JPH06311357A - Method and device for generating gravure printing dot cell - Google Patents

Abstract

PURPOSE:To reduce an overlapped part of dot cells of plural color plate by placing centers of dot cells of the color plates at each intermediate position so that pitches of dot cells are equal to each other as dot cell arrangement of plural color plates. CONSTITUTION:An original picture input section 10 receives a color separation picture signal from an original picture OR, a picture processing section 20 edits the signal and stores the result to an external storage device 26. Then an interpolation processing section 23 of a control section 22 executes interpolation processing of the color separation picture signal and initializes a color plate of a processing object, pitches Px, Py in the main scanning direction and the sub-scanning direction, and coordinates of engraving positions (X, Y)=(X0, Y0), then calculates sequentially X coordinates of the engraving positions, provides an engraving start position of an odd number line as a coordinate (X0+1/2Px, Y+1/2Py) and the engraving start position of an even number lipe as a coordinate (x0, Y+1/2Py) to generate an engraving picture signal Sc in each scanning line and gives it to an engraving section 30. The engraving section 30 uses a graver 34 to engrave a dot cell onto the surface of a copper member 32 based on the signal Sc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a halftone dot cell forming method for gravure printing and a halftone dot cell forming apparatus for gravure printing, in which halftone dot cells are engraved on the surface of a plate cylinder member for gravure printing.

[0002]

2. Description of the Related Art In gravure printing, the amount of ink filled in the recesses is adjusted by adjusting the volume of minute recesses (dot cells) formed on the surface of the plate cylinder, and the density of the printed image is adjusted. Is a printing method that expresses.

The plate cylinder used for gravure printing is a cylindrical plate cylinder member having a large number of halftone dot cells arranged periodically on the surface thereof. As a method of forming a halftone dot cell, a method of etching the surface of the plate cylinder member has been conventionally used, but in recent years, an electronic engraving gravure for engraving the surface of the plate cylinder member using an electronic engraving machine has been adopted. There is.

In color printing, color prints are made by printing inks of four colors, yellow (Y), magenta (M), cyan (C), and black (K).
The electronic engraving machine engraves dot cells on the surface of the plate cylinder based on the color-separated image signals for the respective colors to create the plate cylinders for the four colors, respectively. The area and depth of each halftone dot cell are adjusted according to the level of the color separation image signal at each halftone dot cell position.

As a method of forming a halftone dot cell for gravure, for example, the method described in Japanese Patent Publication No. 57-19972 is known. According to this method, as shown in FIG. 1 of the publication, in the first color plate, the pitch of the halftone dot cells is compressed in the scanning direction of the plate cylinder and the pitch of the halftone dot cells is extended in the feeding direction. On the other hand, in the second color plate, conversely, the pitch of the halftone dot cells is extended in the scanning direction of the plate cylinder and the pitch of the halftone dot cells is shortened in the feeding direction. By doing so, a halftone dot cell corresponding to the resolution of the image information is formed.

[0006]

However, in the above-mentioned prior art, there is a large number of overlapping portions of halftone dot cells in each color plate, so that there is a problem that the saturation of the color expressed in the color printed matter is impaired. is there. Further, if there are many overlapping portions of halftone dot cells, there is also a problem that the glossiness of the printed matter becomes low because the proportion of the white paper portion on which the ink is not applied increases in the image area where the density is low.

The present invention has been made to solve the above-mentioned problems in the prior art, and when forming halftone dot cells of gravure, reduces the overlapping portion of the halftone dot cells of a plurality of color plates. The purpose is to

[0008]

In order to solve the above-mentioned problems, a first method according to the present invention is a gravure printing plate for each color plate based on a plurality of color separation image signals representing a color image. A method for forming halftone dot cells for gravure printing, in which halftone dot cells are engraved on the surface of a body member,
(A) preparing a plurality of color-separated image signals representing the color-separated image of each color plate at a common coordinate position arranged on the image plane; and (b) interpolating each color-separated image signal with respect to the position of a halftone dot cell. When generating an engraving image signal for each color plate by calculation, the halftone dot cell array of at least two color plates is such that the pitches of the halftone dot cells along the same direction are equal to each other, and the at least two colors A step of setting a halftone dot cell array in which the centers of halftone dot cells of the plate are located in the middle of each other and generating an engraving image signal for defining each halftone dot cell size at each halftone dot cell position for each color plate. And (c) engraving a halftone dot cell on the plate cylinder member of each color plate based on the engraving image signal.

In the first method described above, as a halftone dot cell array of at least two color plates, the pitches of the halftone dot cells along the same direction are equal to each other, and the halftone dot cells of the at least two color plates are equal to each other. Since the dot cell arrays whose centers are located in the middle of each other are set, the dot cells of these color plates do not overlap.

A second method according to the present invention is a method of forming halftone dot cells for gravure printing, in which halftone cells are engraved on the surface of a plate cylinder member for gravure printing, and (a) preparing a plurality of color separation images And (b) when generating the engraving image signal for each color plate by sequentially mounting and reading the color separation images one by one at the same position of the image reading device, the halftone dot cells of at least two color plates. As an array, a halftone dot cell array in which the pitches of the halftone dot cells along the same direction are equal to each other and the centers of the halftone dot cells of the at least two color plates are located in the middle of each other are set, and each halftone dot cell array is set. A step of generating an engraving image signal that defines the size of the halftone cell at the dot cell position; and (c) engraving the halftone cell on the plate cylinder member of each color plate based on the engraving image signal. Prepare

In the second method described above, in addition to the operation of the first method, the image signals for engraving with respect to each color plate are obtained by sequentially mounting and reading each color separated image one by one at the same position of the image reading device. Since it is generated, the engraving image signal can be obtained without performing the interpolation calculation.

A third method according to the present invention is a gravure printing halftone dot for engraving a halftone dot cell on the surface of a plate cylinder member for gravure printing for each color plate based on a plurality of color separation image signals representing a color image. A method for forming a cell, comprising: (a)
Preparing a plurality of color-separated image signals representing the color-separated image of each color plate at a common coordinate position arranged on the image plane, and (b) interpolating each color-separated image signal with respect to the position of a halftone dot cell. When the engraving image signal for each color plate is generated by the halftone dot cells, the halftone dot cells having the same pitch along the main scanning direction and the halftone dots along the sub-scanning direction for each of the magenta, cyan, and black plates. The size of the halftone dot cell at each halftone dot cell position is set by setting the halftone dot cell array in which there are no plates with the same cell pitch and the centers of the halftone dot cells of each plate are arranged at different positions. For each color plate, and (c) engraving halftone cells on the plate cylinder member of each color plate based on the engraving image signal.

In the third method described above, the halftone dot cell pitches along the main scanning direction are equal to each other and the halftone dot cell pitches along the sub scanning direction are the same for each of the magenta, cyan, and black plates. Even if there are no plates that are equal to each other, and the centers of the dot cells of each plate are set at positions different from each other, the dot cell array is set, so even if the plates are slightly shifted, the overlapping parts of the dot cells will overlap. The ratio of does not become excessively large.

A fourth method according to the present invention is a method of forming halftone dot cells for gravure printing in which halftone cells are engraved on the surface of a plate cylinder member for gravure printing, and (a) prepares a plurality of color separation images. And (b) each color separation image is sequentially mounted and read at the same position of the image reading device to generate an engraving image signal for each color plate, and each magenta, cyan, and black plate is generated. On the other hand, there is no plate in which the pitches of the halftone cells along the main scanning direction are equal to each other and the pitches of the halftone cells along the sub-scanning direction are also equal to each other, and the centers of the halftone cells of each plate are A step of setting halftone dot cell arrays arranged at mutually different positions to generate an engraving image signal defining the size of the halftone dot cell at each halftone dot cell position; and (c) based on the engraving image signal. The plate body of each color plate In comprising the step of engraving a halftone cell, a.

In the fourth method described above, in addition to the operation of the third method, the color separation images are sequentially mounted one by one at the same position of the image reading apparatus and read, whereby the engraving image signal for each color plate is obtained. Since it is generated, the engraving image signal can be obtained without performing the interpolation calculation.

A first apparatus according to the present invention is a gravure printing halftone dot for engraving a halftone dot cell on the surface of a plate cylinder member for gravure printing for each color plate based on a plurality of color separation image signals representing a color image. A cell forming device, a storage means for storing a plurality of color separation image signals representing color separation images of each color plate at a common coordinate position arranged on an image plane, and a position of halftone cell for each color separation image signal. Is a means for generating an engraving image signal for each color plate by interpolating with respect to each of the color plates, wherein the halftone dot cell arrays of at least two color plates have equal pitches of the halftone dot cells along the same direction, and An engraving image that defines the size of a halftone dot cell at each halftone dot cell position by setting a halftone dot cell array in which the centers of at least two halftone dot cells are located in the middle of each other. Comprises engraving signal generating means for generating for each color plate the item, and a sculpture means for engraving the halftone cell to the plate cylinder member of each color plate in accordance with the engraving image signal.

In the above-mentioned first apparatus, the engraving signal generating means has a halftone dot cell arrangement of at least two color plates, and the pitches of the halftone dot cells along the same direction are equal to each other, and the at least two of the at least two color dot cells are arranged. Since the engraving image signal is generated for each color plate by setting the dot cell array in which the centers of the halftone dot cells of the color plates are located in the middle of each other, the halftone dot cells of these color plates do not overlap. .

A second apparatus according to the present invention is a gravure printing halftone cell forming apparatus for engraving halftone cells on the surface of a plate cylinder member for gravure printing using a plurality of color separation images prepared in advance. A means for generating an engraving image signal for each color plate by sequentially reading each color separation image mounted at the same position one by one, and as a halftone dot cell array of at least two color plates, in the same direction. The pitch of the halftone dot cells along each other is equal to each other, and the halftone dots at each halftone dot cell position are set while setting the halftone dot cell array in which the centers of the halftone dot cells of the at least two color plates are located in the middle of each other. An engraving signal generation unit that reads an engraving image signal that defines the size of the cell, and an engraving unit that engraves a halftone dot cell on the plate cylinder member of each color plate based on the engraving image signal are provided.

In the above-mentioned second apparatus, in addition to the operation of the apparatus of the first apparatus, the engraving signal generating means sequentially reads each of the color separation images mounted at the same position one by one, and thereby the color plates are separated. Since the image signal for engraving is generated, the image signal for engraving can be obtained without the need for means for interpolation calculation.

A third device according to the present invention is a gravure printing halftone dot for engraving a halftone dot cell on the surface of a plate cylinder member for gravure printing for each color plate based on a plurality of color separation image signals representing a color image. A cell forming device, a storage means for storing a plurality of color separation image signals representing color separation images of each color plate at a common coordinate position arranged on an image plane, and a position of halftone cell for each color separation image signal. Is a means for generating an engraving image signal for each color plate by performing an interpolation calculation with respect to each of the color plates, and the pitches of the halftone cells along the main scanning direction are equal to each other and sub There is no plate whose pitches of halftone cells along the scanning direction are equal to each other, and the centers of halftone dot cells of each plate are set at positions different from each other to set each halftone dot cell array. Engraving signal generating means for generating, for each color plate, an image signal for engraving which defines the size of the dot cell at the dot cell position, and engraving the dot cell on the plate cylinder member of each color plate based on the image signal for engraving. And engraving means.

In the above-mentioned third apparatus, the engraving signal generating means has the same pitch in the halftone dot cells along the main scanning direction with respect to each of the magenta, cyan and black plates and in the sub scanning direction. There is no plate whose pitch of halftone dot cells along each other is equal to each other, and the center of halftone dot cells of each plate is set at a position different from each other, and the image signal for engraving is set for each color plate. Therefore, even if the plates are slightly deviated from each other, the ratio of the overlapping portion of the halftone dot cells does not become excessively large.

A fourth apparatus according to the present invention is a halftone dot cell forming apparatus for gravure printing, which engraves halftone cells on the surface of a plate cylinder member for gravure printing using a plurality of color separation images prepared in advance. It is a means for generating an engraving image signal for each color plate by sequentially reading each color separation image mounted at the same position one by one, and performing main scanning for each magenta, cyan, and black plate. The pitch of halftone dot cells along the direction is equal to each other and the pitch of halftone dot cells along the sub-scanning direction is also equal to each other, and there is no plate, and the centers of the halftone dot cells of each plate are arranged at different positions. And a plate cylinder for each color plate on the basis of the engraving image signal, by setting the dot cell array and reading the engraving image signal that defines the size of the dot cell at each dot cell position. For members Comprising engraving means for engraving the point cells, a.

In the above-mentioned fourth apparatus, in addition to the operation of the third apparatus, the engraving signal generating means sequentially reads each of the color separation images mounted at the same position one by one, thereby engraving each color plate. Since the image signal is generated, the image signal for engraving can be obtained without the need for means for interpolation calculation.

[0024]

EXAMPLES A. First Embodiment: FIG. 1 is a block diagram showing an electronic engraving system to which an embodiment of the present invention is applied. This electronic engraving system is composed of an original image input unit 10, an image processing unit 20, and an engraving unit 30.

The original image input section 10 has an original image cylinder 12 and a reading head 14. The original image OR is attached to the outer peripheral surface of the original image cylinder 12, and the original image cylinder 12 rotates at a constant speed. The reading head 14 is the original cylinder 12
The image of the original image OR is read while moving in a direction parallel to the axial direction of. As a result, the image of the original image OR is separated into a predetermined color, and a plurality of color separated image signals are obtained. Normally, color separation is performed into four colors of Y (yellow), M (magenta), C (cyan), and K (black). The plurality of color-separated image signals Ss thus obtained are stored in the external storage device 2 of the image processing unit 20.
6 is stored in the form of color separated image data.

The color separated image signal Ss is a signal indicating the density of each color for each pixel of a predetermined size. FIG. 2 is an explanatory diagram showing the arrangement of the centers of the pixels, and the centers Q of the pixels are shown by lattice points of a square lattice. In this example, the pitch Pi of the pixels in the main scanning direction is equal to the pitch Pi of the pixels in the sub scanning direction.
The main scanning direction X corresponds to the circumferential direction of the original image cylinder 12, and the sub scanning direction Y corresponds to the axial direction of the original image cylinder 12. The pixel positions shown in FIG. 2 are common to each color plate. That is, the color separation image signal for each color of YMCK represents the density of each color at the common pixel position. As the color separation image signal, a color separation image signal created for offset printing by another device can be used.

The image processing unit 20 includes a control unit 22, a color monitor 24, and a mouse 28 in addition to the external storage device 26. The operator edits the image using the mouse 28 or the like while looking at the image displayed on the color monitor 24. Editing an image includes synthesizing a plurality of original images, correcting an image, and determining the layout of a plurality of image parts.
The color separated image signal is edited according to the editing of the image, and the edited color separated image signal is stored in the external storage device 26 as color separated image data. Editing of this image is the same as that performed in the layout system for offset printing.

The color separation image signal after editing is processed by the interpolation processing unit 2
3, the engraving image signal Sc at each halftone dot cell position
And the engraving image signal Sc is applied to the engraving section 30.

The engraving section 30 forms halftone cells by engraving the cylindrical plate body member 32 with the engraving blade 34 in accordance with the engraving image signal Sc. The plate body member 32 is a metal cylinder, and the cutting edge of the engraving blade 34 is diamond. FIG. 3 is a plan view showing an array of halftone dot cells of K plate. The basic structure of a halftone dot cell is composed of four halftone dot cells KCa to KCd arranged in a square shape and a halftone dot cell KCe arranged at the face center position. In this example, the pitch Px in the main scanning direction and the pitch Py in the sub scanning direction of the basic structure of the halftone dot cell are equal. Further, FIG. 3 shows the pitches Px and P.
Both y are shown to be 2.5 times the pitch Pi described in FIG. The coordinates (X0, Y0) indicate the engraving start position of the halftone dot cell.

FIG. 4 is a plan view in which the center position of the halftone dot cell shown in FIG. 3 and the center position Q of the pixel for the color separation image signal shown in FIG. As you can see from Figure 4,
Since the position of the halftone dot cell KC is different from the center position Q of the pixel for the color separated image signal, when forming the halftone dot cell KC, the color separated image signal is interpolated and the color separated image signal at the position of each halftone dot cell is obtained. The value of must be calculated. That is, the value of the color separation image signal (that is, the image signal for engraving) at the position of each halftone dot cell is obtained by interpolating the color separation signal at the pixel position near the halftone dot cell, for example, by linear interpolation. This interpolation calculation is executed by the interpolation processing unit 23 in the control unit 22. As the interpolation calculation method, for example, the method described in Japanese Patent Publication No. 55-33060 can be used.

The engraving section 30 has a screen signal having a frequency (for example, 5 KHz) corresponding to the pitch Px in the main scanning direction, and the engraving image signal Sc provided from the interpolation processing section 23.
And are superimposed to generate a drive signal for the engraving blade 34. The engraving blade 34 is pressed toward the surface of the plate cylinder member 32 at a depth corresponding to the level of the drive signal, and halftone dot cells are formed on the surface of the rotating plate cylinder member 32. Each halftone dot cell has an inverted pyramid shape. Since the amount of ink is determined by the volume of the halftone dot cell, the halftone dot cell is deeply engraved in a high density image area, and the halftone dot cell is shallowly engraved in a low density image area.

FIG. 5 is a plan view showing the relationship between the pixel center position and the halftone dot cell for the C plate. The position of the center Q of the pixel in FIG. 5 is the same as that in FIG. The coordinates of the engraving start position of the halftone dot cell CC of the C plate are (X0 + 1 / 2Px, Y0
). FIG. 6 is a plan view showing the arrangement of the K plate halftone dot cells KC and the C plate halftone dot cells CC. The K and C halftone dot cells are not formed on the surface of one plate cylinder, but the plate cylinders of each color plate are separately prepared.

In the arrangement of the halftone dot cells of the K plate and the C plate in FIG. 6, the pitches along the same direction are equal to each other, and the halftone dot cell pitches Px are shifted from each other along the main scanning direction X. is doing. Alternatively, it can be seen that they are shifted from each other by half the pitch Py along the sub-scanning direction Y. In other words, the K plate halftone dot cell KC and the C plate halftone dot cell CC have their centers located at the centers of the mutual gaps. In the arrangement shown in FIG. 6, the K plate halftone dot cell KC and the C plate halftone dot cell CC do not overlap.

FIG. 7 is a plan view showing the arrangement of halftone dot cells KC and CC in an image area having a density of 100%. Even when the halftone dot cell becomes large in this way, the overlapping portion of the two types of halftone dot cells KC and CC is minimized.

FIG. 8 shows the halftone dot cell array of FIG.
FIG. 6 is a plan view in which a halftone dot cell MC of a plate and a halftone dot cell YC of a Y plate are added. Note that the patterns of the respective colors match each other in the state of FIG. 8, and by printing four colors of ink in the state of FIG. 8, a printed matter without misregistration can be obtained.

The structure of the halftone dot cell of each color plate in FIG. 8 is as shown in Table 1 below, and the engraving disclosure position differs for each color plate.

[Table 1] In Table 1, the scanning pitch is the pitch of halftone cells,
Pi is the pixel pitch for the color separated image signal (see FIG. 2).

In the halftone dot cell array shown in FIG. 8, the pitches along the same direction are equal in each plate. In addition, in the center of the gap between the halftone dot cell of the K plate and the halftone dot cell of the C plate (see FIG. 6),
Halftone cells of the M version and halftone cells of the Y version are arranged. Alternatively, it can be considered that the K-plate halftone cell and the C-plate halftone cell are arranged in the center of the gap between the M-plate halftone cell and the Y-plate halftone cell. In order to achieve such an arrangement, as shown in Table 1 above, the engraving start position of the halftone dot cell of the M plate is set to a position shifted by 1 / 4Px and 1 / 4Py from the engraving start position of the K plate. , The engraving start position of the halftone dot cell of the Y plate is set to a position shifted by 1 / 4Px and 1 / 4Py from the engraving start position of the C plate.

By arranging the halftone dot cells of each color plate as shown in FIG. 8, an overlapping portion of the halftone dot cells of each color plate is generated in the highlight portion (that is, the state of FIG. 8) in which the size of the halftone dot cell is small. You can avoid it. As a result, it is possible to reduce the proportion of the white paper portion on which the ink is not applied, so that it is possible to improve the saturation of the color expressed in the printed matter.
Further, in the example of FIG. 8, the density of the halftone dot cells of each color plate (the number of halftone dot cells per unit area) is equal to each other, which is advantageous in that the resolution of each color plate is equal. Further, in the example of FIG. 8, the distance between the halftone dot cells adjacent to each other in the main scanning direction X and the distance between the halftone dot cells adjacent to each other in the sub scanning direction Y are both equal, and 45 degrees with respect to the main scanning direction X. The distance between adjacent halftone dot cells in the rotated direction and the distance between adjacent halftone dot cells in the direction rotated 45 degrees with respect to the sub-scanning direction Y are also equal. This means that if one halftone dot cell and eight halftone dot cells surrounding it are considered, one halftone dot cell is eight.
That is, it is in the farthest position for all one halftone dot cells. Therefore, even if a certain color plate is misaligned at the time of printing, there is an advantage that it is unlikely to overlap with a halftone dot cell of another color plate. This advantage contributes to the improvement of the saturation of the color expressed in the printed matter, especially in the highlight portion where the halftone dot cells are small.

In the examples of FIGS. 6 and 8, the halftone dot cell of each color plate is located exactly in the center between the other halftone dot cells, but it may be slightly displaced from the center. That is, the center of the halftone dot cell of each color plate may be arranged at a position to fill the gap between the other halftone dot cells.

FIG. 9 is a flow chart showing the processing procedure in the first embodiment. In step S1, the original image input unit 10 reads the color separated image signal from the original image OR, and in step S2, the read color separated image signal is edited,
The edited color-separated image signal is stored in the external storage device 26. In step S3, the image processing unit 20 interpolates the color-separated image signal to generate an engraving image signal. FIG. 10 is a flowchart showing the detailed procedure of step S3.

In step S31, the color plate to be processed (first is the K plate), the pitch Px in the main scanning direction and the sub-scanning direction,
Py and the coordinates of the engraving position (X, Y) = (X0, Y0) are initialized.

Steps S32 to S34 are a process of generating an engraving image signal for the halftone dot cells along the odd-numbered scanning lines. The scanning line referred to here is, as shown in FIG.
Scan lines SL1 passing over the halftone dot cells along the main scanning direction X
SL2 and SL3.

In step S32, the value of the engraving image signal at the coordinates (X, Y) of the engraving position is obtained by interpolation calculation. This interpolation calculation is performed according to the method described in Japanese Patent Publication No. 55-33060, as described above.

In step S33, the X coordinate of the next engraving position is calculated. The Y coordinate remains unchanged while steps S32 to S34 are repeated. In step S34, it is determined whether the end of the main scanning direction has been reached or not depending on whether the main scanning coordinate X has become equal to or larger than a predetermined maximum value. If the end of the main scanning direction is not reached, step S3
The process returns from step 4 to step S32 to generate an engraving image signal for the next halftone dot cell. On the other hand, when the end of the main scanning direction is reached, the process proceeds to step S35, and the engraving start position of the next scanning line is calculated. The engraving start position of the next scanning line (even number) is the coordinates (X0 + 1 / 2Px, Y + 1 / 2P
y). Referring to FIG. 3, the engraving start position on the first scanning line SL1 is the position of the halftone dot cell KCa, and the engraving start position on the second scanning line SL2 is the position of the halftone dot cell KCe. .

In step S36, it is determined whether the processing has been completed for all the scanning lines of the color plate. If not completed, the process proceeds to step S37, and the process is started along the even-numbered scan lines.

Steps S37 to S42 are step S4.
The calculation formula in 1 is different from the calculation formula in step S35, and is the same as steps S32 to S36 described above. The engraving start position of the next scanning line (odd number) calculated in step S41 is given by coordinates (X0, Y + 1 / 2Py).

By repeating steps S32 to S36 and steps S37 to S42, the engraving image signal for each scanning line is created. In step S4 of FIG. 9, halftone dot cells having a size corresponding to the engraving image signal are engraved on the surface of the plate cylinder member 32.

When the plate cylinder is completed for one color plate, the process returns from step S5 to step S3. At this time, a new plate cylinder member is set in the engraving section 30. In this way, by repeating steps S3 to S5, the plate cylinders for four color plates are created.

B. Second Embodiment: FIG. 11 is a plan view showing an arrangement of halftone dot cells in a second embodiment of the present invention. In the arrangement of FIG. 11 as well, similar to FIG. 3, the basic structure of the halftone dot cell is four halftone dot cells KCa arranged in a rectangular shape.
.About.KCd and halftone dots KCe arranged at the face center position. However, the pitch Px in the main scanning direction in FIG. 11 is shorter than that in FIG. 3, and the pitch Py in the sub scanning direction is expanded. The pitch ratio in FIG. 11 is Px: Py = 2: 3.

When the basic structure of the halftone dot cell is a rectangle as shown in FIG. 11, the shape of the bottom surface of the halftone dot cell is composed of sides parallel to the diagonal line of the rectangle (shown by a broken line in the figure). It becomes a diamond. This is because the banks (unengraved portions) between the halftone dot cells KC are formed in parallel. In this way, as shown in FIG. 12, even when a halftone dot cell having an image density of 100% is formed, there is no portion where the width of the bank is extremely narrow.

FIG. 13 is a plan view showing the arrangement of K-plate halftone dot cells KC and C-plate halftone dot cells CC in the second embodiment. Also in FIG. 13, as in FIG. 6, the array of halftone dot cells KC for K plate and the array of halftone dot cells CC for C plate have equal pitches along the same direction, and the main scanning direction X.
Is shifted by half the pitch Px of the halftone dot cells. In other words, the centers of the K-plate halftone cell KC and the C-plate halftone cell CC are located at the centers of each other.

FIG. 14 is a plan view showing an arrangement of four-version halftone dot cells in the second embodiment. The structure of the halftone dot cell of each color plate in FIG. 14 is as shown in Table 2 below, and the engraving disclosure position is different for each color plate.

[Table 2]

As can be seen by comparing Table 2 and Table 1, FIG.
The halftone dot cell structure of No. 4 is the halftone dot cell structure of FIG.
Only the values of x and Py (pitch of halftone dot cells) are different. Therefore, this second embodiment also has the same effect as the first embodiment.

C. Third Embodiment: FIG. 15 is a plan view showing an arrangement of halftone dot cells MC of the M plate and halftone dot cells YC of the Y plate in the third embodiment. In the array of FIG. 15, the values of the scanning pitches Px and Py are opposite to those of the array of FIG. Figure 1
The halftone dot cells MC and YC shown in FIG. 5 and the halftone dot cell K shown in FIG.
When C and CC are overlaid and displayed, the arrangement of FIG. 16 is obtained. In FIG. 16, the pitches of the KCMY plates in the main scanning direction are denoted by Pxk, Pxc, Pxm, Pxy, and the pitches in the sub-scanning direction are denoted by Pyk, Pyc, Pym, Pyy, respectively. The halftone dot cell structure of FIG. 16 is as shown in Table 3 below.

[Table 3]

In the halftone dot cell array of FIG. 16, the overlapping portion of the halftone dot cells is slightly larger than the arrangements of FIGS. 8 and 14, but the proportion of the overlapping portion is still small.
Most halftone cells do not overlap each other. FIG.
The overlapping state of the halftone dot cells does not change much when the arrangement of FIG. 13 and the arrangement of FIG. 15 are slightly shifted and overlapped. That is, even if the halftone dot cells of the M plate and the Y plate are slightly displaced from the positions shown in FIG. 16, the overlapping portions between the halftone dot cells in FIG. 16 disappear and the overlapping portions occur only in other places. Further, in general, even if the Y plate is displaced, the quality of the printed matter is not significantly affected. Considering such a matter, in the third embodiment, if the positional relationship between the halftone dot cells of the K plate and the C plate (that is, the positional relationship of FIG. 13) is accurately managed, it becomes 4
When the color inks are overprinted, the ratio of the overlapping portions of the halftone dots can be kept substantially constant. That is, since it is not necessary to accurately control the positions of all the halftone dot cells of the four color plates, there is an advantage that the plate cylinder can be easily manufactured.

D. Fourth Embodiment: In the halftone dot cell array in the first embodiment (FIG. 8), the second embodiment (FIG. 14), and the third embodiment (FIG. 16) described above, scanning in the main scanning direction is performed. There are at least two plates whose pitches are equal to each other and whose scanning pitches in the sub-scanning direction are also equal to each other. Therefore, when plate misregistration occurs during printing, the halftone dot cells of the two plates may overlap in the entire printed matter.

In order to prevent such a possibility, the fourth
In the embodiment, among the three color plates of KCM, halftone dot cells of each color plate are arranged so that there are no color plates having the same scanning pitch in the main scanning direction and the same scanning pitch in the sub scanning direction. To set. In other words, when two arbitrary color plates among the three color plates are compared, the halftone dot cells in the main scanning direction or the halftone dot cells in the sub-scanning direction have different pitches. Sets the array of point cells. As described above, the shift of the halftone dot cells of the Y plate does not have a great influence on the quality of the printed matter, so the scanning pitch can be set relatively freely.

FIG. 17 is a plan view showing the arrangement of halftone dot cells in the fourth embodiment. Table 4 below shows the dot structure of FIG.

[Table 4] Further, in the fourth embodiment, the engraving start position of each color plate is set so that the centers of the halftone dot cells of each KCM color plate do not overlap each other in the highlight part (low density part) of the image.

In the fourth embodiment, the ratio of the pitches Pxk, Pxc, Pxm of the KCM three-color halftone dot cells in the main scanning direction is 2:
The ratio of the pitches Pyk, Pyc, and Pym in the sub-scanning direction is 2: 3: 2. Thus, if the pitch of the halftone dot cells of each color plate is set to an integer ratio, as shown in FIG. 17, the cycle In (= 6 of the entire overprinted halftone dot cell array is obtained.
Pi) becomes a relatively short length represented by the least common multiple (2 × 3 = 6) of the integer of the ratio. When the cycle of the halftone dot cell array is short, there is an advantage that a pattern (moire) generated due to the periodicity of the array becomes inconspicuous. From this point of view, it is preferable to represent the integer ratio of the pitch of the halftone dot cells of each color plate by using an integer as small as possible, and particularly preferably an integer ratio using an integer of 10 or less.

In the example of FIG. 17, the area (Pxk × Pyk) of the basic structure of the halftone dot cell of the K plate is smaller than the area of the unit structure of the halftone dot cell of the C plate or M plate. This means that the density of the halftone dot cells of the K plate is higher than that of the halftone dot cells of the C plate and the M plate. As described above, setting the density of halftone dot cells of the K plate higher than the halftone dot cell densities of the other plates has the advantage that the contour of the image of the K plate can be expressed at a relatively high resolution.

FIG. 18 is a plan view showing a state in which the positions of the M halftone dot cells are displaced from the halftone dot cell array of FIG. In FIG. 18, there is a portion where the M-version halftone dot cell and the C-version halftone dot cell overlap, but even in most areas, there is no overlapping portion between the halftone dot cells. Thus, FIG.
Adopting the halftone dot cell arrangement as shown in 7 has an advantage that the ratio of the overlapping portion of the halftone dot cells can be suppressed to be small even when the plate of a certain color is displaced.

The present invention is not limited to the above-described embodiments, but can be carried out in various modes without departing from the scope of the invention, and the following modifications can be made.

(1) Instead of interpolating a color separated image signal obtained by reading a color original image to generate an engraving image signal, a previously prepared color separated image is read and an engraving image signal for gravure printing is obtained. There is also a way to get. Here, as the color separation image, a continuous tone image obtained by exposing the photographic paper with an optical color separation image signal or a halftone plate image (film or photographic paper) for offset printing can be used. .

When reading the color separation image created in advance, it is necessary to accurately position the color separation image of each plate in the original image cylinder 12 (FIG. 1). FIG. 19 is a conceptual diagram showing the original image input unit 10a capable of accurately positioning the color separated image CS. This original image input section 10a
Two positioning pins 15 and 16 are provided upright on the surface of the original image cylinder 12a. In each color separation image CS,
A punch hole is punched at a position corresponding to the distance between the positioning pins 15 and 16 and having an exactly common relative position with respect to the image. By doing so, it is possible to accurately position the original image of each color plate simply by fitting the punched holes of each color separation image into the positioning pins 15 and 16. In addition,
The height of the positioning pins 15 and 16 is 1 to 2 mm so that the positioning pins 15 and 16 do not collide with the read head 14.
It is preferable to set to.

FIG. 20 is a flow chart showing the procedure for creating a plate cylinder for gravure using the original image input section 10a of FIG. In step S11, a pin hole is formed in the color separation image of each plate. In step S12, the color separation image of the first version is attached to the original image input unit 10a. In step S13, the engraving image signal is directly read from the color-separated image, and halftone dot cells are engraved on the surface of the plate cylinder in step S14 according to the engraving image signal. Then, when creating the next plate cylinder, the process returns from step S15 to step S12.

FIG. 21 is a conceptual diagram showing another example of the original image input section capable of accurately positioning the color separated image CS. In each color-separated image CS, a register mark (register mark) RM is drawn at a position whose relative position to the image is exactly the same. The original image input section 10b has a register mark reading device 18 for reading the position of the register mark RM. The register mark reading device 18 is a simple optical device, and an operator views the image of the register mark using the register mark reading device 18, and the color separated image CS is located at a predetermined position (for example, the register mark is aligned with the finder cross of the register mark reading device 18). Position)
It should be adjusted to.

As the register mark reading device 18, a device for reading the image of the register mark using an image pickup device such as a CCD may be used. In this case, the position of the register mark is calculated from the image of the register mark, and the reading start position of the color separated image CS (that is, the engraving start position of the halftone dot cell) is calculated from the calculated position of the register mark.

By accurately positioning the color-separated image of each plate by the above method, the engraving image signal at the position of the halftone dot cell for gravure can be directly read from the color-separated image. When the image signal for engraving is directly read from the color-separated image, the interpolation processing unit 23 in FIG. 1 is unnecessary.

(2) The present invention can be carried out by combining the first embodiment (FIG. 6) and the second embodiment (FIG. 13) to form a halftone dot cell for gravure printing. For example, the halftone dot cell of FIG. 6 is applied to the C plate and the K plate, and the pitch P1x and the pitch P1y of the halftone dot cell are set to 2
13 is applied to the Y plate and the M plate, the pitch P2x of the dot cells is 2Pi, and the pitch P2y is 3Pi. And Y version or M
When the engraving start position of the plate is (X0, Y0), the engraving start position of the C plate or K plate is (X0 + P2x / 4, Y0 +
P2y / 12) is preferable.

[0070]

As described above, according to the first method and apparatus of the present invention, as the halftone dot cell array of at least two color plates, the pitches of the halftone dot cells along the same direction are equal to each other, Since the centers of the halftone dot cells of the at least two color plates are set in the middle of each other, the halftone dot cells of these color plates do not overlap. Therefore, when the halftone dot cells of the gravure are formed, it is possible to reduce the overlapping portion of the halftone dot cells of the plurality of color plates.

According to the second method and apparatus of the present invention,
In addition to the effects of the first method and apparatus, the color separation images are sequentially mounted one by one at the same position of the image reading apparatus and read to generate the engraving image signal for each color plate. There is an effect that the image signal for engraving can be obtained without performing.

According to a third method and apparatus of the present invention,
For each of the magenta, cyan, and black plates, there is no plate in which the pitch of halftone cells along the main scanning direction is equal to each other and the pitch of halftone cells along the sub-scanning direction is equal to each other, and, Since the halftone dot cell array in which the centers of the halftone dot cells of each plate are arranged at positions different from each other is set, the ratio of the overlapping portion of the halftone dot cells does not become excessively large even if the plates are slightly displaced. Therefore, there is an effect that the overlapping portion of the halftone dot cells of a plurality of color plates can be reduced.

In the fourth method and apparatus, in addition to the effects of the third method and apparatus, one image for each color separation is sequentially mounted at the same position of the image reading apparatus and read, thereby engraving the image for each color plate. Since the signal is generated, there is an effect that the image signal for engraving can be obtained without performing the interpolation calculation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electronic engraving system to which an embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram showing an array at the center of pixels of a color separation image signal.

FIG. 3 is a plan view showing an array of halftone dot cells of K plate in the first embodiment.

FIG. 4 is an explanatory diagram in which a center position of a halftone dot cell and a center position of a pixel of a color separation image signal are overlapped and displayed.

FIG. 5 is a plan view showing halftone dot cells of C plate and center positions of pixels in the first embodiment.

FIG. 6 is a plan view showing the arrangement of halftone dot cells of K plate and C plate in the first embodiment.

FIG. 7 is a plan view showing the arrangement of halftone dot cells of K plate and M plate when the image density is 100% in the first embodiment.

FIG. 8 is a plan view showing an arrangement of four-version halftone dot cells in the first embodiment.

FIG. 9 is a flowchart showing a processing procedure in the first embodiment.

FIG. 10 is a flowchart showing a detailed procedure of step S3.

FIG. 11 is a plan view showing the arrangement of halftone dot cells in the second embodiment of the present invention.

FIG. 12 is a plan view showing an array of halftone dot cells of K plate when the image density is 100% in the second embodiment.

FIG. 13 is a plan view showing the arrangement of halftone dot cells of K plate and C plate in the second embodiment.

FIG. 14 is a plan view showing an arrangement of YMCK fourth-version halftone dot cells in a second embodiment.

FIG. 15 is a plan view showing an array of halftone dot cells of M plate and Y plate in the third embodiment.

FIG. 16 is a plan view showing the arrangement of halftone dot cells in the third embodiment.

FIG. 17 is a plan view showing the arrangement of halftone dot cells in the fourth embodiment.

FIG. 18 is a plan view showing a state where the positions of halftone dot cells of M plate are displaced in the fourth embodiment.

FIG. 19 is a conceptual diagram showing an original image input unit for accurately positioning a color separation image.

20 is a flowchart showing a procedure for creating a plate cylinder for gravure using the original image input unit of FIG.

FIG. 21 is a conceptual diagram showing another example of an original image input unit for accurately positioning a color separated image.

[Explanation of symbols]

 10 ... Original image input unit 12 ... Original image cylinder 14 ... Read head 15, 16 ... Positioning pin 18 ... Registration mark reader 20 ... Image processing unit 22 ... Control unit 23 ... Interpolation processing unit 24 ... Color monitor 26 ... External storage device 28 ... Mouse 30 ... Engraving part 32 ... Plate body member 34 ... Engraving blade CC ... C plate halftone cell CS ... Color separation image KC ... K plate halftone cell MC ... M plate halftone cell OR ... Original image Pxk ... K plate Main scanning direction pitch of halftone dot cell Pyk ... Sub scanning direction pitch of K plate half dot cell Pi ... Pixel pitch Px ... Main scanning direction pitch of halftone dot cell Py ... Sub scanning direction pitch of halftone dot cell RM ... Registration mark X ... Main scanning direction Y ... Sub scanning direction YC ... Halftone dot cell of Y plate

Claims (8)

[Claims] 1. A method of forming halftone dot cells for gravure printing, comprising engraving halftone dot cells on the surface of a plate cylinder member for gravure printing for each color plate based on a plurality of color separation image signals representing a color image, (A) preparing a plurality of color-separated image signals representing the color-separated image of each color plate at a common coordinate position arranged on the image plane; and (b) interpolating each color-separated image signal with respect to the position of a halftone dot cell. When generating an engraving image signal for each color plate by calculation, the halftone dot cell array of at least two color plates is such that the pitches of the halftone dot cells along the same direction are equal to each other, and the at least two colors Set the halftone dot cell array where the centers of halftone dot cells of the plate are located in the middle of each other,
Generating for each color plate an engraving image signal that defines the size of the halftone dot cell at each halftone dot cell position; and (c) forming halftone dot cells on the plate cylinder member of each color plate based on the engraving image signal. A method of forming a halftone dot cell for gravure printing, comprising a step of engraving. 2. A method of forming halftone dot cells for gravure printing, which comprises engraving halftone cells on the surface of a plate cylinder member for gravure printing, comprising: (a) preparing a plurality of color separation images; and (b) When generating the engraving image signal for each color plate by sequentially mounting and reading the color separation images one by one at the same position of the image reading device, a halftone dot cell array of at least two color plates is formed along the same direction. The pitch of the halftone dot cells is equal to each other, and the halftone dot cell array in which the centers of the halftone dot cells of the at least two color plates are located in the middle of each other is set, and the halftone dot cell at each halftone dot cell position is set. A step of generating an engraving image signal that defines the size of the image, and (c) engraving a halftone cell on the plate cylinder member of each color plate based on the engraving image signal. Forming method. 3. A method of forming halftone dot cells for gravure printing, comprising engraving halftone dot cells on the surface of a plate cylinder member for gravure printing for each color plate based on a plurality of color separation image signals representing a color image. (A) preparing a plurality of color-separated image signals representing the color-separated image of each color plate at a common coordinate position arranged on the image plane; and (b) interpolating each color-separated image signal with respect to the position of a halftone dot cell. When generating the engraving image signal for each color plate by calculation, for each plate of magenta, cyan, and black, the pitch of the halftone dot cells along the main scanning direction is equal to each other and along the sub scanning direction. The pitch of the halftone dot cells is not equal to each other, and the halftone dot cell array in which the centers of the halftone dot cells of each plate are arranged at mutually different positions is set. SE Gravure printing, which comprises: a step of generating an engraving image signal for defining each size for each color plate; and (c) engraving a halftone dot cell on the plate cylinder member of each color plate based on the engraving image signal. Halftone dot cell formation method. 4. A method of forming halftone dot cells for gravure printing, which comprises engraving halftone cells on the surface of a plate cylinder member for gravure printing, comprising: (a) preparing a plurality of color separation images; and (b) When generating the engraving image signal for each color plate by sequentially loading and reading the color separation images one by one at the same position of the image reading device, for the magenta, cyan, and black plates, the main scanning direction The pitches of the halftone dot cells along each other are equal to each other and the pitches of the halftone dot cells along the sub-scanning direction are equal to each other, and there is no plate, and the centers of the halftone dot cells of each plate are arranged at different positions. A step of setting a halftone dot cell array to generate an engraving image signal that defines the size of the halftone dot cell at each halftone dot cell position; and (c) a plate cylinder member of each color plate based on the engraving image signal. Process of engraving halftone dot cells on A method of forming halftone dot cells for gravure printing, comprising: 5. A halftone dot cell forming device for gravure printing, which engraves halftone dot cells on the surface of a plate cylinder member for gravure printing for each color plate based on a plurality of color separation image signals representing a color image, Storage means for storing a plurality of color-separated image signals representing the color-separated image of each color plate at a common coordinate position arranged on the image plane, and each color by interpolating each color-separated image signal with respect to the position of a halftone dot cell. Means for generating an image signal for engraving with respect to a plate, wherein a halftone dot cell array of at least two color plates has equal pitches of the halftone dot cells along the same direction, and the halftone dot mesh of the at least two color plates is provided. By setting a dot cell array in which the centers of dot cells are located in the middle of each other, an engraving image signal that defines the size of the dot cell at each dot cell position is generated for each color plate. A time signal generating means, engraving means and, gravure printing halftone cells forming apparatus comprising engraving a halftone cell on a plate cylinder member of each color plate in accordance with the engraving image signal. 6. A halftone dot cell forming device for gravure printing, which engraves halftone dot cells on the surface of a plate cylinder member for gravure printing using a plurality of color separation images prepared in advance, and is mounted at the same position. Is a means for generating an engraving image signal for each color plate by sequentially reading each of the color-separated images, and the pitch of the halftone cells along the same direction as the halftone cell array of at least two color plates. Are equal to each other and the centers of the halftone dot cells of the at least two color plates are set in the middle of each other, while engraving for defining the size of the halftone dot cells at each halftone dot cell position. A halftone dot cell forming device for gravure printing, comprising: an engraving signal generating unit for reading an image signal for engraving; and an engraving unit for engraving a halftone dot cell on a plate cylinder member of each color plate based on the engraving image signal. 7. A halftone dot cell forming device for gravure printing, which engraves halftone dot cells on the surface of a plate cylinder member for gravure printing for each color plate based on a plurality of color separation image signals representing a color image, Storage means for storing a plurality of color-separated image signals representing the color-separated image of each color plate at a common coordinate position arranged on the image plane, and each color by interpolating each color-separated image signal with respect to the position of a halftone dot cell. Means for generating an engraving image signal for a plate, wherein halftone dot cells having the same pitch in the main scanning direction and halftone dots in the sub scanning direction are provided for each of magenta, cyan, and black plates. There are no plates with the same cell pitch, and the halftone dot cell array in which the centers of the halftone dot cells of each plate are arranged at different positions is set, and the halftone dot cells at each halftone dot cell position are set. And engraving means for engraving a halftone dot cell on the plate cylinder member of each color plate based on the engraving image signal, based on the image signal for engraving. Halftone dot cell forming device for gravure printing. 8. A halftone dot cell forming device for gravure printing, which engraves halftone dot cells on the surface of a plate cylinder member for gravure printing by using a plurality of color separation images prepared in advance, and is mounted at the same position. Is a means for generating an engraving image signal for each color plate by sequentially reading each of the color-separated images that are generated, and is a halftone dot cell along the main scanning direction for each of magenta, cyan, and black plates. Set a halftone dot cell array in which the pitches of the halftone dots are equal to each other and the pitches of halftone dot cells along the sub-scanning direction are not equal to each other, and the centers of the halftone dot cells of each plate are different from each other. Then, engraving signal generating means for reading an engraving image signal that defines the size of the halftone dot cell at each halftone dot cell position, and engraving the halftone dot cell on the plate cylinder member of each color plate based on the engraving image signal. Engraving means , Gravure printing halftone cells forming apparatus comprising a.