) is obtained, and the boundaries in the horizontal direction are obtained by edge extraction using a simple logical filter as shown in FIG. In this case, the upper and lower two lines are obtained as shown in FIG. 16, but the one farther than the reference line, for example, the black boundary line is recognized as the boundary. Similarly, the black boundary line on the reference line side is recognized by the filters of FIGS. 17 to 19 as shown in FIG. 18, and the one closer to the boundary line is selected as the reference line and the distance L between the two straight lines is determined as shown in FIG.
Seek as 1. That is the amount of vertical displacement. Similarly, for lateral registration, the same measurement is performed by shifting the image in the vertical direction. However, the filter uses FIG.

First, the overall processing procedure will be described with reference to the lock diagrams and the processing flow shown in FIGS. First, when the operator supports the measurement location, the image of the entire printed matter is photographed by the line sensor of the printed matter inspection apparatus as described in JP-A-63-45545. in this case,
You don't have to worry about colors because you need location information. This image is displayed on the monitor TV, and the operator displays the measurement area with a cursor or the like. Then, the entire sensor unit in FIG. 2 starts moving. Here, it is determined whether or not the instructed measurement location is the cross mark as shown in FIG. This judgment can be sufficiently performed by the discriminant analysis method among the binarization methods. If there is no cross mark, it is necessary to move the sensor unit 11 and repeat until the cross mark is found. If you find it, measure the register.
Then, each color is separated, the register shift amount is measured, and the plate position is adjusted. If printing is in progress, it is possible to constantly monitor and adjust the registration.

[0016]

According to the present invention, means for photographing an enlarged image of an infrared image of a registration pattern and a color image in synchronism with the running speed of printing paper, means for converting the infrared image into a black color image, and the color Based on the same shift amount, a means for color-separating the image and further subtracting the black color image to convert it into an indigo, red, yellow image, and a means for calculating the shift amount of each image from the black, indigo, red, and yellow images By including means for adjusting the phase of each plate cylinder, the following effects are obtained. (1) Since no special mark is added, the work of the plate making department can be saved. (2) Since no special mark is inserted, an extra space for printing paper is not required, which saves paper and saves the conventional work of removing the mark portion.

[Brief description of drawings]

FIG. 1 is a schematic view of a commercial offset rotary press according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of the sensor unit of FIG.

FIG. 3 is a diagram showing an overlap of cross marks of respective colors.

FIG. 4 is a diagram showing a spectral reflectance characteristic of white paper.

FIG. 5 is a diagram showing a spectral reflectance characteristic of black ink.

FIG. 6 is a diagram showing a spectral reflectance characteristic of indigo.

FIG. 7 is a diagram showing a spectral reflectance characteristic of yellow.

FIG. 8 is a diagram showing spectral reflectance characteristics of crimson.

FIG. 9 is a diagram showing a black mark (mask image) obtained from an infrared image.

FIG. 10 is a diagram showing indigo marks as a result of binarizing and masking an image of a color camera.

FIG. 11 is a diagram showing a crimson dragonfly as a result of binarizing and masking an image of a color camera.

FIG. 12 is a diagram showing a yellow register mark as a result of binarizing and masking an image of a color camera.

FIG. 13 is a diagram showing a first step of a method of measuring the amount of misregistration using indigo as an example.

FIG. 14 is a diagram showing a next step of FIG. 13.

FIG. 15 is a diagram showing a next step of FIG. 14.

16 is a diagram showing a next step of FIG. 15. FIG.

FIG. 17 is a diagram showing a next step of FIG. 16.

FIG. 18 is a diagram showing a next step of FIG. 17.

FIG. 19 is a diagram of a spatial filter for obtaining the amount of deviation in the vertical direction.

FIG. 20 is a diagram of a spatial filter that obtains a shift amount in the left-right direction.

FIG. 21 is a diagram showing a result of measuring the amount of misregistration.

FIG. 22 is a diagram showing an example of measurement locations on a printed matter.

FIG. 23 is a block diagram of an embodiment of the present invention.

FIG. 24 is a processing flow of an example of the present invention.

[Explanation of symbols]

1a printing unit 1b printing unit 1c printing unit 1d printing unit 7 printing paper 10 Free guide roller 11 Sensor unit 13 Strobe 20 Register adjustment circuit

Claims (2)

[Claims] 1. An infrared image and a color image of a registration pattern of printed paper are taken, and these images are converted into four images of black, indigo, red and yellow, and each color image is based on the black image. A register control method for a multi-color printing press, which comprises calculating a shift amount of each plate cylinder and adjusting the phase of each plate cylinder based on the shift amount. 2. A means for photographing an enlarged image of an infrared image of a registration pattern and a color image in synchronism with the running speed of printing paper, a means for converting the infrared image into a black color image, and color separation of the color image. In addition, subtract the above black color image to indigo,
It comprises means for converting into a red and yellow image, means for calculating a shift amount of each image from the black, indigo, red and yellow images, and means for adjusting the phase of each plate cylinder based on the same shift amount. A register control device for a multi-color printing machine, characterized by: